鄂尔多斯盆地大牛地气田三维储层精细描述

Fine description of reservoirs by the 3D stochastic modeling in the Daniudi gas field,Ordos Basin

下二叠统下石盒子组是大牛地气田低孔、低渗透岩性气藏的主要产气层之一,分析其储层的非均质性,精细描述储层的各种属性特征,是气田进一步开发的关键。为此,综合利用地质、地震、测井等各种资料,应用三维随机建模技术,根据两步法建模理论和地质统计结果,采用地震、沉积模式控制等多信息融合约束的建模方法,建立了研究区储层的沉积微相模型,精细描述了下石盒子组辫状河沉积特征,剖析了各沉积微相砂体的展布形态与叠置关系;依据相控建模方法,分析各微相下的属性分布特征,统计属性分布变密度函数,以已经建成的沉积微相模型为基础,完成各属性的随机模型,分级、分层次详细地描述储层的非均质性,并指出心滩沉积的粗砂岩、砂砾岩等为相对高孔、高渗带,是主要的产气砂体。

The Early Permian lower Shihezi Formation is one of the major payzones in the lithologic gas reservoirs with low porosity and low permeability in the Daniudi gas field,Ordos Basin.Analysis of the heterogeneity and fine description of the attributes of the reservoirs are critical to further development of this gas field.Taking all available data sources into account,we adopted the 3D stochastic modelling to built sedimentary micro-facies models for the reservoirs in the study area,described in detail the characteristics of braided river deposits in the lower Shihezi Formation,and analyzed the distribution and superimposition of sandbodies of various sedimentary micro-facies.By using the facies-controlled modeling method,we analyzed the characteristics of attribute distribution of each sedimentary micro-facies,performed statistics of variable density function of the attribute distribution,built a stochastic model for each attribute based on the sedimentary micro-facies models,and described in detail the reservoir heterogeneity.It is believed that the griststone and glutinite in channel bar deposits contribute to potential payzones because of their relatively high porosity and permeability.