Acidizing of Gas Wells

by
Oyetunde Olajide Fadele, MSE

University of Texas at Austin, 2000
Supervisor: A.D. Hill

The apparent skin measured during the real time monitoring of gas wells is found to be abnormally high. A viscous effect (Economides et al, 1994) on the skin has been found to explain this phenomenon. Diversion occurs in the acid treatment of gas wells encountering multiple layers. In gas wells, when a residual gas saturation occurs behind the acid phase, the penetration of injected acid is affected. The objective in this project is to develop models based on the above phenomena and implement them in acidizing software for real time monitoring (UTRTM) and for simulation (UTMAST).

Algorithms for the real-time monitoring of gas wells, for viscous skin calculation in both single and multiple stage injection have been developed and implemented in the UTRTM program. The viscosity ratio of injected fluid to reservoir fluid controls the importance of viscous skin in acidizing treatment interpretation. Based on the results of a study of acid penetration in gas reservoirs with the UTMAST program, live acid penetrates deeper in gas wells due to the presence of residual gas, as compared with single-phase flow. From applying an acidizing model (Hill and Rossen, 1994) to gas wells in multi-layer formations, it is concluded that viscous diversion is effective when layers are of similar permeabilities, but not so when layers have a marked difference in permeability.

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