Development of an assessment methodology for geopressured zones of the upper Gulf Coast based on a study of abnormally pressured gas fields in south Texas

Detailed study of the producing gas fields in south Texas has identified a total of 47 abnormally pressured fields in a six-county area including Hidalgo, Brooks, Cameron, Willacy, Kenedy, and Live Oak Counties. An assessment methodology for assessing the potential of the deep geopressured zone in south Texas as an energy resource was developed, based on investigation of the reservoir parameters of these fields. This methodology is transferrable to broad areas of the Gulf Coast. The depth of the geopressured zone in the study area ranges from 7000 ft in western Hidalgo to 12,000 ft in central Cameron County. Temperature data from within the fields, corrected to undisturbed reservoir values, yields a 300/sup 0/F isogeothermal surface at depths from 10,500 ft to 17,000 ft over the study area. The question of fluid deliverability was found to be paramount in determining the potential of the geopressure-geothermal resource as a practical source of energy. The critical parameter is the effective reservoir permeability throughout the study region. Individual fields were assessed for their potential to produce large quantities of geothermal fluid based on reservoir study and detailed geological investigation. Five locations within the study region have been selected as potential candidates for furthermore » evaluation and possible eventual testing. Based on investigation of permeability and temperature, the upper limit of fluid temperature likely to be produced in the lower south Texas study region is 300/sup 0/F. In Live Oak County, the possibility of producing fluid at higher temperatures is somewhat improved, with a reasonable possibility of producing fluid at 350/sup 0/ to 375/sup 0/F.« less