COMBINING LASER MEASUREMENTS WITH BACKWARD WAVE TECHNIQUES FOR EVALUATION OF UNDERGROUND OPENINGS IN OIL SHALE

SUCCESSFUL COMMERCIALIZATION OF OIL SHALE WILL INVOLVE LARGESCALE UNDERGROUND MINING OR RETORTING, AND WILL REQUIRE SUPPORT TECHNOLOGY TO EVALUATE THE INTEGRITY OF SUPPORT PILLARS, MINE ROOF ROCK, AND OTHER LARGE STRUCTURES IN OIL SHALE. IN ORDER TO ELIMINATE TIME CONSUMING AND OBTRUSIVE EVALUATION METHODS INVOLVING CONTRACT TYPE DETECTORS (GEOPHONES, ACCELEROMETERS, ETC.), IT IS PROPOSED HERE THAT OIL SHALE STRUCTURES BE EVALUATED BY NONCONTRACT OPTICAL METHODS. IN PARTICULAR, WE PROPOSE THAT THE RESPONSE OF ROCK STRUCTURES TO VARIOUS TYPES OF ACOUSTIC EXCITATION BE MEASURED AND RECORDED USING A LASER AND OPTICAL INTERFEROMETRIC TECHNIQUES. ONCE THESE ARRAY MEASUREMENT TECHNIQUES ARE FULLY DEVELOPED, WE FURTHER PROPOSE THAT OPTICALLY GATHERED ACOUSTIC DATA BE PROCESSED BY "BACKWARD WAVE PROPAGATION" TECHNIQUES. THESE TECHNIQUES WILL ALLOW US TO DETERMINE THE STATE (STRESS FIELD, CAVITIES, INCLUSIONS, ZONES OF FRACTURED ROCK, ETC.) OF THE ROCK VOLUME ADJACENT TO THE ROCK SURFACE BEING EXAMINED OPTICALLY. THIS DEMONSTRATED CAPABILITY WOULD LEAD TO THE DEVELOPMENT OF RAPID, INEXPENSIVE TOOLS FOR THE EVALUATION OF LARGE STRUCTURES IN ANY KIND OF ROCK, AND IN PARTICULAR, LEAD TO PRACTICAL EVALUATION METHODS FOR LARGE UNDERGROUND STRUCTURES IN OIL SHALE. THE INCREASED SAVINGS IN TIME AND MONEY AND THE ENHANCED SAFETY TO PERSONNEL WOULD MORE THAN OFFSET THE COST OF DEVELOPMENT.