Innovative Remediation Techniques for Restoring Well Integrity by Curing High Annulus-B Pressure and Zonal Communication
Authors: Ansari Arsalan , Al-Azizi Badr , Larsen Arne G. 
Published: March 2017

Abstract
The petroleum industry has made significant investments and extensive research to rectify well integrity issues, one particular failure mode relates to the migration of hydrocarbon fluids to surface through microchannels, due to poor cementation, resulting in the inability to provide integral barriers in the 95/8" casing x 12¼" hole annulus. Section milling and external casing patches are two of the widely-utilized approaches to restore annulus integrity; however, they add complexity associated with excessive steel cuttings and re-entry risk. Remediation using Hydra System is one of the innovative approaches that can be utilized in wells to provide strong integral cement barriers behind the 95/8" production casing below the 133/8" casing-shoe to prevent reservoir fluids migrating to surface. As a consequence, the well life can be extended and the older wells can be restored back to production and injection. This approach is gaining increased popularity due to a number of economic and environmental advantages such as restoring the well production/injection with minimum workover costs and risk due to less complex operations.
The research utilizes a novel technology to execute a repair of wells with failed Annulus-B (95/8" x 133/8" casing annulus barrier) integrity by providing integral cement barriers in Annulus-B above the reservoir for wells experiencing migration of hydrocarbons from reservoir through the this casing annulus. The planned methodology starts with completion recovery followed by running noise, temperature and cement bond logs in order to evaluate the cement quality behind 95/8" casing above the reservoir.
Findings from the noise/temperature logs and oil sample evaluation indicated that oil is migrating from the reservoir, through Annulus-B, dripping at surface through the 30" conductor pipe. The cement bond logs indicate poor cement behind 95/8" casing above the reservoir. Therefore, the aforementioned remediation technology was successfully utilized as it delivers effective jet washing and subsequent cleaning of the annular space using specialized tools and thereafter spraying cement to create a 100-feet competent cement barrier behind the casings for effective isolation and the prevention of pressure communication to the surface via Annulus-B. Furthermore, 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 well's injection rate to be restored.
This strategy may be developed as a very cost-effective technology as it saves the operator approximately 16-22 days and $ 1.6-2.3 million per well with associated significant CAPEX and OPEX savings by avoiding additional costs associated with complexity of operations in section milling. It is feasible to be applied in offshore wells requiring remediation of failed Annulus-B integrity as it delivers greater efficiency by reducing the rig time and the associated costs.