Aquifer Gas Injection Offers an Alternative for Handling Associated Gas Produced from Deepwater Fields

摘要

The shift of hydrocarbon exploration and production torndeepwater has required new approaches to field development.rnFloating production structures provided a method to producernoil and transport it to market via tanker. However, handlingrnthe associated gas represents a new challenge.rnThis paper considers the viability of storing producedrnassociated gas in an aquifer for recovery at some future time.rnA simulation study was conducted with a hypotheticalrnsandstone aquifer in an anticlinal trap. Five years of injectionrnwere simulated followed by five years of production (storedrngas recovery). Particular attention was given to the role ofrnrelative permeability hysteresis in determining trapped gasrnsaturation which tends to control the efficiency of the storagernprocess. Various cases were run to observe the effect ofrnlocation of the injection/production well.rnThe results indicate that it is technically feasible to recover gasrninjected into an aquifer, provided the aquifer exhibits thernappropriate structure, size and permeability. However, morernthan half of the stored gas is lost due to trapped gas saturationsrnand high water saturations with corresponding low gas relativernpermeabilities. During the production (recovery) phase, it canrnbe expected that water-gas production ratios will be high.rnWell location has a role in recovery efficiency, but is not asrnimportant as the relative permeability effects. The economicrnlimit of stored gas recovery will be greatly affected byrnproducing water-gas ratios, especially at great depth. For arnspecific prospect for gas storage in an aquifer, special lab testsrnshould be done to exam the imbibition process. An economicrnanalysis should then be tied to an accurate simulation of thernprospect.