页岩储层基质孔隙连通性及其定量评价方法

The pore connectivity of shale matrix has a significant impact on shale gas migration and the long-term gas supply of shale gas wells. However, the investigations on pore connectivity of shale matrix is limited and many questions are still existing, such as the factors controlling pore connectivity of shale matrix is still unknown, the evaluation of pore connectivity of shale matrix is mainly qualitative lacking of quantitative evaluation methods. As a result, many more researches focusing on pore connectivity of shale matrix are required to clarify these questions. Using representative marine and continental shale samples from China, this project will focus on the pore connectivity of shale matrix and develop quantitative evaluation methods. Multiple approaches will be applied to characterize the pore structure of shale and clarify the controlling factors of pore connectivity of shale matrix, including FE-SEM、FIB-SEM、QEMSCAN、N2 adsorption and so on. A new pore structure model of shale matrix will be established to accommodate shale heterogeneity. Spontaneous imbibition and high pressure mercury intrusion porosimetry will be used to quantitatively evaluate the pore connectivity of shale matrix. The outcomes of this project will enrich the evaluation system of shale gas reservoirs and play an important role in searching for potential shale gas reservoirs in China.

页岩储层基质孔隙连通性直接影响页岩气在储层内的运移，从而控制页岩气的长期供气能力。目前页岩储层基质孔隙连通性研究还不够深入，页岩储层基质孔隙连通性主控因素不清，同时缺乏定量化评价方法。项目以我国典型海相和陆相页岩为研究对象，针对页岩储层基质孔隙连通性及其定量评价这一科学问题，利用岩石学和地球化学方法精细刻画页岩储层非均质性特征，采用场发射扫描电镜（FE-SEM）等直接成像法和氮气吸附法等流体注入法表征页岩储层微观孔隙结构，包括孔隙形貌、大小、分布以及连通状态，明确页岩储层基质孔隙连通性主控因素；参照已有孔隙结构简化模型，并结合页岩储层非均质性特征和基质孔隙连通性特征，建立适应页岩非均质性的基质孔隙结构简化模型；利用自发渗吸法和高压压汞法来定量评价页岩储层基质孔隙连通性。成果对于完善页岩储层评价体系及页岩气有利区优选具有重要的意义。

页岩储层基质孔隙连通性影响页岩气在储层内的运移，并最终影响页岩气的长期供气能力。本项目围绕页岩储层基质孔隙连通性这一科学问题，以渝东南地区志留系龙马溪组海相页岩和延安地区三叠系延长组陆相页岩为主要研究对象，并结合美国巴奈特页岩以及川东北地区侏罗系自流井组陆相页岩储层特征开展研究。水自发渗吸斜率和油相自发渗吸斜率可分别用以表征亲水孔隙连通性和亲油孔隙连通性，高压压汞法获得的孔隙曲折度可用来表征页岩储层基质孔隙连通性。结果显示，页岩储层基质亲水孔隙连通性均较差，而龙马溪组海相页岩亲油孔隙连通性与延长组陆相页岩相比明显较好；在镜质体反射率或者等效镜质体反射率为0.8%-3.0%的范围内，随着热成熟度增加，页岩中有机质孔隙发育程度不断增加，而原生无机矿物孔隙则不断减少，同时溶蚀孔的出现也会增加亲油孔隙空间，因此表现出亲水孔隙连通性不断下降，亲油孔隙连通性不断上升的趋势；石英的抗压实作用有利于孔隙空间的保存，特别是有利于亲水无机矿物孔隙的保存，而粘土矿物与流体之间强烈的相互作用会改变页岩储层孔隙结构并对孔隙连通性产生重要的影响；页岩储层富含有机质孔隙，具有亲水和亲油双重孔隙连通网络，据此建立了偏向亲水、混合润湿、偏向亲油三种页岩储层基质孔隙结构简化模型。项目成果对于完善页岩储层评价体系及页岩气有利区优选具有重要的意义。