Geopressured Geothermal Resource and Recoverable Energy Estimate for the Wilcox and Frio Formations, Texas

Ariel Esposito, Chad Augustine

Research output: Contribution to conferencePaperpeer-review

8 Scopus Citations

Abstract

A supply curve for geopressured geothermal resources is under development to assess the economic feasibility of producing electricity from this alternative geothermal option. Both an analysis of the geopressured geothermal resource in the United States and an analysis of the main economic factors associated with resource utilization are required to develop a reliable supply curve. The main focus of the work to date has been on gathering available data on the geopressured geothermal resource and developing a methodology to estimate the recoverable energy resource. This paper describes the reservoir modeling technique developed to estimate the recoverable energy resource and applies it to geopressured fairways identified in the Frio and Wilcox formations in the Gulf Coast region of Texas, where a large amount of reservoir data is available. An estimate of the geopressured geothermal resource of the fairways in the Wilcox and Frio formations is made using the current geologic data set available. Next, the recoverable energy is calculated by determining the amount of thermal energy and methane energy that could be produced over a 20-year production period. The flow rate of water and methane for wells located in the geopressured geothermal fairways is simulated utilizing the TOUGH2 Reservoir Simulator and data from Bebout et al. (1982;1983) and Gregory et al. (1980).The model uses the EWASG equation of state for H 2O, NaCl, and CH 4 and incorporates relative permeability, capillary pressure, rock compressibility, and leakage from the bounding shale layers (Battistelli et al., 1997). The simulations show that permeability, porosity, pressure, sandstone thickness, well spacing, and gas saturation in the sandstone have a significant impact on the flow rate of water and methane and the percent of energy recovered. Using the results of these simulations, an estimate of recoverable thermal and methane energy can be developed. The results of the simulations predict lower average well production flow rates and a significantly higher production of natural gas relative to water than in previous studies done from 1975 to 1980 (Bassiouni, 1980; Papadopulos et al., 1975; Wallace et al., 1978). Previous studies used analytical models that ignore the development of free gas in the reservoir as the pressure decreases during production and, as a result, underestimate the amount of methane produced with the hot brine. Also, prior studies do not incorporate faults and either set an effective well radius or use image wells to analyze well interference and calculate the total number of wells. Based on the reservoir modeling and simulation completed in this study, multiphase flow processes and reservoir boundary conditions greatly influence the total quantity of the fluid produced as well as the ratio of gas and water in the produced fluid and must be considered to accurately estimate geopressured geothermal reservoir production.

Original languageAmerican English
Pages1563-1571
Number of pages9
StatePublished - 2011
EventGeothermal Resources Council Annual Meeting 2011, Geothermal 2011 - San Diego, CA, United States
Duration: 23 Oct 201126 Oct 2011

Conference

ConferenceGeothermal Resources Council Annual Meeting 2011, Geothermal 2011
Country/TerritoryUnited States
CitySan Diego, CA
Period23/10/1126/10/11

NREL Publication Number

  • NREL/CP-6A20-51648

Keywords

  • Geopressured geothermal energy
  • Reservoir modeling
  • Resource estimate
  • Texas

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