Statistical Look of the Hydrocarbon Prospectivity of Undiscovered Subsalt Plays at the Mexican Side of the Deepwater Gulf of Mexico Basin

摘要

The iikeliness and the size of undiscovered subsalt fields in the Mexican side of the deepwater portion of the Gulf of Mexico Basin are investigated and discussed. The continuity of the geological setting from the U.S. side into the Mexican side of the basin and the comparison between the total plays versus the subsalt plays of the whole basin suggests the presence of undiscovered subsalt resources south of the international border. Basinwide, there is a probability ratio of subsalt plays having as much as 1.3 times the volume of hydrocarbon as the above salt ones. Although subsalt Miocene plays have a share of reserves greater than that of subsalt Lower Tertiary plays, spatial distribution of these trends suggests that the latter plays may predominant south of the border. Statistical evidence suggests that there is a chance of finding one subsalt field with a subsalt play for every four fields with plays of any kind that are discovered. The cross plot of the areas of the fields and the distribution of reserves shows a dispersed cloud of points loosely suitable to be analyzed even with the use of confidence bands. The logistic function reduces the uncertainty of this situation and provides a meaningful insight in the connection between the areas and the dimension of reserves of the fields. The cumulative frequency curve of the volume of reserves of subsalt fields in the U.S. side of the basin is applied to constrain the expected volume of reserves in the Mexican side. Between the first quartile and the median size of undiscovered subsalt fields, the sizes could be from one and a half up to two and a half times bigger than the size of the largest above-salt field already discovered in the Mexican side of the basin. However, this promising appraisal is tempered by the analysis of risked probabilities, which shows that the overall odds against a commercial discovery at the basin are 7 to 3.