A reduced degree of freedom model for thermal permeability enhancement in blocky rock

Journal Article · Sun Jan 01 04:00:00 UTC 1989 · Geothermics (International Journal of Geothermal Research and its Applications); (UK)

OSTI ID:5795057

Xiang, J ^[1]; Elsworth, D ^[2]

---

1. Dept. of Mineral Engineering, Pennsylvania State Univ., University Park, PA (US)
2. Waterloo Centre for Groundwater Research, Univ. of Waterloo, Waterloo, Ontario N2L 3G1 (CA)

An upwind-weighted finite-element model is presented for the analysis of non-boiling hot dry rock geothermal systems. The model accommodates the essential mechanisms of permeability enhancement or degradation resulting from injection of fluid at a temperature different from ambient. The effects of induced thermal strains and fluid pressures in conditioning both normal and shear displacements in an ubiquitously jointed continuum are accommodated. The mass is idealized as a blocky assemblage where diffusive-advective energy transport in the fracture system is augmented by transient heat supply from intact rock blocks. The true transient nature of both energy supply from the blocks to the percolating fluid and the development of thermal strains within the medium are determined analytically. The local assumption of full lateral restraint coupled with analytical representation of thermal strains renders the nonlinear initial-value problem fully defined in terms of the two dependent variables of fluid pressure and fluid temperature only. Subject to these assumptions, complete fluid-pressure and fluid-temperature histories of large, thermally stimulated reservoirs may be determined effectively and efficiently. Results are presented for both single point injection and dual point injection-withdrawal scenarios to illustrate the possible scope of the method.

• OSTI ID: 5795057
• Journal Information: Geothermics (International Journal of Geothermal Research and its Applications); (UK), Journal Name: Geothermics (International Journal of Geothermal Research and its Applications); (UK) Vol. 18:5/6; ISSN GTMCA; ISSN 0375-6505
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150200* -- Geology & Hydrology of Geothermal Systems
150902 -- Geothermal Engineering-- Fluid Transmission
152003 -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
ANALYTICAL SOLUTION
ENERGY SYSTEMS
ENHANCED RECOVERY
FINITE ELEMENT METHOD
FLUID FLOW
GEOLOGIC MODELS
GEOTHERMAL FIELDS
GEOTHERMAL SYSTEMS
GEOTHERMAL WELLS
HOT-DRY-ROCK SYSTEMS
NUMERICAL SOLUTION
PERMEABILITY
PHYSICAL PROPERTIES
PRESSURE GRADIENTS
RECOVERY
STIMULATION
THERMAL CONDUCTIVITY
THERMAL RECOVERY
THERMODYNAMIC PROPERTIES
WELL STIMULATION
WELLS