METHOD AND SYSTEM FOR GEOPHYSICAL EXPLORATION

• Main Authors: SONDERGELD, CARL H, RAI, CHANDRA S
• Format: Patent
• Language: English; French
• Published: 30.03.1993
• Edition: 5
• Subjects: DETECTING MASSES OR OBJECTS; GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; MEASURING; PHYSICS; TESTING

The present invention relates generally to a method and system for geophysical exploration and more particularly to a method and system for obtaining selected physical properties of the subterranean formations surrounding a wellbore and for obtaining inverse logs of the selected physical properties so as to aid the geophysicist in evaluating the oil and gas bearing potential of such formations. In one embodiment of the invention, continuous core samples are obtained from along the length of a wellbore. Discrete samples are obtained from the continuous core samples at selected intervals so as to be representative of the formation lithologies traversed by the wellbore along its length. The samples can then be processed at the wellsite with a transportable laboratory so as to obtain measures of a plurality of selected physical properties of the subterranean formations representative of their in-situ condition. An inverse log of each physical property as a function of depth can be prepared with which explorationists can evaluate geophysical survey data for oil and gas potential. In more detail, measures of the subterranean formation's compressional wave velocity, shear wave velocity, bulk density, saturated density, dry density, magnetic susceptibility and compressive strength can be determined from which one can also calculate the formation's acoustic impedance and porosity. Additionally, inverse logs of one or more of the physical properties can be used to perform basin analyses. When used for basin analysis, the physical properties of each inverse log can be used to calibrate geophysical survey data of the basin at one or more wellbore sites within the basin from which the inverse logs were obtained. Having thus calibrated the geophysical survey data, explorationists can then extrapolate the physical properties to other locations in the basin remote to the wellbore site with the geophysical survey data to evaluate the oil and gas potential of the earth's formations at such remote locations. 89179ART0098