Summary
Objective
Develop and calibrate a method to predict penetration and pullout capacity for torpedo anchor piles. Torpedo piles could be used in the Gulf of Mexico as anchors for temporary and permanent mooring systems and as conductors for deepwater wells. This work will produce data from laboratory-scale and field-scale model tests so that design methods can be validated and calibrated.
Introduction
Recently, US operators have shown an increased interest in using torpedo piles for anchoring deepwater facilities. They provide a potentially economic alternative to conventional anchors. Petrobras has reported the successful use of torpedo piles both as anchors and more recently as well conductors.
Fugro (a geotechnical consultant) is currently sponsoring a 2-year long research effort at the University of Texas on the methods to predict torpedo pile penetration and performance. This research is intended to address fundamental concepts ands is not directed at a particular, proprietary type of anchoring system. Applications could include a variety of pile types and even surface conductors for deepwater wells.
This ongoing research project started in September 2005 and is expected to be completed by September 2007. The project consists of four phases. The first phase consists of a thorough review of the literature about torpedo piles and other seafloor penetrator experiments. The second phase consists of developing a set of design models to predict the penetration and the capacity of torpedo piles as a function of seafloor velocity, pile geometry and soil shear strength. The third phase consists of conducting a series of 1:30 model torpedo pile experiments at The University of Texas at Austin using their large soil bed facilities. The data will be used to calibrate the design models. The final phase will consist of performing a limited number of offshore field tests using a 0.3-m-diameter, 6-m-long torpedo test pile. These data will be used to further calibrate and validate the design models in field conditions.
A JIP has been recently formed with support from Fugro, ExxonMobil and Shell to fund the offshore test. The cost of the offshore test alone is approximately $150,000. Participants have agreed in principal to MMS participation for a minimal participation fee. MMS will be given access to the confidential data that are produced, will be able to review and provide comments for project reports, and will be given an opportunity to provide guidance to the research effort. The confidential information will remain proprietary to and publishable by Fugro, ExxonMobil, and Shell.
Benefits to MMS and Industry
Torpedo piles can provide a significant economic advantage for anchoring mooring systems in deepwater. It is beneficial both for MMS and industry to develop a fundamental and common understanding of torpedo pile behavior before a project-specific design is developed and needs to be evaluated by MMS. This project affords this opportunity to the MMS to provide input and have timely access to results at a minimal cost.
Deployment of Results
The results will be deployed in project reports, technical papers and a set of calibrated design methods.
Project Plan
Scope and Plan: Additional laboratory model data will be obtained. The predictive models will be calibrated with laboratory data. The field tests will be conducted, and the data will be used to validate the calibrated design models.
Related Publications
Audibert, J.M., Morvant, M.N., Won, J.Y., Gilbert, R.P. 2006. “Torpedo Piles – Laboratory and Field Research,” International Society of Offshore and Polar Engineers, San Francisco, June 2006, Paper No. 2006-PCW-03.
