Full Record

New Search | Similar Records

Author
Title Investigation of buoyant plumes in a quasi-2D domain : characterizing the influence of local capillary trapping and heterogeneity on sequestered CO₂ – : a bench scale experiment
URL
Publication Date
Date Accessioned
Degree MSin Engineering
Discipline/Department Petroleum Engineering
Degree Level masters
University/Publisher University of Texas – Austin
Abstract Leakage of stored bulk phase CO₂ is one risk for sequestration in deep saline aquifers. As the less dense CO₂ migrates upward within a storage formation or in layers above the formation, the security of its storage depends upon the trapping mechanisms that counteract the migration. The trapping mechanism motivating this research is local capillary trapping (LCT), which occurs during buoyancy-driven migration of bulk phase CO₂ within a saline aquifer with spatially heterogeneous petrophysical properties. When a CO₂ plume rising by buoyancy encounters a region where capillary entry pressure is locally larger than average, CO₂ accumulates beneath the region. One benefit of LCT, applied specifically to CO₂ sequestration and storage, is that saturation of stored CO₂ phase is larger than the saturation for other permanent trapping mechanisms. Another potential benefit is security: CO₂ that occupies local capillary traps remains there, even if the overlying formation that provides primary containment were to be compromised and allow leakage. Most work on LCT has involved numerical simulation (Saadatpoor 2010, Ganesh 2012); the research work presented here is a step toward understanding local capillary trapping at the bench scale. An apparatus and set of fluids are described which allow examining the extent of local capillary trapping, i.e. buoyant nonwetting phase immobilization beneath small-scale capillary barriers, which can be expected in typical heterogeneous storage formation. The bench scale environment analogous to CO₂ and brine in a saline aquifer is created in a quasi-two dimensional experimental apparatus with dimension of 63 cm by 63 cm by 5 cm, which allows for observation of plume migration with physically representative properties but at experimentally convenient ambient conditions. A surrogate fluid pair is developed to mimic the density, viscosity and interfacial tension relationship found at pressure and temperature typical of storage aquifers. Porous media heterogeneity, pressure boundary conditions, migration modes of uprising nonwetting phase, and presence of fracture/breach in the capillary barrier are studied in series of experiments for their influences on LCT. A variety of heterogeneous porous media made of a range of sizes of loosely packed silica beads are used to validate and test the persistence of local capillary trapping mechanism. By adjusting the boundary conditions (fluid levels in reservoirs attached to top and to bottom ports of the apparatus), the capillary pressure gradient across the domain was manipulated. Experiments were conducted with and without the presence of fracture/potential leakage pathway in the capillary seal. The trapped buoyant phase remained secure beneath the local capillary barriers, as long as the effective capillary pressure exerted by the trapped phase (proportional to column height of the phase) is smaller than the capillary entry pressure of the barrier. The local capillary trapping mechanism remained persistent even under forced imbibition, in which a…
Subjects/Keywords CO₂ geologic sequestration; Local capillary trapping
Contributors Bryant, Steven L. (advisor)
Language en
Country of Publication us
Record ID handle:2152/26451
Repository texas
Date Retrieved
Date Indexed 2019-09-12
Grantor The University of Texas at Austin
Note [] text; [department] Petroleum and Geosystems Engineering;

Sample Search Hits | Sample Images

…capillary trapping………………………….….………….…21 2.1.3 Local capillary trapping at bench scale………………………..…23 2.2 CO2 and brine properties…………………………………………………24 2.2.1 Wettability……………………………………………………..…24 2.2.2 Viscosity ratio…………………………………….………………24 2.2.3 Interfacial…

…bench scale…………… 30 2.4 Integrity of caprock for CO2 storage………………………………..……31 2.5 Persistence of local capillary trapping to CO2 storage safety……………33 viii Chapter 3 3.1 3.2 3.3 Experimental Set Up……………………………………………………. 34 Experiment concepts…

…limitations in the quantification process; refer to assumption (2) below……………………………………………………………………125 Table 5.1: Experimental plan for influence of bead size distribution on local capillary trapping …………………………………………………………..…… 162 x LIST OF…

…value tends to plateau beyond 20 MPa. (right) Interfacial tension between CO2 and brine tends to be independent on temperature at 20 MPa. (Neilson et al. 2012)……………………………27 (left) Evolution of the local capillary trapping

…volume with normalized critical capillary entry pressure for base case with different horizontal correlation lengths. (right) Evolution of the local capillary trapping volume with normalized critical capillary entry pressure for base case with…

…regions below boundaries with regions of sufficiently smaller beads. The circled sections appear to be where Local Capillary Trapping occurs. The configuration shown here from 34 hour is unchanged from the 3 hour observation. The circled sections…

…illustrate local capillary trapping of nonwetting phase beneath boundaries of regions of smaller beads above larger beads…………..….69 4 seconds after the apparatus is flipped. Channeling of nonwetting phase is evident in the 5 mm, 3 mm and 2 mm regions. The…

…settling; (b) Long time equilibrium states………………………..72 The circled sections illustrate local capillary trapping beneath boundaries where smaller beads lie above larger beads. Long lateral extent boundary provides a good trapping capability…

.