| Popis: |
Abstract It is the purpose of this paper to present data on brines occurring in the Frioformation of the Texas Gulf Coast, and to show how their composition varies,with depth below the surfacewith depth below the top of theformationalong the approximate strike. The brines vary in chloride content from 3,180 to 73,000 p.p.m., though theaverage salinity of the salt waters is shown to vary with total depth; theconcentration being 35,000 to 40,000 p.p.m. at 3500 to 5500 ft., slightly lessthan 50,000 p.p.m. chloride at 5500 to 6500 ft. and average 38,000 to 40,000below 6500 feet. From the analyses available, it appears that the highest concentration of saltsoccurs in the upper 300 ft. of the formation, while lower salinity is foundwith increasing depth below this point. The salt waters from wells in Starr County show less concentration of dissolvedsalts than in any other group of wells farther north along the strike. In all, 116 analyses from 63 fields and 14 wildcats, from depths ranging from1300 to 11,400 ft. below the surface and from 2 to 3240 ft. below the top ofthe Frio, are recorded. Introduction Brines have been studied for many years in' an attempt to solve some of thegeologic and production problems associated with the production of oil and gas.One practical application of study of water analyses is the correlation ofwaters occurring above, in, or below the producing sand in the same field orthroughout the same formation. The Frio formation, the series of sands and shales occurring below theMarginulina zone and above the Vicksburg, is.one of the major oil andgas-producing formations in the Texas Gulf Coast. Fossils are rare or absent inthe upper Frio throughout most of the area. When available, cuttings and cores, and electric logs were used to determine the top of the Frio. A change inlithology was used to determine this point in most of the wells, and fossilswere used in some of the deep wells. It is realized that a change in lithology is not perfect for correlationpurposes over long distances and some of the trends may be influenced by theinability to differentiate between the nonfossiliferous Marginulina zone andthe Frio. It underlies virtually all the area shown on the accompanying map(Fig. I). Although it is not productive in the up dip facies, it has beenexplored to a limited degree below 12,000 ft. Furthermore, toward the coastline future drilling to deeper depths should encounter this formation. Although thousands of wells have penetrated or drilled entirely through theformation, very few water samples have been secured from the many sandsoccurring in this formation and analyzed. Previous Investigation No previous published study has been made of the chemical composition andconcentration of waters from the Frio formation. T.P. 1729 |
