North Sea First: Vessel to Vessel Acid Stimulation on Subsea Wells

StimWell Services completed a series of acid fracturing treatments on three subsea wells in the central North Sea in the spring of 2014. This work was unique as it was the first time that a large high rate acid treatment was successfully placed by a stimulation vessel through a light well intervention vessel (LWIV) in the North Sea.

Previous treatments have been pumped from the LWIV themselves or with a stimulation vessel via a semi-submersible rig. Pumping a treatment with skid equipment significantly limits the treatment size and rate. Treatments pumped via a semi- submersible rig are also more time consuming and expensive.

This arrangement with the LWIV & stimulation vessel allowed for a higher rate acid treatment to be pumped with significant cost & time savings.

Numerous benefits from a Safety and Efficiency stand point resulted from the way the work was performed and has set a precedent for future work in the field.

  • Pre-installed equipment allowed the two Dynamically Positioned (DP2) vessels to safely approach and work in close proximity maintaining a safe working environment in variable weather conditions.
  • A novel automated floatation system allowed for emergency quick release disconnect (EQD) of the high pressure Coflexip hose used between the two DP2 vessels during the treatment if required. This allowed EQD of the hose in an unlikely emergency situation without risk of damage to the subsea architecture which was located in water 85M deep.

* The weight on the hose hanger in the event of an EQD only changes by .15 MT from normal operating conditions with the hose connected.

* A retrieval system was designed to be able to safely and efficiently retrieve a disconnected hose back onto the Island Patriot's hose reel.

  • Shared weather forecasting allowed for both vessels to have a high degree of assurance that a sufficient weather window was present to carry out each treatment with a sufficient safety factor.
  • Amended and pre-agreed marine operating guidelines ensured that both vessels were able to remain on location with sufficient position control backup during the operations.

Efficiency / Results
  • Higher capacities for treatment volumes and rates by utilizing a purpose built DNV certified stimulation vessel resulted in substantially increased post treatment production rates versus placement of reduced volume from equipment and materials on board the LWIV.
  • High pressure surface lines on board the LWIV were pre-installed and tested prior to the arrival of the stimulation vessel allowing minimal connection time for the two vessels required to execute each treatment.
  • Logistics flexibility and vessel capacity allowed for other stimulation treatments to be carried out between each LWIV treatment on other locations without the need for a port call by the stimulation vessel.

The project was a major success for all parties involved and by being able to safely and efficiently perform large high-rate acid stimulations between the vessels the operator was able to perform the proper stimulation treatments for the wells.

Overall cost for the project was 2/3 less compared to carrying out the work with a semi- submersible and production from the wells exceeded expected production.


General Enquiries:

StimWell Services
Beacon Innovation Centre
Beacon Park
Great Yarmouth
NR31 7RA

Vessel Address:

StimWell Services
c/o Copco A/S
Vestkraftkaj 4C

Contact Details:

Tel: +44 (0) 1493 448021