Rheological Transition during Foam Flow in Porous Media

Abstract

The flow of nitrogen foam in Bentheimer sandstone cores previously saturated with a surfactant solution has been investigated experimentally. The displacement process was visualized with the aid of a computed tomography (CT) scanner. CT data were analyzed to obtain water saturation profiles at different times. Pressure drops measured over core segments were recorded to determine foam mobility. It was found that foam undergoes a sharp transition from a weak to a strong state at a critical gas saturation of S gc = 0.75 ± 0.02. This effect was interpreted successfully by the rise of foam yield stress as gas saturation exceeds the S gc. It is suggested that confined jamming is the most likely mechanism responsible for the mobility transition.

Effect of Surfactant Partitioning on Mobility Control During CO2 Flooding

“…5a and 5b show the sectional pressure drops and corresponding water saturation, respectively, during the simultaneous injection of CO 2 and the CD 1045 solution. The pressure drop near the inlet (Section 1) was much lower than that in subsequent sections (Sections 2 and 3), which has been well-known as the "inlet effect" (Kovscek and Radke 1993;Nguyen et al 2003;Simjoo et al 2012). Strong foam started to propagate into Section 2 after almost 2 injected PV and then Section 3 after 5 PV.…”

The flow of a foam in a two‐dimensional porous medium

“…While much is already known qualitatively on the mechanisms of foam displacement in porous media, and many existing macroscopic models [e.g., Kovscek and Radke , ; Kovscek et al ., ; Fergui et al ., ; Kornev et al ., ; Alvarez et al ., ; Kam et al ., ; Dholkawala et al ., ] address the generation and macroscopic displacement of foams in porous media, experimental studies usually involve the use of core flooding units [ Fergui et al ., ; Apaydin and Kovscek , ; Pang , ] from which it is difficult to obtain detailed information on the local foam structure: only global quantities can be measured, and only qualitative information on local displacement dynamics is inferred. In recent years, experiments using X‐ray microtomography [ Apaydin and Kovscek , ; Zitha et al ., ; Nguyen et al ., ; Du et al ., ; Simjoo et al ., ] or γ ray attenuation [ Fergui et al ., ] have enabled limited visualization of foam flow, revealing regions of preferential occupation of the medium by the foam and providing spatially resolved measurement of liquid fractions, also under conditions of oil sweep [ Simjoo et al ., ]. Experiments based on micromodels consisting of pore networks [ Jeong et al ., ; Chen et al ., ; Ma et al ., ; Jeong and Corapcioglu , ], on the other hand, have mainly been used to investigate oil or NAPL sweep, and have not allowed precise bubble‐scale observation of the foam kinematics, or only on a small subpart of the system [ Jeong and Corapcioglu , ], for example, in order to assess the role of capillary snap‐off on foam generation [ Kovscek et al ., ].…”

Capillary-Driven Transport of Dissolved Salt to the Drying Zone During $$\hbox {CO}_{2}$$ CO 2 Injection in Homogeneous and Layered Porous Media

“…Four slices were taken near the center of the core, each consisting of 512 × 512 pixels with the pixel size of 0.3 × 0.3 mm. The noise for CT images typically ranges from 3 to 20 Hounsfield Units (HU), corresponding to an accuracy of ±2 % (Simjoo et al 2012). CT scans produce images consisting of voxels with a Hounsfield Unit (HU) according to the average saturation inside the voxel, with a higher HU corresponding to a higher density.…”

“…Therefore, in the CT images, brine and solid salt were treated as a single phase. The files were imported into and processed in MATLAB to calculate brine saturations at different time steps (Akin and Kovscek 2003;Simjoo et al 2012). When imported into MATLAB for processing, the values are stored as HU+1024 in order to do calculations.…”