鄂尔多斯盆地白于山井网加密区延长组长4+5特低渗储层沉积特征和储层物性分析

Comprehensive Depositional System and Reservoir Characterization Study of Chang 4+5 Reservoir of Yanchang Group, Infill Well Region in Baiyushan Area, Ordos Basin

以岩芯、薄片资料为基础,结合常规测井和成像测井等资料,综合分析鄂尔多斯盆地白于山井网加密区上三叠统延长组长4+5特低渗储层的沉积特征和储层特征,进而解剖储层砂体在纵向及平面的展布特征。结果表明,长4+5储层主要为一套中-细粒长石砂岩,发育平行层理和交错层理;储集空间以中小孔径的粒间孔为主,发育少量裂缝,储层物性较差。储层砂体在平面上呈较均匀的条带状展布,厚度在2~5 m之间;沉积亚相以三角洲前缘为主,发育水下分流主河道、水下分流浅河道、水下分流浅滩和水下分流间湾4种沉积微相。在纵向上,水下分流主河道及浅河道交替变化,在各小层有规律的展布。研究结果对进一步寻找白于山地区的油气富集区有一定的指示意义。

The authors focus on the ultra-low permeability reservoirs of Chang 4+5 reservoir period of Yanchang Group,Jing’an oil field,Ordos Basin.Cores,thin sections,wireline logs,and imaging logs were used to understand depositional systems,reservoirs and to furtherly characterize vertical and horizontal distribution patterns of sandstones.The results show that main reservoirs of Chang 4+5 of Yanchang Group are composed of medium-tofine grained arkose.Parallel beddings and cross beddings are common.Interpartical pores and a few fractures are main reservoir spaces and reservoir quality is poor.Sand bodies are uniformly distributed in the horizontal direction with brand shape and thickness between 2 to 5 meters.Front delta is the main sedimentary subfacies.Distributary main channel,distributary shallow channel,distributary shoal,and inner distributary bay are four main sedimentary microfacies.In the vertical direction,distributary main channels and distributary shallow channels are distributed reciprocally related to the variation of hydrodynamic power.The research result is a guidance on the hydrocarbon exploration in this region.