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Intervention invention

A new modular subsea well access system makes it possible to carry out work ranging from subsea tree installations to permanent plugging and abandonment operations without the expense of a rig.

Using off-the-shelf and field-proven components, the well access specialists at Optime Subsea Services have created a system the company believes can save operators money and time.

Thor Lovland, chief operating officer of the of Norway-based company, says front-end engineering and design studies indicate an ability to complete a permanent plug and abandonment operation without the use of a rig at a 60% cost savings using Optime’s multiCompletionSystem (mCS) compared to current rig and light well intervention solutions.

The same system using a different configuration tailored to subsea tree installation can save an estimated $1 million to $2 million per vertical subsea tree installation, he says.

“We believe the market now wants a system that is simple, with field proven components, but innovative in its way to significantly drive down costs, time, and can be run from a lighter service vessel,” Lovland says.

At Optime, founded in 2015, “standardise is a buzzword”, he says. “We saw it. We lived it on a daily basis. We need to change — not just processes but the technology.”

The company drew inspiration for what would become the mCS from other rigless systems, which Lovland calls “excellent technology but too complex”.

The mCS, in all of its different configurations, takes control over the well and maintains its safety barriers and control during any of these operations, the company says.

“The mCS is a system that has the modularity and the life-of-field concept. Modular building blocks do christmas tree communications, (intervention workover control systems)-type services through installation, stimulation, interventions and all the way to plugging and abandonment,” he says. “We wanted modularity without the complexity that a lot of times comes with that.”

Building blocks

A lower control package (LCP) holds all the controls equipment, such as subsea pumps, which eliminates the need for large topsides equipment. The basic mCS unit functions as a christmas tree controller when using the LCP.

When a field-proven hose is added to the LCP, the mCS can carry out light well intervention operations such as well stimulation and hydrate remediation to increase oil recovery.

By combining the LCP module and the newly-designed barrier removal tool (BRT), the mCS can install christmas trees and put the well on stream while maintaining double barriers subsea.

Adding a well control package and field-proven tools used in other well access, intervention, downhole and drilling operations to the LCP makes it possible for the mCS to carry out rig-less and riser-less plugging and abandonment operations.

“This is in fact what makes the system so innovative and unique. It is the use of existing solutions, but applying it into a different system and configuration,” Lovland says.

Combining a field-proven lubricator and pressure control head with the LCP turns the plugging and abandonment stack into a traditional riserless light-weight intervention system.

Lovland says each of these modules costs much less than their traditional counterparts because a smaller vessel can be safely used, minimising the type and amount of work a rig is required for at the well site.

“This isn’t new technology. You’re using it already. It’s field proven. The valve, connectors, control equipment, the hose, etc, we’ve piecemealled it together. The system is what is new.”

Under development

Optime did not start with the rigless, riserless plugging and abandonment system. Instead, it focused on developing a system that could carry out subsea installation of trees from a support vessel, which it designed, built, tested and prototyped in 2015.

But with the industry in a down cycle, there were not many greenfields projected to go online. The forecast for installation needs was grim, so Optime turned its engineering talents to creating modules that could carry out brownfield work - well stimulation, intervention and plugging and abandonment operations.

Through it all, the emphasis was on using off-the-shelf technology and components to avoid the need for qualification testing and focus on modularity so the same basic system could be used simply by changing out a few key parts of the kit.

Once the company had a dedicated well completion package, the next step called for combining intervention and drilling technologies. Adding the light well intervention well lubricator, wireline operation and pressure control head resulted in an intervention stack.

“The capital investment is about a quarter of a traditional light well intervention system,” Lovland says.

He sees the system’s modularity as providing flexibility for operators.

“If you get a 20 or 30-well campaign, some of them you may not need to perform a plugging and abandonment on. Some you may be able to stimulate. You’d have that ability by planning ahead,” Lovland says.

New territory

Optime recently opened an office in Houston. The company says the Gulf of Mexico – with wells typically yielding lower recovery rates than the more-often stimulated North Sea wells – is a prime market for inexpensive well stimulation services.

The Gulf of Mexico also has a number of wells that need to be plugged and abandoned, and operators typically want to minimise costs associated with closing down wells.

“By combining two field-proven operational technologies, we have developed an industry unique and first of its kind, completely rigless, riserless plugging and abandonment system,” he says. “Today, as far as we know, no other systems can do complete permanent plugging and abandonment from a vessel. None.”

The appeal for such a system, he says, lies in the fact that many plugging and abandonment operations are done from costly rigs or light well intervention vessels, and the operator is paying for functionality that is not required.

By using a modular fit-for-purpose system like the mCS, costs for operators will go down, although an intervention vessel is still required because of the need to handle hydrocarbons on the deck.

The drawback until now in reaching a rigless, riserless plugging and abandonment system has been how to ensure the resulting system still had enough power to kill a well, if need be.

“We’ve moved the barriers subsea. On a rig, barriers are topsides,” Lovland says. “By moving the barrier subsea, we actually created a safer operation, with no risk of hydrocarbons on deck during well barrier removal and also less personnel involvement during operations in the red zone.”

The solution itself is not complicated and is based on “piecemealling” existing solutions into a new combined system.

While the plugging and abandonment system does have certain limitations, Lovland says, the module can serve an estimated 75% to 80% of the wells that need to be abandoned right now.

“We don’t want to, or need to, build a system that does it all. The market needs the most cost-optimised solution and one that can handle the most challenging operations.”

Some concerns have been voiced about open-water coiled tubing and well barriers when it comes to a rigless, riserless plugging and abandonment module. Lovland says Optime designed an open-water coil tubing system dedicated for plugging and abandonment operations that increases the robustness and “watch circles” vessels use to define safe operation limits.

“It is important to remember that setting a plug, cement or other alternatives like polymer... is just a very small piece of the operation,” Lovland says. “But a lot of today’s focus on plugging and abandonment appears to be only focusing on these smaller pieces of the operation.”

Instead, he says, the well needs to be secured in an under-pressure state, while ensuring sufficient drift (scale and milling), circulating in the main bore and annuli, testing for overburden zones, generating space for primary and secondary permanent plugs, setting plugs, verifying and testing plugs and finally removing the wellhead and setting the plug.

He says the Optime system was designed for all of these steps but uses one system to provide a validated 40% to 60% cost reduction when compared to rig plugging and abandonment operations.

Another draw for the system is that the mCS puts less strain – only about 40 tons – on aging wellheads, compared to a typical 200-ton blowout preventor, Lovland says.

“When there are wellheads with little documented data, and no more fatigue life, and you’re coming in with a BOP of 200 tons, there’s nothing left,” he says. “We have about seven and a half thousand times more fatigue life on our system compared to a BOP system. That’s big if wells are 20 or 30 years old.”

Decreased footprint

The big goal for the mCS, aside from lowering capital expenditure, is to reduce the footprint.

“The umbilical and the way we’ve communicated from topsides to the subsea, that’s changing,” he says. “The traditional umiblical’s got to go.”

One piece of that is a field-proven subsea hydraulic pump unit from Telemark Technologies, which merged with Optime in October 2016 with the objective of fast-tracking Optime’s cost-saving subsea installation solution to the global oil and gas market.

The purpose-built subsea pump generates hydraulic control pressure to operate the subsea valves and actuators subsea. The umbilical cannot be removed but the hydraulic lines will be replaced with electric conductors, making it a very small outer diameter. The pump does not handle any communications subsea.

The mCS can be used on many vessels of opportunity. For christmas tree installation and well stimulation, vessels between 70 and 100 metres long with crane capacity of 50 tons or more are sufficient. For plugging and abandonment work, an intervention vessel is required, although a “rig of opportunity” is also acceptable while rates are down

“Using mCS on a rig will still solve the challenge with wellhead fatigue, increase operational speed and be considerably quicker, and more cost efficient than what is done today.

"Mobilisation of mCS on a rig will be straightforward due our system’s limited footprint, low height, and by utilising existing rig equipment such as hydrocarbon and mud management,” Lovland says. “We’re agnostic as to what our equipment can work with — standard flanges, standard interfaces, flying leads when we need to.”

Following the recent merger with Telemark Technologies, Optime has the capital needed to build its mCS modules on spec. The subsea services company expects the first – the well stimulation package – will be ready in mid-2017.

Lovland says the company is also working to refine the modular building blocks of the mCS system and make it more cost-effective.

The company realises that “opportunities for these fit-for-purpose operations are what is currently in demand in the market, both short and longer term, so the priority is to deploy these systems and services globally before we move on to developing our other downhole tools or riserless components and systems”, he says.

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