SAGD Research Articles

Effect of MgO Slaking on Silica Removal during Warm Lime Softening of SAGD Produced Water

MgO is added during warm lime softening (WLS) to remove silica from steam-assisted gravity drainage produced water. Although it is a general practice in the oil sand industry to avoid MgO slaking t...

Identifying Reservoir Features via iSOR Response Behaviour

To extract viscous bitumen from oil sands reservoirs, steam is injected into the formation to lower the bitumen’s viscosity enabling sufficient mobility for its production to the surface. Steam-assisted gravity drainage (SAGD) is the preferred process for Athabasca oil sands reservoirs but its performance suffers in heterogeneous reservoirs leading to an elevated steam-to-oil ratio (SOR) above that which would be observed in a clean oil sands reservoir. This implies that the SOR could be used as a signature to understand the nature of heterogeneities or other features in reservoirs. In the research reported here, the use of the SOR as a signal to provide information on the heterogeneity of the reservoir is explored. The analysis conducted on prototypical reservoirs reveals that the instantaneous SOR (iSOR) can be used to identify reservoir features. The results show that the iSOR profile exhibits specific signatures that can be used to identify when the steam chamber reaches the top of the formation, a lean zone, a top gas zone, and shale layers.

THE ANALYSIS OF THERMAL FIELDS AT THE PRIMARY STAGE OF THE STEAM-ASSISTED GRAVITY DRAINAGE PROCESS

This article analyzes the temperature distribution in a producer well at the primary stage of the steam-assisted gravity drainage process. The increase in share of hard-to-recover reserves requires using steam-assisted gravity drainage (SAGD). Its successful application, in turn, depends on warming up the inter-well zone, which demands steam circulation in both wells at the primary stage of the process. The duration of this stage affects the transition to oil production and the profitability of the process, which emphasizes the importance of analyzing thermal fields at this stage to assess its duration. The existing research does not allow estimating the temperature in the producer, using the correct formulation of the problem. This paper presents the temperature distribution in a producer for SAGD for classical and chess well patterns for the first time. The aim of the work is to choose a development system for the minimum duration of primary stage of SAGD. For this purpose, the fundamental solution of the non-stationary heat equation for a continuous stationary point source in an unbounded medium is used. The estimation of temperature, at which oil becomes mobile, allows determining the primary stage duration. The authors compare the classical and chess well patterns. In addition, they have obtained the temperature distribution in producer. The results show that classical well pattern provides faster heating of inter-well zone. It is determined that the closest injection well has the greatest influence on the temperature in the producing well.

The Influence of Interlayer on the Expansion of Steam Chamber of Oil Sand SAGD Development

The steam-assisted gravity drainage (SAGD) technology is currently a more effective frontier technology for the exploitation of heavy oil, and it has a better development effect than other exploitation methods. The formation and expansion of the steam chamber is the key to SAGD technology, and the interlayer is an important influencing factor. Therefore, it is of great significance to study the influence of the interlayer on the expansion of the steam chamber and the effect of SAGD development during the oil sand SAGD development process. In order to study the influence of the interlayer on the expansion of the steam chamber during the oil sand SAGD development process, a double-horizontal well SAGD physical experiment simulation experiment was carried out using the experimental device of the thermal recovery physical simulation system. The influence of interlayer on the expansion law of the steam chamber during the SAGD development of dual horizontal wells is studied. Studies have shown that the interlayer inhibits the longitudinal development of the steam chamber, and the steam chamber is forced to expand laterally along the interlayer to form a steam chamber similar to an inverted triangle. The steam chamber is fully developed in the area below the interlayer, but the steam chamber cannot break through the interlayer.

Experimental Study on the Process of eMSAGP

While SAGD (Steam Assisted Gravity Drainage) has been successfully deployed in recovering heavy oil/oil sand reservoirs, it suffered from low OSR (Oil-Steam-Rate) and chamber growth rate in producing super heavy oil. The SAGP technology is to inject Non-Condensable Gas (NCG) into the reservoir with steam in the SAGD process. By partial pressure effect of NCG, SAGP reduces the heat loss to overburden, thus greatly increasing OSR and reducing the demand for steam. However, it still faces the challenge of uneconomic oil rate. Introducing infill well and operating it in flooding manner, enhanced Modified Steam Assisted Gas Push (eMSAGP) can significantly speed up the growth of steam chamber and improve oil production. This work presented the physical simulation results of eMSAGP and evaluated the feasibility of its application in super heavy oil reservoir.

Real-time Performance Monitoring of Electrical Submersible Pumps in SAGD Process

Electrical submersible pump (ESP) is one of the preferred artificial lift systems in upstream oil production because of its wide operating range and endurance to harsh operating environments. In Alberta Canada, about two-thirds of steam assisted gravity drainage (SAGD) wells are equipped with ESPs. Keeping the ESPs long-term operational is one of the primary challenges faced by the operators. ESP failures are a common problem due to various reasons, such as, harsh operating conditions, improper installations, etc. Therefore, the real-time monitoring of ESP performance is indispensable as it can prevent unscheduled well shutdowns and enable preventative maintenance. In this work, aiming at the development of reliable ESP performance monitoring in SAGD process, a monitoring strategy based on a multivariate statistical technique is proposed. The strategy includes a novel first-principles based feature extraction approach, an online model update strategy and a new health index to evaluate ESP health conditions in real time. Test results on real ESP datasets are presented to highlight the efficacy of the proposed algorithm.

Changes in Oil and Water Compositions during Steam Isolation Using Gel-Forming GALKA® System in a Horizontal Well Developed by Steam-Assisted Gravity Drainage (SAGD)

Changes in Oil and Water Compositions during Steam Isolation Using Gel-Forming GALKA® System in a Horizontal Well Developed by Steam-Assisted Gravity Drainage (SAGD)

Mechanism and Energy Efficiency Evaluation of Superheated Steam Assisted Gravity Drainage Technique

Mechanism and Energy Efficiency Evaluation of Superheated Steam Assisted Gravity Drainage Technique

An advanced scaling model system for non-condensable gas steam assisted gravity drainage recovery process

Physical modeling is critical to study the performance of certain operation in heavy oil reservoirs. A well-designed experiment should guarantee the information gathered from lab would be applied to predict the thermal process in the field. To meet this requirement, the initial and boundary condition similarity between lab and field should be satisfied. It is reasonable to follow certain scaling criteria to fabricate the physical model. In addition to these conventional guidelines, this paper makes following recommendations to ensure a successful thermal recovery experiment,•To control and mitigate the steam channeling between the sand-pack and apparatus wall, the back wall is designed as it can be pushed enough to increase contact pressure.•Heat loss should be handled carefully, which impacting steam chamber growing and causing heat accumulation around the model.•A data acquisition system, based on PXI platform and Labview software, for the thermal recovery experiments had been proved valuable in evaluating the spreading progress of steam chamber.

On the ratio of energy produced to energy injected in SAGD: Long-term consequences of early stage operational decisions

Steam-Assisted Gravity Drainage (SAGD) is a recovery process used to extract bitumen from underground reservoirs. The efficiency of SAGD is determined by the volume of steam injected (reflecting cost and greenhouse gas emissions) relative to the volume of oil recovered (revenue). Another way to look at this relationship is as a ratio of cumulative energy produced to energy injected (EPEI). First described in this study, EPEI ratios offer a novel perspective on SAGD because they reduce the inter-well comparison bias caused by operational choices such as steam temperature, steam quality and well length. There are numerous studies on SAGD from an experimental, analytical or numerical simulation perspective, but all require assumptions and constraints specified in advance, and can only return an approximation of field performance. Studies that work exclusively with field data have typically been used for prediction modeling only. In contrast, this study employs a novel methodology by working within the existing constraints and operational choices of SAGD field wells to infer the number of steam-oil performance relationships present, and how long they last. One by one, we eliminate parameters that cannot cause the performance differences seen in the field using only deductive reasoning and multi-parameter sensitivity analysis, and arrive at possible reasons for the performance relationships found. 1520 SAGD well pairs in Alberta, Canada are used, which is more than 90% of the wells in Alberta over the last 20 years, and to the best of our knowledge, the largest field well set of any SAGD study to date. This comprehensive data set ensures that findings are applicable across the industry. Results reveal a new and surprising finding that the EPEI ratio is set during the first few months on production, and is very difficult to change thereafter. Hence, operators have a short, time-limited opportunity to influence each well's recovery ratio (and therefore its profitability and greenhouse gas emissions). This reflects the importance of process start-up and the first few months after start-up when the near well region of the reservoir is conditioned. Finally, the stability of the EPEI ratio permits a simple, new model capable of predicting cumulative recovery months in advance.

The Research of Vapor Phase Front Migration Rules in Steam Assisted Gravity Drainage

The degree of steam overlay and descriptions of the migration rules for vapor front is considered one of the greatest challenges to research the seepage laws of steam assisted gravity drainage. In order to surmount these challenges, the theory of percolation mechanics are introduced, combined with the well group structure of steam assisted gravity drainage, we do workings such as establishing the mathematical model of the pressure field, applying the steam overlap theory and simplifying the steam overlap coefficient, adopting the technology of database and mapping to display the trends of vapor front intuitively. At last, combined with production factor and reservoir thickness, we analyze the swept volume of steam and the influence rules of the vapor front migration. Understanding the achievements will provide a scientific basis to the improvement of steam’s sweep volume in symmetry elements, displaying the working degree of reservoirs intuitively as well as the efficient development of steam assisted gravity drainage. &nbsp

Characterizing foulants on slotted liner and probing the surface interaction mechanisms in organic media with implication for an antifouling strategy in oil production

Fouling phenomena are commonly observed in oil production processes, which have caused many challenging issues. Many previous studies focused on fouling in aqueous environment. However, the characterization of foulants and underlying interaction mechanism in organic media still remain limited, which is of fundamental and practical importance. In this work, the foulants on slotted liner samples were characterized, which have served in an oil wellbore based on steam-assisted gravity drainage (SAGD) operation for about six months. The foulants were demonstrated to be fine mineral solids (e.g., silica) and organic materials (e.g., asphaltenes). Atomic force microscope (AFM) colloidal probe technique was employed to quantify the interaction forces of silica particles or asphaltenes with carbon steel (L80) substrates with or without electroless nickel-phosphorus (EN) coating in organic media. The results demonstrated that the corrosion on L80 surface could significantly enhance the adhesion with silica particles and asphaltenes, aggravating the fouling phenomena; while the EN coating could effectively eliminate the corrosion and show good antifouling property. Quartz crystal microbalance with dissipation monitoring (QCM-D) technique was applied to investigate the dynamic adsorption behaviors of asphaltenes on iron (a major component of L80) and EN coating surfaces. The QCM-D results showed that much less asphaltenes were adsorbed on EN coating than that on iron, which agrees well with the force measurements. This work provides useful insights on the fouling processes and fundamental surface interaction mechanisms of fine solids, asphaltenes and substrates in oil, with implications on developing effective antifouling strategies (e.g., functional coatings) in oil production.

Investigation on Tripping in Magnetic Generator in Steam-Assisted Gravity Drainage Wells Based on Numerical Simulation

Abstract Magnetic Guidance Technology can meet the precise measurement requirements when drilling steam-assisted gravity drainage (SAGD) oil wells. Magnetic generator is a key part in the Magnetic Guidance Technology. When magnetic generator is tripped into horizontal well, pump pressure and passing capacity of the magnetic source generator in the curved section need to be analyzed. So, a mathematical model of tripping in the magnetic generator is established. If curvature radius, deviation angle, and friction factor are known, the forces acting on the magnetic generator in different positions could be calculated. The finite element (FE) results show that: (1) with depth increasing in the curved section, the equivalent stress on the magnetic generator increases in a fluctuating manner, the contact area, friction drag, and energy loss increase. (2) The greater the hole curvature, the greater tripping in force and the higher pump pressure are needed. The lower friction coefficient is favorable to tripping in the magnetic generator. (3) The friction between the magnetic generator and tubing wall in the horizontal section is much less than that in the curved section. Field applications have shown that the maximum downforce is close to the result of finite element analysis. The research results provide a reasonable reference basis for smooth running of magnetic source generators with different trajectory conditions.

Convection beyond the Steam Chamber Interface in the Steam-Assisted-Gravity-Drainage Process.

In the steam-assisted-gravity-drainage (SAGD) process, heat energy is transferred from the steam chamber to the farther cold reservoir by conduction and convection mechanisms, so as to reduce the oil viscosity. In previous research works, although it was proved that convection is an indispensable part of the heat-transfer process, there is still a controversy about the formation mechanism of heat convection. In this study, an analytical mathematic model was proposed to explore the convective heat transfer in SAGD operation. Typically, this model integrates three heat convection forms that are generated by pressure difference, gravity, and thermal expansion of connate water,. Subsequently, the simulation results are compared with field data to evaluate the accuracy of the new model, and they are reasonably consistent with UTF field data. The results indicate that convective heat transfer plays a predominant role in the immediate vicinity of the steam chamber interface. Furthermore, this paper derives a mathematic model of oil production to explore the effect of heat convection on oil production under different operation conditions. The results demonstrate that heat convection has an adverse impact on oil production, but it is inevitable. This study also displays that some parameters, such as the lateral spreading rate, the thermal diffusivity, the viscosity coefficient, and the curvature of oil relative permeability curve, can significantly affect the oil production rate. Based on this study, the effect of convection mechanism on the heat-transfer process and oil production will be further clarified, and the parameters in the SAGD process can be optimized, so as to effectively enhance and predict oil production.

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.

Development of a deep learning-based model for the entire production process of steam-assisted gravity drainage (SAGD)

Steam-assisted gravity drainage (SAGD) has been widely proven to enhance heavy oil recovery effectively. However, the performance evaluation of SAGD in heavy oil reservoirs usually involves time-consuming and tedious static and dynamic numerical simulations, which is not suitable for practical decision-making and prediction. As a reliable alternative modeling tool, the deep learning-based model has great potential for comprehensive data analysis and system prediction of machine learning methods. Still, it has not been widely used in SAGD development planning. In this paper, a recurrent neural network model is applied to the prediction of SAGD production information. A large number of simulation results are collected using CMG software to build a training database, which includes static parameters describing various characteristics of the reservoir and dynamic parameters for production control. The deep learning-based model is divided into two parts. One part is responsible for predicting the thermal communication in the preheating stage, and the other part is responsible for predicting the production information in the production stage, using the principal component analysis method to reduce the dimension of the input vector, limiting the overfitting and improving the quality of the prediction. Besides, an intelligent history matching technology for oilfield SAGD production is proposed. The model is designed to be controlled by a user-friendly graphical interface for user convenience and can be directly integrated into reservoir management programs. This research highlights the enormous potential of replacing traditional modeling tools with neural network models for decision-making and predicting SAGD production projects in oilfields.

Integral Model of Steam-Assisted Gravity Drainage

An integral model of steam-assisted gravity drainage is described and modified with account for inequality of heat fluxes and the steam chamber growth in the vertical direction. The model is brought into the dimensionless form convenient for analyzing the influence of different phenomena on the process and verified by means of the calculations based on the Chung and Butler experiments. Within the framework of the model the main effects occurring during the process are described.

An Improved Set of Design Criteria for Slotted Liners in Steam Assisted Gravity Drainage Operation

Slotted liners are widely used in steam-assisted gravity drainage (SAGD) wells to control sand production and sustain wellbore productivity. The slotted liner can provide desirable performance when appropriately designed. A literature review indicates a limited number of studies that offer design criteria specifically for SAGD wells. Moreover, past criteria seem to neglect some key factors, which may lead to inadequate slot design. This paper proposes a set of graphical design criteria for slotted liners in SAGD production wells, using prepacked sand retention testing (SRT) data. The SRT is designed to incorporate several essential factors that are not present in the past design criteria, such as slot density, steam breakthrough, and particle size distribution (PSD). The proposed design criteria are presented graphically for normal and aggressive conditions, where the aggressive condition accounts for the potential occurrence of the steam breakthrough. It is found that the upper bound of the design window is substantially lower for the aggressive condition due to the higher sand production after the steam breakthrough. The design criteria also indicate that the slotted liner is suitable only for the formations with low fines content.

A heat‐transfer model for tube fouling in the radiant section of once‐through steam generators

AbstractOnce‐through steam generators (OTSGs) produce steam by recycling produced water in the steam‐assisted‐gravity‐drainage (SAGD) process for extracting Alberta's oil sands via in situ recovery of bitumen. The industry's specifications for water quality, steam quality, and water recycle ratio, as well as high temperature and pressure operations, lead to the fouling of OTSG tubes, which has important economic, safety, and environmental consequences. The roles and mechanisms of inorganic and organic impurities on tube fouling also complicate the study of heat transfer in OTSGs. Heat transfer in OTSGs involves radiation, convection, conduction, forced convection, and boiling. In this investigation on OTSG fouling, a steady‐state mathematical model was built in Microsoft Excel, incorporating industry design data, to demonstrate the impact of tube fouling on heat transfer and tube‐wall temperature. The model predictions indicate that tube fouling introduces a significant thermal resistance that not only decreases the rate of heat transfer but also causes an increase in the tube‐wall temperature such that it could exceed the safe operating limits of the tube material, leading to potential tube failures. Predictions are provided for the average tube‐wall temperature exceeding the recommended operating limit of 700 K over a range of foulant thermal conductivity (ie, 0.05‐2 W m−1 K−1) and foulant thickness (ie, 0.4‐11 mm corresponding to 0.1%‐30% of the tube radius).

Evaluation of newly developed reverse demulsifiers and cationic polyacrylamide flocculants for efficient treatment of oily produced water

For treating oily produced water (OPW) originating from the steam-assisted gravity drainage (SAGD) process, we prepared three water-soluble and cationic reverse demulsifiers - poly aluminium chloride and quaternary ammonium salt (PAC-QAS), polyamine (PA), and polyamine and poly aluminium chloride (PA-PAC). Their effectiveness in destabilizing the emulsion and removing oil and suspended solids from OPW and the synergistic effect with cationic polyacrylamide flocculants (CPAMs) were examined through bench-scale and field tests. The effects of chemical properties, injection dosage, and influent water quality on separation efficiency were discussed in detail. Results from microscopic observations and bottle tests reveal that polyamine-type reverse demulsifier could effectively separate oil from OPW. Its surface-active components enabled to induce morphological changes of the emulsified oils in the aqueous phase by absorbing at the oil-water interface, replacing the natural surfactants, and weakening the interfacial film strength, which promoted the collision and coalescence of small oil droplets. The subsequent bridging and sweeping effects driven by flocculant further strengthened the treatment performance. The optimal combination of PA and CPAM-2 could remove up to 90 % oil and 85 % suspended solids from OPW. Compared to flocculant, the insufficient dosage of reverse demulsifier resulted in worse separation, signifying that the demulsification played a more significant role. The correlation of treatment performance obtained from bench-scale and field tests showed that lower chemical dosages were required in the practical application, indicating the economic applicability and operability for oily wastewater treatment.