伊拉克W油田白垩系生物碎屑灰岩储层高渗层成因及分布规律  

Genesis and distribution of high permeable streaks of the Cretaceous bioclastic limestone reservoir in W Oilfield, Iraq

作　　者：韩海英[1] 田中元[1] 徐振永[1] 姚子修[1] 衣英杰[1] 李峰峰 HAN Haiying;TIAN Zhongyuan;XU Zhenyong;YAO Zixiu;YI Yingjie;LI Fengfeng

机构地区：[1]中国石油勘探开发研究院

出　　处：《海相油气地质》2022年第3期261-270,共10页Marine Origin Petroleum Geology

基　　金：国家科技重大专项课题“伊拉克大型生物碎屑灰岩油藏注水开发关键技术研究与应用”(编号:2017ZX05030-001)资助。

摘　　要：中东地区白垩系生物碎屑灰岩储层普遍存在高渗层,随着注水开发的进行,高渗层导致注入水快速水蹿,给油田开发带来严重的挑战,因此研究高渗层的成因及分布具有重要的意义。基于岩心、铸体薄片、物性和测井等资料,分析了伊拉克W油田Mishrif组油藏内高渗层的沉积、岩性、物性、电性等特征,阐明了高渗层的类型及成因机理,厘清了高渗层的分布规律。研究表明:高渗层根据成因可分为沉积主控型、成岩主控型和构造主控型等3类。沉积主控型高渗层主要发育在MB1段潮道和MB2L段内缓坡滩中,前者岩性以生物碎屑颗粒灰岩和砾屑灰岩为主,平均孔隙度为23.5%,平均渗透率为173×10^(-3)μm^(2),测井曲线呈现为箱形和钟形特征;后者岩性以生物碎屑泥粒灰岩为主,平均孔隙度为26.7%,平均渗透率为103×10^(-3)μm^(2),测井曲线呈现为漏斗形特征。成岩主控型高渗层主要分布在MB2U段台缘滩中,岩性以生物碎屑砾屑灰岩、颗粒灰岩和泥粒灰岩为主,平均孔隙度为27.0%,平均渗透率为216×10^(-3)μm^(2),测井曲线呈现为箱形+漏斗形特征。构造主控型高渗层主要分布在MA段局限台地丘滩体内,岩性以砾屑灰岩、颗粒灰岩和泥粒灰岩为主,平均孔隙度为23.6%,平均渗透率为108×10^(-3)μm^(2),测井曲线表现为略偏低的自然伽马、低密度和高声波时差的特征。这3类高渗层的成因机理、发育模式和分布规律均有所差异:沉积主控型高渗层主要由高能沉积体叠加同生-准同生期淡水溶蚀而形成,平面上呈网状和片状分布;成岩主控型高渗层主要由同生-准同生期和表生期两期大气淡水溶蚀改造而形成,平面上呈席状分布;构造主控型高渗层主要由同生-准同生期大气淡水溶蚀、沿断层流入的大气淡水和地层酸性流体溶蚀等多期成岩改造而形成,平面上沿断层呈斑状分布。High permeable streaks(HPS) are commonly developed in the Cretaceous bioclastic limestone reservoirs in Middle East. With the progress of water injection, the existence of HPS leads to rapid water channeling, which brings serious challenges to oilfield development. Therefore, the study on the cause and distribution of HPS is of great significance. Based on the data of cores, cast thin sections, physical property and logging, this paper analyzes the characteristics of sedimentation, lithology, physical property and electrical property of the HPS in Mishrif Formation of W Oilfield in Iraq, and clarifies their types, genesis and distribution pattern. The result shows that the HPS of Mishrif Formation can be divided into three types according to their genesis: sedimentation-dominated type, diagenesisdominated type, and tectonism-dominated type. The sedimentation-dominated HPS are mainly developed in tidal channels of MB1member and in inner ramp shoals of MB2L member. The former is dominated by bioclastic grainstones and rudstones with average porosity of 23.5%and average permeability of 173×10^(-3)μm^(2), the logging curves are boxshaped and bell-shaped;the latter is mainly composed of bioclastic packstones with average porosity of 26.7%and average permeability of 10~3×10^(-3)μm^(2), the logging curves are funnel-shaped. The diagenesis-dominated HPS are mainly distributed in the platform margin of MB2 Umember which are mainly composed of bioclastic rudstones, grainstones and packstones,with an average porosity of 27.0% and an average permeability of 216×10^(-3)μm^(2), and the logging curves are box-shaped + funnel-shaped. The tectonism-dominated HPS are mainly distributed in the mounds and shoals of the limited platform in MA member, which are mainly composed of bioclastic rudstones, grainstones and packstones, with average porosity of 23.6% and average permeability of 10~8×10^(-3)μm^(2).The logging curves are characterized by low natural gamma-ray, low density, and high interval transit time.The genesis, dev

关 键 词：生物碎屑灰岩 高渗层 成因 白垩系 伊拉克 中东 

分 类 号：TE122.2[石油与天然气工程—油气勘探]