Fractured formations are strongly heterogenous, and thus exhibit a complex logging response mechanism. By using the logging while drilling (LWD) resistivity imaging tool, fractures can be visually identified and their aperture quantitatively calculated. Because physical fracture model simulation is time consuming and costly, we propose using a 3D finite element method (FEM) numerical simulation to interpret the LWD resistivity imaging tool logging responses in conjunction with a new aperture calculation model based on the forward model. First, we used the single fracture model to investigate the effect of fracture aperture and formation resistivity contrast on the maximum current contrast at the fracture. The results showed that the aperture is linearly related to the maximum current contrast, while the formation resistivity contrast exhibits a pronounced exponential relationship with the maximum current contrast. Both of these relationships are affected by the fracture's dip angle, so segmented fitting is required when the fracture dip angles differ. Next, using the forward model, we developed the fracture aperture calculation model based on the maximum current contrast. The aperture calculation model was established in three segments in accordance with the different fracture dips, and the influence factors affecting the fracture inverting inclination were analyzed using multi-fracture simulation images. Finally, the accuracy of the new model was verified with the simulated fracture images. The novel model for calculating fracture aperture is of great significance for processing and interpreting LWD resistivity imaging logging data.

中文翻译：

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基于数值模拟的随钻测井电阻率成像数据定量评价裂缝孔径

裂缝地层非均质性强，表现出复杂的测井响应机制。通过使用随钻测井（LWD）电阻率成像工具，可以直观地识别裂缝并定量计算其孔径。由于物理裂缝模型模拟耗时且成本高，我们建议使用 3D 有限元法 (FEM) 数值模拟结合基于正演模型的新孔径计算模型来解释随钻测井电阻率成像工具测井响应。首先，我们使用单裂缝模型研究了裂缝孔径和地层电阻率对比对裂缝处最大电流对比的影响。结果表明，孔径与最大电流对比度呈线性关系，而地层电阻率对比与最大电流对比表现出明显的指数关系。这两种关系都受到裂缝倾角的影响，因此当裂缝倾角不同时，需要进行分段拟合。接下来，利用正演模型，我们开发了基于最大电流对比度的裂缝孔径计算模型。根据裂缝倾角的不同，分三段建立孔径计算模型，利用多裂缝模拟图像分析影响裂缝反转倾角的影响因素。最后通过模拟裂缝图像验证了新模型的准确性。