Mark Mathews
Los Alamos Scientific Laboratory, University of California
Los Alamos, New Mexico
ABSTRACT
At the present time, geophysical well logs are not calibrated for igneous and metamorphic lithologies or for fracture porosity. These geologic conditions are routinely encountered in geothermal reservoirs and geothermal fields.
Geophysical well logs are generally continuous records of various measurements plotted versus depth. For these measurements to have meaning, they must be related to generally accepted standard units by a valid and specified system of comparison. Accurate measurement and recording of log data is necessary for effective well evaluation, reservoir engineering assessment, and subsurface geological or geophysical appraisal. Proper interpretation of log data provides accurate subsurface geologic parameters. Calibration data that is auxiliary to the log data will show the degree of log accuracy and indicate the reliability of the estimated subsurface geologic parameters, when the log data is reviewed with a knowledge of the calibration procedures.
Three large calibration models or test pits are presently being fabricated. Each calibration model will be constructed of large stone blocks which have a cored-borehole and wire-sawn simulated fractures. Details of the test pits size, simulated fracture locations, rock type of each test pit, and location and access of these pits are discussed. Supporting data from rock properties of similar rock that will be used in each test pit are included.