四川盆地焦石坝地区龙马溪组页岩微观孔隙结构特征及其控制因素  

Characteristics and controlling factors of micro-pore structures of Longmaxi Shale Play in the Jiaoshiba area,Sichuan Basin

作　　者：郭旭升[1] 李宇平[1] 刘若冰[1] 王庆波[1] 

机构地区：[1]中国石化勘探南方分公司

出　　处：《天然气工业》2014年第6期9-16,共8页Natural Gas Industry

基　　金：中国石油化工集团公司重大专项"四川盆地周缘下组合页岩气形成条件与有利区带评价"(编号:P13129)

摘　　要：页岩储层岩石的孔隙结构是影响页岩气藏储集能力和页岩气开采效果的主要因素。为此以四川盆地焦石坝地区下志留统龙马溪组页岩为研究对象，运用氩离子抛光扫描电镜技术、低温氮气吸附脱附法和高压压汞实验对该区页岩储层的微观孔隙结构进行了系统研究。结果表明：①焦石坝地区龙马溪组页岩孔径主要为纳米级，孔隙类型可分为有机质孔、无机孔（粒间孔、粒内孔、晶间孔、溶蚀孔）、微裂缝（矿物颗粒内构造缝、层间滑动缝、成岩收缩缝、有机质演化异常压力缝），以有机质孔和黏土矿物粒间孔为主，其中有机质孔分布最为广泛；②TOC与有机质孔含量存在着明显的正相关性，在底部优质泥页岩段（TOC〉2％）有机质孔最为发育，含量高达50％；③微观孔隙结构复杂，多呈开放形态，以两端开口的圆筒状孔及四边开放的平行板状孔为主，孔径大小主要分布在2～30nm，以中孔为主。在此基础上，分析了该区页岩储层微观孔隙结构的控制因素，结论认为，有机质丰度和热演化程度为其主控因素，黏土矿物含量对其影响相对不明显。Pore structure of a shale gas play is a major factor influencing the storage capacity of a shale gas reservoir and the effect of shale gas development. Taking the I.ongmaxi Shale Play in the Jiaoshiba area of Sichuan Basin as the target, we systematically studied the microscopic pore structures of the shale reservoir by using Argon-ion polishing Scanning Electron Microscope （SEM）, high- pressure mercury injection and low temperature nitrogen adsorption and desorption technology. The studies revealed that the pores in shale are dominated by nano-scale pores and can be classified into organic pores, inorganic pores （intergranular pores, intragranular pores, inter-crystalline pores and dissolution pores）, microfracture （intragranular structure fracture, inter-layer sliding fracture, di agenetic constricted fracture and abnormal pressure fracture from organic evolution）. The organic pores and clay mineral pores are predominant, of which the organic pores are the most common pore type. TOG values show an obvious positive correlation with the content of organic pores. The organic pores are the most highly developed in the lower high quality clay-shale with a TOC over 2 and have a content of up to 50%. The microscopic pore structures are very complex and are mostly in open shapes. A cylinder shape with two open ends and a parallel tabular shape being open in four sides are dominant. Pore diameters are in the range of 2 - 30 nm with moderate pore predominant. In addition, organic richness and thermal maturity are believed to be the major factors controlling the microscopic pore structures of the shale, while the effects of clay minerals are relatively insignificant.

关 键 词：四川盆地 焦石坝地区 早志留世 页岩 微观孔隙结构 控制因素 有机质孔 热演化程度 页岩气 

分 类 号：P618.13[天文地球—矿床学]