裂缝型储层流动单元划分方法研究:以鄂尔多斯盆地姬塬地区长811储层为例

摘要

测井曲线R/S分析能够有效地表征储层裂缝发育程度.以往研究中单独运用声波曲线进行R/S分析并不能规避岩性变化对声波曲线的影响.采用重构曲线( AC - GR)进行R/S计算,能够有效地反映裂缝发育程度和位置.另外,统计表明裂缝发育层段裂缝密度同重构曲线的分形维数D平均值有很好的相关性.因此,在划分流动单元过程中,除选取常用的孔隙度、渗透率、有效厚度等参数外,还选取重构曲线(AC-GR)的分形维数D进行综合聚类分析.以鄂尔多斯盆地姬塬地区长811储层为例,按其综合渗流能力将其划分成4类流动单元:第1类主要位于主河道汇流处,基质物性好,有效厚度大,裂缝较发育；第2类主要位于主河道,有效厚度较大,裂缝发育程度一般；第3类位于河道侧翼,有效厚度小,裂缝发育；第4类零星分布,基质物性较差,裂缝不发育,总体呈北东—南西向展布.%Previous studies showed that R/S analysis of well logs can effectively characterize the degree of reservoir fractures. But R/S calculation only using acoustic curves cannot avoid the influence of lithology changes. In this paper, R/S calculation using the reconstructed curves ( AC - CR) could remove the influence of lithology changes on acoustic curves and could reserve the response of fractures. In this way, R/S analysis of reconstructed curves (AC - GR) can much effectively characterized the development and location of fractures. Statistics showed that the relationship between fracture density and fractal dimension ( D) of reconstructed curves (AC -GR) was good. In this study on dividing the flow units, in addition to the commonly used parameters, i. e. porosity, permeability and effective thickness, the fractal dimension (D) of reconstructed curves (AC -GR) was also used in the method of cluster analysis. Taking the first oil layer in the eighth member of the Yanchang Formation in Jiyuan area of Ordos basin as an example, four types of flow units were defined according to the comprehensive flow ability. The first type was located in the confluence of main channel where the reservoir property and the effective thickness were high and the fractures were developed. The second was located in the main channel where the effective thickness was high and fractures were developed moderately. The third was located in the river flank where the effective thickness was low and fractures were developed. The fourth was spo-radically distributed along the northeast-to-southwest direction in the areas where the reservoir property was hotrngood and fractures were not developed.