Experimental Investigation of the Interaction of Phase Behavior With Microscopic Heterogeneity in a CO2 Flood

Abstract

This paper reports results of an experimental investigation of the effects of microscopic heterogeneity on local displacement efficiency in a CO 2 flood. Flow-visualization experiments for first-contact miscible displacements are described and compared with effluent composition measurement for the same models. High-pressure flow-visualization experiments for multicontact miscible CO 2 floods are also described. The displacements were performed in two-dimensional (2D) etched glass models made from thin-sections of San Andres carbonate core from the Maljamar field. Techniques used in preparation of the models are described briefly.Observations of first-contact miscible displacements in heterogeneous models indicate that early breakthrough and a long transition zone occur when preferential flow paths exist in the pore structure. This behavior corresponds to a flowing fraction less than 1 in the Coats-Smith model. Because the 2D models contained no dead-end PV, the results presented indicate that a low flowing fraction can occur if flow velocities in different portions of the pore space differ significantly. Coats-Smith parameters obtained for models were comparable with values obtained in floods performed in reservoir samples.Visual observations of the CO 2 /crude-oil displacements indicate that there is an interaction between phase behavior and microscopic heterogeneity. Mixing of nearly pure CO 2 in the preferential flow path with oil in adjacent regions leads to a residual oil saturation (ROS) that forms in the preferential path after oil initially present has been displaced.

Investigation of the microscopic displacement mechanisms and macroscopic behavior of alkaline flooding at different wettability conditions in shaly glass micromodels

“…Numerous studies have been performed using glass micromodels. They have been used to study specific aspects related to flow in porous media such as wettability (Laroche et al, 1999;Grattoni and Dawe, 2003), capillary pressure (Smith et al, 2005), interfacial tension (Mackay et al, 1998), heterogeneity (Bahralolom et al, 1998), multiple contact miscibility (Campbell and Orr, 1985;Dastyari et al, 2005), water alternating gas injection (Sohrabi et al, 2004), solvent injection (Dehghan et al, 2010;Farzaneh et al, 2010), and gravity drainage (Chatzis et al, 1988;Bora et al, 1997;Mashayekhizadeh et al, 2011).…”

Visual Investigations on the Oil Recovery and Sequestration Potential of CO₂ in Naturally Fractured Oil Reservoirs

“…Presence of water can decrease the efficiency of miscible CO 2 displacements in water wet systems as the higher saturation of wetting phase decreases the flow fraction of nonwetting phase and consequently decreases the recovery of oil in water wet systems (4) . Interaction of phase behaviour with heterogeneities leads to residual oil saturations due to preferential flow paths (5) .…”

“…In order to observe the effects of 2-D flow, Campbell and Orr (4) suggested using glass etched micro-models and visualized CO 2 /Crude oil displacements. Bahralolom et al (2,5) also used micro-models similar to the one used previously 3 . The main difference of Bahralolom's model was that pore networks on the models were etched by tracing pore patterns from an enlarged photo of thin-sections.…”

Modeling of capacitance flow behavior in EOS compositional simulation

“…Gradual migration of oil from the bypassed region to the flowing region can cause the resulting composition profile to deviate from the one without the transverse mass flux (Brock and Orr, 1991;Pande and Orr, 1994a;1994b;Zhou et al, 1997). High residual oil saturations were observed in dominant flow paths due to the interaction of phase behavior with oil bypassing (Gardner and Ypma, 1984;Campbell and Orr, 1985;Bahralolom et al, 1988;Mohanty and Johnson, 1993). These results indicate the importance of considering the effects of oil bypassing on oil recovery.…”

“…It has been observed in various types of experiments and field applications of gas injection. Flow-visualization experiments (Stalkup, 1970;Chatzis et al, 1983;Campbell and Orr, 1985;Bahralolom et al, 1988;Stern, 1991) showed that microscopic oil bypassing was related to pore structures with bimodal or wide pore-size distributions. Shielding of oil by water films in pores can also hinder the contact between the bypassed oil and injection gas in the region with high water saturations (Shelton and Schneider, few inches can cause marked oil bypassing by gas (McGuire et al, 1995).…”