The petroleum industry has made significant investments and extensive research to rectify well integrity issues, one particular failure mode relates to the structural degradation of the surface and conductor casing strings by the effects of corrosion. Historically, and by convention, the inability to provide integral barriers in the 9⅝″ × 13⅜″ casing annulus is resulting in wells being abandoned. Section milling to restore annulus integrity and the use of external casing patches to replace failed casings are two of the innovative approaches that we utilized in offshore wells to recover annulus integrity and as such preventing reservoir fluid migration to surface. These approaches have proved successful as they provided real economic and environmental advantages. We have proven that wells can be put back on stream with greatly reduced CAPEX and OPEX exposure, negating the need to drill new replacement wells; we achieved tangible commercial benefits and at the same time reduce our environmental risk exposure. Our remediation engineering design focuses on the application of a novel strategy for an offshore well that had failed Annulus-B (9⅝″ × 13⅜″ casing annulus). The failure was detected during planned annulus monitoring. The annulus pressure test failed and testing fluid was observed exiting from the conductor. The remediation action involved section milling and the placement of cement to regain annulus integrity. The operation commenced with standard workover practices for the completion recovery, followed by the running of cement, noise, temperature and corrosion logs in an effort to evaluate the cement quality behind 9⅝″ casing above the reservoir and gain corrosion mapping of the 13⅜″ casing. The noise/temperature logs indicated a leak point at 4500 feet and the annulus space was hydro-tested which resulted in returns being observed at surface, confirming a direct leak path from the 9⅝″ × 13⅜″ casing annulus to the 13⅜″ × 30″ casing annulus. The cement bond logs indicated poor cement behind 9⅝″ casing above the reservoir. However, the results from metal thickness detection logs indicated insignificant corrosion (˜15%) for 13⅜″ casing, eliminating the need to recover and replace this casing string. The decision was taken to place two cement barriers behind the 9⅝″ casing, above and below leak point, and an additional barrier would be installed with the use of a 7″ tie-back casing string. The planned strategy was successfully implemented and the integrity of the producer well was restored with two competent 100’ cement barriers behind 9⅝″ casing, above and below the leak depth, and a 7″ tie-back casing string was also cemented all the way to surface. As a result of this remediation, the production rate for the well was restored and provided an additional 200 BOPD as compared to expected production rate. Adopting the above methodology resulted in approximately 50 days rig time giving significant cost savings and negated the requirement to permanently abandon this well and to drill a replacement well.

Increasing global demand for additional energy requirement - forecasted to increase up to 74% by 2030 - has catalyzed the petroleum industry to perform extensive research into rectifying structural well integrity issues in order to extend the life and return older wells to production and injection. These issues are mainly caused by failure of corroded surface casing. Due to the inability to provide integral barriers in the 95/8″ casing x 12¼″ hole annulus, these wells are planned to be abandoned or completed as single zone wells. Perforate, Wash and Cement remediation strategy is one of the innovative approaches that can be utilized in wells to provide strong integral cement barriers behind the 95/8″ casing to prevent reservoir fluids migrating to surface. This approach is gaining increased popularity due to a number of economic and environmental advantages such as reduction in costs for abandonment of current wells and drilling of new wells, mitigate environmental concerns, restoring the well production/injection with minimum workover costs and eliminating the risk with section milling of not being able to re-enter the casing. The research utilizes a Novel Remediation technique for providing integral cement barriers in the 95/8″ x 133/8″ casing annulus above the reservoir for wells experiencing migration of hydrocarbons from reservoir through the 95/8″ x 133/8″ casing annulus. The planned methodology starts with completion recovery followed by running cement, noise, temperature and corrosion logs in order to evaluate the cement quality behind 95/8″ casing above the reservoir and the corrosion level for 133/8″ casing. Findings from the noise/temperature logs and oil sample evaluation indicate that oil is migrating from the reservoir, through 95/8″ x 133/8″ casing annulus, dripping at surface through the 30″ conductor pipe. The cement bond logs indicate poor cement behind 95/8″ casing above the reservoir. However, the results from Metal thickness detection logs indicate low corrosion (~10-15%) in the 133/8″ casing, eliminating the necessity for any external casing patch to restore 133/8″ structural integrity. Therefore, Perforate, Wash and Cement remediation strategy was successfully applied and the integrity of the dual water injector well was restored by placing 100-feet cement barrier behind perforations in the 95/8″ casing above the reservoir. In addition a 7″ short tie-back was installed over the perforated cemented interval. Hence, the 95/8″ casing was re-established as a well barrier element in the well, allowing the injection rate for the well to be restored. This strategy may be developed as an economic saving technology as it saves us approximately 5-8 days per well with associated significant CAPEX and OPEX savings by avoiding additional costs on section milling and solving problems encountered with section milling. It is feasible to be applied in offshore wells having integrity issues as it extends the life of the well without taking on additional environmental risk.

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