Abstract: Use of Permanent Downhole Geophones as a Tool for Reservoir Behavior Characterization

DEFLANDRE J.-P., J. LAURENT, P.-C. LAYOTTE, F. HUGUET and F. VERDIER

Downhole geophones have been developed for use in a permanent way (several years) in producing oil or gas wells. These geophones were designed to be installed between the casing and the tubing. They can be adapted to different well completions.

Such geophones are suitable for two types of applications: microseismic monitoring and 4D-seismic measurements. Installing 3-component permanent geophones close to the reservoir level enables the recording of microseismic events of small magnitude (less than -1). The data obtained make it possible to locate the mechanically active zones associated with fluid injection or withdrawal.

For 4D-seismic measurements, these downhole geophones enable the easy setting of multiazimuthal borehole seismic to monitor, in a repeatable way, seismic parameter variations in the instrumented wellbore vicinity.

These two applications have been successfully used in two different underground gas storage reservoirs since 1991. Results obtained at the first site were used to improve the technology of the arrays. At the second site one well has been equipped with 15 permanent downhole geophones and used since June 1993 to locate gas displacement in the vicinity of this wellbore. This evaluation was performed on the basis of both travel time variations and acoustic impedance variations.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria