The second member of the Triassic Xujiahe Formation in the Sanhuiba area in Huaying Mountain is an important section of sedimentary delta facies in the Chongqing Tianfu Geological Survey and Training Base. In spite of...The second member of the Triassic Xujiahe Formation in the Sanhuiba area in Huaying Mountain is an important section of sedimentary delta facies in the Chongqing Tianfu Geological Survey and Training Base. In spite of some initial efforts on its lithology and lithofacies, the existing research is yet to be completed and suffers from contradictory conclusions and inadequate evidence. Starting from the sedimentary microfaeies types and cyclic features, we analyzed the vertical sequence of a sedimentary delta model and discovered that this section is a constructional delta deposit. Eight incomplete and asymmetric regressive cycles are marked off, given that frequent erosion surfaces appeared in the section. Based on the analysis of structural characteristics of every monocycle, we summarized the system of cycles, tracts and sequence characteristics of the overall section. In view of this systematic series of cycles, we discussed the features of the syndepositional tectonic movements in the area and conclude that, due to frequent erosion, migration and diversion of a sub-channel branch was brought about by oscillating movements of the crust. In a comparison with neighboring sections, we explored the cause of erosion and the relations between erosion and cycles. This study greatly strengthens existing research and theories, makes an important and comprehensive contribution to geological surveys and training in the area and provides essential suggestions for coal exploration, oil and gas evaluation and in general to exploration and development in the target stratum.展开更多
In the Xinchang area in western Sichuan Basin,a total of 121.12 billion cubic meters of proved reserves of natural gas are discovered in Member 2 of Xujiahe Formation,but only 7.739 billion cubic meters of proved rese...In the Xinchang area in western Sichuan Basin,a total of 121.12 billion cubic meters of proved reserves of natural gas are discovered in Member 2 of Xujiahe Formation,but only 7.739 billion cubic meters of proved reserves of natural gas are produced.The main reason is that sandstones in Member 2 of Xujiahe Formation in the Xinchang area are generally tight,with strong heterogeneity,only intervals with relatively good physical properties have a certain production capacity;therefore,it is very necessary and important to evaluate effective reservoirs in Member 2 of Xujiahe Formation.Through analysis of cores,with consideration of color,sedimentary texture and grain size,lithofacies of Member 2 of Xujiahe Formation in the Xinchang area can be divided into 12 types.According to data of physical properties and thin section analysis,it can be concluded that the favorable lithofacies in the upper submember of Member 2 of Xujiahe Formation are the massive medium-coarse sandstone,the medium-coarse sandstone with cross bedding,and the medium-coarse sandstone with carbonaceous fragments.On the basis of electrical characteristics,well-logging interpretation standards for favorable lithofacies are established,in addition,favorable lithofacies and effective reservoir in the Xinchang area are determined,and distribution of favorable lithofacies(effective reservoir)is identified,which lay a solid foundation for next deployment of appraisal well and development of effective reserves.展开更多
基金provided by the National Natural Science Foundation of China (Nos. 50678182 and 40802001)the Natural Science Foundation of Chongqing City (No.2008 BA0015)the Research Fund for Teaching Reform in Institutes of Higher Learning, Chongqing, China (No.09-3-094)
文摘The second member of the Triassic Xujiahe Formation in the Sanhuiba area in Huaying Mountain is an important section of sedimentary delta facies in the Chongqing Tianfu Geological Survey and Training Base. In spite of some initial efforts on its lithology and lithofacies, the existing research is yet to be completed and suffers from contradictory conclusions and inadequate evidence. Starting from the sedimentary microfaeies types and cyclic features, we analyzed the vertical sequence of a sedimentary delta model and discovered that this section is a constructional delta deposit. Eight incomplete and asymmetric regressive cycles are marked off, given that frequent erosion surfaces appeared in the section. Based on the analysis of structural characteristics of every monocycle, we summarized the system of cycles, tracts and sequence characteristics of the overall section. In view of this systematic series of cycles, we discussed the features of the syndepositional tectonic movements in the area and conclude that, due to frequent erosion, migration and diversion of a sub-channel branch was brought about by oscillating movements of the crust. In a comparison with neighboring sections, we explored the cause of erosion and the relations between erosion and cycles. This study greatly strengthens existing research and theories, makes an important and comprehensive contribution to geological surveys and training in the area and provides essential suggestions for coal exploration, oil and gas evaluation and in general to exploration and development in the target stratum.
基金supported by the Sinopec Scientific Research Project"Gas Reservoir Reserve Evaluation and Development Target Optimization of Xujiahe Formation"(No.:P18089-4).
文摘In the Xinchang area in western Sichuan Basin,a total of 121.12 billion cubic meters of proved reserves of natural gas are discovered in Member 2 of Xujiahe Formation,but only 7.739 billion cubic meters of proved reserves of natural gas are produced.The main reason is that sandstones in Member 2 of Xujiahe Formation in the Xinchang area are generally tight,with strong heterogeneity,only intervals with relatively good physical properties have a certain production capacity;therefore,it is very necessary and important to evaluate effective reservoirs in Member 2 of Xujiahe Formation.Through analysis of cores,with consideration of color,sedimentary texture and grain size,lithofacies of Member 2 of Xujiahe Formation in the Xinchang area can be divided into 12 types.According to data of physical properties and thin section analysis,it can be concluded that the favorable lithofacies in the upper submember of Member 2 of Xujiahe Formation are the massive medium-coarse sandstone,the medium-coarse sandstone with cross bedding,and the medium-coarse sandstone with carbonaceous fragments.On the basis of electrical characteristics,well-logging interpretation standards for favorable lithofacies are established,in addition,favorable lithofacies and effective reservoir in the Xinchang area are determined,and distribution of favorable lithofacies(effective reservoir)is identified,which lay a solid foundation for next deployment of appraisal well and development of effective reserves.
