倾斜电各向异性地层阵列感应测井数据处理新方法

A new data processing method of array induction logging for inclined electrical anisotropic formation

阵列感应测井的原始信号经软件聚焦算法处理后可提供多种分辨率、不同探测深度的电阻率信息,这使得阵列感应测井成为复杂油气层测井评价的重要手段。然而,当在深层致密储层和非常规储层等电各向异性储层中采用斜井进行钻探时,由于传统软件聚焦算法没有考虑地层倾斜及其电各向异性的影响,常规阵列感应测井输出结果的适用性受到极大挑战,其电阻率曲线常出现钻井液假侵入、曲线乱序等异常现象。针对这一问题,提出以未聚焦的原始电阻率为约束,在已知仪器与地层相对夹角和目的层电各向异性系数的前提下,通过建立层状地层模型,结合仪器的正演算法模拟电阻率响应特征并与实测电阻率曲线进行误差比较,不断修改模型以进行迭代循环计算,从而得到等效的水平电阻率和垂直电阻率阵列感应测井曲线。该方法有效地剔除了地层倾角及其电各向异性的影响,且进一步通过分辨率匹配处理可获得具有给定分辨率、能完全保留钻井液侵入特征的地层水平方向和垂直方向的阵列感应电阻率曲线,显著提高了复杂储层的电阻率测量精度和测井解释符合率。相关算法得到了理论模型和多口实际测井资料的验证。

After being processed by software focusing algorithm,the original signals of array induction logging can provide resistivity information of multiple resolutions and various detection depths.For this reason,array induction logging has become an important logging evaluation technique for complex oil and gas reservoirs.However,when deviated well are used for drilling in electrical anisotropic reservoirs such as deep tight reservoirs and unconventional reservoirs,since conventional software focusing algorithm does not take into account the impact of inclination and electrical anisotropy of formation,it is a great challenge to apply the output results of conventional array induction logging in actual fields,and the resistivity curve often has abnormalities such as false invasion of drilling fluid and curve disorder.To address this problem,this paper puts forward to build a layered formation model with non-focusing original resistivity as constraint and under the premise of knowing the relative angle between the instrument and the formation,as well as the electrical anisotropic coefficient of the target stratum.The resistivity response characteristics were simulated by the forward algorithm of the instrument and the error was compared with the measured resistivity curve.Iterative calculations were performed by modifying the model until equivalent horizontal and vertical resistivity array induction logging curves were obtained,which has significantly improved the resistivity measurement precision and the coincidence rate of logging interpretation for complex reservoirs.The relevant algorithms are validated by theoretical models and practical drilling data.