Pressure transient testing of a manmade fractured geothermal reservoir: an examination of fracture versus matrix dominated flow effects

Technical Report · Mon Sep 01 00:00:00 EDT 1980

DOI:https://doi.org/10.2172/5049862· OSTI ID:5049862

Fisher, H N; Tester, J W

The data analysis is in terms of a diffusion equation that determines the flow of water and hence the pressure in the main fracture system, associated joints, and the matrix permeability. The fits of the flow data to type curve solutions of the diffusion equation with pressure-dependent properties for various flow geometries are presented. The following points are considered in detail. (1) The limits on the fracture geometry, aperture, and diffusing areas are determined from the diffusion parameters. (2) Dependence of the parameters (impedance, diffusivity) of the flow-through systems are related to the inflation of the major fractures. (3) The rock properties are related to the reservoir compressibility and permeability. In particular, laboratory experiments have shown that the properties of all sizes of cracks from large single fractures to the microstructure are pressure dependent if the fluid pressure is near the confining stress. The effects of this pressure dependence on the form of the type curves are included. (4) The competition of flow into the various types of porosity (main fractures, joints, and microstructure) and the effect on the interpretation of type curves are considered. The approach described makes an important departure from conventional pressure-transient reservoir analysis in that pressure-dependent properties are incorporated into a numerically simulated generation of type curves resulting from one- and two-dimensional diffusion. In addition, the problem of specifying a unique flow geometry where both matrix and fracture-dominated, non-Darcy flow effects are possible is analyzed using a large amount of field and laboratory data in conjunction with a theoretical treatment that reviews the existing state of the art in reservoir mechanics.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5049862
• Report Number(s): LA-8535-MS
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
FRACTURED RESERVOIRS
FLUID FLOW
TESTING
COMPRESSIBILITY
CRACKS
DATA ANALYSIS
DIFFUSION
FLOW RATE
FLUID INJECTION
HOT-DRY-ROCK SYSTEMS
PERMEABILITY
POROSITY
PRESSURE DEPENDENCE
ROCK MECHANICS
GEOTHERMAL SYSTEMS
MECHANICAL PROPERTIES
MECHANICS
Geothermal Legacy
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