VAPEX Process Research Articles

Effects of Fracture Parameters on VAPEX Performance: A Numerical and Experimental Approach Utilizing Reservoir-On-The-Chip

The present research carries out an in-detail study of the VAPEX process as one of the most recent solvent-based heavy oil recovery techniques in fractured reservoirs to evaluate the effect of fracture parameters on process performance. To achieve this purpose, several fractured patterns with distinct features were designed and engraved on glass pieces to manufacture state-of-the-art microfluidic models mimicking a typical Canadian heavy oil reservoir. A heavy oil sample of viscosity 1514 cP was utilized during the conducted experiments with pure propane and pure carbon dioxide as the injection solvents. A thorough image analysis operation was carried out over the experimental models to determine heavy oil produced, residual oil saturation, ultimate recovery factors, and monitor solvent chamber expansion. Numerical simulations of the same experiments were carried out for history matching and predicting other designed scenarios. Error analysis revealed average absolute errors of below 8%, showing convincing precision. Together with the simulation outcomes, a comprehensive data bank was obtained from the 30 scenarios designed and 18 VAPEX experiments conducted. The effects of fracture orientation, length, width, intensity, and position on process performance were identified and numerically evaluated. It was observed that all fractures, regardless of their properties, enhanced heavy oil recovery in comparison to the base case (no fractures) scenario. Moreover, propane proved more efficient owing primarily to its higher solubility and effective dispersion. The highest recovery factor, 65.81%, was obtained when implementing two wide vertical fractures on either side of the well pair. Almost equal to that, 64.93% was the process efficiency by positioning two long horizontal fractures between the wells.

An Exponential Solvent Chamber Geometry for Modeling the VAPEX Process

Accurate simulation of the VAPEX process relies heavily on precise modeling of the solvent chamber propagation. In the previously developed models, the solvent chamber possesses either a linear, circular, or parabolic shape. In this study, an exponential solvent chamber model was considered to represent the propagation of the chamber throughout the spreading and falling stages of the VAPEX process. The tuning parameters of the proposed model include the exponential function coefficient and the transition region thickness. These parameters are altered by employing a MATLAB-based Genetic Algorithm (GA) to minimize the error between determined and measured cumulative produced oil in four experimental case studies presented in the literature. According to the outcomes, the proposed method can accurately adjust the cumulative produced oil to the measured values in both spreading and falling stages. Additionally, the thickness of the transition region obtained by this model is in reasonable agreement with the laboratory measurements. Accordingly, the average relative errors of all four cases for cumulative produced oil and transition region thickness are 7.73% and 5.12%, respectively. Consequently, the model estimates the oil production rate with reasonable precision and the predicted solvent chamber shapes are well-aligned with the experimentally observed chambers.

Heavy Oil and VAPEX Process: A Brief Review

Heavy Oil and VAPEX Process: A Brief Review

Extraction Rate in Vapor Assisted Extraction of Heavy Oil (VAPEX)

Heavy oil recovery requires either heat (SAGD) or a solvent (VAPEX) to reduce its high viscosity first and then the less viscous oil can be recovered. We show here that the existing data on oil recovered in VAPEX process in sandpacks show a square root dependence on the height of pay zone, following expectation. This dependence had remained uncertain and is of importance in oil field operation.

A shortcut model to estimate oil production rate in VAPEX process

An analytical model for estimating the oil production rate in the vapor extraction process (VAPEX) is presented in this work. It regards the most effective properties of fluid and reservoir in the form of the Rayleigh number. The model involves three coefficients (x1, x2 and x3) that are determined through minimizing an objective function based on the difference between experimental VAPEX data and calculated data. The strength of the model was examined through comparison experimental work. Having an average relative error of 15% against the real data, the model showed its high capability for predicting the VAPEX production rate.

Numerical Study of Single Well Vapor Extraction Process

Vapor extraction (Vapex) is an emerging technology to produce heavy oil and bitumen from subsurface formations. Single well (SW) Vapex technique uses the same concept of Vapex process but only with one horizontal well. In this process solvent is injected from the toe of the horizontal well with oil production at the heel section. The main advantage of SW-Vapex process lies in the economic saving and applicability in problematic reservoirs, where drilling of two horizontal wells is impractical. The performance of SW-Vapex seems to be comparable with dual horizontal Vapex process using proper optimization schemes. This study is grouped into two sections: (i) a screening study of early time operating performance of SW-Vapex and (ii) a sensitivity analysis of the effect of the reservoir and well completion parameters. Simulation results show that solvent injection rate can be optimized to improve oil production rate. Higher injection rates may not necessarily lead to increase in production. This study confirms that SW-Vapex process is very ineffective in reservoirs with high oil viscosity (more than 1,500 cp) and thin formations (less than 10 m).

Optimization of vapex over consumption in one of the heavy oil cleft store

The process of solvent vapor extraction is a recycling method for the heavy oil application that the light hydrocarbon vapor is used as a solvent to reduce the heavy oil viscosity. The primary low recycling and the lower production flow compared with the thermal methods have faced the field applications with limitation due to the slow identity of the solvent penetration procedure in the heavy oil,. So in order to optimize and increase the production in this process, a simulation study was performed on one of the heavy oil cleft store of Iran and the solutions were presented to increase the oil recycling in this process. At first after construction of a cleft two dimensional store with multiple blocks that show the solvent vapor flowing in the cleft net, the optimization process was analyzed around two axes. First the optimization strategies presented to optimize the constructed solvent system injection in the process. Then the formation and distance between producing wells and injection on the process performance and the best condition were evaluated and developed. The results showed that the solvent composition injection method through the producing well in addition to produce the injecting well in first ten days of process with more pressure and the well formation model with subsidiary distance and the vertical determined distance, the most optimized producing performance was presented compared to other plans, this results increase the security about the field application in the VAPEX process at cleft stores Key terms: optimization, solvent vapor extraction, heavy oil, cleft stores, wells formation

Three dimensional visualization of solvent chamber growth during the VAPEX processes: An experimental approach using laser

VAPEX is a non-thermal process proposed as an alternative to SAGD due to its applicability in thinner reservoirs, advantage of energy efficiency, produced oil quality, and environmental saving. Its high cost caused by the injected solvent, however, requires further efforts to optimize the process. This, in turn, entails a clear understanding of the physics of the process. To acquire this understanding, a 3-D visualization technique was applied to a VAPEX model packed with glass beads. The oil saturated porous media and the solvent injected into the model processed refractive indices matched with the glass beads, which made the model transparent. Laser illuminated the yellow fluorescent dye dissolved in the solvent to distinguish it from the oil. Two high-speed cameras recorded the process from two sides of the model while a laser sheet moved along the model. A dome-shaped solvent chamber with viscous fingering on its top was observed. The injection pressure influenced the size of the chamber especially in the horizontal direction, which was not possible to identify through standard 2-D tests. Also, the solvent spread along the ceiling of the model and then displaced the oil down. The boundary of the solvent and oil was tilted and even curved at different injection rates. Finally, variable injection rate cases were compared with constant rate trials and an optimum operation plan was proposed through the analysis of the production rate, produced oil quality, and 3-D images of the chamber growth.

Lattice Boltzmann investigation of thermal effect on convective mixing at the edge of solvent chamber in CO2-VAPEX process

The high viscosity of heavy oil is a serious problem for the recovery efficiency of this resource by conventional methods. Since a few past years, the vapour extraction process (VAPEX) has emerged as a promising technology for the recovery of heavy oils and bitumen in reservoirs where thermal methods, such as steam-assisted gravity drainage cannot be applied. Recently, the use of CO2 as a solvent is believed to make the VAPEX process more economical and environmentally and technically attractive. Convective mixing at the edge of the solvent chamber enhances mass and heat transfer rates which increases oil mobility and production rate. The objective of this study is to analysis the influence of the main controlling parameters, such as buoyancy ratio and Prandtl number on the flow patterns and mass transfer mechanism, in order to understand the thermal effect on the dissolution of carbon dioxide through natural convection at the boundary layer of solvent chamber of CO2-VAPEX process. The numerical results obtained by lattice Boltzmann method show that the flow structure and the mass transfer mechanism are strongly depend on the buoyancy ratio and Prandtl number. So, the performances of CO2-VAPEX process are strongly influenced by thermal effect; and we found that it has negative consequences on this process.

Estimation of effect of diffusion and dispersion parameters on VAPEX process

Abstract Recent developments in heavy oil extraction have heightened the need for a promising vapor extraction process in problematic reservoirs. Due to the high energy efficiency and suitability for the latter reservoirs, it is believed that VAPEX has had a great deal of interest compared to the thermal methods in recent years. The present study aims to develop a method based on a compositional simulation in the VAPEX process to study the effect of mass transfer coefficients on production rate. This model can simulate VAPEX with different diffusion and dispersion coefficients and is validated against the experimental data. Simulation results show a challenge between mass transfer and gravity drainage process; hence, if drainage is the dominant step, a high diffusion coefficient has a reverse impact on production rate. Instead, a high dispersion coefficient almost has a positive effect on oil production.

Recovery Rate of Vapor Extraction in Heavy Oil Reservoirs—Experimental, Statistical, and Modeling Studies

The VAPor EXtraction process (also known as VAPEX) is a solvent-based enhanced oil recovery (EOR) technology that has great potential for the recovery of heavy oil and bitumen through mass transfer and gravity drainage mechanisms. In this study, laboratory tests, the multivariable regression technique, and the connectionist model optimized by a Genetic Algorithm (GA) were used to determine the oil production rate during the VAPEX process in homogeneous and fractured porous media. The smart technique and statistical models describe the VAPEX production rate in terms of three dimensionless numbers, namely the Schmidt number (Sc), the Peclet number (Pe), and a dimensionless parameter (NS) referred to as the VAPEX number. The developed smart model was constructed based on a large number of experimental data conducted under various process conditions in both training and testing phases. A comparison of results obtained from connectionist modeling, the regressive model, and the experimental VAPEX data exhibits ...

Uncertainty assessment of Vapex performance in heterogeneous reservoirs using a semi-analytical proxy model

Abstract While compositional simulators are available for modeling the recovery performance of Vapex process, computational constraints often preclude detailed numerical solution of the flow and transport differential equations, as implemented in traditional flow simulators, using an entire suite of geostatistical realizations that represent the uncertainty due to reservoir heterogeneity occurring at different scales. Proxy models that are based on analytical formulations provide efficient alternatives to expensive detailed flow simulations. A novel semi-analytical proxy has been developed to model solvent transport in Vapex at isothermal conditions. Detailed analytical formulations were derived and implemented in a calculation procedure to advance the solvent–oil interface and estimate producing oil rate with time. A mass penetration parameter was formulated, and its change with time was tracked. Results obtained from the proxy were validated against experimental data available in the literatures as well as detailed compositional simulation studies ( Shi and Leung, 2014a , Shi and Leung, 2014b ). Later, a suite of geostatistical realizations are ranked based on their cumulative oil production using this proxy, and the results demonstrate good agreement with those based on detailed compositional simulations but with significant savings in computational costs. Finally, this proxy is employed to assess impacts of uncertainty in subscale heterogeneity. An important contribution from this work is that process physics are built directly into this proxy; it represents an advantage over other alternative modeling approaches (i.e., regression) that are driven only by data. This proposed proxy can be easily integrated in existing reservoir management workflows to optimize production scenarios in a quick and robust manner. It can be applied to rank numerous geostatistical realizations and quickly identify a smaller, more manageable subset of realizations for further simulation analysis. It presents an important tool for assessing the uncertainty in reservoir properties on effective mass transfer and the ensuing recovery performance, as well as assisting decisions-making for future pilot and field development planning.

Semi-Analytical Proxy for Vapex Process Modeling in Heterogeneous Reservoirs

Vapex (vapor extraction) is a nonthermal process that has significant potential in providing a more environmentally friendly and energy-efficient alternative to steam injection. Vaporized solvent injected in-situ dissolves into the oil and reduces oil viscosity, allowing the oil to flow to a horizontal production well via gravitational forces. While compositional simulators are available for assessing the Vapex performance, the simulation process may become difficult when taking into account the uncertainty due to reservoir heterogeneity. A semi-analytical proxy is proposed to model the process, in a way analogous to the steam-assisted gravity drainage (SAGD) model described by Butler, who demonstrated the similarity between two processes with a series of Hele-Shaw experiments and derived an analytical steady-state flow rate relationship that is comparable with the SAGD case. Solvent concentration and intrinsic diffusivity are introduced in this model instead of temperature and thermal diffusivity in SAGD. In this paper, analytical solutions and implementation details for the Vapex proxy are presented. The proposed approach is then applied to various reservoirs discretized with spatially varying rock porosity and permeability values; bitumen drainage rate and solvent penetration are calculated sequentially at grid blocks along the solvent–bitumen interface over incremental time steps. Results from this model are compared against experimental data available in the literature as well as detailed compositional simulation studies. Computational requirement of the proxy in comparison with numerical simulations is also emphasized. An important contribution from this work is that process physics are built directly into this proxy, giving it an advantage over other data-driven modeling approaches (e.g., regression). It can be used as an efficient alternative to expensive detailed flow simulations. It presents an important potential for assessing the uncertainty due to multiscale heterogeneity on effective mass transfer and the resulting recovery performance, as well as assisting decisions-making for future pilot and field development.

The Interplay of Permeability, Drainage Height, Capillarity, and Solvent Type on Diffusion and Convective Dispersion in the Vapex Process: A Critical Review

Despite numerous studies on various aspects of the Vapex process, diffusion and convective dispersion phenomena are of a particular interest. The lack of knowledge in this area has resulted in significant uncertainty in design of this process. This paper assimilates and presents a review on the effects of drainage height, permeability, solvent type, and capillarity on mass transfer phenomena in the Vapex process. Due to the scarcity of phase behavior data and variety of adapted experimental approaches in literature, Vapex number was used to investigate the interplay of studied parameters on the efficiency of mass transfer phenomena in Vapex process.

Capillarity and Drainage Height Effects on the Diffusion/Dispersion Coefficient in the VAPEX Process

This study is conducted to investigate the roles of capillarity and drainage height on mass transfer phenomena during the VAPEX process in heavy oil reservoirs. A comprehensive experimental study was conducted in two 2-D slab models using Plover Lake oil from west-central Saskatchewan and n-butane as the solvent. This study revealed significant effects of drainage height and capillarity on oil drainage rates in contrast to previous studies conducted at unrealistically high permeabilities (i.e., >200 D). A new correlation was developed to predict the effective diffusion/dispersion coefficient from solvent concentration, drainage height, and total pore surface area of the porous media.

Optimization of solvent consumption in the VAPEX process

This study presents the results of a simulation study based upon the VAPEX process for heavy oil production at one of the sandstone heavy oil reservoirs. The field is currently producing oil using electrical submersible pumps. The objective of this work was to evaluate the effect of different amounts of propane on the efficiency of the vapor extraction process as an alternative enhanced oil recovery. The results revealed that the higher amounts of propane in the solvent mixture led to increase the recovery factor. However, it was shown that the lower amounts of propane increase the recovery, significantly.

Experimental Investigation of Capillarity and Drainage Height Roles in the Vapor Extraction Process

The authors present the results of a novel comprehensive experimental program to investigate the roles of capillary pressure and drainage height on the performance of the VAPEX process. Measured stabilized drainage rates at lower permeability range (5.1–6.4 D) in this study show no linear relationship with square root of permeability, as reported for experiments at high permeabilities (>200 D). In these tests stabilized drainage rates are a function of drainage height to the power of 1.1–1.3.

Modeling the VAPEX and SAGD Side Wall Process with a Wax Heating Experiment

Physical modeling of a difficult process can give useful insights on how to capture the correct physics so as to build a computer model of the process. In this article it is suggested that a candle wax experiment can simulate crude oil drainage by VAPEX (solvent application) or SAGD (heat application) along the heavy oil interface. The experimental set-up, some initial data, and some suggestions for expansion of the experiment are presented here.

Improvement of Heavy Oil Recovery in the VAPEX Process using Montmorillonite Nanoclays

In this paper, the nanoclay particles were introduced as mobile adsorbents in oil reservoirs to adsorb the asphaltenes, reduce the viscosity and enhance the dispersion. The objective of this paper is experimental investigation of enhanced heavy oil recovery using in situ nanoparticles for the first time. Moreover, two thermal analysis methods (thermogravimetry and differential thermal analysis) were used to analyze the asphaltene content of residue hydrocarbons in the swept chambers in nano-assisted and conventional VAPEX processes. Experiments were carried out using Iranian heavy oil and propane: the setup consisted of two sand-packed cells; one packed only with glass beads as the oil matrix and the other with glass beads and modified montmorillonite as the nanoclay, while they had similar porosity and permeability. The content of deposited asphaltene in swept matrixes, the propagation pattern of vapor chambers in heavy oil matrixes, and the rates of solvent consumption and oil production were determined. The results elucidated that montmorillonite changed the matrix heterogeneity and led to forming enhanced breakthroughs, to increasing the interfacial surface of vapor/bitumen and to accelerating the oil production. It was found that not only was the rate of vapor injection diminished, but the heavy oil recovery was also markedly enhanced by 30(±4)%.

The Effect of Reservoir Wettability on the Production Characteristics of the VAPEX Process: An Experimental Study

The impact of fractional wettability on the production characteristics of a VAPEX process at the macroscale was investigated. Conventional VAPEX experiments were conducted in a 220 Darcy random packing of glass beads in a rectangular physical model and n-pentane was used to recover the Cold Lake bitumen from the oil-saturated model in the absence of connate water. The composition of oil-wet beads in the packed bed was altered from completely water-wet beads to completely oil-wet beads at different proportions of oil-wet beads mixed with water-wet beads. A substantial increase (about 40%) in the production rate of live oil was observed during the VAPEX process when the wettability of the porous packing was entirely oil-wet beads. A critical oil-wet fraction of 0.66 was found for the heterogeneous packing of water-wet and oil-wet beads of similar size distribution. Above this critical composition, the live oil production rate was not affected by further increase in the proportion of the oil-wet beads. It is believed that above this critical composition of the oil-wet beads, the crevice flow process is dominated by the continuity of higher conductivity live oil films between particles through the oil-wet regions. Below this critical composition, the live oil production rate increased linearly with the fraction of the oil-wet beads in the packing. The oil-wet regions favor the live oil drainage compared to that of the water-wet regions as they enhance the rate of imbibition of the live oil from the oil-filled pores to the vacated pores near the nominal VAPEX interface. These two factors enhance the live oil production rate during the VAPEX process. The solvent content of the live oil, the solvent-to-oil ratio (SOR), and the residual oil saturation did not correlate strongly with the proportion of the oil-wet beads in the packing. The average solvent content of the live oil and the residual oil saturation were measured to be 48% by weight and 7% by volume respectively.