bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Integrated Approach to Building History-Matched Geomodels to Understand Complex Long Lake Oil Sands Reservoirs, Part 2: Simulation
Authors: Feizabadi Seyed Ali , Zhang Xingquan Kevin , Yang Peter 
Published: June 2014

Abstract
Simulation is one of the most important and powerful reservoir engineering tools for understanding reservoir performance, devising operating strategies, and solving production problems. Simple homogeneous models are suitable for understanding basic reservoir engineering parameters and for simple sensitivity analyses. However in real reservoirs with heterogeneities such as at Nexen Long Lake, a comprehensive geomodel which includes all the available geology and geophysics knowledge is necessary in order to extract the greatest value from the simulation efforts.
A geomodel is representative of the real reservoir if simulation of the geomodel is able to reproduce the production history of the reservoir (history matching). For a typical SAGD pad, the parameters to be matched include the injection and production rates, downhole injection pressures, and pressure and temperature of observation wells.
Based on our experience, for this process to be effective and reasonably timely a team consisting of the geologist, geophysicist, geomodeler, production and reservoir / simulation engineer must work interactively and in an iterative, "trial and error" fashion.
The geomodelling part is presented in Part 1(10), of this paper and in Part 2 the simulation results are reviewed. The simulation process can be divided into three main parts - history matching, sensitivity analysis and forecasting. Once the history matching part is done, the geomodel is ready to be used for the other two parts.
High water saturation zones, also referred to as lean zones and top water, play an important role in different stages of a SAGD project. A detailed strategy is necessary to deal with them and to optimize the production. Simulation results show that one needs to be able to increase the total fluid rate and solve the sub-cool limitations at the time of contact with these lean zones.
The STARS thermal simulator from Computer Modeling Group (CMG) was used to do all the reservoir simulations in this paper.
Modeling of Multiphase Behavior for Water/n-Alkane Mixtures by Use of the Peng-Robinson EOS
Authors: Venkatramani Arun Venkat , Okuno Ryosuke 
Published: June 2014

Abstract
Experimental results in the literature show that the water solubility in the oleic (L) phase can be high at reservoir conditions in thermal oil recovery processes; e.g., 24 mol% in the water/n-eicosane binary system at 41 bars and 523 K. It becomes even more significant as the L phase becomes more aromatic, which is the case with heavy oil and bitumen. Efficient and accurate representation of multiphase behavior, which consists of the L, vapor (V), and aqueous (W) phases, is crucial in reliable numerical simulation of steam injection processes. This research presents multiphase behavior predictions for water/n-alkane mixtures by use of the Peng-Robinson equation of state (PR EOS) with the van der Waals mixing rules.
Binary interaction parameters (BIPs) are first optimized for water with n-alkanes in terms of three-phase curves including upper critical endpoints (UCEPs), where the V phase and the less dense liquid phase merge in the presence of the denser liquid phase. A new correlation is then developed on the basis of the optimized BIP values. Thermodynamic predictions from the PR EOS with the new BIP correlation are given for various mixtures and compared with experimental data available in the literature.
Results show that the PR EOS with the BIP correlation yields reasonable predictions for multiphase behavior of water/n-alkane mixtures. It gives the transition of binary phase behavior between types IIIa and IIIb that is consistent with experimental results. It also can reproduce asymptotic behavior of three-phase curves and the water solubilities in the L phase (xwL) that has been observed as n-alkane becomes heavier. When applied to water-containing reservoir fluids, the PR EOS with the BIP correlation results in a systematic underprediction of xwL. This is expected considering that reservoir oil consists of various types of hydrocarbons and that the affinity towards water is lowest for n-alkanes and highest for aromatics. Accurate xwL predictions can be obtained by systematically reducing the BIP values from the correlation. The correlation developed may serve as the upper limit of BIPs for water with pseudo components that are required for characterizing water-containing reservoir fluids.
Modeling Effect of Permeability Heterogeneities on SAGD Performance Using Improved Upscaling Schemes
Authors: Kumar D.. , Murugesu M.. , Srinivasan S.. 
Published: June 2014

Abstract
Fully heterogeneous three-dimensional SAGD simulation models are computationally expensive to evaluate, necessitating the need for simpler models that can capture the overall physics of the process while reducing computation time. This paper sheds some insights into the effect of permeability heterogeneity on SAGD performance, and presents both a physics-based upscaling technique that considers the unique geometry of the steam-plume during the SAGD process, as well as a statistical upscaling scheme based on variable selection and multivariate non-linear regression.
Full physics, two-dimensional SAGD simulations were performed using several stochastic shale models representing different proportions. Subsequently, the vertical variability in the models was averaged using a flow-based upscaling technique to obtain an effective anisotropic ratio. The performance of the upscaled models was assessed using full physics numerical simulation. It was observed that the upscaled anisotropic models gave different results compared to the fully heterogeneous models. The discrepancy between the heterogeneous and anisotropic models is largely due to upscaling. Two approaches were formulated to address this. The first approach iteratively adjusts the anisotropic permeability of the 2D model until a match to the 3D heterogeneous model was achieved. Then a non-linear regression model between the heterogeneous model parameters and the history-matched anisotropic permeability was formulated. In the second approach, an upscaling method considering the flux due to convergent flow towards a line sink was developed.
A key result presented in this paper is that heterogeneity plays a significant role in SAGD performance. Factors such as shale correlation length and proportion affect both the initial steam rise and the lateral spread of the chamber. Traditional upscaling techniques assuming power averages or flow-based assuming uniform flow over a plane are inadequate for approximating heterogeneous models. Statistical schemes such as the one presented in this paper perform much better in capturing the recovery characteristics of the SAGD process in heterogeneous media. Considerations such as optimum well pair spacing and optimal steam-oil ratio for maximizing bitumen recovery require quick evaluation of multiple scenarios and that may be possible using the approach presented in the paper.
Interfacial Rheology of Heavy Oil-Aqueous Systems at Elevated Temperatures and Pressures: Effect of Diluents
Authors: Phan Jenny , Balsamo Vittoria , Nguyen Duy , Maharajh Edward , Champion Nalco 
Published: June 2014

Abstract
In SAGD (Steam Assisted Gravity Drainage) operations the produced fluids are complex water-in-oil-in-water (W/O/W) emulsions. A diluent is often added to reduce the density and viscosity of the heavy crude oil. However, the quality and composition of the diluents may in some cases increase emulsion stability and cause the dehydration of the oil to be more difficult as there are more surface-active agents added to the oil coming from the diluent streams. To simulate temperature and pressure conditions during SAGD operations, this work studied the effect of three diluents on interfacial rheology of a Canadian heavy oil and synthetic brine at 120°C and 130 psi and then correlated with emulsion stability and oil dehydration. When compared to 25°C, all three diluents exhibited higher higher compressibility at 120°C, while the initial interfacial tension, "phase change" area ratio (area ratio at which the phase change from high compressibility region to low compressibility region), and crumpling ratio (ratio of the compressed surface area to the original area at which the interface starts to collapse) exhibited a more complex behavior. The higher interfacial tension and higher compressibility were correlated with the lower emulsion stability at increasing pressure and temperature in the absence of treating chemicals. Increasing ageing of the film from 10 minutes to 1 hour at 120°C had a similar effect on the three diluents, suggesting the formation of a more elastic film as asphaltenes start to cross-link on the interface. The effect of demulsifiers (emulsion breakers-EB and reverse emulsion breakers-REB) on interfacial was also investigated at RT and 90°C. Demulsifiers that produced the minimum interfacial tension (IFT) with changing concentrations demonstrated to be the best demulsifiers in the bottle tests. A synergistic effect in reducing IFT was found when EB and REB when combined.
Application of Intelligent Well Technology to a SAGD Producer: Firebag Field Trial
Authors: Stahl Richard M. , Smith Jennifer D. , Hobbs Scott , Clarke Colin M. 
Published: June 2014

Abstract
Even temperature conformance along the length of the horizontal well is key to maximizing Steam Assisted Gravity Drainage (SAGD) production rates. When temperature logs are run in SAGD producers, temperature variations of greater than 50°C between the hottest and coldest spots are commonly observed. We theorize that this temperature distribution is related to an inflow distribution, and that production rates could be improved if this temperature variance was narrowed.
It is difficult to influence conformance with traditional SAGD producer well design. Flow areas are large, and liquid velocities are low, resulting in small frictional pressure losses. It is not possible to impose a materially different drawdown on hot and cold spots along the horizontal with typical well completion methods.
A field trial is ongoing at the Firebag project in which a production well is equipped with intelligent completion technology. The test well's horizontal liner section is split into four hydraulically isolated zones, with each zone having the ability to provide flow or isolation from the reservoir. The well completion is equipped with optical pressure and temperature (P/T) gauges and distributed temperature sensing (DTS) technology which monitors each segment's performance during operations. The capability to independently and immediately manipulate each segment's production inflow will provide the operator the ability to evaluate the influence of an intelligent completion design on a well's conformance and ultimate oil recovery.
The Measurement of Connate Water Chlorides Concentration and Its Effect on Bottom Water Coning Analysis in SAGD for Optimization
Authors: Masih Shahbaz , Bennett Barry , Savage Mark 
Published: June 2014

Abstract
Bottom water coning has a detrimental impact on the performance of steam assisted gravity drainage (SAGD) causing reduced oil mobility around the producer. It, also, leads to higher steam to oil ratio (SOR). Produced water chlorides concentration can be used as an indication and quantification tool for bottom water coning analysis. The chlorides material balance for bottom water coning analysis depends upon connate water saturation and the concentrations of chlorides in connate water, bottom water and produced water along with the water cut of produced emulsion. Most oil sands are water wet but wettability changes with high steam temperatures and almost all the connate water is drained because of steaming. The safe produced water chlorides concentration, at which no bottom water is produced, depends mainly upon connate water saturation and its chlorides concentration besides water cut and oil saturation. Therefore, careful sampling and laboratory procedures for connate water chlorides measurement is vital in bottom water coning analysis.
The mechanical extraction device (referred to as the plunger) was developed mainly to facilitate the recovery of heavy oil and bitumen samples from oil sands cores. In this study, the plunger technology is employed in order to recover water samples to enable measure connate water chlorides PPM (concentration in parts per million). The measured connate water chlorides are also corrected for drilling fluid invasion. A new material balance for bottom water coning analysis is established based on different connate water and bottom water chlorides concentrations and drainage patterns of connate water and oil saturations. The new material balance is used to determine the safe chlorides concentration and applied to bottom water coning analysis in the field application at Leismer SAGD project.
Since, the earlier study assumed the same chlorides concentrations of bottom water and connate water, the new measurement technique of chlorides concentration of connate water has led to a better material balance calculation for bottom water coning and data analysis. The new material balance has led to a lower safe chlorides limit. It has, also, helped better optimization of steam chamber pressure and steam injection strategy to avoid negative impacts of bottom water conning to enhance oil production and lower SOR at Leismer.
Impact of Fractures Characterization, Wettability and Hysteresis on Thermal Recovery Processes in Carbonate Naturally Fractured Reservoirs
Authors: Ghedan Shawket G. , Kumar Anjani 
Published: June 2014

Abstract
Combination of complex sedimentation environment and carbonates' diagenetic alterations render carbonate reservoirs to be very heterogeneous and often naturally fractured. Heavy oil trapped in carbonate reservoirs worldwide is estimated to be over 255 billion cubic meters. The drastic differences in flow and storage capacity of the fracture and matrix networks trigger the need for larger volumes of steam to be injected to produce one cubic meter of heavy oil production, making the application of thermal recovery processes in these reservoirs to be more economically challenging and highly energy intensive.
Recovery of heavy oil from naturally fractured reservoirs is weakly controlled by viscous forces and mostly controlled by capillary and gravity forces, in addition to convection and conduction heat transfer. This makes proper representation of fracture and matrix characteristics to be of paramount importance to the reliability of modeling thermal recovery processes.
This paper discusses the effect of variable fracture characteristics including fracture typing, spacing, and apertures on the performance of dual permeability models under different thermal recovery processes. Further, the paper demonstrates the necessity to characterize partially mineralized fractures and shows its effect on thermal conductivity from fractures to matrix blocks.
The effect of wettability on the recovery process is also discussed. Oil recovery in fractured reservoirs is highly influenced by imbibition process which is most effective under strong water wetness. The paper addresses the performance under water, oil and mixed wettability conditions. Furthermore, the paper shows that proper representation of capillary pressure hysteresis could cause considerable change in oil recovery performance. The modeling work in this paper helps to curtail any extra optimism that may originate from wrongly characterized dual permeability models. Finally, and in case reservoir characteristics are not well determined then forecasting based on uncertainties of reservoir characteristics should give operators a way to estimate the risk involved in the exploitation process of the carbonate resources.
Pentane as a Potential Candidate for ES-SAGD and Hybrid Processes: Its Phase Behaviour with Bitumen
Authors: Nourozieh Hossein , Kariznovi Mohammad , Abedi Jalal 
Published: June 2014

Abstract
Steam-assisted gravity drainage (SAGD) is a promising method for producing oil sand in Alberta; however, it has been suffering from high energy and water consumption and significant greenhouse gas (GHG) emissions. Solvent-based processes represent an alternative to steam-based processes but they have their own drawbacks. The main problem with solvent-based processes is a relatively low production rate because they rely on diffusion and dispersion mechanisms, which are very slow processes. To overcome the limitations of steam and solvent processes, hybrid processes have been proposed in which steam and solvent are co-injected. As a result, several recovery techniques, such as expanding-solvent SAGD (ES-SAGD) and steam-alternating solvent (SAS), were proposed and patented. However, there is a fundamental lack of basic data and mechanistic knowledge relevant to solvent/heat-assisted-recovery processes. Even the most fundamental experimental data, such as the solubility of commonly used solvents in bitumen, is not available. The quantitative effects of solvent on bitumen viscosity and density, and phase behaviour are also not well understood.
Pentane as a potential additive to steam-based processes has saturation pressure close to steam at in situ thermal process; thus, pentane and its mixtures with other hydrocarbons can be considered for bitumen and heavy oil recovery. In this study, the phase behavior of pentane / Athabasca bitumen mixtures was experimentally studied. The measurements include the properties of phases such as solvent solubility, number of phases, and composition, density, and viscosity of each phase as well as the possibility of asphaltene precipitation. The experiments were conducted over wide range of temperatures (23–200°C) and at pressures (1–10 MPa) which cover single liquid, liquid-liquid and vapor-liquid equilibrium conditions.
The results showed that the solubility of pentane in bitumen was relatively high even at high temperatures leading to significant density and viscosity reductions. The asphaltene was separated as a second liquid phase rather than a solid phase, and there was a transition zone between single liquid and liquid-liquid regions in which the asphaltene was instable in the system. A significant reduction in density and viscosity of bitumen was observed with the dissolution of pentane over studied temperature condition.
Combining Process Safety Data with Environmental Risk Analysis to Prioritise Capital Expenditure on Environmental Improvement Programmes
Authors: Gibbons S.. , Quinn D.. , Pollok D.. 
Published: June 2014

Abstract
There has been an increase in the awareness of environmental consequences of major accidents, particularly as a result of the Buncefield fire (UK Hertfordshire Oil Storage Terminal) and the offshore Deepwater Horizon oil spill, and the connection between failures in process safety systems and environmental damage. Whilst there is an obvious link in principle between incidents and environmental consequence, there has been relatively limited work to prioritise planning and preventative expenditure reflecting environmental, as well as safety, outcomes. This paper presents a process whereby integration of process safety data and environmental fate and transport modelling can be used by oil & gas operators to understand and prioritise actions to reduce and mitigate potential environmental risks and to use an understanding of these as the basis for integrated safety planning and management.
In addition to risk ranking major accident events and their consequences, the approach can also be used to help inform emergency planning and the preparedness of operators. One example application of the approach is the use of modelling techniques to analyse the flow routes of released products from secondary containment, factoring-in the influence of man-made structures and drainage infrastructure as well as the fate and transport of material in the environment. Modelled outputs can help identify where improvements in containment systems may be beneficial in reducing risk and in informing emergency response. This paper provides a case study to illustrate how a risk based approach has been applied to enable an agreement with the regulatory authority on an appropriate scope of upgrades to major accident prevention protection measures for environmental protection.
The approach is tiered, to enable an appropriate degree of assessment commensurate with the level of risk; relatively low frequency events are not considered further, but are documented. Removal of those unlikely events through a process of compartmentalisation of a site provides a transparent method by which events which could generate the greatest impact on the environment may be identified. The key conclusion is that a detailed assessment of environmental risk can identify the most appropriate areas of a facility for environmental improvement, and conversely provide a defensible, risk-based rationale significant saving in capital expenditure on programmes which may ultimately serve little benefit in terms of protecting the environment.
The approach outlined has significance across the oil & gas industry as it enables closer integration of process safety and environmental consequence assessments and provides oil & gas operators with a managed approach to making investment decisions which are likely to have the greatest net safety and environmental benefit.
Application of sustainable remediation principles to upstream oil and gas projects opportunities and challenges
Authors: Thomas A. O. 
Published: June 2014

Abstract
Sustainable remediation has been defined as ‘the practice of demonstrating, in terms of environmental, economic and social indicators, that the benefit of undertaking remediation is greater than its impact and that the optimum remediation solution is selected through the use of a balanced decision-making process’. Sustainable remediation has emerged as a significant area of interest for the management of contaminated land and water for regulators, industry and practitioners in Western Europe, the USA and Asia Pacific. It seems likely that sustainable remediation will develop into a key policy and practice consideration in future years. The application of sustainable remediation principles to the management of upstream oil and gas legacy related impacts have not been explored to date.
This paper attempts to define sustainable remediation in the context of onshore upstream O&G operations, demonstrate how sustainable remediation principles could be applied within the context of existing best practice guidance and explore the opportunities that sustainable remediation may bring as well as the barriers that may exist to its implementation.
The primary conclusion is that where existing regulations are absent or incomplete sustainable remediation can offer an improved framework for the management of contaminated land issues that results in solutions that are protective of human health and the environment, inclusive of the views of local stakeholders and is transparent and robust. Where regulations do exist then sustainability should be considered in the context of what is practically achievable. Sustainable remediation can be a driver for improved engagement with stakeholders that can result in locally acceptable solutions that maximize the benefits to local society as well as acting as a catalyst to drive innovative technical solutions. It is recommended that the application of sustainable remediation to upstream oil and gas sites should be examined more closely with a view to developing sector specific guidance and best management practices that promote the incorporation of sustainability and that the procedures for management of contaminated land associated with upstream operations draw on best practices from other parts of the oil and gas sector and contaminated land management as a whole.