摘要:
本文以鄂尔多斯盆地东部镇川堡含气区的下二叠统下石盒子组为例,提出对等时沉积序列进行最大熵谱分析的方法,以便寻找各地层序列间的历史成因联系和彼此间的亲疏程度,从而较好地解决了诸如古水流方向、河道形态及湖泊岸线位置等问题,研究结果表明,镇川堡含气区下石盒子组沉积物源来自东北付谷、宝德一带,古水流方向北东30—60°,发育两个河流系统,稳定主河道4条.下石盒子组地层序列最大熵谱分析的最佳滤波阶数m=62,谱跨度K的最佳参数为200.
Abstract:
The ultimate aim of historical sedimentology is to expound characteristics of vertical sequences of the sedimentary records from larger time-space scale and explain its evolution process in time and the distributary pattern in space. That is, historical connection of the sedimentary sequences in time-space evolution would be interpreted. Maximum Entropy Matrix (MEM) anlysis in Mathematics days an important role on this object. It is very clear that the fundamental principle taking the isochronous sedimentary sequences, which have a obvious characteristic of sandstone and mudstone interbed structure, to be undergone MEM anely sis. That is, sandstone sediments of channel deposition which arise random or disorderly and unsystematicly at the sequence contains actually the cyclicity of sub-cyclicity, and it reflects the periodicity of the channel evolution at the time vector. Thus, we can separate the main periodicity (main frequency) of the cyclioty sandstone with MEM analysis and take it as a parameter to determine the relativity of isochronous sedimentary sequences. If the two isochronous sedimentary sequences have the same or similar amoum of main frequency of the channel sandstone arising, the sequences are of relativity in contribution facton of similarity in sedimentary environment. This paper takes Zhenchuanpu gas- bearing area in the east of Eerduosi Basin locates in western . North-China Platform as an example, and put forwards the MEM analysis method to the isochronous sedimentary sequences so as to look for the historical forming relationship in every straligraphic sequences and the close relationship. Thus the paper has relatively well resolved the problems of palaeocurient direction, the form of river channel and the shoreline of lake etc. The study shows that the MEM analysis method of stratigraphic sequences may help petroleum geologists to rebuild llthofacies and palaeogeography using lithic logging sectiones. The study results indicate that the sedimentary provenance of the lower Shihezi Formation of lower Permian System in Zhenchuanpu area is along the northeastern Baode-Fugu, the palaeocurrent direction is 30-60° , and there are two river systems and three stable main channels. When in the optimu filting wave stage m= 62 and spectrum span k = 200. it is optimum to the MEM analysis effect of the stratigraphic sequences of the lower Shihezi Formation. The premise of the relativity correlation of sedimentary sequences is the isochronous character about the boundary of sequences top and bottom. Seismic stratigraphy may satisfactorily resolve this question.
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