准噶尔盆地中拐凸起侏罗系三工河组储层特征及控制因素

Reservoir Characteristics and Factors Controlling the Jurassic Sangonghe Formation in Zhongguai Uplift, Junggar Basin

中拐凸起作为准噶尔盆地的一个正向二级构造单元,其成藏背景对油气勘探开发非常有利。选取三工河组主要钻井的岩芯和薄片进行岩石特征学的观察与鉴定,以及X衍射,测井录井,扫描电镜,压汞化验资料分析等手段对三工河组砂岩储层的物性及主控因素进行研究。结果表明:三工河组储层砂岩以长石质岩屑砂岩和岩屑砂岩为主,从三工河组一段到三工河组二段的颗粒逐渐变粗并且颗粒分选以好中等为主,具有砂岩结构成熟度中等、成分成熟度较低等特征。三工河组储层局部呈低孔低渗,主要孔渗特征还是以中孔中渗为主。辫状河三角洲前缘水下分流河道等沉积微相控制着储层孔隙和砂岩粒度的发育。根据资料统计分析储层成岩演化期,认为储层致密性受压实与胶结作用影响最大,进入储层成岩后期,溶蚀作用在一定程度上改善了储层的孔隙度,并在增大储层孔隙度的同时为生成油气创造了良好的运移条件。

As a positive sub tectonic unit in the Junggar Basin,the accumulation background of the Zhongguai Uplift is very favorable for gas exploration.The physical properties and main controlling factors of the Sangonghe Formation sandstone reservoir were studied by observing the petrographic characteristics of rock cores and thin sections in select ed main wells,and by X ray diffraction(X RD)analyses,well logging,scanning electron microscopy(SEM)and mercury injection,revealing that the sandstone reservoir consists mainly of feldspathic litharenite and lithic sand stone.Particles in phase 2 of the Sangonghe Formation are larger than those in phase 1 and were mainly of average size,with medium structure maturation and low composition maturation.The porosity and permeability of the reser voir was low in places,but it was mainly of medium porosity and permeability.Sedimentary microfacies at the fore edge of underwater distributary channels in braided river deltas accounted for pore and sand particle development in the reservoir.Analyses of the evolution over this period indicated that reservoir compactness was mainly influenced by compaction and cementation;following the latter,dissolution may have increased the porosity of the reservoir to some extent and offered favorable pathways for gas accumulation.