Three-Phase Pore-Network Modelling for Mixed-Wet Carbonate Reservoirs

Abstract

Carbonate reservoirs have structural heterogeneities (triple porosity: pore-vug-fracture) and are mixed-to oil-wet. The interplay of structural and wettability heterogeneities impacts the sweep efficiency and oil recovery. The choice of an IOR or EOR process and the prediction of oil recovery requires a sound understanding of the fundamental controls on fluid flow in mixed-to oil-wet carbonate rocks and physically robust flow functions, i.e. relative permeability and capillary pressure functions. Obtaining these flow functions is a challenging task, especially when three fluid phases coexist. In this work we use pore-network modelling, a reliable and physically-based simulation tool, to predict three-phase flow functions. We have developed a new pore-scale network model for rocks with variable wettability. Unlike other models, this model comprises a novel thermodynamic criterion for formation and collapse of oil layers. The new model hence captures film/layer flow of oil adequately which impacts the oil relative permeability at low oil saturation and hence the accurate prediction of residual oil. Pore-networks extracted from pore-space reconstruction methods and CT images have been used as input for our simulations and the model comprises a constrained set of parameters that can be tuned to mimic the wetting state of a given reservoir. We have validated our model with available experimental data for a range of wettabilities. A sensitivity analysis has been carried out to investigate the dependency of relative permeabilities on layer collapse and film/layer flow under various wetting conditions. Additionally, WAG injection has been simulated with different lengths of so-called multi-displacement chains and different flood end-points. The flow functions generated by our model can be passed to the next scales (upscaling) to predict the oil recovery at the reservoir scale and we demonstrate this using a proof-of-concept study.

Construction of synthetic carbonate plugs: A review and some recent developments

“…This means that due to the wettability, if reservoir rock is oil-wet, higher amounts of oil can remain retained inside the reservoir rock, resulting in a negative economic situation [4]. For example, in the case of sandstone rocks, preferences to be water-wet [97,98] were found, and carbonate rocks to be oil-wet [6, 99,100] or with an intermediate wet behaviour [101,102] were found.…”

The impact of wettability and connectivity on relative permeability in carbonates: A pore network modeling analysis

“…Digital core analysis is a complement to this activity allowing predictions of multiphase properties to be made for different samples, displacement sequences and wettability to be made easily, once verified against good quality measurements on benchmark samples. The recent development of high‐resolution imaging capabilities has enabled different rock types to be studied that serve as the basis for predictions of flow and transport properties [ Arns et al , 2004; Knackstedt et al , 2006; Al‐dhahli et al , 2011; Blunt et al , 2012].…”

Uncertainty in WAG Injection Modelling using Empirical methods and Three-Phase Pore-Network Modeling with Rock Heterogeneity Effect

“…The study will use the network model that has already developed and validated [Øren, 2003] [23]. The realistic 3D pore-network extracted from the reconstructed pore space of Berea sandstone which will be used as inputs data to our model figure (1). The developed model as described in [2] will be used since it is a physically-based simulation tool.…”

“…Later the three-phase relative permeability has been obtained differently by each model based on these two phase data. Three network models have been used table (1). Three phase relative permeability obtained by network simulation have been used [35].…”