Print this pageAAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Reservoir Connectivity and Fluid Uncertainty Analysis Using Fast Geostatistical Seismic Inversion
(1) Earthworks Ltd, Salisbury, United Kingdom.
(2) BG Group plc, Reading, United Kingdom.
Stochastic seismic inversion (Haas and Dubrule, 1994; Francis, 2006) enables the uncertainty in seismic inversion to be explored. Additional information in the well logs is statistically exploited in accordance with the variogram model. Each stochastic seismic inversion realisation has a spatial constraint imposed by a variogram, is conditional to the well and stratigraphic horizon data and is conditional to the seismic data within the bandwidth of the wavelet. Using a frequency domain fast stochastic seismic inversion algorithm a sufficiently large number of stochastic realisations enables probability and 3D connectivity volumes corresponding to lithology or fluid indicators to be generated. Two applications of 3D Connectivity analysis of stochastic seismic inversion realisations are presented.
In the first example using post-stack seismic inversion 
impedance
realisations, the acoustic impedance is classified by sand and shale discriminators (Francis, 1997). The sand indicator is used to process each realisation using 3D connectivity to identify geobodies. By selecting realisations containing geobodies which are consistent with known connectivity criteria between wells, these realisations can be used as candidates for constraining geostatistical modelling.
In the second example, pre-stack seismic inversion results and a rock physics analysis are used to identify hydrocarbon fluid effects from the seismic response. Pre-stack inversion using Extended Elastic Impedance (Whitcombe et al, 2002) is used to generate a large number of joint stochastic impedance realisation pairs. Based on the rock physics analysis the EEI impedance
realisation pairs are rotated to obtain pairs of optimal fluid and lithology predictor realisations. The rotated realisation pairs are used to evaluate the probability of new well targets being partially depleted by existing production, to estimate sand volumetric uncertainty and to perform a risk analysis of a proposed horizontal well trajectory.