Finding an alternative

Jerry Lee

August 1, 2015

Already deployed off Brazil and West Africa, Jerry Lee investigates a new way to intervene on wells — from the drill pipe.

Animated picture of the ocean floor properties of Vallourec. Image from Vallourec.

Curbing the cost of already expensive offshore drilling and completions programs has to be the mindset of many oil and gas companies, especially after the oil price plummeted. Companies must look into ways to mitigate these costs. One possibility could be the deployment of drill pipe riser intervention systems (DPRIS).

DPRIS is a completions workover riser system that uses
an adapter near the surface and pipe similar to drill pipe for constructing a passage to the wellhead. The ruggedness and robustness of the connection allow for numerous makeup and breakouts, while the threading profile results in fast-joint con- nection and fast tripping speed.

To allow the passage of tools, the inner diameter (ID) of the pipe is optimized. However, the outer diameter (OD) is maintained, allowing the use of normal pipe handling equipment, make and break procedures, and crew. Also, these intervention systems are lighter than typical riser technologies, so they can be used by a larger range of platforms. The system’s characteristics make the system convenient to deploy and cost-efficient due to the speed of connections makeup and breakout, which eliminates the need for additional crew and equipment.

Moreover, in sour wells where sulfide stress cracking (SSC) could be an issue, the DPRIS can be delivered with resistance to SSC, as well as other forms of corrosion-assisted cracking. The resistance is incorporated as part of the structure of the steel itself. “We use special chemical compositions of the steel and special processing,” says Michael Jellison, senior vice president of engineering, Grant Prideco, part of National Oilwell Varco (NOV) Wellbore Technologies.

DPR-2500m 5K System Stack-up at P-XXII rig (Brazil). Photo from FMC Technologies.

Simply put, the drill pipe intervention system is a tube that is upset on the ends (a forging technique that thickens the wall at the tool joint) with highly specialized male and female connec- tions. The major difference between normal drill pipe and drill pipe intervention system is the incorporation of a high-pres- sure, gas-tight seal. “In general, DPRIS gives you access to the well. It allows you to connect to the well and perform various types of completions or intervention riser functions. It’s really a means to get access to the well or to install critical components on top of the well,” Jellison says.

Within one system, users have simultaneous access to a completions and intervention system. DPRIS is applicable for use with Xmas trees with fragile studs, Xmas tree and tubing hanger installation, retrieval, testing, hydrate disassociation, downhole valves maintenance, well test, sand removal, and more, says Luiz Fonseca, service manager for subsea services at FMC Technologies.

“Furthermore, the systems are able to operate as early production risers (EPR), providing a system that can perform long-term well testing. In the past, this system represented the sole production system of one basin, working at a floating, drilling, production, storage and offloading (FDPSO) vessel,” Fonseca says.

With more than 50 systems operating around the world, DPRIS popularity is gaining momentum.

The first system was developed in the mid-1990s to fulfill
 a request by Petrobras for a rugged system that could hand numerous makeups and breakouts. The result was the adaptation of drill pipes for gas-tightness.

VAM DPR SR Connection – properties of Vallourec.Photo from Vallourec.

This first generation drill pipe riser, VAM DPR SR, included
 a Teflon ring on the shoulder that provided gas-tightness up to 5000psi working pressure. First used offshore Brazil, the system was later brought to offshore Angola, West Africa, in 1999, where Total deployed the system at the Girassol project, via FMC Kongsberg. At Girassol, 33 wells were drilled and DPRIS was deployed 66 times for Xmas tree and tubing hanger installation. During its 14 years of deployment in Angola, the system has been run more than 180 times. The systems are inspected every 3000 hours of use time. And, for the first 12 years of deployment, only 25 connections needed repair, says Vincent Flores, Vallourec global product line manager.

However, despite the success of the first generation DPRIS, it has its limitations, and with industry moving to deeper fields, the system needed to adapt to the changing environment. Thus, 2006 saw the launch of the second generation DPRIS, VAM DPR HP, which could be used at greater depths than the first generation. VAM DPR HP is rated for 10,000psi working pressure. However, the Teflon ring was replaced with a metal-to-metal radial seal design. In 2010, this second generation system was first deployed off Nigeria, West Africa, at another Total-operated project, USAN, mainly for Xmas tree and tubing hanger installation, as well as some well testing and well clean ups. “From 2010 to 2015, there were a total of 75 connections, which needed some repair, after hundreds of runs performed by the system. Each DPRIS can actually be rethreaded several times, thanks to its extended tong lengths. Hence,
it allows an enhanced lifespan compared to conventional riser systems,” Flores says. The system is still currently in use at USAN and has been deployed in Brazil as well.

However, every technology has limitations and room for improvement. DPRIS is limited by CO2 in high-pressure, high-temperature (HPHT) conditions, moonpool dimensions, power supply current and nearby deck space required to lay down the hose reel that must be lined up with the moonpool and derrick

A-frame. Operators are also concerned about spare parts supply support, the acquisition of missing parts of the spare systems
 to provide a complete spare system, tool ratings for HPHT scenarios, and the contract model that should be addressed, FMC’s Fonseca says. Despites this, interest in the system seems to be on the rise.

Much like the need for the development of the second generation DPRIS, as the industry heads to ultra-deepwater, such as in the Gulf of Mexico (GOM), suppliers must be prepared for the demand of 15,000-20,000psi-rated DPRIS.

6 5/8” Grant Prideco Drill Pipe Intervention Riser with XT-M Connections. Photo from NOV.

“The GOM looks like it’s about to turn the corner and start adopting the technology in a more widespread basis. [It] will probably be the most active areas for the technology,” Jellison says. “It’s starting to pick up fairly significantly. There’s lots of interest in it. We’ve had interest from several of the major operators of deepwater within the last year.”

The challenge for DPRIS technology is the high pressure involved for applications in the GOM, and also in the types of tools commonly used. The larger tool types, such as plugs, are common in the GOM but will not fit in current DPRIS configurations. So that’s where the next generation is heading — toward larger pipe and tool joint ID’s.

“In the past, NOV has been limited to an OD of 6 5/8in, which limits the size of the tools that can be run inside the pipe, but there’s a strong need and desire for larger sizes. As a result, we’ve been working on an intervention system with a larger OD,” Jellison says. Also, due to torsional limits during makeup, there will be a new optimized design for the connection.

Vallourec is addressing the need to widen the ID by using a proprietary grade of steel and changing the connection design. “We have our high-strength materials that are called VM 150 and VM 165. They have 150,000psi and 165,000psi, respectively, as the minimum yield strength. The interest of those grades is that you can increase the performance, via tension and pressure ratings, without having to increase the weight of the wall thickness,” Flores says. For the new connection, the design will use new threads and geometry. As a result, the OD of the new product will remain closer to the previous generations, while the ID is enlarged.

Successful deployments in Brazil and West Africa have led to significant improvements and growing confidence in DPRIS technology. With a new market burgeoning in the GOM, DPRIS manufactures could see global interest in this technology rise.