A Methodological Analysis of the Mechanisms Associated With Steam/Solvent Coinjection Processes Using Dynamic Gridding

Summary Hybrid steam-solvent processes have gained importance as a thermal-recovery process for heavy oils in recent years. Numerous pilot projects during the last decade indicate the increasing interest in this technology. The steam/solvent coinjection process aims to accelerate oil production, increase ultimate oil recovery, reduce energy and water-disposal requirements, and diminish the volume of emitted greenhouse gases compared with the steam-assisted-gravity-drainage (SAGD) process. Among the identified physical mechanisms that play a role during the hybrid steam/solvent processes are the heat-transfer phenomena, the gravity drainage and viscous flow, the solvent mass transfer, and the mass diffusion/dispersion phenomena. The major consequence of this complex interplay is the improvement of oil-phase mobility that is controlled by the reduction in the oil-phase viscosity at the edge of the steam chamber. It follows that a detailed representation of this narrow zone is necessary to capture the involved physical phenomena. In this work, a study of sensitivity to grid size was carried out to define the appropriate grid necessary to represent the near-edge zone of the steam/solvent chamber. Our results for the steam/solvent coinjection process in a homogeneous synthetic reservoir indicate that a decimetric scale is required to represent with a good precision the heat and mass-transfer processes taking place at the edge of the steam chamber. In addition, we present some numerical results of the adaptive dynamic gridding application. Comparison was performed between the SAGD process and steam/solvent coinjection after the characterization and analysis of the mechanisms that govern oil production under typical Athabasca oil-sand conditions. Finally, in the framework of the proposed numerical methodology, the effect of solvent type and injection conditions on the oil-recovery efficiency is quantitatively illustrated. Published data for similar applications are also discussed. It is expected that this work will provide some insight for the simulation community about methodological aspects to be taken into account when hybrid steam/solvent processes would be modeled.

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Steam-Assisted Gravity-Drainage Performance With Temperature-Dependent Properties—A Semianalytical Approach

SPE Journal ◽

10.2118/175036-pa ◽

2016 ◽

Vol 22 (03) ◽

pp. 902-911 ◽

Cited By ~ 6

Author(s):

M.. Heidari ◽

S. H. Hejazi ◽

S. M. Farouq Ali

Keyword(s):

Oil Sands ◽

Oil Production ◽

Thermal Recovery ◽

Effect Of Temperature ◽

Gravity Drainage ◽

Temperature Dependent ◽

Rock Density ◽

Steam Chamber ◽

Steam Assisted Gravity Drainage ◽

Temperature Dependent Properties

Summary Steam-assisted gravity drainage (SAGD) is one of the successful in-situ thermal-recovery methods for oil-sands production. In this paper, we provide a simple semianalytical model that can accurately analyze an SAGD project with variable properties. In particular, we investigate the effect of temperature-dependent properties such as thermal conductivity, heat capacity, and rock density on SAGD performance. The proposed model sequentially solves the transient nonlinear heat-transfer equation coupled with the continuity equation with Kirchhoff's transformation and the heat integral method (HIM). A criterion for timestep selection is defined on the basis of the Courant and Péclet numbers to guarantee the stability of the sequential technique. The results illustrate that the temperature-dependent physical properties affect temperature distributions ahead of steam chamber which consequently have a significant impact on the cumulative oil production and oil-production rate. Moreover, the results show that the temperature profile ahead of the steam chamber changes with time and space, and a 2D transient assumption for SAGD modeling is necessary. The semianalytical model runs in a small fraction of numerical-simulator runtime, yet it provides reasonable results. Thus, it has the potential to be used as a tool for quick SAGD evaluations.

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Numerical Simulation of Thermal Solvent Replacing Steam under Steam Assisted Gravity Drainage SAGD Process

10.4043/133453-ms ◽

2010 ◽

Author(s):

Weiqiang Li ◽

Daulat D. Mamora

Keyword(s):

High Temperature ◽

Oil Recovery ◽

Oil Sands ◽

Steam Injection ◽

Thermal Recovery ◽

Production Performance ◽

Gravity Drainage ◽

Steam Assisted Gravity Drainage ◽

Recovery Technique ◽

Simulation Results

Abstract Steam Assisted Gravity Drainage (SAGD) is one successful thermal recovery technique applied in the Athabasca oil sands in Canada to produce the very viscous bitumen. Water for SAGD is limited in supply and expensive to treat and to generate steam. Consequently, we conducted a study into injecting high-temperature solvent instead of steam to recover Athabasca oil. In this study, hexane (C6) coinjection at condensing condition is simulated using CMG STARS to analyze the drainage mechanism inside the vapor-solvent chamber. The production performance is compared with an equivalent steam injection case based on the same Athabasca reservoir condition. Simulation results show that C6 is vaporized and transported into the vapor-solvent chamber. At the condensing condition, high temperature C6 reduces the viscosity of the bitumen more efficiently than steam and can displace out all the original oil. The oil production rate with C6 injection is about 1.5 to 2 times that of steam injection with oil recovery factor of about 100% oil initially-in-place. Most of the injected C6 can be recycled from the reservoir and from the produced oil, thus significantly reduce the solvent cost. Results of our study indicate that high-temperature solvent injection appears feasible although further technical and economic evaluation of the process is required.

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A steam rising model of steam-assisted gravity drainage production for heavy oil reservoirs

Energy Exploration & Exploitation ◽

10.1177/0144598719897178 ◽

2019 ◽

Vol 38 (4) ◽

pp. 801-818

Author(s):

Ren-Shi Nie ◽

Yi-Min Wang ◽

Yi-Li Kang ◽

Yong-Lu Jia

Keyword(s):

Production Rate ◽

Horizontal Well ◽

Oil Production ◽

Steam Injection ◽

Injection Rate ◽

Gravity Drainage ◽

Model Parameters ◽

Steam Quality ◽

Steam Chamber ◽

Steam Assisted Gravity Drainage

The steam chamber rising process is an essential feature of steam-assisted gravity drainage. The development of a steam chamber and its production capabilities have been the focus of various studies. In this paper, a new analytical model is proposed that mimics the steam chamber development and predicts the oil production rate during the steam chamber rising stage. The steam chamber was assumed to have a circular geometry relative to a plane. The model includes determining the relation between the steam chamber development and the production capability. The daily oil production, steam oil ratio, and rising height of the steam chamber curves influenced by different model parameters were drawn. In addition, the curve sensitivities to different model parameters were thoroughly considered. The findings are as follows: The daily oil production increases with the steam injection rate, the steam quality, and the degree of utilization of a horizontal well. In addition, the steam oil ratio decreases with the steam quality and the degree of utilization of a horizontal well. Finally, the rising height of the steam chamber increases with the steam injection rate and steam quality, but decreases with the horizontal well length. The steam chamber rising rate, the location of the steam chamber interface, the rising time, and the daily oil production at a certain steam injection rate were also predicted. An example application showed that the proposed model is able to predict the oil production rate and describe the steam chamber development during the steam chamber rising stage.

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Approximate Physics-Discrete Simulation of the Steam-Chamber Evolution in Steam-Assisted Gravity Drainage

SPE Journal ◽

10.2118/194016-pa ◽

2018 ◽

Vol 24 (02) ◽

pp. 477-491 ◽

Cited By ~ 1

Author(s):

Enrique Gallardo ◽

Clayton V. Deutsch

Keyword(s):

Oil Sands ◽

Recovery Process ◽

Thermal Recovery ◽

Porous Media Flow ◽

Gravity Drainage ◽

Discrete Simulation ◽

Flow Equations ◽

Integrity Assessment ◽

Steam Chamber ◽

Steam Assisted Gravity Drainage

Summary Steam-assisted gravity drainage (SAGD) is a thermal-recovery process to produce bitumen from oil sands. In this technology, steam injected in the reservoir creates a constantly evolving steam chamber while heated bitumen drains to a production well. Understanding the geometry and the rate of growth of the steam chamber is necessary to manage an economically successful SAGD project. This work introduces an approximate physics-discrete simulator (APDS) to model the steam-chamber evolution. The algorithm is formulated and implemented using graph theory, simplified porous-media flow equations, heat-transfer concepts, and ideas from discrete simulation. The APDS predicts the steam-chamber evolution in heterogeneous reservoirs and is computationally efficient enough to be applied over multiple geostatistical realizations to support decisions in the presence of geological uncertainty. The APDS is expected to be useful for selecting well-pair locations and operational strategies, 4D-seismic integration in SAGD-reservoir characterization, and caprock-integrity assessment.

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Understanding the Thermo-Hydromechanical Pressurization in Two-Phase (Steam/Water) Flow and Its Application in Low-Permeability Caprock Formations in Steam-Assisted-Gravity-Drainage Projects

SPE Journal ◽

10.2118/165544-pa ◽

2014 ◽

Vol 19 (06) ◽

pp. 1126-1150 ◽

Cited By ~ 1

Author(s):

Sahar Ghannadi ◽

Mazda Irani ◽

Rick Chalaturnyk

Keyword(s):

Pore Pressure ◽

Shear Failure ◽

Thermal Recovery ◽

Subcritical State ◽

Gravity Drainage ◽

Low Permeability ◽

Steam Chamber ◽

Steam Assisted Gravity Drainage ◽

Caprock Integrity ◽

Casing Failure

Summary Steam-assisted gravity drainage (SAGD) is one successful thermal-recovery technique applied in Alberta oil-sand reservoirs. When considering in-situ production from bitumen reservoirs, one must reduce viscosity for the bitumen to flow toward the production well. Steam injection is currently the most promising thermal-recovery method. Although steamflooding has proved to be a commercially viable way to extract bitumen from bitumen reservoirs, caprock integrity and the risk of losing steam containment can be challenging operational problems. Because permeability is low in Albertan thermal-project caprock formations, heating greatly increases the pressure on any water trapped in pores as a result of water thermal expansion. This water also sees a great increase in volume as it flashes to steam, causing a large effective-stress reduction. After this condition is established, pore-pressure increases can lead to caprock shear failure or tensile fracturing, and to subsequent caprock-integrity failure or potential casing failure. It is typically believed that low-permeability caprocks impede the transmission of pore pressure from reservoirs, making them more resistant to shear failure (Collins 2005, 2007). In considering the “thermo-hydromechanical pressurization” physics, low-permeability caprocks are not always more resistant. As the steam chamber rises into the caprock, the heated pore fluids may flash to steam. Consequently, there is a vapor region between the steam-chamber interface penetrated into the caprock and the water region within the caprock which is still at a subcritical state. This study develops equations for fluid-mass and thermal-energy conservation, evaluating the thermo-hydromechanical pressurization in low-permeability caprocks and the flow of steam and water after steam starts to be injected as part of the SAGD process. Calculations are made for both short-term and long-term responses, and evaluated thermal pressurization is compared for caprocks with different stiffness states and with different permeabilities. One can conclude that the stiffer and less permeable the caprock, the greater the thermo-hydromechanical pressurization; and that the application of SAGD can lead to high pore pressure and potentially to caprock shear, and to subsequent steam release to the surface or potential casing failure.

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Feasibility of electromagnetic methods to detect and image steam-assisted gravity drainage steam chambers

Geophysics ◽

10.1190/geo2015-0451.1 ◽

2016 ◽

Vol 81 (4) ◽

pp. E227-E241 ◽

Cited By ~ 3

Author(s):

Sarah G. R. Devriese ◽

Douglas W. Oldenburg

Keyword(s):

Oil Recovery ◽

Oil Sands ◽

Vertical Component ◽

Design Procedure ◽

Production Costs ◽

Three Dimensions ◽

Gravity Drainage ◽

Steam Chamber ◽

Steam Assisted Gravity Drainage ◽

Mcmurray Formation

We have investigated the use of electric and electromagnetic (EM) methods to monitor the growth of steam-assisted gravity drainage (SAGD) steam chambers. SAGD has proven to be a successful method for extracting bitumen from the Athabasca oil sands in Alberta, Canada. However, complexity and heterogeneity within the reservoir could impede steam chamber growth, thereby limiting oil recovery and increase production costs. Using seismic data collected over an existing SAGD project, we have generated a synthetic steam chamber and modeled it as a conductive body within the bitumen-rich McMurray Formation. Simulated data from standard crosswell electrical surveys, when inverted in three dimensions, show existence of the chamber but lack the resolution necessary to determine the shape and size. By expanding to EM surveys, our ability to recover and resolve the steam chamber is significantly enhanced. We use a simplified survey design procedure to design a variety of field surveys that include surface and borehole transmitters operating in the frequency or time domain. Each survey is inverted in three dimensions, and the results are compared. Importantly, despite the shielding effects of the highly conductive cap rock over the McMurray Formation, we have determined that it is possible to electromagnetically excite the steam chamber using a large-loop surface transmitter. This motivates a synthetic example, constructed using the geology and resistivity logging data of a future SAGD site, where we simulate data from single and multiple surface loop transmitters. We have found that even when measurements are restricted to the vertical component of the electric field in standard observation wells, if multiple transmitters are used, the inversion recovers three steam chambers and discerns an area of limited steam growth that results from a blockage in the reservoir. The effectiveness of the survey shows that this EM methodology is worthy of future investigation and field deployment.

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Dimethyl Ether as a Novel Solvent for Bitumen Recovery: Mechanisms of Improved Mass Transfer and Energy Efficiency

SPE Journal ◽

10.2118/208615-pa ◽

2021 ◽

pp. 1-20

Author(s):

Min Yang ◽

Maojie Chai ◽

Rundong Qi ◽

Zhangxin Chen ◽

Linyang Zhang ◽

...

Keyword(s):

Mass Transfer ◽

Energy Efficiency ◽

Energy Consumption ◽

Dimethyl Ether ◽

Oil Production ◽

Recovery Process ◽

Thermal Recovery ◽

Production Performance ◽

Reservoir Rock ◽

Bitumen Recovery

Summary A solvent-based thermal recovery process has the advantages of low capital expenditure, less energy consumption, and less greenhouse gas emission. Dimethyl ether (DME), as a renewable solvent, has been considered as a novel additive in the thermal bitumen recovery process. Being soluble in both water and oil phases, DME has the potential to enhance mass transfer and improve oil production. In this work, a phase behavior model of the DME-bitumen-water system is first developed considering DME partitioning between oil and water. A field-scale numerical simulation model with fine gridblocks is developed to investigate the heat and mass transfer mechanisms between DME and bitumen in the interface of a DME vapor chamber. The numerical model is validated with physical experiment results. The close agreement between measured and simulated production profiles indicates that the mechanisms are adequately captured. Meanwhile, various simulation scenarios are performed to evaluate the production performance and the energy efficiency, which is defined as the energy/oil ratio. It is found that the oil production rate in DME injection is 15% higher than that in butane injection at the early stage of production. The solvent penetration depth in DME injection is larger than that in butane injection. This is attributed to the enhanced mass transfer between DME and bitumen caused by the high diffusion of DME in the water phase and preferential partitioning of DME into the oil phase. Furthermore, energy consumption in the warm DME injection process is 48% less than that in warm butane injection and 75% less than that in steam-assisted gravity drainage (SAGD). This is because DME injection can be operated at a lower-temperature condition, leading to less energy transferred to heat reservoir rock/fluids and less heat loss to over/underburden. Therefore, DME is proved to be a technically promising and environmentally friendly solvent to enhance bitumen recovery. The DME-based thermal recovery technique exhibits superior advantages in unlocking poor-quality reservoirs, especially in high water saturation reservoirs and thin reservoirs.

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Understanding Reservoir Architectures and Steam-Chamber Growth at Christina Lake, Alberta, by Using 4D Seismic and Crosswell Seismic Imaging

SPE Reservoir Evaluation & Engineering ◽

10.2118/97808-pa ◽

2007 ◽

Vol 10 (05) ◽

pp. 446-452 ◽

Cited By ~ 32

Author(s):

Weimin Zhang ◽

Sung Youn ◽

Quang T. Doan

Keyword(s):

Oil Recovery ◽

Seismic Data ◽

Lateral Spread ◽

Test Facility ◽

Gravity Drainage ◽

Baseline Survey ◽

Reservoir Heterogeneity ◽

Fort Mcmurray ◽

Steam Chamber ◽

Reservoir Architecture

Summary EnCana Corporation's Christina Lake Thermal Pilot Project located 170 km south of Fort McMurray, Alberta, Canada, uses steam-assisted gravity drainage (SAGD) technology to recover bitumen from the Lower Cretaceous McMurray formation. This paper presents an analysis of time-lapse and crosswell seismic data, as part of an overall study integrating different disciplines and technologies, to understand the effects of geology on SAGD-process performance in the pilot area. A 3D baseline survey was conducted at the start of the pilot in 2001, and two follow up surveys were conducted in 2004 and 2005. In addition, six crosswell seismic profiles were acquired by placing both sources and receivers in the vertical wellbores. The goal of the seismic surveys was to better understand steam-chamber growth and reservoir architecture by detecting lithology changes, including the occurrence and distribution of mudstone stringers. Data from the surveys, especially from the crosswell profiles, indicated significant reservoir heterogeneity, and helped to characterize reservoir architecture in the pilot area more accurately. Analysis of seismic data (both 4D and crosswell) showed steam-chamber growth and oil recovery to be influenced strongly by reservoir geology. Steam-chamber growth is especially affected by the presence of low-permeability facies in the vicinity of the SAGD well pairs. Our analysis indicates that these reservoir heterogeneities have contributed to the creation of areas within the reservoir that have been unaffected by steaming operations to date. These findings are in agreement with flow-simulation results and collectively contribute significantly to the planning of future developments. Introduction The SAGD process was developed conceptually and investigated experimentally by Butler (1994). Main features of the original SAGD model for the lateral spread of the steam chamber included thermal conduction ahead of a steady-moving steam-chamber interface; countercurrent gravity drainage of mobilized bitumen, or heavy oil; and vertical rise of the steam chamber. This recovery process was field tested at the Underground Test Facility (UTF) near Fort McMurray through a number of different phases of pilot operation (Edmunds et al. 1989; Komery et al. 1993). Field applications of the SAGD process have revealed several issues of considerable importance to the recovery performance, including wellbore hydraulics, reservoir heterogeneity, effects of solution gas, and production of solids (Edmunds and Gittins 1993; Ito and Suzuki 1999; Suggett et al. 2000; Ito 1999; Edmunds 1999; Birrell 2003). This paper relates initial efforts undertaken by the Christina Lake Project team to integrate geology, geophysics (specifically, seismic technology), and reservoir engineering to further the understanding of steam-chamber growth in the McMurray reservoir for the Christina Lake SAGD project. Phase 1 of the SAGD pilot was implemented in 2001 at Christina Lake with the drilling and completion of three SAGD well pairs (A1, A2, and A3). Since then, three additional well pairs have been added (A4 well pair in October 2003 and A5 and A6 well pairs in August 2004). Fig. 1 illustrates the project area (TWP 76, R06 west of 4th Meridian), which now includes six SAGD well pairs along with observation wells and disposal wells. The following discussion will be limited to A1 through A4 well pairs, as production histories for the A5 and A6 well pairs are rather limited.

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Influence of Pressure Difference Between Reservoir and Production Well on Steam-Chamber Propagation and Reservoir-Production Performance

SPE Journal ◽

10.2118/190107-pa ◽

2019 ◽

Vol 24 (02) ◽

pp. 452-476 ◽

Cited By ~ 6

Author(s):

Hao Xiong ◽

Shijun Huang ◽

Deepak Devegowda ◽

Hao Liu ◽

Hao Li ◽

...

Keyword(s):

Mathematical Model ◽

Production Rate ◽

Pressure Difference ◽

Oil Production ◽

Thermal Recovery ◽

Production Performance ◽

Production Model ◽

Steam Chamber ◽

Proposed Model ◽

Expansion Angle

Summary Steam-assisted gravity drainage (SAGD) is the most-effective thermal recovery method to exploit oil sand. The driving force of gravity is generally acknowledged as the most-significant driving mechanism in the SAGD process. However, an increasing number of field cases have shown that pressure difference might play an important role in the process. The objective of this paper is to simulate the effects of injector/producer-pressure difference on steam-chamber evolution and SAGD production performance. A series of 2D numerical simulations was conducted using the MacKay River and Dover reservoirs in western Canada to investigate the influence of pressure difference on SAGD recovery. Meanwhile, the effects of pressure difference on oil-production rate, stable production time, and steam-chamber development were studied in detail. Moreover, by combining Darcy's law and heat conduction along with a mass balance in the reservoir, a modified mathematical model considering the effects of pressure difference is established to predict the SAGD production performance. Finally, the proposed model is validated by comparing calculated cumulative oil production and oil-production rate with the results from numerical and experimental simulations. The results indicate that the oil production first increases rapidly and then slows down when a certain pressure difference is reached. The pressure difference has strong effects on steam-chamber-rising/expansion stages. However, at the expansion stage, lower pressure difference can achieve the same effect as high pressure difference. In addition, it is shown that the steam-chamber-expansion angle is a function of pressure difference. Using this finding, a new mathematical model is established considering the modification of the expansion angle, which (Butler 1991) treated as a constant. With the proposed model, production performance such as cumulative oil production and oil-production rate can be predicted. The steam-chamber shape is redefined at the rising stage, changing from a fan-like shape to a hexagonal shape, but not the single fan-like shape defined by (Butler 1991). This shape redefinition can clearly explain why the greatest oil-production rate does not occur when the steam chamber reaches the caprock. Literature surveys show few studies on how pressure difference influences steam-chamber development and SAGD recovery. The current paper provides a modified SAGD production model and an entirely new scope for SAGD enhanced oil recovery (EOR) that makes the pressure difference a new optimizable factor in the field.

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A New Method for Measuring Solvent Diffusivity in Heavy Oil by Dynamic Pendant Drop Shape Analysis (DPDSA)

SPE Journal ◽

10.2118/84202-pa ◽

2006 ◽

Vol 11 (01) ◽

pp. 48-57 ◽

Cited By ~ 32

Author(s):

Chaodong Yang ◽

Yongan Gu

Keyword(s):

Carbon Dioxide ◽

Mass Transfer ◽

High Pressure ◽

Objective Function ◽

Heavy Oil ◽

Oil Production ◽

Thermal Recovery ◽

Oil Reservoirs ◽

Pressure Cell ◽

Heavy Oil Reservoirs

Summary This paper presents a new experimental method and its computational scheme for measuring solvent diffusivity in heavy oil under practical reservoir conditions by DPDSA. In the experiment, a see-through windowed high-pressure cell is filled with a test solvent at desired pressure and temperature. Then, a heavy-oil sample is introduced through a syringe delivery system to form a pendant oil drop inside the pressure cell. The subsequent diffusion of the solvent into the pendant oil drop causes its shape and volume to change until an equilibrium state is reached. The sequential digital images of the dynamic pendant oil drop are acquired and digitized by applying computer-aided digital image-acquisition and -processing techniques. Physically, variations of the shape and volume of the dynamic pendant oil drop are attributed to the interfacial tension reduction and the well-known oil-swelling effect as the solvent gradually dissolves into heavy oil. Theoretically, the interfacial profile of the dynamic pendant oil drop is governed by the Laplace equation of capillarity, and the molecular diffusion process of the solvent into the pendant oil drop is described by the diffusion equation. An objective function is constructed to express the discrepancy between the numerically predicted and experimentally observed interfacial profiles of the dynamic pendant oil drop. The solvent diffusivity in heavy oil and the mass-transfer Biot number are used as adjustable parameters and thus are determined once the minimum objective function is achieved. This novel experimental technique is tested to measure diffusivities of carbon dioxide in a brine sample and a heavy-oil sample, respectively. It should be noted that, with the present technique, a single diffusivity measurement can be completed within an hour and only a small amount of oil sample is required. The interface mass-transfer coefficient at the solvent/heavy-oil interface can also be determined. In particular, this new technique allows the measurement of solvent diffusivity in an oil sample at constant prespecified high pressure and temperature. Therefore, it is especially suitable for studying the mass-transfer process of injected solvent into heavy oil during solvent-based post-cold heavy-oil production (post-CHOP). Introduction Western Canada has tremendous heavy oil and bitumen resources (Farouq Ali 2003, Miller et al. 2002). Approximately 80 to 95% of the original-oil-in-place is still left behind at the economic limit after cold heavy-oil production (Miller et al. 2002). This is a large oil-in-place target for follow-up enhanced oil recovery (EOR) processes. After primary production, most Canadian heavy-oil reservoirs cannot be further exploited economically by thermal recovery processes because reservoir formations are thin and/or there is active bottomwater. In the literature, some studies have been conducted to evaluate the other recovery methods for these heavy-oil reservoirs (Miller et al. 2002, Das 1995, Frauenfeld et al. 1998, Metwally 1998). Among these methods, vapor extraction (VAPEX) and other solvent-based post-CHOP processes are probably the most promising EOR techniques. In practice, the solvent can be carbon dioxide, flue gas, and light hydrocarbon gases, such as methane, ethane, propane, and butane.

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