Production data integration in sand/shale reservoirs using sequential self-calibration and geomorphing: a comparison

摘要

The stochastic inversion of the spatial distribution of lithofacies from multiphase production data is a difficult problem. It is so even for the simplest case addressed here of a sand/shale distribution and under the assumption that reservoir properties are constant within each lithofacies. Two geostatistically-based inverse techniques, sequential self-calibration (SSC) and GeoMorphing (GM), are extended for such purpose and then compared using synthetic reference fields. The extension of both techniques is based on the one-to-one relationship existing between simulation. Both techniques attempt to modify the field of Gaussian deviates while maintaining fixed the truncation threshold field through an optimization procedure. Maintaining a fixed threshold field, which has bene previously computed on the basis of prior information of lithofacies proportion data, well dat,a and other static soft data, guarantees preservation of the initial geostatistical structure. COmparisons of the two techniques using 2-D and 3-D synthetic dat ashow that the SSC is very efficient in producing sand/shale realizaitons matching production data and reproducing the large scale patterns in the reference fields, although it has difficulty in reproducing small scale features. GM is a simpler algorithm than SSC, but it is computationally more intensive and has difficulty in matching complex production data. Better results could be obtained with a combination of the two techniques in which SSC is used to generate realizations identifying large scale features, then these realizations are used as input to GM for a final update to match small scale details.