利用测井资料评价有利沉积微相带划分油层有效厚度

摘要

雁木西油田白垩系低电阻率油层受沉积相带及断裂、构造和岩性等多种因素控制影响,测井信息应用难度增大.提出利用多种测井响应提取单渗砂层能量厚度信息,使其曲线形态、特征和数据大小能够集中反映相对高渗透率的单渗砂层最大沉积能量及厚度变化.确定扇三角洲前缘水下辫状河道、浅水河道骨架砂体有利微相带的发育、规模及分布范围,克服了层段中几个成因相近薄砂层或砂泥互层中砂层累加厚度导致的划分主体骨架砂体微相带的失误.通过该区白垩系井径、自然伽马、密度、中子、声波测井曲线和岩性、孔隙度及其能量厚度统计,建立起单渗砂层能量厚度下限标准.在该区白垩系目的层段储层中提取单渗砂层沉积能量,分析了水下辫状河道、浅水河道有利沉积微相带展布及其与油气聚集分布的关系.利用有利沉积微相带及其相应的油层有效厚度下限,对该区60多口老井白垩系储层重新进行精细评价解释,分别在K1s1期浅水河道、K1s2期水下辫状河道筛选复查新增油层有效厚度32.0 m和21.0 m,为该区油田增储上产和调整挖潜提供了可靠依据.%In the Yanmuxi oil region, the low resistivity reservoir is influenced by sedimentary fa-cies, fractures, structures and lithologies, so it is difficult to use the logging information. Single sand thickness energy information is picked up by several logging methods to reflect the relatively high permeability's largest sedimentary energy and thickness divergence. On the basis of that, we find out the underwater braided channel to shallow channel sand body are the favorable sedimentary microfacies and distribution regions. And it overcomes the lapse about classifying the frame sedimentary facies due to the total sand thickness in several genetic similar thin sand layers or sand-clay layers. Through the statistic of diameter, natural gamma ray, density, neutrons, a-coustic as well as lithologic character, porosity and sedimentary thickness, we set up the lower limit of the energy thickness of single permeability sand bed and picked up information of single permeability sand bed and other sedimentary energy. We analyzed the distribution region of underwater braided channel microfacies and the favorable shallow water channel facies and researched its relationship to reservoir distributions. Taking advantage of favorable sedimentary microfacies and their corresponding lower limit of the reservoir effective thickness, fine log re-evaluation is made for more than 60 wells of cretaceous system in this area. And newly discovered reservoir effective thickness is 32. 0 m for cretaceous system K1s1 period, 21. 0 m for Kls2 period. This method provides a reliable basis for the oilfield potential reserves increment.