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Fast inversion of array laterolog measurements in an axisymmetric medium
Applied Geophysics ( IF 0.7 ) Pub Date : 2020-04-06 , DOI: 10.1007/s11770-019-0767-0
Song Hu , Long Chen , Jin Wang

The array laterolog is an important tool for complex formation logging evaluation due to its high resolution and large detection depth. However, its logging responses are seriously affected by leakage events due to the surrounding rock and by mud invasion. These factors must be considered when inverting array lateral logging data, so that the inversion results reflect the true formation conditions as much as possible. The difficulties encountered in the inversion of array lateral logging data are: too many inversion parameters cause the calculation of the Jacobian matrix to be difficult and the time required to select the initial inversion values due to the slow forward-modeling speed. In this paper, we develop a fast processing method for array laterolog data. First, it is important to clearly define the main controlling factors for the array laterolog response, such as thickness, the surrounding rock, and invasion. Second, based on a depth-window technique, processing the array laterolog data for the entire well is transformed into multiple 2D inversions of the layers using a series of continuous depth windows. For each formation in a depth window, combined with the 1D equivalent fast-forward algorithm, rapid extraction of the radial resistivity profile of the formation is achieved. Finally, the 1D inversion result is used as the initial state to further eliminate the influence of surrounding rocks and layer thicknesses on the apparent resistivity response. Numerical simulation results show that the factors affecting the response of the array laterolog are the invasion properties, the layer thicknesses, and the surrounding rocks; the windowing technique greatly reduces the number of inversion parameters needed and improves the inversion speed. A real application of the method shows that 2D inversion can rapidly reconstruct the actual resistivity distribution and improve the accuracy of reservoir saturation calculations.

中文翻译:

轴对称介质中阵列测井法测量的快速反演

阵列测井仪具有高分辨率和大探测深度,是进行复杂地层测井评估的重要工具。然而,由于周围岩石和泥浆的侵入,其测井响应受到泄漏事件的严重影响。在反演阵列横向测井数据时必须考虑这些因素,以便反演结果尽可能反映真实的地层条件。在对阵列横向测井数据进行反演时遇到的困难是:反演参数太多会导致雅可比矩阵的计算变得困难,并且由于慢速的正向建模速度会导致选择初始反演值所需的时间。在本文中,我们开发了一种用于阵列测井数据的快速处理方法。第一,重要的是,明确定义阵列后测响应的主要控制因素,例如厚度,围岩和侵入。其次,基于深度窗口技术,使用一系列连续的深度窗口将整个井的阵列测井数据处理转换为层的多个2D反演。对于深度窗口中的每个地层,结合一维等效快进算法,可以快速提取地层的径向电阻率曲线。最后,将一维反演结果用作初始状态,以进一步消除围岩和层厚度对视电阻率响应的影响。数值模拟结果表明,影响阵列测井响应的因素有:侵入特性,层厚,和周围的岩石;窗口技术大大减少了所需的反演参数数量,并提高了反演速度。该方法的实际应用表明,二维反演可以快速重建实际电阻率分布,提高储层饱和度计算的准确性。
更新日期:2020-04-06
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