吐哈盆地鄯勒地区西山窑组油藏储层特征及储油机理

Reservoir Characteristics and Storage Mechanism of Xishanyao Formation in Shanle Area,Tuha Basin

鄯勒低渗透油气藏储层物性差,纵向上存在2个次生孔隙发育带,对应于西山窑组二段和三工河组油层。次生孔隙发育带钾长石溶蚀强烈,自生高岭石很发育,相对含量大于25%,以蠕虫状和书页状分布于骨架颗粒间。大量自生高岭石发育所需的开放—半开放流体体系同时也有利于油气富集。根据成岩作用特点及储层孔隙演化特征,对西山窑组二段储层划分了3种成岩—储集相,评价了不同成岩作用相互作用下的次生孔隙发育的程度。此外,沉积条件决定了砂体原始物性的好坏,后期构造作用形成的裂缝又有效地改善了储层物性,三者共同控制了研究区油气的富集程度,是鄯勒地区西山窑组背斜型油藏的储油机理。

Low permeability hydrocarbon reservoirs in the Shanle area have two secondary pore zones vertically： Middle Xinshanyao Formation and Sangonghe Formation oil layers. In the secondary pore zones, potassium feldspar is corroded intensely; authigenic kaolinites are well developed with more than 25% relative content and occur as book and vermicular kaolinites between the skeletal grains. The well developed authigenic kaolinites need the diagenetic environment which is an open or half-open flow system. This was also favorable for hydrocarbon accumulation. According to the characteristics of diagenesis and pore evolution, the reservior of Middle Xinshanyao Formation can be divided into three diagenetic facies. We evaluated the development of secondary porosity in condition of mutual action of different diagenesis. Besides, depositional condition controls original physical properties of sand, and fractures generated by late tectonization improves the physical properties, all of them control the enrichment of hydrocarbon in this area. These factors are oil storage mechanism of anticlinal reservior in Xinshanyao Formation of Shanle area.