This paper discusses the successful design, testing, and application of a new filter-cake breaker technology based on lactic acid chemistry. This technology provided prolonged delay in filter-cake breakthrough time at 220°F, which ensured coverage of the entire open hole, improved uniform filter-cake removal, minimized brine losses, and exceeded the expected production rates in different layers of the offshore Abu Dhabi reservoir.
Reservoir characterization was a fundamental component in the identification of the proper solution to maximize the return on investment of the assets. Temperature, permeability, porosity, and the nature of the reservoirs were studied thoroughly to determine one solution to be used in different reservoirs. Drilling fluid characterization (non-damaging with proper bridging package) and a proper filter-cake design were crucial to exceed the targeted production of the reservoirs. The paper discusses all steps from the laboratory testing of the breaker, application in different layers of the reservoir, and results obtained from the applications.
Lactic acid precursor was confirmed to be the "one fit solution" to cover the different reservoir layers. Because of its chemical structure, the hydrolysis process is slower than other breaker types currently available, which made it possible to maximize the breakthrough time at elevated temperatures, minimize completion fluid losses, and optimize the completion operations. Equally important, as an acid precursor rather than a live acid, this solution enabled the rig site personnel to implement the solution without affecting the health, safety, and environment (HSE) aspects that are fundamental in offshore locations. The possibility of pumping this solution through the rig pits enabled the jobs to be performed without additional equipment generally required for well stimulation. The achievement of these goals, supported by the higher production observed during the flow-back of the well, demonstrated how this solution maximized the return on investment for the assets located offshore Abu Dhabi.
The innovative use of lactic acid chemistry in the breaker, as compared to the conventional formic acid precursor breakers that are widely available, provided superior delay at higher bottomhole temperatures (in this case, 220°F) because of the slower acid liberation rate.