HR: 13:40h
AN: H13G-01 INVITED     [Abstracts]
TI: Using Time-Lapse Geophysical Estimates of Pressure Change to Image Permeability
AU: * Vasco, D W
EM: dwvasco@lbl.gov
AF: Earth Sciences Division, Berkeley Laboratory, Building 90-1116, 1 Cyclotron Road, Berkeley, CA 94720 United States
AB: Estimates of fluid pressure and saturation changes provided by time-lapse geophysical methods are sensitive to reservoir flow properties, such as permeability. As shown in this talk, given high-resolution estimates of pressure changes in the subsurface, one may define a linear equation for permeability variations. In effect, the inverse problem for permeability, which in most settings is decidedly non-linear, is mapped into a sequence of linear sub-problems. The resulting linear inverse problems may be solved efficiently using sparse-matrix techniques. Two applications demonstrate the feasibility of this approach. The first application utilizes a set of tilt and borehole pressure data from a field site at Raymond, California. The observations are associated with a well test in which fluid is withdrawn from a shallow fracture zone. I am able to image a high permeability, north-trending channel within the fracture zone. The second application is to a set of crosswell saturation and pressure estimates from a CO$_2$ flood at the Lost Hills field in California. The resulting permeability estimates agree with a permeability log in an adjacent well and are in accordance with water and CO$_2$ saturation changes imaged in the interwell region.
DE: 5100 PHYSICAL PROPERTIES OF ROCKS
DE: 1832 Groundwater transport
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting