Correction method and application of high natural gamma curve with variable weight

Abnormal high value features of natural gamma curve caused by high radioactive material in local sandstone lead to the fact that the sandstone and mud stone cannot be distinguished accurately by natural gamma curve. Meanwhile, the misconception on the geological law of hydrocarbon reservoirs will be eventually caused without the original natural gamma corrected natural gamma spectrum, formation element capturing spectrum, etc. Therefore, a new method of reconstructing natural gamma curve with variable weight is proposed based on spontaneous potential, natural gamma and formation den sity. After the process of baseline drift correction of spontaneous potential curve, caliper environment correction of natural gamma, and spontaneous potential, natural gamma and formation den sity will be normalized and used as independent variables. The method is applicable to the correction of abnormal high value features of natural gamma curve caused by the abnormal local enrichment of uranium, thorium and potassium in sandstone. The application effect in Triassic Chang 6 oil reservoir of Ordos basin indicates that this method can effectively overcome the problem of sandstone omission of original natural gamma for the abnormal high content of thorium and uranium, which can greatly enhance the distinguishing accuracy of sandstone identification.