Bridging the P&A gap

New and expanding regulations governing the growing number of ageing offshore oilfields are pushing the industry to develop safe, innovative and fit-for-purpose technologies for well plug and abandonment (P&A) operations and late-stage interventions. Delaney Olstad discusses Weatherford's experience to date with a customized hydraulic pulling and jacking unit that incorporates a BOP and was put through its paces last year on a Gulf of Mexico mature well intervention.

As offshore oilfields worldwide increasingly shift from asset to liability, they must either be decommissioned or reinvigorated to enhance further production. Globally, an estimated 20,000 idle wells have been identified for abandonment, 60% of them in the Gulf of Mexico. Other major markets are the North Sea, Asia Pacific and sub-Saharan Africa. The US Gulf has an estimated 9000 wells that are idle, some of them for as long as five years. Many have sustained irreparable hurricane damage.

From a service company standpoint, the focus is on operational excellence in providing state-of-the-art products and services for completing this final and inevitable stage of the life of a well in ways that comply with increasingly stringent environmental regulations that vary from region to region.

Demand for P&A and late-stage intervention services has increased dramatically in the Gulf of Mexico following changes in well and platform abandonment regulations in the wake of the April 2010 Macondo incident. These regulations, governed by the Bureau of Safety & Environmental Enforcement (BSEE), include NTL 2010-NO5, which stipulates increased safety measures regarding the use of blowout preventers. NTL 2010-GO5 states that if a Gulf of Mexico well has not been productive for three or more years, the operating company must put forward a plan, including a timeframe and methodology, to abandon it. Regulations also outline detailed permanent plugging requirements for cement plugs and squeezes.

In response to these ever-changing regulations and client requirements, Weatherford has engineered a rigless alternative, a customized hydraulic pulling and jacking unit (P&JU) that incorporates a BOP for abandonment and mature-well intervention operations. Over the past six years, the unit has been deployed for 10 P&A and late-stage intervention programs in the Gulf of Mexico, including a late-stage intervention last year in the Green Canyon area.

A rigless alternative

The technology has emerged as a safe and cost-efficient alternative to conventional rig-based operations and workover or snubbing units, as well as crane-based operations in well P&A and intervention programs. Rigs deliver relatively fast trip time in pulling tubulars, offer large capacity fluid storage and diversified crew skills, including dedicated crane operators, electricians and mechanics. Jackup rigs are self-sustaining with personnel quarters. But with high day rates, large rigs can be expensive. In addition, jackups are not suitable for deepwater applications.

Snubbing units are often used because the equipment can be run while the well is under pressure. But because snubbing units are not designed for P&A or intervention operations, they can be considerably less efficient in terms of time and cost and are not as safe.

Crane-based operations provide flexibility in addressing various well and platform configurations, offer low day rates, are fast and highly responsive, require fewer personnel on board and leave a small footprint. But cranes also require increased trip time due to limited or lack of rack-back storage, have limited operating capabilities and are less flexible in changing weather conditions. Their inability to operate in high winds, for example, can result in the need to suspend operations, increasing mechanical downtime and non-productive time (NPT).

In many cases, the hydraulic P&JU can bridge the gap in overcoming the limitations of both rig-based and crane-based operations and providing an alternative for decommissioning wells or performing interventions to bring mature wells back online. The diesel-powered unit is less likely to be impacted by weather, a key advantage in reducing NPT. Once rigged up, the compact, lightweight unit is completely independent from the crane, and is American Petroleum Institute (API) certified to withstand winds up to 69mph (60 knots). Once assembled, the integrated jacking system and power swivel, which rests in its own integrated stand, require no additional rig-up time.

Each P&JU is API 4 F stamped, and incorporates innovative equipment, technologies and resources to address the challenges associated with these critical offshore operations. The unit is designed in modules, and is rigless, meaning it can be placed on offshore platforms that don't have existing derrick systems, have downgraded their derrick systems or have damaged derrick systems or structures. The hydraulically-powered mast sits directly above the well and allows a full range of operations to be conducted.

The P&JU is highly mobile and can skid from well to well with a selfclamping skidding system. The entire system has been designed to have a small footprint and provide greater flexibility to accommodate changes in well conditions. Most importantly, the design allows the BOP to be placed under the unit, making it fully compliant with regulatory requirements.

Weatherford's hydraulic pulling & jacking unit has been used in used in several Gulf of Mexico P&A and decommissioning operations.

BOP accommodation

Since the technology was introduced, it has been enhanced so that the undercarriage can cradle a larger BOP (triple stack with annular), by increasing the riser supports of the P&JU based on industry and client needs. The P&JU has a pulling capacity of 220,000lbs (99,790kg) in 60ft increments, a jacking capacity of 600,000lbs (272,155kg) and a racking capacity of 10,000ft (323 joints) of 31/2in IF drill pipe.It also offers 24-hour hurricane preparedness time.

A P&JU system was the basis of a multi-disciplinary, single-source solution for a Gulf of Mexico intervention and plug-and-abandonment operation in 10 wells on a platform in the Mississippi Canyon. The unit facilitated the support of 6200ft of 31/2in tubing, and achieved an average well-to-well skid time of one hour, beating the industry standard. The operation was completed in 234 days, 108 days ahead of schedule, and saved the operator an estimated $10.8 million.

In another Gulf application, the P&JU performed a successful plug-andabandonment operation on 11 wells on a hurricane-damaged platform leaning at a 15° angle.

The project was completed in 299 days, well ahead of the 365-day target, and saved the operator $6.6 million.

For a 2011 Green Canyon intervention project, a P&JU was deployed to recomplete a well within a new zone in a formation that had stopped producing. The well had a measured depth of 14,530ft with a maximum deviation of 41° at a water depth of 1353ft. Deviation at the perforations was 33°. The operation was the second late-stage intervention completed with the technology. The P&JU was selected because the deck space on the platform was limited and could not have accommodated a full-sized rig. It was also determined to be a better alternative than a snubbing unit, which the operator had used previously for this type of operation but found to be inefficient and unsafe by exposing personnel and equipment to risks.

For this project, the unit was used to replace more than 14,000ft of 27/8in, 6.5lb chrome tubing to clean out the well and recomplete it after setting a gravel packer. The P&JU can accommodate 10,000ft of drill pipe, but to handle the additional 4,000ft, it was a simple and safe operation to lay the additional tubulars down the integrated V-Door to reach the 14,000ft depth.

This operation increased production and extended the life of the well by providing access to new areas of the formation. The job was completed with no safety or environmental incidents in 50 days, or 1200 hours, between 14 August and 3 October. A key factor in the success of the project was that the P&JU was able to fit on the platform and provide all the necessary capabilities to safely and efficiently meet the operator's needs. The unit saved the operator considerable time and expense by providing a viable alternative to an expensive rig or an inefficient snubbing unit. The job also met the operator's requirements that all equipment and components necessary were provided with original equipment manufacturers documentation.

As offshore fields continue to mature and the heightened regulatory climate expands to other regions globally, the well abandonment and late-stage intervention market is expected to grow. These operations are increasingly being conducted in the highly-regulated North Sea region, where an estimated 2000 wells need to be addressed.

Delaney Olstad is product line champion for Weatherford International's Well Abandonment and Decommissioning Services. He has been with Weatherford for 14 years, serving as the US Region engineer for the Fishing & Re-Entry product lines and as the engineering supervisor over the Tubular Running Services R&D Group.

A surge in activity also is anticipated in Asia Pacific, historically a region where abandonment regulation has been severely lacking. However, with a number of Asia Pacific governments beginning to examine guidelines for dealing with the increasing number of mature wells, the late-stage intervention market in that region is expected to see an upturn.

Earlier this year, a P&JU was deployed for a significant late-stage intervention campaign on an 11-well project for a major operator in Brunei. The unit, built in a record 160 days, beat out several competing technologies, including snubbing units and workover rigs, in bidding for this project. OE