Techno-Economic Feasibility of Geothermal Deep Direct-Use Systems in Grimes County, Texas

Abstract

This study evaluates the techno-economic feasibility of a deep direct-use geothermal system in Grimes County, Texas. The system consists of a doublet system, including an injector and a producer. Fluid is extracted from the subsurface for heat utilization at surface facilities and is reinjected as cooled fluid. A numerical model is developed to simulate the performance of the doublet system. The simulation time is 30 years for analyzing long-term behavior. A deep formation - the Austin Chalk, with formation top ranges from 13,000 ft (3,962 m) to 15,500 ft (4,724 m) of true vertical depth (TVD) - is selected as the reservoir formation due to the favorable sealability of the Midway and Taylor shales above. The permeable layer is sandwiched between low-permeable formations. The reservoir is assumed to be brackish water, without any hydrocarbons. Techno-economic analysis is conducted to assess economic feasibility. The sensitivity of formation characteristics such as porosity and permeability can also be modeled to examine the reservoir impact on energy production. The results of the reservoir simulation evaluate the dynamic performance of the direct-use geothermal system. Produced temperature profile, changes in reservoir pressure over time, and the amount of energy stored are simulated. Techno-economic analysis incorporates simulation results to assess the economic indicators, such as the levelized cost of energy. Additionally, the evaluation considers both technical and economic performance to provide a comprehensive assessment.