New HF Acid Fluid Technology Used for Future Fifth Restimulation of Deep GOA Well

Abstract Objectives/Scope Operators face many challenges as a well approaches the end of its life. Decisions must be made related to the economic feasibility of performing a restimulation treatment to increase and prolong production versus well plug and abandonment (P & A). This is the situation that a GOA operator was facing for a well in their Deepwater field that was plagued with issues including organic deposition, fines migration, aging proppant pack, and increasing water cut. Methods, Procedures, Process A damage mechanism assessment was performed which included a problem-solving exercise and lab evaluations of oil and water samples. Due to the prior four light well intervention vessel (LWIV) bullhead HF acid restimulation treatments preformed on this aging well, an HF fluid system was needed that had a low corrosion rate to protect the completion equipment as well as a higher pH stimulation fluid that would do as little damage as possible to the existing proppant pack. To achieve all of these goals, a newly developed HF acid fluid system was vetted. In addition to the standard stimulation fluid to reservoir fluid compatibility and HF acid corrosion testing, acid solubility tests were performed with analog core material that was identified for the target formation. These acid solubility tests were used to compare the different acid systems pumped during the well's lifetime to evaluate the impact on the formation/proppant pack with each acid stimulation treatment. Results, Observations, Conclusions This eleven-year-old well had undergone four bullhead restimulations where the acid treatment formulation was altered each time the well was treated due to changes in formation damage mechanisms. Some of the alterations included refining the solvent package, including the incorporation of a solvent soak to combat the organic deposition problem, chemical diverter package, and HF system variations. The primary benchmark for well treatment success was using an increase of well PI. This new HF acid fluid was also found to be less corrosive due to the higher pH of the system allowing less corrosion inhibitor to be used which aids in reducing formation damage and changing the wettability of the rock. Additionally, solubility analysis of an analog core sample was conducted, and the fluid was shown to have comparable dissolution ability to traditional HF acid systems. Novel/Additive Information The uniqueness of this project lies in the fact that this will be the fifth restimulation treatment pumped on this well. Many operators have intervention standards that suggest that no more than three mud acid treatments are recommended. This paper highlights that with this newly developed HF acid system additional treatments can be pumped safely without creating additional corrosion to the downhole completion equipment or causing further damage to the existing proppant pac. This high pH HF acid will allow the operator to continue to perform stimulation treatments on the well to increase its current production and prolong its life prior to future well plug and abandonment.