Detection of Mobile Fluids in the subsurface By Dr. Kandiah [BALA] Balachandran Kalamazoo, MI Kalamazoo Valley Community College

Experiments Comparatively strong horizontal component signature was recorded at near normal incidence at a field site near Tulsa, Oklahoma which led to this investigation. A simple set-up simulating a two-layer medium was constructed using a thick block of aluminum glued to a slab of Berea sandstone.

Experiments (contd.) A P-transducer was placed on top of the Al block to generate the waves that were reflected at the interface. Both P- and SV- reflected waves were recorded at various offsets. The experiment was done with dry rock first. It was repeated with the rock in a bath of water.

SV- to P- amplitude ratios S-wave amplitudes and the corresponding P-wave amplitudes were measured and the ratios were calculated as a function of offset The theoretical solution to the expected amplitudes were obtained using solutions to Zoeppritz equations made available on the Web by the CREWES project of the University of Calgary (Charles Ursenbach)

Observations The SV to P amplitude ratios were significantly larger when the rock was wet than when it was dry. This was more noticeable at larger angles of incidence. The following slides show the experimental data and the theoretically expected ratios of these amplitudes. These results are preliminary.

Further work July 2005: at Colorado School of Mines Repeated the experiment with some measurement of saturation of the rock – not very successful Repeat with light oil in the pores Repeat with heavy oil in the pores Improve the design of the experiment so higher subsurface pressure environments can be simulated…

Conclusions The observations suggest that the presence of mobile fluids may be determined by studying the ratios of the amplitudes of the SV to P reflections and it just may be possible to identify the fluid. Plans are being made to study these variations with available data from 3- Component surveys acquired in select areas.