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Development of Conformance Gel for Diadema Oil Field using Powder and Emulsion Polymers and their Impact on Equipment and Economics
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2019 – 20th European Symposium on Improved Oil Recovery, Apr 2019, Volume 2019, p.1 - 11
Abstract
Summary
Diadema Oil Field is located in the San Jorge Gulf Basin in Southern Argentina. The field is operated by CAPSA, an Argentinean oil producer company; it has around 500 producer and 300 injector wells (well spacing is around 250 m). The company has been developing water flooding during more than 25 years (today this technique represents +65% of oil production), polymer flooding during more than 10 years and (+15% of oil production); produces about 1,850 m3/d of oil and 45,000 m3/d of gross production (96% water cut) with 43,000 m3/d of water injection.
The main reservoir under secondary recovery is characterized by high permeability (500 md average), high heterogeneity (10 to 5000 md), high porosity (30%), very stratified sand-stone layers (4 to 12 m of net thickness) with poor lateral continuity (fluvial origin) and 20 °API oil (100 cp at reservoir conditions, 50 °C). Due to such reservoir conditions, injectors and producers are subject to channeling problems.
Polymer gels have been extensively used to tackle such conformance issues. The criteria of success do not only depend on the quality of the technical solution but also on economics. Generally, gels are formulated using polymers under powder form requiring the mobilization of a dissolution unit, a maturation tank and one to several dilution tanks. On the opposite the utilization of polymers under reverse emulsion form only requires the use of a single skid including a static mixer for the inversion of the emulsion and one or two static mixers for polymer dilution and homogenization with the crosslinker, reducing both the footprint of the equipment (important for offshore) and the cost of the treatment.
Two gel formulations using Chromium (III) acetate as crosslinker and partially hydrolyzed polyacrylamide either under its powder or its reverse emulsion version were developed to fit field conditions targeting a gel D category according to Sydansk classification and a gel time below 36 hours. A cost analysis comparison of both formulations was performed to select the more efficient solutions.
Gels C to D were achieved for both formulations, 15 hours gel time and good stability over 3 months. The economical evaluation showed that the cost saving associated to the use of a single skid did not compensate the extra price of the reverse emulsion compared to the powder. The formulation using HPAM as a powder was selected and 20+ injection wells were treated without facing any operational issue.
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