- Copyright © 2001 Society of Exploration Geophysicists
Physical properties of shallow-water flow (SWF) sands differ from most reservoir and seal rocks studied for petroleum purposes. These materials exist near the transition zone between rocks and sediments. Our investigations, the subject of this article, suggest that physical properties of SWF sands are amenable to a prediction methodology that uses high-resolution multicomponent seismic data.
SWF sands are a primary hazard to deepwater drilling operations in the Gulf of Mexico. They have the potential to result in well failures and significant discharges of subsurface fluids into the ocean. However, at present, most operators make only a modest attempt to identify SWF before drilling. They drill through these hazards and mitigate any resulting damage at significant expense if one is encountered. This is not rare. According to a report from Fugro Geoservices, approximately 70% of all deepwater wells have experienced SWF.
A method for predrill delineation of sands that are close to failure, and thus likely to exhibit SWF, would be advantageous in selecting optimal drilling locations and in developing cost-effective well plans. The current method of identifying SWF involves predrill hazard studies utilizing conventional and high-resolution seismic data to identify zones that might produce SWF. However, the high incidence of SWF mitigation events in deepwater wells shows that existing techniques do not provide adequate resolution or accuracy.
At present, no robust seismic method exists for accurately identifying and characterizing SWF. Operators do not have the option to avoid the hazard instead of mitigating the problem after it has started. A new method is required that will permit operators to identify the hazard before the well is drilled.
Using seismic data for accurate understanding of the physical properties and deformational behavior of SWF sands is essential to characterization, prediction, and interpretation of these stratigraphic units. To date, very few core and …