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Er V.,University of Alberta | Er V.,Apex Engineering Inc. | Babadagli T.,University of Alberta | Babadagli T.,Sultan Qaboos University | Babadagli T.,University of Southern California
SPE Reservoir Evaluation and Engineering | Year: 2010

CO2 injection has been applied in naturally fractured reservoirs (NFRs) for the purpose of enhanced oil recovery (i.e., the Wey-burn and Midale fields, Canada; the Wasson and Slaughter fields, USA; and the Bati Raman field, Turkey). The matrix part of these types of reservoirs could potentially be a good storage medium as well. Understanding the matrix/fracture interaction during this process and the dynamics of the flow in this dual-porosity system requires visual analyses. We mimicked fully miscible CO2 injection in NFRs using 2D models with a single fracture and oil (solute)/hydrocarbon solvent pairs. The focus was on the visual pore-scale analysis of miscibility interaction, breakthrough of solvent through fracture, transfer between matrix and fracture, and the dynamics of miscible displacement inside the matrix. First, matrix/fracture interaction was studied intensively using 2D glass-bead models experimentally. The model was prepared using acrylic sheets and glass beads saturated with oil as a porous medium while a narrow gap of 1-mm size containing filter paper served as a fracture. The first contact miscible solvent (pentane) was injected into the fracture, and the flow distribution was monitored using an image-acquisition and -processing system. The produced solvent and solute were continuously analyzed for compositional study. The effects of several parameters, such as flow rate, viscosity ratio (oil/solvent), and gravity, were studied. Next, the process was modeled numerically using a commercial compositional simulator, and the saturation distribution in the matrix was matched to experimental data. The key parameters in the matching process were the effective diffusion coefficients and the longitudinal and the transverse dispersivities. The diffusion coefficients were specified for each fluid, and dispersivities were assigned into gridblocks separately for the fracture and the matrix. Copyright © 2010 Society of Petroleum Engineers.

In a method for enhancing the efficiency of separation of bitumen from oil sands ore, lipids, lipid by-products, and lipid derivatives are used as process additives for ore-water slurry-based bitumen extraction processes or in situ bitumen recovery processes. These additives act as surfactants reducing surface and interfacial tensions, thus promoting breakdown the oil sands ore structure and resultant liberation of bitumen from the ore. Lipid treatment does not deleteriously affect release water chemistry in bitumen recovery processes, and it does not appreciably affect the fuel value of recovered bitumen. Lipids which may be effectively used as additives include biodiesel, tall oil fatty acids, monoglycerides, vegetable oil, and soap water, and combinations thereof. Lipids may also be used as process additives to enhance the efficiency of clean-up of hydrocarbon-contaminated soils, in the production of bitumen-water or oil-water emulsions, and to enhance the transportability of emulsions such as in pipelines.

Apex Engineering Inc. | Date: 2014-01-18

In a process for destabilizing bitumen-water emulsions to facilitate bitumen recovery therefrom, bitumen-water interfacial tension is increased by reducing or eliminating the activity of functional groups acting as surfactants by treating the emulsions with one or more additives of ionic base to increase the hydrophobic characteristics of bitumen droplets in the emulsions and thus increase their attraction to each other and to gas bubbles. Additives effective for this purpose include salts of the Periodic Tables Group II earth alkali metals cations such as magnesium, calcium, strontium, and barium, and Group III metals cations such as aluminum. Mechanical agitation or injection of a gas stream into the destabilized bitumen-eater emulsion may be used to form bitumen-rich froth. The additives used for destabilization of the emulsions also promote flocculation of clay-size particles in the froth and improve the chemistry of the recovered water.

Use of additives to improve the efficiency of thermal heavy oil and bitumen recovery processes has been studied extensively over the decades. Two common types of additives used in thermal applications, mainly steam assisted recovery, are solvents and surfactants. Commercial use of solvents has setbacks due to their high costs and retrieval difficulties. Cost and stability of the surfactants under reservoir operating temperature and pressure are the major concerns. We propose the use of bio Diesel such as fatty acids methyl ester as a surfactant additive reducing heavy oil/bitumen-water interfacial tension in steam assisted recovery processes. Advantages of using bioDiesel as a surfactant additive are that bio Diesel is chemically stable under the operating pressure and temperature of the reservoir, it causes no harm on bitumen fuel quality and on release water chemistry and its use is economically feasible. We conducted a series of steam assisted bitumen recovery experiments to clarify the additional recovery potential and efficiency improvement capacity of bio Diesel. High pressure steam at 1.8 MPa pressure, 205°C was used in these tests at a 900 g/h feed rate. The porous media used was a normal grade oil sands ore obtained from a surface mine operation in Northern Alberta, Canada. Oil sands ore was packed in a basket and placed in a high pressure cell. Bitumen recovery experiments were performed by spraying canola oil fatty acid methyl ester on oil sands ore at a 2 g/kg-bitumen dosage. These tests show that bitumen recovery efficiency increases over 40%. In another series of tests, tall oil fatty acids methyl ester was injected into a high pressure steam line at a 8.3 g-bioDiesel/kg-steam dosage. Because of the solubility of bioDiesel in bitumen, the effect of bioDiesel on bitumen recovery could not be accurately concluded. Vapor pressure measurements performed on canola oil and tall oil derived bioDiesel samples suggest that saturation compositions of bioDiesel in steam at 1.8 MPa pressure and 205°C are at least one order of magnitude higher than the requested bioDiesel dosages. Further tests are planned by reducing bioDiesel dosages to about 0.5 to 1.0 g-bioDiesel/kilogram-steam and by monitoring the solubility of bioDiesel in bitumen. © 2012, IFP Energies nouvelles.

Yates T.J.,Apex Engineering Inc. | Sullivan-Green L.,San Jose State University
Practice Periodical on Structural Design and Construction | Year: 2013

This paper focuses on the analysis and design of foundations on clayey (elastic) soils in the San Francisco/San Pablo Bay area. Many of these soils have mild to moderate expansive properties that still allow the use of shallow T-footings (strip footings). Although suitable for strip footings, the clayey soils deform under structural loads, causing settlement. This deformation causes internal forces in the reinforced T-footing which need to be properly accounted for in design. Three local methods are examined and compared with respect to their assumptions, conservatism, and appropriateness of use. These methods are the spanability method, the bearing capacity method, and the FEM. Although the spanability and bearing capacity methods are deemed adequate by local building officials and design engineers, this paper recommends the use of a more accurate method for design and analysis such as FEM to properly account for structural loads within the T-footings. © 2013 American Society of Civil Engineers.

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