鄂尔多斯盆地曾岔地区延安组和延长组储层特征对比分析

Comparative analysis of reservoir characteristics of Yan'an and Yanchang Formations in Zengcha Area,Ordos Basin

厘清储层的宏观结构和微观物性特征对油藏勘探开发意义重大。针对近年来不断有新油藏发现但研究程度较低的曾岔地区,利用大量岩石薄片、扫描电镜、阴极发光和物性分析等资料,结合沉积砂体展布特征,对延安组和延长组储层特征及其控制因素进行了对比分析。研究表明:延安组和延长组分别以中-细粒石英砂岩和细粒长石砂岩为主,延长组胶结物含量总体大于延安组,其中以方解石和绿泥石最为发育;储集空间以粒间孔为主,其次为长石溶孔、岩屑溶孔和晶间溶孔,其中延安组储层孔隙结构好,物性明显优于延长组,在延长组中,长6好于长4+5,长7和长9油层组。曾岔地区储层的发育受宏观沉积作用和微观成岩作用的共同影响,辫状河中边滩和心滩砂体物性一般好于主河道,三角洲前缘中水下分流河道砂体物性一般好于水下天然堤;压实和胶结作用对延长组储层物性的破坏程度较延安组大,但溶蚀作用延长组较延安组发育,溶蚀产生的次生溶孔是延长组储层物性改善的主要途径;储层中碳酸盐胶结物含量普遍较高,由于其后期溶蚀作用较弱,因此碳酸盐对储层物性的破坏性尤为明显。

Understanding the macrostructure and microscopic characteristics of reservoirs is of great significance to the future petroleum exploration. This paper focus on the Zengcha Area in Ordos Basin, where new oil reservoirs have been found in recent years but the research level still need improve. Ac- cording to the massive data of reck thin section, cathodoluminescence, scanning electron microscope and the physical property analysis, in the context of distributionof the sedimentary sand body of the sedimentary sand body distribution, the reservoir characteristics and control factors of Yan＇ an Formation and Yanchang Formation were compared and analyzed. The results show that the rock types of the Yan＇ an Formation and the Yanchang Formation are mainly composed of medium-fine quartz arenite and arkose. The cement content of Yanchang Formation was larger than Yan＇ an Formation, and the cement is domi- nated by calcite and chlorite. The main pore type of the reservoir is intergranular, whereas feldspar, cut-tings and intercrystauine solution pores are also identified. In general, the pore structure and physical properties of the reservoirs in Yan＇ an Formation are better than those in Yanchang Formation. In Yan-chang Formation, the Chang 6 is better than the Chang 4＋5 ,Chang 7 and Chang 9. In Zengcha Area,the development of reservoirs is controlled by the coupling of sedimentation and diagenesis, the physical prop-erties of the point bar and braid bar are generally better than the channels, and distributary channels in the delta front are generally better than levees. The destructive impact of cementation and compaction on reservoir is greater in Yanchang Formation, where the dissolution is more abundant. Secondary pore formed by dissolution is the main factor enhancing reservoir property in Yanchang Formation. Although the car- bonate cement content in the studied reservoir is high, the dissolution is relative weak; the impact of car- bonate cement on reservoirs is mainly manifested by the destruction of physical property of reserviors.