Prediction of Staged Gas Injection and Production Capacity for Underground Gas Storage in Offshore Water Injection Reservoirs - A Case Study of NanPu No.1 Gas Storage

Water injection reservoir reconstruction research of gas storage is still in its infancy, Nanpu No.1 gas storage is the first offshore oil and gas reservoir reconstruction in China, developed gas reservoirs and gas roof reservoirs, In early stage, offshore jacket was used, and in later stage, artificial islands were built and developed by water injection, Due to the restriction of exploitation conditions, oil and gas co-production, single layer gas production and productivity testing data are lacking, Effective gas phase seepage capacity, gas injection and production capacity is difficult to determine. Therefore, based on different layers’s air permeability, combined with the permeability stress sensitivity test and the relationship function of air permeability and water permeability, the water phase permeability is obtained; According to the equivalent percolation theory of multiphase flow, gas reservoir adopted the gas-water phase permeability curve, oil reservoir adopted the oil-water phase permeability curve and gas-oil phase permeability curve. Finally, the effective permeability of underground gas phase is obtained after the gas injection is stable for the reservoir under construction of the oil reservoir; Based on the steady state or quasi-steady state seepage equation, established gas and oil reservoir’ binomial productivity equations, considered node coordination, critical liquid carrying, critical erosion, critical sand production pressure difference and fluid saturation changes after gas flooding. Established prediction chart of gas injection and production capacity of gas and oil reservoir at different stages; Comprehensive analysis and optimization of tubing size and determination of reasonable gas injection and production capacity provide technical support for the preparation of Nanpu No.1 gas storage scheme. The evaluation results are consistent with the first round of gas injection, which verifies the accuracy of the method and provides reference for the construction of similar gas storage.