A gas content evaluation method for highly mature-over-mature shale based on alkane carbon isotope inversion

Abstract

The invention discloses a highly mature-over-mature shale gas content evaluation method based on alkane carbon isotope inversion, which is suitable for high-mature-over-mature shale, comprising the following steps: developing shale cores of typical shale gas wells in the block On-site desorption experiment to measure the gas content of shale; separate two alkanes in the desorbed gas, measure the carbon isotope of the two alkanes, calculate the carbon isotope difference between the two, and then establish the carbon isotope difference of the two alkanes Fitting formula with shale gas content; collect wellhead gas or analytic gas from adjacent wells or shale gas wells in adjacent blocks, measure the isotopes of two alkanes, and substitute into the fitting formula to calculate shale gas content. The invention is beneficial in that it is reliable in principle, not affected by rock cores, low in implementation cost, and can effectively improve the accuracy of shale gas content evaluation, especially when developing for thick shale intervals, it can play a better role. It has great economic advantages and is easy to popularize and implement.

Description

technical field [0001] The invention relates to a shale gas content evaluation method, in particular to a high-mature-over-mature shale gas content evaluation method based on alkane carbon isotope inversion, and belongs to the technical field of oil and gas exploration. Background technique [0002] Shale gas is an unconventional natural gas existing in organic-rich mud shale and its interlayers, mainly in adsorption and free states, mainly composed of methane, with a small amount of ethane, propane and butane. clean energy. Due to the huge resource potential of shale gas, it has been considered as a major discovery of natural gas exploration in the 21st century. In recent years, China has vigorously promoted the process of shale gas exploration and development, and has made many major breakthroughs. Among them, the exploration and development of high-mature-over-mature shale gas in the Longmaxi Formation in the Sichuan Basin is the best. In 2018, China's shale gas product...

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Problems solved by technology

[0030] The isothermal adsorption experiment method is similar to the on-site desorption method, both of which are based on shale cores. They also have the disadvantages of difficult shale coring, high cost, and complicated experimental operations. The simple average method will reduce the gas content of thick shale. Accuracy of Evaluation Results

[0031] These two shale gas content evaluation methods are based on the analysis and testing of shale cores, which are easily affected by the fragmentation of shale cores and the limited number of cores. At the same time, they have the disadvantages of complicated experimental process and high experimental cost, especially for thick formations. When evaluating shale gas content, the simple average method usually adopted will reduce the accuracy of the final evaluation results

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