Geotechnical

A 1 day forum on Risk Assessment for Submarine Slope Stability with special emphasis on deepwater was organized and conducted with participation from government, academia and industry. In addition, extensive research and compilation of data from literature was conducted to develop a database on submarine slope failures. Because the information required to perform a complete risk assessment was limited, the objective was to develop a database to provide information that can be used to supplement site-specific data for making risk assessments of sea floor stability.

This 2-day workshop examined the current geohazards technology and identify future challenges that industry needs to address. The workshop provided a better understanding of technologies that have a significant impact on deepwater drilling and the lessons learned with deepwater geohazards occurrences. Additional goals of the workshop were to identify and prioritize areas not currently being addressed and to formulate joint industry projects to address these areas. The workshop was held on April 3-4, 2001 at Del Lago Conference Center in Montgomery, Texas.

The project developed a submarine slope evaluation method for critical loading conditions based on well documented case histories. The focus was on geological, geotechnical, geophysical and the related failure mechanisms. The following tasks had been analyzed:

Task A: Study of Case Histories-Case histories of submarine slides in offshore areas worldwide. Appropriate numerical models had been selected for future analysis.

Task B: Submarine Slide Loading Conditions-Loading conditions and triggering mechanisms that exist at sites had been compiled and analyzed.

The JIP developed an advanced seismic analysis method to detect shallow sands that are prone to SWF and to identify which sands will actually flow. The JIP improved detection and identification methods for SWF, which will reduce the occurrence of and risk of SWF. JIP work included laboratory measurements of affected rocks and sediments, pre-processing multi-component seismic lines, computer modeling, and use of specialized seismic analysis techniques.

This project developed contour maps of shear strength for the Central and Western Gulf of Mexico shallow sediments for depths of 0, 5 and 10 feet below mud-line and from shoreline to ~300 ft water depths. Present regulations require that offshore pipelines be buried to a depth of 3 ft. below the mud-line in water depths of 200 ft. or less. An alternative in soft sediments is to allow pipelines to self-bury by virtue of their mass.

Cancelled

This JIP developed an improved methodology for pre-drill pore pressure and fracture gradient prediction for deepwater wells. The JIP conducted a detailed geo-pressure analysis of 60 to 80 deepwater wells using all available data. A Multi-disciplinary team studied the results and formulated an improved methodology for predicting pore pressures and fracture gradients. The JIP held forums and training sessions and prepared a reference document to implement the new methodology.

Cancelled

This is a JIP designed to disseminate new information to address hazard concerns related to hydrates and to stimulate new research. Objectives of the research include: mapping gas hydrates in geophysical context across the Gulf of Mexico, and analyzing new samples of natural gas hydrate. The focus is on reservoir characterization, the effects of gas hydrates on sea floor stability, and on pipeline plugging and potential rupture.

This project will continue development of the earthquake Load and Resistance Factor Design (LRFD) guidelines for offshore structures. The focus is on three topics: 1) concrete Gravity Base Structures, 2) seismic hazard characterizations, and 3) verifying of the proposed ISO guidelines. The unique characteristics of concrete gravity based platforms will be addressed, including seismic loading considerations and soil-structure interaction. The results of selected seismic hazard studies will be reviewed to determine the accuracy of the guidelines for specifying the design spectrum.