库车坳陷 DB 气田白垩系巴什基奇克组砂岩的多期溶蚀

摘要

以岩心观察、普通薄片和铸体薄片观察与鉴定为基础，辅以阴极发光显微镜、扫描电镜和油层物性分析等技术手段，结合区域地质研究成果，系统研究塔里木盆地库车坳陷DB气田白垩系巴什基奇克组砂岩储层溶蚀作用特征及其发育机制，并剖析其与孔隙演化的关系。结果表明，库车坳陷DB气田白垩系巴什基奇克组砂岩为特低孔－特低渗储层，发育多种溶蚀孔隙。储层经历多期溶蚀作用，依次为大气淡水表生淋滤溶蚀作用、有机酸溶蚀作用、微弱的碱性溶解作用和较弱的酸碱交替溶蚀作用，分别溶蚀早期碳酸盐胶结物、长石、不稳定岩屑和石英质组分等，形成粒间溶孔、溶蚀缝、超粒大孔隙、粒内溶孔等溶蚀孔隙。结合地层埋藏史、有机质发育史和构造演化史等研究成果，综合分析认为，DB气田多期溶蚀和烃类多期注入相匹配是形成现今高产气田的重要原因。%Characteristics and genesis of dissolution and its influence over pores in sandstone reservoirs of the Cretaceous Bashijiqike Formation in DB gas field of Kuqa Depression are studied based on observation of cores,and normal/cast thin sections,analyses through cathodoluminescence microscope,scan electricity microscope,and characterization of reservoir physical properties,and etc.The result shows that the sandstone reservoirs in the Formation have ultra-low porosity and permeability and contain various types of dissolved pores.The reservoirs had experienced successively atmospheric water supergene leaching ( dissolving carbonate cementation) ,organic acid dissolution ( dissolving feldspar) ,weak alkaline dis-solution ( dissolving unstable debris) ,and less weak alternative acid/alkali dissolution( dissolving quartzose) ,resulting in intergrannular dissolution pores,dissolution fractures,large dissolution pores surpassing grain size,intragranular dissolu-tion pores,and etc.A combination of the study with previous analyses,including stratigraphic burial history,and evolu-tionary history of organic matter and tectonics of the Formation,indicates that right timing between multi-staged dissolu-tion and hydrocarbon charge was critical for forming prolific DB field.