沾车地区泥岩裂缝成因分析

Formation Analysis of Mudstone Fracture in Zhanche Area

沾车地区沙三下亚段与沙一段泥岩裂缝发育,但是裂缝分布规律复杂多变制约了勘探进展。对裂缝成因及主控因素进行深入分析后,将泥岩裂缝按成因划分为成岩裂缝(溶蚀裂缝、矿物收缩裂缝、油气演化裂缝)、构造裂缝(扩张裂缝、拉张裂缝、剪切裂缝)和变质收缩裂缝共3大类7种类型。泥岩裂缝的形成和发育主要受沉积环境、成岩作用和构造活动的影响。半干旱半湿润气候、半咸水湖泊中的深湖-半深湖环境最有利于泥岩裂缝的形成和发育;早成岩阶段A期成烃作用和黏土矿物转化作用有利于成岩裂缝的形成;在大断层和岩浆侵入带附近构造裂缝发育。物源不太发育的缓坡带和洼陷带沙三下亚段是泥岩裂缝的集中发育的区带和层系。

Fractures are developed in Esx3and Es1mudstone of Zhanche area,however the complex distributions restricte its exploration progress.By the in-depth analysis of the causes of cracks and controlling factors,the mudstone fractures is devided into Seven types of three categories by cause,including：diagenetic cracks（dissolution seams,mineral shrinkage cracks and oil-gas evolutionary fracture）,tectonic fractures（expansion cracks,tension cracks and shear cracks）,and metamorphic shrinkage cracks.Formation and development of mudstone fractures depend on the impacts of sedimentary environment,diagenesis,and tectonic activity.Semiarid and semihumid climate conditions,deep and semi-deep brackish lake environment are the most conducive conditions for the formation and development of mudstone fracture.Earlier diagenetic A is the main period of mudstone fracture formation due to hydrocarbon generation and clay minerals transformation.Tectonic fractures are developed nearby the large fault zone and magmatic intrusion.Gentle belt which has less developed provenance and sag of Esx3are the concentrated development zone and strata.