High-maturity-over-maturity shale gas content evaluation method based on alkane carbon isotope inversion

Abstract

The invention discloses a high-maturity-over-maturity shale gas content evaluation method based on alkane carbon isotope inversion. The method is suitable for a high-maturation-over-maturation shale and comprises the following steps: carrying out a shale core on-site desorption experiment of a typical shale gas well in a block, and determining the shale gas content; separating out two alkanes in the desorbed gas, measuring carbon isotopes of the two alkanes, calculating a carbon isotope difference value of the two alkanes, and then establishing a fitting formula between the carbon isotope difference value of the two alkanes and the shale gas content; collecting well mouth gas or desorption gas of adjacent wells or adjacent block shale gas wells, measuring isotopes of the two alkanes, and substituting the isotopes into a fitting formula to calculate the shale gas content. The method has the advantages that the principle is reliable, the influence of the rock core is avoided, the implementation cost is low, the accuracy of shale gas content evaluation can be effectively improved, particularly, when a thick shale layer section is developed, great economic advantages can be achieved, and the method has the characteristics of being easy to popularize and convenient to implement.

Description

technical field [0001] The invention relates to a shale gas content evaluation method, in particular to a highly 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 that occurs in organic-rich mud shale and its interlayers. It mainly exists in adsorption and free states. It is mainly composed of methane and contains a small amount of ethane, propane and butane. It is recognized as clean energy. Because shale gas has huge resource potential, it has been considered as a major discovery of natural gas exploration in the 21st century. In recent years, China has vigorously promoted the exploration and development of shale gas, and has achieved many major breakthroughs. Among them, the exploration and development of highly mature-over-mature shale gas in the Longmaxi Formation in the Sichuan Basin has ...

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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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