Polymeric Gel Treatment for Water Shutoff – A Case Study

Production from several matured oil and gas fields is impacted by high water cut. Common causes of excess water production in wells are coning, inflow through fractures and poor cement quality behind casing. Operators always aim at increasing the recovery of oil and gas and prolong well life in the absence of or negligible water cut. Polymeric gel system is a clear fluid formulated with low-molecular-weight polymer which allows penetration into matrix pore spaces for complete shut-off. Its low viscosity prior to crosslinking aids its injectivity; after placement in small openings such as pore throats and channels in cement behind casing, the final product is a rubber-like ring gel which penetrates formation matrix to reduce permeability and eventual shut-off flow. This paper focuses on the application of polymeric gel solution designed to shut off water production in two wells in Niger Delta. The candidate wells were carefully selected following a comprehensive review of the well schematic, petrophysical information and the reservoir performance monitoring logs. Based on the results of the data analyzed, polymer gel system was recommended. The required laboratory tests were conducted to confirm gelation time prior to field deployment. Coiled tubing and thru tubing inflatable packer were the preferred deployment method for precise treatment placement. The wells were shut-in for five days and surface samples were collected and kept in the water bath under downhole temperature conditions to allow curing of the treatment. The wells were opened after the curing time, and pressure tested against cured treatment system downhole and held for 10mins. The positive results from the pressure tests in both wells showed that total shut-off of the existing perforations were successful. The wells were thereafter re-perforated at shallower depths and production sustained on both wells.