BJ Tubular Services leaped at the opportunity to provide pile-driving services for Murphy Sarawak Oil Company of Malaysia and its partner Petronas Carigali at their jackup-deployed platform installation off the west coast of Borneo.

The project wasn't going to be easy. The four structure support piles, measuring 36 in. x 1.25 in., would also be used as conductors for the Production A platform in the West Patricia field. Each of the four structure piles - or conductors - were to contain three 133/8-in. casing strings utilizing Hydril 521 connections with a maximum potential coupling outside diameter of 13.814 in., depending on pipe weight. This configuration would serve as the basis of a 12-well platform. The four piles were made up using internally-externally flush Oil States Puma connections.

Murphy Oil Engineering determined that the required depth - or penetration - of the 36-in. piles should be from 236 ft to 246 ft (72 m to 75 m) below mudline. Using soil data provided and drive simulations, BJ proposed using a reduced inside diameter (ID) drive shoe called the Composite Drillable Drive Shoe system (CDDS). The system would mitigate internal pile skin friction while driving, and allow installation to be achieved with currently available equipment within the Asia Pacific area. By using the CDDS, it would reduce the potential for costly and time-consuming practice of drilling out the casing during driving in order to make it possible for the pile to reach the required penetration. Another benefit of avoiding drilling out the inside of the casing was it eliminated any risk that drilling out would compromise the relationship between the surrounding formation and the external wall of the pile. This type of drive shoe is normally constructed from steel, and remains inside the tip of the pile after it is successfully driven to its designated depth.

Murphy Sarawak was unable to tolerate a permanent reduction in pile ID at the pile tip due to the risk of connection interference and/or hang-up at the pile tip. As an alternative, BJ proposed using an insert made of material other than steel that would perform the same function as the traditional steel drive shoe, but could be removed once pile driving was completed. Using computer simulation to design and test several alternatives involving different materials and methods of installation, BJ settled on 15 mm thick composite material sheets formed to suit the ID of the pipe in question, which were then bonded to the inner bore of the parent pipe. The primary performance criteria for the composite material was it had to exhibit the same properties as the parent steel pipe during the introduction of compressive and tensional stresses that occur during the pile-driving process.

BJ designed inserts and constructed scale models before testing them to destruction to determine the shear potential of the bonding material. Once testing was completed, BJ proposed the new system plans to Murphy Sarawak. The presentation included pile-driving simulations based on the specific soil data for the proposed platform locations, in order to demonstrate the performance of the composite material insert in conjunction with BJ's Specialized Offshore Hydraulic Pile Driving System. Murphy Sarawak agreed to the use of the removable composite material insert, and BJ commenced with fabrication and subsequent installation of the insert(s). The approach involved removing the insert after pile-driving was completed, during the first pass of drill bit when the combined structure pile/conductor string was cleaned out, to just past the shoe. A watermelon mill is located above the bit and set to the ID of the pipe at 33.5 in. By doing so, the tip of the conductor/structure pipe size is returned to the size of the parent bore. Drilling forward then commenced for the casing strings, and was successfully completed on schedule.

"The greatest challenge for us was to devise an easily extractable, cost effective drive shoe that would deliver the same performance as the standard steel unit, but could then be removed permanently from the pile tip. Fortunately, the composite material insert performed well, as indicated in our field testing and pile-driving simulations," Doug Bell, Asia Pacific area manager for BJ Tubular Services, said. "The primary benefit of this approach is that when we remove the drive shoe, we lower the risk of possible connection problems and complications at the pile tip sometimes caused by permanently reducing the pile ID. By preventing these problems, the overall operation is likely to run more efficiently. In the long-run, it is less costly," he added.

BJ has successfully carried out subsequent driving operations related to platform installations in Malaysia for Murphy using the CDDS system.

Looking ahead, BJ will be carrying further similar procedures for other operators in Malaysia, Vietnam and other Asia Pacific markets.

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