Innovative Planning and Remediation Techniques for Restoring the Well Integrity by Curing High Annulus-B Pressure and Zonal Communication
Authors: Ansari Arsalan A. , Libdi Ziad , Larsen Arne G. 
Published: November 2016

The petroleum industry has made significant investments and extensive research to rectify structural 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 9%" casing × 12¼" hole annulus; therefore, these wells are being abandoned. 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. Annulus-B Remediation using HydraWell Technology is one of the innovative approaches that can be utilized in wells to provide strong integral cement barriers behind the 9%" production casing 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, mitigate environmental concerns by avoiding excessive steel cuttings like section milling and eliminating the complexity associated to re-entry risk as incase of section milling.

The research utilizes a novel technology to execute a repair of wells with failed Annulus-B barrier integrity by providing integral cement barriers in the 9%" × 13%" casing annulus above the reservoir for wells experiencing migration of hydrocarbons from reservoir through the 9%"× 13%" 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 9%" casing above the reservoir.

Findings from the noise/temperature logs and oil sample evaluation indicated that oil is migrating from the reservoir, through 9%" × 13%" casing annulus, dripping at surface through the 30′ conductor pipe. The cement bond logs indicate poor cement behind 9%"  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 9%" 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 5–8 days 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 with reduced rig time and associated costs, resulting in minimum environmental risk.