川南龙马溪组页岩气储层纳米孔隙结构特征及其成藏意义

以川南龙马溪组页岩气储层为例，运用氮气吸附法对储层纳米孔隙进行测定，通过等温线和DFT分析，对孔结构特征表征并讨论控制纳米孔隙结构的主因和纳米孔隙对页岩气成藏的意义。结果表明：龙马溪组页岩气储层孔隙结构较复杂，主要由纳米孔组成，具有一定的无规则孔结构，孔隙多呈开放形态，以两端开口的圆筒孔及4边开放的平行板孔等开放性孔为主；垂向上由深到浅，孔隙开放程度减小；纳米主孔位于2~40 nm，占孔隙总体积的88.39%，占比表面积的98.85%；2~50 nm的中孔提供了主要的孔隙体积，小于50 nm的微孔和中孔提供了主要的孔比表面积；TOC是控制该储层中纳米孔隙体积及其比表面积的主要内在因素，也是提供页岩气主要储存空间的重要物质；纳米孔对页岩气的吸附能力极强，在其内部有大量页岩气以结构化方式存在，增加了页岩气的存储量，并使模型表征复杂化；开放状纳米孔可提高页岩气解吸效率和储层渗透率，提高页岩气的产量。

Structure characteristics and accumulation significance of nanopores in Longmaxi shale gas reservoir in the southern Sichuan Basin

Presented a study on shale gas reservoir of Longmaxi Formation of Lower Silurian in southern Sichuan Basin.The reservoir porosity was measured using nitrogen adsorption method.The pore volume,pore specific surface area and pore size distribution were studied through the isotherms and DFT analysis.Based on all of these,discussed the main factors to control the nanopore structure and the nanopore’s influence on shale gas accumulation.The results show that,the pore structure of the shale gas reservoir of Longmaxi Formation is relatively complex,which is composed of nanopores and possesses a certain ruleless structure(the amorphous pore),pores are open in style and mainly consist of the cylinder pores with two ends open and parallel-plate pores with four sides open.It is concluded that openness degree of the pores improved with the increase of the vertical depth,the sizes of the main nanopores are in a range of 2～40 nm,which take up 88.39% of the total volume of pores and 98.85% of specific surface area.Most of the pore volume is occupied by the mesopores which are 2～50 nm in size.The micropores and mesopores of which the diameters are less than 50 nm dominate the main pore specific surface.The main internal factor to control the volume and the pore specific surface of nanopores of the shale gas reservoir in Longmaxi Formation is TOC content.It is also the important substance to provide the main storage space.The nanopores have a strong ability to absorb shale gas,the interior of which is structured filled with the shale gas,thus increase shale gas storage capacity and finally make the model characteristic complicated.The open nanopores can improve the shale gas desorbing efficiency and the permeability of the reservoirs,and then improve the shale gas production.