bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiphase Equilibrium Calculation Using Reduced Variables
Authors: Nichita Dan Vladimir , Broseta Daniel , de Hemptinne Jean-Charles 
Published: December 2007

Abstract
A new method for multiphase equilibrium calculations with cubic equations of state (EOS) has been developed. The minimum of the Gibbs free energy and of the tangent plane distance function should be found in a space with a significantly reduced number of dimensions. The number of independent variables for phase equilibrium calculations does not depend on the number of components in the mixture and non-zero binary interaction coefficients (BIC) are taken into account by our approach.
Phase splitting calculations consists in successive substitution (SSI), followed by Minimum Variable Newton-Raphson (MVNR) iterations. The tangent plane distance criterion is used for testing the thermodynamic stability. The nonlinear system of equations for phase stability is solved by a globally-convergent Newton method.
The calculation of multiphase equilibrium is organized in a stepwise manner, combining phase stability analysis by minimization of the tangent plane distance (TPD) function with phase splitting calculations. The phase distribution for three-phase calculation is found by the constrained minimization of a convex smooth function.
The robustness of the proposed method is tested for several systems of interest in reservoir and production engineering. The reduction in computer time as compared to conventional methods is all the more important as the number of the components is greater. The most important savings in computer time are expected for mixtures with many components and relatively few BIC’s.
The proposed method using reduced variables represents a new, efficient, and reliable tool for the many practical situations when multiphase equilibria calculations are needed. To the best of our knowledge, it is the first implementation of the reduced variables to multiphase equilibrium calculation.
Three-phase Compositional Streamline Simulation and Its Application to WAG
Authors: Yan Wei , Michelsen Michael L. , Stenby Erling H. , Berenblyum Roman A. , Shapiro Alexander A. 
Published: December 2007

Abstract
This paper presents the development of a three-dimensional (3D), three-phase compositional reservoir simulator based on the streamline method and its application to the simulation of water-alternating-gas (WAG) processes. The three-phase compositional streamline simulator has been developed by integrating a one-dimensional (1D) three-phase compositional solver into the 3DSL streamline simulator.
2D and 3D simulations of WAG processes have been performed using the developed simulator. Comparison with the commercial finite difference simulator Eclipse 300 (E300) has also been made. The results from the two simulators are generally in good agreement while the streamline simulator is much faster than E300 and the speed-up factor increases with the simulation size.
This study further extends the application area of the streamline method and shows that the streamline technique can be used successfully for displacement processes with complex physics like that encountered in a WAG process.
Analytical Model for 1-D Gas Flooding: Splitting between Hydrodynamics and Thermodynamics
Authors: P. Pires, A. , G. Bedrikovetsky, P. , A. Shapiro, A. 
Published: December 2007

Abstract
The compositional model for two-phase multicomponent flow is discussed with applications to gas based IOR processes. Analytical models for 1-D displacement of oil by gas have been developed during last 15 years. It was observed from semi-analytical and numerical experiments that several thermodynamic features of the process (compositional path on phase diagram, MMP, etc.) are independent of transport properties. In this paper two flow potentials are introduced; being used as new independent variables they split the compositional (n-1)*(n-1) model for n-component flow into a thermodynamics auxiliary (n-2)*(n-2) system and one transport equation. Explicit projection and lifting procedures are derived. The new technique developed permits splitting for both self-similar continuous injection problems and non-self-similar slug injection problems. The "concentration" part of compositional model solution, including MMP, is independent of transport properties.
Modeling Fluid Flow Through Single Fractures Using Experimental, Stochastic and Simulation Approaches
Authors: Dicman Alfred , Putra Erwinsyah , Schechter David Stuart 
Published: December 2007

Abstract
A fracture is usually assumed as a set of smooth parallel plates separated by a constant width. However, the flow characteristics of an actual fracture surface would be quite different, affected by tortuosity and the impact of surface roughness. Though several researchers have discussed the effect of friction on flow, their efforts lack corroboration from experimental data and have not converged to form a unified methodology for studying flow on a rough fracture surface.
In this study, we have shown an integrated methodology, involving experiments, stochastics and numerical simulations that incorporate the fracture roughness and the friction factor, to describe flow on a rough fracture surface. Laboratory experiments were performed to support the study and the flow contributions from the matrix and the fracture were matched through modified cubic law. Observations suggest that the fracture apertures need to be distributed to accurately model the experimental results.
The methodology successfully modeled fractured core experiments, which were earlier not possible through parallel plate approach. A gravity drainage experiment using an X-ray CT scan of a fractured core has also validated the methodology.
Streamline Simulation of Water Injection in Naturally Fractured Reservoirs
Authors: Al-Huthali Ahmed H. , Datta-Gupta Akhil 
Published: December 2007

ABSTRACTUntil recently1,2 streamline simulators were limited to single-porosity systems and not suitable for modeling fluid flow and transport in naturally fractured reservoirs. Describing fluid transport in naturally fractured reservoirs entails additional challenge because of the complicated physics arising from matrix-fracture interactions. In this paper the streamline-based simulation is generalized to describe fluid transport in naturally fractured reservoirs through a dual-media approach. The fractures and matrix are treated as separate continua that are connected through a transfer function, as in conventional finite difference simulators for modeling fractured systems. The transfer functions that describe fluid exchange between the fracture and matrix system can be implemented easily within the framework of the current single-porosity streamline models. In particular, the streamline time of flight concept is utilized to develop a general dual porosity dual permeability system of equations for water injection in naturally fractured reservoirs. We solve the saturations equations using an operator splitting approach that involves ‘convection’ along streamline followed ‘matrix-fracture’ exchange calculations on the grid. Our formulation reduces to the commonly used dual porosity model when the flow in the matrix is considered negligible.2We have accounted for the matrix-fracture interactions using two different transfer functions: the conventional transfer function (CTF) and an empirical transfer function (ETF). The ETF allows for analytical solution of the saturation equation for dual porosity systems and is used to validate the numerical implementation. We also compare our results with a commercial finite-difference simulator for waterflooding in five spot and nine-spot patterns. For both dual porosity and dual permeability formulation, the streamline approach shows close agreement in terms of recovery histories and saturation profiles with a marked reduction in numerical dispersion and grid orientation effects. An examination of the scaling behavior of the computation time indicates that the streamline approach is likely to result in significant savings for large-scale field applications.
Integrating Dynamic Data in Reservoir Models Using a Parallel Computational Approach
Authors: Srinivasan Sanjay , Bryant Steven 
Published: December 2007

Abstract
Conditioning reservoir models to dynamic data is challenging due to the non-linear relationship between the measured flow response data and the model parameters (porosity, permeability etc.). The focus of this paper is to present a methodology for efficiently integrating dynamic production data into reservoir models. In contrast to other methods for production data integration, the proposed methodology attempts to quantify the information in production data pertaining to reservoir heterogeneity in a probabilistic manner. The conditional probability representing the uncertainty in permeability at a location is iteratively updated to account for the additional information contained in the dynamic response data. A localized perturbation procedure is also presented to account for multiple flow regions within the reservoir. The proposed methodology is demonstrated on a realistic case example. The methodology for implementing the proposed algorithm on parallel cpu’s is presented. The computational synergies realized through domain decomposition flow simulation are likely to result in significant cpu savings.
Numerical Simulation of Water Injection in Disconnected and Connected Fractured Media Using Jacobian-free Fully Implicit Control Volume Method
Authors: Monteagudo J. E. P. , Firoozabadi A. 
Published: December 2007

Abstract
In this work we present an algorithm for water injection in 2D and 3D connected and discrete fractured media using a fully implicit approach for the control-volume method. The crossflow equilibrium concept (that is, the discrete fracture approach) is used to reduce the fracture dimension by one. A congruent mathematical formulation is provided for the discrete fracture approach, establishing a relationship between the matrix and fracture main variables following the physics of two-phase flow at the matrix-fracture interface. The system of partial differential equations is discretized within the discrete-fracture framework using the control-volume method in a fully-implicit formulation. The resulting system of non-linear equations is solved with a Jacobian-free Newton-Krylov solver. In this solver, there is no need to assemble the Jacobian matrix of the non-linear system of equations, which reduces memory and computational effort requirement. We present numerical results for several examples with various degrees of non-linearity in capillary pressure and relative permeability using both 2D and 3D discrete-and connected-fractured media. The Jacobian-free Newton-Krylov method demonstrates to be very efficient for all the numerical examples. The performance of the fully-implicit model is compared with the IMPES formulation to determine the range of applicability of the proposed method.
Evaluation of Matrix-Fracture Imbibition Transfer Functions for Different Types of Oil, Rock and Aqueous Phase
Authors: Babadagli T. , Zeidani K. 
Published: December 2007

Abstract
Several different versions of the transfer functions evolved from classical Mattax and Kyte’s dimensionless group and Aranofsky et al.’s abstract relationship were tested. Another transfer function derived analytically based on power law relationship between recoverable oil and time was also included in the testing process. The exponents in all these transfer functions reflect the strength and type of the transfer. The recovery curves obtained from the spontaneous imbibition of different aqueous phases (brine and surfactant) into cylindrical rock samples saturated with different types of oil were used to fit the transfer functions. The exponents yielding the best fit to experimental data were obtained and correlated to the effective parameters such as the viscosity of oil, matrix permeability, IFT, matrix size, and wettability using multivariable regression analysis.
The correlations developed were analyzed for the rock and oil types, and IFT. It was observed that the exponential relationships were more suitable for synthetic and processed oil samples whereas the power law transfer functions were more applicable for crude oil cases.
It is hoped that the analysis provided in this paper would facilitate the selection of proper transfer function type for performance estimation of naturally fractured reservoirs.
Recent Successes: MEOR Using Synergistic H2S Prevention and Increased Oil Recovery Systems
Authors: Hitzman Donald O. , Dennis Michael , Hitzman Daniel C. 
Published: December 2007

Abstract
Contemporary investigations of Microbial Enhanced Oil Recovery (MEOR) technologies began in earnest in the 1980’s. Since then, numerous programs have examined the reliability of the concepts, processes, and technical efficacy of recovery biosystems. Despite reported successes, MEOR technologies have not been widely accepted by the oil and gas industry as a means to recover residual oil. The Bio-Competitive Exclusion (BCX) biological process has successfully demonstrated significant oil recovery results in mature waterfloods from the deliberate alteration of indigenous reservoir microflora to an anaerobic denitrifying bacteria (DNB) population through the use of nitrate-based formulae as alternate electron acceptors and microbial nutrient. These environmentally safe inorganic salts complement the naturally occurring volatile fatty acids (VFA) in the reservoir and produced waters, selectively stimulating and increasing the targeted DNB. This designed and controlled manipulation of an indigenous DNB population initiates and increases the production of multiple gas, solvent, and surfactant bio-products which have known and demonstrable oil recovery properties. The BCX technology offers a feasible, practical, and very cost effective, tertiary oil recovery system that concurrently controls reservoir and surface system souring. Field data from California, Oklahoma, China, and Canada are presented.
Dewatering in Hunton Reservoir—Drill Vertical or Horizontal Well?
Authors: Zubarev D. , Patwardhan S. , Kelkar M. , Keefer B. 
Published: December 2007

Abstract
The paper describes an economic analysis carried out for the wells drilled in Hunton Formation in Carney Field in Lincoln County, Oklahoma. The Carney Field produces oil and gas from the Hunton Formation. The field was developed starting in 1995. The Hunton formation covers 2.7 million acres in Oklahoma and in surrounding states of Texas, New Mexico and Arkansas and is one of the most prolific oil producing reservoirs in Oklahoma. Marjo operating Co. is one of the many operators involved in producing from this reservoir. The early development of the Carney field was mostly accomplished through vertical wells. However, in the last two years, the new wells drilled are mostly horizontal wells. It is believed that horizontal wells have better probability of success and better productivity. Horizontal wells also have added advantage of bigger spacing as compared to vertical wells. In this paper, we investigate the efficacy of horizontal wells as against the vertical wells. Our evaluation is based on wells operated by Marjo Operating Company as well as some other operators.
We observe that vertical wells are as economically efficient, or perhaps better, than horizontal wells. We did not find any correlation between horizontal well length and the productivity of the well. Further, for reservoir regions, where the initial oil saturation is higher, vertical wells performed significantly better than horizontal wells.
Chemical Treatments to Enhance Productivity of Horizontal and Multilateral Wells: Lab Studies and Case Histories
Authors: Al-Otaibi M. B. , Nasr-El-Din H. A. , Siddiqui M. A. 
Published: December 2007

Abstract
Many soft sandstone formations are completed with horizontal wellbore. The drilling fluid, water based mud, filter cake is left in place until the completion operations are finished. At that time, a cleanup fluid is pumped to remove the filter cake deposition from the wellbore face. These cleanup fluids can be acid, specific enzymes, oxidizers or acidic water. Reservoir heterogeneity complicates the cleaning process. There is a need for a slow, efficient method to remove filter cake, without affecting the integrity of the formation.
In this paper, a comparison of various cleaning methods was conducted in the lab (using ceramic disks, core plugs) and in the field. Chemical analysis for core effluent and well flowback samples after various treatments was conducted. These tests included: Anthrone method for carbohydrates, and full analysis of the produced solids using acid solubility, XRD, and SEM.
Revitalization of Pilar Field (Sergipe-Alagoas Basin, Brazil) using deviated wells along fault planes – a successful experience.
Authors: Borba C. , Takeguma M. S. , Filho E. J. Souza , Schneider K. N. 
Published: December 2007

Abstract
Pilar oil and gas field, located onshore northeastern region of Brazil, had the production peak by 1985, when produced 1300 m3/d of oil, decreasing since then until reaching 350 m3/d in 1997. Forecasts at that time indicated a very low oil production of about 200 m3/d by year in 2002.
A study was launched in 1997, strongly focused on the characterization of sealing fault planes that control the oil and gas accumulations, which resulted in the projects of deviated wells, following the fault planes. This approach has made possible to drill one single well crossing multiple sets of reservoirs, increasing the possibility of finding virgin reservoirs along trends of producing reservoirs.
As a result, the oil rate has been rising since 1998, reverting the declining tendency of the period between 1985 and 1997. In 2003 the oil rate reached 1100 m3/d. In the period of revitalization, the OOIP has increased 50%.
Modeling CO2 Storage in Aquifers with a Fully-Coupled Geochemical EOS Compositional Simulator
Authors: Nghiem Long , Sammon Peter , Grabenstetter Jim , Ohkuma Hiroshi 
Published: December 2007

AbstractThis paper describes a fully coupled geochemical compositional Equation-of-State (EOS) compositional simulator for the simulation of CO2 storage in saline aquifers. The simulator (GEM-GHG) models the following phenomena: (1) convective and dispersive flow in porous media; (2) phase equilibrium between the oil, gas and aqueous phase; (3) chemical equilibrium for reactions between the aqueous components and (4) mineral dissolution and precipitation kinetics. For numerical robustness and stability, all equations are solved simultaneously. The simulator is applied to the simulation of typical field-scale CO2 sequestration processes, showing the migration of CO2(g) and CO2(aq), the dissociation of CO2(aq) into HCO− and its subsequent conversion into carbonate minerals. Convection of high-density plumes of CO2-rich brine in conjunction with CO2 mineralization around the plumes is illustrated.
Effect of CO2 Impurities on Gas-Injection EOR Processes
Authors: Zhang P. Y. , Huang S. , Sayegh S. , Zhou X. L. 
Published: December 2007

Abstract
Carbon dioxide flooding is a promising enhanced oil recovery method both on technical and, if operating costs are properly controlled, economic grounds. Injecting this greenhouse gas also has environmental merits. Flue gas from power plants is a ready source of CO2; however extracting CO2 for enhanced oil recovery from such a source will increase project costs. Furthermore, to reduce both the net CO2 utilization and the cost of purchasing gas, it is usually necessary to recycle the produced CO2 with as little purification as possible. Therefore, understanding the roles of impurities in fluid phase behaviour and miscibility characteristics is necessary for designing a cost-effective CO2 enhanced oil recovery process.
Laboratory studies of the effect of CO2 impurities on phase equilibrium and minimum miscibility pressure (MMP) were conducted on two Saskatchewan light oils covering a range of densities from 29.5°API to 38°API. The results indicate that the MMP for these light oils could increase unfavourably as the N2 and/or CH4 concentration increased in the CO2 stream. The MMP changes as the type and concentration of impurities in the injected CO2 stream change. However, coreflood tests showed that the near-miscible CO2 displacement might employ the same mechanisms as miscible CO2 flooding to mobilize and displace oil; thus, good oil recovery can be achieved in the vicinity of the MMP. While laboratory measurements are essential in the evaluation of a gas injection process, an equation of state (EOS) simulation was demonstrated to be a useful tool in analyzing the phase behaviour of various injection gases, reservoir fluids, and the gas-oil interactions.
Evolution of Completion Practices in the Wild River Tight Gas Field
Authors: Colwell D. A. F. , O'Brien C. G. J. , Gates T. D. 
Published: December 2007

Abstract
This paper presents the evolution of completion practices and fracture stimulation that has taken place in the Wild River area of Canada over the past 2 years. Since being acquired in March of 2001, 67 wells have been drilled and completed in the field, which is characterized by multiple stacked, tight gas reservoirs. During that time, seven distinct completion phases can be identified, each targeting either a reduction in the total capital expenditure or enhancing production performance by fracture stimulation optimization. On the capital front, a progression of completion tools occurred including standard bridge plugs, proprietary permanent packer frac systems, and composite bridge plugs. Focus areas for production performance improvement included fluid systems, proppant selection, perforating strategy, energizing fluids, and third party quality control. As a result of this evolution, the average completion cost per zone has been reduced by approximately 40% and the average initial production rate has been increased by approximately 150%.
Improved Petrophysical Methods and Techniques for Shaly Sands Evaluation
Authors: Al-Ruwaili Saleh B. , Al-Waheed Hilal H. 
Published: December 2007

Abstract
Clean sands have null or minimal shale and clay, and can adequately be evaluated using petrophysical techniques like neutron-density cross-plot and Archie's equation. Routine core analysis can be enough for validating log-analysis results in clean sands. On the other hand, shaly sands have considerable shale and clay; consequently the above petrophysical evaluation techniques are not adequate. Porosity logs, e.g. neutron, density and sonic, and saturation logs, i.e. deep-resistivity, are affected by the shale and clay present in shaly sands. Additionally, shale and clay affect the electrical properties, the capillary pressure and the transmissibility in shaly sands. The effects of shale and clay, on logs and log-analysis, need to be modeled and incorporated in the petrophysical evaluation in order to obtain a more accurate assessment of shaly sands.
Soft and hard data was acquired in some shaly sands, in Saudi Arabia, to evaluate their storage and flow capacity. Density, neutron, sonic, resistivity and gamma-ray logs were routinely acquired in wells drilled in these formations. Logs like Elemental-Capture-Spectroscopy (ECS) and Nuclear-Magnetic-Resonance (NMR) were acquired in key wells. In some key wells, the core was cut and core analysis was conducted to obtain formation porosity, electrical properties and clay attributes, e.g. clay-type and clay-abundance. The above data was exploited in improving shaly sands petrophysical evaluation, which is discussed and demonstrated in this paper.