Ravenspurn North is a mature gas field in the Southern North Sea with 42 wells, drilled and many hydraulically fractured in the late 1980s. By 2006 more than half of the wells had ceased to flow and many were flowing intermittently. With ailing wells and consequently falling production rates, the longer term future for Ravenspurn North field was uncertain.A wireline campaign suggested a common failure mode for many wells that large amounts of proppant had accumulated in the wellbore. Modeling of the potential range of static and dynamic pressure losses caused by this proppant supported a significant enhancement to the remaining gas potential. However, the depths of the wells combined with sub-hydrostatic pressure conditions and large diameter lower completions made achieving cleanout challenging. Furthermore, the target wells were located on unmanned offshore installations with minimal facilities, deck space and deck loading. This paper details how each of these obstacles were successfully tackled to reinstate a target set of wells. It describes the various cleanout options that were considered, and why Concentric Coiled Tubing Vacuum Technology (CCTVT) was ultimately selected. Prior to this project CCTVT had never been deployed in the North Sea and nowhere in the world at these reservoir depths. The operation was delivered on the small unmanned installation by conducting the world-first boat spooling operation of Concentric Coiled Tubing; rigorously re-assessing deck loadings; and running the operation 100% self sufficient with a maximum of 10 personnel on board.Finally this paper culminates with a detailed description of the successful CCTVT operations which recovered a total of 2,950 lbs of proppant from three wells to expose the perforations, and unload the wells of liquid. Furthermore, Concentric Coiled Tubing was used to mill out tubing profile nipples and install a packer to hang off 1,200 ft of flush joint tailpipe. Innovative thinking and close collaboration between operator and service companies was required as the ability to perform multiple operations on Concentric Coiled Tubing was in itself pioneering.Overall this campaign has pushed the boundaries of intervention technology to deliver an extremely challenging project. This has resulted in a more certain future for the Ravenspurn North field, as well as unlocking opportunities in deep depleted gas wells worldwide.

Ravenspurn North is a mature gas field in the southern North Sea with 42 wells, drilled (and many hydraulically fractured) in the late 1980s. By 2006, more than half of the wells had ceased to flow, and many were flowing intermittently. With ailing wells and consequently falling production rates, the longer-term future for Ravenspurn North field was uncertain.A wireline campaign suggested a common failure mode for many wells: Large amounts of proppant had accumulated in the wellbore. Modeling of the potential range of static and dynamic pressure losses caused by this proppant supported a significant enhancement to the remaining gas potential. However, the depths of the wells combined with subhydrostatic pressure conditions and large-diameter lower completions made achieving cleanout challenging. Furthermore, the target wells were located on unmanned offshore installations with minimal facilities, deck space, and deck loading.This paper details how each of these obstacles was successfully tackled to reinstate a target set of wells. It describes the various cleanout options that were considered, and why concentric-coiledtubing vacuum technology (CCTVT) was ultimately selected. Before this project, CCTVT had never been deployed in the North Sea, and nowhere in the world at these reservoir depths. The operation was delivered on the small unmanned installation by conducting the world's first boat-spooling operation of concentric coiled tubing (CCT); rigorously reassessing deck loadings; and running the operation completely self-sufficiently, with a maximum of 10 personnel onboard.Finally, this paper provides a detailed description of the successful CCTVT operations that recovered a total of 2,950 lbm of proppant from three wells to expose the perforations and unload the wells of liquid. Furthermore, CCT was used to mill out tubingprofile nipples and install a packer to hang off 1,200 ft of flushjoint tail pipe. Innovative thinking and close collaboration between operator and service companies were required, because the ability to perform multiple operations on CCT was in itself pioneering.Overall, this campaign has pushed the boundaries of intervention technology to deliver an extremely challenging project. This has resulted in a more-certain future for the Ravenspurn North field, as well as newly unlocked opportunities in deep depleted gas wells worldwide.

Ravenspurn North is a mature gas field forming part of BP's UKCS portfolio. The field commenced production in 1990 through 42 wells and 3 platforms but by 2006 half of the wells had ceased to flow. Surface pressures suggested limited remaining gas and, with declining production, the field was at risk of abandonment.A surveillance campaign carried out in 2006 suggested a common failure mode for many wells, which postulated that large amounts of proppant had accumulated in the wellbore. Pressures measured downhole above the proppant fill supported a significant increase of the remaining gas potential.A project to rejuvenate this field was initiated in 2007. The key to this project was cleaning out and reinstating non-flowing wells across the field. This would require pushing the boundaries of cleanout techniques and delivering a number of industry firsts, all on normally unmanned installations with complex logistical challenges. Additionally, each individual well intervention would be economically marginal on a standalone basis -the project had to place these interventions into a wider business context before building the case to justify the investment needed to resolve the many challenges presented. This paper details the journey to maximise the potential of the mature Ravenspurn North field. It starts with the acquisition of surveillance in 2006 and covers how the business case was built to justify one of BP's most complex well intervention programmes in the North Sea (concentric coiled tubing vacuum technology on a small unmanned platform). It culminates in the successful execution of the first phase of wells in 2010.With the first phase of the Ravenspurn North rejuvenation complete, this paper reflects on the lessons learned along the way and identifies the key activities which have contributed to delivering a longer, brighter future for this field.

Whilst there have been claims that the success rate has been near 30 per cent, the realistic success rate is near 3 per cent. Due to the poor success rate, the Chinese petroleum authorities are now likely to consider all proposals of offshore exploration.