Plunger lift is a well-known artificial lift technique originally developed for the de-liquefaction of gas wells. However its use has been extended to include high Gas – Oil Ratio (GOR) oil wells, those with low or no production due to paraffin and scale deposits and wells with high or fluctuating sales line pressures. It is an intermittent production technique that utilizes reservoir energy stored in the gas phase to lift oil from the bottom of the well to surface via the vertical cyclic action of a "pigging" device within the tubing. This action enhances the production performance of liquid loaded wells.

In this study, plunger lift systems on two wells were evaluated to determine well performance and to optimize production rates if plunger lift systems were to be installed on other wells. Casing and tubing pressure trends were used to identify operational deficiencies and causes. Vogel's model was used to model the inflow performance relationship using bottom-hole pressure data. The Foss and Gaul model for plunger lift operation was used to determine production rates and gas requirement for each well in order to optimize well performance. The mode of operation with the current settings (long after-flow periods and over-estimation of plunger fall back time) is representative of intermittent lift with the assistance of a plunger rather than gas assisted plunger lift operation. The GOR for both wells are too low for efficient operation and a model of the current settings indicates that a gas injection rate of 450 MSCF/D is required to obtain an optimum oil production rate of 103 bopd. These plunger lift systems also prevent paraffin accumulations in the production tubing of these two wells.

New plunger lift operating variables such as casing valve opening and closing time, gas injection rate, after flow time, plunger rise velocity and fallback time, flow-line motor valve cycle time and number of cycles per day were modeled to obtain an optimum oil production rate. The results showed that a gas injection rate of 173 MSCF/D is required to obtain an oil production rate of 195 BOPD for a plunger rise velocity between 800 to 1000 ft/min. For these new settings the gas requirement was reduced by 61 % and the oil production increased by 89 %. These results indicate that the modification of the operating variables can effectively optimize gas assisted plunger lift systems that are installed in the oil wells producing from the Cruse Formation in the Main Soldado field offshore the Southwest coast of Trinidad.

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