ABSTRACT

The northern Gulf of Mexico is a mature hydrocarbon-producing basin. As with most such basins, the average size of newly discovered fields has tended to decrease over time. One hundred and thirty-seven fields were discovered during the period 1970 to 1974, with a mean field size of 53.8 million barrels equivalent and a median field size of 25.5 million barrels equivalent. Ten percent of the fields discovered during that time period contained greater than 140 million barrels equivalent in recoverable reserves. Preliminary data on fields discovered during the period 1990 to 1994, a total of 100 fields, indicates that the mean field size has decreased to 5.6 million barrels equivalent and the median field size has decreased to 2.4 million barrels equivalent. Ninety percent of the fields discovered during this time period are estimated to contain less than 9.9 million barrels equivalent in reserves.

These statistics have a profound message for companies exploring in the northern Gulf of Mexico. Business models must either allow for small fields to be discovered, developed and produced profitably or must contain strategies for finding larger than average fields. Methods for exploiting small fields profitably may include use of seismic attributes to minimize dry holes, innovative development methods to reduce costs, and reducing cycle times to improve the rate of return on investment. Methods for finding larger than average fields should include focusing on less mature plays. Recent discoveries in the sub-salt, in the Vicksburg in Galveston Bay and in the lower Cretaceous carbonates of the eastern Gulf illustrate that less mature plays do exist in the northern Gulf of Mexico and are capable of containing fields with large reserves.