Integrated Study of a Fractured Middle East Reservoir with Stratiform Super-K Intervals – Part 2: Upscaling and Dual Media Simulation

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe paper describes the upscaling and reservoir simulation of a giant Middle East oilfield, whose geological modeling is described in a companion paper (1). The main objective of the study was the simulation of the irregular water advance observed in some parts of the field, as a consequence of peripheral water injection.Three scales of heterogeneity were identified in the characterization phase, namely the matrix, the stratiform Super-K intervals and the fractures. To accommodate the different hydraulic properties of each heterogeneity system, a dual-media approach (dual porosity and dual permeability) was used.The assignment of the effective properties to the simulation grids (matrix and fracture grids) was performed independently for the three heterogeneity systems. In particular, the geostatistical facies model was upscaled using algebraic methods, while the stratiform Super-K layers and fractures properties were explicitly reproduced at the simulation gridblock scale, through an original upscaling procedure.The history match was achieved in a short time, by a small variation of the fractal dimension of the fracture distribution and without resorting to any local modification.Simulation results showed that the fracture system was the controlling factor in terms of water advance and breakthrough, while the impact of the stratiform Super-K layers proved to be of second order.In a later stage, the model was utilized to run production forecasts under different exploitation scenarios.Conclusions of this study indicate that for such porous and fractured reservoirs with stratiform Super-K occurrences, a detailed characterization of all the heterogeneity systems, coupled with a dual-media formulation, are necessary requisites for accurate reservoir simulation and effective reservoir management.

Fractured Reservoir Simulation: a Challenging and Rewarding Issue

“…However, due to their size and their nonuniform distribution, they may closely influence the reservoir-scale flow behaviour, and be the origin of early injected fluid breakthroughs for instance. An accurate simulation of fluid flows along these large fractures with a dual-medium model is required, taking into account in particular the orientation and connectivity of those objects within and between cells through discrete fracture cell transmissivities (Cosentino et al, 2002). For the above reasons, sub-seismic faults or fracture swarms remain a weak point and a real source of uncertainties for fractured reservoir flow model.…”

“…The analysis of such reservoir engineering data is becoming common practice for fields with sparse fracture information (especially borehole image logs and flowmeters) from a few wells, but a more extensive set of long-term production data. Two recent examples concern Middle East fields (Cosentino et al, 2002;Ozkaya and Richard, 2006) where water injection resulted in earlier water breakthrough than expected (Fig. 2).…”

Integrated Reservoir Management: a Powerful Method to Add Value to Companies' Assets. a Modern View of the Eor Techniques

“…As such, the reservoir simulator must account for rock mechanical effects (especially to tackle fractured reservoirs), include a dual-media option [10,11] (for the same reason), be coupled to a surface model in order to allow a global optimization process, be designed to simulate compositional effects like with gas injection and handle chemical or thermal flooding. With regard to complex well compliance and modeling of heterogeneities, the simulator has to be implemented with unstructured gridding facilities.…”

Impact of Fractures on CO2Storage Monitoring: Keys for an Integrated Approach

“…The presence of sub-seismic fractures (hereafter named fractures for brevity) in several reservoirs is evidenced by much larger permeability derived from production data than expected from core data (matrix permeability) (Bourbiaux et al, 2005;Cosentino et al, 2001). Several previous studies dealt with the modelling of the influence of fractures on seismic anisotropy (e.g., Brown and Lawton, 1993;Fjaer et al, 1996;Rasolofosaon, 1998a;Ikelle and Gangi, 2000;Gajewski et al, 2003), but we want here to emphasize that a multidisciplinary approach is required in order to finely characterize the impact of fractures on CO 2 storage monitoring.…”