The lower Frio Formation in eastern Brazoria County, upper Texas Gulf Coast, was deposited in a high constructive deltaic environment in the Houston delta system. Constructive elements of the stacked, elongate to lobate deltas that were intersected in core are storm induced delta front splays, delta front slump deposits, and distributary mouth bar, distributary channel and delta plain assemblages. Reworked and winnowed abandonment facies that are volumetrically insignificant relative to constructive elements are subdivided into a crossbedded shoreface-foreshore subfacies and a fine grained cyclic sequence of storm deposits on the lower shoreface that represent a distal abandonment subfacies. Micropaleontological evidence indicates that deposition of constructive and abandonment facies took place in water depths of less than 120 feet.

Twenty-three shale samples ranging in depth from 5194 ft to 13,246 ft from Gulf Oil Corporation No. 2 Texas State Lease 53034 well and 33 shale samples ranging in depth from 2185 ft to 15,592 ft from General Crude Oil Company/Department of Energy No. 1 Pleasant Bayou well were examined by x-ray techniques to determine the mineralogy of the geopressured zone in the Brazoria Fairway. Both wells have similar weight-percent trends with depth for a portion of the mineralogy. Calcite decreases, and plagioclase, quartz and total clay increase slightly. Within the clays, illite in mixed-layer illite/smectite (I/S) increases and smectite in mixed-layer I/S decreases. Four minerals have distinctly different trends with depth for each well. In the No. 2 Texas State Lease 53034 well, potassium feldspar and mixed-layer I/S decrease, kaolinite increases, and discrete illite is constant. In the No. 1 Pleasant Bayou well, potassium feldspar and kaolinite are constant, mixed-layer I/S increases, and discrete illite decreases.

First order leveling to be conducted as part of an environmental monitoring program for a geopressured test well was reported. 39.43 kilometers of first order levels were run to NGS specifications. Twelve Class B type bench marks were set to NGS specifications. The adjusted elevation of bench mark C-1209 was used as a starting elevation and is based on a supplementary adjustment of April 6, 1979 by NGS. The closure for the loop around the well site is -0.65 millimeters. The distance around the loop is 1.29 kilometers, the allowable error of closure was 4.54 millimeters. The initial leveling of this well was performed in 1977. A thorough search for their monumentation was conducted. No monuments were found due to the lack of adequate monument descriptions. Therefore, an elevation comparison summary for this report is only available along the NGS lines outside the well area. The first order level tie to line No. 101 (BMA-1208) was +3.37 millimeters in 17.21 kilometers. The allowable error of closure was 12.44 millimeters.

For a variety of reasons, thousands of oil and gas wells have been abandoned in the Gulf Coast Region of the United States. Many of these wells penetrated geopressured zones whose resource potential for power generation was undervalued or ignored. The U.S. Department of Energy (DOE) Geopressured-Geothermal Research Program was chartered to improve geothermal technology to the point where electricity could be commercially produced from a substantial number of geopressured resource sites. This research program focused on relatively narrow technical issues that are unique to geopressured resources such as the ability to predict reservoir production capacity based on preliminary flow tests. Three well sites were selected for the research program. These are the Willis Hulin and Gladys McCall sites in Louisiana, and the Pleasant Bayou site in Texas. The final phase of this research project consists of plug and abandonment (P&A) of the wells and site restoration.

A field evaluation of geopressured brine injectability was completed during September 22 to 25, 1980 at the DOE, Brazoria test site in Texas. Membrane filters, with pore sizes of 0.4-..mu..m and 10.0-..mu..m, were used as the basis for obtaining suspended solids data and for developing performance-life estimates of typical spent brine injection wells. Field measurements were made at 130/sup 0/C and line pressures up to 3800 psig. Scale inhibited (phosphonate-polyacrylate threshold-type, carbonate scale inhibitor), prefiltered-scale-inhibited, and untreated brine were evaluated. Test results indicated that raw brine was highly injectable, while scale-inhibited brine had extremely low quality. The poor injectability of scale-inhibited brine resulted from partial precipitation of the scale inhibitor.