Study of Gas Injection Effects on Rock and Fluid of a Gas Condensate Reservoir during Underground Gas Storage Process

Abstract

Abstract Underground gas storage (UGS) is a common activity in countries with major transport and distribution gas pipeline infrastructures, which allows to efficiently resolving demand seasonality problems. Natural gas injection and storage in depleted gas condensate reservoirs is a common challenge in downstream petroleum industrial jobs. Generally the gas condensate depletion process take places partially, hence the injected light natural gas into the proportionally heavier condensates lead to remarkable changes in gas relative permeability and condensate saturation. These variations affect gas production directly. In this work, UGS was studied on a gas reservoir through compositional simulator. The oil field under study is a gas condensate reservoir located in central Iran. A synthetic model of the gas condensate reservoir was generated which investigates the effect of natural gas injection and production upon variations in gas relative permeability and condensate saturation within near and far away areas of the wellbore. Before natural gas injection and production cycles begin to implement, storage able gas volume and base gas in place volume are calculated through volumetric and material balance methods to determine the optimum pressure for the first injection. It was found that both condensate saturation and gas relative permeability were sensitive to injection rate. The results on gas relative permeability suggest that gas productivity curtailed by condensate drop out can be somewhat restored by increasing injection and production cycles. Injection of higher volumes of gas in the first cycle prevents condensate from forming and increases gas productivity index.