Experimental Investigation and Network Modelling Simulation of Free Fall Gravity Drainage in Single-Matrix and Fractured-Blocks Models

Abstract

<jats:title>Abstract</jats:title> <jats:p>Free Fall Gravity Drainage as an important recovery mechanism was investigated and analyzed experimentally and by numerical (network model) simulation for both single matrix and fractured blocks models. The results of free fall gravity drainage of these two models were compared to each other to determine whether or not the network of fractures intensify the free fall gravity drainage recovery of matrix blocks. For the experimental study, a set of glass micromodels with real pattern of porous media was constructed in two main forms of single matrix model (as a 2D simulator of conventional reservoirs) and fractured blocks model (as a 2D simulator of fractured reservoirs) in laboratory.</jats:p> <jats:p>Also, two numerical network model simulators were programmed based on pore scale displacement mechanisms (drainage, imbibition and flow through films) to study and compare the behavior of free fall gravity drainage process in two models. The simulator takes into account the dominant displacement mechanisms observed in free fall gravity drainage glass micromodel experiments of both single matrix and fractured blocks models. Free fall gravity drainage experimental results of glass micromodel were used to validate the network model simulator. The mixed-wet wettability of glass micromodels was applied in network model simulator which allows oil to flow through wetting films in oil-wet regions and through spreading films on water in water-wet regions.</jats:p> <jats:p>Method of Image-Analysis was used to generate pore and throat size distribution functions of glass micromodels. The simulators were used to study and interpret the effects of different parameters on free fall gravity drainage results. For this purpose, numerous sensitivity analysis scenarios were tested (run) by numerical simulators to evaluate the effect of different parameters (pore and throat size, fracture aperture, oil density, oil viscosity, gas -oil interfacial tension (sgo) and coordination number (Z)) on results of free fall gravity drainage process. Also, relative permeability and capillary pressure curves of both single matrix and fractured blocks models were generated by numerical network model simulator and are compared to each other.</jats:p>