摘要
四川盆地绵阳-长宁拉张槽及周缘沉积了巨厚的筇竹寺组黑色页岩,是未来深层页岩气勘探的有利目标。以拉张槽中段及周缘筇竹寺组富有机质页岩裂缝脉体中赋存的古流体为研究对象,基于岩心和薄片观察了裂缝脉体的发育特征,通过碳氧同位素测试分析了古流体的来源及成因,利用盆地数值模拟恢复了地层压力演化过程,进而探讨了筇竹寺组页岩气的保存条件。结果显示:绵阳-长宁拉张槽内的GS17井和拉张槽东侧的MX9井筇竹寺组页岩裂缝脉体相对不发育,拉张槽西侧W201井发育多组顺层缝和高角度裂缝,被早期方解石和晚期鞍状白云石、重晶石、石英等矿物充填;碳氧同位素结果表明成脉流体与热液和有机质脱羧作用有关;拉张槽内及东侧高石梯-磨溪地区筇竹寺组由于原油裂解发育强超压并保存至今,而拉张槽西侧的威远构造虽然也曾经发育过超压,但在晚期构造运动中发生了泄压作用。相较于拉张槽内和高石梯-磨溪地区,威远地区筇竹寺组页岩气的晚期保存条件相对苛刻,需要重点关注局部超压发育区。
Huge and thick black shale was deposited in the Mianyang-Changning intracratonic sag of the Sichuan Basin,which is a favorable target for shale gas exploration in the future.Taking the paleofluid preserved in the Qiongzhusi Formation shale as the research object,based on the petrological and optical characteristics of fracture veins observed in cores and thin sections,the source and origin of the paleofluid were analyzed by carbon and oxygen isotope testing,the formation pressure evolution of shale gas was simulated by using BasinMod software,and the preservation conditions of Qiongzhusi Formation shale gas in the central portion and surrounding areas of the Mianyang-Changning intracratonic sag were discussed.The results show that fracture vein rarely appears in the Qiongzhusi Formation shale of wells GS17 and MX9.While multiple groups of bed-parallel and high-angle fractures appear in Well W201,which are filled with mesocrystalline to coarse crystalline calcite,fibrous calcite,saddle dolomite,barite,and quartz.Carbon and oxygen isotopes indicate that fracture veins were generated by fluids of hydrothermal solution or organic matter decarboxylation.Hydrocarbon generation,particularly the crude oil cracking,induced the strong overpressure in the Qiongzhusi Formation of the intracratonic sag and the Gaoshiti-Moxi area,and the overpressure has been preserved thus far.Although overpressure was also developed in the Weiyuan structure,it dissipated in the late tectonic movement.Compared with the intracratonic sag and Gaoshiti-Moxi area,the late preservation conditions of shale gas in the Weiyuan area were relatively harsh,but some local overpressure areas need to be focused on.
作者
陈丽清
吴娟
何一凡
蒋前前
吴伟
罗超
杜国正
Chen Liqing;Wu Juan;He Yifan;Jiang Qianqian;Wu Wei;Luo Chao;Du Guozheng(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;College of Energy,Chengdu University of Technology,Chengdu 610059,China;Shale Gas Evaluation and Exploitation Key Laboratory of Sichuan Province,Chengdu 610051,China;Shale Gas Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu 610051,China)
出处
《地质科技通报》
CAS
CSCD
北大核心
2023年第3期142-152,共11页
Bulletin of Geological Science and Technology
基金
国家自然科学基金青年科学基金项目(41502134)
四川省科技厅应用基础项目(2018JY0437)。
关键词
拉张槽
筇竹寺组
页岩气
裂缝脉体
地层压力
古流体
intracratonic sag
Qiongzhusi Formation
shale gas
fracture vein
formation pressure
paleofluid
