Diffraction tomography for geophysical monitoring of hydrocarbon reservoirs

An algebraic tomographic imaging technique for diffraction tomograph is discussed that was designed to meet the needs of geophysical tomographic imaging, particularly as applied to monitoring enhanced oil recovery (EOR) projects in hydrocarbon reservoirs. Because geophysical tomographic data are typically gathered in 2-D or 3-D format and are multicomponent in nature and the dimensionality of the data set can be high, the data are usually first processed to obtain a variety of tomograms from which complementary information about the medium can be interpreted. In particular, acoustic velocity changes in heavy oil reservoirs that are being thermally stimulated can be associated with the movement of the thermal front through the reservoir. Additional information can be derived from good data, yielding the elastic moduli of the reservoir rock. Changes in elastic moduli are also associated with certain types of EOR processes including in situ combustion, for example, and represent a change in the character of the medium as a result of the process. Examples of tomograms reconstructed from data taken in hydrocarbon reservoirs are presented