摘要
为了弄清川西坳陷须五段致密砂岩与泥页岩储层发育特征及控制因素,并深化对非常规致密气储层的认识,利用岩心、铸体薄片、扫描电镜、X射线衍射及压汞等资料,对须五段储层岩石学、储集空间、物性等特征及其控制因素进行了研究。结果表明:须五段储层岩性大致分为泥页岩、粉砂岩和细砂岩三大类,分别占地层总厚度的56%,19%和25%,砂岩普遍具有泥质杂基和岩屑含量高、长石含量低的特征,泥页岩中石英等脆性矿物含量较高;储集空间包括有机质孔、杂基微孔、粒内溶孔、粒间溶孔及微裂缝5类;细砂岩孔隙度和渗透率平均值分别为1.41%和0.1 m D,属于致密砂岩储层,主要为高能的水下分流河道微相沉积,粉砂岩孔隙度和渗透率平均值分别为1.52%和0.22 m D,总体均略高于细砂岩,泥页岩孔隙度和渗透率平均值分别为1.95%和0.068 m D,属于致密页岩储层;储层物性主要受到沉积条件、成岩作用和构造裂缝的多重控制,强烈的压实和压溶作用是导致砂岩致密的主要原因,次生孔隙主要由溶蚀作用形成,黏土矿物的转化及有机质热演化为泥页岩提供了大量储集空间,微裂缝极大地改善了储层渗透性。研究结果可为该区下一步油气勘探提供一定参考。
The exploration of nonmarine unconventional tight gas is still in the early stage. In order to explore the research methods of tight gas in nonmarine shale sequence, the data of cores, cast thin sections, scanning elec-tron microscope, X-ray diffraction and mercury injection, were used to study the petrology, reservoir space, physical properties and main controlling factors of the fifth member of Xujiahe Formation in the Westem Sichuan Depression. The results show that the lithology was composed of three types：shale （56%）, siltstone （25%） and fine sandstone （ 19% ）. There are high content of matrix and debris, low content of feldspar in sandstone, and high content of quartz mineral in shale. The reservoir spaces include organic pores, mixed matrix pores and intra- granular dissolved pores, intergranular dissolved pores and microfractures. The average porosity and permeabili- ty of sandstone are 1.41% and 0.1 mD, respectively, so it belongs to tight sandstone reservoir, and mainly in high power subaqueous distributary channel. The average porosity and permeability of siltstone are 1.41% and 0.1 mD, respectively, and the average porosity and permeability of shale reservoir are 1.95% and 0.068 mD, respectively. The reservoir properties are mainly controlled by deposition conditions, diagenesis and structural fracture. Strong compaction and pressure dissolution are the main factors leading to the tightness of sandstone. Secondary pores are mainly formed by dissolution. The transformation of clay minerals and the thermal evolution of organic matter provide a large amount of reservoir spaces for shale, and microfracture greatly improves the reservoir permeability. The results can provide a reference for tight gas exploration in this area.
出处
《岩性油气藏》
CSCD
北大核心
2017年第4期38-46,共9页
Lithologic Reservoirs
基金
国家重大科技专项"四川盆地碎屑岩层系大中型油气田形成规律与勘探方向"(编号:2011ZX05002-004)资助
关键词
致密砂岩
泥页岩
储层特征
控制因素
须五段
川西坳陷
tight sandstone
shale
reservoir characteristics
main controlling factors
the fifth member of Xujiahe Formation
Western Sichuan Depression
