鄂尔多斯盆地北部太原组海陆过渡相页岩孔缝特征及油气地质意义

鄂尔多斯盆地太原组海陆过渡相泥页岩是非常规天然气的储集层.通过采集太原组泥页岩样品，利用氩离子抛光-扫描电镜技术，观察抛光后泥页岩样品微孔隙、微裂缝的微观结构特征，分析其成因，认为沉积作用、成岩作用、有机质变质作用、干酪根生烃作用、溶蚀作用、构造应力作用是太原组页岩孔隙、裂缝发育的主控地质因素.同时参考国内外学术界对海相和陆相页岩的孔隙、裂缝类型的划分方案，将太原组海陆过渡相泥页岩孔隙、裂缝初步划分为有机孔、无机孔和微裂缝三大类.有机孔细分为化石孔、生烃孔；无机孔细分为粒间孔、晶间孔和溶蚀孔；微裂缝细分为收缩缝、应力缝和黏土矿物层间缝.太原组页岩中发育的微孔隙、微裂缝，为页岩气（尤其是游离气）提供了良好的储集空间和渗流通道，有利于页岩气的成藏.为页岩气的压裂开采及高产稳产提供了有利条件.

PORE-FRACTURE FEATURES OF THE MARINE-CONTINENTAL TRANSITION SHALES FROM TAIYUAN FORMATION IN NORTHERN ORDOS BASIN AND PETROLEUM GEOLOGICAL IMPLICATION

The marine-continental transition shale of Taiyuan Formation in Ordos Basin serves as an unconventional gas reservoir. The micropores and microfissures of shale samples are observed with argon ion polishing-SEM technique to analyze their genesis. It is thought that sedimentation, diagenesis, metamorphism of organic matter, hydrocarbon generation of kerogen, dissolution and structural stress are the main controlling geological factors for the development of pores and fractures. By reference to the classification schemes at home and abroad for pore-fracture types of marine and continental shale, the pores and fractures of the marine-continental transition shale in Taiyuan Formation fall into three types, namely organic pore, inorganic pore and microfracture, each of which can be further subdivided into several styles. The micropores and microfractures can provide favorable reservoir space and seepage channels for shale gas, especially free gas, which is the precondition for high and stable yield by fracturing development.