Anchoring Flowlines, FPSOs and Rigs in Deepwater – The Torpedo Pile

New Wave Media

Among the many challenges facing E&P in the Brazilian deepwater pre-salt plays, is that of anchoring the flowlines, platforms, FPSOs and even buoys to the seabed which can be over 2000 meters deep. Petrobras has developed a simple and efficient method of doing this through the Torpedo Pile.

In the case of the deepwater pre-salt plays in Brazil, specially at the Santos Basin, the distance from land to some of the proven plays like Tupi and Iara, which are around 300km from shore and pose complex logistics problems even on surface structures. Challenges, such as how to anchor a deepwater rig or FPSO to the seabed 2,200 meters down must be resolved. It is a long distance for anchors to travel, normally four or more anchors are used and these anchors need to be aligned. Petrobras has developed, through its technology center, an excellent solution in the torpedo pile anchor system. The torpedo pile is a promising deepwater anchoring system due to its low manufacturing and installation cost and its reliability and operational simplicity.

Petrobras was awarded its Brazilian patent for the torpedo pile in 1996 and since then has anchored more than 1,000 deepwater flowlines, rigs and FPSO´s using the torpedo pile.

Typical dimensions of the Torpedo pile, for MODU anchorages is a 30 inch external diameter and 12 meter length. For FPSO anchorage the external diameter increases to 42 inches with a torpedo length of 15 meters. Another reason why torpedo piles are considered the best solution for semi-submersible rig and FPSO anchoring in deep waters is that they only need a PSV for transport and launching. After launching they reach the seabed through their weight and the pull of gravity. The stabilizing fins, conical tip, ballast help the torpedo pile penetrate the soil by attaining a high free-fall velocity also through the effects of its weight and gravity.

The torpedo is basically a solid cylindrical structure with a pointed end forward and four elongated fins that go from around its midsection almost to its end, where it is secured to a heavy duty chain. They were first used to anchor flexible lines, but are now commonly used to anchor MODUs, rigs and FPSOs in deepwater.

They have proven their efficiency in the deepwater pre-salt and other deepwater plays in Brazil and are now in extensive use by Petrobras. Their use is not limited to Brazil either, as Petrobras will be using them in WA and has licensed Intermoor Inc. to produce and install the torpedo pile in its deepwater plays and for other companies in the GOM.

 

Claudio Paschoa

Photo courtesy of Intermoor Inc.