Rock-to-rock remediation operations with PWC® and HWO unit


Operator: Major European Operator
When: December, 2020
Scope: Flawlessly executing PWC® operations from a HWO Unit

Permanent rock-to-rock barriers installed without section milling


A review of historic well data identified the requirement for remedial barrier placement on several of the platform wells to be permanently abandoned.

Due to the small platform footprint and available deck space, a P&A specific hydraulic workover unit was chosen by the client as the optimal solution for performing the downhole operations. These units by design do not have the same specifications as a traditional drilling rig with less torque and fluid storage available, but they are a very capable conveyance method which made Perf-Wash-Cement the ideal partner technology for rock-to-rock remediation.

In addition, the well architecture with limited
cap-rock for barrier placement and rat hole for dropping the TCP guns introduced a secondary challenge. However, with a robust track record effectively delivering 400+ successful plugs,
HydraWell’s experience proved valuable when supporting this campaign. 


Due to the natural decline of the reservoirs, Cessation of Production(CoP) was recently called on these platform producers prior to progressing to the wells plug and abandonment (P&A) and decommissioning phases.

Uncertainty regarding the quality and extent of the existing annular barriers required the inclusion of an annular remediation option within the abandonment programmes.


The HydraWell solution was to perform each Perf-Wash-Cement (PWC®) operation in two trips, allowing us to retrieve the TCP guns prior to running the wash and cement assembly.

Due to the specific annular contents identified, the HydraHemera™ jet-wash tool was chosen as the preferred technology for these wells.  The system provides the added flexibility that was required whilst maximising the efficiency of the operation.

Utilising experience from wider operations and backed up by in-house CFD modelling expertise, the HydraWell operations team worked closely with the wash fluid and cement providers to design out the traditional spacer fluid used.

This helped to combat the limited storage space available on the platform and reduced the HSE risk without compromising on the quality of the barrier placement. It also allowed for the nozzle configuration to be optimised for the restricted flow rates available.



The job execution was ‘textbook’ with a subsequent log over the PWC® interval showing superior barrier placement and a significant improvement in the cement quality.

Due to the achieved success, the Operator will continue to work with HydraWell on approximately 15 wells across its Celtic Sea assets as part of a two-year P&A campaign to completely abandon its operations efficiently and sustainably.

Working alongside well engineering and reservoir management specialists as the lead contractor will allow HydraWell to continue supporting our client’s substantial P&A requirements in the completion of this major decommissioning project.

HydraWell is proud to have been key to the positive start of a long decommissioning campaign and to strengthen the collaborative relationships between all parties involved.

Our PWC® technology offers a step-change in performance and has the potential to slash the operational sequence by up to six days when compared to the conventional section milling alternative. 

Based on reduced operating times of a diesel-powered jack-up drilling unit, that’s 720MT CO2 emissions.

Furthermore, PWC® produces zero swarf handling issues and zero metal shavings sparking huge positive environmental benefits due to the elimination of transportation needs, pollution risk and landfill capacity.

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