PRE-CRUISE ESTIMATES OF SEDIMENT PROPERTIES FOR THE 2005 CHEVRONTEXACO ET AL GULF OF MEXICO GAS HYDRATE RESEARCH CORING PROJECT

Emrys H. Jones
ChevronTexaco Energy Technology Company

Natural gas hydrates are known to occur in the Gulf of Mexico (GOM). However, the extent of, and effects that hydrates have on sediments is not well understood. In order to improve the understanding of these sediments ChevronTexaco, its JIP partners, and the DOE conducted scientific drilling in the GOM. Drilling was conducted to obtain log data and cores of hydrate bearing sediments. These data will increase the basic property data base on hydrate sediments and will be compared to pre-cruise seismic predictions of the sediment properties.

Pre-cruise planning for the holes included a detailed 3D seismic analysis preformed by WesternGeco, a USGS high resolution seismic survey, heat flow measurements by Georgia Tech, and piston cores and deep towed data by NRL. The two areas in the GOM studied were Atwater Valley and Keathley Canyon. These locations are nearly the same water depth but differ in almost every other respect.

The Atwater location is in the Eastern Gulf in the middle of the geologic feature called the Mississippi Canyon. It has numerous mounds and evidence of salt diapirs and fluid flow effects. Bottom Simulating Reflectors (BSRs) are generally not noticeable. However, the targeted mound does show an indication of a BSR on its flanks. 

The Keathley Canyon location is in the Western Gulf, at the top of ridge separating two mini-basins. The location has a strong seismic signature indicating a BSR and areas of trapped gas. Some evidence of mounds can be found but they are not the dominant feature. 

This paper discusses the pre-cruise estimates sediment mechanical and acoustic properties that are expected from seismic and well bore models developed by the JIP.