Applications of Geostatistical Inversion to Solve Subsurface Challenges - A Case Study from NMC Area

Various challenging conditions encountered while mapping vertical extension and lateral continuity of medium to high porosity thin sands, e.g. significant overlap of elastic properties between reservoir and non-reservoir facies, presence of carbonaceous shales giving rise to pitfalls in interpretation etc. have been addressed using advanced geostatistical inversion workflow. Integrated and iterative workflows comprising well log data conditioning, seismic petrophysics, rock physics modelling and validation of predicted logs with seismic amplitude variations with offset (AVO) have been used to solve various issues encountered with well logs. Geostatistical inversion workflow comprising data preparation, geostatistical modelling and simulation, and unconstrained inversion, has been tailored to fit the purpose and the results validated at numerous blind wells. The frequency of occurrence of medium to high porosity sand bodies derived from many realisations of geostatistical inversion delineated several point bars consistent with the depositional setting of the area. Analysis of ranked volumes from geostatistical inversion shows that the actual sand thickness encountered in 7 out 11 blind wells fall within the P10-P90 range, thus quantifying the uncertainty associated with interpretation of the results.