Water alternating enriched gas injection to enhance oil production and recovery from San Francisco Field, Colombia
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The main objectives of this study are to determine the most suitable type of gas for a water-alternating-gas (WAG) injection scheme, the WAG cycle time, and gas injection rate to increase oil production rate and recovery from the San Francisco field, Colombia. Experimental and simulation studies were conducted to achieve these objectives. The experimental study consisted of injecting reconstituted gas into a cell containing sand and "live" San Francisco oil. Experimental runs were made with injection of (i) the two field gases and their 50-50 mixture, (ii) the two field gases enriched with propane, and (iii) WAG with the two field gases enriched with propane. Produced oil volume, density, and viscosity; and produced gas volume and composition were measured and analyzed. A 1D 7-component compositional simulation model of the laboratory injection cell and its contents was developed. After a satisfactory history-match of the results of a WAG run, the prediction runs were made using the gas that gave the highest oil recovery in the experiments, (5:100 mass ratio of propane:Balcon gas). Oil production results from simulation were obtained for a range of WAG cycles and gas injection rate. The main results of the study may be summarized as follows. For all cases studied, the lowest oil recovery is obtained with injection of San Francisco gas, (60% of original oil-in-place OOIP), and the highest oil recovery (84% OOIP) is obtained with a WAG 7.5-7.5 (cycle of 7.5 minutes water injection followed by 7.5 minutes of gas injection at 872 ml/min). This approximately corresponds to WAG 20-20 in the field (20 days water injection followed by 20 days gas injection at 6.8 MMSCF/D). Results clearly indicate increase in oil recovery with volume of the gas injected. Lastly, of the three injection schemes studied, WAG injection with propane-enriched gas gives the highest oil recovery. This study is based on the one-dimensional displacement of oil. The three-dimensional aspects and other reservoir complexities that adversely affect oil recovery in reality have not been considered. A 3D reservoir simulation study is therefore recommended together with an economic evaluation of the cases before any decision can be made to implement any of the gas or WAG injection schemes.
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Includes bibliographical references (leaves 169-171).
Issued also on microfiche from Lange Micrographics.
Rueda Silva, Carlos Fernando (2003). Water alternating enriched gas injection to enhance oil production and recovery from San Francisco Field, Colombia. Master's thesis, Texas A&M University. Available electronically from
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