柴达木盆地油砂山油田上干柴沟组沉积微相特征

Microfacies Characteristics of Upper Ganchaigou Formation of Youshashan Oilfield in Qaidam Basin

摘要: 以岩芯观察和测井分析为基础，通过对柴达木盆地油砂山油田上干柴沟组的沉积背景、物源方向、沉积构造、粒度分析的研究，确定其为一套以陆源碎屑的辫状河三角洲逐渐向浅湖过渡的沉积。区内以浅水三角洲前缘亚相沉积为主体，主要包括辫状分流河道微相、分流河道间微相、水下分流河道微相、水下分流河道间微相、河口坝微相、远砂坝微相、席状砂微相、砂坝微相、砂滩微相、颗粒滩微相、浅滩微相、浅湖泥微相等11种沉积微相类型。此外，以单井微相分析为基础，结合大量的地球物理测井及录井资料，研究了区块内上干柴沟组6个油层组的沉积微相平面分布规律，最有利砂体主要发育在三角洲前缘的水下分流河道、河口坝及浅湖砂坝中。沉积微相的精细研究为推测有利相带为良好的岩性油气藏的发育、主力层剩余油挖潜以及油田的下一步勘探开发奠定了基础。

Abstract: Based on core observation and logging analysis, the upper Ganchaigou formation of Youshashan in Qaidam Basin is determined to deposit in the terrigenous clastic transitional environment from the braided delta to the shallow river, through the research on its sedimentary background, source direction, sedimentary structure and analysis of grain sizes. The region is dominated by shallow- water delta front, including the braided distributary channels, interdistributary areas, sub- aqueous distributary channels, sub-aqueous interdistributary areas, mouth bars, distal bars, sheet sands, sand bars, sand beaches, grain banks, shallow-lake sheet sands and mudflats. What’s more, on the basis of single-well facies analysis, integrated with a great mass of geophysical logging and well logging data, a study has been made on the microfacies areal distribution patterns of the six oil layer groups in upper Ganchaigou formation in the region, and it has been found out that the most favorable sand bodies were deposited in the sub-aqueous distributary channels and mouth bars in the delta front and sand bars in the shallow lake. The fine studies of microfacies lay a foundation for the speculation of the favourable facies belts, the potential tapping of remaining oil in the main layers and the future exploration and development of the oil field.