Water Shutoff in Gas Wells: Proper Gel Placement Is the Key to Success

Abstract

Summary The objectives of water-shutoff 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 highmolecular-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 semistable foam rather than with gas. Such displacement allows for improved gas production after the gel treatment. Laboratory-scale simulations were used to history match the coreflood results to calibrate the gelation and overdisplacement 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 for combatting 3D coning situations. This overdisplacement technique can also minimize the startup problems experienced in fractured gas reservoirs after gel treatments.