川南龙马溪组页岩储层特征及主控因素

以川南长宁页岩气示范区A井页岩气优质产层龙一1小层与非优质产层龙一2小层及龙二段为主要研究对象，从储层矿物组成、纳米孔隙发育特征和赋存载体组合样式及其主控因素等微观层面进行系统对比，进一步明确了两者的差异及相互关系。研究结果显示:1）龙一1小层富含有机质、石英和黄铁矿，页岩孔径分布呈前峰型，纳米孔隙发育主要受TOC含量控制，有机孔是纳米孔隙主要类型，有机质颗粒充填于矿物粒间孔内，被石英和碳酸盐岩等脆性矿物包围，构成“纳米级气藏”；2）龙一2小层和龙二段相对富含黏土矿物和碳酸盐岩，页岩孔径分布以后峰型为主，纳米孔隙发育主要受黏土矿物含量控制，黏土矿物粒间孔/层间孔是纳米孔隙主要类型，黏土矿物颗粒内部充填纳米孔隙不发育的方解石和白云石，对页岩气运移起到有效阻滞。因此，非优质产层龙一2小层和龙二段实际上是下伏优质产层龙一1小层的有效盖层。川南龙马溪组页岩气选区需同时关注龙一1小层的储集能力和龙一2小层与龙二段等上覆地层的封闭能力。

Shale Reservoir Characteristics and Main Controlling Factors of Longmaxi Formation,Southern Sichuan Basin

Comprehensive comparisons of mineral compositions and occurrence and distribution of nanopores were conducted for the productive （L11） and non-productive （L12 and L2） sections of the lower Silurian Longmaxi Formation to clarify their individual geological implications for shale gas exploration and exploitation in southern Sichuan Basin， China. The results show that （1） the L11 section is rich in organic matter， quartz and pyrite. A unimodal pore size distribution was observed in the plots of dV/dlog（D） vs. D， with peaks in the micropore range. The TOC regulates the formation of nanopores， and a significant occurrence of organic matter pores was detected within this section. Organic matter particles fill the interparticle pores of the mineral matrix and are surrounded by brittle minerals （e.g.， quartz and carbonates）， forming nano-gas-reservoirs. （2） The L12 and L2 section is rich in clays and carbonates. A unimodal distribution with peaks in the macropore range was observed in the plots of dV/dlog（D） vs. D. Clays play a major role in the occurrence of nanopores. Pores within/between clay grains and between clay platelets were detected in this section. The porous clay particles are filled and separated by calcite and dolomite， hence blocking gas migration. Therefore， the upper non-productive section is the effective caprock of the lower productive section. More attention should be paid to the reservoir capacity of the L11 section and sealing ability of L12 and L2 of the Longmaxi Formation in the southern Sichuan Basin.