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Title Pore-scale controls of fluid flow laws and the cappillary trapping of CO₂
URL
Publication Date
Date Accessioned
Degree PhD
Discipline/Department Geological Sciences
Degree Level doctoral
University/Publisher University of Texas – Austin
Abstract A pore-scale understanding of fluid flow underpins the constitutive laws of continuum-scale porous media flow. Porous media flow laws are founded on simplified pore structure such as the classical capillary tube model or the pore-network model, both of which do not include diverging-converging pore geometry in the direction of flow. Therefore, modifications in the fluid flow field due to different pore geometries are not well understood. Thus this may translate to uncertainties on how flow in porous media is predicted in practical applications such as geological sequestration of carbon dioxide, petroleum recovery, and contaminant’s fate in aquifers. To fill this gap, we have investigated the role of a spectrum of diverging-converging pore geometries likely formed due to different grain shapes which may be due to a variety of processes such as weathering, sediment transport, and diagenesis. Our findings describe the physical mechanisms for the failure of Darcy’s Law and the characteristics of Forchheimer Law at increasing Reynolds Number flows. Through fundamental fluid physics, we determined the forces which are most responsible for the continuum-scale porous media hydraulic conductivity (K) or permeability. We show that the pore geometry and the eddies associated therein significantly modify the flow field and the boundary stresses. This has important implications on mineral precipitation-dissolution and microbial growth. We present a new non-dimensional geometric factor β, a metric for diverging-converging pore geometry, which can be used to predict K. This model for K based on β generalizes the original and now widely-used Kozeny (1927) model which was based on straight capillary tubes. Further, in order to better quantify the feasibility of geological CO2 sequestration, we have conducted laboratory fluid flow experiments at reservoir conditions to investigate the controls of media wettability and grain shapes on pore-scale capillary trapping. We present experimental evidence for the snap-off or formation of trapped CO2 ganglion. The total trapping potential is found to be 15% of porosity for a water-wet media. We show that at the pore-scale media wettability and viscous-fingering play a critical role in transport and trapping of CO2. Our investigations clearly show that that in single-phase flow pore geometry significantly modifies pore-scale stresses and impacts continuum-scale flow laws. In two-phase flows, while the media wettability plays a vital role, the mobility ratio of CO2 - brine system significantly controls the CO2 capillary trapping potential- a result which should be taken into consideration while managing CO2 sequestration projects.
Subjects/Keywords Non-Darcy law; Forchheimer law; Eddies; CO₂ trapping; CO₂ sequestration; Pore geometry; Fluid flow; Grain shape; Wettability
Contributors Cardenas, Meinhard Bayani, 1977- (advisor); Bennett, Philip C. (Philip Charles), 1959- (advisor)
Language en
Country of Publication us
Record ID handle:2152/22083
Repository texas
Date Retrieved
Date Indexed 2020-10-15
Grantor The University of Texas at Austin
Note [] text; [department] Geological Sciences;

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…grain geometry controls on the capillary trapping of supercritical carbon dioxide (s-CO₂ .75  4.1 Abstract ...................................................................................................75  4.2 Introduction…

trapping mechanisms: (a) snap-off at pore-throat, and (b) poredoublet model....................................................................................77  Figure 4.2: (a) The flow cell for CO₂ and brine flood…

…media. The controls of media wettability on the two-phase transport are well known from enhanced oil recovery operations; however, there exist no evidence of media wettability controls on CO₂ flow or its residual trapping. Residual trapping, also known…

…as capillary trapping (discussed further in Chapter 4), is projected to contribute to up to 90% [Qi et al., 2009] of permanently stored CO₂. A few initial studies on water-wet media have shown that CO₂ capillary trapping is a…

…2007; Krevor et al., 2012; Iglauer et al., 2012]. Furthurmore, no study to date has examined the effects of CO₂-wet media on its flow and capillary trapping. Similarly, pore geometry or pore structure is known to influence two-phase transport and…

trapping or involve numerical modeling only; no study clearly presents an experimental investigation of the pore-geometry controls on the transport and trapping of CO₂. 1.2 NOVEL QUESTIONS In this dissertation, I aim to investigate for the answers to the…

…scale hydraulic parameters? 5) How does the media wettability, i.e., water-wet vs. CO₂-wet control the transport and capillary trapping of CO₂? 6) How does the pore geometry, i.e., porous media formed of round grains vs. angular grains…

…influence the transport and capillary trapping of CO₂? 6 1.3 DISSERTATION ORGANIZATION To address the above listed question three different chapters are dedicated in this dissertation. Two of these main chapters are already published as two different…

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