Solvent Steam Assisted Gravity Drainage Research Articles

Measurements and PR EoS Modeling of Thermophysical Properties at Vapor-Liquid Equilibrium Conditions for Natural Gas Condensate/Live Bitumen Mixtures.

In response to the need for less energy-intensive and greener bitumen recovery techniques, the use of multicomponent diluents through the expanding solvent steam-assisted gravity drainage (ES-SAGD) technique has garnered significant interest in recent years. In this work, we report new comprehensive measurements and Peng-Robinson equation of state (PR EoS) modeling of thermophysical properties (saturation pressure, density, viscosity, and K-values) of multicomponent mixtures of methane-bitumen-solvent. The multicomponent solvent is a natural gas condensate comprised of C3, i-C4, n-C4, i-C5, n-C5, C6, and C7+. Density, viscosity, solubility, and K-values of live bitumen (bitumen with dissolved methane) and various multicomponent mixtures are measured in the pressure range of 1-4 MPa and the temperature range of 313.41-459.10 K. A systematic approach is utilized to model the measured data. The experimental data show that the saturation pressure of the live bitumen can be controlled by selecting an appropriate solvent (condensate) composition. Condensate also has a significant effect on reducing the density and viscosity of the system. The results also show that the K-values of the components are almost independent of the composition of the solvent. The new comprehensive data set and the EoS model parameters reported in this work find applications in reservoir simulation as well as the design and optimization of the ES-SAGD process.

Influence of solvent injection temperature in steam-solvent assisted gravity drainage process for heavy oil reservoirs of Brazilian Northeast

The solvent–steam assisted gravity drainage is an oil recovery process that combines the advantages of thermal and miscible effects, and it has been successfully tested, especially in Canada, where many heavy oil reservoirs are located. This method uses two parallel horizontal wells drilled one above the other, the upper injects steam and solvent and the lower produces oil. This process has not been applied yet in Brazil, where there are heavy oil reservoirs, especially in northeast region. Based on this context, this research aimed to study the application of the ES-SAGD process in a semisynthetic reservoir, with characteristics similar to those found in the Brazilian Northeast, specifically to analyze the influence of the solvent injection scheme on ES-SAGD. Numerical simulations were performed using commercial software from CMG. It was analyzed several steam-solvent injection rates, using two injected temperatures for solvent, (at reservoir or at steam temperature´s), in order to minimize explosion risks, that can be due to high temperatures. Results showed that solvent injection temperature has great influence on oil recovery, it is better for oil production when it is inject hot solvent, because cold solvent generates a cooling of the steam. However, it is possible to injected cold solvent (at reservoir temperature), and increase oil production, changing some steam properties, avoiding explosions risks.

Bitumen Recovery Performance of SAGD and Butane- and Hexane-Aided SAGD in the Presence of Shale Barriers.

Oil and gas formations are commonly found to be heterogeneous, and one of the most common occurrences of reservoir heterogeneity is the presence of shale barriers. Shale barriers typically have very low permeability and high initial water saturation. Due to low permeability, these barriers obstruct the oil drainage path, specifically in thermal recovery methods such as steam-assisted gravity drainage (SAGD). In addition to flow assistance, they also lead to heat losses due to absorption by the high initial water saturation. Expanding solvent steam-assisted gravity drainage (ES-SAGD) is a hybrid technique comprising solvent co-injection along with steam. Solvent being in the vapor phase can potentially overcome the restricted path due to the presence of shale barriers. This paper presents a numerical simulation study on comparison between SAGD and ES-SAGD in the presence of shale barriers. SAGD and ES-SAGD with hexane and butane are numerically simulated for 240 lognormally generated shale realizations. First, both recovery processes are analyzed over the whole simulation period. Additionally, they have also been evaluated at multiple cumulative steam oil ratio cut-offs at 2, 2.5, 3, and 3.5. Transition points are defined and explained to cluster the shale density/fractions based on similar behaviors. It was shown that the oil that cannot be mobilized and produced by SAGD because shale barriers can be reached by the vaporized solvent through tortuous paths and recovered. Also, thermal losses are reduced because of lower steam chamber temperature. This led to efficient results for ES-SAGD over SAGD in heterogeneous formations.

Rich solvent - Steam assisted gravity drainage (RS-SAGD): An option for clean oil sands recovery processes

The impact of steam generation on Steam-Assisted Gravity Drainage (SAGD) process economics and environmental impacts have led to various modifications of SAGD including solvent co-injection with steam. One example is the Expanding Solvent Steam-Assisted Gravity Drainage (ES-SAGD) process where 1–5 vol% solvent is injected with the steam into the reservoir. The solvent travels with the steam to the edge of depletion chamber dissolving into the oil thereby mobilizing the oil more than would have been achieved with heating alone. This means lower steam-to-oil ratio and thus, greater thermal efficiency, lower emissions intensity, and water consumption intensity. However, processes where the majority of the fluid injected is steam are still overly emissive and expensive to operate. There is a need to develop carbon-neutral bitumen production processes. Rich Solvent-SAGD (RS-SAGD) aims at injecting mostly solvent into the reservoir with small amounts of steam to achieve radically lower emissions and water consumption intensities than that of SAGD. Here, a RS-SAGD process is investigated where the solvent content is >60 vol% by using detailed thermal-solvent reservoir simulation in an Athabasca oil sands reservoir. The results reveal that RS-SAGD yields higher oil rate than that of SAGD and the process has significantly higher energy efficiency, up to 96% lower emissions and water consumption intensities than that of SAGD. Given the performance of RS-SAGD processes, oil sands operators should consider such processes for future operations.

Data-Driven Models to Predict Hydrocarbon Production From Unconventional Reservoirs by Thermal Recovery

AbstractIn the numerical simulations of thermal recovery for unconventional resources, reservoir models involve complex multicomponent-multiphase flow in non-isothermal conditions, where spatial heterogeneity necessitates the huge number of discretized elements. Proxy modeling approaches have been applied to efficiently approximate solutions of reservoir simulations in such complex problems. In this study, we apply machine learning technologies to the thermal recovery of unconventional resources, for the efficient computation and prediction of hydrocarbon production. We develop data-driven models applying artificial neural network (ANN) to predict hydrocarbon productions under heterogeneous and unknown properties of unconventional reservoirs. We study two different thermal recovery methods—expanding solvent steam-assisted gravity drainage for bitumen and in-situ upgrading of oil shale. We obtain training datasets by running high-fidelity simulation models for these two problems. As training datasets of ANN models, diverse input and output data of phase and component productions are generated, by considering heterogeneity and uncertainty. In the bitumen reservoirs, diverse permeability anisotropies are considered as unknown properties. Similarly, in the oil shale reservoirs, diverse kerogen decomposition kinetics are considered. The performance of data-driven models is evaluated with respect to the position of the test dataset. When the test data is inside of the boundary of training datasets, the developed data-driven models based on ANN reliably predict the cumulative productions at the end of the recovery processes. However, when the test data is at the boundary of training datasets, physical insight plays a significant role to provide a reliable performance of data-driven models.

2-D physical model experimental study of ethyl acetate and steam co-injection for in-situ bitumen recovery

In this work, we evaluate ethyl acetate (EA) as a solvent for bitumen recovery using a 2-D sand-pack physical model for the first time. EA was considered for co-injection with steam due to the promising results obtained from our recent experimental phase behavior and reservoir simulation studies. Two experiments were conducted by co-injection of 10 and 20 vol% of EA with steam to evaluate expanding solvent steam assisted gravity drainage (ES-SAGD). An experiment was also conducted for the steam assisted gravity drainage (SAGD) as a reference case. The results showed that co-injection of EA increases the bitumen rate. Both ES-SAGD experiments showed a higher production rate compared to SAGD and the superiority of ES-SAGD. The results of 10 and 20 vol% EA co-injection revealed ~65% and ~75% bitumen recovery, respectively, compared to 50% in the case of the SAGD experiment. Co-injection of EA with steam also decreased the cumulative steam-oil-ratio (cSOR), which is desirable in bitumen recovery processes. ES-SAGD experiments reduced the cSOR by 1.5 to 2.5 units, which is 20 to 32% lower than SAGD. This reduction in cSOR results in significant energy savings and lower greenhouse gas emission intensity. The cumulative energy-oil-ratio was also measured, and the results showed that co-injection of EA decreases the energy-oil-ratio by 17–22% compared to SAGD. Moreover, it was observed that implementation of EA significantly reduces the water-oil emulsion stability, which is favorable in oil/water separation and treatments of the produced water.

Solvent-Based and Solvent-Assisted Recovery Processes: State of the Art

Summary Steam injection is a widely used oil-recovery method that has been commercially successful in many types of heavy-oil reservoirs, including the oil sands of Alberta, Canada. Steam is very effective in delivering heat that is the key to heavy-oil mobilization. In the distant past in California, and also recently in Alberta, solvents were/are being used as additives to steam for additional viscosity reduction. The current applications are in field projects involving steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS). The past and present projects using solvents alone or in combination with steam are reviewed and evaluated, including enhanced solvent SAGD (ES-SAGD) and liquid addition to steam for enhancing recovery (LASER). The use of solvent in other processes, such as effective solvent extraction incorporating electromagnetic heating (ESEIEH) and after cold-heavy-oil production with sand (CHOPS), are also reviewed. The theories behind the use of solvents with steam are outlined. These postulate additional heavy-oil/bitumen mobilization; oil mobilization ahead of the steam front; and oil mobilization by solvent dispersion caused by frontal instability. The plausibility of the different approaches and solvent availability and economics are also discussed.

Self-adaptive differential evolution with a novel adaptation technique and its application to optimize ES-SAGD recovery process

Differential evolution (DE) algorithm has shown good performance in many optimization problems. However, its control parameters greatly affect its performance and require many trials to determine the optimum values of control parameters for each specific optimization problem. In this paper, we present a self-adaptive DE with a new adaptation technique to improve the solution quality as well as increase the speed of convergence with a reduction in the computational cost. The proposed approach, called modified self-adaptive differential evolution (MSaDE), employs a new success-rate indicator of the strategies used to generate the trial vectors in conventional self-adaptive differential evolution (SaDE) algorithm. The proposed method has been tested on 22 benchmark problems and on the expanded solvent steam-assisted gravity drainage (ES-SAGD) recovery process. The results show that a significant speed-up is achieved in the exploitation and exploration capabilities of the self-adaptive DE algorithm.

A thermodynamic model to predict propane solubility in bitumen and heavy oil based on experimental fractionation and characterization

Propane has been suggested as suitable solvent for solvent-aided bitumen recovery methods such as Vapour Extraction (VAPEX), N-Solv (hot solvent injection), and Expanding Solvent-Steam Assisted Gravity Drainage (ES-SAGD). Characterization of bitumen and phase behaviour study of solvent/bitumen systems are the initial steps towards an optimized and successful solvent-aided bitumen recovery process. In this study, Athabasca bitumen is experimentally fractionated to four cuts using modified vacuum distillation and then each cut is characterized. The phase behaviour data including solubility, density, and viscosity of propane/bitumen cuts are measured in wide ranges of temperature and pressure. Using the measured solubility data of propane/bitumen cuts, the PR-EoS is tuned and a binary interaction parameter correlation between propane and bitumen components is developed. The bitumen is then characterized using the boiling point or carbon number distribution obtained by Simulated Distillation test (ASTM D7169). The generalized model is then implemented to calculate the propane solubility in two bitumen samples from different reservoirs (Athabasca and Cold Lake). Our proposed model in this paper, predicted the propane solubility in Athabasca bitumen sample with an average deviation of 1.8 mol.% without using any experimental data of propane/bitumen system or tuning parameter. The proposed model was also evaluated by predicting the propane solubility in Cold Lake bitumen. The propane solubility in Cold Lake bitumen was calculated with an average deviation of 3.0 mol.%, which shows the generality of the proposed model.

The effect of different solvents on the density of undersaturated athabasca bitumen: Application in VAPEX and ES-SAGD

ABSTRACTPredicting the density of bitumen after solvent injection is highly required in solvent-based recovery techniques like expanding solvent-steam assisted gravity drainage (ES-SAGD) and vapor extraction (VAPEX) in order to estimate the cumulative oil recovery by these processes. Using experimental procedures for this purpose is so expensive and time-consuming; therefore, it is crucial to propose a rapid and accurate model for predicting the effect of various solvents on the dilution of bitumen. In this study, an adaptive neuro-fuzzy interference system is introduced to estimate the effect of methane, ethane, propane, butane, carbon dioxide, and n-hexane on the density of undersaturated Athabasca bitumen in wide ranges of operating conditions. The obtained results were in an excellent agreement with experimental data with coefficients of determination (R2) of 0.99997 and 0.99948 for training and testing datasets, respectively. Statistical analyses illustrate the superiority of the proposed model in predicting the bitumen density at different conditions.

Quick Screening of Pareto-Optimal Operating Conditions for Expanding Solvent–Steam Assisted Gravity Drainage Using Hybrid Multi-Objective Optimization Approach

Solvent–steam mixture is a key factor in controlling the economic efficiency of the solvent-aided thermal injection process for producing bitumen in a highly viscous oil sands reservoir. This paper depicts a strategy to quickly provide trade-off operating conditions of the Expanding Solvent–Steam Assisted Gravity Drainage (ES-SAGD) process based on Pareto-optimality. Response surface models are employed to evaluate multiple ES-SAGD scenarios at low computational costs. The surrogate models play a role of objective-estimators in the multi-objective optimization that provides qualified ES-SAGD scenarios regarding bitumen recovery, steam–energy efficiency, and solvent-energy efficiency. The developed hybrid approach detects positive or negative correlations among the performance indicators of the ES-SAGD process. The derived Pareto-optimal operating conditions give flexibility in field development planning and thereby help decision makers determine the operating parameters of the ES-SAGD process based on their preferences.

Solubility and thermo-physical properties measurement of CO2- and N2-Athabasca bitumen systems

The production of heavy oil and bitumen is more complex and expensive than conventional oils. One of the main reasons is that heavy oils and bitumen have high viscosity and are usually immobile at the reservoir conditions. The viscosity of heavy oil or bitumen must be lowered in order to be recoverable by an oil recovery method such as solvent injection, steam-assisted gravity drainage (SAGD), and expanding solvent SAGD (ES-SAGD). In this study we report thermo-physical properties of CO2 and N2/bitumen mixtures. Solubility of non-condensable gaseous solvents, i.e. carbon dioxide and nitrogen, in Athabasca bitumen, as well as the liquid phase density and viscosity of solvent saturated bitumen are measured at temperatures up to 190°C and pressures up to 8MPa. Moreover, Peng-Robinson equation of state (PR-EoS) is applied to represent the experimental solubility which shows the absolute average relative deviation (AARD) of 4.3% and 7.6% for CO2 and N2, respectively. These findings will find many applications in the design and simulation of heavy oil and bitumen recovery processes.

Cracked Naphtha Coinjection in Steam-Assisted Gravity Drainage

Steam-assisted gravity drainage (SAGD) is a thermal in situ recovery method for heavy oil and oil sands that has been employed to exploit the vast petroleum deposits in the Athabasca region of northern Alberta that are not amenable to surface mining. Nevertheless, in spite of its success in recovering highly viscous bitumen, SAGD remains a costly technology that requires large energy input in the form of steam for each barrel of produced oil. This requires large quantities of water and natural gas, resulting in sizable greenhouse gas (GHG) emissions and extensive postproduction water treatment. There are ongoing efforts to make SAGD more energy-efficient and environmentally sustainable by reducing steam consumption while maintaining favorable oil production rates and ultimate oil recovery. Such efforts include the coinjection of steam and solvent in a process called expanding solvent SAGD (ES-SAGD) wherein bitumen that is essentially immobile at initial reservoir conditions is made mobile by heating and m...

Solubility of n-Butane in Athabasca Bitumen and Saturated Densities and Viscosities at Temperatures Up to 200°C

Summary The steam- and/or solvent-based recovery processes are efficient methods for recovery of heavy and extraheavy oils. The performance of these techniques depends on the amount of solvent dissolved in the oil and the variation of oil viscosity with temperature. Thus, full understanding of the quantitative effects of the solvent on heavy-oil viscosity and phase behavior is crucial for feasibility studies, design, and prediction of field-scale processes. Phase-behavior study of bitumen diluted with heavy hydrocarbon solvents, such as butane and pentane, has gained less attention in recent years. These solvents, as good candidates for recently developed recovery methods such as expanding solvent steam-assisted gravity drainage (ES-SAGD), could provide promising oil-production rates. Thus, the aim of this research is the development of an understanding of the phase behavior of n-butane/Athabasca-bitumen mixtures. It includes both experimental and modeling studies of solubilities and saturated liquid densities and viscosities over wide ranges of temperatures (up to 200 °C) and pressures (up to 8 MPa). Experimental results indicate that the dissolved n-butane in bitumen leads to a significant oil-viscosity reduction, and the effect is more pronounced at lower temperatures and/or higher pressures. The modeling results show that the measured solubilities are adequately represented by the Peng-Robinson equation of state (EOS) with an average absolute relative deviation (AARD) of 9.7%. The saturated liquid densities are also correlated with both the EOS and the effective liquid-density approach with 0.86 and 0.55% AARDs, respectively. The viscosity data are reasonably matched with Pedersen corresponding state.

Multicomponent Solvent Co-injection with Steam in Heavy and Extra-Heavy Oil Reservoirs

Expanding solvent steam assisted gravity drainage (ES-SAGD) is a hybrid steam–solvent oil recovery process that can be used to extract oil from heavy oil and bitumen reservoirs. It is a variation of the SAGD process in which only steam is used. In ES-SAGD, the mobilization of highly viscous oil is enhanced through a combination of heat and mass transfer processes, which results in significantly reduced volumes of water and natural gas needed to generate the injected steam, making ES-SAGD more energy efficient and environmentally sustainable relative to SAGD. Both SAGD and ES-SAGD use the same well configuration, and solvent co-injection in existing SAGD projects often requires limited facility modifications. This study investigates different aspects of ES-SAGD experimentally, based on typical Long Lake reservoir properties and operating conditions, using different concentrations of gas condensate. Furthermore, this study provides phase behavior insights to govern the selection of appropriate solvents for ...

Density and Viscosity of Athabasca Bitumen Samples at Temperatures Up to 200°C and Pressures Up to 10 MPa

Summary This paper presents the measurements of bitumen thermophysical properties (density and viscosity) over a wide range of temperatures (ambient to 200°C) and pressures (atmospheric to 14 MPa). The measurements have been conducted on three Athabasca bitumen samples taken from different locations. A new method was proposed to correlate the density data as a function of temperature and pressure, with a maximum absolute deviation of 1.7 kg/m3. The viscosity data were also correlated with two correlations available in literature considering the effect of pressure and temperature on viscosity of bitumen, with an average absolute relative deviation of 9.2%. The measured data and correlations are applicable for the prediction and optimization of oil recovery in the solvent- and thermal-based bitumen-recovery processes such as expanding- solvent steam assisted gravity drainage (ES-SAGD) and heated vapor extraction (VAPEX).

The Role of Resins, Asphaltenes, and Water in Water–Oil Emulsion Breaking with Microwave Heating

The stability of water-in-oil emulsions highly depends on the existence of polar components and their interactions within the emulsions. Asphaltenes, resins, and water are the main polar components of the emulsions. As the stability of the emulsions increases, emulsion breaking becomes more difficult and requires more energy and chemical input. With this study, we propose a significant reduction in energy and chemical use for efficient break up of water-in-oil emulsions through the application of microwave heating. To demonstrate this concept, we conduct experiments on different emulsions that originated from steam-assisted gravity drainage (SAGD) and expanding solvent SAGD (ES-SAGD) and investigate how the polar components initially present in the emulsions affect the microwave efficiency. Water, a polar molecule which is the main component in emulsions, was expected to allow the most efficient microwave absorption. However, our results show that asphaltenes and resins have greater role than the water co...

Modelling of Bitumen-and-Solvent-Mixture Viscosity Data Using Thermodynamic Perturbation Theory

Summary Viscosity is an important transport property for engineering design and simulation of bitumen production and transportation. During the production of bitumen with solvent injection, steam-assisted gravity drainage, or expanding solvent steam-assisted gravity drainage, the oil/solvent mixture encounters various temperature and pressure conditions. Therefore, a model is necessary to predict the viscosity of the mixture of bitumen and solvent in wide ranges of temperatures, pressures, and compositions (T-P-x). In this work, we propose a semitheoretical viscosity model based on the Arrhenius mixing rule and considering the effect of association between the molecules of the solvent and the bitumen. To achieve this purpose, thermodynamic perturbation theory (TPT) is used to calculate the fraction of bonding solvent molecules. We calculate the viscosity of the solvent in wide temperature and pressure ranges using the modified Enskog theory (MET). Results show an acceptable agreement between the predictions of this model and experimental viscosity data of bitumen saturated with different solvents (CH4, N2, CO2, and C2H6) at various T-P-x ranges. These experimental data cover the typical T-P-x ranges of oil-recovery methods.

Numerical Simulation Study of Field Scale SAGD and ES-SAGD Processes Investigating the Effect of Relative Permeabilities

Steam Assisted Gravity Drainage (SAGD) has been proved to be an effective method in producing from extra heavy oil or bitumen resources. The main recovery mechanism in this process is viscosity reduction by introducing heat into the reservoir. The Solvent Co-Injection processes (SCI) or Expanding Solvent SAGD (ES-SAGD) are alternative methods to the conventional SAGD. In these processes reduction in the oil viscosity is achieved by a combination of latent heat from steam and dissolution of solvents into bitumen. These alternative methods lower the steam requirements and associated costs with it, as well as the amount of carbon dioxide emission into the atmosphere caused by steam generation process.In this work some numerical simulations were conducted to examine the effect of relative permeability data on the performance of SAGD and ES-SAGD processes. Temperature dependant relative permeability data, that shows variation of end points with temperature, was tested against fixed relative permeabilities. Oil production was found to be strongly dependant on the end point relative permeability data. It is suggested to use temperature dependant relative permeabilities in numerical simulations. This must be considered as a matching criterion, when trying to history match field data.Solvent co-injection showed promising results both in terms of improved recovery factor and reduced steam oil ratio as an economical criterion. In addition, the high solvent recoveries of 97-100% in all solvent co-injection runs make the process even more economically interesting. Injecting only 2% on a molar basis of pentane, hexane or heptane as solvent, boosted the oil rates up.

A Review on Thermal Enhanced Heavy Oil Recovery from Fractured Carbonate Reservoirs

Heavy oil in Middle East fractured carbonate reservoirs account for 25-30% of the total oil in place in the region. Production of heavy oil from such reservoirs is thought to play an important role in the future of the ever-growing world\'s energy consumption in which Iran\'s recoverable heavy oil is more than 85 billion barrels. The offshore Ferdows field in Iran is reportedly on the order of 30 billion barrels of oil and holds perhaps the greatest promise to add significant future carbonate heavy oil production within the region. With depletion of conventional petroleum reserves and increase of hydrocarbon fuel demand, there is no doubt that there will be a tremendous demand on the development of heavy oil reservoirs in the coming decades. Despite its strategic importance, recovery of heavy crude from fractured carbonate reservoirs has found limited applications due to the complexity of such reservoirs. As most of the oil is stored in matrix due to its higher storage capacity than fracture network, reservoir development plans will aim at maximizing the matrix oil recovery. For reservoirs with high recovery factor, minimizing matrix residual oil saturation is a critical issue to extend the life of the reservoir. For reservoirs with low recovery factor, accelerating the production rate is more vital. For each of these reservoir types, different Enhanced Oil Recovery (EOR) methods should be considered and implemented accordingly. In this study, a comprehensive review is conducted to figure out the feasibility of heavy oil recovery from fractured carbonate reservoirs by use of Cyclic Steam Stimulation (CSS), Steam injection, In-Situ Combustion (ISC), Steam Assisted Gravity Drainage (SAGD), Vapor Extraction (VAPEX) and Expanding Solvent-Steam Assisted Gravity Drainage (ES-SAGD).