Abstract
Faults are generally represented in conventional upscaled models as 2D planar surfaces with transmissibility multipliers used to represent single-phase fault properties. However, faults are structurally complex 3D zones in which both single-phase and two-phase fault rock properties can be significant. Ignoring this structural and petrophysical complexity within faults may impart considerable inaccuracy on the predictive performance of upscaled models. This study has developed a two-phase flow-based geometrical upscaling method capable of representing simultaneously the complex geometry and saturation-dependent two-phase flow properties of realistic fault zones. In this approach, high-resolution sector models are built of small portions of the fault zones and assigned appropriate single-phase and two-phase fault rock properties. Steady state two-phase flow simulations at different fractional flows of oil and water are used to determine the saturation dependent upscaled pseudo relative permeability functions which are incorporated into upscaled models. The method is applied to an example model containing two 3D fault zone components and tested by comparing the flow results of upscaled model with those of a high-resolution truth model. Results show that two-phase flow-based geometrical upscaling is a promising method for representing the effects of two-phase fault rock properties and complex 3D fault zone structure simultaneously.
Highlights
ObjectivesThe objective of the study is to upscale the fault zone in the truth model into a simpler representation as a single continuous surface with the same aggregated throw but none of the geometrical complexities: this is referred to as the upscaled model (Fig. 2b)
The overall objective of the current work is to create an upscaled model in which both single- and two-phase fault rock properties are represented within the simplified model geometry shown in Fig. 2b, and this upscaled model is the final product of the workflow summarised in Fig. 6 and explained in detail in the final section of the paper
This study has defined and tested a procedure for upscaling the geometry of three-dimensional fault zones and the single-phase and two-phase petrophysical properties of associated fault rocks, to the resolution at which faults are generally represented in full-field flow simulation models of conventional clastic reservoirs
Summary
The objective of the study is to upscale the fault zone in the truth model into a simpler representation as a single continuous surface with the same aggregated throw but none of the geometrical complexities: this is referred to as the upscaled model (Fig. 2b). The upscaled model (Fig. 2b) represents the fault as it would appear in a conventional full-field simulation model and the overall objective of the study is to upscale the flow paths present in the truth model for representation in this low-resolution upscaled model. The overall objective of the current work is to create an upscaled model in which both single- and two-phase fault rock properties are represented within the simplified model geometry shown, and this upscaled model is the final product of the workflow summarised in Fig. 6 and explained in detail in the final section of the paper. The objective of the current study is to describe the method and investigate its accuracy, and to do this requires comparisons between truth and upscaled models
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