Abstract
The Sawah field, a waterflood field, currently produces approximately 130,000 BFPD with an average 96% water-cut. The Fluid In Fluid Out (FIFO) stands at only 0.6, resulting in suboptimal waterflood performance. One cause of the low injection rate in Sawah field is injector plugging due to solid content and/or scale, and characteristics of the reservoir itself. Pressure Transient Analysis (PTA) further validates significant skin and permeability reduction.
To improve the injection rate, workover activities are conducted on the targeted well using a combination of the Acidizing and C-EBD (Cyclic Extended Breakdown) methods. This involves a chemical and mechanical effort, where the acid dissolves scale, and the C-EBD creates fractures. Compatibility tests are conducted between acid and water production, as well as acid and water injection. A 15% HCl simple acid is injected with a 3-feet penetration near the wellbore using coiled tubing. Following soaking, the treatment continues by injecting water into the reservoir in 6 cycles, with 350-700 bbls of water for each cycle.
During workover activities, improved injectivity was observed through Step Rate Tests (SRT). After acidizing, a rate of 2.5 bpm at 1,600 psi was achieved, followed by 3 bpm at 1,350 psi after the first 3 cycles of C-EBD. Further injectivity improvements occurred during subsequent C-EBD cycles, with the first 3 cycles reaching 2.4 bpm at 1,300 psi, and the next 3 cycles achieving 3.5 bpm at a similar pressure. Post Put on Injection (POI), the injection rate increased from 0-30 to 5,100-8,500 BWIPD, marking the well's highest injection rate in history. This notable success opens opportunity for Sawah Field, facilitating the reactivation of trade-off wells and increased capacity to handle additional fluids from size-up jobs or new wells. The collaborative efforts of the Subsurface, Research, and Workover Teams in the Sawah field were vital in achieving this remarkable result, contributing to longer injection well lifetimes, preventing overflow at surface facilities, and enhancing employee satisfaction.
A lesson learned emphasizes the need to verify flow meter readings before and during execution, facilitating the prompt identification of problems or areas for improvement. Additionally, conducting an extra Step Rate Test (SRT) before acidizing serves as an added baseline. This successful approach is currently being implemented in other injectors within the Sawah field facing similar plugging issues, showcasing its ongoing effectiveness in enhancing operational practices.
