邛西构造须二段特低渗透砂岩储层微观裂缝的分布特征

DISTRIBUTION OF MICROFRACTURES IN ULTRALOW PERMEABILITY SANDSTONE RESERVOIRS OF THE SECOND MEMBER OF XUJIAHE FORMATION (T_3x_2) IN QIONGXI STRUCTURE

根据微观薄片分析,结合岩心与地表露头资料,对邛西构造须二段特低渗透砂岩储层微观裂缝的类型、特征、期次及其参数分布进行了研究。邛西构造上三叠统须二段储层发育粒内缝、粒缘缝和穿粒缝3种类型的微观裂缝,其成因以构造微裂缝为主,此外还有成岩微裂缝以及与异常高压有关的微裂缝。微观裂缝具有5次充填序列,反映了3次构造破裂事件以及1次成岩破裂事件、1次与异常高压有关的破裂事件。微观裂缝是该区重要的储集空间,对改善特低渗透砂岩储层的储集性能起着重要的作用。

The types, characteristics, ages and parameters of the microfractures in T3x2 of Qiongxi structure are studied through microscopic thin section analysis and in combination with core and outcrop data. Three types of microfractures, i.e. intragranular, grain edge and transgranular fractures, are developed in T3x2 sandstone reservoirs of Qiongxi structure, and their genetic types are dominated by structural microfractures, followed by diagenetic microfactures and microfractures related with surpressure. The microfractures show 5 filling sequences, which represent 3 tectonic disruption events, 1 diagenetic fracturing event and 1 fracturing event related with surpressure. The microfractures are the major reservoir space in the study area and play an important role in improving the poroperm characteristics of the ultralow permeability sandstone reservoirs.