Technical Paper: Preventive treatment for enhancing water removal from gas reservoir by wettability alteration

Society: SPE
Paper Number: 105367
Presentation Date: 2007
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Water blocks and condensate drop out near the wellbore in a gas reservoir can cause rapid production decline. The liquid (water/condensate) is trapped near the wellbore due to strong capillary forces and/or viscous fingering of gas through the liquid. To remove this liquid, alcoholic solvents are injected into the near wellbore area; however, this remedial solution needs to be reapplied in case of any subsequent water or condensate banking in the well. In this paper, we present a preventive and permanent chemical treatment for the removal of water and condensate blocks. Three types of tests have been conducted to evaluate the performance of the chemical system which include contact angle, imbibition and core flow test. A total of 41 chemicals have been tested using contact angle and imbibition tests and only 2 chemicals, A5 and A6 were selected for core flow test as they were stable at high temperature and did not damage the cores excessively during the imbibition tests. The core treated with a solution containing 5% A5 and 95% brine (2-wt% KCl) in the core flow test gave higher clean up of trapped water due to reduction in capillary force. This treatment system also shows a better alteration of the formation wettability from liquid wet to non-liquid wet conditions compared to the other chemical systems tested.