2009 Vol. 27, No. 3
Display Method:
2009, 27(3): 381-389.
Abstract:
Lower Ordovician Majiagou Formation in Ordos Basin is a shallow marine carbonate sequence with evaporate stratum. The centralwestern part in the basin often contains several dolomite units, which are major reservoir rock. Some researchers considered them as reflux dolomite near surface. However, petrography and geochemistry of dolomite suggest that this dolomite have evidence of burial origin.
〓〓Majiagou dolomite (M5) included dullred cathodoluminescence, trace element of 170 ~ 210 ppm for Mn and 5500 ~ 6200 ppm for Fe, stable isotopic oxygen composition of -7.093~-9.932 PDB, the average is -8.671 PDB, for matrix and vugfilling saddle dolomite and bright dolomite cement, stable isotopic strontium composition of 0.709 766~0.708 65 for 87Sr/86Sr (influenced by silicaclastics materialities, sea water). Dolomite replaced host rock along the fractures in the section. These data about Majiagou dolomite (M5) was formed in the burial condition.
〓〓REE pattern of dolomite are distinctly different from sea water, commonly are short of negative anomaly of Eu and Ce, such distinct REE signatures probably reflected interaction between diagenetic fluid and host rock and siliciclastic material. Homogenization temperature of 160℃～220℃, salinity of 5wt% ~ 25wt%, suggest dolomitization occurred at high temperature and larger pressure, replacing fluids is brines.
〓〓The pervasive dolomite, trace MVT mineral (sphalerites, galenas and iron sulfides), potassium(K)silicate mineral (Kfeldspar), quartz, volcanic tuffs, in these rock, which preserve a regional hydrothermal signatures.
〓〓The petrography and geochemistry of Majiagou dolomite show that this dolomite (M5) has evidence of hydrothermal dolomite (HTD) and central field (gas) are now identified to be of HTD type, typically with a strong structural control on localization.
Lower Ordovician Majiagou Formation in Ordos Basin is a shallow marine carbonate sequence with evaporate stratum. The centralwestern part in the basin often contains several dolomite units, which are major reservoir rock. Some researchers considered them as reflux dolomite near surface. However, petrography and geochemistry of dolomite suggest that this dolomite have evidence of burial origin.
〓〓Majiagou dolomite (M5) included dullred cathodoluminescence, trace element of 170 ~ 210 ppm for Mn and 5500 ~ 6200 ppm for Fe, stable isotopic oxygen composition of -7.093~-9.932 PDB, the average is -8.671 PDB, for matrix and vugfilling saddle dolomite and bright dolomite cement, stable isotopic strontium composition of 0.709 766~0.708 65 for 87Sr/86Sr (influenced by silicaclastics materialities, sea water). Dolomite replaced host rock along the fractures in the section. These data about Majiagou dolomite (M5) was formed in the burial condition.
〓〓REE pattern of dolomite are distinctly different from sea water, commonly are short of negative anomaly of Eu and Ce, such distinct REE signatures probably reflected interaction between diagenetic fluid and host rock and siliciclastic material. Homogenization temperature of 160℃～220℃, salinity of 5wt% ~ 25wt%, suggest dolomitization occurred at high temperature and larger pressure, replacing fluids is brines.
〓〓The pervasive dolomite, trace MVT mineral (sphalerites, galenas and iron sulfides), potassium(K)silicate mineral (Kfeldspar), quartz, volcanic tuffs, in these rock, which preserve a regional hydrothermal signatures.
〓〓The petrography and geochemistry of Majiagou dolomite show that this dolomite (M5) has evidence of hydrothermal dolomite (HTD) and central field (gas) are now identified to be of HTD type, typically with a strong structural control on localization.
2009, 27(3): 404-409.
Abstract:
Through research on the oolitic reservoir of Feixianguan Formation in the Shunan Area，Sichuan Basin，it is indicated that the main reservoir spaces of oolitic reservoir are moldic pore and intragranular dissolved pore , which is formed by meteoric water leaching. The reservoir development in the upper part of Oolitic Beach, with obvious characteristics of separated layer stimulation. Combining the study of palaeogeomorphology, eustatic sea level change, palaeoclimate and diagenetic evolution, it is calculated that the mode of origin of oolitic reservoir is syngenetic karst, reservoir is formed by meteoric water leaching. Oolitic beach at the chapada of palaeogeomorphology provided material basis for the reservoir formation and evolution, and controlled the distribution of reservoir. Paleogeomorphology, eustatic sea level change and palaeoclimate determined the intensity of syngenetic karst, and dominated reservoir quality. Subjacent karst and tectonic disruption play a role in improving reservoir performance, but is limited in effect.
Through research on the oolitic reservoir of Feixianguan Formation in the Shunan Area，Sichuan Basin，it is indicated that the main reservoir spaces of oolitic reservoir are moldic pore and intragranular dissolved pore , which is formed by meteoric water leaching. The reservoir development in the upper part of Oolitic Beach, with obvious characteristics of separated layer stimulation. Combining the study of palaeogeomorphology, eustatic sea level change, palaeoclimate and diagenetic evolution, it is calculated that the mode of origin of oolitic reservoir is syngenetic karst, reservoir is formed by meteoric water leaching. Oolitic beach at the chapada of palaeogeomorphology provided material basis for the reservoir formation and evolution, and controlled the distribution of reservoir. Paleogeomorphology, eustatic sea level change and palaeoclimate determined the intensity of syngenetic karst, and dominated reservoir quality. Subjacent karst and tectonic disruption play a role in improving reservoir performance, but is limited in effect.
Prediction of the Secondary Porosity Zone of Fuyu Oil Layer in the 〖JZ〗West of Daqing Placanticline
2009, 27(3): 419-426.
Abstract:
In order to find the reservoir which develop the secondary porosity in the context of generally low porosity and low permeability, on the basis of the analysis of contributing factor of secondary porosity and diagenesis research of the reservoir, Combined impact of the formation of secondary porosity factors, we have predicted the porosity developed area of Fuyu oil layer in the West of Daqing placanticline. Research shows that secondary porosity in the region is mainly affected by the formation of carbonate and organic acids which come from Qingshankou group, and by the impact of fault controlled and overpressure, secondary porosity mainly distributed in the surrounding region of Qijia sag, Gulong sag and Longhupao terrace, some secondary porosity distributed in the western slope which developed by meteorological water eluviations.
In order to find the reservoir which develop the secondary porosity in the context of generally low porosity and low permeability, on the basis of the analysis of contributing factor of secondary porosity and diagenesis research of the reservoir, Combined impact of the formation of secondary porosity factors, we have predicted the porosity developed area of Fuyu oil layer in the West of Daqing placanticline. Research shows that secondary porosity in the region is mainly affected by the formation of carbonate and organic acids which come from Qingshankou group, and by the impact of fault controlled and overpressure, secondary porosity mainly distributed in the surrounding region of Qijia sag, Gulong sag and Longhupao terrace, some secondary porosity distributed in the western slope which developed by meteorological water eluviations.
2009, 27(3): 435-442.
Abstract:
The time equivalent Yingshan Formation in Tarim Basin has been discussed. Based on this, the sedimentary environment of Yingshan Formation was reconstructed, with the aid of outcrops, seismic facies, strata contour map and core analysis, and draw three conclusions as follows: ①The distribution characteristic of platform edge at Daobaowanian Stage and Dawanian Stage and the type of platform were definite. Besides, the viewpoint that the discontinuity of reef and beach along the platform edge was put forward. ②Carbonate sands are wild range and the shape is multifarious. Generally, they are elongate or elliptical and strike of sands is parallel to the platform edge. ③The existence of intrashelf basin was proved. Along the edge of intrashelf basin there are carbonate sands and bioherm, generally sands on windward side and bioherm on lee side. In intrashelf basin sediments predominatly consist of pelagic carbonates, which are commonly rich in organic content.
The time equivalent Yingshan Formation in Tarim Basin has been discussed. Based on this, the sedimentary environment of Yingshan Formation was reconstructed, with the aid of outcrops, seismic facies, strata contour map and core analysis, and draw three conclusions as follows: ①The distribution characteristic of platform edge at Daobaowanian Stage and Dawanian Stage and the type of platform were definite. Besides, the viewpoint that the discontinuity of reef and beach along the platform edge was put forward. ②Carbonate sands are wild range and the shape is multifarious. Generally, they are elongate or elliptical and strike of sands is parallel to the platform edge. ③The existence of intrashelf basin was proved. Along the edge of intrashelf basin there are carbonate sands and bioherm, generally sands on windward side and bioherm on lee side. In intrashelf basin sediments predominatly consist of pelagic carbonates, which are commonly rich in organic content.
2009, 27(3): 452-457.
Abstract:
Based on the character of primary rock and rockweathering, this article deals with the mineralization and the course of mineralizing for bauxite in the WuchuanZheng′anDaozhen area, Northern Guizhou. It is considered that metallogenic primary rock of bauxite in the WuchuanZheng′anDaozhen area is marine shale of lower Silurian Hanjiadian group which has a lot of hydromica, and it is the substance condition to form ore deposit. Bauxite from ore formation caused by weathering, breakage and transportation, segregation and purification to accumulation, consequently, the figure of metallogenic model for bauxite in the WuchuanZheng’anDaozhen area is established.
Based on the character of primary rock and rockweathering, this article deals with the mineralization and the course of mineralizing for bauxite in the WuchuanZheng′anDaozhen area, Northern Guizhou. It is considered that metallogenic primary rock of bauxite in the WuchuanZheng′anDaozhen area is marine shale of lower Silurian Hanjiadian group which has a lot of hydromica, and it is the substance condition to form ore deposit. Bauxite from ore formation caused by weathering, breakage and transportation, segregation and purification to accumulation, consequently, the figure of metallogenic model for bauxite in the WuchuanZheng’anDaozhen area is established.
2009, 27(3): 470-478.
Abstract:
Analysis and analogy of sequence are the most basic contents in the study on sequence stratigraphy. Currently, it is main way to establish highfrequency sequence stratigraphic framework by application of drilling data, and the application of seismic data, but the typical primary profile analysis, is less in China, thus to lead to some crosslayer phenomena. The key of sequence stratigraphy research is comprehensive utilization of outcrop, paleontology, logging and seismic data, and the highresolution core, logging and threedimensional seismic data is three basic components of sequence stratigraphy analysis. It will be finally possible to establish more actual sequence stratigraphy framework by mutual verification of these three types of information. Based on drilling sequence and seismic data, the well seismic unified stratigraphic framework is established by using synthetic seismogram, which is a reliable basis for analyzing the sequence stratigraphy internal characteristics and searching for hidden hydrocarbon traps. This paper established the 34 grade sequence stratigraphy framework of seismic and drilling mutually unified, which was divided into four thirdorder sequences (of which three in Qingshankou Group and one in Yaojia Group) and 20 fourthorder sequences in Qingshankou Yaojia group of Upper Cretaceous in Sifangtuozi area of southern Songliao Basin.
Analysis and analogy of sequence are the most basic contents in the study on sequence stratigraphy. Currently, it is main way to establish highfrequency sequence stratigraphic framework by application of drilling data, and the application of seismic data, but the typical primary profile analysis, is less in China, thus to lead to some crosslayer phenomena. The key of sequence stratigraphy research is comprehensive utilization of outcrop, paleontology, logging and seismic data, and the highresolution core, logging and threedimensional seismic data is three basic components of sequence stratigraphy analysis. It will be finally possible to establish more actual sequence stratigraphy framework by mutual verification of these three types of information. Based on drilling sequence and seismic data, the well seismic unified stratigraphic framework is established by using synthetic seismogram, which is a reliable basis for analyzing the sequence stratigraphy internal characteristics and searching for hidden hydrocarbon traps. This paper established the 34 grade sequence stratigraphy framework of seismic and drilling mutually unified, which was divided into four thirdorder sequences (of which three in Qingshankou Group and one in Yaojia Group) and 20 fourthorder sequences in Qingshankou Yaojia group of Upper Cretaceous in Sifangtuozi area of southern Songliao Basin.
2009, 27(3): 487-493.
Abstract:
The Bogda Mountain located between Junggar basin and TurpanHami basin. Its uplift time has been debated for a long time and is of important geotectonic significance. Based on
the information of predecessors and the study area, it is considered that the Bogda area was mainly in extensional environment between Early Carboniferous to Middle Permian; in later Pernianearly Triassic period, the particle size, distribution, morphology, composition changes of TurpanHami Basin sediments and stratigraphic contact relationship show that the initial uplifting time of the Bogda mountain took place at late Permian. According to the great changes of time and space about sedimentary facies, ZTR index and sandstone detrital compositions of Xishanyao formation, Sanjianfang formation and Qiketai formation in middle Jurassic epoch on Taibei sag of TurpanHami Basin, it is concluded that the reuplift time of Bogda Mountain took place at late Xishanyao formation, and became the north source supplying area of the TurpanHami Basin. But the maximum uplift amplitude during the Himalayan movement formed the present basinorogen pattern.
The Bogda Mountain located between Junggar basin and TurpanHami basin. Its uplift time has been debated for a long time and is of important geotectonic significance. Based on
the information of predecessors and the study area, it is considered that the Bogda area was mainly in extensional environment between Early Carboniferous to Middle Permian; in later Pernianearly Triassic period, the particle size, distribution, morphology, composition changes of TurpanHami Basin sediments and stratigraphic contact relationship show that the initial uplifting time of the Bogda mountain took place at late Permian. According to the great changes of time and space about sedimentary facies, ZTR index and sandstone detrital compositions of Xishanyao formation, Sanjianfang formation and Qiketai formation in middle Jurassic epoch on Taibei sag of TurpanHami Basin, it is concluded that the reuplift time of Bogda Mountain took place at late Xishanyao formation, and became the north source supplying area of the TurpanHami Basin. But the maximum uplift amplitude during the Himalayan movement formed the present basinorogen pattern.
2009, 27(3): 503-510.
Abstract:
In this paper, 21 lake sediments samples were collected from Tajiguri situated on the western Nam Co lake (Profile Nam Co 1) and Ganmanong located in northeastern Nam Co lake (Profile Nam Co 2)respectively. According the characteristics of the sediments genesis including the color, texture, structure, moisture, Presents of carbonates, and the roots density and so on, the two section plane are divided in to 12 layers and 9 layers separate. By analyzing some main environment implication factors consist of the grain size composition, total organic carbon(TOC), total inorganic carbon(TIC), total carbon(TC), pH value, electricity conductivity(EC), and water content, the results show that: the genesis degree of Profile Nam Co 1 is much better than that of Profile Nam Co 2; on the bases of aging data, both the two profiles formed from Late Pleistocene and indicated three times coldwarm alternations periods since about 40ka BP.
In this paper, 21 lake sediments samples were collected from Tajiguri situated on the western Nam Co lake (Profile Nam Co 1) and Ganmanong located in northeastern Nam Co lake (Profile Nam Co 2)respectively. According the characteristics of the sediments genesis including the color, texture, structure, moisture, Presents of carbonates, and the roots density and so on, the two section plane are divided in to 12 layers and 9 layers separate. By analyzing some main environment implication factors consist of the grain size composition, total organic carbon(TOC), total inorganic carbon(TIC), total carbon(TC), pH value, electricity conductivity(EC), and water content, the results show that: the genesis degree of Profile Nam Co 1 is much better than that of Profile Nam Co 2; on the bases of aging data, both the two profiles formed from Late Pleistocene and indicated three times coldwarm alternations periods since about 40ka BP.
2009, 27(3): 518-524.
Abstract:
On the basis of field geological investigation in Liulin and Baode in Shanxi province, together with other researcher’s results, the spatial distribution and material composition of Neogene strata were studied. Neogene strata can be divided into three parts in vertical: The bottom is mainly composed of
aqueous deposits, the top is aeolian red clay; the middle part is transitional layer. Further research on Liulin Section reveals the detail characteristics of red clay and aqueous deposits: coarse grain sandstone and gravel cut through red clay, but the fine mudstone parallel to red clay. The character of spatial distribution and material composition of Neogene strata are as follows: the size and thickness of queous deposits is large and thickness of red clay is small near to Luliang Mountain (such as Baode section). The size and thickness of fluvial deposits decrease form Luliang Mountains to Ordos Basin, on the contrary, thickness of red clay increase. Proportional change of red clay and aqueous accumulation transitional layer is the same, which means aqueous deposits wedge red clay base like an asymmetric wedge. The relation between red clay and aqueous accumulation can help us understand the cause of red clay and recover the uplift history of Luliang mountain and paleoclimate evolution.
On the basis of field geological investigation in Liulin and Baode in Shanxi province, together with other researcher’s results, the spatial distribution and material composition of Neogene strata were studied. Neogene strata can be divided into three parts in vertical: The bottom is mainly composed of
aqueous deposits, the top is aeolian red clay; the middle part is transitional layer. Further research on Liulin Section reveals the detail characteristics of red clay and aqueous deposits: coarse grain sandstone and gravel cut through red clay, but the fine mudstone parallel to red clay. The character of spatial distribution and material composition of Neogene strata are as follows: the size and thickness of queous deposits is large and thickness of red clay is small near to Luliang Mountain (such as Baode section). The size and thickness of fluvial deposits decrease form Luliang Mountains to Ordos Basin, on the contrary, thickness of red clay increase. Proportional change of red clay and aqueous accumulation transitional layer is the same, which means aqueous deposits wedge red clay base like an asymmetric wedge. The relation between red clay and aqueous accumulation can help us understand the cause of red clay and recover the uplift history of Luliang mountain and paleoclimate evolution.
2009, 27(3): 529-536.
Abstract:
Fortyfour sediment samples were collected from the Xiangjiang River and its tributary, and its REE concentrations were analyzed using Inductively Coupled PlasmaMass Spectrometry (ICPMS). The total REE concentration(∑REE), lightREE (LREE) and heavyREE concentration (HREE)were 63～387，58.2～353 and 4.8～34 mg·kg1, respectively. In spite of district differences in REE concentrations, the chondritenormalized REE patterns are characterized by LREErich right curves in the suspended matter of all samples. The REE curve normalized by North America shales(NASC) is a horizontal one. REE in suspended matter of Xiangjiang River are controlled by many kinds of factors, probably associated with clay minerals and heavy minerals. The chondritenormalized REE patterns in suspended matter of Laodao river displayed positive Eu anomaly, which is distinctly different from North America shales，and its sources and origin need to be further studied in the future.
Fortyfour sediment samples were collected from the Xiangjiang River and its tributary, and its REE concentrations were analyzed using Inductively Coupled PlasmaMass Spectrometry (ICPMS). The total REE concentration(∑REE), lightREE (LREE) and heavyREE concentration (HREE)were 63～387，58.2～353 and 4.8～34 mg·kg1, respectively. In spite of district differences in REE concentrations, the chondritenormalized REE patterns are characterized by LREErich right curves in the suspended matter of all samples. The REE curve normalized by North America shales(NASC) is a horizontal one. REE in suspended matter of Xiangjiang River are controlled by many kinds of factors, probably associated with clay minerals and heavy minerals. The chondritenormalized REE patterns in suspended matter of Laodao river displayed positive Eu anomaly, which is distinctly different from North America shales，and its sources and origin need to be further studied in the future.
2009, 27(3): 537-545.
Abstract:
Based on quantitative modeling and experimental data on ntetracosane cracking to generate gaseous hydrocarbons in a confined system, we calculated the generation kinetics and carbon isotope kinetics of methane, ethane and propane and determined the main controlling factors influencing the variation of δ13C2 and δ13C3. The carbon isotope of gaseous hydrocarbons from nC24 cracking to gas are comparable to those from crude oil reported recently, and they can be used to investigate the geochemical characteristics of crude oil cracking to gas under geological conditions. The geological model of nC24 cracking suggests it is stable at 150～160℃ and its cracking temperature ranges 180℃ to 200℃, consistent with geological models of crude oil cracking currently reported. With increasing degree of thermal stress, the changes in δ13C2 and δ13C3 are larger than that of δ13C1. It is shown that isotope accumulation controlled by the recharging history of a reservoir has a considerable impact on the carbon isotope distribution of natural gas. Compared to that of cumulative gas, the carbon isotope ratio of partly accumulation gas is heavier and influences the fractionation of the δ13C2 and δ13C3 curves to a greater extent. The geological model of nC24 cracking to gas has been used to interpret the origin of carbon isotopic variation of natural gas in some reservoirs in the Tarim basin.
Based on quantitative modeling and experimental data on ntetracosane cracking to generate gaseous hydrocarbons in a confined system, we calculated the generation kinetics and carbon isotope kinetics of methane, ethane and propane and determined the main controlling factors influencing the variation of δ13C2 and δ13C3. The carbon isotope of gaseous hydrocarbons from nC24 cracking to gas are comparable to those from crude oil reported recently, and they can be used to investigate the geochemical characteristics of crude oil cracking to gas under geological conditions. The geological model of nC24 cracking suggests it is stable at 150～160℃ and its cracking temperature ranges 180℃ to 200℃, consistent with geological models of crude oil cracking currently reported. With increasing degree of thermal stress, the changes in δ13C2 and δ13C3 are larger than that of δ13C1. It is shown that isotope accumulation controlled by the recharging history of a reservoir has a considerable impact on the carbon isotope distribution of natural gas. Compared to that of cumulative gas, the carbon isotope ratio of partly accumulation gas is heavier and influences the fractionation of the δ13C2 and δ13C3 curves to a greater extent. The geological model of nC24 cracking to gas has been used to interpret the origin of carbon isotopic variation of natural gas in some reservoirs in the Tarim basin.
2009, 27(3): 551-557.
Abstract:
By the calculation of gas diffusion amount of 41 large and medium gas fields in china and statistics of their geological reserves, gasbearing area and formation period, gas diffusion rate, gas accumulation rate and the ratio of gas accumulation and diffusion rate were studied. It was considered that gas diffusion rate of 41 large and medium gas fields in China 0.2×106 m3/km2Ma to 49.5×106 m3/km2Ma, average 7.2×106 m3/km2Ma. Gas accumulation rate is 2.1×106 m3/km2Ma to 528.1×106 m3/km2Ma, average 79.4×106 m3/km2Ma. The ratio of gas accumulation and diffusion rate is 1.5 to 94.2, average 14.5. By the study of the relation between reserves abundance and ratio of gas accumulation and diffusion rate of 41 large and medium gas fields in China, it was considered that they have proportional relation. The greater the ratio of gas accumulation and diffusion rate is, the greater the reserves abundance of large and medium gas fields is, conversely the lower. The ratio of gas accumulation and diffusion rate for the formation of large and medium gas fields with high reserves abundance should be at least greater than 4.1. The ratio of gas accumulation and diffusion rate for the formation of large and medium gas fields with medium reserves abundance should be at least between 4.1 and 2.3. The ratio of gas accumulation and diffusion rate for the formation of large and medium gas fields with low reserves abundance should be at least lower than 2.3.
By the calculation of gas diffusion amount of 41 large and medium gas fields in china and statistics of their geological reserves, gasbearing area and formation period, gas diffusion rate, gas accumulation rate and the ratio of gas accumulation and diffusion rate were studied. It was considered that gas diffusion rate of 41 large and medium gas fields in China 0.2×106 m3/km2Ma to 49.5×106 m3/km2Ma, average 7.2×106 m3/km2Ma. Gas accumulation rate is 2.1×106 m3/km2Ma to 528.1×106 m3/km2Ma, average 79.4×106 m3/km2Ma. The ratio of gas accumulation and diffusion rate is 1.5 to 94.2, average 14.5. By the study of the relation between reserves abundance and ratio of gas accumulation and diffusion rate of 41 large and medium gas fields in China, it was considered that they have proportional relation. The greater the ratio of gas accumulation and diffusion rate is, the greater the reserves abundance of large and medium gas fields is, conversely the lower. The ratio of gas accumulation and diffusion rate for the formation of large and medium gas fields with high reserves abundance should be at least greater than 4.1. The ratio of gas accumulation and diffusion rate for the formation of large and medium gas fields with medium reserves abundance should be at least between 4.1 and 2.3. The ratio of gas accumulation and diffusion rate for the formation of large and medium gas fields with low reserves abundance should be at least lower than 2.3.
2009, 27(3): 567-573.
Abstract:
Based on the anatomizing and analysis of controlling factors of the ramptype lithologic reservoir in the hinterland of Junggar basin, reservoir formation model is established preliminarily. According to the composing factors of reservoir formation, the model is named as faciesfault control type of ramp farsource model. This reservoir formation model is controlled by structural background, composition and distribution of sedimentary system, superimposition and cause of formation of sand body, oil source fault, and so on. In addition, the author gave the suggestions for oil and gas exploration in the hinterland of Junggar basin.
Based on the anatomizing and analysis of controlling factors of the ramptype lithologic reservoir in the hinterland of Junggar basin, reservoir formation model is established preliminarily. According to the composing factors of reservoir formation, the model is named as faciesfault control type of ramp farsource model. This reservoir formation model is controlled by structural background, composition and distribution of sedimentary system, superimposition and cause of formation of sand body, oil source fault, and so on. In addition, the author gave the suggestions for oil and gas exploration in the hinterland of Junggar basin.
2009, 27(3): 390-404.
Abstract:
In recent years, deeply buried and high quality reefbank facies reservoirs have been discovered in the Changxing and Feixianguan Formation in the northeast of Sichuan Basin and the Lianglitage Formation of Tazhong area in the Tarim Basin has brought the hope for the oilgas exploration in deep marine facies carbonate strata. Although this reef beach body distribution range is broad, the reservoir quality is good, the proving oil gas reserves are big, but these two basin's reef beach body reservoir actually has the big difference. The reservoir thick of the reefbank facies reservoir in the northeast of Sichuan Basin is bigger, the porosity and permeability is better than the reservoir of Tazhong, and the lithologic character of the former is dolomite, the latter is limestone. The comparison research of the two areas discovered that the difference is controlled in the following factors: The high energy sedimentary environment and eustatic sea level change have the decisive control on the thickness and poroperm capability of reservoir; the gypsum can affect the dolomite occurrence to a certain extent, improve the poroperm capability of reservoir; the hydrocarbon charge time, the reservoir burial evolution, as well as hydrocarbonfluidrock interaction and so on have obvious control on the formation and preservation of the secondary pore, hole and fracture. Because in the northeast of Sichuan Basin when the reefbank body is growing, the eustatic sea level change is comparatively steady and the water energy is very high, are advantages to grow thick and clean reefflat body; dolomite is more, recrystallization is common; hydrocarbon is early charge , the reservoir fast bury deeply at the front and in uplift at last, these are advantages to grow the second porosity, so the storage quality of reefbank reservoir in the northeast of Sichuan Basin is better than Tazhong area.
In recent years, deeply buried and high quality reefbank facies reservoirs have been discovered in the Changxing and Feixianguan Formation in the northeast of Sichuan Basin and the Lianglitage Formation of Tazhong area in the Tarim Basin has brought the hope for the oilgas exploration in deep marine facies carbonate strata. Although this reef beach body distribution range is broad, the reservoir quality is good, the proving oil gas reserves are big, but these two basin's reef beach body reservoir actually has the big difference. The reservoir thick of the reefbank facies reservoir in the northeast of Sichuan Basin is bigger, the porosity and permeability is better than the reservoir of Tazhong, and the lithologic character of the former is dolomite, the latter is limestone. The comparison research of the two areas discovered that the difference is controlled in the following factors: The high energy sedimentary environment and eustatic sea level change have the decisive control on the thickness and poroperm capability of reservoir; the gypsum can affect the dolomite occurrence to a certain extent, improve the poroperm capability of reservoir; the hydrocarbon charge time, the reservoir burial evolution, as well as hydrocarbonfluidrock interaction and so on have obvious control on the formation and preservation of the secondary pore, hole and fracture. Because in the northeast of Sichuan Basin when the reefbank body is growing, the eustatic sea level change is comparatively steady and the water energy is very high, are advantages to grow thick and clean reefflat body; dolomite is more, recrystallization is common; hydrocarbon is early charge , the reservoir fast bury deeply at the front and in uplift at last, these are advantages to grow the second porosity, so the storage quality of reefbank reservoir in the northeast of Sichuan Basin is better than Tazhong area.
2009, 27(3): 410-418.
Abstract:
Microscopic characteristics of the reservoir from the start, through a variety of experiments that: Cretaceous Bashijiqike sandstone carbonate debris of Kuqa DepressionTabei uplift in Tarim Basin have five major characteristics of clear distinction with cement : Coarse grain size, generally around than the original porosity, and a good grinding round (individual phenomenon of the late pressure solution), the clear outline and a relatively homogeneous distribution in the sand, nonblock classes; debris in the presence of fossils and more to finegrained powder; cements (iron calcite, dolomite iron) and more attached to the brink of debris while there was increased, there were significant changes in limestone, carbonate debris show orange under cathodeluminescence. Carbonate rock debris distribution near the source have the characteristics of coarsegrained, low content, poor separation, poor grinding park, poor homogeneity, while the other far from the source have the characteristics of much fine particle size, high content, good separation, good grinding park, and good homogeneity, shallowshaped tablets, and buried the characteristics of strong pressure solution. The ancient source of carbonate rock formation, drought, heat, nearly salt for the ancient climate and water environment, near the source of the rapid accumulation of ancient geography is the main cause of carbonate debris. Carbonate rock debris of identification and quantification have the importance of geological significance：its effect was significantly lower than that hole by cement, which can effectively explain the causes of high porosity sandstone with high content carbonate , and define the distribution of sediment source area as an effective evidence.
Microscopic characteristics of the reservoir from the start, through a variety of experiments that: Cretaceous Bashijiqike sandstone carbonate debris of Kuqa DepressionTabei uplift in Tarim Basin have five major characteristics of clear distinction with cement : Coarse grain size, generally around than the original porosity, and a good grinding round (individual phenomenon of the late pressure solution), the clear outline and a relatively homogeneous distribution in the sand, nonblock classes; debris in the presence of fossils and more to finegrained powder; cements (iron calcite, dolomite iron) and more attached to the brink of debris while there was increased, there were significant changes in limestone, carbonate debris show orange under cathodeluminescence. Carbonate rock debris distribution near the source have the characteristics of coarsegrained, low content, poor separation, poor grinding park, poor homogeneity, while the other far from the source have the characteristics of much fine particle size, high content, good separation, good grinding park, and good homogeneity, shallowshaped tablets, and buried the characteristics of strong pressure solution. The ancient source of carbonate rock formation, drought, heat, nearly salt for the ancient climate and water environment, near the source of the rapid accumulation of ancient geography is the main cause of carbonate debris. Carbonate rock debris of identification and quantification have the importance of geological significance：its effect was significantly lower than that hole by cement, which can effectively explain the causes of high porosity sandstone with high content carbonate , and define the distribution of sediment source area as an effective evidence.
2009, 27(3): 427-434.
Abstract:
There are lots of trace fossils preserved in the Lower Triassic Daye Formation in Huaxi area of Guiyang. Eighteen ichnogenera have been found in this region: Beaconichnus，Circulichnis, Cosmorhaphe, Dendrohaphe, Glockerichnus, Gyrochorte, Gordia, Maeandropolydora, Micatuba, Mammillichnis, Megagrapton, Planolites, Palaeophycus, Phycodes, Phycosiphon, Rhizocorallium, Thalassinoides and Undichna. Some trace fossils have been found for the first time, and they are Circulichnis, Glockerichnus, Maeandropolydora. Three ichnofabrics have been found in Daye Formation, including: Phycodes ichnofabric, PhycosiphonMammillichnis ichnofabric and Thalassinoides ichnofabric. Based on the relative abundance of the ichnogenera in Daye Formation, four ichnofacies have been distinguished: Cruziana ichnofacies of the first and third member, Zoophycos ichnofacies and Nereites ichnofacies of the second member. Combined with the analysis on ichnofabrics, the ichnofacies research shows that the study area located the front line of carbonate platform slope margin, and reflected less energy and anoxia environment. Phycodes ichnofabric and Thalassinoides ichnofabric can be assigned to Cruziana ichnofacies, PhycosiphonMammillichnis ichnofabric can be assigned to Zoophycos ichnofaciesNereites ichnofacies.
There are lots of trace fossils preserved in the Lower Triassic Daye Formation in Huaxi area of Guiyang. Eighteen ichnogenera have been found in this region: Beaconichnus，Circulichnis, Cosmorhaphe, Dendrohaphe, Glockerichnus, Gyrochorte, Gordia, Maeandropolydora, Micatuba, Mammillichnis, Megagrapton, Planolites, Palaeophycus, Phycodes, Phycosiphon, Rhizocorallium, Thalassinoides and Undichna. Some trace fossils have been found for the first time, and they are Circulichnis, Glockerichnus, Maeandropolydora. Three ichnofabrics have been found in Daye Formation, including: Phycodes ichnofabric, PhycosiphonMammillichnis ichnofabric and Thalassinoides ichnofabric. Based on the relative abundance of the ichnogenera in Daye Formation, four ichnofacies have been distinguished: Cruziana ichnofacies of the first and third member, Zoophycos ichnofacies and Nereites ichnofacies of the second member. Combined with the analysis on ichnofabrics, the ichnofacies research shows that the study area located the front line of carbonate platform slope margin, and reflected less energy and anoxia environment. Phycodes ichnofabric and Thalassinoides ichnofabric can be assigned to Cruziana ichnofacies, PhycosiphonMammillichnis ichnofabric can be assigned to Zoophycos ichnofaciesNereites ichnofacies.
2009, 27(3): 443-451.
Abstract:
The studied area is located in the middle part of Yishan slope in Ordos basin, and Chang 6 is the main target oillayer. Understanding the sedimentary microfacies and the relationship between sedimentary microfacies and oilgas distribution is of guiding importance to oil and gas exploration and development. By analyzing the data of drilling cores, logging, image granularities as well as casting thin sections, it can be concluded that delta front subfacies is the main sedimentary subfacies of Chang 6, which includes 6 kinds of microfacies including underwater distributary channel, river mouth bar, interdistributary bay, sheet sandstones, underwater burst fan and natural levee. The distribution of sedimentary microfacies is analysed also. Furthermore, quantitative statistics was used in the analysis of it's oilbearing properties of sedimentary microfacies in oilbearing bodies. The study shows that the oil in Chang 6 mainly developed in the underwater distributary channel sand and combined sand from the underwater distributary channel and river mouth bar, and Chang 61 is the main oilbearing layer, which is the main target of oil and gas exploration.
The studied area is located in the middle part of Yishan slope in Ordos basin, and Chang 6 is the main target oillayer. Understanding the sedimentary microfacies and the relationship between sedimentary microfacies and oilgas distribution is of guiding importance to oil and gas exploration and development. By analyzing the data of drilling cores, logging, image granularities as well as casting thin sections, it can be concluded that delta front subfacies is the main sedimentary subfacies of Chang 6, which includes 6 kinds of microfacies including underwater distributary channel, river mouth bar, interdistributary bay, sheet sandstones, underwater burst fan and natural levee. The distribution of sedimentary microfacies is analysed also. Furthermore, quantitative statistics was used in the analysis of it's oilbearing properties of sedimentary microfacies in oilbearing bodies. The study shows that the oil in Chang 6 mainly developed in the underwater distributary channel sand and combined sand from the underwater distributary channel and river mouth bar, and Chang 61 is the main oilbearing layer, which is the main target of oil and gas exploration.
2009, 27(3): 458-469.
Abstract:
In application to highresolution sequence stratigraphy principles and methods, forty one shortterm baselevel cycles and seven middleterm baselevel cycles and two longterm baselevel semicycles in Fuyu oil layer of Chao 1 Chao gas 3 blocks of Chaoyanggou oil field are identified. By the sedimentary dynamics analysis of genesis of multiage baselevel cycles, quantitative analysis of the core testing and statistical data which characterize the macroscopic heterogeneity of the reservoir, we point out that with the uprising of the longterm baselevel cycle, inlayer heterogeneity of shortterm baselevel cycles becomes stronger, and interlayer heterogeneity of middleterm baselevel cycles becomes weaker, and plane heterogeneity of shortterm baselevel cycles becomes stronger. With the subsiding of the longterm baselevel cycle, every trend is contrary. By analysis, the changes of sedimentary environment that are caused by the changes of baselevel cycles and associated accommodation are the determinative factors for feature differences of reservoir macroscopic heterogeneity.
In application to highresolution sequence stratigraphy principles and methods, forty one shortterm baselevel cycles and seven middleterm baselevel cycles and two longterm baselevel semicycles in Fuyu oil layer of Chao 1 Chao gas 3 blocks of Chaoyanggou oil field are identified. By the sedimentary dynamics analysis of genesis of multiage baselevel cycles, quantitative analysis of the core testing and statistical data which characterize the macroscopic heterogeneity of the reservoir, we point out that with the uprising of the longterm baselevel cycle, inlayer heterogeneity of shortterm baselevel cycles becomes stronger, and interlayer heterogeneity of middleterm baselevel cycles becomes weaker, and plane heterogeneity of shortterm baselevel cycles becomes stronger. With the subsiding of the longterm baselevel cycle, every trend is contrary. By analysis, the changes of sedimentary environment that are caused by the changes of baselevel cycles and associated accommodation are the determinative factors for feature differences of reservoir macroscopic heterogeneity.
2009, 27(3): 479-486.
Abstract:
The shrinkage stage is an important part of basin evolution.The research actuality about the sequence stratigraphy of rift basin among faulting stage, depression stage and shrinkage stage shows that there is very little systematic research about the sequence stratigraphy during shrinkage stage, and there is vague understanding of its sequence boundary, structure, and main control factors. In the view of this problem, we carried out a systematic research about the sequence stratigraphy in Sifangtai formation and Mingshui formation which correspond to the shrinkage stage in Songliao basin. One supersequence was defined by two regional unconformities, and it can be divided into six sequences. The comparison and analysis on the geologic feature between depression stage and shrinkage stage in Songliao Basin shows that it is a shallow lake with smooth topography, and its representative characteristics are lowamplitude structure, low accommodation space, frequently up and down of base level, and so on. The representative characteristics of sequence boundary are gentle angular unconformity, lowangle onlap and transfer surface between ascending and falling. The sedimentary facies of this region contain meandering river, meandering river delta, braid river delta, lakes and so on. In their sequence structure, they were divided into two system tract: transgressive system tract and regressive system tract. There is no obvious incised valley in basin margin and few sublacustrine fan was found. Sands are mainly in the transgressive system tract. Because of stable structural setting, sequences were controlled mainly by palaeoclimate and palaeotopography.
The shrinkage stage is an important part of basin evolution.The research actuality about the sequence stratigraphy of rift basin among faulting stage, depression stage and shrinkage stage shows that there is very little systematic research about the sequence stratigraphy during shrinkage stage, and there is vague understanding of its sequence boundary, structure, and main control factors. In the view of this problem, we carried out a systematic research about the sequence stratigraphy in Sifangtai formation and Mingshui formation which correspond to the shrinkage stage in Songliao basin. One supersequence was defined by two regional unconformities, and it can be divided into six sequences. The comparison and analysis on the geologic feature between depression stage and shrinkage stage in Songliao Basin shows that it is a shallow lake with smooth topography, and its representative characteristics are lowamplitude structure, low accommodation space, frequently up and down of base level, and so on. The representative characteristics of sequence boundary are gentle angular unconformity, lowangle onlap and transfer surface between ascending and falling. The sedimentary facies of this region contain meandering river, meandering river delta, braid river delta, lakes and so on. In their sequence structure, they were divided into two system tract: transgressive system tract and regressive system tract. There is no obvious incised valley in basin margin and few sublacustrine fan was found. Sands are mainly in the transgressive system tract. Because of stable structural setting, sequences were controlled mainly by palaeoclimate and palaeotopography.
2009, 27(3): 494-502.
Abstract:
By analyzing Permian structural sequence, sedimentation and faults characteristics, the author thinks that Wuxia area was a peripheral foreland restricted by nappe in Permian, there mainly developed submarine fans, fan deltas, fluvial fans and lakes, from under to upside, experienced deep sea stage, flysch stage and molasse stage, among which fans acted as typical lithosomic bodies. At the same time, structural evolution experienced intense divingcollision orogenesis stage, weakly compress occlude instant extend stage and revived strong thrusted stage, generating many thrusting reverse faults to influence sedimentation and denudation and control formation and evolution of fault belt. It is showed that the Permian is characterized by a model of forward thrusting movement and gradual advance migration of fan bodies. That is to say, with the forward thrusting movement of synsedimentary faults controlling the fans from mountainous region to the edge of the Junggar basin, fan bodies distributed in all fault belts gradually developed and advanced from the edge to the center of the Junggar basin and the fan bodies became larger, showing an obvious sedimentary response of gradual advance migration. There is an excellent coupling between them, so faults activity can be looked upon as main factor in controlling sedimentation in Wuxia area.
By analyzing Permian structural sequence, sedimentation and faults characteristics, the author thinks that Wuxia area was a peripheral foreland restricted by nappe in Permian, there mainly developed submarine fans, fan deltas, fluvial fans and lakes, from under to upside, experienced deep sea stage, flysch stage and molasse stage, among which fans acted as typical lithosomic bodies. At the same time, structural evolution experienced intense divingcollision orogenesis stage, weakly compress occlude instant extend stage and revived strong thrusted stage, generating many thrusting reverse faults to influence sedimentation and denudation and control formation and evolution of fault belt. It is showed that the Permian is characterized by a model of forward thrusting movement and gradual advance migration of fan bodies. That is to say, with the forward thrusting movement of synsedimentary faults controlling the fans from mountainous region to the edge of the Junggar basin, fan bodies distributed in all fault belts gradually developed and advanced from the edge to the center of the Junggar basin and the fan bodies became larger, showing an obvious sedimentary response of gradual advance migration. There is an excellent coupling between them, so faults activity can be looked upon as main factor in controlling sedimentation in Wuxia area.
2009, 27(3): 511-516.
Abstract:
Flood and ebb channel are the important geomorphologic units and different hydrodynamic properties exist in these channels. Based on the analysis of particle size, clay and heavy mineral and magnetic features of the sediments in the flood and ebb channels of the Changjiang Estuary, it is found that there are different sedimentary features in the flood and ebb channels. Particle sizes of the sediments in the flood channel are coarser than that in the ebb channel. Distribution and concentrations of clay minerals in the flood channel sediment are similar with those in the ebb channel due to the dualdirection currents. Concentration of heavy minerals in the ebb channel is higher than that in the flood channel because there is strong ebb tide current and similarly there are more ferrimagnetic mineral in the ebb channel.
Flood and ebb channel are the important geomorphologic units and different hydrodynamic properties exist in these channels. Based on the analysis of particle size, clay and heavy mineral and magnetic features of the sediments in the flood and ebb channels of the Changjiang Estuary, it is found that there are different sedimentary features in the flood and ebb channels. Particle sizes of the sediments in the flood channel are coarser than that in the ebb channel. Distribution and concentrations of clay minerals in the flood channel sediment are similar with those in the ebb channel due to the dualdirection currents. Concentration of heavy minerals in the ebb channel is higher than that in the flood channel because there is strong ebb tide current and similarly there are more ferrimagnetic mineral in the ebb channel.
2009, 27(3): 525-528.
Abstract:
αcellulose, as an important component of organic matter from lake sediments, has been paid much attention by paleoclimate researchers, and especially its isotopes have been extensively utilized to reconstruct paleoclimate and paleoenvironment. Recently, the limited application of stable isotope of cellulose is attributed to difficulty to extract pure cellulose from lake sediments, and the established experimental procedure of cellulose extraction is very complicated. Based on repeated experiments, an effective four processes to extract cellulose is established, including alkalinewashing by 5% NaOH, acidwashing by 5%HCl, bleaching by glacial acetic acid and sodium chlorite and alkalinewashing by 17.5% NaOH. The result of infrared spectrum shows that spectrogram is consistent with standard αcellulose. Furthermore, in order to testify the result, compare with the preestablished method about stable carbon and oxygen isotope, which indicates this procedure is proved to be simple and feasible.
αcellulose, as an important component of organic matter from lake sediments, has been paid much attention by paleoclimate researchers, and especially its isotopes have been extensively utilized to reconstruct paleoclimate and paleoenvironment. Recently, the limited application of stable isotope of cellulose is attributed to difficulty to extract pure cellulose from lake sediments, and the established experimental procedure of cellulose extraction is very complicated. Based on repeated experiments, an effective four processes to extract cellulose is established, including alkalinewashing by 5% NaOH, acidwashing by 5%HCl, bleaching by glacial acetic acid and sodium chlorite and alkalinewashing by 17.5% NaOH. The result of infrared spectrum shows that spectrogram is consistent with standard αcellulose. Furthermore, in order to testify the result, compare with the preestablished method about stable carbon and oxygen isotope, which indicates this procedure is proved to be simple and feasible.
2009, 27(3): 546-550.
Abstract:
Hydrocarbon generation kinetics simulation was carried out to planktonnic algae and benthic algae , with the thermal simulation and element composition analysis ,the results show that planktonic algae and benthic algae are characterized by high abundance of N,S,O atoms and low hydrocarbon activation energy .Average activation energy is about 220 kJ/mol; and the activation energy of the beginning of hydrocarbon generation is less than 184 kJ/mol; the activation energy is respectively 251 kJ/mol and 255 kJ/mol to reach 90% hydrocarbon generation ratio; and generate great abundance of hydrocarbon when they are still immature. However, the period of hydrocarbon generation of planktonnic algae and benthic algae is very long ,the span of activation energy in the period of 10% to 90% kerogen transformation ratio are respectively 59 kJ/mol and 71 kJ/mol; the span of temperature are respectively 166.8 ℃and 201.2 ℃. The planktonnic algae would generate hydrocarbon much more quickly than benthic algae, the carbon conversion ratio of hydrocarbon generation of planktonic algae and benthic algae is respectively 61.77% and 34.9%.The products of hydrocarbon generation are main asphaltene and resin. Planktonnic algae and benthic algae are the main source of immature and lowmature oil.
Hydrocarbon generation kinetics simulation was carried out to planktonnic algae and benthic algae , with the thermal simulation and element composition analysis ,the results show that planktonic algae and benthic algae are characterized by high abundance of N,S,O atoms and low hydrocarbon activation energy .Average activation energy is about 220 kJ/mol; and the activation energy of the beginning of hydrocarbon generation is less than 184 kJ/mol; the activation energy is respectively 251 kJ/mol and 255 kJ/mol to reach 90% hydrocarbon generation ratio; and generate great abundance of hydrocarbon when they are still immature. However, the period of hydrocarbon generation of planktonnic algae and benthic algae is very long ,the span of activation energy in the period of 10% to 90% kerogen transformation ratio are respectively 59 kJ/mol and 71 kJ/mol; the span of temperature are respectively 166.8 ℃and 201.2 ℃. The planktonnic algae would generate hydrocarbon much more quickly than benthic algae, the carbon conversion ratio of hydrocarbon generation of planktonic algae and benthic algae is respectively 61.77% and 34.9%.The products of hydrocarbon generation are main asphaltene and resin. Planktonnic algae and benthic algae are the main source of immature and lowmature oil.
2009, 27(3): 558-566.
Abstract:
There is abundant oil and gas in F,Y Formation of Sanzhao depression in Songliao Basin, how to further enlarge reservoir area and how to exploit proven territory are two problem puzzling explorer because of the complexity of reversed migration. The distinctiveness of accumulation of F,Y Formation are manifested in two aspects: first, higher density fault, smaller scale and concentrated in zone; second, it's difficult to forecast distribution of the fluvial channel sand since F,Y Formation located in convergence of provenance. This paper based on the correlation of oil and gas, centering on the formation and evolution of fault, oil source fault is calibrated, the allocation of fault and sand body and regulation of controlling oil has been analyzed and the accumulation model is established. It's considered that the oil of F, Y Formation mainly comes from the hydrocarbon source rock of K1qn, the key period of accumulation is last sediment stage of K2m, consequently, the main oil source faults are those among the periods of fault depression to depression and depression to inversion, reversed migration happened along the oil source fault under the action of overpressure, the depth downward is usually 200m, so the favorable formation of interest is the top of F,Y Formation. Faults in F,Y Formation is featured by concentration in zone, oil source faults , the ones controlling accumulation, are mainly the boundary faults. The force condition of "reversed migration", namely, oil along oil source faults, multiple phases of deformation of faults and transportation of horizontal fracture caused by the decoupling of mudstone of K1qn in reversed period determined the concentration of oil in footwall channel sand of fault, oil in horst controlled by oil source fault is highly concentrated, whereas the concentration zone of fault which is the lower tectonic place is not concentration area of oil.
There is abundant oil and gas in F,Y Formation of Sanzhao depression in Songliao Basin, how to further enlarge reservoir area and how to exploit proven territory are two problem puzzling explorer because of the complexity of reversed migration. The distinctiveness of accumulation of F,Y Formation are manifested in two aspects: first, higher density fault, smaller scale and concentrated in zone; second, it's difficult to forecast distribution of the fluvial channel sand since F,Y Formation located in convergence of provenance. This paper based on the correlation of oil and gas, centering on the formation and evolution of fault, oil source fault is calibrated, the allocation of fault and sand body and regulation of controlling oil has been analyzed and the accumulation model is established. It's considered that the oil of F, Y Formation mainly comes from the hydrocarbon source rock of K1qn, the key period of accumulation is last sediment stage of K2m, consequently, the main oil source faults are those among the periods of fault depression to depression and depression to inversion, reversed migration happened along the oil source fault under the action of overpressure, the depth downward is usually 200m, so the favorable formation of interest is the top of F,Y Formation. Faults in F,Y Formation is featured by concentration in zone, oil source faults , the ones controlling accumulation, are mainly the boundary faults. The force condition of "reversed migration", namely, oil along oil source faults, multiple phases of deformation of faults and transportation of horizontal fracture caused by the decoupling of mudstone of K1qn in reversed period determined the concentration of oil in footwall channel sand of fault, oil in horst controlled by oil source fault is highly concentrated, whereas the concentration zone of fault which is the lower tectonic place is not concentration area of oil.
