测井曲线相关性分析及其在复杂润湿性油层识别中的应用

Correlation Analysis of Well Logs and Its Application to Identifying Pay Zones with Complex Wettability

复杂润湿性条件下,油、水层电阻率对比度低,导致流体性质识别困难。基于岩石物理基础理论及Archie公式,总结并提出了利用电阻率-孔隙度曲线相关性分析识别复杂润湿性油层的方法。考虑测井曲线分辨率匹配和泥质含量的影响,选取泥质砂岩岩石物理体积模型,利用声波时差曲线计算孔隙度,并对电阻率和孔隙度曲线分别进行归一化处理。每次计算窗长n值优选为12,对储层实现连续处理。基于鄂尔多斯盆地陇东地区81口试油井长81储层的处理结果,统计每个层段正相关系数的厚度与有效厚度的比值λ,通过试油结论标定:当λ≥60%时,判定为油层;当60%>λ>40%时,判定为油水同层;当λ≤40%时,判定为水层;油、水层识别符合率达到80.25%,为复杂润湿性油层定量识别提供一种可行的方法。

Oil and water layers have low resistivity contrast in the reservoirs with complex wettabitlity, which re- suits in the difficulty of identification of fluid property. Based on petrophysical theory and Archie formula, a method is proposed to identify oil reservoirs with complex wettability by correlation analysis between resistivity log and po- rosity log. In consideration of the influence of well log resolution and shale content, shaly sandstone bulk model is chosen for porosity calculation via acoustic log. Then after the value of calculating window is chosen as 12, continu- ous processing to the reservoir after normalization processing of resistivity and porosity curves is achieved. Accord- ing to 81 processing results of Chang 81 pay zones in Longdong area, Ordos basin, the ratio of positive relevance and total thickness is calculated in each reservoir, which is named after A. On the strength of 81 oil test results, the fol- lowing conclusions can be drawn. The reservoirs are estimated as pay zones, oil and water layers, water layers when A is greater than 60% , between 40% and 60% , lower than 40% respectively. The accuracy rate reaches 80. 25% and the effectiveness is demonstrated. This method is considered as an available one to fluid property identification in formation complex wettability.