Recent research from Bloomberg suggests the global offshore decommissioning market will reach $9.5 billion by 2027, led by mature regions such as the Gulf of Mexico and the North Sea. According to industry body Oil & Gas UK, 1,832 wells on the U.K. Continental Shelf (UKCS) and the Norwegian Continental Shelf are mature and expected to be decommissioned through 2025. A potential inhibitor to future decommissioning activity is the high cost currently associated with the process. However, those costs are coming down.

The Oil and Gas Authority, the U.K. industry’s regulator, recently reported a drop in estimated decommissioning costs for the UKCS, largely due to improvements in planning and execution of processes such as plug and abandonment (P&A).

The underlying drivers for global decommissioning and P&A activity include regulatory or legislation trends toward the implementation of comprehensive legal regulation for the decommissioning and safe abandonment of oil and gas wells as well as an increased focus on operational safety offshore. In terms of the P&A market, a low oil price and increased rig availability can shift the emphasis from enhancing late-life production for maturing fields and infrastructure to accelerating economic cut-off dates. Operationally, there is an increased focus on innovative systems to enhance safety while reducing time, cost and operational complexity related to P&A.

Technology evolution
With cost reduction a key challenge in the modern industry, the focus on safely managing abandonment has never been greater. A response to this has been the development of a range of new technologies and a review of conventional practices and processes to enable P&A at an appropriate cost.

Oilfield services company Expro offers a recently developed technology that has a safe, cost-efficient low footprint and is an agile alternative to conventional coiled tubing (CT). The company recently acquired Quality Intervention (QI), which added new CT technology, annular integrity technology and in-situ wellhead remediation tooling to its product and services range. This has enabled Expro to build on its existing P&A offering and expand into a CT and pumping service market estimated to be valued by the company at approximately $6.3 billion.

Lightweight, heavy-duty system
Conventional CT delivers high-rate circulation, but it can be heavy, bulky and time-consuming to plan and mobilize. The process can involve potential HSE exposure, significant rigup and lifting (about two to three days), considerable costs (more than $1 million), personnel, and a relatively heavy and large footprint. Furthermore, CT can only be deployed on large rigs or platforms, or spooled from a vessel.

The CoilHose Light Well Circulation System (LWCS) from Expro substitutes hose for the conventional steel pipe currently in widespread use. The system enables rigless light circulation services from a package with a relatively small footprint and offers operators an alternative to CT that can be rapidly deployed across all types of installations onshore and offshore, reducing overall HSE exposure while maximizing operational uptime.

The CoilHose Light Well Circulation System is shown being rigged up. (Source: Expro)

Rigup time for the new system is no more than 4 hours, and the number of personnel required ranges from four to six (compared to up to 11 or even more for CT). Lifting requirements are limited. It can be deployed almost universally across all types of installations and into the most challenging of wellbores at temperatures ranging up to 150 C and to depths in excess of 10,000 ft.

The LWCS does not utilize an injector (like CT). Instead, it is weighted down by the bottomhole assembly (BHA) connected on the downhole end of the hose and run in hole by gravity feed, in a similar way to wireline. The CoilHose unit is used to deploy and retrieve the CoilHose and BHA from the wellbore.

The tubing itself is a flexible and reinforced high-pressure hose. It incorporates several layers of high-tensile steel wires and an outer layer made of thermoplastic materials. With a safety factor of four, the specially designed hose has a working pressure of 12,500 psi.

The pressure control package used to deploy CoilHose into the wellbore consists of a customized pressure control head and triple or quad ram BOP. The ram configuration is set to be the same as for a CT operation, with a shear/seal on top and pipe rams in the middle and at the bottom. The pipe ram is designed to seal without damaging the hose.

All BHA components such as the end connector, dual flapper valves, straight-pull release, swivel, weight bars, turbine and variations of cleaning nozzles have been designed and manufactured to complement the system. Applications include downhole safety valve and wellhead cleanout, nitrogen gas lift or unloading wells, memory logging services, halite and hydrate removal, tubing cleanout and fluid displacement.

This technology provides the further efficiency of being able to deploy wireline from the same unit, thus avoiding lengthy and costly idle rigup and rigdown periods between the different types of intervention.

In addition to the intervention of the main wellbore, Expro has the ability to enter and intervene in the annuli. With casing integrity issues, such as pressure in the annulus (a growing concern due to the industry’s stock of aging wells), Expro’s annulus intervention technologies are helping to address well integrity challenges. Applications include downhole circulation in the well annulus, remediation of sustained casing pressure and cementing, annulus fluid replacement, sealant for downhole leak repair, corrosive fluid displacement, diagnostics and logging, and environmental and groundwater protection.

The WellSpring annulus intervention system offers minimally intrusive equipment allowing the wellhead remediation of annular integrity issues without the use of a heavy workover rig, resulting in significantly reduced cost (up to 95%). This system, which can be rapidly mobilized, helps operators prolong the life of wells and increase recovery through the revitalizations of shut-in and low production wells.

Multiple runs
The CoilHose LWCS system has been deployed on multiple occasions with more than 100 runs in live wells. It was used recently to successfully remediate a failed downhole safety valve in a well in the North Sea where scale buildup was suspected of having impeded full travel of the flow tube resulting in the failed test for the valve at 1,740 ft. Following a thorough assessment and planning process, including high-pressure pumps and a filter/suction package, a 2,500-ft-long hose was run in the well and a nozzle was used to jet a solution, including 15% hydrogen chloride at 3 ft per minute across the valve. Subsequent tests on the downhole safety valve provided positive results for the operation undertaken, with full flow tube travel restored.