| Title | Joint Geophysical Imaging of Poroperm Distributions in Fractured Reservoirs |
|---|---|
| Authors | Malin, Peter; Leary, Peter; Shalev, Eylon; Onacha, Stephen |
| Year | 2009 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Fractures; Fracture Heterogeneity; Percolation; Flow; Seismic Velocities; Magnetotellurics; Shear-wave Splitting |
| Abstract | Fracture control of reservoir flow is manifested in two closely similar spatial fluctuation relations operating at opposite ends of the reservoir scale spectrum. At cm-scales, fluctuations in wellcore porosity ? and permeability ? from oil-field clastic reservoirs are related by ?? ~ ?log(?), ? denoting spatial variation on the order of cm to m. At hundred-meter scales, variations in seismic velocity ? and electromagnetic resistivity ? in the Krafla Iceland geothermal reservoir are related by ?? ~ ?log(?), ? denoting spatial variations on the order of 100m to km. We suppose that small-scale well-core porosity ? and large-scale bulk seismicvelocity ? are responding to spatial variations in grain-scale fracture density at their respective scale lengths. We similarly suppose that small-scale well-core permeability ? and large-scale bulk electrical-resistivity ? are responding to variations in spatial connectivity that form percolation flow paths at their respective scales. These two expressions thus encourage interpreting seismic and electromagnetic field data using unifying data inversion based on the micro-to-macro scaling property of grain-scale fracture density fluctuations. The grain-scale fracture density interpretation of scale-independent jointfluctuation relations is strengthened by Krafla seismic shear-wave and magnetotelluric-phase bulk data indicating the existence of stress-aligned-fractures that induce shear-wave anisotropy and promote fracture-related flow in the high-productivity region of the geothermal field. |