Advanced Horizontal Well Recirculation Systems for Geothermal Energy Recovery in Sedimentary Formations

Horizontal well pairs for closed loop geothermal recovery system

Horizontal well pairs for closed loop geothermal recovery system (optimally separated depending on formation structure and properties)

Horizontal well technology has advanced rapidly in the past 10 years, allowing new economic production from both conventional and unconventional resources (including shale gas and heavy oil thermal developments). For thermal enhanced oil recovery, advanced horizontal well pair and multi-well configurations and operating practices have allowed development of significant new heavy oil production through application of steam assisted gravity drainage systems (SAGD), cyclic steam stimulation operations (CSS and “huff and puff”) and horizontal assisted steam drive system (HASDRIVE). To date, however, such innovative horizontal well systems and technology have not been widely transferred or applied within the Geothermal Energy Industry. The key impediments have been high well costs (which are declining with improved drilling technology) and limited design optimization and economic studies.

Terralog and the University of California, Irvine, propose to investigate and develop advanced design concepts for paired horizontal well recirculation systems, optimally configured for geothermal energy recovery in permeable sedimentary formations. One or more horizontal well pairs (which may be spaced vertically or laterally depending on formation properties) are placed to establish a (relatively) closed loop recirculation system.

We plan to investigate and develop this innovative approach for geothermal resource development through a combined research effort of geologic resource identification, engineering analysis, numerical simulation, small scale and large scale laboratory investigations and validation experiments, and detailed economic analyses. The research effort will proceed in two phases, over three years and will include the following tasks:

  • Geologic resource identification, characterization, and documentation
  • Engineering feasibility studies and numerical simulations
  • Preliminary design optimization for a range of formation and fluid properties
  • Laboratory investigations and validation experiments at the core scale (1D flow) and small block scale (2D flow), and larger block scale (3D flow), with comparison to numerical simulation results
  • Detailed simulation and design optimization for specific geologic formations in the US
  • Detailed energy and economic evaluations and documentation for specific resources in the US

Application of advanced horizontal well circulation system technology in permeable sedimentary formations provides a number of significant environmental advantages over traditional geothermal recovery and enhanced geothermal systems in low permeability crystalline formations. These include: 1) Eliminating the need for hydraulic fracturing; 2) Significantly reduced risk for induced seismicity; 3) Reduced need for surface wastewater disposal; and 4) Potential combination with CO2 sequestration.

This project will identify expanded opportunities for geothermal energy development in the US with lower environmental risk. It will contribute unique and critical laboratory data for porous flow and geothermal heat recovery in sedimentary rocks. And it will provide practical design guidelines and detailed economic analyses for horizontal well circulation systems for geothermal energy recovery.

Sample numerical model cross section to evaluate porous flow and heat transfer between horizontal well pairs for varying design configurations, formation properties, and fluid properties

Sample numerical model simulation results

Sample numerical model cross section (top image) and simulation results (lower image) to evaluate porous flow and heat transfer between horizontal well pairs for varying design configurations, formation properties, and fluid properties