Water Shut-Off in Gas Wells: Proper Gel Placement is the Key to Success

Abstract

Abstract The objectives of water shut-off treatments in gas wells suffering from water influx are to reduce water production and at the same time increase gas production rates and producible gas reserves. Several field treatments, conducted under the umbrella of a research project focused on water abatement in gas wells, have demonstrated that a sequential gel/gas injection technique in fractured gas reservoirs was successful in reducing water production and increasing gas production. Further efforts focused on improving gel placement in both fractured and matrix reservoirs to improve the treatment efficiency. Injectivity of the gelant was improved for injection into matrix reservoirs by either reducing the concentration of the high molecular weight polymer in the gelant formulation or by using a low molecular weight polymer.Gel placement was improved by displacing the gelant away from the near wellbore region with semi-stable foam rather than with gas. Such displacement allows for improved gas production after the gel treatment.Lab scale simulations were used to history-match the coreflood results to calibrate the gelation and over-displacement options in the simulations.Field scale simulations demonstrated the merits of the proper gel placement technique using a foam to displace the gelant away from the wellbore in matrix and fractured reservoirs. Optimized gel formulations in combination with the new over-displacement technique provide a treatment alternative to combat 3-D coning situations. This over displacement technique can also minimize the start-up problems experienced in fractured gas reservoirs after gel treatments.