Solvent Co-Injection Research Articles

The macro and micro analysis on EOR mechanisms during steam and solvent thermal recovery in heavy oil reservoirs

Using only pure steam as a driving medium in heavy oil reservoirs may result in a low oil recovery factor. Solvent is a good oil displacement medium that can be dissolved in heavy oil, which can greatly reduce the viscosity and improve the mobility of heavy oil. Therefore, the method of solvent assisted displacement and drainage has the unique advantage during steam flooding. In this paper, a quantitative method is proposed to choose appropriate solvents. Then a series of experiments are carried out, including oil displacement experiment to measure oil displacement efficiency, 2D visualization experiment to analyze the sweep efficiency and remaining oil distribution, and 3D scaling physical simulation setting with bottom water condition, which are used to analyze production performance, the expanding characteristics of steam chamber and study reservoir fluid distribution. The results show that steam moving upwards to heat and drive heavy oil to production well under the action of displacement and drainage. In a heavy oil reservoir with thin bottom water, if only steam is injected into reservoir, then there is no obvious stage of stable oil production and the oil recovery factor is only 32.7%. However, when solvent and steam are co-injected into reservoir, the stage of stable oil production maintaining about 0.6 PV and the oil recovery factor is 43.2%. During steam and solvent flooding, solvent can greatly reduce the oil viscosity to improve its mobility; meanwhile solvent can promote the expansion of steam chamber. The co-injection of steam and solvent can obviously expand steam chamber and increase oil recovery factor in heavy oil reservoirs (even connecting with bottom water layer). The method of steam and solvent flooding further enriches EOR technologies of thermal recovery in heavy oil reservoirs.

Experimental Study on Optimizing Steam Solvent Co-Injection Process in Akan Carbonate Oilfield

Steam solvent co-injection processes are generating considerable interest in terms of improving heavy oil upgrading in unconventional reservoirs. The characteristics of the opted solvents in the field have not been dealt with in depth. This paper presents a study on selecting the most optimal solvent for the Akan oilfield enhanced oil recovery (EOR). The first step in this work consisted of determining the Akan oil field viscosity, through an elemental and SARA analyses. Next, a set of physical and chemical methods was used to understand the mechanism of solvents’ effect on oil viscosity dynamics. The compositions of the used solvents were analyzed by a gas chromatography-mass spectrometer system equipped with a mass selective detector ISQ (USA). The evidence from the present study suggests that toluene and o-xylene are the most optimal solvents for enhancing the Akan oil recovery and reducing its viscosity. The obtained data demonstrated a higher efficiency of the used solvents on the oil viscosity reduction where the maximum oil viscosity reduction was observed in the presence of toluene, which led to a value of 178.1 mPa.s. Moreover, the obtained results reported that the solvent co-injection process efficiency increases gradually depending on the chemical composition of the used solvent, as witnessed by the obtained oil recovery factor (RF) values. It has been found that the oil recovery factor values during the capillary soaking in the presence of water was equal to 20%, in the presence of o-xylene it was equal to 61%, and in the presence of toluene, it was equal to 69%. Likewise, a similar efficiency behavior has been demonstrated during filtration experiments where water led to a 26% recovery factor, o-xylene to 69%, and toluene to 78%, meanwhile the solvent slug led to 65%. The results of this study would seem to suggest that the viscosity of the investigated oil decreases in the presence of aromatic solvents, such as toluene and o-xylene, as witnessed by the recovery factors they demonstrated. A consequence of these changes is the possibility that aromatic solvent molecules tend to separate the asphaltene layers and reduce the overlap between large asphaltene macromolecules, which leads to the dissociation of asphaltene aggregates.

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.

Solvent co-injection with steam-assisted gravity drainage process performance evaluation–New analytical treatment in relation to constant injection rate

Steam-based enhanced oil recovery methods like Steam-Assisted Gravity Drainage (SAGD) for extracting extremely heavy oils and bitumen are energy intensive and require high steam volumes with steam generation resulting in significant greenhouse gas emission. The oil industry has resorted to adding solvent to steam aiming to overcome these limitations. A new analytical model is developed for describing solvent co-injection with steam (solvent-SAGD) process in relation to constant injection rate, for the first time, based on the combination of an overall solvent mass balance, heat balance and volumetric oil displacement and Darcy's oil rate using a mixture viscosity model as a function of temperature and solvent concentration ahead of a moving vapor-oil front which satisfy the equilibrium in the system. The objectives of this work are to evaluate the performance of the solvent-SAGD process by predicting; vapor chamber growth, oil production rate, solvent production rate, solvent loss (or solvent retention) rate, and the effect of solvent type and concentration on the process. The mechanism of oil recovery by steam with added solvent is not clear. Given the controversy regarding the use of solvents with steam, by developing the new mathematical approach, this study is intended to explain whether solvent-SAGD process increases oil recovery compared to SAGD or not. If any, which solvent results in better recovery. The results of this approach give a better understanding of the oil production mechanism during the solvent-SAGD process by interconnecting vapor chamber conditions and the conditions of heated and diluted oil ahead of the moving vapor-oil interface. The results show that mass transfer occurs over a scale of centimeters, while heat transfer scale is of the order of meters. The rate of solvent retention increases over time, while the production rates of solvent and bitumen decrease. Also, it is shown that the solvent-SAGD process which is a combination of heat and mass transfer would yield a higher oil recovery, if viscosity reduction from dilution at a lower temperature is greater than viscosity reduction by temperature in the SAGD process, for the same total injection rate.

Improved CE(SDS)-CZE-MS method utilizing an 8-port nanoliter valve.

Capillary sieving electrophoresis utilizing SDS (CE(SDS)) is one of the most applied methods for the analysis of antibody (mAb) size heterogeneity in the biopharmaceutical industry. Inadequate peak identification of observed protein fragments is still a major issue. In a recent publication, we introduced an electrophoretic 2D system, enabling online mass spectrometric detection of generic CE(SDS) separated peaks and identification of several mAb fragments. However, an improvement regarding system stability and handling of the approach was desired. Here, we introduce a novel 8-port valve in conjunction with an optimized decomplexation strategy. The valve contains four sample loops with increased distances between the separation dimensions. Thus, successively coinjection of solvent and cationic surfactant without any additional detector in the second dimension is enabled, simplifying the decomplexation strategy. Removal efficiency was optimized by testing different volumes of solvents as presample and cationic surfactant as postsample zone. 2D measurements of the light and heavy chain of the reduced NIST mAb with the 8-port valve and the optimized decomplexation strategy demonstrates the increased robustness of the system. The presented novel set-up is a step toward routine application of CE(SDS)-CZE-MS for impurity characterization of proteins in the biopharmaceutical field.

Analytical Modeling of the Cyclic ES-SAGD Process

Approximately half of the daily oil production from the Canadian oil sands comes from the application of steam assisted gravity drainage (SAGD). Due to the high steam requirements of SAGD, many studies have focused on solvent injection as a means of reducing the steam consumption. One of the multiple variations of the steam-solvent injection process consists on the intermittent co-injection of solvent with steam, also known as a cyclic expanding-solvent (ES)-SAGD process. The current study represents a first attempt to create an analytical model that can describe a cyclic ES-SAGD process. The proposed analytical model uses previous SAGD and ES-SAGD models to describe the steam plus solvent stages of the process. The results obtained from the analytical model were contrasted against numerical simulation results for cases in which the solvent was hexane, pentane, and butane, as well as for cases in which hexane is a solvent and the injection cycle length is variable. In all cases, it was seen that the cumulative oil production computed by the analytical model and the numerical model are in good agreement. Over the range of conditions that were tested the absolute relative difference in the cumulative oil production, after a period of 10 years, ranged from 8.6% to 9.4%, with a median value of 9%. However, compared to the numerical simulations, the analytical model did not fully match the oil rate and the steam chamber shape. This difference was attributed to the analytical model’s simplified description of heat and mass transfer during the process. Thus, it is recommended that further studies be conducted, and recommendations for further investigations are given.

Online mass spectrometry of CE (SDS)-separated proteins by two-dimensional capillary electrophoresis.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is the fundamental technique for protein separation by size. Applying this technology in capillary format, gaining high separation efficiency in a more automated way, is a key technology for size separation of proteins in the biopharmaceutical industry. However, unequivocal identification by online mass spectrometry (MS) is impossible so far, due to strong interference in the electrospray process by SDS and other components of the SDS-MW separation gel buffer. Here, a heart-cut two-dimensional electrophoretic separation system applying an electrically isolated valve with an internal loop of 20nL is presented. The peak of interest in the CE (SDS) separation is transferred to the CZE-MS, where electrospray-interfering substances of the SDS-MW gel are separated prior to online electrospray ionization mass spectrometry. An online SDS removal strategy for decomplexing the protein-SDS complex is implemented in the second dimension, consisting of the co-injection of organic solvent and cationic surfactant. This online CE (SDS)-CZE-MS system allows MS characterization of proteoforms separated in generic CE (SDS), gaining additional separation in the CZE and detailed MS information. In general, the system can be applied to all kinds of proteins separated by CE (SDS). Here, we present results of the CE (SDS)-CZE-MS system on the analysis of several biopharmaceutically relevant antibody impurities and fragments. Additionally, the versatile application spectrum of the system is demonstrated by the analysis of extracted proteins from soybean flour. The online hyphenation of CE (SDS) resolving power and MS identification capabilities will be a powerful tool for protein and mAb characterization. Graphical abstract Two-dimensional capillary electrophoresis system hyphenated with mass spectrometry for the characterization of CE (SDS)-separated proteins. As first dimension, a generic and high MS-interfering CE (SDS) separation is performed for size separation. After heart-cut transfer of the unknown CE (SDS) protein peak, via a four-port nanoliter valve to a volatile electrolyte system as second dimension, interference-free mass spectrometric data of separated mAb fragments and soybean proteins are obtained.

Reducing the Energy and Steam Consumption of SAGD Through Cyclic Solvent Co-Injection

The amount of oil that is contained in the Canadian oil sands represent the third largest oil accumulation in the world. Approximately half of the daily oil production from the oil sands comes from mining processes and the other half is produced mostly using steam assisted gravity drainage (SAGD). This method is effective at reducing the viscosity of the oil. However, the generation of steam requires a significant amount of energy. Thus, there is an ongoing effort to reduce the energy needed to produce oil from the oil sands. In this article the intermittent injection of a solvent, along with steam, is investigated as a means of reducing the amount of energy required to extract oil from the Canadian oil sands. A simulation-based study examined the effect of the type of solvent, the cycles’ duration, the solvent concentration and the number of cycles. The simulations covered a time span of 10 years during which several different solvents (methane, ethane, propane, butane, pentane, hexane, and CO2) were injected under varying injection schedules. The solvents that were investigated are compounds that are likely to be readily available at a heavy oil production site. The solvent injection periods ranged from six to 24 months in length. The results reveal that SAGD combined with intermittent injection of hexane resulted in the most significant improvement to the cumulative oil production and in the cumulative energy-oil ratio (cEOR). Compared to SAGD without solvent injection, the cumulative oil production was increased by 45% and the cEOR was reduced by 23%. It was also seen that the performance of the proposed process is highly dependent on the resulting physical properties of the solvent-bitumen mixture. Finally, a simplified economic analysis also identified SAGD with intermittent hexane injection as the scheme that resulted in the highest net present value. Compared to SAGD without solvent injection, the intermittent injection of hexane led to an 85% increase in the net present value.

Coinjection of C6, C7, and CO2 with steam to improve low-pressure SAGD process

Steam assisted gravity drainage (SAGD) is one of the most widely used processes of thermal recovery for heavy oil. Investigating the effectiveness of solvent coinjection with steam is an important aspect in the optimisation of SAGD process. So far, however, the effects of using CO2 have not been closely examined. This study sheds light on the addition of hydrocarbon solvents with CO2 which reached earlier maximum ultimate oil recovery (90%) than that for other solvents coinjection. This study shows that solubility of C6, heat loss reduction and CO2 diffusion, are the main recovery mechanism in enhancing oil recovery. The present study highlights the steam propagation in the presence of C6 and CO2 and its relation to enhancing oil recovery. It is interesting to observe that physical properties of the injected fluid reduce the energy consumption. Another finding is that solvent coinjection leads to stable subcool, hence increase oil recovery.

Mathematical model for one-dimensional oil displacement by steam injection with solvent addition

Recently, co-injection of steam and solvent has shown to be an attractive technique to increase oil recovery, combining the advantages of viscosity reduction due to the heat transfer achieved from steam injection with the benefits of mass transfer obtained from miscible flooding. In this work, the problem of one-dimensional displacement of oil by steam injection combined with solvent is analyzed. The mathematical model is based on the mass conservation of components oil and solvent, and conservation of system energy. The solution, composed by shock and rarefaction waves and constant states, is obtained using the method of characteristics. Different solution structures were found for particular sets of reservoir-fluid system parameters, which are defined by the ratio between the value of Henry's constant and the system pressure. The results presented here may be used for fast and efficient evaluation of technical aspects of the best Enhanced Oil Recovery method for a particular field, specially for thin shallow viscous heavy oil reservoirs. This model is also useful for the development of streamlines simulators, where gravity and capillary effects are neglected.

Vapor–Liquid Equilibrium of Bitumen–Ethane Mixtures for Three Athabasca Bitumen Samples

Steam–solvent coinjection processes have received more attention in the past decade due to the environmental impact of the pure steam injection process. Increasingly restrictive environmental regulations including carbon tax have served to push the industry to consider coinjection processes (steam + solvent) to reduce greenhouse gas emissions. Understanding the phase behavior of solvent/bitumen mixtures is critical for feasibility studies as well as the design and implementation of a successful coinjection process. This study presents the vapor–liquid equilibria for bitumen/ethane mixtures and their applications for bitumen recovery processes. Experiments were conducted for temperatures up to 190 °C and pressures up to 10 MPa to simulate the conditions of in situ steam processes. The results of our vapor–liquid equilibrium experiments include solubility, viscosity, and density measurements of the saturated liquid phase, k-values, and gas oil ratio. Increasing the temperature from 50 to 150 °C resulted in ...

Enhanced heavy oil recovery (SAGD), coinjection of steam and solvent, reduction of CEOR and CSOR

ABSTRACTThe effect of coinjection of hydrocarbon solvents (C4, C5, C6, C7, and C8), with steam at low pressure, on heavy oil recovery is addressed. It is concluded that the coinjection of solvents reduced cumulative steam oil ratio and the lighter solvents performed better in reducing cumulative net energy oil ratio (CEOR, GJ/m3). The work illustrated that C6 was the best-performing solvent with respect to oil recovery (EOR) at 20 wt%, CEOR with an optimum of 30 wt%. An explanation on the reason for the highest EOR at 20 wt% is given. The coinjection with CO2 has also been addressed here with different schemes.

Radio-Frequency Heating Combined With Solvent Injection for Heavy-Oil Recovery

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 180709, “Heavy-Oil Recovery by a Combination of Radio-Frequency Heating With Solvent Injection,” by I. Bogdanov, SPE, S. Cambon, and M. Mujica, CHLOE, and A. Brisset, SPE, Total, prepared for the 2016 SPE Canada Heavy Oil Technical Conference, Calgary, 7–9 June. The paper has not been peer reviewed. The most popular technology for producing heavy oil (HO) and bitumen is reservoir heating, mainly by steam injection. Electromagnetic (EM) heating is a capable alternative. Radio-frequency heating (RFH) results from the microwave effect and has the advantage of avoiding problems associated with water supply and treatment. The advantages of RFH technology can be strengthened with solvent injection. After a period of preheating, solvent injection may lead to improved oil recovery because of additional decrease in oil viscosity. Introduction The complexity of HO recovery has inspired profound modifications in production technology. To find a successful technology, combinations of known mechanisms are considered frequently. Many of these modifications use solvent coinjection. No single commercial reservoir simulator is able to compute the interaction of an RF antenna with a reservoir. Despite this, field-scale RFH simulations have been performed with coupled simulators, which separately model reservoir dynamics and in-situ EM-field distribution. Although limited in computational performance, this approach can be used successfully for field-scale simulations. The principal object of the numerical study presented in this paper is the solvent/HO mixture under RFH conditions in an HO reservoir. The study has attempted to shed light on whether solvent-assisted RFH technology is capable of improving oil-recovery efficiency and to specify its advantages and draw backs in a typical Athabasca deposit. Simulation Model Large-scale RFH models have numerically simulated realistic oil recovery, providing a technical basis for critical analysis of oil-recovery processes. The numerical methodology based on loose coupling of reservoir and EM-field simulators has been developed recently. A coupling code has been built that simultaneously launches two simulators and initializes problem geometries and grids. The strong point of this approach is that the thermal multicomponent flow and the EM-field calculations can be presented on different grids adapted to their specific solutions. Main Results and Discussion Preheating. Preheating is necessary to enhance well connectivity and allow solvent injection. This period is common in thermal recovery for highly viscous oils. Two important advantages of RFH-based oil recovery during the preheating phase are that (1) well-injectivity problems do not exist for EM fields and that (2) the EM heating field is volumetric, spread over a certain distance in the reservoir, and, hence, may be more efficient than standard steam-circulation options. It should be noted, however, that other factors such as heating geometry related to well configuration can affect the efficiency of this process and should not be neglected.

Selection of efficient solvent in solvent-aided thermal recovery of bitumen

In solvent-assisted thermal recovery of bitumen, steam and solvent transfer their latent heat to the oil sands, mobilize the bitumen and co-condense on steam-bitumen interface. The mixing of heated bitumen with solvents further reduces its viscosity and the mobilized oil drains by gravity toward the production well. Co-injection of steam and solvent results in a gravitationally unstable diffusive boundary layer leading to convective dissolution of bitumen and solvent and thereby increases the oil recovery. We present a linear stability analysis to study the growth of convective instabilities and determine the onset of convective dissolution and the initial wavelength of instabilities. The scaling relations obtained from the linear stability are used to find the optimum solvent for solvent-aided thermal recovery processes by taking into account the azeotropic nature of solvent and steam co-condensation. The results show that an n-alkane carbon number range between 7 and 9 leads to earlier onset of convective dissolution, which is in agreement with the results of reservoir simulations. This study provides a fast screening method for selection of efficient solvent for the solvent-aided thermal recovery processes. In addition, the predicted initial wavelengths of instabilities facilitates selection of the proper grid size in numerical simulation of solvent and steam recovery processes.

How to select the right solvent for solvent-aided steam injection processes

Solvent-steam processes gained popularity in recent years in the extraction of high-asphaltenes-content heavy hydrocarbons. However, while solvent selection is key for the success of these processes, the criteria for solvent selection are still not fully established. In this study, three asphaltenes insoluble (propane, n-hexane, carbon dioxide) and one asphaltenes soluble (toluene) solvents were tested on solvent-aided steam processes to extract a bitumen sample from Alberta, Canada. Both steam flooding and SAGD performances were analyzed. The impact of clay presence was investigated by conducting experiments with and without the addition of clays, consisting of an illite-kaolinite mixture. The results of this study suggest that the produced oil samples from steam injection processes are in the form of water-in-oil emulsions. It has been observed that the amount of asphaltenes in produced oil determines the amount of water trapped in the form of emulsions. Co-injection of solvent with steam decreases the interfacial film between water and asphaltenes. However, asphaltenes insoluble solvents were found to be more effective to eliminate the forces at the oil-water interface. Presence of clays also reduced the water content of emulsions. The results of this study suggest that carbon dioxide, which is a non-hydrocarbon asphaltenes-insoluble solvent, yields the greatest quality oil with the lowest amount of water and clay in produced oil and provides high oil recovery. Hence, it is recommended to use asphaltenes-insoluble, non-hydrocarbon solvents for the extraction of low API gravity, high viscosity, and high asphaltenes content reservoirs.

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...

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 ...

Solvent-Enhanced Steamdrive: Experiences From the First Field Pilot

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 175414, “Solvent-Enhanced Steamdrive: Experiences From the First Field Pilot in Canada,” by M.L. Verlaan, SPE, and R. Hedden, SPE, Shell Canada; and O. Castellanos Díaz, V. Lastovka, SPE, and C.A. Giraldo Sierra, Shell Chemicals Americas, prepared for the 2015 SPE Kuwait Oil and Gas Show, Mishref, Kuwait, 11–14 October. The paper has not been peer reviewed. In recent years, the addition of a hydrocarbon condensate to steam operations in heavy-oil and bitumen reservoirs has emerged as potential technology to improve not only oil recovery but also energy efficiency. The idea of solvent addition to a steamdrive process has been extended and applied for the first time in the Peace River area in Canada. There, evidence was obtained of oil uplift in the patterns where solvent was injected. However, piloting this new technology in a brownfield had many challenges, especially when evaluating its main economic factors: production increase and solvent recovery. Introduction Vertical-well steamdrive (VSD) is the selected process to recover bitumen from the Peace River Bluesky formation. Solvent coinjection has been identified as an economical method to improve the efficiency of this process. In an early phase of the steamdrive, a slug of hydrocarbon condensate (diluent) is coinjected with the steam. The solvent condenses at the cold steam/bitumen interface to form a solvent bank. This bank has the potential to accelerate bitumen production by viscosity reduction and to improve ultimate recovery. The efficiency of the diluent coinjection in a steamdrive process is expected to be lower than that of liquid addition to steam for enhanced recovery; however, the solvent recovery factors are expected to be much higher. The solvent recovery, therefore, is a key factor in the economic viability of the process. The main objectives of the pilot were to obtain a positive response in bitumen production and accurate quantification of the diluent recovery. An accurate assessment of the bitumen-production increase was not expected because of the small size of the pilot and lack of control patterns; hence, the injection slug size and concentration were designed to obtain a significant and measurable bitumen response. Pilot Design The Peace River lease in Alberta, Canada, has been subject to many well-and recovery-technology trials in the last 30 years. One of the technologies tried is cyclic steam stimulation (CSS) with multilateral horizontal wells. Pad 19 has been developed with so-called “soak radial wells”—four horizontal laterals in a cross pattern. Over a 9-year time frame, bitumen has been produced in seven to eight CSS cycles. With a recovery of less than 20% from the initial design, a part of the pad has been converted to a pattern steamdrive to increase recovery to more than 50%. Vertical injectors and producers are drilled to complete the 5-acre inverted- fivespot patterns. Vertical producers are perforated over almost the complete interval, while steam injectors have been completed with five limited-entry perforations (LEPs) to distribute the steam evenly over the entire reservoir interval.

Investigating Well Spacing and the Solvent-Aided Process

The feasibility of using fewer wells in a steam-assisted-gravity-drainage (SAGD) project during solvent coinjection was investigated, which resulted in a field test showing that using a wider well spacing with a solvent-aided process (SAP) enhances production and reduces the steam/oil ratio (SOR). Compared with a steam-alone process or SAGD, fewer well pairs are required to drain a given reservoir pool.