Browsing by Subject "Bitumen"

Now showing 1 - 9 of 9

Experimental studies on the use of chemical additives for steam-assisted gravity drainage
(2017-12-07) Li, Litan; Nguyen, Quoc P.; Balhoff, Matthew T
Steam-assisted gravity drainage (SAGD) is a mature technique for bitumen recovery from oil sand reservoirs; however, it is an energy intensive process that requires large amounts of steam to heat and mobilize the bitumen. The purpose of this work was to find ways to improve SAGD performance using chemical additives. Key mechanisms were identified, a suite of high-temperature additive characterization tests was developed, and promising additives were tested in porous media. Based on the results, experimenters concluded that oil-water interfacial tension reduction held the most potential for improved recovery. A preliminary field-scale study was attempted using numerical simulation, which showed that wettability alteration and oil-water interfacial tension reduction had a positive impact on SAGD performance.
Mixing of solvent and bitumen in steam-solvent co-injection under controlled thermodynamic conditions
(2021-09-27) Liu, Young (M.S. in engineering); Okuno, Ryosuke, 1974-
The most important aspect of solvent-aided steam-assisted gravity drainage (SA-SAGD) is the interplay between phase behavior and fluid flow near the edge of a steam chamber, which is caused by the mixing of solvent with bitumen. The mixing of solvent with bitumen (i.e., dispersion) results in dilution of the bitumen and improves the energy efficiency of SAGD. However, it is often difficult to analyze this through large-scale steam injection experiments because chamber-edge thermodynamic conditions in the experiments are transient. Moreover, research studies on dispersion, along with dispersion coefficient data, in SA-SAGD are scarce. This thesis presents a novel small-scale experimental method and a numerical model designed to study the bitumen gravity drainage with steam injection (SAGD) and solvent-steam co-injection (SA-SAGD) under controlled thermodynamic conditions, such as pressure, temperature, and composition. The dispersion coefficients for solvents with bitumen under gravity drainage with controlled boundary conditions are determined by calibrating a fine-scale numerical model with experimental data. The experiments use a 3-inch diameter by 15-inch length sand-pack placed in a 25-L cylindrical pressure vessel. The sand-pack is surrounded by a one-inch annular void space, into which the vapor phase is injected under controlled pressure, temperature, and composition. Both steam only and steam and solvent co-injection experiments are performed at a pressure of 3500 kPa. Oil production and temperature profiles inside and outside the sand-pack are recorded for all experiments. Post excavated samples from the sand-pack are analyzed. The results of the SAGD base case are history-matched using a numerical simulation model. The established parameters from the SAGD history match are then transferred to the SA-SAGD simulation model. The SA-SAGD experiments are history matched by fine-tuning the dispersion coefficient to better model the mixing between the solvent and bitumen. The dispersion coefficient for C₄ and C₈ in bitumen for SA-SAGD are determined to be 5.83×10⁻² m²/day and 5.64×10⁻² m²/day, respectively. The associated Péclet numbers for C₄ and C₈ dispersion coefficients are 60 and 309. The solved dispersion coefficients are analyzed and discussed. Finally, the criteria and guidelines are given for applying the determined dispersion coefficients in the field-scale simulation of SA-SAGD.
Novel solvent injection and conformance control technologies for fractured viscous oil reservoirs
(2013-05) Rankin, Kelli Margaret; Nguyen, Quoc P.
Fractured viscous oil resources hold great potential for continued oil production growth globally. However, many of these resources are not accessible with current commercial technologies using steam injection which limits operations to high temperatures. Several steam-solvent processes have been proposed to decrease steam usage, but they still require operating temperatures too high for many projects. There is a need for a low temperature injection strategy alternative for viscous oil production. This dissertation discusses scoping experimental work for a low temperature solvent injection strategy targeting fractured systems. The strategy combines three production mechanisms – gas-oil gravity drainage, liquid extraction, and film gravity drainage. During the initial heating period when the injected solvent is in the liquid phase, liquid extraction occurs. When the solvent is in the vapor phase, solvent-enhanced film gravity drainage occurs. A preliminary simulation of the experiments was developed to study the impact of parameter uncertainty on the model performance. Additional work on reducing uncertainty for key parameters controlling the two solvent production mechanisms will be necessary. In a natural fracture network, the solvent would not be injected uniformly throughout the reservoir. Preferential injection into the higher conductivity fracture areas would result in early breakthrough leaving unswept areas of high oil saturation. Conformance control would be necessary to divert subsequent solvent injection into the unswept zones. A variety of techniques, including polymer and silica gel treatments, have been designed to block flow through the swept zones, but all involve initiating gelation prior to injection. This dissertation also looks at a strategy that uses the salinity gradient between the injected silica nanoparticle dispersion and the in-situ formation water to trigger gelation. First, the equilibrium phase behavior of silica dispersions as a function of sodium chloride and nanoparticle concentration and temperature was determined. The dispersions exhibited three phases – a clear, stable dispersion; gel; and a viscous, unstable dispersion. The gelation time was found to decrease exponentially as a function of silica concentration, salinity, and temperature. During core flood tests under matrix and fracture injection, the in-situ formed gels were shown to provide sufficient conductivity reduction even at low nanoparticle concentration.
Optical characterization of asphalt binder microstructure
(2019-04-30) Ramm, Adam Steven; Downer, Michael Coffin; Bhasin, Amit; Marder, Michael; Sitz, Greg
This dissertation presents results of optical characterization of asphalt binder microstructure. We use noncontact optical microscopy methods to observe microstructure at the surface as well as in the bulk of asphalt binder samples. Normal incidence optical microscopy is used to image elongated, striped, surface microstructures (known as ’bees’ since they resemble bumble-bees) with comparable resolution to atomic force microscopy (AFM). Narrow band dark field optical microscopy is used to measure surface microstructure areal density and bulk microstructure volume density. Short wavelength illumination images surface microstructures, while longer wavelength near infrared (NIR) illumination penetrates into the bulk and images sub-surface microstructures. We subject the binder to temperature cycles and observe the resulting microstructure kinetics. We benchmark these optical measurements with rheometry measurements obtained from identical thermal cycles. We also use optical methods to observe surface ’bee’ microstructure variations due to interfacial tension modifications and compare these results to thin film mechanics theory
Optical second harmonic generation in bitumen films
(2012-12) Roberts, Aaron Joseph; Downer, Michael Coffin
The ability of asphalt binders (bitumen) in road surfaces to self-heal after cracking is important to developing a robust transportation system that can tolerate heavy traffic and varying weather conditions. In order to develop improved binders, there is a need for noninvasive, in-situ, interface-specific methods of monitoring the kinetics, physics and chemistry of self-healing bitumen interfaces. Here the feasibility of using optical second-harmonic generation (SHG) by focused femtosecond laser pulses to monitor bitumen surfaces is demonstrated. SHG signals are observed in transmission through a sample composed of bitumen spin-coated onto a borosilicate microscope coverslip. The SHG signals are absent from uncoated coverslips, demonstrating that they originate from the bitumen layer. Further tests demonstrate that the bitumen-air surface makes the dominant contribution to the SHG signal. The SHG signal is observed to decay on a time scale comparable to typical self-healing times because of sample heating by the incident laser irradiation. Methods to control this effect by translating the sample during data acquisition are developed. Although the present results were obtained with a single incident wavelength (800 nm), they demonstrate the feasibility of probing bitumen interfaces spectroscopically with tunable light sources in order to monitor bond-specific chemical kinetics.
Origins and evolution of instabilities in asphalt binder
(2023-01-02) Hajj, Ramez Muhammad; Bhasin, Amit; Juenger, Maria; Folliard, Kevin; Downer, Michael
Asphalt binders are complex viscoelastic materials that serve as the bonding agent for mineral aggregates in flexible pavement layers. One of the most important distresses exhibited in flexible pavements is their tendency to crack due to repeated loading. The current body of literature on asphalt binders has yet to establish experimentally how these cracks are born at a microscopic level, and a proper test method for evaluating a binder’s resistance to forming cracks. This dissertation proposes answers toward a solution to both of the above gaps. Eight asphalt binders were evaluated experimentally using a novel poker chip test that realistically mirrors the state of stress experienced by a binder in an asphalt mix. Based on these results, the interplay between stiffness, strength, and ductility of the binder was evaluated and used as a screening tool to for outlier binders. In addition, the cavitation surfaces and their relationship with strength was observed. Subsequently, dark field microscopy was used to observe the origination of the cavitation instability in the binder. Cavitation was observed to occur at the interface between inclusions in the bulk of the binder and the matrix itself. A theoretical framework for the reasons for this based on classical solutions in mechanics is proposed. Finally, X-ray computed tomography was used to obtain images of an asphalt mixture microstructure at two different scales. These images were meshed to form a finite element model, which was used to determine critical points in a mixture for cracking. The findings indicated high triaxiality could be appropriately modeled in the laboratory using the poker chip test at high aspect (diameter/thickness) ratio. This high aspect ratio creates an approximate confined stress state for testing, and also allows for nearly uniform stress distribution in the test specimen. This was validated using finite element analysis to confirm the poker chip test as suitable for laboratory testing of asphalt binders.
Production mechanism of diluent injection in heavy oil and bitumen
(2017-06-05) Nguyen, Duong Thai; Nguyen, Quoc P.
The invention of horizontal and hydraulic fractured have shaped the oil and gas industry in such a way that engineers could never imagine. Thanks to the new technology, tight formation productions help the United States comes tantalizingly close to energy independent. After four decades, the U.S lifted the ban on crude oil export increased the competition in the energy market. However, tight formations productions require high capital investment, and high water consumption but its production declines fast. Scientist have been actively seeking for alternative resources for future supply. Heavy oil and bitumen is one of interesting alternative, as the resource can be all over the world, but the largest reserves are concentrated in Americas: Venezuela, and in Canada’s Alberta Province. The production of heavy oil and bitumen is an extremely energy-intensive activity with the associated high environmental impact. Most common methods for heavy oil and bitumen production are surface mining or heat injection. The heat lost associated with steam injection is a big concern, sometimes it can be as high as 90%. To reduce heat loss, the use of solvent was employed. However, solvent processes with vertical wells could be much slower than the thermal process such as steam injection. Since the introduction of horizontal well and hydraulic fracture that helps increase the contact area between the solvent and oil, the investigation of solvent injection process has been widely revisited. Solvent or diluent injection without understanding asphaltene behavior can cause permeability and porosity reduction. In this study, I have investigated the mass transfer mechanisms in diluent processes with focus on understanding how these mechanisms govern asphaltene precipitation, flocculation and transportation.
A real options analysis and comparative cost assessment of nuclear and natural gas applications in the Athabasca oil sands
(2010-08) Harvey, Julia Blum, 1982-; Groat, Charles G.; Schneider, Erich; Jablonowski, Christopher
This report offers a comparative valuation of two bitumen production technologies, using real options analysis (ROA) techniques to incorporate strategic flexibility into the investment scenario. By integrating a probabilistic cost model into a real options framework, the value of an oil recovery facility is modeled to reflect the realistic alternatives available to decision-makers, where the course of the investment can be altered as new information becomes available. This approach represents a distinct advantage to traditional discounted cash flow (DCF) estimation, which is unable to capture operational adaptability, including the ability to expand, delay, or abandon a project. The analysis focuses on the energy inputs required for the recovery of heavy oil bitumen from Alberta, Canada, and examines both natural gas and nuclear steam plants as heat sources. The ACR-1000 reactor is highlighted as a substitute for conventional natural gas-fueled means of production, in light of the recent volatility of natural gas prices and the potential for emissions compliance charges. The methodology includes a levelized cost assessment per barrel of bitumen and estimation of cost ranges for each component. A mean-reversion stochastic price model was also derived for the both natural gas and oil price. By incorporating cost ranges into a ROA framework, the benefit of retaining project flexibility is included in its valuation. Formulated as a decision tree, built-in options include the initial selection to pursue nuclear or natural gas, site selection and licensing, the ability to switch heat source in the planning stage, and the final commitment to construct. Each decision is influenced by uncertainties, including the course of bitumen and natural gas price, as well as emissions policy. By structuring the investment scenario to include these options, the overall value of the project increases by over $150 million. The ability to switch technology type allows for an assessment of the viability of nuclear steam, which becomes economically favorable given high natural gas prices or high emissions taxes. Given an initial selection of natural gas SAGD, there is a 25% probability that a switch to nuclear steam will occur, as evolving financial conditions make nuclear the optimal technology.
Towards a better understanding of bitumen chemistry, microstructure, and rheology
(2018-11-27) Sakib, Nazmus; Bhasin, Amit; Baumgardner, Gaylon; Saleh, Navid; Juenger, Maria; Faxina, Adalberto
Bitumen is the residua of fractional distillation of crude oil. It generally consists of complex and a diverse variety of organic molecules and other heteroatoms. The nature and interactions between these molecules dictate the engineering properties of the bitumen. One of the attributes used to classify and examine these diverse constituent molecules is based on their relative polarities. Typically a bitumen is classified into four polarity based fractions, namely saturates, aromatics, resins and asphaltenes (SARA) using physical separation by precipitation and chromatography. Such separations require specialized equipment and expertise. In this study, two new fast and repeatable techniques of chromatography using disposable and inexpensive parts were developed. One of these methods was then used to fractionate a large set of bitumens in order to compare the constitution of the bitumens based on these fractions to their rheological, mechanical, and microstructural properties. Results show that parameters based on bitumen stiffness and tensile strength correlate well with these fractions. Similar relationship with more time dependent parameters was not conclusive. Microscopic observation of surface microstructures indicates similarity among bitumens from the same producer. There was also a good correlation between SARA parameters and surface microstructure for bitumens from the same producer. However, this relationship was unique for each producer and not global suggesting that other factors related to the crude source need to be considered as well