PRISM :: Browsing by Author "Chen, Zhangxing (John)"

Browsing by Author "Chen, Zhangxing (John)"

Now showing 1 - 20 of 93

Open Access
A Genetic Algorithm Optimizer with Applications to the SAGD Process
(2013-07-12) Chen, Zhen; Chen, Zhangxing (John)
Steam-assisted gravity drainage (SAGD) using parallel pairs of horizontal wells, one drilled for steam injection and the other for oil recovery, is the most widely used and effective in-situ method for recovering the Canadian oil sands. An optimization task is used to identify the parameters that will produce either a maximum or minimum value for objective functions the user specifies. In the area of reservoir simulation, the parameters can be well spacing to identify optimal field development plan, or a steam injection pressure/rate and a liquid production rate in the SAGD process for optimal operating conditions. The objective functions may be physical quantities, such as cumulative oil produced, the recovery factor, and the cumulative steam-oil ratio, or an economic index like net present value (NPV) dependent on those physical quantities. They can also be a function independent on the physical quantities, e.g., a history match data error if the optimization task is history match. The objective of this thesis is to develop an optimizer using a genetic algorithm that can be used to optimize a variety of tasks in reservoir simulation, including the history match error minimization, the optimal field development plan, production optimization and process optimization. In this work, the genetic algorithm using both binary and continuous encoding is designed and developed, which can be coupled with a reservoir simulator to study optimization tasks in reservoir simulations. This genetic algorithm is benchmarked with the traditional gradient based optimization algorithm. The genetic algorithm optimizer coupled with a reservoir simulator is used to optimize the steam injection rates over the life of a steam-assisted gravity drainage process in a reservoir with gas cap. The parameter sensitivities of the genetic algorithm are studied.
Open Access
A GMRES Solver with ILU(k) Preconditioner for Large-Scale Sparse Linear Systems on Multiple GPUs
(2015-09-28) Yang, Bo; Chen, Zhangxing (John)
Most time of reservoir simulation is spent on the solution of large-scale sparse linear systems. The Krylov subspace solvers and the ILU preconditioners are the most commonly used methods for solving such systems. Based on excellent parallel computing performance, GPUs have been a promising hardware architecture. The work of developing preconditioned Krylov solvers on GPUs is necessary and challengeable. We devote our efforts into the development of the GMRES and the ILU(k) preconditioner on a multiple-GPU architecture and achieve favorable speedup effects. Our GPU computation includes the algorithms such as SPMV, nested RAS, decoupled ILU(k) and parallel triangular solver, etc. The numerical experiments prove that our preconditioned GMRES algorithm is feasible and works well on a multiple-GPU workstation.
Open Access
A New Material Balance Methodology for Quintuple Porosity Shale Gas and Shale Condensate Reservoirs
(2016) Orozco Ibarra, Daniel Ricardo; Aguilera, Roberto; Chen, Zhangxing (John); Kantzas, Apostolos
A recent petrophysical formulation states that all the storage mechanisms present in shale reservoirs are best represented by a quintuple porosity system that is further fed by dissolved gas in the solid kerogen. The quintuple porosity system is made up of: 1) adsorbed gas in the pore walls of the organic matter, 2) free gas stored in the inorganic matrix porosity, 3) free gas stored in natural fractures (microfractures and slot porosity), 4) free gas stored in the hydraulic fractures created around the wellbore by the stimulation job, and 5) free gas stored in the organic nanopores. This thesis presents a new material balance methodology for shale gas and shale condensate reservoirs that considers all the aforementioned storage mechanisms. Results lead to the conclusion that ignoring the effects of gas diffusion from kerogen in shale material balance calculations can lead to pessimistic estimates of both OGIP and production forecasts.
Open Access
A Novel Data Science Approach to Estimate a Borehole Caliper Log Utilizing Tripping Data
(2024-08-14) Prasad, Mandyam Rangayyan Prathik; Shor, Roman; Kantzas, Apostolos; Innanen, Kristopher; Chen, Zhangxing (John)
During drilling operations, monitoring the borehole integrity is crucial. Borehole irregularities, such as constrictions, ledges, and breakouts, can lead to significant non-productive time and present challenges when casing and cementing the well, adversely affecting operational efficiency. These issues are particularly problematic during tripping – the process of moving the drill string in and out of the borehole. However, monitoring rig data during trips presents an opportunity to monitor the same problems. Early identification of such dysfunctions allows proactive measures to mitigate their impact on operations. This technique shows promise for estimating borehole quality in advance of wireline caliper measurements while also allowing for deeper estimation in geothermal wells where current caliper tools cannot log due to high temperatures. This study introduces a novel forward/backward modelling strategy that utilizes resistance signatures in conjunction with drill string configurations to identify and quantify borehole dysfunctions, thereby enhancing operational efficiency. This approach is based on the analysis of overpull, calculated by subtracting the expected hook load (HL) calculated from a soft string drill string model from the real-time measurements of HL. Two signals were used for analysis: the Bottom Hole Assembly (BHA) configuration signal and a synthetic resistance signal. The BHA signal represents the outer diameter (OD) of the BHA, whereas the synthetic resistance signal represents the borehole gauge vs. depth. A synthetic overpull signal can be obtained by convolving the BHA signal with the resistance profile at each depth. In the reverse problem, the real overpull signal may be deconvolved with the BHA signal to estimate the resistance signal. The model was applied to actual overpull data from a drilling operation. First, the resistance signal was manually estimated to enable the overpull signal to match the field data. There was a good match between the resistance signal and the measured four-arm caliper log. A backward model was then applied to calculate the resistance signal. For shallow depths, the model is capable of detecting changes in the caliper log; however, for deeper depths, drill string dynamics confound the signal, presenting an opportunity to perform further work.
Open Access
Accelerating the GMRES solver with block ILU(k) preconditioner on GPUs in reservoir simulation
(Journal of Geology & Geosciences, 2015) Chen, Zhangxing (John); Liu, H.; Yang, B.
This paper studies the parallelization of the restarted GMRES solver, GMRES (m), and the block ILU (k) preconditioner on GPUs used in petroleum reservoir simulations. The difficulty is how to accelerate this preconditioner with a variable block size. In this paper, parallel solution techniques for block triangular systems are proposed, which work for matrices with an arbitrary block size. These techniques also work with an arbitrary level k for the block ILU (k) preconditioner. Numerical experiments show that the GPU-based linear solver GMRES (m) is much faster than its CPU version.
Open Access
An Equation-of-State Based Mathematical Modeling of Four-Phase Flow in Porous Media
(2013-04-30) FEIZABADI, SEYED ALI; Abedi, Jalal; Chen, Zhangxing (John)
Nowadays, oil and gas field development requires more comprehensive and precise simulations using geological, physical and chemical models than before. In fact, reservoir simulation has become an increasingly widespread and important tool for analyzing and optimizing oil recovery projects and reducing risks in development decisions. As energy demand increases and conventional hydrocarbon resources and reserves decline, new complicated recovery methods emerge such as solvent injection. Solvent injection is a method with the purpose of the viscosity reduction of heavy oil and bitumen. In this method, solvent (like propane, CO2, etc) is injected into the reservoir and diluted oil is produced. Application of this method may lead to the presence of four-phase flow in the reservoir, as it has been acknowledged in numerous papers available in the literature on oil recovery by solvent injection. In the past thirty years, the development of compositional reservoir simulators using various equations of state (EOS) has been addressed by many researchers. However, the development of compositional simulators that can handle more than two hydrocarbon phases in conjunction with EOS formulation has been particularly ignored or received very little attention. In the solvent injection simulation, the condensed solvent is a hydrocarbon; therefore, it is usually included in the oil phase. This is problematic because the simulator uses mixture properties for the oil phase within a grid whereas in reality, there are cases where the solvent-rich liquid phase and the diluted oil occupy separate spaces within the pores. It would be more accurate and align with physical reality to have another phase in the simulator for the solvent-rich liquid. Considering such a fourth phase in the simulation would allow us to track and monitor the behavior of solvent in the system accurately and make it possible to manage the recycle of the solvent in the operation similar to water in SAGD. The oil relative permeability would need to be portioned between the diluted oil (L1) phase and the solvent-rich liquid phase (L2) so that there are relative permeabilities for each of the oil phases (four-phase relative permeability). In addition, there needs to be diffusion of components in these two liquid phases into each other at the pore scale within a grid (this would be an analytical or empirical based calculation). After the properties of the two liquid phases become similar, it might be possible to combine them. This dissertation can be divided into two major parts of phase equilibrium and fluid flow in porous media. The results from phase equilibrium modeling have been implemented into the part of the fluid flow in porous media and this modeling has been extended up to four phases in equilibrium. The IMPES (implicit pressure and explicit saturations) approach has been used to solve the system of equations. Results of this modeling show that the second liquid phase forms in a certain range of pressure, temperature and composition. It has been found that the effect of this second liquid phase is considerable on the oil (L1) production.
Open Access
An integrated multi-component reservoir-wellbore thermal model
(2012) Dong, Chao; Chen, Zhangxing (John)
As more and more wells have been put into operation, accurate modeling of wellbore flow plays a significant role in reservoir simulation, particularly in thermal recovery processes such as Steam Assistant Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS). The main objective of wellbore modeling is to predict heat exchange and phase behaviour in the vertical and horizontal wellbores and therefore to predict their effect on the entire simulation process. Coupled reservoir and well modeling can provide a detailed description of these thermal processes. To model these processes, a thermal K-value multi-component reservoir model is developed. This model has the ability to simulate three-dimensional multi-component, three-phase thermal processes such as SAGD and CSS. Two corresponding sets of wellbore models, Sink/Source Well (SSW) and Multi-Segment Well (MSW) models, are developed and tested to achieve several result. The SSW model consists of a set of well control methods. It is chosen as the reference wellbore model in this study and validated with commercial software. In this study the MSW model is also constructed and tested for several thermal recovery processes. The MSW model includes mass and energy conservations for each component, constraints and a general pressure drop relationship. The multiphase wellbore flow is represented using a no- lip or slip model. It has the ability to deal with complex configurations such as multi-tubing situation; several reults are included in the thesis. Three type of coupling schemes for the MSW model are also tested and compared in this research: full, iterative or advancing-level coupling to the reservoir. In addition, An algorithm of dynamic gridding for solving a wellbore flow model is coupled with the General Propose Reservoir Simulator (GPRS), which has the capability to simulate the isothermal black oil reservoir model to obtain detailed information on such important quantities as flow pattern and mixture velocity in any specific location of wellbore. We apply the black oil model to the simulation of several cases on dynamical local mesh refinement isothermally, and compare the results with fixed coarse and fine meshes. The experiments demonstrate that the algorithm can yield accurate results with acceptable computational time.
Open Access
Application and experimental study of cyclic foam stimulation
(RSC (Royal Society of Chemistry) Advances, 2015-08-27) Chen, Zhangxing (John); Zhang, J.; Wu, X.; Han, G.; Wang, J.; Ren, Z.; Zhang, K.
Formation damage is a serious problem in oil and gas industries. Based on common reservoir damage, the conditions and factors resulting in damage were summarized into four categories in this paper. The worldwide advanced technologies applied in reservoir damage treatment are reviewed. For the first time, we propose the concept of injecting nitrogen foam into a formation to treat the damage caused by sand blocking. An application of Cyclic Foam Stimulation is introduced, which enhances productivity significantly. Experimental apparatus for the Cyclic Foam Stimulation was designed, which included a wellbore vessel that could stimulate the effect of sand setting. A reservoir vessel was also designed to supply the foam. Additionally, in order to simulate the formation damage caused by the size and distribution of fine sand, six artificial cores, which were porosity contrastive and sand producing, were prepared based on the technologies of pressure control and PVA membrane wrapping. The experimental results show that the foam has a good discharging effect on sand blockages. Moreover, the effects of the size and distribution of the fine sand on the porosity was studied. It was found that the smaller the size of the grains and the more uniform the grain distribution, the worse the formation porosity. A porosity recovery factor has been defined and the recovery rate of the porosity was also studied. A scientific guide for the application of Cyclic Foam Stimulation can be generated from the studies in this paper.
Open Access
Brittleness and Fracability Evaluation of Unconventional Reservoirs
(2018-05-10) Hu, Yuan; Chen, Zhangxing (John); Huang, Haiping; Wang, Xin; Hejazi, Seyed Hossein; Nouri, Alireza M.
Brittleness and fracability evaluation plays an important role in recovery of unconventional oil and gas; it directly influences the effect of hydraulic fracturing. The definition of brittleness is controversial and the existing analytical/semi-analytical models have no unified theory to support them. Brittleness and fracability evaluation is currently unreliable. Unconventional reservoirs have different confining pressure, pore pressure and temperature. Models that do not consider these influences lack accuracy in the brittleness index (BI) calculation, resulting in failure during hydraulic fracturing. This research is focused on establishing new methods for brittleness and fracability evaluation. First, analytical/semi-analytical models are proposed considering the influence of confining pressure, pore pressure and temperature, respectively. The influence of calcite on rock mechanics parameters and brittleness is compared to quartz and clay. The weight of each parameter in models based on elastic modulus and mineralogy is analyzed. Finally, a numerical method to evaluate rock brittleness in terms of energy is developed. This novel method is applied to evaluate rock brittleness and fracability in more complicated conditions by considering hydro-mechanical (HM) interaction. By defining brittleness in terms of energy, rock brittleness from different sources can be compared. The influence factors ignored by other models of brittleness evaluation: pressure, temperature and rock texture can be addressed at the same time. By combining the analytical method and the numerical method for brittleness and fracability the resulting evaluations are more applicable because they reflect a more realistic unconventional oil and gas reservoirs environment.
Open Access
Capillary forces between two parallel plates connected by a liquid bridge
(Journal of Porous Media, 2015) Chen, Zhangxing (John); Dejam, M.; Hassanzadeh, H.
Liquid flow between porous and nonporous materials plays an important role in many science and engineering applications such as oil recovery from fractured porous media. The capillary continuity between porous matrix blocks via formation of liquid bridges is a key contributor to the gas−oil gravity drainage mechanism in a gas invaded zone of naturally fractured reservoirs, which increases the height of the continuous liquid column in a fractured formation, thereby enhancing the recovery of oil. However, the role of capillary forces information or break-up of liquid bridges between porous matrix blocks remains a controversial topic. In an attempt to improve an understanding of this problem, a force balance is presented for the concave liquid bridges formed between two horizontal parallel plates. The force balance allows development of a simple model that can be used to find a relationship between the net capillary force, contact angle, and liquid bridge volume. Three different regions including: (I) repulsive net capillary force, (II) attractive net capillary force, and (III) nonexistence regions have been identified. Region I is considered as a region of liquid bridge break-up while Region II is considered as a region of liquid bridge formation. The findings improve an understanding of the formation and break-up of the liquid bridges, which is important in oil recovery from naturally fractured reservoirs during a gravity drainage process.
Open Access
Case Study of Expanding Solvent-SAGD Process for Athabasca Oil Sand Reservoirs with Presensce of Lean Zones
(2017) Yu, Yanguo; Chen, Zhangxing (John); Pereira Almao, Pedro R.; Dr. Qingye Lu
Reservoir heterogeneities (i.e., lean zones or shale layers) impact the performance of SAGD (steam assisted gravity drainage) processes. The lean zones, which have a water saturation of more than 50%, have been reported by several oil sands fieldsduring the development of oil sand reservoirs in the Athabasca area in western Canada. They reported that the lean zones severely affected the production of SAGD processes. Therefore, an ES-SAGD (expanding solvent SAGD) process has been introduced into this type of reservoir to improve the production performance. Simulation studies are conducted to investigate the mechanisms of how lean zones influence the two processes by comparing their bottom, middle, and top locations in a reservoir. Moreover, the thickness, location, water saturation of lean zones and reservoir permeability are also investigated to understand the impacts of lean zones further on these processes. A heterogeneous reservoir model, which contains lean zones, is carried out to study the production performance of the SAGD and ES-SAGD processes.
Open Access
Characterization of rock matrix block size distribution, dispersivity, and mass transfer coefficients in fractured porous media
(2013-10-02) Sharifi Haddad, Amin; Abedi, Jalal; Chen, Zhangxing (John); Hassanzadeh, Hassan
Fractured porous media are important structures in petroleum engineering and geohydrology. The accelerating global demand for energy has turned the focus to fractured formations. The fractured porous media are also found in conventional naturally fractured reservoirs and the water supply from karst (carbonate) aquifers. Studying mass transfer processes allows us to explore the complexities and uncertainties encountered with fractured rocks. This dissertation is developing an analytical methodology for the study of mass transfer in fractured reservoirs. The dissertation begins with two cases that demonstrate the importance of the rock matrix block size distribution and dispersivity through a transient mass exchange mechanism between rock matrix blocks and fractures. The first case assumes a medium with no surface adsorption, and the second case includes the surface adsorption variable. One of the main focuses of this work is the characterization of the rock matrix block size distribution in fractured porous media. Seismic surveying, well test analysis, well logging, and geomechanical tools are currently used to characterize this property, based on measurements of different variables. This study explores an innovative method of using solute transport to determine the fracture intensity. This methodology is applied to slab-shaped rock matrix blocks and can easily be extended to other geometries. Another focus of this dissertation is the characterization of dispersivity in field scale studies. Improving our knowledge of dispersivity will enable more accurate mass transfer predictions and advance the study of transport processes. Field tracer tests demonstrated that dispersivity is scale-dependent. Proposed functions for the increasing trend of dispersivity include linear and asymptotic scale-dependence. This study investigated the linear dispersivity trend around the injection wellbore. An analysis of the tracer concentration in a monitoring well was used to characterize the slope of the linear function for different rock geometries. The final part of the study is the development of a lumped mass transfer coefficient between fractures and rock matrix blocks with different geometries. The obtained lumped mass transfer coefficient confirms that the scale of study, dispersivity, and the rate of injection of the fluid into the wellbore are important variables in solute transport in fractured rocks.
Open Access
Chemical Additives and Foam to Enhance SAGD Performance
(2016) Li, Ran; Chen, Zhangxing (John); Song, Hua; Clarke, Matthew
Adding chemical additives with in-situ generation of foam is an approach to enhance SAGD (steam assisted gravity drainage) performance both in terms of oil production and SOR (steam oil ratio). Simulation study tells that, owing to gas mobility control, interfacial tension reduction and emulsification, the steam chamber profile is substantially controlled with a reduced heat loss, and the residual oil saturation drops dramatically. A heterogeneous model based on a Suncor Firebag project is further employed to testify that bubbles are conducive to improve volumetric sweep efficiency by diverting steam into low-permeable area. Simultaneously, foam favors to reduce the influences of top water zone and maintain a bowl-shaped and uniformly-developed steam chamber growth. Afterwards, an analytical method is introduced to further explain the physical mechanisms with a modified finger rising model, which shows that CAFA-SAGD (chemical additives and foam assisted SAGD) owns a lower finger rising velocity with less steam consumption.
Open Access
Chops studies - a modeling and simulation perspective
(2012-08-23) Sun, Jian; Chen, Zhangxing (John)
CHOPS refers to Cold Heavy Oil Production with Sand in Western Canada, with heavy oil and sand produced together. Being different from conventional primary recovery, wormhole propagation and foamy oil flow are observed to make CHOPS achieve considerable production. Differences between the conventional primary depletion and cold heavy oil production are discussed in terms of their drainage mechanisms, model formulation and modeling approaches. The goal of this study is to investigate the modeling techniques on wormhole propagation and foamy oil flow as well as their effects in simulation. This study demonstrates two kinds of wormhole modeling approaches: Modeling wormholes as high permeability channels resulting from the experimental observations in which new variables are set up to model the enhanced permeability channels and modeling wormholes as well segments resulting from the extension of wormholes that build more flow paths like wells. Also, a reaction - based pseudo bubble point model is applied in the modeling of foamy oil flow. The heavy oil solution gas drive is divided into several stages in order to capture the transfers between various gas partitions. The above different modeling approaches are implemented into a General Purpose Research Simulator. Numerical studies are conducted for pressure profiles, sand production characteristics in wormhole propagation, Gas-Oil Ratios (GOR) and Recovery Factors (RF) for foamy oil flow. The simulation results show the rationality of the proposed wormhole modeling approaches and indicate that pressure decline and a permeability increase rate are two main factors influencing CHOPS performance.
Open Access
Closed-Loop Reservoir Management for Thermal Recovery Processes
(2015-10-05) Shaker, Wisam; Chen, Zhangxing (John); Walker, Greg
The combination of model-based optimization and simulation into a single workflow forms the main components of a powerful tool called Closed-Loop Reservoir Management (CLRM). Real-time reservoir management has been applied mostly for water flood application and there is lack of information on application of CLRM for a thermal recovery process. In this research, a novel methodology has been developed to value surveillance prior to acquisition for a Steam Assisted Gravity Drainage (SAGD) process. The workflow evaluates the values of a rate, pressure and temperature surveillance represented by their measurements in injectors, producers and observation wells in a SAGD project. A 2D SAGD reservoir has been used to test the validity of the developed methodologies. The results rejected the null hypothesis proposed and show that these three types of surveillance are uncorrelated, and in the test have reduced the uncertainty range of the future reservoir outcomes by 84%. The power and utility of the developed approach have been expanded to generate a second workflow. The testing workflow represents a new application of the CLRM on thermal cases to test the type of surveillance, the number and locations of the required observation wells and the period of history matching in a 3D SAGD reservoir with the intent of discarding models that would satisfy history at the production well and would be poor predictors. The workflow tests how would the future reservoir outcomes that are controlled by observation wells capture the growth of a steam chamber during the SAGD process. A third comprehensive workflow has been developed to combine an Ensemble Kalman Filter (EnKF) algorithm and simulation with a thermal option to data assimilates of a 2D SAGD reservoir permeability. It is proposed to use the updated reservoir permeability as an input for the reservoir simulation runs from initial time to eliminate any inconsistency between the updated reservoir permeability and the dynamic reservoir properties. The frequency of the updating has been investigated and the outcomes show that incorporating more production data at the first year of production has reduced the uncertainty range of future cumulative oil production in the range of 50-70%.
Open Access
CO2 Sequestration in UCG
(2013-09-24) Adim Naghouni, Forough; Chen, Zhangxing (John)
The most commonly applied UCG designs are Linked Vertical Wells (LVW) and Controlled Retracting Injection Point (CRIP). In the CRIP process, the production well is drilled vertically, and the injector is drilled horizontally close enough to the producer to have considerable flow connection. When the linking channel is established, the coal is ignited at the end of the horizontal well and a cavity is initiated. A main problem with UCG in contrast to other fossil fuel technologies is the higher CO2 production which may lead to a global warming potential. Potential solutions for this problem may be compression and injection of the recovered CO2 into an exhausted UCG reactor or into a seam in which the permeability has been enhanced by the relaxation of the strata overlying the reactor for the purposes of CO2 sequestration.
Open Access
Cold, Hot and Steam Assistant Solvent Injection Processes for Heavy Oil Recovery
(2018-06-26) Wang, Qiong; Chen, Zhangxing (John); Abedi, Jalal; Pereira Almao, Pedro R.
Solvent-based processes such as vapor extraction (VAPEX) can be another technology that has potential to enhance heavy oil recovery in a more cost-efficient and environment friendly way. Extensive experimental and simulation studies have been conducted to evaluate VAPEX. However, theoretical modeling has not gained much progress in the past two decades. This thesis aims at adopting a series of mathematical models for a new theoretical analysis of comprehensively evaluating solvent-based recovery processes and also attempts to develop a new process to enhance production. This thesis first develops a comprehensive theoretical analysis method for VAPEX, which considers all the major recovery mechanisms such as dynamic mass transfer, gravity drainage, multiphase flow, and boundary movement in the model. Both constant and variable diffusivity have been studied in this model, and the latter justified in the progressive change of properties such as viscosity in the media within the diffusion layer. A hot solvent injection process takes advantages of both thermal recovery processes (quick heat conduction and large viscosity reduction) and solvent-based processes (lower energy consumption and less green-house gas emission). This thesis then develops a transient mass transfer model to analyze the cold heavy oil–hot solvent mixing process during a hot solvent injection process. This mass transfer model is then incorporated into the VAPEX model to evaluate the performance of a hot solvent injection process. Key indicators such as oil production profile, injection pressure, injection temperature, solvent oil ratio, etc. have been studied to find out a quantitatively correlation. A new hybrid process, SAVE, is proposed to enhance heavy oil recovery. In this process, a short-slug steam and a long-slug solvent are alternately injected to extract heavy oil. Simulation results show that the cumulative steam-oil ratio of SAVE is 37.26% of that of SAGD. In comparison with VAPEX, SAVE produces oil 8.4 times faster than VAPEX and its cumulative solvent-oil ratio of SAVE is only 26% of that of VAPEX. SAVE performs relatively better in thinner formations than in thicker ones.
Open Access
Comparative Simulation Study and Economic Analysis of Thermal Recovery Processes in Athabasca Reservoirs
(2018-04-30) Iyogun, Christopher Omokhowa; Chen, Zhangxing (John); Chen, Shengnan; Maini, B. B.
Simulation studies of three thermal recovery processes used in Athabasca reservoirs have been carried out for a 10-year production period. The recovery processes studied are Steam-Assisted Gravity Drainage (SAGD), Fast-SAGD, and Expanding Solvent-SAGD (ES-SAGD). Normal pentane (n-C5) was the solvent of choice used in ES-SAGD simulations with its molar concentration varied from 2% to 5.9%. The main objective of this study is to conduct an economic analysis of the three recovery processes with the goal of determining the most economically viable process. The economic indicator that will be assessed to ascertain the most viable recovery process is their Net Present Value (NPV.) 2D simulation studies based on homogeneous Athabasca reservoirs have been performed. Results obtained show that of the three recovery processes, Fast-SAGD had the lowest cumulative oil produced, followed by SAGD and ES-SAGD, the highest. The cumulative oil produced also increased with increasing molar concentration of n-C5. Furthermore, it was shown that as expected, the CSOR of ES-SAGD was the lowest of them while that of Fast-SAGD was the highest. The CSOR of the ES-SAGD processes reduced as the concentration of the n-C5 increased. The economic analysis showed that of the three recovery processes, ES-SAGD is the most economically viable process. Furthermore, the effect of solvent on the viability of ES-SAGD over the other recovery processes is dependent on the price regime of pentane. In this analysis, two extreme price regimes were chosen and the result showed that for a low price regime, varying the molar ratios of n-C5 had a significant effect on the NPV up to a point before its effect diminishes. In fact, increasing the molar concentration of n-C5 from 2% to 3.76% significantly increased the NPV while further increasing it from 3.76% to 4% and thereafter to 5.9% had no noticeable effect. However, it seems that increasing it from 3.76% to 5.9% had a diminishing effect especially after the 3-year period. Nevertheless, the significant NPV improvement ES-SAGD has over SAGD and Fast-SAGD diminishes once the price regime of pentane is more than 3 times that of oil. In fact, this high price regime showed that 5.9% molar concentration of n-C5 is no longer more viable than the SAGD counterpart. There is still some benefit up till about 4% molar concentration of n-C5 but this benefit is greatly diminished. In conclusion, ES-SAGD has been shown to be the best recovery process for Athabasca reservoirs based on economics but further research is needed to evaluate the molar concentration that will provide the most economic benefit for a real Athabasca reservoir.
Open Access
Coupled Studies of Shale Reservoirs Characterization and Simulation
(2018-04-19) Yang, Sheng; Chen, Zhangxing (John); Azaiez, Jalel; Dong, Mingzhe; Moore, Robert Gordon; Huang, Haiping; Harris, Nicholas B.
Coupled studies of characterization and simulation of shale reservoirs are documented in this thesis. The characterization of shale reservoirs includes the description of natural fractures, rock brittleness derived from dipole sonic logs, brittle mineral composition calculated from Elemental Capture Spectroscopy (ECS) logs, and hardness measured on cores. Then a rock fracability index model, based on these rock properties, is generated to constrain stimulated reservoir volumes generated by microseismic events. An enhanced Dubinin-Astakhov (DA) model is also proposed to model methane-shale adsorption under supercritical conditions. Based on reservoir characterization, the Marcellus shale gas and Eagle Ford shale condensate reservoirs simulation models are developed and validated by field data. Effects of uneven proppant distribution, geomechanics, single-component adsorption and matrix permeability are evaluated in the shale gas reservoirs. In terms of the condensate reservoir, roles of multicomponent adsorption and geomechanics are investigated during primary recovery and CO2 enhanced recovery.
Open Access
Cyclic Solvent Injection (CSI) and Cyclic In-situ Upgrading Technology (CISUT) in Tight Oil Reservoirs
(2020-09-04) Assef, Yasaman; Pereira-Almao, Pedro; Kantzas, Apostolos; Maini, Brij; Jeje, Ayodeji; Chen, Zhangxing (John); Meyer, Rudy; Alvarado, Vladimir
Due to increasing energy demand and fast depletion of conventional oil resources, a strong interest exists in unconventional oil production; namely, light oil from shales and extra-heavy oil from naturally fractured carbonates. The heterogeneous nature of these class of reservoirs, along with their low matrix permeability and porosity, have been known as major constraints for implementing conventional enhanced oil recovery (EOR) techniques. Huff and puff mode or cyclic injection has been recognized as one of the promising recovery techniques in which the injection and production occur in a single well. In this dissertation, we present results from comprehensive simulation of cyclic CO2 injection(CCI) in Bakken ultra-tight oil reservoir and both experimental and numerical modeling of cyclic gas injection in Ayatsil extra-heavy oil carbonate. For the first time, application of extra heavy oil in situ upgrading using ultra dispersed catalysts is investigated in a cyclic mode. Numerical simulations have been paired with the experimental design method in order to identify the parameters that could control oil recovery, CO2 utilization, and CO2 retention factors of the cyclic CO2-EOR process. Impacts of rock heterogeneity and dependency of relative permeability on saturation history during CCI in various operational constraints, are studied. Through conducting sets of huff’n’puff experiments, effective molecular-diffusion coefficient of gases in Ayatsil oil is determined based on pressure-decay theory for CO2-oil, ethane-oil, CO2-C2-oil and mixture CO2-C2-C3-oil at constant temperature. In extra-heavy oil, hydrogen deficiency and high carbon content, sulfur, and metals necessitate upgrading procedure to obtain proper feedstock for a normal refining. In this study, the feasibility of nano-catalyst in-situ upgrading technology (ISUT) in a cyclic mode is investigated for carbonate saturated with Ayatsil oil. In setup, hydrogen and catalyst dispersed in vacuum residue are co-injected to be transferred through the fracture medium. After the catalysts are located in the matrix oil in place, the catalytic reactions and hydro-conversion process take place. Useful analytical methods are utilized to prove the effectiveness of the proposed cyclic in-situ upgrading in heavy oil. Our numerical simulations are capable of regenerating our laboratory results by capturing combination of hydroprocessing reactions, heat transfer and mass transfer phenomena.