NRC FINDS MMS TOO CONSERVATIVE ON GEORGES BANK DATA

The Minerals Management Service was too conservative when it estimated the potential oil and gas resources on Georges Bank off New England, the National Research Council says.

MMS estimated a mean of 40 million bbl of economically recoverable crude oil in the basin.

In a report MMS asked for, NRC said there are five potential exploration plays in the region, but wells drilled so far tested only one type of play.

NRC's report said, "While those wells-two Continental Offshore Stratigraphic Test (COST) wells and eight unsuccessful industry exploratory wells-have provided a large amount of stratigraphic, geochemical, and geophysical data, those data do not necessarily hold for the other four play types.

"Because information from wells is lacking for all but one play in the basin, the MMS estimates of undiscovered hydrocarbon resources are based primarily on identification of structures from the available geophysical information."

HIGHGRADING PROSPECTS

In any frontier province, NRC pointed out, the first efforts to find oil and gas focus on the most obvious structures, which results in the less obvious stratigraphic and combination type traps remaining unrecognized at first.

"This practice contributes to the geological uncertainty in the MMS evaluation because it overlooks the possible contribution of unidentified structural and stratigraphic trapping to the resource base," NRC said.

"In addition, variations in porosity may go undetected, yet they may form stratigraphic traps with as much potential as areas of uniform porosity arched over low relief structures."

NRC said geochemical analyses based on data from the wells show that strata within the region's main subbasin are organically lean. The type of kerogen in the older sedimentary rocks commonly produces gas, while the type of kerogen in the younger Cretaceous strata generally produces oil under appropriate thermal conditions.

The hydrocarbon source in the COST G-1 well was predominantly gas producing, and the source in the COST G-2 well, carbonates and shale, is more oil prone, with some natural gas associated to it.

EXTRAPOLATING DATA

NRC said data from the 10 Georges Bank wells, all in the same subbasin, should not have been extrapolated to characterize the average amount of economically recoverable undiscovered hydrocarbons in the basin because the other plays are different and must have independent hydrocarbon sources based on structural and geographic locations.

Poor exploration results in the Baltimore Canyon, about

500 km southwest of Georges Bank, appear to have played a major role in the MMS resource evaluation of Georges Bank, NRC said. In contrast, no consideration was given to the more successful exploration programs in the geologically similar Canadian areas to the north.

"The appropriate weight that should be given to these related areas can be determined by the use of play summary maps of the source reservoir and trap conditions in the Canadian sector to see if any favorable trends can be projected into the U.S. part of the area," it said.

NRC recommended that each of the identified plays on Georges Bank be drilled to obtain geochemical and stratigraphic data, that MMS obtain reprocessed and more recent seismic data for all basin parts, and that MMS upgrade to industry standard data processing equipment and techniques for play and prospect evaluations.