2012 Vol. 30, No. 6
Display Method:
Detection of Cyclostratigraphic Sequence Surfaces in Stratigraphic Record:Its principle and approach
2012, 30(6): 991-998.
Abstract:
In this paper spectral analysis methods are used to study sedimentary cycle changes in depth domains in geophysic logging record. We propose that sedimentation rates have important control for cyclic wavelengths, spectrum peak patterns and continuities. Digital simulation tests show cyclic wavelength changes and spectral bands terminations along depth domain by slidingwidow spectral analysis, which indicate abrupt sedimentation rate changes. Its depth location of abrupt surfaces are corresponding to stratigraphic discontinuity and reflect depositional regime conversion and can be as identification critical maker of cyclostratigraphic sequence surface discrimination. This method has been verified to be validity in deep sea sediment from ODP Site 154. The data processing procedures, which sedimentary cycle signals are extracted and check in spectral analysis, are described and illustrated in detailed. The extreme point data series, which are reconstructed from original logs, can be provided us obvious and stable spectral signals with the cyclic wavelength of 10m scale level. The cyclostratigraphic sequence surfaces in this hierarchy can be used a reference surface in regional stratigraphic correlations. The upper Trassic Xujiahe Formation from the western Sichuan foreland basin as a case study, cyclostratigraphic sequence surfaces are calibrated based on evolutive spectral analysis from natural gamma log of Chuanya Hole 95. It is suggested that this methods have widely practical values compression with traditional seismic sequence.
In this paper spectral analysis methods are used to study sedimentary cycle changes in depth domains in geophysic logging record. We propose that sedimentation rates have important control for cyclic wavelengths, spectrum peak patterns and continuities. Digital simulation tests show cyclic wavelength changes and spectral bands terminations along depth domain by slidingwidow spectral analysis, which indicate abrupt sedimentation rate changes. Its depth location of abrupt surfaces are corresponding to stratigraphic discontinuity and reflect depositional regime conversion and can be as identification critical maker of cyclostratigraphic sequence surface discrimination. This method has been verified to be validity in deep sea sediment from ODP Site 154. The data processing procedures, which sedimentary cycle signals are extracted and check in spectral analysis, are described and illustrated in detailed. The extreme point data series, which are reconstructed from original logs, can be provided us obvious and stable spectral signals with the cyclic wavelength of 10m scale level. The cyclostratigraphic sequence surfaces in this hierarchy can be used a reference surface in regional stratigraphic correlations. The upper Trassic Xujiahe Formation from the western Sichuan foreland basin as a case study, cyclostratigraphic sequence surfaces are calibrated based on evolutive spectral analysis from natural gamma log of Chuanya Hole 95. It is suggested that this methods have widely practical values compression with traditional seismic sequence.
2012, 30(6): 999-1009.
Abstract:
This paper takes Zibo, Linqu, Pingyi, Mengyin basin as the key study area. Through composition analysis of fragment garnet in Mesozoic sandstone, we try to discuss the tectonic evolution history of West Shandong uplift and the surroundings in Mesozoic. Research shows that garnet composition of Luxi basin changed from Early Mesozoic Jurassic to Midlate Mesozoic Jurassic implying that the provenace of Luxi basin shifting. The provenance mainly comed from West Shandong uplift in EarlyMid Jurassic period .Then the provenance turn to Jiaodong region and West Shandong uplift in Midlate Mesozoic Jurassic period, but the mainly provenance was Jiaodong region. The changes of provenance of garnet in Jurassic Period showed that Sulu Orogen belt was probably uplifted to the earth's surface in Midlate Jurassic. In Cretaceous period the mainly provenance of Luxi basin was Jiaodong area and Luxi uplift had little contribution in provenance supply, but the provenance supply of Luxi uplift shifted in mid Qingshan Formation and midWangshi Formation . In Cretaceous , Sulu Orogen belt controlled the sediment of Luxi Basin. Paleogeography framework indicates that the terrain of Shangdong is higher in the east and lower in the west. The shifts of garnet provenance in Cretaceous showed that West Shandong uplift was probably uplifted in MidLate period in Early Cretaceous and midlate period in Late Cretaceous.
This paper takes Zibo, Linqu, Pingyi, Mengyin basin as the key study area. Through composition analysis of fragment garnet in Mesozoic sandstone, we try to discuss the tectonic evolution history of West Shandong uplift and the surroundings in Mesozoic. Research shows that garnet composition of Luxi basin changed from Early Mesozoic Jurassic to Midlate Mesozoic Jurassic implying that the provenace of Luxi basin shifting. The provenance mainly comed from West Shandong uplift in EarlyMid Jurassic period .Then the provenance turn to Jiaodong region and West Shandong uplift in Midlate Mesozoic Jurassic period, but the mainly provenance was Jiaodong region. The changes of provenance of garnet in Jurassic Period showed that Sulu Orogen belt was probably uplifted to the earth's surface in Midlate Jurassic. In Cretaceous period the mainly provenance of Luxi basin was Jiaodong area and Luxi uplift had little contribution in provenance supply, but the provenance supply of Luxi uplift shifted in mid Qingshan Formation and midWangshi Formation . In Cretaceous , Sulu Orogen belt controlled the sediment of Luxi Basin. Paleogeography framework indicates that the terrain of Shangdong is higher in the east and lower in the west. The shifts of garnet provenance in Cretaceous showed that West Shandong uplift was probably uplifted in MidLate period in Early Cretaceous and midlate period in Late Cretaceous.
2012, 30(6): 1010-1020.
Abstract:
South Guizhou is located in YunnanGuizhouGuangxi basin, southwest of the Yangtze plate. This area is located in the shallow shelf during the most period of the Permian, dominated by carbonate platform depositional environments. The Moyang Section is just situated in the transitional zone between the carbonate platform and basin, which is an ideal region for preservation of storm deposits. The Maokou Formation of Middle Permian in Moyang Section, Luodian, South Guizhou is mainly composed of marine shelf carbonates. Tempestite occurs in the lower part of this formation, featured by the shell limestone, containing a little rubble with sedimentary structure of storm deposit. Biological shells are severe fragmented and grading is not obvious in the shell limestone. The storm sedimentary structures include bottom erosional surface, truncation, wave ripple bedding, graded bedding, and massive bedding. Storm deposits include bottom erosional surface A and four sedimentary units: B, C, D, E. The unit A, bottom erosional surface, indicates the action of storm flow on marine sediment; the unit B, shell limestone, represents the deposits of storm waves and storm eddy; the unit C, grading layer, records the process of gravitational differentiation or storm turbidity during period of storm decaying; the unit D, massive layer, is produced by rapid accumulation of suspending materials in the late stage of the storm; the top unit E, waves ripple bedding section, is deposited during the later period of the storm. Four successions of storm deposits can be distinguished, correspondent to the waterdepth and storm flow involved. Successions 1, 2 and 3 occur in the inner shelf that between the normal wave base and storm wave base, caused by the intensive proximalstorm. Succession 4 occurs in the outer shelf that below the storm wave base, which is the turbidity deposit brought by the distalstorm. The sedimentary characteristics, types and sequences of the Moyang storm deposit suggest that the preservation of the storm sedimentary sequence closely related to the sedimentary environment, providing a reference for understanding the evolution of the southern margin of the Yangtze carbonate platform.
South Guizhou is located in YunnanGuizhouGuangxi basin, southwest of the Yangtze plate. This area is located in the shallow shelf during the most period of the Permian, dominated by carbonate platform depositional environments. The Moyang Section is just situated in the transitional zone between the carbonate platform and basin, which is an ideal region for preservation of storm deposits. The Maokou Formation of Middle Permian in Moyang Section, Luodian, South Guizhou is mainly composed of marine shelf carbonates. Tempestite occurs in the lower part of this formation, featured by the shell limestone, containing a little rubble with sedimentary structure of storm deposit. Biological shells are severe fragmented and grading is not obvious in the shell limestone. The storm sedimentary structures include bottom erosional surface, truncation, wave ripple bedding, graded bedding, and massive bedding. Storm deposits include bottom erosional surface A and four sedimentary units: B, C, D, E. The unit A, bottom erosional surface, indicates the action of storm flow on marine sediment; the unit B, shell limestone, represents the deposits of storm waves and storm eddy; the unit C, grading layer, records the process of gravitational differentiation or storm turbidity during period of storm decaying; the unit D, massive layer, is produced by rapid accumulation of suspending materials in the late stage of the storm; the top unit E, waves ripple bedding section, is deposited during the later period of the storm. Four successions of storm deposits can be distinguished, correspondent to the waterdepth and storm flow involved. Successions 1, 2 and 3 occur in the inner shelf that between the normal wave base and storm wave base, caused by the intensive proximalstorm. Succession 4 occurs in the outer shelf that below the storm wave base, which is the turbidity deposit brought by the distalstorm. The sedimentary characteristics, types and sequences of the Moyang storm deposit suggest that the preservation of the storm sedimentary sequence closely related to the sedimentary environment, providing a reference for understanding the evolution of the southern margin of the Yangtze carbonate platform.
2012, 30(6): 1021-1031.
Abstract:
The well known geological mountainMantoushan is located in the mountain area of southern Jinan city. The standard (stratotype) profile from the Longwangmiao Stage to the Zhangxia Stage of the Lower middle Cambrian of the North China is established here. Here, geological traces are so rich and research history is so long that Mantoushan mount is famous at home and abroad. The Jinan area lies in the west side of the Tanlu fault and seismic zone. During the early Cambrian, a set of terrigenous clastic sediments consisted of sand and mud intercalated with carbonate were deposited in the western Shandong region including Jinan city where was littoral, sabkha and epicontinental sea, which stratigraphic sequence, from bottom to top, was the Liguan Formation (∈1l), the Zhushadong Formation((∈1l) and the Mantou Formation(∈1-2m). By means of field observation and labexammination, various synsedimentary deformation structures caused by earthquakes, namely seismites, were identified in the Lower Cambrian of Mantoushan mount, eastern hill to the Qingyang village, Hongyegu valley and Gunqiushan mount, and so on. The synsedimentary deformation structures discovered by the study include convolute deformation (seismic fold), graded microfault, gliding structure, slump fold, load structure, pillow mass, mixed insertion sediment, soft siliceous vein, diapir structures of soft siliceous layers, deformation of diatoms stramatolitic, settlement structure, thixotropic wedge, boudinage, seismic crack or fissure, shattered breccia and seismic breccia, and so on. Most of them belong to plastic deformation structures of softsediments, but shattered breccia, seismic breccia and seismic crack or fissure are brittle deformation structures of semiconsolidated to uncompletely consolidated sediments. Their characteristics and formation mechanism are detailed in this paper. The thixotropic wedge has been reported firstly in China. Some thixotropic wedge and settlement structures developed in dolomite with siliceous layers, and their original sediment was dolomitic limemud with soft siliceous layers. By triggering of strong earthquake, soft siliceous layers became more soft because viscosity of siliceous sediment (SiO2·nH2O) get diminished, meanwhile dolomitic limemud was liquefied. Under vertical shock force, soft siliceous layers were cut off, and subsequently sinkage of disconnected siliceous layers formed settlement structure, which extended down so that disconnected siliceous layers converged to result in the formation of thixotropic wedge. Differences of thixotropic wedge, seismic crack and filling structure of seismic crack are as follows: (1) Thixotropic wedge are one of plastic deformations which are formed for viscosity of soft nonliquefied sediments is diminished and their rheological property is enhanced (thixotropy) by earthquake triggering. With settlement structure going on to deep, thixotropic wedge was formed. Formations of wedge body and it's host rock are synchronous; (2) Seismic crack is a tensile fissure of the "V" shape，which belongs to brittle deformation of semiconsolidated or incompletely consolidated sediment formed by the earthquake action; (3)The filling structure of seismic crack is usually wedge yet, but its filling is soft sediment or brittle seismic breccia. In general, the formation process of wedge body is out of synch with that of the crack. On the basis of the distribution of palaeotectonic plates and seismic zones in the early Cambrian, it is considered that these seismic sedimentary traces are records of the intraplate ancient earthquakes during the early Cambrian, and it is can be deduced that they are response to tectonic activities of the PaleoTanlu fault zone. The discovery of paleoseismic event records and the interpretation of this paper enrich the geological sciences connotation of the southern Jinan area, especially the Mantoushan mount.
The well known geological mountainMantoushan is located in the mountain area of southern Jinan city. The standard (stratotype) profile from the Longwangmiao Stage to the Zhangxia Stage of the Lower middle Cambrian of the North China is established here. Here, geological traces are so rich and research history is so long that Mantoushan mount is famous at home and abroad. The Jinan area lies in the west side of the Tanlu fault and seismic zone. During the early Cambrian, a set of terrigenous clastic sediments consisted of sand and mud intercalated with carbonate were deposited in the western Shandong region including Jinan city where was littoral, sabkha and epicontinental sea, which stratigraphic sequence, from bottom to top, was the Liguan Formation (∈1l), the Zhushadong Formation((∈1l) and the Mantou Formation(∈1-2m). By means of field observation and labexammination, various synsedimentary deformation structures caused by earthquakes, namely seismites, were identified in the Lower Cambrian of Mantoushan mount, eastern hill to the Qingyang village, Hongyegu valley and Gunqiushan mount, and so on. The synsedimentary deformation structures discovered by the study include convolute deformation (seismic fold), graded microfault, gliding structure, slump fold, load structure, pillow mass, mixed insertion sediment, soft siliceous vein, diapir structures of soft siliceous layers, deformation of diatoms stramatolitic, settlement structure, thixotropic wedge, boudinage, seismic crack or fissure, shattered breccia and seismic breccia, and so on. Most of them belong to plastic deformation structures of softsediments, but shattered breccia, seismic breccia and seismic crack or fissure are brittle deformation structures of semiconsolidated to uncompletely consolidated sediments. Their characteristics and formation mechanism are detailed in this paper. The thixotropic wedge has been reported firstly in China. Some thixotropic wedge and settlement structures developed in dolomite with siliceous layers, and their original sediment was dolomitic limemud with soft siliceous layers. By triggering of strong earthquake, soft siliceous layers became more soft because viscosity of siliceous sediment (SiO2·nH2O) get diminished, meanwhile dolomitic limemud was liquefied. Under vertical shock force, soft siliceous layers were cut off, and subsequently sinkage of disconnected siliceous layers formed settlement structure, which extended down so that disconnected siliceous layers converged to result in the formation of thixotropic wedge. Differences of thixotropic wedge, seismic crack and filling structure of seismic crack are as follows: (1) Thixotropic wedge are one of plastic deformations which are formed for viscosity of soft nonliquefied sediments is diminished and their rheological property is enhanced (thixotropy) by earthquake triggering. With settlement structure going on to deep, thixotropic wedge was formed. Formations of wedge body and it's host rock are synchronous; (2) Seismic crack is a tensile fissure of the "V" shape，which belongs to brittle deformation of semiconsolidated or incompletely consolidated sediment formed by the earthquake action; (3)The filling structure of seismic crack is usually wedge yet, but its filling is soft sediment or brittle seismic breccia. In general, the formation process of wedge body is out of synch with that of the crack. On the basis of the distribution of palaeotectonic plates and seismic zones in the early Cambrian, it is considered that these seismic sedimentary traces are records of the intraplate ancient earthquakes during the early Cambrian, and it is can be deduced that they are response to tectonic activities of the PaleoTanlu fault zone. The discovery of paleoseismic event records and the interpretation of this paper enrich the geological sciences connotation of the southern Jinan area, especially the Mantoushan mount.
2012, 30(6): 1032-1041.
Abstract:
Autochthonous seismites of the Doushantuo Formation have been discovered for the first time in Xikou, Cili County in Hunan Province. Based on the profile measurement, detailed observations and description, combined with the analysis of the tectonic background, many typical seismites soft sedimentary deformation structures have been recognized, such as: faultgraded, liquefied carbonate vein, liquefied breccias, convolute deformation structure, waterescape structur and seismofolds, and so on. The vertical sequence of the seimites is underlying unshocked layer, synsedimentary microtracture (faultgraded), microcorrugated layer, vibrational liquefaction layer, liquefied breccias layer, liquefied homogenization layer and overlying unshocked layer from down to up. The horizon of the seismite shows a good contradistinctive relation in time and space. It suggests that in the Doushantuo Period, strong and frequency seismic activity occurred in study area, the nature and activity of earthquake fault varied with different phases. Tectonic activity which accelerates the organic carbon the oxidation is beneficial to development of organisms and also helpful to the phosphate accumulation. In addition, wellkept paleoseismic records are of great significance to deduce the sedimentary environment.
Autochthonous seismites of the Doushantuo Formation have been discovered for the first time in Xikou, Cili County in Hunan Province. Based on the profile measurement, detailed observations and description, combined with the analysis of the tectonic background, many typical seismites soft sedimentary deformation structures have been recognized, such as: faultgraded, liquefied carbonate vein, liquefied breccias, convolute deformation structure, waterescape structur and seismofolds, and so on. The vertical sequence of the seimites is underlying unshocked layer, synsedimentary microtracture (faultgraded), microcorrugated layer, vibrational liquefaction layer, liquefied breccias layer, liquefied homogenization layer and overlying unshocked layer from down to up. The horizon of the seismite shows a good contradistinctive relation in time and space. It suggests that in the Doushantuo Period, strong and frequency seismic activity occurred in study area, the nature and activity of earthquake fault varied with different phases. Tectonic activity which accelerates the organic carbon the oxidation is beneficial to development of organisms and also helpful to the phosphate accumulation. In addition, wellkept paleoseismic records are of great significance to deduce the sedimentary environment.
2012, 30(6): 1042-1052.
Abstract:
According to the analysis for cores, seismic interpretation and welllogging , the authors have thoroughly studied the sedimentary facies types and characters of Yanchang Formation of the Upper Triassic in the south Ordos Basin with thin sections and grain size analysis and a great deal of indoor testing data. The authors have proposed that the sedimentary facies type of Chang 9 to Chang 6 of Yanchang Formation is sandy debris flows. With basin sedimentary and evolutionary background, the genetic mechanism of the sand debris flows have been discussed, and detailed studies have been made on the rock types and sedimentary structures of the sandy debris flows, build up relevant sedimentary models. The results indicate that the sandy debris flows deposit is composed of two genetic facies of massivebedded siltsand and packsand and mud pebble siltsand and packsand, which indicate deposition from deltafront sand during slip and slump under outside function of energy.Relationship between sandy debris flow depositional systems and distribution of oil and gas are elaborated in detail. It is considered that sandy debris flow deposits are injection migration oilgas accumulation types and classic lithologic hydrocarbon reservoir, which are the most favorable sedimentary facies belt for the generation of Yanchang Formation reservoirs.
According to the analysis for cores, seismic interpretation and welllogging , the authors have thoroughly studied the sedimentary facies types and characters of Yanchang Formation of the Upper Triassic in the south Ordos Basin with thin sections and grain size analysis and a great deal of indoor testing data. The authors have proposed that the sedimentary facies type of Chang 9 to Chang 6 of Yanchang Formation is sandy debris flows. With basin sedimentary and evolutionary background, the genetic mechanism of the sand debris flows have been discussed, and detailed studies have been made on the rock types and sedimentary structures of the sandy debris flows, build up relevant sedimentary models. The results indicate that the sandy debris flows deposit is composed of two genetic facies of massivebedded siltsand and packsand and mud pebble siltsand and packsand, which indicate deposition from deltafront sand during slip and slump under outside function of energy.Relationship between sandy debris flow depositional systems and distribution of oil and gas are elaborated in detail. It is considered that sandy debris flow deposits are injection migration oilgas accumulation types and classic lithologic hydrocarbon reservoir, which are the most favorable sedimentary facies belt for the generation of Yanchang Formation reservoirs.
2012, 30(6): 1053-1060.
Abstract:
Shallowwater delta in large lacustrine depression basins is different from conventional delta in aspects of framework, microfacies, sandbody, scale and shape. In this article, forming conditions and deposition characteristics of K2y1 shallowwater deltas in the southern Songliao basin has been analyzed. Songliao basin are characterized by stable structure, slow subsidence, flat palaeotopography, dry climate and sufficient material source during Putaohua Formation, thus formed a distinctive shallowwater delta deposition. Unlike conventional terrigenous basins, its shoreline often migrated in large scale and few deep lacustrine and semideep lacustrine facies developed . The shallowwater delta can be distinguished by following characteristics:(1)The channel of shallowwater delta extended far away, up to 160 km from delta plain to lake center; Divaricating and confluence were often happen in delta . Sand bodies show obvious direction and birds footlike distribution on the isopach map.(2)Mouth bar in the front of delta was not developed as restricted by accommodation and washing action. The sandstone reservoirs were obviously controlled by fluvial system.(3)Channel on the delta front were reformed to sheetlike sandstone by lake water and can be divided into three styles which include poorly sheetlike, moderately sheetlike and intensely sheetlike styles;(4)The sedimentary models of shallowwater delta differ from Gilbert delta style which have topset bed, bottomset bed and foreset bed. During K2y1 deposition period, the base level increased gradually, I and II sand group provided a favorable reservoir storage space, III sand group transgress provided a good seal for Putaohua reservoir.
Shallowwater delta in large lacustrine depression basins is different from conventional delta in aspects of framework, microfacies, sandbody, scale and shape. In this article, forming conditions and deposition characteristics of K2y1 shallowwater deltas in the southern Songliao basin has been analyzed. Songliao basin are characterized by stable structure, slow subsidence, flat palaeotopography, dry climate and sufficient material source during Putaohua Formation, thus formed a distinctive shallowwater delta deposition. Unlike conventional terrigenous basins, its shoreline often migrated in large scale and few deep lacustrine and semideep lacustrine facies developed . The shallowwater delta can be distinguished by following characteristics:(1)The channel of shallowwater delta extended far away, up to 160 km from delta plain to lake center; Divaricating and confluence were often happen in delta . Sand bodies show obvious direction and birds footlike distribution on the isopach map.(2)Mouth bar in the front of delta was not developed as restricted by accommodation and washing action. The sandstone reservoirs were obviously controlled by fluvial system.(3)Channel on the delta front were reformed to sheetlike sandstone by lake water and can be divided into three styles which include poorly sheetlike, moderately sheetlike and intensely sheetlike styles;(4)The sedimentary models of shallowwater delta differ from Gilbert delta style which have topset bed, bottomset bed and foreset bed. During K2y1 deposition period, the base level increased gradually, I and II sand group provided a favorable reservoir storage space, III sand group transgress provided a good seal for Putaohua reservoir.
2012, 30(6): 1061-1071.
Abstract:
Trace elements and REE of sedimentary rocks contain abundant information of geology. Having a high sensitivity on hydrological changes of sedimentary environment, trace elements and REE can be used as an effective method on the study of paleoclimate and paleoenvironment during deposition period. Choosing the trace elements and REE measured value of 17 samples of middle Jurassic Shaximiao Formation of western margin of Sichuan basin. Results indicate that, in the study area, both the Sr/Ba ratios of the upper and lower Shaximiao Formation are less than 1, which illustrate that there was a fresh water environment during deposition of Shaximiao Formation. The characteristic values and ratios of trace elements and REE such as V,U,Mo,V/Cr,Ni/Co,U/Th,（Cu+Mo）/Zn,V/（V+Ni）,δCe,δEu,∑REE,La/Yb, suggest that the bottom water of the lake was moderate oxidation environment during the whole time Shaximiao Formation deposition. According to the Sr/Cu ratios and the research findings before, we suggest that there paleaoclimate was warm and arid with cool interphases during the whole time of lower Shaximiao Formation， and after then it turned to worm and aridity again during the upper Shaximiao period， which is as the lower Shaximiao Formation, and the aridity strengthened gradually.
Trace elements and REE of sedimentary rocks contain abundant information of geology. Having a high sensitivity on hydrological changes of sedimentary environment, trace elements and REE can be used as an effective method on the study of paleoclimate and paleoenvironment during deposition period. Choosing the trace elements and REE measured value of 17 samples of middle Jurassic Shaximiao Formation of western margin of Sichuan basin. Results indicate that, in the study area, both the Sr/Ba ratios of the upper and lower Shaximiao Formation are less than 1, which illustrate that there was a fresh water environment during deposition of Shaximiao Formation. The characteristic values and ratios of trace elements and REE such as V,U,Mo,V/Cr,Ni/Co,U/Th,（Cu+Mo）/Zn,V/（V+Ni）,δCe,δEu,∑REE,La/Yb, suggest that the bottom water of the lake was moderate oxidation environment during the whole time Shaximiao Formation deposition. According to the Sr/Cu ratios and the research findings before, we suggest that there paleaoclimate was warm and arid with cool interphases during the whole time of lower Shaximiao Formation， and after then it turned to worm and aridity again during the upper Shaximiao period， which is as the lower Shaximiao Formation, and the aridity strengthened gradually.
2012, 30(6): 1072-1079.
Abstract:
Lake Qinghai, the largest closedbasin brackish lake in China, is located in the northeastern margin of Tibetan Plateau. The authors studied a 475 cm long sediment core (QH2005) retrieved from the southeastern part of Lake Qinghai. The six chronological constraints for core QH2005 include: four 14C dates on bulk organic carbon (BOC) and two on lignin. The inferred changing "lake reservoir effect" was used to correct the older BOC dates. The corrected BOC dates, together with the lignin dates were converted into calendar ages to yield the "depthage" model for core QH2005. We randomly collected adult ostracod (Limnocythere inopinata or Eucypris inflata) valves from the sediment and measured the body length for 30 L. inopinata valves, which were later statistically processed to yield its average value. For sections without enough L. inopinata valves in core QH2005, E. inflata valves were used to instead. In addition, sediment redness was also determined for Core QH2005. Ostracod δ18O values for Core QH2005 were revealed to be mainly related to dilution and evaporative enrichment of the lake water and hence can be further used to indicate enhanced monsoonal precipitation of Lake Qinghai area when negative ostracod δ18O values were observed. High redness values indicate increased riverine supply to Lake Qinghai associated with increased monsoon rainfall. The results of ostracod δ18O and redness show that: climate during 13,500~10,900 cal a BP was relatively cold and dry with frequent shortterm fluctuations; warm and wet climate began at about 10 900 cal a BP and culminated around 6 500 cal a BP as a result of monsoon strengthening; climate became cold and dry afterwards and has remained relatively stable since 3 400 cal a BP. The reconstructed salinity based on ostracod body length coincides well with the above changing pattern. Generally, the reconstructed lake water salinity shows evident decreasing trend with considerable fluctuations in late glacial, synchronous to the amelioration of monsoon climate; the salinity displays overall increasing trend since late Holocene, coinciding with the deduced deterioration of monsoon climate. However, on millennial/centennial timescales, the paleosalinity based on ostrocad body length is not in accord with the shortterm climatic fluctuations (including: icerafting events 4, 3 and 2 (by ~5 900 cal a BP, ~4 300 cal a BP and ~3 100 cal a BP respectively) and Little Ice Age (by ~500 cal a BP)) deduced by ostracod δ18O and redness results. We speculate that lake water salinity was one of the most important factors influencing the L. inopinata body length, but not necessarily the only one factor. Other factors including water temperature, water depth and water chemical composition could as well exert certain influences on the microhabitat of ostracod and hereby in turn give rise to changes in ostracod body length. Therefore more studies are needed to make clear the mechanism of environmental factors influencing ostracod body length before it can be used to reconstruct environmental variables.
Lake Qinghai, the largest closedbasin brackish lake in China, is located in the northeastern margin of Tibetan Plateau. The authors studied a 475 cm long sediment core (QH2005) retrieved from the southeastern part of Lake Qinghai. The six chronological constraints for core QH2005 include: four 14C dates on bulk organic carbon (BOC) and two on lignin. The inferred changing "lake reservoir effect" was used to correct the older BOC dates. The corrected BOC dates, together with the lignin dates were converted into calendar ages to yield the "depthage" model for core QH2005. We randomly collected adult ostracod (Limnocythere inopinata or Eucypris inflata) valves from the sediment and measured the body length for 30 L. inopinata valves, which were later statistically processed to yield its average value. For sections without enough L. inopinata valves in core QH2005, E. inflata valves were used to instead. In addition, sediment redness was also determined for Core QH2005. Ostracod δ18O values for Core QH2005 were revealed to be mainly related to dilution and evaporative enrichment of the lake water and hence can be further used to indicate enhanced monsoonal precipitation of Lake Qinghai area when negative ostracod δ18O values were observed. High redness values indicate increased riverine supply to Lake Qinghai associated with increased monsoon rainfall. The results of ostracod δ18O and redness show that: climate during 13,500~10,900 cal a BP was relatively cold and dry with frequent shortterm fluctuations; warm and wet climate began at about 10 900 cal a BP and culminated around 6 500 cal a BP as a result of monsoon strengthening; climate became cold and dry afterwards and has remained relatively stable since 3 400 cal a BP. The reconstructed salinity based on ostracod body length coincides well with the above changing pattern. Generally, the reconstructed lake water salinity shows evident decreasing trend with considerable fluctuations in late glacial, synchronous to the amelioration of monsoon climate; the salinity displays overall increasing trend since late Holocene, coinciding with the deduced deterioration of monsoon climate. However, on millennial/centennial timescales, the paleosalinity based on ostrocad body length is not in accord with the shortterm climatic fluctuations (including: icerafting events 4, 3 and 2 (by ~5 900 cal a BP, ~4 300 cal a BP and ~3 100 cal a BP respectively) and Little Ice Age (by ~500 cal a BP)) deduced by ostracod δ18O and redness results. We speculate that lake water salinity was one of the most important factors influencing the L. inopinata body length, but not necessarily the only one factor. Other factors including water temperature, water depth and water chemical composition could as well exert certain influences on the microhabitat of ostracod and hereby in turn give rise to changes in ostracod body length. Therefore more studies are needed to make clear the mechanism of environmental factors influencing ostracod body length before it can be used to reconstruct environmental variables.
2012, 30(6): 1080-1087.
Abstract:
The surface calcification is a kind of deposit on the earth, which is an important deposit type of land calcium carbonate. For a long time, the hydrodynamic formation cause of land calcium carbonate deposit is familiar to the researchers. The research of the biological cause of the formation is relatively fewer. In fact, the biological cause should be not ignored as well, especially algous deposit process. From imitating for field hydrodynamic force condition, taking the bluegreen algae for example, the research makes a biological deposit test under the different hydrodynamic force condition. From the test, we get optimum hydrodynamic condition of algae growth and their calcification rate, that is under the rate of 0~60 rpm, under the excessive strong , the growth of bluegreen algae will be restrained, and reduce the deposit rate of calcium carbonate. Under the condition of waterfall, hydrodynamic force is strong, in calcium carbonate depositing process, hydrodynamic formation cause of land calcium carbonate deposit is the lead cause; Under the weaker hydrodynamic condition, such as in river bed, biological calcification deposit will be the lead cause. Therefore, hydrodynamicbiological cause viewpoint has been proposed in the article. From the field algous samples, the calcium carbonate depositing test has been done under the different water hydrodynamic conditions. The test results show that under the faster water condition, most calcium carbonate will deposit very quick，and fewer algae calcium carbonate will precipitate because of adverse living environment under the condition. And under the slower water condition, because of being avail for algae’s living, more algae calcium carbonate will precipitate, and few calcium carbonate will deposit under the condition without algae. Also, under the motionless condition, contribution of calcium carbonate deposit have been compared in the article between the algous environment and without algous environment. The article presents , while without algous, under the motionless condition, the calcium carbonate depositing is controlled by liquid equilibrium state, over saturation liquor will keep the deposition going, unless the liquor is saturated. But, while algous join, under the motionless condition, the calcium carbonate depositing may not be controlled by liquid equilibrium state, algous calcium carbonate deposit will keep going，even if it is saturated. So, under the faster flow condition, without doubt, fast flow makes CO2 in liquor overflow，calcium carbonate will deposit in quantity，while the contribute from algous calcium carbonate deposit is few. Under the motionless condition,Mechanism of CO2 overflowing almost disappear, or weak, corresponding calcium carbonate deposit is few, and algous calcium carbonate deposit is main. Then, in nature, largely stromatolite may indicate a quiet deposit environment.
The surface calcification is a kind of deposit on the earth, which is an important deposit type of land calcium carbonate. For a long time, the hydrodynamic formation cause of land calcium carbonate deposit is familiar to the researchers. The research of the biological cause of the formation is relatively fewer. In fact, the biological cause should be not ignored as well, especially algous deposit process. From imitating for field hydrodynamic force condition, taking the bluegreen algae for example, the research makes a biological deposit test under the different hydrodynamic force condition. From the test, we get optimum hydrodynamic condition of algae growth and their calcification rate, that is under the rate of 0~60 rpm, under the excessive strong , the growth of bluegreen algae will be restrained, and reduce the deposit rate of calcium carbonate. Under the condition of waterfall, hydrodynamic force is strong, in calcium carbonate depositing process, hydrodynamic formation cause of land calcium carbonate deposit is the lead cause; Under the weaker hydrodynamic condition, such as in river bed, biological calcification deposit will be the lead cause. Therefore, hydrodynamicbiological cause viewpoint has been proposed in the article. From the field algous samples, the calcium carbonate depositing test has been done under the different water hydrodynamic conditions. The test results show that under the faster water condition, most calcium carbonate will deposit very quick，and fewer algae calcium carbonate will precipitate because of adverse living environment under the condition. And under the slower water condition, because of being avail for algae’s living, more algae calcium carbonate will precipitate, and few calcium carbonate will deposit under the condition without algae. Also, under the motionless condition, contribution of calcium carbonate deposit have been compared in the article between the algous environment and without algous environment. The article presents , while without algous, under the motionless condition, the calcium carbonate depositing is controlled by liquid equilibrium state, over saturation liquor will keep the deposition going, unless the liquor is saturated. But, while algous join, under the motionless condition, the calcium carbonate depositing may not be controlled by liquid equilibrium state, algous calcium carbonate deposit will keep going，even if it is saturated. So, under the faster flow condition, without doubt, fast flow makes CO2 in liquor overflow，calcium carbonate will deposit in quantity，while the contribute from algous calcium carbonate deposit is few. Under the motionless condition,Mechanism of CO2 overflowing almost disappear, or weak, corresponding calcium carbonate deposit is few, and algous calcium carbonate deposit is main. Then, in nature, largely stromatolite may indicate a quiet deposit environment.
2012, 30(6): 1088-1098.
Abstract:
Coastal saltmarshes are among the most productive ecosystems in the world, and scientific evaluations of their potentials as carbon sources or sinks have great significances for the studies on carbon exchanges between land and the sea. Sulfate reduction is the most important process for degradation of soil organic matters of saltmarshes, and the main functional microbes in this process are sulfatereducing bacteria. Two transects from hight tidal flat to bare flat were selected from areas with Spartina alterniflora and native vegetation, respectively, for investigations of spatial distribution characteristics and mechanism of sulfatereducing bacteria (SRB) in the Chongmingdongtan saltmarsh of the Yangtze Estuary. This study was based on data including concentrations of both SRB and heterotrophic bacteria (HB) in soil samples with different depths and plant rhizospheres, content and δ13C value of particulate organic carbon (POC), and molar ratio of Cl/SO2-4 of interstitial water in drilling cores with different altitudes in the saltmarsh. SRB concentrations of the cores increase from the high tidal flat to the bare flat, due to decrease of oxygen content and increase of SO2-4 content of the cores from land to the sea. This suggests that SRB turn to be more important in mineralization of organic matters from the high tidal flat to the bare flat. The variation trend of SRB concentration from the high tidal flat to the bare flat, however, has not been influenced markedly by POC content of the soils. The concentrations of HB in samples with different depths of the drilling core from high tidal flat are markedly greater than those of HB in samples with corresponding depths of the drilling cores from both middle tidal flat and bare flat. This is due to the decreases in both oxygen content and POC content of the cores from land to the sea. Different cores are similar in that the concentrations of HB decrease with depth due to the decrease of soil oxygen content with depth. The concentration of HB in the area with higher POC content is markedly greater that that of HB in the area with lower POC content. The concentrations of SRB are markedly different in rhizospheres of different types of vegetations. SRB is susceptible to rhizospheres of different types of vegetations. Rehizosphere of Phraqmites australis is the most favorable one for SRB growth, and that of Scirpus triqueter comes next. Rehizosphere of Spartina alterniflora is unfavorable to SRB growth, and the root secretion may restrain the development of SRB. The concentration of HB in the rhizosphere soil is greater than that of HB in nonrhizosphere soil, and HB is not susceptible to the rhizospheres of different types of vegetations. Soil organic matter content is the key factor that result in the difference in microbe amount between the drilling cores with the same altitudes from different transects. The difference in microbe amount between drilling cores with different altitudes in one transect, is due to the differences in both soil oxygen content and SO2-4 content between the cores. SRB is susceptible to the organic components originating from Spartina alterniflora, and the organic matters with much components coming from Spartina alterniflora may restrain the growth of SRB. Mineralizations of the organic components originating from Spartina alterniflora probably attribute to HB. The molar ratio of Cl/SO2-4 of interstitial water is low, and is less than 19.33 in most cases, indicating additon of SO2-4 with sources other than the sea. Such additions of SO2-4 offset the consumption of SO2-4 due to sulfate reduction, and make it more difficult to determine quantitatively the intensity of sulfate reduction based on the molar ratio of Cl/SO2-4 of interstitial water in the salt marsh. The more SRB there exists, the greater the molar ratio of Cl/SO2-4 is, and the more marked sulfate reduction is in one drilling core.
Coastal saltmarshes are among the most productive ecosystems in the world, and scientific evaluations of their potentials as carbon sources or sinks have great significances for the studies on carbon exchanges between land and the sea. Sulfate reduction is the most important process for degradation of soil organic matters of saltmarshes, and the main functional microbes in this process are sulfatereducing bacteria. Two transects from hight tidal flat to bare flat were selected from areas with Spartina alterniflora and native vegetation, respectively, for investigations of spatial distribution characteristics and mechanism of sulfatereducing bacteria (SRB) in the Chongmingdongtan saltmarsh of the Yangtze Estuary. This study was based on data including concentrations of both SRB and heterotrophic bacteria (HB) in soil samples with different depths and plant rhizospheres, content and δ13C value of particulate organic carbon (POC), and molar ratio of Cl/SO2-4 of interstitial water in drilling cores with different altitudes in the saltmarsh. SRB concentrations of the cores increase from the high tidal flat to the bare flat, due to decrease of oxygen content and increase of SO2-4 content of the cores from land to the sea. This suggests that SRB turn to be more important in mineralization of organic matters from the high tidal flat to the bare flat. The variation trend of SRB concentration from the high tidal flat to the bare flat, however, has not been influenced markedly by POC content of the soils. The concentrations of HB in samples with different depths of the drilling core from high tidal flat are markedly greater than those of HB in samples with corresponding depths of the drilling cores from both middle tidal flat and bare flat. This is due to the decreases in both oxygen content and POC content of the cores from land to the sea. Different cores are similar in that the concentrations of HB decrease with depth due to the decrease of soil oxygen content with depth. The concentration of HB in the area with higher POC content is markedly greater that that of HB in the area with lower POC content. The concentrations of SRB are markedly different in rhizospheres of different types of vegetations. SRB is susceptible to rhizospheres of different types of vegetations. Rehizosphere of Phraqmites australis is the most favorable one for SRB growth, and that of Scirpus triqueter comes next. Rehizosphere of Spartina alterniflora is unfavorable to SRB growth, and the root secretion may restrain the development of SRB. The concentration of HB in the rhizosphere soil is greater than that of HB in nonrhizosphere soil, and HB is not susceptible to the rhizospheres of different types of vegetations. Soil organic matter content is the key factor that result in the difference in microbe amount between the drilling cores with the same altitudes from different transects. The difference in microbe amount between drilling cores with different altitudes in one transect, is due to the differences in both soil oxygen content and SO2-4 content between the cores. SRB is susceptible to the organic components originating from Spartina alterniflora, and the organic matters with much components coming from Spartina alterniflora may restrain the growth of SRB. Mineralizations of the organic components originating from Spartina alterniflora probably attribute to HB. The molar ratio of Cl/SO2-4 of interstitial water is low, and is less than 19.33 in most cases, indicating additon of SO2-4 with sources other than the sea. Such additions of SO2-4 offset the consumption of SO2-4 due to sulfate reduction, and make it more difficult to determine quantitatively the intensity of sulfate reduction based on the molar ratio of Cl/SO2-4 of interstitial water in the salt marsh. The more SRB there exists, the greater the molar ratio of Cl/SO2-4 is, and the more marked sulfate reduction is in one drilling core.
2012, 30(6): 1099-1105.
Abstract:
It is necessary to know longterm flood records and the sequence for understanding the features and periods of extreme flood, while lacustrine sediments from Taihu Lake has provided the records much longer than the observations. This paper has reconstructed historical flood events during the past 150 years in Taihu Lake catchment, by sedimentary records from TXS core in the centre of the open water. Dating of the 210Pb and 137Cs and characteristics of the grain size and magnetic susceptibility were analyzed, and sedimentary flood index were configureated which have been correlated with regional summer precipitation and flood discharge in the lower reaches of the Yangtze River. Results showed that there were about 24 events of the extreme large floods when we used cutoff the 90th percentiges for the discharge (Q≥90th%) and summer precipitation (Pjja≥90th%) from historical documents since 1840AD. Compariably, flood index from grain size of sedimentary sand (>64 μm) and lowfrequency magnetic susceptibility can catch 15 flood events during the past 150 years, 62.5% corespending with the historical records. This result supported that lacustrine sediment records can well reconstruct the paleoflood change, and provid scientific basis of sedimentology and magnetic susceptibility to recognize centenary timescale extreme floods in features and periods.
It is necessary to know longterm flood records and the sequence for understanding the features and periods of extreme flood, while lacustrine sediments from Taihu Lake has provided the records much longer than the observations. This paper has reconstructed historical flood events during the past 150 years in Taihu Lake catchment, by sedimentary records from TXS core in the centre of the open water. Dating of the 210Pb and 137Cs and characteristics of the grain size and magnetic susceptibility were analyzed, and sedimentary flood index were configureated which have been correlated with regional summer precipitation and flood discharge in the lower reaches of the Yangtze River. Results showed that there were about 24 events of the extreme large floods when we used cutoff the 90th percentiges for the discharge (Q≥90th%) and summer precipitation (Pjja≥90th%) from historical documents since 1840AD. Compariably, flood index from grain size of sedimentary sand (>64 μm) and lowfrequency magnetic susceptibility can catch 15 flood events during the past 150 years, 62.5% corespending with the historical records. This result supported that lacustrine sediment records can well reconstruct the paleoflood change, and provid scientific basis of sedimentology and magnetic susceptibility to recognize centenary timescale extreme floods in features and periods.
2012, 30(6): 1106-1114.
Abstract:
Welldeveloped Neocene strata in the western Qaidam Basin were a detailed record of the deformation and uplift of the surrounding mountain, weathering and erosion of the provenance and the process of climate changes. Based on the measurement and analysis of the carbonate contents, chloride ion contents and sulfate radical contents of the Miocene sediment in the Honggouzi section of the western Qaidam Basin，the climate changes in this area can be divided into the following four stages: stageⅠ(17~16.7 Ma) is a dry stage; stageⅡ(16.7~7.4 Ma) this stage is wetter than stageⅠ, but is characterized by continuous drought (the drought intensified in 14.7Ma and 10.7 Ma, respectively and 8.7~7.4 Ma shows increased fluctuation ); stage Ⅲ（7.4~5.1 Ma）relatively humid with fluctuation；stage Ⅳ（5.1~4.8 Ma）is a dry stage. 17~16.5 Ma the erosion rate is the high; 16.5~9.8 Ma the erosion rate is relatively low and 8.7~6 Ma the erosion rate is high.The erosion rate of this area shows no obvious connection with climate, but is well consistent with tectonic activities ,namely ,the tectonic active period corresponds with the stages of the high erosion rate or the erosion rate increases dramatically. Thus, in Honggouzi area, the regional tectonic activity is the main factor to control the erosion rate.
Welldeveloped Neocene strata in the western Qaidam Basin were a detailed record of the deformation and uplift of the surrounding mountain, weathering and erosion of the provenance and the process of climate changes. Based on the measurement and analysis of the carbonate contents, chloride ion contents and sulfate radical contents of the Miocene sediment in the Honggouzi section of the western Qaidam Basin，the climate changes in this area can be divided into the following four stages: stageⅠ(17~16.7 Ma) is a dry stage; stageⅡ(16.7~7.4 Ma) this stage is wetter than stageⅠ, but is characterized by continuous drought (the drought intensified in 14.7Ma and 10.7 Ma, respectively and 8.7~7.4 Ma shows increased fluctuation ); stage Ⅲ（7.4~5.1 Ma）relatively humid with fluctuation；stage Ⅳ（5.1~4.8 Ma）is a dry stage. 17~16.5 Ma the erosion rate is the high; 16.5~9.8 Ma the erosion rate is relatively low and 8.7~6 Ma the erosion rate is high.The erosion rate of this area shows no obvious connection with climate, but is well consistent with tectonic activities ,namely ,the tectonic active period corresponds with the stages of the high erosion rate or the erosion rate increases dramatically. Thus, in Honggouzi area, the regional tectonic activity is the main factor to control the erosion rate.
2012, 30(6): 1115-1122.
Abstract:
The lithology of source rock oil reservoir of Lucaogou Formation in Malang sag is diverse and it mainly has mudstone, carbonatite, the transition lithology between carbonatite and mudstone, tuffaceous mud and small amounts of micrite, dolomicrite, tuff and so on. It is characterized by the lamina structure and the thickness of the lamina is 0.1~10 mm. Based on the foundation of the observation of rock cores and cast slice, the macro and micro characteristics of the reservoir of Lucaogou Formation source rock oil in the Malang sag are studied in this paper combining with many methods of experimental analysis, such as Ariron polishing, scanning electronic microscopy(SEM)in the field emission environment, electron backscattering diffraction, Xray energy spectrum, Xray diffraction, petrographic microscope, fluorescent light, and so on. The reservoir space of Lucaogou Formation source rock oil can be divided into five basic types—primary pores, secondary dissolution pores, organic hydrocarbon generating residual pores, cracks and fractures between layers of lamina and so on. Primary pores include intergranular pores which mainly exist between rigid particles and intercrystal pores which exist mainly between quartz crystals and carbonate mineral crystals. Mainly secondary pores are intergranular and intragranular dissolved pores, dissolution fractures as well as caverns in the matrix. Secondary pores formed by the dissolution of the the iron calcite in shale rock samples can be seen in the scanning electron microscopy (SEM). Dissolution fractures are formed by the all or part of dissolution of the fractures in acid fluid which are already filled with calcite first. Matrix type dissolution pores are mainly formed by the dissolution of unstable minerals in the matrix of the fine grain scattered rocks, which are commonly developed and scattered distributed. After the argon polishing rock surface, nm to micron grade dissolution holes can be seen in the scanning electron microscopy. This kind of pores mainly develops in calcareous mudstone, argillaceous limestone, dolomitic mudstone and mudstone. Pores formed by the thermal evolution of organic matter, called organic matter pores, commonly have regular shapes, indentation forms, honeycomb forms and their sizes range from dozens of nanometer to hundreds of nanometer. Porosity are positively correlated with TOC, indicating that residual organic matter hydrocarbon generation pores play an important part in the hydrocarbon source rock reservoir space. The linear density of cracks of source rock oil reservoir of Lucaogou Formation in Malang sag could reach a hundred per meter and are mostly vertical cracks, followed by horizontal crack and high angle oblique crack. The development of the cracks is influenced by brittle mineral content, bed thickness and so on. The survey region is rich in lamina. The slippage between layers and broken cracks in laminite formed the important basis of reservoir space. As a highquality hydrocarbon source rocks, the hydrocarbon generated in laminite can concentrate in reservoir space after an extremely short of primary migration, which is beneficial to the concentration of oil source rocks. Large mounts of nanometer to micron level micro pores and micro cracks develop in the source rock oil reservoir of Lucaogou Formation and their sizes are basically bigger than the diameter of liquid hydrocarbon molecules, so they could form effective reservoir space.
The lithology of source rock oil reservoir of Lucaogou Formation in Malang sag is diverse and it mainly has mudstone, carbonatite, the transition lithology between carbonatite and mudstone, tuffaceous mud and small amounts of micrite, dolomicrite, tuff and so on. It is characterized by the lamina structure and the thickness of the lamina is 0.1~10 mm. Based on the foundation of the observation of rock cores and cast slice, the macro and micro characteristics of the reservoir of Lucaogou Formation source rock oil in the Malang sag are studied in this paper combining with many methods of experimental analysis, such as Ariron polishing, scanning electronic microscopy(SEM)in the field emission environment, electron backscattering diffraction, Xray energy spectrum, Xray diffraction, petrographic microscope, fluorescent light, and so on. The reservoir space of Lucaogou Formation source rock oil can be divided into five basic types—primary pores, secondary dissolution pores, organic hydrocarbon generating residual pores, cracks and fractures between layers of lamina and so on. Primary pores include intergranular pores which mainly exist between rigid particles and intercrystal pores which exist mainly between quartz crystals and carbonate mineral crystals. Mainly secondary pores are intergranular and intragranular dissolved pores, dissolution fractures as well as caverns in the matrix. Secondary pores formed by the dissolution of the the iron calcite in shale rock samples can be seen in the scanning electron microscopy (SEM). Dissolution fractures are formed by the all or part of dissolution of the fractures in acid fluid which are already filled with calcite first. Matrix type dissolution pores are mainly formed by the dissolution of unstable minerals in the matrix of the fine grain scattered rocks, which are commonly developed and scattered distributed. After the argon polishing rock surface, nm to micron grade dissolution holes can be seen in the scanning electron microscopy. This kind of pores mainly develops in calcareous mudstone, argillaceous limestone, dolomitic mudstone and mudstone. Pores formed by the thermal evolution of organic matter, called organic matter pores, commonly have regular shapes, indentation forms, honeycomb forms and their sizes range from dozens of nanometer to hundreds of nanometer. Porosity are positively correlated with TOC, indicating that residual organic matter hydrocarbon generation pores play an important part in the hydrocarbon source rock reservoir space. The linear density of cracks of source rock oil reservoir of Lucaogou Formation in Malang sag could reach a hundred per meter and are mostly vertical cracks, followed by horizontal crack and high angle oblique crack. The development of the cracks is influenced by brittle mineral content, bed thickness and so on. The survey region is rich in lamina. The slippage between layers and broken cracks in laminite formed the important basis of reservoir space. As a highquality hydrocarbon source rocks, the hydrocarbon generated in laminite can concentrate in reservoir space after an extremely short of primary migration, which is beneficial to the concentration of oil source rocks. Large mounts of nanometer to micron level micro pores and micro cracks develop in the source rock oil reservoir of Lucaogou Formation and their sizes are basically bigger than the diameter of liquid hydrocarbon molecules, so they could form effective reservoir space.
2012, 30(6): 1123-1129.
Abstract:
Based on core observation, thinsection identification and well logging data analysis, Triassic reservoir physical property, pore type, diagenesis and reservoir characteristics of the main control factors at northwestern margin of Cheguai area, Junggar basin were studied. Fan delta front facies reservoir experienced mechanical compaction, cementation, dissolution metasomatism, various diagenesis, and compaction effect of reservoir characteristics of the main factors. According to diagenesis and authigenic mineral characteristics, it is late diagenetic stage B period that Diagenesis of the Triassic reservoirs in Cheguai Area.With the depth increasing and compaction enhancing, physical properties become bad, which can make the porosity reduces 20%. Zeolite and carbonate cement dissolution can make the porosity is increased up to 3%, total porosity distribution range between 6%~18%, and the permeability distribution in the range of 0.08×10-3～40.0×10-3μm2.
Based on core observation, thinsection identification and well logging data analysis, Triassic reservoir physical property, pore type, diagenesis and reservoir characteristics of the main control factors at northwestern margin of Cheguai area, Junggar basin were studied. Fan delta front facies reservoir experienced mechanical compaction, cementation, dissolution metasomatism, various diagenesis, and compaction effect of reservoir characteristics of the main factors. According to diagenesis and authigenic mineral characteristics, it is late diagenetic stage B period that Diagenesis of the Triassic reservoirs in Cheguai Area.With the depth increasing and compaction enhancing, physical properties become bad, which can make the porosity reduces 20%. Zeolite and carbonate cement dissolution can make the porosity is increased up to 3%, total porosity distribution range between 6%~18%, and the permeability distribution in the range of 0.08×10-3～40.0×10-3μm2.
2012, 30(6): 1130-1139.
Abstract:
This paper applies reservoir fluorescence, reservoir inclusion and analysis of geochemical characteristics of crude oil and reservoir extracts, combined with distribution and contact relation of reservoir and source rock to study the characteristics of reservoir formation and the controlling factors of Chang 8 oilbearing reservoir in Huaqing area of Ordos basin thoroughly and systematically. Chang 8 reservoir has two different colors of fluorescence, the homogenization temperature of inclusion shows two peaks, the maturity of flow crude oil is higher than that of the reservoir extracts, and the reservoir extracts have serious biodegradation, it is shown that there are two stages of reservoirforming in Chang 8 oilbearing formation. According to the evolution history of source rock and homogenization temperature of reservoir inclusion, it can be implicated that the first stage of reservoirforming occurred in Late Jurassic, Chang 7 source rock reached the hydrocarbon generation threshold at the time, the generated oil with low maturity was biodegraded and formed asphalt. Now the oil in the reservoir is mainly mature which was gathered in Early Cretaceous. It is pointed out that the distribution of Chang 8 reservoir is controlled by multiple factors such as sedimentary facies belt, reservoir characteristics, hydrocarbon source rocks, the contact relationship of reservoir and source rock, pore blockage of asphalt etc. Huaqing area is near the depositional center of the Chang 7 source rock, but the thickness and purity of the source rock is different, source rock thickness and the carrier bed of the reservoir and source rock together control the oil potentials of Chang 8 reservoir, and the dense lithology segment between the reservoir and hydrocarbon source rock may block the migration of the oil to the Chang 8 reservoir.
This paper applies reservoir fluorescence, reservoir inclusion and analysis of geochemical characteristics of crude oil and reservoir extracts, combined with distribution and contact relation of reservoir and source rock to study the characteristics of reservoir formation and the controlling factors of Chang 8 oilbearing reservoir in Huaqing area of Ordos basin thoroughly and systematically. Chang 8 reservoir has two different colors of fluorescence, the homogenization temperature of inclusion shows two peaks, the maturity of flow crude oil is higher than that of the reservoir extracts, and the reservoir extracts have serious biodegradation, it is shown that there are two stages of reservoirforming in Chang 8 oilbearing formation. According to the evolution history of source rock and homogenization temperature of reservoir inclusion, it can be implicated that the first stage of reservoirforming occurred in Late Jurassic, Chang 7 source rock reached the hydrocarbon generation threshold at the time, the generated oil with low maturity was biodegraded and formed asphalt. Now the oil in the reservoir is mainly mature which was gathered in Early Cretaceous. It is pointed out that the distribution of Chang 8 reservoir is controlled by multiple factors such as sedimentary facies belt, reservoir characteristics, hydrocarbon source rocks, the contact relationship of reservoir and source rock, pore blockage of asphalt etc. Huaqing area is near the depositional center of the Chang 7 source rock, but the thickness and purity of the source rock is different, source rock thickness and the carrier bed of the reservoir and source rock together control the oil potentials of Chang 8 reservoir, and the dense lithology segment between the reservoir and hydrocarbon source rock may block the migration of the oil to the Chang 8 reservoir.
2012, 30(6): 1140-1148.
Abstract:
There are three types of crude oil in the Malang sag, Santanghu Basin. Type Ⅰ oil is from the source rocks of Permian Lucaogou Formation. Type Ⅱ oil is from the source rocks of Carboniferous Haerjiawu Formation and type Ⅲ oil is mixed source oil of type Ⅰ oil and type Ⅱ oil. Based on the study of the intensity of faults activity and the matching relationship between vertical transporting faults and the source rock, and then combined with the analysis data of nitrogen compounds, vertical migration characteristics of the oil in the Malang sag are studied in this paper. The research results are as follows. Firstly, the vertical migration ability of the oil is controlled by the intensity of faults activity, and the oil can accumulate in the overlying strata by migrating when the vertical transporting faults match the source rock well. When there are only vertical transporting faults or there is only source rock, oil can not accumulated in the overlying strata. The Jurassic was broken through by the vertical transporting faults nearby the thickness center of the Permian Lucaogou Formation source rock, so type Ⅰ oil which was generated by the source rock of the Lucaogou Formation could accumulate in the Jurassic through migration. The Permian and Jurassic were not broken by most faults nearby the Carboniferous Haerjiawu Formation source rock, so type Ⅱ oil which was generated by the source rock of the Carboniferous Haerjiawu Formation could not accumulate in the Permian and Jurassic, and it only accumulated at the top of Carboniferous. Besides, combined with the analysis of transporting faults, nitrogen compounds can trace hydrocarbon vertical migration well. The absolute concentration of nitrogen compounds in the crude oil is gradually reduced. And nitrogenshielded isomers are more enriched than parts of nitrogenshielded isomers and nitrogenexposed isomers from the deep to the shallow strata. For example, the value of 1,8DMC/1,3DMC and 1,8DMC/2,4DMC both are increased from the deep to the shallow strata. These parameters all trace the hydrocarbon vertical migration through the transporting faults from the deep to the shallow strata well.
There are three types of crude oil in the Malang sag, Santanghu Basin. Type Ⅰ oil is from the source rocks of Permian Lucaogou Formation. Type Ⅱ oil is from the source rocks of Carboniferous Haerjiawu Formation and type Ⅲ oil is mixed source oil of type Ⅰ oil and type Ⅱ oil. Based on the study of the intensity of faults activity and the matching relationship between vertical transporting faults and the source rock, and then combined with the analysis data of nitrogen compounds, vertical migration characteristics of the oil in the Malang sag are studied in this paper. The research results are as follows. Firstly, the vertical migration ability of the oil is controlled by the intensity of faults activity, and the oil can accumulate in the overlying strata by migrating when the vertical transporting faults match the source rock well. When there are only vertical transporting faults or there is only source rock, oil can not accumulated in the overlying strata. The Jurassic was broken through by the vertical transporting faults nearby the thickness center of the Permian Lucaogou Formation source rock, so type Ⅰ oil which was generated by the source rock of the Lucaogou Formation could accumulate in the Jurassic through migration. The Permian and Jurassic were not broken by most faults nearby the Carboniferous Haerjiawu Formation source rock, so type Ⅱ oil which was generated by the source rock of the Carboniferous Haerjiawu Formation could not accumulate in the Permian and Jurassic, and it only accumulated at the top of Carboniferous. Besides, combined with the analysis of transporting faults, nitrogen compounds can trace hydrocarbon vertical migration well. The absolute concentration of nitrogen compounds in the crude oil is gradually reduced. And nitrogenshielded isomers are more enriched than parts of nitrogenshielded isomers and nitrogenexposed isomers from the deep to the shallow strata. For example, the value of 1,8DMC/1,3DMC and 1,8DMC/2,4DMC both are increased from the deep to the shallow strata. These parameters all trace the hydrocarbon vertical migration through the transporting faults from the deep to the shallow strata well.
2012, 30(6): 1149-1155.
Abstract:
Beier Depression is one of second tectonic units in Lake Beier depression, development from the bottom of the bed rock of the Upper Triassic Budate Group(T3b), the Tongbomiao group（J2t） of Upper Jurassic, Nantun group(K1n), Damoguaihe group(K1d) and Yimin group(K1y) of Lower Cretaceous, Qingyuangang group(K1q) Formation of the Yimin group and the upper Cretaceous. Combined with results of previous studies, this paper considers source rock, trap, and the source fault are main control factors of hydrocarbon accumulation in Beir depression. Oil and gas mainly from dark mudstone of K1n and source rock with better conditions, to provide sufficient oil source for hydrocarbon migration and accumulation in Beir depression. Traps are mainly two kinds of type, crack traps and fault traps include fault block, fault seal and fault lithologic traps in Beir depression.The reservoirs of T3b and K1d and source rocks of K1n located in different layers, faults should be oil migration transporting main pathway.By studies on spatial matching relation of oil reservoir forming factors in Beier depression K1n source rock, fracture, fault trap and source fault, it was considered that fracture and fault traps had 4 contact relations with K1n source rocks in space in Beier depression. The first is that fracture traps of Budate group are located at the side of the top of K1n source rocks. They are connected by T5 -T1faults. The second is that K1nfault traps are located in K1n source rocks. They are connected by T23-T1faults The third is that K1n fault traps are located outside of K1n source rocks. They are connected by sand body connected by T23-T1 aults. The forth is that K1d2 fault traps are located above of K1n source rocks. They are connected by T23-T1faults .The control effect of space matching relation of 3 reservoir forming factors on oil accumulation and distribution was showed as follows three aspects. ①Distribution of oil reservoir was controlled by the distribution of K1n source rock. ②Oil reservoirs are all distributed along source faults. The shorter the distance from trap to K1n source rock, the better it is to form oil reservoir.
Beier Depression is one of second tectonic units in Lake Beier depression, development from the bottom of the bed rock of the Upper Triassic Budate Group(T3b), the Tongbomiao group（J2t） of Upper Jurassic, Nantun group(K1n), Damoguaihe group(K1d) and Yimin group(K1y) of Lower Cretaceous, Qingyuangang group(K1q) Formation of the Yimin group and the upper Cretaceous. Combined with results of previous studies, this paper considers source rock, trap, and the source fault are main control factors of hydrocarbon accumulation in Beir depression. Oil and gas mainly from dark mudstone of K1n and source rock with better conditions, to provide sufficient oil source for hydrocarbon migration and accumulation in Beir depression. Traps are mainly two kinds of type, crack traps and fault traps include fault block, fault seal and fault lithologic traps in Beir depression.The reservoirs of T3b and K1d and source rocks of K1n located in different layers, faults should be oil migration transporting main pathway.By studies on spatial matching relation of oil reservoir forming factors in Beier depression K1n source rock, fracture, fault trap and source fault, it was considered that fracture and fault traps had 4 contact relations with K1n source rocks in space in Beier depression. The first is that fracture traps of Budate group are located at the side of the top of K1n source rocks. They are connected by T5 -T1faults. The second is that K1nfault traps are located in K1n source rocks. They are connected by T23-T1faults The third is that K1n fault traps are located outside of K1n source rocks. They are connected by sand body connected by T23-T1 aults. The forth is that K1d2 fault traps are located above of K1n source rocks. They are connected by T23-T1faults .The control effect of space matching relation of 3 reservoir forming factors on oil accumulation and distribution was showed as follows three aspects. ①Distribution of oil reservoir was controlled by the distribution of K1n source rock. ②Oil reservoirs are all distributed along source faults. The shorter the distance from trap to K1n source rock, the better it is to form oil reservoir.
2012, 30(6): 1156-1164.
Abstract:
The thermal simulation experiment of Yaha and Hade crude oil samples in Tarim Basin was carried out, by using the gold tube confined system. The yield characteristics and kinetic parameters of cracking gases from Yaha and Hade oil samples were studied. The results demonstrate that the Yaha and Hade oil samples have high total gas yields (738.87 ml/g, 598.98 ml/g) and C25 yields (256.85 ml/g, 188.63 ml/g). Differences are existed in the kinetic parameters of cracking gases in the Yaha and Hade oils. The activation energy distributions of methane, ethane and propane generated from the Yaha oil sample are in the range of (66～83)×4.186kJ/mol, (59～72)×4.186kJ/mol, and (59～65)×4.186kJ/mol. Their frequency factors from the Yaha oil sample are 2.07×1016s-1, 1.0×1014 s-1, and 1.0×1014s-1, respectively. The activation energy distributions of methane, ethane and propane from the Hade oil sample are in the range of (63～84)×4.186 kJ/mol, (57～63)×4.186 kJ/mol, and (58～70)× 4.186 kJ/mol. Their frequency factors from the Hade oil sample are 1.42×1016s-1, 1.0×1014s-1, and 1.0×1014s-1, respectively. The Mandong 1 gas pool in the eastern Tarim Basin was taken as an example and its kinetic modeling of gas generation was studied. It is suggested that gas source of the Mandong 1 gas pool was resulted from a large number of crude oil cracking.
The thermal simulation experiment of Yaha and Hade crude oil samples in Tarim Basin was carried out, by using the gold tube confined system. The yield characteristics and kinetic parameters of cracking gases from Yaha and Hade oil samples were studied. The results demonstrate that the Yaha and Hade oil samples have high total gas yields (738.87 ml/g, 598.98 ml/g) and C25 yields (256.85 ml/g, 188.63 ml/g). Differences are existed in the kinetic parameters of cracking gases in the Yaha and Hade oils. The activation energy distributions of methane, ethane and propane generated from the Yaha oil sample are in the range of (66～83)×4.186kJ/mol, (59～72)×4.186kJ/mol, and (59～65)×4.186kJ/mol. Their frequency factors from the Yaha oil sample are 2.07×1016s-1, 1.0×1014 s-1, and 1.0×1014s-1, respectively. The activation energy distributions of methane, ethane and propane from the Hade oil sample are in the range of (63～84)×4.186 kJ/mol, (57～63)×4.186 kJ/mol, and (58～70)× 4.186 kJ/mol. Their frequency factors from the Hade oil sample are 1.42×1016s-1, 1.0×1014s-1, and 1.0×1014s-1, respectively. The Mandong 1 gas pool in the eastern Tarim Basin was taken as an example and its kinetic modeling of gas generation was studied. It is suggested that gas source of the Mandong 1 gas pool was resulted from a large number of crude oil cracking.
2012, 30(6): 1165-1171.
Abstract:
Geochemical analysis was completed for crude oils from Yakela oilfield to investigate geochemical characteristics and genetic type of crude oils. The heptane value, isoheptane value and MCYC6 index of crude oils in Yakela oilfield provided excellent evidence for marine oils characteristics. Compoundspecific carbon isotope of light hydrocarbons indicated that oils in Yakela oilfield were marine oils with relative high maturity for lower oils. C21/C23 tricyclic diterpane and C28 steranes relative content in C27~C29steranes were consistent with oils derived from O3source rock in Tarim Basin. Characteristics of triaromatic steroids and methyl triaromatic steroids further proved the O3 source rock was the source of oils in Yakela oilfield. A significant difference was found in carbon isotope composition of whole oil and fractions of TD2 well ,T904 well and Yakela oilfield，which suggested the crude oils among deeper and shallower layers in Yakela oilfield were marine oils and had obvious diffrences with crude oils derived from ∈—O1. Based on the ight hydrocarbons, tricyclic terpanes, C28steranes, triaromatic steranes and methyl triaromatic steranes, and carbon isotope composition of whole oil and fractions, it is suggested that the crude oils of Yakela oilfield in deeper and shallower layers had the common source and derived from O3 source rock.
Geochemical analysis was completed for crude oils from Yakela oilfield to investigate geochemical characteristics and genetic type of crude oils. The heptane value, isoheptane value and MCYC6 index of crude oils in Yakela oilfield provided excellent evidence for marine oils characteristics. Compoundspecific carbon isotope of light hydrocarbons indicated that oils in Yakela oilfield were marine oils with relative high maturity for lower oils. C21/C23 tricyclic diterpane and C28 steranes relative content in C27~C29steranes were consistent with oils derived from O3source rock in Tarim Basin. Characteristics of triaromatic steroids and methyl triaromatic steroids further proved the O3 source rock was the source of oils in Yakela oilfield. A significant difference was found in carbon isotope composition of whole oil and fractions of TD2 well ,T904 well and Yakela oilfield，which suggested the crude oils among deeper and shallower layers in Yakela oilfield were marine oils and had obvious diffrences with crude oils derived from ∈—O1. Based on the ight hydrocarbons, tricyclic terpanes, C28steranes, triaromatic steranes and methyl triaromatic steranes, and carbon isotope composition of whole oil and fractions, it is suggested that the crude oils of Yakela oilfield in deeper and shallower layers had the common source and derived from O3 source rock.
2012, 30(6): 1172-1179.
Abstract:
As for the gasgenerating potential at the overmature stage, the authors used the RockEval rock pyrologger and TGMS hightemperature pyrogenating simulated experiment device to carry out a series of experiment and research. By using the coal and carbonaceous mudstone of Jurassic in Junggar Basin and outcrop coal sample of the Permian system and Carboniferous carbonaceous mudstone in Ordos Basin, we carried out the gasgenerating simulation experiment and the temperature is from 300℃ to 800℃. According to the result, all the rocks have generated a lot of gas when the temperature is lower than 600℃(that is Ro＜2.0%～2.5%). When increasing the experiment temperature from 600℃ to 800℃, which means to raise Ro from 2.0%～2.5% to 5.0%, we found that both the coal and the carbonaceous mudstone in the two Basin can generate a great amount of natural gas between 600～800℃. The gas generated from the carboniferous carbonaceous mudstone accounts for 25.38%, 34.39%. The gas generated from the two type source rocks at the overmature stage accounts for 20%～35% of the total generated gas volume. In an attempt to verify the above phenomenon, we have cooperated with Taiyuan Institute of Coal Chemistry Chinese Academy of Sciences to carry out the source rock thermogravimetricmassspectrometric thermal simulated experiment and have got very similar result.According to the result of thermogravimetricmassspectrometric experiment on the shale of sea facies and the mud stone of lake facies, the two samples of Songliao Basin, the organic matter of Ⅱ2 residue gasgenerating when the temperature is between 600～800℃ accounts for 7% of the total generated gas volume or so and the organic matters of Ⅱ1 organic matter accounts for 5%. However, the gasgenerating volume is much smaller than the coalrelated source rock. There is a tendency in which the type of organic matter is worsening and the residue gas volume is reducing at high temperature, which is similar to that experiment result on the abovementioned pyrogenating gas generation rate. When the temperature is between 800～1000℃, the gasgenerating potential disappears, which is consistent with the experiment result of coalrelated source rock. Therefore, a large amount of natural gas can be generated at the overmature stage(Ro≥2.5)for coal and carbonaceous mudstone, and the volume can account for 20%,or even more. The low limit of Ro extend to 5.0% . The generated gas volume stops increasing when the temperature is larger than 800℃, so the simulation temperature 800℃ will be enough for the gasgeneration reflection.
As for the gasgenerating potential at the overmature stage, the authors used the RockEval rock pyrologger and TGMS hightemperature pyrogenating simulated experiment device to carry out a series of experiment and research. By using the coal and carbonaceous mudstone of Jurassic in Junggar Basin and outcrop coal sample of the Permian system and Carboniferous carbonaceous mudstone in Ordos Basin, we carried out the gasgenerating simulation experiment and the temperature is from 300℃ to 800℃. According to the result, all the rocks have generated a lot of gas when the temperature is lower than 600℃(that is Ro＜2.0%～2.5%). When increasing the experiment temperature from 600℃ to 800℃, which means to raise Ro from 2.0%～2.5% to 5.0%, we found that both the coal and the carbonaceous mudstone in the two Basin can generate a great amount of natural gas between 600～800℃. The gas generated from the carboniferous carbonaceous mudstone accounts for 25.38%, 34.39%. The gas generated from the two type source rocks at the overmature stage accounts for 20%～35% of the total generated gas volume. In an attempt to verify the above phenomenon, we have cooperated with Taiyuan Institute of Coal Chemistry Chinese Academy of Sciences to carry out the source rock thermogravimetricmassspectrometric thermal simulated experiment and have got very similar result.According to the result of thermogravimetricmassspectrometric experiment on the shale of sea facies and the mud stone of lake facies, the two samples of Songliao Basin, the organic matter of Ⅱ2 residue gasgenerating when the temperature is between 600～800℃ accounts for 7% of the total generated gas volume or so and the organic matters of Ⅱ1 organic matter accounts for 5%. However, the gasgenerating volume is much smaller than the coalrelated source rock. There is a tendency in which the type of organic matter is worsening and the residue gas volume is reducing at high temperature, which is similar to that experiment result on the abovementioned pyrogenating gas generation rate. When the temperature is between 800～1000℃, the gasgenerating potential disappears, which is consistent with the experiment result of coalrelated source rock. Therefore, a large amount of natural gas can be generated at the overmature stage(Ro≥2.5)for coal and carbonaceous mudstone, and the volume can account for 20%,or even more. The low limit of Ro extend to 5.0% . The generated gas volume stops increasing when the temperature is larger than 800℃, so the simulation temperature 800℃ will be enough for the gasgeneration reflection.
2012, 30(6): 1180-1184.
Abstract:
As compared to the device developed by our predecessors, the newly established adsorbed gas degasificationcollection device has a series of advantages such as wide sample application range, large sample inlet, high vaccum, shorttime sample smashing, low crushing temperature and waterfree gas collection, which make sure the geochemical characteristics of acquired adsorbed gas sample is the same as the adsorbed gas on corresponding hydrocarbonsource rock. The results show that the acquired adsorbed gases are composed mainly of hydrocarbon gas and carbon dioxide gas, with the hydrocarbon gas accounting for more than 80%, and can be measured reliably for theirδ13C1~δ13C3 data, even δ13C4~δ13C5 data. The results of carbon isotope test analysis satisfy the needs for the geochemical study and application of adsorbed gases. The above new techniques of experimental geochemistry establish the new direct nature gassource correlation method, prove that the old usual method of indirect nature gassource correlation is scientific and authentic, and set up the experimental basis of the research and application of adsorbed gas on hydrocarbonsource rock.
As compared to the device developed by our predecessors, the newly established adsorbed gas degasificationcollection device has a series of advantages such as wide sample application range, large sample inlet, high vaccum, shorttime sample smashing, low crushing temperature and waterfree gas collection, which make sure the geochemical characteristics of acquired adsorbed gas sample is the same as the adsorbed gas on corresponding hydrocarbonsource rock. The results show that the acquired adsorbed gases are composed mainly of hydrocarbon gas and carbon dioxide gas, with the hydrocarbon gas accounting for more than 80%, and can be measured reliably for theirδ13C1~δ13C3 data, even δ13C4~δ13C5 data. The results of carbon isotope test analysis satisfy the needs for the geochemical study and application of adsorbed gases. The above new techniques of experimental geochemistry establish the new direct nature gassource correlation method, prove that the old usual method of indirect nature gassource correlation is scientific and authentic, and set up the experimental basis of the research and application of adsorbed gas on hydrocarbonsource rock.
