Study of the Effects of Wettability Changes on Three-Phase Flow in Porous Media Through Pore Network Modelling

Abstract

Abstract The increased reliance on CO2 sequestration and Enhanced Oil Recovery techniques such as tertiary gas injection or WAG for oil field development has necessitated an in depth analysis of three-phase flow in porous media for reservoir modelling and production enhancement techniques. Prediction of three-phase flow phenomena requires a sound understanding of the fundamental flow physics in water-wet, intermediate and oil-wet rocks in order to derive physically robust flow functions, namely relative permeability and capillary pressure curves. A new pore-network model for rocks with arbitrary wettability employing the thermodynamic oil formation and collapse criteria was developed and successfully validated by Al Dhahli et al. in January 2013. This model has been used in the current study to assess the influence of network extraction methodologies, wettability alteration after ageing and capillary effects on multiphase flow characteristics at pore level. Also, the study aims to understand the effects of capillary height functions on flow phenomena. These analogies are successfully illustrated for the Berea sandstone network models. The flow functions for pore-network analyses were subsequently imported to a reservoir model so as to carry out pore to reservoir scale integration. Flow function normalization and de-normalization were performed with respect to the flowing fluid saturations. This aided in better curve interpolations and fewer curve smoothening. Consequently, curve interpolations based on flowing saturations are suggested for three-phase pore- to reservoir scale integrations in future analyses. Pore network extraction and flow modelling has contributed to a paradigm shift in today's reservoir modelling approach. However, these applications are presently being limited to research level only and pore scale modelling is still in a relatively nascent stage. Near reservoir conditions such as intermediate wettability, variable flow functions and reservoir heterogeneity form a part of future work in this subject. Further study in this field can delineate dynamic properties of the reservoir, bringing the industry one step closer to effectively recovering immobile/trapped fluid from brown field reservoirs.