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ELECTRICAL DETECTION OF FRACTURES IN BOREHOLES.

Objective

TO DEVELOP FURTHER THE FRACTURE LOGGING TOOL ORIGINATED BY THIS CONTRACTOR SO THAT IT CAN BE USED TO MONITOR FRACTURES IN A BOREHOLE DURING THE PROCESS OF HYDRAULIC FRACTURING.
The apparatus is intended for studying fractures produced artificially by hydraulic overpressure in a borehole, during the actual process of fracturing.
To achieve this, the instrument measures, twice per second, the electrical conductance of the wall of the compression chamber at 160 different points, and presents the results in the form of an image obtained in real time.
The appearance of a fracture is in most instances accompanied by a local increase in conductance, enabling the fracture to be detected and its dip and strike to be determined. The first tests, carried out at Mayet de Montagne, France, were successful. However, since the artificially produced fractures are very small, the signals have to be processed in order to obtain images of acceptable quality.
The instrument can also demonstrate the existence of natural fractures in the wall of a borehole during a conventional logging operation.
THE TOOL WILL BE DESIGNED TO FIT INSIDE A STRADDLE PACKER ASSEMBLY AND TO SEND SIGNALS TO THE SURFACE DURING THE PROCESS OF HYDRAULIC FRACTURING. IT WILL CONSIST OF 10 RADIAL ASSEMBLIES, EACH WITH 16 ELECTRODES, WITHIN A PACKER CHAMBER 1 M HIGH. DATA FROM THE ELECTRODES WILL BE SAMPLED BY DOWN-HOLE ELECTRONICS AND MULTIPLEXED TO SURFACE VIA A 7-CONDUCTOR CABLE. IT WILL PERMIT THE DEVELOPMENT OF FRACTURES TO BE FOLLOWED IN REAL TIME WITH A RESOLUTION OF 0.1 SEC.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Address
Avenue Denfert-rochereau 77
75014 Paris
France