Seismic inversion for reservoir delineation and description

Seismic inversion can be used to derive acoustic impedance information from seismic data. The seismic inversion methods globally optimised nonlinear seismic inversion and fully linear seismic inversion are introduced to describe a porous Zechstein carbonate interval in Denmark as a correlation exists between the acoustic impedance and porosity. The globally optimised non-linear seismic inversion method enables a detailed delineation of a potentially porous carbonate interval due to interfaces that are derived as part of the inversion. The inversion is guided by the acoustic impedance log and uses a wavelet calculated at the well location. As the inversion does not use a prior model the result is not biased by the interpreter. The fully linear seismic inversion method enables an evaluation of the possible variation in acoustic impedance that can be derived from the seismic data. The inversion method utilizes a prior model defined by extrapolating the low frequency trend from the acoustic impedance log along interpreted horizons. Based on this model the best fitting mean acoustic impedance section resolved in the seismic section is found. Additionally the upper and lower confidence limits of acoustic impedance which can be derived from the seismic section, are defined.