A New Method for Calculating the Influx Index in Gas-Drive Reservoirs: A Case Study of the Kela-2 Gas Field

Donghuan Han (), Tongwen Jiang, Wei Xiong, Shusheng Gao, Huaxun Liu, Liyou Ye, Wenqing Zhu and Weiguo An
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Donghuan Han: University of Chinese Academy of Sciences, Beijing 100049, China
Tongwen Jiang: Department of Science and Technology Management, PetroChina Company Limited, Beijing 100007, China
Wei Xiong: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Shusheng Gao: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Huaxun Liu: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Liyou Ye: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Wenqing Zhu: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Weiguo An: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China

Energies, 2024, vol. 17, issue 5, 1-23

Abstract: The calculation of the influx index is one of the most contentious issues in dynamic reserve evaluation of gas reservoirs’ development. For the influx index, it is key to obtain information on the pore compressibility coefficient under realistic gas reservoir pressure. So far, little is known about the assessment of the pore compressibility coefficient at a laboratory scale. Here, we combine observations of gas flowmeter, ISCO booster pump, intermediate container, and rock samples to quantify the pore compressibility coefficient from the KL2-13 well in the Kela-2 reservoir. Additionally, the iterative method (combined the static and dynamic methods) is proposed based on the experimentally obtained pore compressibility coefficient ( C f ), dynamic reserve ( G ), water body multiple ( β ), and material balance equation to calculate the influx index. The combined iterative method adjusts the values of G and N by comparing the results of the static and dynamic methods, and iteratively corrects C f using a binary search method until the results of the static and dynamic methods are consistent. The results of our study reveal that the influx index calculated by the dynamic and static methods was consistent, and the gas production per unit pressure drop matched the actual production. These results strongly suggest that there exists a correlation between formation pressure and the influx index, wherein the latter exhibits a gradual decrease as the former decreases. Conversely, the displacement index of both the rock and connate water do not demonstrate a significant dependence on pressure. Furthermore, the impact of pressure on the pore compressibility factor and reservoir water compressibility factor appears to be minimal. These findings hold substantial implications for understanding the behavior of gas reservoirs under varying pressure conditions.

Keywords: influx index; Kela-2 reservoir; pore compressibility coefficient; dynamic reserve (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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