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Description:
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The shift of hydrocarbon exploration and production to deepwater has resulted in new opportunities for the petroleum industry (in this project , the deepwater depth greater than 1 ,000 ft ) but also , it has introduced new challenges . In 2001 ,more than 999 Bcf of associated gas were produced from the Gulf of Mexico , with deepwater associated gas production accounting for 20 % of this produced gas . Two important issues are the potential environmental impacts and the economic value of deepwater associated gas . This project was designed to test the viability of storing associated gas in a saline sandstone aquifer above the producing horizon . Saline aquifer storage would have the dual benefits of gas emissions reduction and gas storage for future use . To assess the viability of saline aquifer storage , a simulation study was conducted with a hypothetical sandstone aquifer in an anticlinal trap . Five years of injection were simulated followed by five years of production (stored gas recovery ) . Particular attention was given to the role of relative permeability hysteresis in determining trapped gas saturation , as it tends to control the efficiency of the storage process . Various cases were run to observe the effect of location of the injection /production well and formation dip angle . This study was made to : (1 ) conduct a simulation study to investigate the effects of reservoir and well parameters on gas storage performance ; (2 ) assess the drainage and imbibition processes in aquifer gas storage ; (3 ) evaluate methods used to determine relative permeability and gas residual saturation ; and (4 ) gain experience with , and confidence in , the hysteresis option in IMEX Simulator for determining the trapped gas saturation .
The simulation results show that well location and dip angle have important effects on gas storage performance . In the test cases , the case with a higher dip angle favors gas trapping , and the best recovery is the top of the anticlinal structure . More than half of the stored gas is lost due to trapped gas saturations and high water saturation with corresponding low gas relative permeability . During the production (recovery ) phase , it can be expected that water -gas production ratios will be high . The economic limit of the stored gas recovery will be greatly affected by producing water -gas ratio , especially for deep aquifers . The result indicates that it is technically feasible to recover gas injected into a saline aquifer , provided the aquifer exhibits the appropriate dip angle , size and permeability , and residual or trapped gas saturation is also important . The technical approach used in this study may be used to assess saline aquifer storage in other deepwater regions , and it may provide a preliminary framework for studies of the economic viability of deepwater saline aquifer gas storage . |