A new method of deep carbonate lithology identification at the Tadong uplift in the eastern section of the Tarim Basin

摘要

The lithology identification of deep carbonate rocks has always been a difficult field of research. The deep carbonate rock formations in the eastern section of the Tarim Basin have complex tectonism, deposition, and diagenesis. Therefore, it is difficult to use conventional logging information to identify the lithology of deep carbonate rocks. In this study, a natural gamma ray spectrometry log in unconventional logging was used to discover a new method (comprehensive superposition method) for the lithology identification of deep carbonate rocks. The research results showed that the TH, U, K, and KTH information in a natural gamma ray spectrometry log can reflect the lithological characteristics of carbonate rocks extremely well. In addition, this new identification method was able to optimize the typical logging parameters which could best reflect the lithology of the carbonate rocks after analyzing the original record curve and a variety of combined curves of the natural gamma ray spectrometry. This new method could comprehensively superpose the typical logging parameters and was capable of finally quantitatively identifying the lithology of dolomite, micrite, calcarenite, and finely crystalline limestone in deep carbonate rocks, with an identification accuracy of more than 79 %. On the basis of the above research results, a special statistical method was made to analyze the typical logging parameters of natural gamma ray spectrometry and to assist and test the identification of a comprehensive superposition method, in order to improve the lithology identification accuracy. This new method for the lithology identification of deep carbonate rocks, based on a natural gamma ray spectrometry log, achieved good application effects in the eastern section of the Tarim Basin.