DEEP GULF PROJECT OPENS NEW ROV ERA

Benton F. Baugh
Baugh Consulting Engineers Inc.
Houston

William S. Tillinghast
Conoco Inc.
Houston

Multipurpose interface profiles have been installed on 12 ball valves in 1,080 ft of seawater.

These profiles allow an ROV (remotely operated vehicle) to swim up to and operate valves with 5,000 ft-lb torque, and also to inject repair sealant. Repair sealant can be injected into the upstream seat, downstream seat, and the stem packing through standardized porting.

The ball valves are in a subsea pipeline system in the Gulf of Mexico that connects the Jolliet TLWP (tension leg wellhead platform) in 1,760 ft of water to more conventional platform facilities in 616 ft of water.

The unified connection skid housing most of the valves and attached profiles discussed is in 1,080 ft of water. It serves as a connection point in the flexible pipeline system where further production can be conveniently connected. Some of the valves are in straight pipeline sections which are not directly associated with a skid.

This project is of particular interest because it reflects a change in the nature of the ROV-related business from one of limited capability manipulators and proprietary profiles to one of multipurpose, public domain profiles.

The initiation of public domain profiles is considered to be a key step in the development of a volume of economic subsea applications for ROV-type service systems.

The project also led to three "firsts" in subsea intervention:

Use of public domain interface profile
Use of multipurpose (i.e., for torque and hydraulic signals) profile
Remote repair of a subsea valve (by sealant injection),

PROFILE SELECTED

The RU-style profile, developed by Radoil Tool Co., was selected for this project because it was the only profile in the public domain which was known to provide the capabilities of operation by torque and hydraulic interfacing. Being in the public domain was considered to be an important economic consideration because it would allow future service operations to be competitively bid.

Fig. 1 shows the prototype of the RU (ReUsable) profile.

It has a square stem at the center for torque input, docking funnels on each side of the square stem, an internal connector recess around the square stem, and a circle of eight hydraulic ports. The hydraulic ports can be singles, duals, or triples for up to 24 hydraulic signals within a 9.500 in. diameter (on the RU-1.125 size shown). The ports are identified by letters from "A" to "H," in a counter-clockwise fashion.

Fig. 2 shows the actual style RU profile used on the Jolliet project. It is an RU-2 size, providing a 2-in. square capable of 5,000 ft-lb torque. The white indicator plate around the 2-in. stem provides position indication and positive rotation stops. This allowed the identical profile to be originally specified on valves from 2 in. through 12 in. The identical 5,000 ft-lb torque is input to any of the valves without fear of overtorquing any of them. The profiles were ultimately fitted on only 8 in. through 12 in. valves.

WRENCH

The wrench shown in Fig. 2 has two torque alignment posts which stab into the docking funnels on the RU-2 profile. The wrench socket which engages the square is called a cloverleaf square:

It is simulated by pressing a square bar into the sand and rotating it 45. The pattern in the sand is a cloverleaf square. The cloverleaf square is tolerant to erosion off the stem, marine buildup on the stem, and allows 45 of free rotation between right and lefthand torque. These characteristics make it ideal for subsea service.

The small chain seen on the wrench transmits the wrench rotation to an indicator on the rear of the wrench to allow observation by tv cameras on the ROV. The pattern of holes on the face of the wrench provides locations for mounting of hydraulic stab subs which engage the hydraulic ports. On the Conoco Jolliet project, the "E" port was used as a triple port for the three sealant lines.

The 8-in. ball valve shown in Fig. 3 with an RU-2 profile mounted on the top side is one which was used for the Jolliet project. Immediately above the profile and to its left is the debris cover.

The ROV was able to open the debris cover before service operations and close it afterwards. It could also completely remove the cover when required. The large cage around the profile provided guidance for vertically lowering the tooling.

The subsea utility wrench of Fig. 4 is shown with special guides to allow it to guide automatically into the guide cage of Fig. 3 with 6 in. of offset guidance. A flexible compliant handle on the top allowed the ROV to lower the tool into the guide cage and take full advantage of the 6 in. offset guidance provided.

This is a simple wrench based on a double planetary drive which only operated the valve. This tool could not be of assistance in the injection of the repair sealants.

In the future, any competitive ROV service contractor can use the wrenches, like the one shown which were purchased by Conoco, or make their own to the public domain interface sizes.

TOOL

Fig. 5 shows the ROV swimming underwater with the prototype utility interface tool. This tool was built on the top of a subsea utility wrench as seen in Fig. 4. Sealant intensification capabilities were added to the tool.

The upstream and downstream seat seals received 10,000 psi sealant, and the steam packing received 2,500 psi sealant.

The ROV is able to operate the wrench motor and three sealant intensifiers with only two hydraulic lines between the ROV and the tool. Recessed T-handles on the control panel face were used to direct the hydraulics to the individual function.

This tool weighed approximately 600 lb in air (with buoyancy material), and was buoyed to weigh only 25 lb in water. This original weight during testing was so light that the prop wash, of the ROV could actually bow the tool around. Changes were made to allow the net weight of the tool in water to be between 40 and 100 lb to accommodate available ROV'S.

The ROV was outfitted with a 6-in. thick belly skid and RU-2 profile torque/alignment pins mounted on the front. A pair of docking funnels was installed on the tool on the back near the top. The belly skid can be engaged with docking ports on the back of the tool, as shown, to carry the tool.

ROTATING POST

As can be seen, a tool of this size extends a long way below the bottom of the ROV. This makes for difficult handling on the surface and going through the waves of the air/water interface. For this reason, the RU profile torque/alignment pins on the front of the belly skid were mounted on a rotating post which could swivel 360.

This means that the tool can be mounted upside down at the surface for convenient handling, and then rotated down once it is underwater.

Numerous successful tests were run with this tool mounted on the torque/alignment pins (hard docked) as described. Additional testing was done with the ROV manipulator holding the tool by the compliant handle on the top. This landing testing was combined with the ability to operate the ball valve and to inject sealant in the underwater environment. All this testing was successful and was a clear extension of the technology which had been demonstrated before. It was, however, not the most interesting aspect of the test program.

Fig. 6 shows the most dramatic test of the system. It had been determined that some of the profiles would be mounted on valves which may not be near vertical. It was suspected that some of the pipeline mounted valves might be as much as 45 out of orientation. The fixture shown placed the valve in a position in which the pipeline was sloped at 5, and the valve was leaned over at 45.

This situation meant that the compliant handle could not be used for landing. No flexibility could be provided for between the ROV and the tool. The tool was cocked over at 45 to the ROV using the rotation of the mounting-post to the belly skid.

The ROV was required to locate the profile and land the tool by settling down and to the right at the same time. The ROV was not an ultra fancy model with any special positioning controls. It was just a plain, smaller ROV.

The experienced pilots for the ROV were able to accomplish the tasks in a few minutes. The task was possible, but clearly beyond the capabilities of anyone but an expert pilot.

The test program and field installation have demonstrated a number of new developments:

Workability of multipurpose and public domain profiles
The ability of a small ROV (20 hp) to handle a large package (600 lb in air)
The ability of an ROV to install packages at odd angles when assisted by proper guidance frames
Subsea workability of subsea sealant injection systems.

Additional testing with the RU-1.125 profile size has demonstrated the ability of an ROV to approach a profile horizontally and make engagements. Divers have used neutrally buoyant RU-1.125 wrenches to engage the RU1.125 profiles for 1,000 ft-lb torque capability, with hydraulic stab subs in place. These tests have demonstrated that practical public domain interfaces are now commercially available for the specification, manufacture, installation, and use by anyone in the industry.

The clear definition of this interface will surely stimulate technical progress on both sides of the interface.

ACKNOWLEDGMENTS

The authors would like to acknowledge the outstanding commitment of Conoco Inc. and the joint interest owners in the Jolliet project, OXY USA Inc., a subsidiary of Occidental Petroleum Corp., and Four Star Oil & Gas Co., a subsidiary of Texaco Inc. Their support has made a substantial contribution in the development of new technology in the area of subsea intervention profiles and subsea intervention tasks.

EDITOR'S NOTE...

The work on which this article is based is also the subject of a 1990 Offshore Technology Conference paper (No. 6353) by Benton Baugh and W.S. Tillinghast titled "Systems for ROV actuation and repair of pipeline ball valves."

In addition, Tillinghast has covered the Jolliet pipeline in more detail in his 1990 OTC paper (No. 6403), "The deepwater pipeline system on the Jolliet project.