利用微观孔隙结构参数对辽河大民屯凹陷页岩储层分级评价

依据全岩XRD衍射、低温氮气吸附实验获取平均孔径、比表面积、绿泥石相对含量等微观储层评价参数,对辽河大民屯凹陷页岩储层分级评价。研究表明:3个微观参数彼此之间存在明显的线性关系;平均孔径与绿泥石含量呈线性关系,绿泥石相对含量越高,平均孔径越大,其主要原因是绿泥石富集化学性质活泼的Fe元素,可吸附大量有机质,有机质在成熟演化阶段可生成大量的有机酸而形成溶蚀孔,并增加储层的平均孔径;平均孔径与比表面积之间也呈现明显的线性关系,且具有明显的三分性,当平均孔径大于10 nm时比表面积均小于1 m2/g,当平均孔径为5～10 nm时,比表面积介于1～6 m2/g,当平均孔径小于5 nm时比表面积均大于6 m2/g;比表面积和绿泥石相对含量两个微观参数之间也呈现出线性关系,且各个拐点之间的参数具有一致性,绿泥石相对含量为5％和9％时,对应的平均孔径为5和10 nm、比表面积为6～1 m2/g,可利用该拐点对页岩储层分级评价。
Based on experimental approaches including whole-rock XRD and low-temperature nitrogen adsorption, this research targeted three parameters (average pore size, specific surface area and relative content of chlorite) to establish a grading system for the shale reservoirs in Damintun Depression in Liaohe Oilfield, Northeastern China. The results show that the three microscopic parameters share obvious linear relationship between each other. Higher content of chlorite is usually related to larger average pore size. This can be explained that chlorite is rich in Fe, which is chemically active and is capable of attracting lots of organic matters. The organic matters can subsequently turn into organic acid during the maturing and evolution processes to form numerous solution pores. The study also shows an evident trichotomy in the relationship between average pore size and specific surface area:when the average pore size is more than 10 nm,the associated surface area is less than 1 m2/g; When the average pore size ranges between 5 and 10 nm,the specific surface area varies between 1 m2/g and 6 m2/g; and lastly when the average pore size is less than 5 nm,the specific surface area is more than 6 m2/g. Microscopic parameters between specific surface areas and the relative content of chlorite also show clearly linear relation. Consistencies are observed between turning points:relative content of chlorite(5％ and 9％), average pore size (5 nm and 10 nm), and specific surface area (6-1 m2/g). The turning points can be used to grade the quality of microspore structures in shale reservoirs