Feasibility Study of Both Carbon Dioxide Sequestration and Underground Gas Storage Combination

摘要

Underground gas storage (UGS) is a relatively modern technique for mitigation detrimental effect of the supply-demand misbalances that has been developing rapidly and is now an essential part of the gas chain. The original and primary scope was a modulation of peak demand and the optimization of the transport network. Nowadays more specific and differentiated functions are taking over. For example, this process can also be adapted to producing oil or condensate and can be considered as an IOR method. The purpose of this study is to investigate the parameters affecting underground gas storage in gas condensate reservoirs in order to improve its performance. In this paper we considered the economic aspect of UGS and focused on engineering methods to reduce the cost of storage. This resulted in finding a new phenomenon in gas storage. Results of the study were directed toward replacing the cushion gas, which accounts for about 38% of the storage costs. Efforts for finding an appropriate alternative for cushion gas to maintain reservoir pressure in storage cycles led to recognition of CO_2 sequestration and finally with combining UGS and CO_2 sequestration the natural gas as in cushion gas replaced by CO_2 gas. In this case the natural base gas in the reservoir is drained and CO_2 sequestration begins. For improving the quality of production stream, the injection wells used for CO_2 sequestration separated from those which are used in UGS. Also CO_2 injection into lower layers delays the production of CO_2 in production times. Optimum limit for this is a place between minimizing CO_2 production and maximizing working gas capacity. Carbon dioxide has higher miscibility than natural gas that causes an approximately 1.2 STB/MMSCF CO_2 increase in condensate production. This means a 1.3% increase in condensate recovery in addition to what we could have before with natural gas. Simulation Results confirm the success of the project as well as being economical. However, 16% of injected CO_2 produces in 20 years of gas storage, but over time, CO_2 production has a decreasing trend.