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我国东部大多数油田已进入注水采油阶段 ,注入水侵入储集层 ,造成电导率异常 ,给测井解释带来困难。目前 ,采用电磁波测井仪器测量相位差和幅度比 ,利用近似公式将其转换为视电导率和视介电常数 ,再通过图版校正 ,即可得出地层的真电导率和真介电常数 ,使得定量解释的精度得到提高。然而这种图版校正法存在一定的局限性 ,尤其对于薄层 ,由于井眼、围岩及侵入影响的紧密耦合性 ,使得逐次图版校正方法失去作用 ,甚至可能得出错误的结果。因此 ,基于电磁场Maxwell方程的反演方法成为当前电法测井研究的焦点。文中正演采用数值模式匹配方法 ,利用47MHz电磁波测井的相位差和幅度比曲线 ,给出了反演地层真电导率及介电常数的一种快速迭代反演方法。通过对一个 8层模型的无噪声和有噪声数据的反演考查 ,以及通过实际井的反演结果验证 ,其反演结果与模型的响应曲线及实际曲线均吻合较好 ,表明此方法能有效地克服井眼、注入水侵入和邻层的影响 ,所测得的电导率和介电常数接近地层的真实性。该方法精度高 ,应用方便 ,处理油田实际资料效果较好。
Most of eastern China’s oilfields have entered the waterflooding and oil recovery stage, infusing water into the reservoirs, resulting in abnormal conductivity, which makes logging interpretation difficult. At present, using electromagnetic wave logging instrument to measure the phase difference and amplitude ratio, using the approximate formula to convert it to apparent conductivity and apparent dielectric constant, and then through the plate correction, we can get the formation of true conductivity and true permittivity, Making quantitative interpretation of the accuracy is improved. However, this method of plate calibration has some limitations. Especially for the thin layer, the correction method of successive calibration plates is ineffective due to the close coupling of wellbore, surrounding rock and intrusion effects, and may even lead to erroneous results. Therefore, the inversion method based on Maxwell equation of electromagnetic field becomes the focus of current electrical logging. In this paper, a numerical iteration method based on numerical mode matching is used to predict the true conductivity and dielectric constant of the stratum by using the phase difference and amplitude ratio curves of 47MHz electromagnetic wave logging. The inversion of the noise-free and noisy data of a 8-layer model and the validation of the actual well inversion results show that the inversion results are in good agreement with the model response curve and the actual curve, indicating that this method is effective Overcome the impact of wellbore, injection of water and adjacent layers, the measured conductivity and dielectric constant close to the authenticity of the formation. The method has the advantages of high precision, convenient application and good effect on the actual data of the oilfield.