基于岩石物理相的储层非均质性研究:以昆北油田切12井区E_3~1为例

Reservoir Heterogeneity Based on Petrophysical Facies:A Case Study on E_3~1 in Qie12 Block of Kunbei Oilfield

昆北油田切12井区E_3~1主要是一套近源且位于不整合面上的辫状河三角洲相沉积,岩性主要为含砾砂岩和砂砾岩,由于受沉积环境、成岩作用、构造等因素的影响,岩性复杂、成熟度低、分选差、孔隙结构具有多重性、有效储层与非有效储层混杂、储层非均质性极强,因此,采用了更精细的岩石物理相对储层非均质性进行了研究。以岩性资料、测井资料及其解释成果为基础,选取了反映沉积、成岩、构造作用的自然伽马、自然电位、声波时差、密度和裂缝孔隙度5个参数,运用加权平均法计算了反映岩石物理相的综合评价系数。在此基础上,采用逐点岩石物理相综合评价系数,运用变异系数法对储层非均质性进行了计算,按照变异系数值大小将工区储层非均质性分为3类:第Ⅰ类弱非均质性,变异系数≤0.2;第Ⅱ类中等非均质性,变异系数在0.2～0.4之间;第Ⅲ类强非均质性,变异系数>0.4。根据这个标准对储层平面非均质性进行了评价。

The E3~1 in Qie 12 block of Kunbei Oilfield is a mainly abraided river delta facies deposit which is near source in the unconformity surface.Its lithology is mainly pebbly sandstone and conglomerate,due to the influence of sedimentary environment,diagenesis,structure and other factors,lithology is complex,lowmaturity,poor sorting,multiple pore structure,effective reservoir and non-effective reservoir are mixed,strong heterogeneity of reservoir,This paper studies the finer petrophysical facies to solve reservoir heterogeneity based on lithologic data,logging data and its interpretation results.Five parameters of natural gamma,natural potential,interval transit time,density and fracture porosity are selected to reflect sedimentary,diagenetic,tectonic action,and the weighted average method is used to calculate the comprehensive evaluation coefficient of petrophysical facies reflected.On this basis,the comprehensive evaluation coefficient of point by point petrophysical facies is adopted,and the reservoir heterogeneity is calculated by the variation coefficient method.According to the magnitude of the coefficient of variation,the heterogeneity of the work area can be divided into three categories：the coefficient of variation of the first type of weak heterogeneity less than or equal to 0.2;the coefficient of variation for second types of medium heterogeneity between 0.2 and 0.4;and the coefficient of variation of the third types of strong heterogeneity greater than 0.4.According to this standard,the plane heterogeneity of reservoir is predicted.