库车前陆冲断带低渗砂岩的裂缝发育模式

Model for the Fracture Development of the Sand with Low-permeability in the Foreland Faulted Fold Belt

致密砂岩是重要的非常规储层,其裂缝的发育程度影响了储集性和渗透性。本文以库车坳陷北部野外裂缝测量和统计分析为例,研究前陆冲断带致密砂岩区裂缝发育的规律。提出前陆冲断带的构造裂缝可以分为三期:前褶皱期、同褶皱期和后褶皱期。根据每个实测剖面各测量点裂缝密度的测量统计分析,并与逆断层及相关褶皱的构造要素,如距断层或褶皱轴面的距离,开展回归分析,分别半定量地建立了逆断层及相关褶皱控制裂缝发育的模型,提出两种成因的构造裂缝,即"局部构造控制的裂缝带"和"区域构造裂缝"。前陆冲断带内局部构造控制的裂缝发育带具有上盘裂缝比下盘发育,背斜顶部和陡翼的裂缝比缓翼和远离断层区域更发育的特点。

Tight sands are an important type of unconventional reservoir. The development intensity of fractures in the tight sands influences the reservoir capacity and permeability. The fracture development of the sands in the foreland faulted-folds is researched through measuring and analysis of field fractures in the northern Kuche basin. Three episodes of structural fractures are indentified as pre-folding, syn-folding, and post-folding fractures. The models of fractures controlled by different structures are proposed by regression analysis of the measured fracture densities and distances to fold-axial plane or thrust fault. Two types of structural fractures are therefore proposed, which include the“damage zone controlled by local structures”and the“regional structural fractures”. The fractures in the hanging wall of the fault are more developed than those in the footwall. Similarly, the fractures in the top and high tilted limb of the fold are more developed than those in the low tilted limb far away from the fault.