煤层孔隙与裂隙特征研究进展

煤层孔隙与裂隙发育特征是非常规油气沉积学的重要研究内容，其研究对深入认识煤层流体赋存与传质过程微观机理、优化地质适配性开发工艺具有重要意义。煤层孔隙、裂隙成因类型复杂、尺度分布范围广、非均质性强，其发育特征是煤化作用、变质作用类型、构造演化作用、煤岩物质组成、地下流体等多因素共同作用的结果。煤化作用是其内因，构造应力作用是其主要外因，内外因作用下形成了不同煤阶、不同含煤盆地、不同构造部位煤层孔隙、裂隙发育的现今特征，而成煤物质、沉积环境、盆地埋藏史、热史等具有重要的控制作用。煤层孔隙、裂隙的研究与煤层气高效开发紧密关联，未来研究中将煤层孔隙—裂隙作为具有整体性的解吸—扩散—渗流网络加以认识更具意义，而煤层孔隙—裂隙连通网络控制的渗透率来源和有效性、纳米尺度孔隙—裂隙发育特征与结构关系、孔隙—裂隙与煤层流体之间的界面性质、多尺度孔隙—裂隙结构表征等需要进一步探讨。数字岩石物理表征技术的发展和应用为该领域的研究提供了新方法和新思路。

Research Advances on Characteristics of Pores and Fractures in Coal Seams

The study of the characteristics and relationships of pores and fractures in coal seams is an important research in unconventional petroleum sedimentology,and is of great significance for understanding the micromechanisms of the existence,state,and mass transfer process of coal seam fluid,and for optimizing the exploitation of coalbed methane(CBM)where geologically appropriate.The pores and fractures in coal seams have complex genesis,with wide-ranging scale and strong heterogeneity.Their characteristics are the result of the combined actions of coalification,metamorphism types,tectonic evolution,coal components,and underground fluids.Coalification is the internal cause of pore and fracture characteristics,while tectonic stress is the major external cause.The combined actions of internal and external causes have formed the presently observed characteristics of pores and fractures in coal of different rank,in different coal-bearing basins,and in different tectonic locations.Moreover,the coal-forming materials,sedimentary environment,burial history and thermal history of coal-bearing basins each play important roles in determining the present pore and fracture characteristics.The study of pore and fracture characteristics is closely related to the efficient exploitation of CBM,which implies that considering pores and fractures in coal as an entire desorption–diffusion–seepage network in further research will be a sensible approach.The source and effectiveness of coal permeability is controlled by pore/fracture connected networks,nanoscale pore/fracture characteristics and their syntagmatic relations:interfacial properties of pores,fractures and coal seam fluids,together with multiscale pore/fracture characterization,all need to be further researched.The development and application of digital petrophysical characterization technology provides new methods and ideas for research into pore and fracture characteristics.