Promotion and Application of Rock Debris Gamma Spectroscopy Logging Technology

With the shift of oilfield exploration from conventional oil and gas to unconventional oil and gas such as tight oil and shale oil and gas, horizontal wells dominate the new drilling well types now. The improvement of drilling technology has led to thin and fragmented rock cuttings returning from the bottom of the well. In addition, the influence of oil-based drilling fluid on rock cuttings has brought great difficulties to traditional rock cuttings logging and reservoir interpretation and evaluation, increasing the difficulty of accurately targeting horizontal wells and maintaining high drilling encounter rates. In order to solve the problems of lithology identification, stratigraphic division, assisting geological guidance to smoothly enter the target, determining whether to drill along the formation, and reservoir interpretation and evaluation during horizontal well drilling in the Shixi syncline area in northern Guizhou, the gamma ray spectroscopy logging technology of rock debris is introduced. Energy spectrum parameters of radioactive elements such as uranium, thorium, potassium, gamma and non-uranium gamma are obtained by analyzing rock debris. According to the characteristics of shale oil and gas self-generation and high organic matter, the problems in lithology identification, stratification, drilling of horizontal wells and improving drilling rate are solved by means of the changes of energy spectrum parameters and derived parameters. A formula for calculating the total organic carbon content in the Shixi syncline area of northern Guizhou is developed by fitting the optimized uranium and gamma data of energy spectrum parameters. A shale gas interpretation template is established by combining the changes in gas logging total hydrocarbon values. Practical application has shown that this method achieves rapid interpretation and evaluation of reservoir fluids, division of strata, determination of sedimentary environment, assistance in target entry, and improvement of reservoir drilling encounter rate. This method can be applied to similar blocks.