Publications of year 1997

Articles in journal or book chapters

A. R. Kovscek, T. W. Patzek, and C. J. Radke. Mechanistic Foam Flow Simulation in Heterogeneous and Multidimensional Porous Media. Society of Petroleum Engineers Journal, 2(4):511--526, December 1997.
[pdf]
Keywords: Foam, EOR, Mobility Control.

Abstract

Gases typically display large flow mobilities in porous media relative to oil or water, thereby impairing their effectiveness as displacing fluids. Foamed gas, though, is a promising agent for achieving mobility control in porous media. Because reservoir-scale simulation is a vital component of the engineering and economic evaluation of any enhanced oil recovery (EOR) or aquifer remediation project, efficient application of foam as a displacement fluid requires a predictive numerical model. Unfortunately, no such model is currently available for foam injection in the field where flow is multidimensional and the porous medium is heterogeneous. We have incorporated a conservation equation for the number density of foam bubbles into a fully implicit, three-dimensional, compositional, and thermal reservoir simulator and created a fully functional, mechanistic foam simulator. Because foam mobility is a strong function of bubble texture, the bubble population balance is necessary to make accurate predictions of foamflow behavior. Foam generation and destruction are included through rate expressions that depend on saturations and surfactant concentration. Gas relative permeability and effective viscosity are modified according to the texture of foam bubbles. In this paper, we explore foam flow in radial, layered, and heterogeneous porous media. Simulations in radial geometries indicate that foam can be formed deep within rock formations, but that the rate of propagation is slow. Foam proves effective in controlling gas mobility in layered porous media. Significant flow diversion and sweep improvement by foam are predicted, regardless of whether the layers are communicating or isolated.

BibTex Entry:

@ARTICLE{Kovscek_1997,
TITLE ={Mechanistic Foam Flow Simulation in Heterogeneous and Multidimensional Porous Media},
AUTHOR ={A. R. Kovscek and T. W. Patzek and C. J. Radke},
journal ={Society of Petroleum Engineers Journal},
volume ={2},
number ={4},
pages ={511--526},
month =dec,
year ={1997},
KEYWORDS ={Foam, EOR, Mobility Control},
URL ={http://ekofisk.stanford.edu/supria/publications/public/spe39102-2.pdf},
ABSTRACT ={Gases typically display large flow mobilities in porous media relative to oil or water, thereby impairing their effectiveness as displacing fluids. Foamed gas, though, is a promising agent for achieving mobility control in porous media. Because reservoir-scale simulation is a vital component of the engineering and economic evaluation of any enhanced oil recovery (EOR) or aquifer remediation project, efficient application of foam as a displacement fluid requires a predictive numerical model. Unfortunately, no such model is currently available for foam injection in the field where flow is multidimensional and the porous medium is heterogeneous. We have incorporated a conservation equation for the number density of foam bubbles into a fully implicit, three-dimensional, compositional, and thermal reservoir simulator and created a fully functional, mechanistic foam simulator. Because foam mobility is a strong function of bubble texture, the bubble population balance is necessary to make accurate predictions of foamflow behavior. Foam generation and destruction are included through rate expressions that depend on saturations and surfactant concentration. Gas relative permeability and effective viscosity are modified according to the texture of foam bubbles. In this paper, we explore foam flow in radial, layered, and heterogeneous porous media. Simulations in radial geometries indicate that foam can be formed deep within rock formations, but that the rate of propagation is slow. Foam proves effective in controlling gas mobility in layered porous media. Significant flow diversion and sweep improvement by foam are predicted, regardless of whether the layers are communicating or isolated.},

}

Internal reports

W. E. Brigham. Water Influx, and Its Effect on Oil Recovery Part 1. Aquifer Flow. Technical report, Stanford University, CA, USA, June 1997.
[pdf]
Keywords: Aquifer, Analytical Work.

Abstract

Natural water encroachment is commonly seen in many oil and gas reservoirs. In fact, overall, there is more water than oil produced from oil reservoirs worldwide. Thus it is clear that an understanding of reservoir/aquifer interaction can be an important aspect of reservoir management to optimize recovery of hydrocarbons. Although the mathematics of these processes are difficult, they are often amenable to analytical solution and diagnosis. Thus this will be the ultimate goal of a series of reports on this subject. This first report deals only with aquifer behavior, so it does not address these important reservoir/aquifer issues. However, it is an important prelude to them, for the insight gained gives important clues on how to address reservoir/aquifer problems. In general when looking at aquifer flow, there are two convenient inner boundary conditions that can be considered; constant pressure or constant flow rate. There are three outer boundary conditions that are convenient to consider; infinite, closed and constant pressure. And there are three geometries that can be solved reasonably easily; linear, radial and spherical. Thus there are a total of eighteen different solutions that can be analyzed. The information in this report shows that all of these cases have certain similarities that allow them to be handled fairly easily; and, though the solutions are in the form of infinite series, the effective results can be put into very simple closed form equations. Some equation forms are for shorter time results, and others are for longer time results; but, remarkably, for all practical purposes, the solutions switch immediately from one to the other. The times at which they switch depend on the sizes of the systems being considered; and these, too, can be defined by simple equations. These simple equation forms provide great insight on the nature of the behavior of these systems. Real field aquifer data are never at constant pressure or constant flow rate. This fact, however, can be handled easily using the superposition integral. This report also discusses this idea and its application, and shows how the simpler analytic solutions make this superposition process considerably easier to perform.

BibTex Entry:

@TECHREPORT{TR103,
TITLE ={Water Influx, and Its Effect on Oil Recovery Part 1. Aquifer Flow},
AUTHOR ={W. E. Brigham},
YEAR ={1997},
MONTH =jun,
INSTITUTION ={Stanford University, CA, USA},
KEYWORDS ={Aquifer, Analytical Work},
URL ={http://ekofisk.stanford.edu/supria/publications/public/tr103.pdf},
ABSTRACT ={Natural water encroachment is commonly seen in many oil and gas reservoirs. In fact, overall, there is more water than oil produced from oil reservoirs worldwide. Thus it is clear that an understanding of reservoir/aquifer interaction can be an important aspect of reservoir management to optimize recovery of hydrocarbons. Although the mathematics of these processes are difficult, they are often amenable to analytical solution and diagnosis. Thus this will be the ultimate goal of a series of reports on this subject. This first report deals only with aquifer behavior, so it does not address these important reservoir/aquifer issues. However, it is an important prelude to them, for the insight gained gives important clues on how to address reservoir/aquifer problems. In general when looking at aquifer flow, there are two convenient inner boundary conditions that can be considered; constant pressure or constant flow rate. There are three outer boundary conditions that are convenient to consider; infinite, closed and constant pressure. And there are three geometries that can be solved reasonably easily; linear, radial and spherical. Thus there are a total of eighteen different solutions that can be analyzed. The information in this report shows that all of these cases have certain similarities that allow them to be handled fairly easily; and, though the solutions are in the form of infinite series, the effective results can be put into very simple closed form equations. Some equation forms are for shorter time results, and others are for longer time results; but, remarkably, for all practical purposes, the solutions switch immediately from one to the other. The times at which they switch depend on the sizes of the systems being considered; and these, too, can be defined by simple equations. These simple equation forms provide great insight on the nature of the behavior of these systems. Real field aquifer data are never at constant pressure or constant flow rate. This fact, however, can be handled easily using the superposition integral. This report also discusses this idea and its application, and shows how the simpler analytic solutions make this superposition process considerably easier to perform.},

}

W. E. Brigham and L. M. Castanier. SUPRI Heavy Oil Research Program Twentieth Annual Report. Technical report, Stanford University, CA, USA, June 1997.
[pdf]
Keywords: Reservoir Definition, In-Situ Combustion, Heavy Oil, Steam, EOR, Formation Evaluation.

Abstract

Supri-A yearly research report.

BibTex Entry:

@TECHREPORT{TR109,
TITLE ={SUPRI Heavy Oil Research Program Twentieth Annual Report},
AUTHOR ={W. E. Brigham and L. M. Castanier},
YEAR ={1997},
MONTH =jun,
INSTITUTION ={Stanford University, CA, USA},
KEYWORDS ={Reservoir Definition, In-Situ Combustion,Heavy Oil,Steam,EOR,Formation Evaluation},
URL ={http://ekofisk.stanford.edu/supria/publications/public/tr109.pdf},
ABSTRACT ={Supri-A yearly research report.},

}

R. G. Hughes, W. E. Brigham, and L. M. Castanier. CT Measurements of Two-Phase Flow in Fractured Porous Media. Technical report, Stanford University, CA, USA, June 1997.
[pdf]
Keywords: Experimental Work, Fractures, Imbibition.

Abstract

The simulation of flow in naturally fractured reservoirs commonly divides the reservoir into two continua: the matrix system and the fracture system. Flow equations are written presuming that the primary flow between grid blocks occurs through the fracture system and that the primary fluid storage is in the matrix system. The dual porosity formulation of the equations assumes that there is no ow between matrix blocks while the dual permeability formulation allows fluid movement between matrix blocks. Since most of the fluid storage is contained in the matrix, recovery is dominated by the transfer of uid from the matrix to the high conductivity fractures. The physical mechanisms influencing this transfer have been evaluated primarily through numerical studies. Relatively few experimental studies have investigated the transfer mechanisms. Early studies focused on the prediction of reservoir recoveries from the results of scaled experiments on single reservoir blocks. Recent experiments have investigated some of the mechanisms that are dominant in gravity drainage situations and in small block imbibition displacements. The mechanisms active in multiphase flow in fractured media need to be further illuminated, since some of the experimental results appear to be contradictory. This report describes the design, construction, and preliminary results of an experiment that studies imbibition displacement in two fracture blocks. Multiphase (oil/water) displacements will be conducted at the same rate on three core configurations. The configurations are a compact core, a two-block system with a 1 mm spacer between the blocks, and a two-block system with no spacer. The blocks are sealed in epoxy so that saturation measurements can be made throughout the displacement experiments using a Computed Tomography (CT) scanner. Preliminary results are presented from a water/air experiment. These results suggest that it is incorrect to assume negligible capillary continuity between matrix blocks as is often done.

BibTex Entry:

@TECHREPORT{TR104,
TITLE ={CT Measurements of Two-Phase Flow in Fractured Porous Media},
AUTHOR ={R. G. Hughes and W. E. Brigham and L. M. Castanier},
YEAR ={1997},
MONTH =jun,
INSTITUTION = {Stanford University, CA, USA},
KEYWORDS ={Experimental Work, Fractures, Imbibition},
URL ={http://ekofisk.stanford.edu/supria/publications/public/tr104.pdf},
ABSTRACT ={The simulation of flow in naturally fractured reservoirs commonly divides the reservoir into two continua: the matrix system and the fracture system. Flow equations are written presuming that the primary flow between grid blocks occurs through the fracture system and that the primary fluid storage is in the matrix system. The dual porosity formulation of the equations assumes that there is no ow between matrix blocks while the dual permeability formulation allows fluid movement between matrix blocks. Since most of the fluid storage is contained in the matrix, recovery is dominated by the transfer of uid from the matrix to the high conductivity fractures. The physical mechanisms influencing this transfer have been evaluated primarily through numerical studies. Relatively few experimental studies have investigated the transfer mechanisms. Early studies focused on the prediction of reservoir recoveries from the results of scaled experiments on single reservoir blocks. Recent experiments have investigated some of the mechanisms that are dominant in gravity drainage situations and in small block imbibition displacements. The mechanisms active in multiphase flow in fractured media need to be further illuminated, since some of the experimental results appear to be contradictory. This report describes the design, construction, and preliminary results of an experiment that studies imbibition displacement in two fracture blocks. Multiphase (oil/water) displacements will be conducted at the same rate on three core configurations. The configurations are a compact core, a two-block system with a 1 mm spacer between the blocks, and a two-block system with no spacer. The blocks are sealed in epoxy so that saturation measurements can be made throughout the displacement experiments using a Computed Tomography (CT) scanner. Preliminary results are presented from a water/air experiment. These results suggest that it is incorrect to assume negligible capillary continuity between matrix blocks as is often done.},

}

N. S. Sagar and L. M. Castanier. Oil-Foam Interactions in a Micromodel.. Technical report, Stanford University, CA, USA, November 1997.
[pdf]
Keywords: Foam, Micromodels, Interfacial Tension, Experimental Work.

Abstract

This report presents results of a pore-level visualization study of foam stability in the presence of oil. Many laboratory investigations have been carried out in the absence of oil, but comparatively few have been carried out in the presence of oil. For a field application, where the residual oil saturation may vary from as low as 0 to as high as 40% depending on the recovery method applied, any effect of the oil on foam stability becomes a crucial matter. Sandstone patterns were used in this study. The micromodels used are two-dimensional replicas of the flow path of Berea sandstone etched on to a silicon wafer to a prescribed depth, adapting fabrication techniques from the computer chip industry. After flooding the models up to connate water and residual oil saturations, surfactant flood followed by gas injection to generate foam was done. Starting with lower concentrations of surfactant and gas injection the procedure was followed up to higher concentrations of surfactant. Visual observations were made using a high resolution microscope and pictures were recorded on videotape before being processed as they appear in this report. The single most important reason for this study on silicon micromodels compared to previous micromodel work is pore dimensions. With glass micromodels, for example, the reaction kinetics of acid etching makes it necessary to enlarge the pores by a factor of 5 to 50 thus providing a serious limitation for their use in studying processes that depend critically on capillary forces or involve thin films as compared to real rock pores. Two different surfactants were used, a fluoro-surfactant (for generating an oil foam) and an Alpha-Olefin Sulfonate. Oseberg crude was the non-wetting phase in the first set of experiments, and Kerosene in the next two sets. While the fluoro-surfactant created a strong static gas-blocking foam in the presence of oil, the Alpha-olefin Sulfonate (AOS) foamer did not. The fluoro-surfactant foam gave the oil-tolerant behavior expected from its non-entering, non-spreading characteristics. The AOS on the other hand, did not behave in accordance with its bulk observations and its behavior was seen to be controlled by formation of oil/foam emulsions. Generation sites for both foam and the emulsions were seen to be controlled by pore geometry and local saturation. For the foam, no obvious link could be found with the number of films observed and the strength of gas blockage. A lot of other interesting observations included snap-off, emulsion formation and breakdown sequences, foam lamella formation and breakdown sequences, and static emulsion and foam in different configurations within the model usually at higher concentrations of surfactant.

BibTex Entry:

@TECHREPORT{TR110,
TITLE ={Oil-Foam Interactions in a Micromodel.},
AUTHOR ={N. S. Sagar and L. M. Castanier},
YEAR ={1997},
MONTH =nov,
INSTITUTION = {Stanford University, CA, USA},
KEYWORDS ={Foam, Micromodels, Interfacial Tension, Experimental Work},
URL ={http://ekofisk.stanford.edu/supria/publications/public/tr110.pdf},
ABSTRACT ={This report presents results of a pore-level visualization study of foam stability in the presence of oil. Many laboratory investigations have been carried out in the absence of oil, but comparatively few have been carried out in the presence of oil. For a field application, where the residual oil saturation may vary from as low as 0 to as high as 40% depending on the recovery method applied, any effect of the oil on foam stability becomes a crucial matter. Sandstone patterns were used in this study. The micromodels used are two-dimensional replicas of the flow path of Berea sandstone etched on to a silicon wafer to a prescribed depth, adapting fabrication techniques from the computer chip industry. After flooding the models up to connate water and residual oil saturations, surfactant flood followed by gas injection to generate foam was done. Starting with lower concentrations of surfactant and gas injection the procedure was followed up to higher concentrations of surfactant. Visual observations were made using a high resolution microscope and pictures were recorded on videotape before being processed as they appear in this report. The single most important reason for this study on silicon micromodels compared to previous micromodel work is pore dimensions. With glass micromodels, for example, the reaction kinetics of acid etching makes it necessary to enlarge the pores by a factor of 5 to 50 thus providing a serious limitation for their use in studying processes that depend critically on capillary forces or involve thin films as compared to real rock pores. Two different surfactants were used, a fluoro-surfactant (for generating an oil foam) and an Alpha-Olefin Sulfonate. Oseberg crude was the non-wetting phase in the first set of experiments, and Kerosene in the next two sets. While the fluoro-surfactant created a strong static gas-blocking foam in the presence of oil, the Alpha-olefin Sulfonate (AOS) foamer did not. The fluoro-surfactant foam gave the oil-tolerant behavior expected from its non-entering, non-spreading characteristics. The AOS on the other hand, did not behave in accordance with its bulk observations and its behavior was seen to be controlled by formation of oil/foam emulsions. Generation sites for both foam and the emulsions were seen to be controlled by pore geometry and local saturation. For the foam, no obvious link could be found with the number of films observed and the strength of gas blockage. A lot of other interesting observations included snap-off, emulsion formation and breakdown sequences, foam lamella formation and breakdown sequences, and static emulsion and foam in different configurations within the model usually at higher concentrations of surfactant.},

}

B. C. Sharma, W. E. Brigham, and L. M. Castanier. CT Imaging Techniques for Two-Phase and Three-Phase In-Situ Saturation Measurements. Technical report, Stanford University, CA, USA, June 1997.
[pdf]
Keywords: Steam, Thermal Recovery, Experimental Work, 3-phase Saturation.

Abstract

The aim of this research is to use the SUPRI 3D steam injection laboratory model to establish a reliable method for 3-phase in-situ saturation measurements, and thereafter investigate the mechanism of steamflood at residual oil saturation. Demiral et al. (1992) designed and constructed a three-dimensional laboratory model that can be used to measure temperature, pressure and heat loss data. The model is also designed so that its construction materials are not a limiting factor for CT scanning. We have used this model for our study. In this study, we saturated the model with mineral oil, and carried out waterflood until residual oil saturation. Steamflood was then carried out. A leak appeared at the bottom of the model. Despite this problem, the saturation results, obtained by using 2-phase and 3-phase saturation equations and obtained from the Cat scanner, were compared with the saturations obtained from material balance. The errors thus obtained were compared with those obtained by an error analysis carried out on the saturation equations. This report gives details of the experimental procedures, the data acquisition and data processing computer programs, and the analysis of a steamflood experiment carried out at residual oil saturation.

BibTex Entry:

@TECHREPORT{TR107,
TITLE ={CT Imaging Techniques for Two-Phase and Three-Phase In-Situ Saturation Measurements},
AUTHOR ={B. C. Sharma and W. E. Brigham and L. M. Castanier},
YEAR ={1997},
MONTH =jun,
INSTITUTION = {Stanford University, CA, USA},
KEYWORDS ={Steam, Thermal Recovery, Experimental Work, 3-phase Saturation},
URL ={http://ekofisk.stanford.edu/supria/publications/public/tr107.pdf},
ABSTRACT ={The aim of this research is to use the SUPRI 3D steam injection laboratory model to establish a reliable method for 3-phase in-situ saturation measurements, and thereafter investigate the mechanism of steamflood at residual oil saturation. Demiral et al. (1992) designed and constructed a three-dimensional laboratory model that can be used to measure temperature, pressure and heat loss data. The model is also designed so that its construction materials are not a limiting factor for CT scanning. We have used this model for our study. In this study, we saturated the model with mineral oil, and carried out waterflood until residual oil saturation. Steamflood was then carried out. A leak appeared at the bottom of the model. Despite this problem, the saturation results, obtained by using 2-phase and 3-phase saturation equations and obtained from the Cat scanner, were compared with the saturations obtained from material balance. The errors thus obtained were compared with those obtained by an error analysis carried out on the saturation equations. This report gives details of the experimental procedures, the data acquisition and data processing computer programs, and the analysis of a steamflood experiment carried out at residual oil saturation.},

}

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Maintained by Herve Gross, SUPRI-A PhD Candidate.

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WARNING

Publications of year 1997

Articles in journal or book chapters

Abstract

Internal reports

Abstract

Abstract

Abstract

Abstract

Abstract