昭通示范区龙马溪组页岩气高产储层微观孔隙结构定量表征

Quantitative Characterization of Microscopic Pore Structures for the High-Yielding Shale Gas Reservoir of Longmaxi Formation in Zhaotong Demonstration Zone

以昭通示范区龙马溪组页岩气高产储层为研究对象,通过场发射扫描电镜,氮气吸附实验,XRD衍射,核磁共振实验,纳米CT扫描技术和Image J图像处理软件,对页岩气高产储层微观孔隙结构进行定量表征。研究结果表明,页岩气高产储层的岩石类型以富含有机质的灰黑—黑色页岩为主,孔隙度大于2%,渗透率大于0.01×10^(-3)μm^(2),孔隙类型以有机质孔为主,孔隙连通性好,其次为粒间孔,粒内孔和少量微裂缝,孔隙半径分布在5~50 nm之间,三类孔隙结构在孔隙类型,TOC含量和孔径分布方面各有差异,其中Ⅰ类孔隙结构主要为机质孔,TOC含量高,储层质量好。Ⅱ类孔隙有机质含量中等,主要是由有机质和黏土矿物提供的微孔-介孔构成;Ⅲ类孔隙有机质含量低,主要是由黏土矿物提供的部分微孔和介孔构成。

In this study,the high-yielding shale gas reservoir of Longmaxi Formation in Zhaotong Demonstration Zone is addressed.The microscopic pore structures of high-yielding shale gas reservoir were quantitatively characterized by field emission scanning electron microscopy,nitrogen adsorption experiment,X-ray diffraction(XRD),nuclear magnetic resonance experiment,nano-CT scanning technology and Image J image processing software.The study findings show that the rocks of shale gas reservoir mainly consist of greyish black-black shale rich in organic matters and with a porosity greater than 2%and a permeability greater than 0.01×10^(-3)μm^(2).Most of the pores are organic ones with good connectivity,and there are also some intergranular and intragranular pores,as well as a small number of micro-cracks.The pore size is in the range of 5~50 nm.The three types of pore structures are different in pore type,total organic content(TOC)and pore size.Type Ⅰ pores are mainly organic ones,with high TOC and good reservoir quality.Type Ⅱ pores have moderate organic content,which are mainly composed of micropores-mesopores provided by organic matters and clay minerals.Type Ⅲ pores have low organic content,which are mainly composed of some micropores and mesopores provided by clay minerals.