摘要
鄂尔多斯盆地富县探区上三叠统延长组具有多层系、多套生储盖组合特点,是该盆地重要的天然气产层,但目前该区忽略了成岩作用对储集层影响的研究。通过铸体薄片、扫描电镜、X射线衍射、阴极发光等分析手段并结合本区沉积微相特征,研究储层成岩作用并寻找出有利成岩相带,确定相对优质储层的分布规律。结果表明:(1)多种成岩作用对储层砂岩物性造成强烈影响,其中早成岩阶段的压实作用、压溶作用和晚成岩阶段铁方解石的胶结作用是造成低孔隙、低渗透储层的主要因素;(2)长二段储集砂岩主要处于中成岩阶段A期,少部分处于中成岩阶段B期,砂岩主要成岩序列为压实作用→绿泥石胶结→大气水淋滤、长石强烈溶蚀溶解→次生孔隙形成→自生高岭石→自生石英→烃类侵位→晚期铁方解石、铁白云石交代胶结;(3)长二段砂体可划分5个成岩相带,其中弱压实—石英加大较弱—绿泥石薄膜—溶蚀成岩相砂岩储层物性最好,储集空间主要以长石溶孔、粒间孔和岩屑溶孔的组合形式出现,孔隙间的连通性良好,为储层发育的优势成岩相带。
The Upper Triassic Yanchang Formation in the Fuxian exploration area of the Ordos Basin has multiple layers and multiple source-reservoir-eaprock assemblages, and it is an important production formation in this basin. However, the current studies seldom deal with the influence of diagenesis on reservoirs. This paper, through casting thin section, scanning electron microscopy （SEM）, X-ray diffraction, and cathodoluminescence analysis, and considering the characteristics of sedimentary microfacies of this area, discussed the reservoir diagenesis, identified the favorable diagenetic facies belts, and clarified the distribution of relatively high quality reservoirs. Several findings are obtained. First, multiple kinds of diagenesis have a strong influence on the physical properties of reservoir sandstone, typically the compaction and pressure solution in the early diagenetic stage and the cementation of ferrocalcite in the late diagenetic stage which are major contributors to low porosity and low permeability reservoirs. Second, the reservoir sandstone of the second member of Yanchang Formation （Chang-2） is mainly in Period A of the middle diagenetic stage, and partially in Period B of the middle diagenetic stage. Sandstone experienced a diagenetic sequence of compaction → chlorite cementation → atmospheric water leaching, and strong corrosion and dissolution of feldspar → formation of secondary pores → authigenic kaolinite → authigenic quartz →hydrocarbon emplacement → metasomatic cementation of ferrocalcite and ferrodolomite in the late period. Third, the sand bodies of Chang-2 can be divided into five diagenetic facies belts. Specifically, the weak compaction-weaker quartz enlargement-chlorite thin film-dissolution diagenetic facies belt is a prominent belt for its best physical properties, with its reservoir space consisting of feldspar dissolved pore, intergranular pores and cuttings dissolved pore which exist in combination and efficiently connected.
作者
王桂成
李育
王钟远
李少卓
第凯翔
Wang .Guicheng Li Yu Wang Zhongyuan Li Shaozhuo Di Kaixiang(School of Earth Sciences and Engineering, Xi＇an Shiyou University, Xian, Shaanxi 710000, China)
出处
《天然气勘探与开发》
2017年第2期13-20,共8页
Natural Gas Exploration and Development
基金
陕西省自然科学基金资助"连续型油藏砂岩疏导体系于石油运移时效性探讨"(编号:2013JM5006)
关键词
鄂尔多斯盆地
晚三叠世
延长组
成岩作用
成岩相
成岩阶段
胶结作用
沉积相
Ordos Basin
Upper Triassic Yanchang Formation
Diagenesis
Diagenetic facies
Diagenetic stage
Cemention
Sedimentary facies
