鄂尔多斯盆地上古生界致密砂岩气成岩、成藏耦合机理研究

The thesis is in view of the tight sandstone gas associating the coal-bearing source rock developing from the middle and western areas in our country, scientifically probed into its availability analysis coupling based on the diagenesis and gas accumulation. It takes the tight sandstone gas from Upper paleozoic in Erdos basin as the research object, with the link of the geochemistry changing of the fluid. ①Analysing the control effect of the much organic acid released from the coal-bearing source rock on the sandstone tightness in the process of the early generating hydrocarbon.Based on the component acquired from the the coal and carbargilite thermal simulation, we conduct acid-soluble tests on the quartz sandstone and lithic sandstone, simulate the precipitation rate of quartz cementation and overgrowth within the geological scale; calculate the amount of the decreasing pore due to the quartz secondary growth and the siliceous cement development, analyze the change of the sandstone pore throat contexture and tightness. ②With kinetic parameters of hydrocarbon generation from the thermal simulation of the source rock, quantitative describing the generating and expulsion quantity under the geology dimension, defining the main gas accumulation period and key time according to the inclusion thermometry and the K-Ar / Ar-Ar dating of illite. ③Discussing the validity of the diagenesis and accumulation coupling in the process of the gas filling and reservoir tightness development. The tight sandstone gas pool is the main domain of the gas long exploration in our country. Researching its forming mechanism and accumulation rule will have a economical value on improving the success rate of the tight sandstone gas exploration.

针对我国中西部地区发育的与煤系烃源岩共生的致密砂岩气，从成岩和成藏两个角度切入对其成藏耦合有效性的科学探讨。以鄂尔多斯盆地上古生界致密砂岩气为研究对象，借助于流体的地球化学变化这条纽带：①剖析煤系烃源岩在早期生烃过程中释放出的大量有机酸对砂岩致密化的控制作用；在煤岩及碳质泥岩热模拟获取的组分基础上，对石英砂岩、岩屑砂岩酸溶实验，石英胶结物及自生加大边进行地质尺度下动力学定量模拟；计算石英次生加大及硅质胶结物发育导致孔隙减少量，分析砂岩孔喉结构与致密性变化；②在烃源岩热模拟实验基础上计算动力学参数，定量刻画地质尺度下的生排烃量，根据包裹体测温及储层伊利石K-Ar/Ar-Ar测年，确定主力成藏期次和关键时间；③探讨天然气充注与储层致密化发育过程中成岩与成藏耦合的时效性。致密砂岩气是我国今后天然气勘探的主要领域，研究其形成机理及富集规律，对于提高致密砂岩气的勘探成功率具有重要经济意义。

致密砂岩气是中国目前开发的主要天然气，对其形成机理的研究具有重大的战略及理论意义。. 借助常规薄片、阴极发光、扫描电镜等实验手段，对鄂尔多斯盆地东部上古生界砂岩储层展开砂岩致密化研究，同时借助于盆地模拟、烃源岩热演化生烃模拟进行有机酸生成模拟，酸溶实验；使用石英沉淀动力学模型展开石英生成量的计算，计算了石英砂岩孔隙衰减量。. 在早成岩阶段（距今220Ma）至晚成岩阶段A期（距今160Ma）为有机酸生成的主要时期。有机酸致使长石、岩屑等无机矿物溶解、石英发生多期次生增生，山西组砂岩受机械压实及强烈的硅质胶结作用,导致孔隙致密化发育。在早成岩阶段结束时，原始孔隙度下降到15.47%。晚成岩阶段A，孔隙降低为6.94%，储层已经致密化，晚成岩阶段B，孔隙进一步降低为5.84%，储层致密化加剧。有机流体充注形成的有机-无机相互作用是导致储层孔隙度的减少，储层致密化发育主要影响因素。.应用流体包裹体、激光拉曼组分、碳同位素分馏动力学及K-Ar同位素测年，精细研究了山西组、石盒子组致密砂岩储层形成过程，探讨了致密砂岩气藏的成岩和成藏的耦合机理。结合埋藏史确定出山西组、下石盒子组含气层系有效成藏时间：135Ma~108Ma，131Ma~89Ma。. 甲烷碳同位素动力分馏的模拟计算结果表明，榆林山23气藏在中侏罗世晚期天然气逐渐充注成藏，在早白世130~97.5Ma时期，气藏经历了阶段聚集，捕获的天然气主要是成熟度Ro为1.5%~2.0%之间生成。早期的烃类充注200~150Ma，此时石英砂岩储层已经向致密化发育，在150Ma，储层已达致密化。第二期烃类气体充注时间为140~100Ma，即早白垩世，后期主力天然气的充注是在储层已致密化的条件下成藏，说明山西组气藏和盒8气藏在成藏早期是边致密，边成藏，成藏后期是先致密后成藏。