基于测井资料岩石物理模拟的储层识别法

Identification of reservoir by log-data-based petrophysical simulation

文中基于测井资料岩石物理模拟方法的理论分析,根据中国东部油田两口井的井资料及岩性和试油等资料,利用测井曲线环境校正→选择岩石物理模型→计算弹性参数这一流程,选择了微分等效介质和自适应岩石物理模型对两口井的纵、横波速度进行了模拟和预测。利用纵、横波速度、密度参数与弹性模量之间的关系导出纵、横波速度比、剪切模量、拉梅常数和泊松比参数,再根据不同参数的交会图和相关性分析了解岩性、孔隙和流体变化对弹性参数的影响规律,总结出研究区储层的识别依据:①含油层段在纵、横波波阻抗上和密度上表现为低值(纵、横波波阻抗值分别小于8×106(kg·m-2·s-1)和4.15×106(kg·m-2·s-1),密度小于2.28g/cm3);②含油层段泊松比一般小于0.29,当泊松比大于0.29后,含油储层与非储层发生重叠,可通过拉梅常数小于1.25×106(kg·m-1·s-2)作为控制,区分含油储层和非储层;③含油层段纵、横波速度比一般小于1.85,当纵、横波速度比大于1.85、小于2.0时,储层和非储层发生重叠,可用8×106(kg·m-2·s-1)纵波阻抗作为上限约束,识别含油储层;④纵波阻抗与自然伽马曲线交会分析表明,含油砂岩分布在55API以下、纵波阻抗小于8×106(kg·m-2·s-1)的区域。

Based on the theoretical analysis of log-data-based petrophysical simulation and according to the data of two wells in eastern oilfield of China (such as log data, lithologic and test data), the paper used such a flow as correction of logging environment→selection of petrophysical model→computation of elastic parameters and selected differential equivalent medium and adaptive petrophysical model to simulate and predict the velocities of P-and S-waves in two wells. Using the relationship between the velocities of P- and S-waves, density parameters and elastic modulus to deduce the P-to-S-waves velocity ratio, shear module, Lame constants and Poisson’s ratio parameter, and again get the rule that the variation of the lithology, porosity and fluid affects the elastic parameters according to the crossplot and correlation analysis, which yields bases of identifying reservoir in research area: ①oil-bearing strata shows low value in P- and S-wave impedances and density (the P- and S-wave impedance less than 8×106kg/m3·m/s and 4.15×106kg/m3·m/s respectively, the density less than 2.28g/cm3). ②the Poison's ratio of oil-bearing strata is less than 0.29; when Poison's ratio is greater than 0.29, the oil-bearing strata overlaps with non-reservoir, in which the Lame constants less than 1.25×106kg/m3·(m/s)2 can be used as control to differentiate oil-bearing strata from non-reservoir. ③the P-to-S-waves velocity ratio of oil-bearing strata is generally less than 1.85; when the P-to-S-waves velocity ratio is greater than 1.85 and less than 2.0, the oil-bearing strata may overlap with non-reservoir, and the P-wave impedance 8×106kg/m3·m/s can be used as upper limit constraint to identify the oil-bearing strata. ④The analysis of crossplot of P-wave impedance with natural gamma curve shows that the distribution of oil-bearing sandstone is in the area where both the value of natural gamma curve is bellow 55API and P-wave impedance is less than 8×106kg/m3·m/s.