Foaming Issue during Chemical EOR Field Trial: Handil Field Experience

Abstract

Abstract Chemical Enhanced Oil Recovery (CEOR) has offered many opportunities to recover remaining oil during the gradual depletion of conventional oil reserves. One of the CEOR methods proposed is surfactant injection in huff-and-puff mode to reduce oil-water interfacial tension (IFT) and desorption of absorbed hydrocarbon from rock surface. As surfactant has a foam tendency, it becomes an operation challenge to maintain the quality of crude and produced water in the production stream. This paper aimed to describe the operation troubleshooting experience involved in lab analysis and field application during surfactant injection trial with the huff-and-puff method in Handil field, Indonesia. The soaking time was 72 hours, then produced to the existing surface facility. The main obstacle the was foaming issue in Oily Water Treatment Unit (OWTU). The consequence of this condition was the degradation of discharged water quality which leads to risk of environment pollution. Several proposed surfactant products and produced liquid sample were analyzed at lab for foaming tendency by volume ratio of 1:99 and 10:90. The product with less foam level was selected for further compatibility check with existing water clarifier and the proposed defoamer products. The combination of water clarifier and defoamer dosage that gave highest oil separation efficiency and fastest foam collapse time was selected for field application. After Surfactant Pumping and Soaking Program at well candidate with Huff-and-Puff method, the quality of produced liquid was frequently checked as basis of defoamer and water clarifier dosage adjustment. 5,000 barrels of surfactant solution that injected to one of oil well in Handil Field led to foam formation once the well was produced to surface facility. The foam at test barge separator could be fully collapsed by injecting defoamer product at the inlet. However, if the defoamer was stopped while the production was flowing to downstream section, the foaming issue could appear in oily water treatment unit and it degraded the quality of discharge water. Therefore, the recovered well effluent with total 2,000 barrels was routed to surface facility by batching method to accommodate the appropriate dosage adjustment of defoamer and water clarifier. The defoamer was adjusted around 50-100 ppm, while the water clarifier dosage was increased around 23% from baseline to improve the discharged water quality. As the result of this trial, the total volume of incremental gain from HD-X could be calculated for more than 12.2 kbbl based on well production record. In addition, the foam issue at OWTU could be managed and the water treatment could be resumed with close monitoring. The field trial enhanced the learning curve of surface treatment strategy during Chemical EOR operation in the mature field, especially for surfactant application. The result may be varied in different application, depends on the volume of recovered surfactant in the production stream and the targeted water quality as the compliance to environmental regulation.