乐安油田草4块沙四段稠油油藏储层特征及控制因素

Es_4 Heavy Oil Reservoir Characteristics and Control Factors of Block Cao4 in Le'an Oilfield

盆地边缘缓坡带的圈闭组合与其特定的区域构造特征密切相关,通常发育超覆、剥蚀不整合稠油油藏。以东营凹陷南缓坡乐安油田为例,综合应用地震、岩心、钻井、测井、分析化验资料,对其储层特征及主控因素进行了分析。研究表明,乐安油田草4块沙四段地层划分为2个三级层序;岩石类型以含泥质或灰质不等粒岩屑长石砂岩为主,较高的泥质含量和碳酸岩含量导致储层的敏感性偏强;沉积物源方向来自东南部的广饶凸起,具有水下冲积扇扇中亚相的沉积特征;为高孔、中渗储层。同一油藏内原油性质遵循构造高部原油粘度较低、向构造低部逐渐变稠的变化趋势;纵向上,地层自下而上原油逐渐变稠。沉积特征、不整合、基底大断层、火山活动及埋藏浅等因素,综合控制储层特征和原油性质。

The trap assemblies of the slow slope zone at the basin's edge were closely related to their special areal structural characters,where overlap,unconformity heavy oil reservoirs were usually developed.By taking the typical stratigraphic unconformity heavy oil reservoir-Le'an Oilfield in the southern gentle slope zone of Dongying Depression as an example,the reservoir characteristics and primary control factors were analyzed by applying seismic,core,drilling and logging data.It was of great importance to scientific and effective development of similar special oil and gas reservoirs.The results show that in Es4 reservoir in Block Cao4 of Le'an Oilfield two sequences are developed.The rock types are mainly of carbonaceous or muddy,seriate and pebbled debris-feldspar sandstones.Stronger reservoir sensitivity is induced by higher silt and carbonate contents.The source of sediments is mostly derived from the Guangrao up-lift in the southeast and it has the sedimentary character of mid-subfacies of underwater alluvial fan.It is the reservoir with high porosity and middle permeability.Oil viscosity is lower in the high structure than that in the low structure of a reservoir;and thickens vertically from the bottom to top of the formation,The factors,including sediment characters,unconformity,big basement fault,volcano activity and shallow burial,comprehensively control the reservoir characters and oil property.