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This paper describes the development and results obtained from an encapsulated surfactant pilot designed to deal with liquid loading in gas wells located in Centenario field in Neuquén province of Argentina, which is a mature field in an urban area. Due to the field location, subsurface valves were installed into tubing during 2010-2017 to prevent possible blowouts, hence capillary string, which was a proven technology to deal with liquid loading, was discarded. To deal with liquid loading and production losses, Pluspetrol and SUEZ (the chemicals & services provider company) developed field application of a new technology of encapsulated surfactant that consists of an inert carrier soaked with liquid active chemical. This product allows constant dosage for a long period of time eliminating the need of installing a capillary string inside the well. Due to the architecture of the wells and commingled production, liquid loading problems and unstability started at rates of 30 Mm3/d, leaving 30% of the well remaining recoverable resources unproduced. These issues were dealt with successfully using capillary strings until 2010, when urbanization of the productive area made it necessary to install subsurface valves. From then on, production stability was affected, losing up to 70% of it in several zones. The pilot consisted of five wells. Candidates were selected using dynamic gradients and telemetry systems to evaluate liquid loading, confirmed by unstable production and favorable response to shut-ins. The project is currently in test phase. It was carried out initially in one well with a 100% increase in daily production, as well as high stability of gas and liquid production. The liquid level in wells, solid surfactant concentration and liquid rates were considered to estimate the treatment duration. Wellhead telemetry and physical measurements such as dynamic gradients, allowed an accurate analysis of results. Measurements during the treatment showed a pressure reduction of 7 kg/cm2 in front of the perforations, compared to the best production conditions of the well before liquid loading. In addition, four more wells were treated similarly, and by the time this work is presented only have preliminary results are obtained. In order to evaluate this project continuous flow meters are being used. In case these positive results remain, it is expected that this application will be expanded to more than 40 wells. Using encapsulated surfactant implies several advantages. One of them is the possibility to run physical measurements during treatment in order to continuously evaluate its performance and pressure change. In addition, the absence of a capillary string allows the treatment to be held on wells with complicated production systems, such as velocity strings, diameter reductions, or subsurface valves diminishing operative risks. Another positive feature is to avoid installing pumps and chemical recipients at the location, making this suitable for urban fields. Last but not least, the technology price is lower than others, resulting in an attractive solution. |
