How to realize an air-injection well with constant bottom-hole pressure?
Dear all,
I am using the EOS3 module to simulate the injection of air into a confined aquifer via a fully penetrating well. In order to prevent potential damage to the rock formation, the pressure within the model domain must be kept below 60 bar at all times. Despite this constraint, the goal is to inject as much air as possible. To achieve this, it is desirable to maintain a constant bottom-hole pressure of 60 bar. However, I am unsure of the best method for achieving this.
Any suggestions would be greatly appreciated.
Thanks,
Xin
2 replies
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I'm afraid there is no explicit option in TOUGH2 to simulate injection with constant BHP. One possible approach could be to simulate the wellbore explicitely in the discretisation grid, make wellbore elements inactive (infinite volume), and assign initial conditions corresponding to the gas phase you intend to inject: single-gas conditions with almost all air, P=60 bar and the evaluated BHT of injected air.
In this way you cannot control the air injection rate which likely will decline with the buildup of P in the acquifer. Injection rates can be found looking at the gas phase flux along the connections among wellbore elements and aquifer elements.
Extremely high air injection rates could be obtained just at the beginning because of the P difference between the borehole and surrounding aquifer. You might control the wellbore P by injecting air into the wellbore elements at variable rates in such a way to obtain a given P increase within the wellbore. The way to do that was explained by Karsten Pruess and reported in both Petrasim and TOUGH3 (pag.32) user's guides.
Regards,
Alfredo