The objective of this project was to install a capillary string attached to the production tubing and inject continuously corrosion inhibitor using electric chemical skid unit on the surface, controlling the doses according to the specific flow rate per well, and improve continuous rod life by extending MTTF.
To achieve the above mentioned objective, the well selection was focused on candidates with a declared corrosion-fatigue mode of failure, with bad actor wells of run life between one and three months. Once the candidates were identified, fluid samples were collected and sent to the lab to identify the corrosion source and categorize the corrosive level of the fluid, however this key information will define the chemical type and the specific daily doses. The chemical skid unit was designed and engineered to set the correct injection doses to maintain continuous treatment and avoiding waste. The use of chemical corrosion inhibitor programs has proven to be a cost-effective approach to minimize corrosion damage and to extend the life of downhole equipment. For this study, we have installed a capillary string attached to the production tubing string and Sucker Rod pump.
The capillary string has been successfully installed at pump seating depth (4,500 ft.). Chemical injection was commissioned at a rate of 5L/day, equivalent to approximately 60 PPM; the injection unit works as expected.
To have an efficient and effective product injected into the well, proper chemical selection considerations need to be taken.
After two months, a corrosion coupon installed in the flowline was removed to evaluate the effectiveness of the program. The analysis confirmed a reduction on the corrosion rate. The well selected has successfully achieved six months run life and still is running.
The continuous rod string was pulled out after six months and found in good condition.
This paper is intended to demonstrate the added value for fields where corrosion leads to regular downhole equipment failures, and providing a clear methodology of well selection and cost-effective solutions implementation, to reach an improved target of MTTF and ultimately of Operational Expenditures Reduction.