An Application of Crosswell Tomography Using a Hydrophone Receiver Array and Airgun Source to Monitor Steam Migration in-an Unconsolidated, Heavy-oil Sandstone, West Coalinga Field, California

Dale M. Blevens and John W. Fairborn

This crosswell tomography field trial demonstrates the viability and cost reducing benefits of a hydrophone receiver array and airgun source for monitoring steam (heat) migration within an unconsolidated, heavy-oil sandstone. This project represents one of the first applications of hydrophone receivers in such an environment. Data quality from the hydrophone array proved more than adequate for P-wave tomography while costs were reduced dramatically from estimates using a clamped geophone array. Additionally the resolution provided by the capture of travel-time data from interwell areas offered a distinct advantage over conventional monitoring techniques limited to observation wells.

Two crosswell surveys were conducted in the vicinity of a new, infill steam injector. The purpose was to monitor steam migration within an 80-foot thick, sandstone interval by detecting the heat-induced velocity decrease between the first survey, conducted just before steam injection, and the second survey conducted approximately three months later. Difference plots of the two surveys clearly define regions of significant temperature change and contact temperature logs corroborate the zone of peak change. The crosswell tomography data and the inferred steam migration characteristic immediately altered an operational strategy for the drive and were later a factor in the abandonment of continuous steam injection.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California