bluuebunny/crossref_metadata_2025_split huggingface dataset:
What Determines Residual Oil Saturation in Three-Phase Flow?
Authors: Blunt M. J. , Fenwick D. H. , Zhou Dengen 
Published: December 2007

Abstract
We present a theoretical and experimental treatment of three phase flow in water wet porous media from the molecular level to the core scale. We compute the equilibrium thickness of a flat oil layer between water and gas considering both van der Waals and structural forces. We show that although most oils will spread over water, they will eventually form a film that is only a few molecules thick. The film thickness, which is in the range 0.1-5 nm, is determined by the capillary pressure and by whether or not the film was formed from thinning a thicker layer or by encroaching over a hitherto clean interface. Both spreading and non-spreading oils can form thin films. Drainage through this film would be far too slow to account for the recoveries seen experimentally. We then present results from drainage experiments in capillary tubes with a square cross-section. The tube has water wetting the corners and contains oil ganglia separated by air bubbles along its length. The gravitational driving force in the experiment allows oil ganglia to drain by swelling the oil film. We predict not only that eventually all the oil is recovered, but that we can calculate the drainage rate. The predicted rate agrees well with the measured values. Finally we perform a series of gravity drainage experiments in sand columns at high and low oil/water surface tensions. Air is introduced into the top of the column containing waterflood residual oil. At the end of the low surface tension experiment there is a thick oil layer (several microns across) between water and gas, stabilized by capillary forces, whereas for the high surface tension fluids, only a molecular oil film is present. In both cases oil is displaced by air, since the oil ganglia will drain under gravity by swelling the oil films. However, the low surface tension case gives a lower final recovery, since a significant amount of oil remains in the column in the thick oil layers. In both experiments virtually all the oil can drain from the top of the column.
The residual oil saturation in the presence of water and gas can be almost zero under favorable circumstances.
Influence of Connate Water on Oil Recovery by Gravity Drainage
Authors: Skauge Arne , Eleri O. O. , Graue Arne , Monstad Per 
Published: December 2007

Abstract
This paper summarizes results from gas gravity drainage experiments at different water saturations. The initial water saturation was varied from zero to very high water saturations where water starts to segregate during gravity drainage. The fluid distribution detected by in-situ saturation measurements along the core was compared to effluent production.
The results show that oil recovery by gas gravity drainage depends on the connate water saturation. A maximum in the oil recovery was observed at intermediate high water saturation. The total residual liquid phase (sum of oil and brine) increased at high initial water saturation.
The experimental results show that water-oil capillary forces influence the total liquid production by gravity drainage. The oil relative permeability increased with connate water present.
Surfactant Flooding: Technical and Economical Conditions to Succeed
Authors: Jakobsen S. R. , Hovland Frank 
Published: December 2007

Abstract
Surfactant flooding in four North Sea sandstone reservoirs have been studied by numerical simulations. The paper discusses the technical and the economical potential for surfactant flooding in these reservoirs, in addition to the uncertainty involved. The results indicates that optimum economy is achieved when typically less than 50 % of the surfactant flood technical potential is recovered.
Oil Recovery Improvement Through Profile Modification by Thermal Precipitation
Authors: Acock A. M. , Reis J. C. 
Published: December 2007

ABSTRACT
This paper presents a method for lowering the permeability of thief zones in oil reservoirs to improve recovery during waterflood operations. The method consists of preheating the thief zone around the injection or production well by injecting hot water or steam and then injecting a hot, saturated chemical solution. If the chemical has a lower solubility at reservoir temperature than at injection temperature, cooling within the formation will result in the precipitation of solids in the pore spaces.
Several chemicals were identified as having a suitable temperature-dependent solubility with a low environmental toxicity, including potassium carbonate and sodium borate. The porosity and permeability reduction from temperature-dependent precipitation of these chemicals was then experimentally determined and a correlation between the permeability and porosity reduction was obtained. A theoretical analysis of this promising new process and how it can be applied are also presented.
Miscible Displacement in Fractured Porous Media: Part II—Analysis
Authors: Firoozabadi Abbas , Tan J. C. T. 
Published: December 2007

ABSTRACT
Numerical simulation of miscible displacement experiments in fractured porous media was carried out to analyze the data. It was found that both the location and the magnitude of the fracture permeability heterogeneity were the main factors in determining the miscible displacement efficiency. The stripping of solute from matrix to fracture, which is caused by the permeability variation in the fracture, significantly increases the recovery efficiency. By taking the fracture permeability heterogeneity into account, the experiments were successfully simulated.
Determination of Injector Steam Quality and Flow-Rate From Orifice Data and Wellhead Pressure
Authors: Blacker H.F. 
Published: December 2007

Abstract
Obtaining accurate measurements of steam injection rate and quality for each injection well in a Thermal EOR flood is an essential part of effective flood management. This paper presents a technique which can be employed, without costly upgrades to field equipment, that provides a relatively accurate estimate of both steam injection rate and steam quality on a continuous basis.
A method of determining a well's injection characteristic is given. This response to injection is then used in conjunction with a conventional orifice flow calculation to provide an estimate of injection rate and quality that cannot be obtained from the orifice flow data alone. The theory and results of the initial field testing are presented in this paper.

Introduction
A series of field tests were run at the Midway Sunset Field with the objective of quantifying our ability to accurately determine an injection well's rate and quality from an orifice flow correlation (James Equation) and the change in wellhead pressure due to a change in mass flow rate and quality.
The Simulation of Paraffin Deposition and Removal in Wellbores
Authors: Keating J. F. , Wattenbarger R. A. 
Published: December 2007

ABSTRACTParaffin deposition creates production problems and formation damage. To eliminate these problems, the deposited paraffin must be removed. Paraffin deposition and removal in reservoirs has been simulated by Ring and Wattenbarger1,2 and paraffin deposition due to natural cooling in reservoirs has been simulated by Peddibhotla.3 The objective of this work is to simulate paraffin deposition and removal in wellbores.The paraffin simulator described in this paper models heat flow in the wellbore, reservoir, underburden, and overburden. This simulator also models mass flow in the wellbore and reservoir. This mass is composed of three pseudocomponents (gas, oil and paraffin) that can exist in three phases (vapor, liquid and solid). Some of this solid paraffin mass deposits onto the tubing during production. This natural phenomena was modeled with the following depositional mechanisms: (1) diffusion deposition and (2) shear deposition. Only one mechanism is used to model paraffin removal, the dissolving of solid paraffin.Paraffin deposition results are presented for a single hypothetical well. These results indicate that only a fraction of the precipitated paraffin deposits onto the tubing. Paraffin removal results are presented for the following three thermal removal techniques: (1) hot oil injection, (2) downhole heaters, and (3) electric tubing heating. These results indicate that hot oil may cause formation damage if the paraffin concentration of the injected oil is high. These results also indicate that downhole heaters and electric heating of the are is a viable thermal removal techniques.
Uncertainty in Well Test Interpretation
Authors: Horne R. N. 
Published: December 2007

Summary
Uncertainty is inherent in any nonlinear inverse problem. Well test interpretation suffers from a particularly unfortunate variety of uncertainties that combine to reduce the confidence that can be associated with the answers obtained. Nonetheless, well test data provide one of the few effective methods of direct reservoir analysis, and therefore it is important for petroleum engineers to overcome as much of the uncertainty as possible, and to understand that part which cannot be overcome. This paper will attempt to summarize the uncertainties found in well test analysis, will show examples of the difficulties, and will discuss methods that have been proposed to reduce or eliminate them.
Coal Gas Openhole Well Performance
Authors: Mavor M. J. 
Published: December 2007

Abstract
Gas production from coal seams has been highly successful due to the use of open-hole completion techniques in the high permeability fairway of the San Juan Basin (Colorado and New Mexico) Fruitland Formation. Based upon extensive formation evaluation data collected during Gas Research Institute funded research efforts, dynamic open-hole (cavity) completion production out-performed hydraulic fracture completion production regardless of the magnitude of natural fracture permeability due to lack of formation damage. This paper will illustrate four examples of the use of open-hole completion procedures that resulted in undamaged completions in reservoirs with absolute permeability ranging from 0.9 to 95 md. The formation evaluation data upon which the conclusions were based included open-hole logs, production logs, sonar logs, single well tests, and interference tests. The latest information has not been previously reported upon in the literature.
An Approach for Implementing Dual Porosity Models in Existing Simulators
Authors: Chen J. , Miller M.A. , Sepehrnoori K. 
Published: December 2007

Abstract
In dual porosity modeling of naturally fractured reservoirs, the reservoir is idealized as a set of disconnected matrix blocks within a highly conductive fracture network. It has been well recognized that the conventional dual porosity model does not accurately model matrix/fracture transfer flow. In the recent literature, matrix blocks have been further discretized to account for transient flow. Unfortunately, this approach greatly increases computational cost and requires much code modification if one tries to add a dual porosity option to an existing single porosity simulator.
In this paper, a new dual porosity modeling approach is presented for oil/water flow in fractured reservoirs. In the formulation, matrix blocks are also discretized. The resulting finite-difference equations for the matrix blocks, however, are mathematically decoupled from the fracture equations. The equations for the fracture system are the same as for single porosity models except for a source and/or sink term for each grid. This scheme does not affect the formulation of the original simulator, since the matrix computations are decoupled. This also greatly reduces computational and coding effort. Also, implicitness of the primary variables is maintained.
The model is verified by solution of Warren and Root's classical dual porosity model and an analytical solution which incorporates transient flow in matrix blocks. Results of the new model are also compared with fine-grid simulation of a fractured reservoir, in which both the fracture network and matrix blocks are discretized. Excellent agreement is achieved for a variety of reservoir properties. The simulator is also used to model published laboratory experiments and to conduct field-scale simulation studies. These results show that the new simulator provides computationally efficient and accurate means of modeling fractured reservoirs. The formulation developed can easily be extended to other recovery processes by modifying existing single porosity simulators.

Introduction
The most efficient approach to modeling fractured reservoirs appears to be the dual porosity model, proposed by Barenblatt et al. (1960) and introduced to the petroleum industry by Warren and Root (1963). The dual porosity model assumes that two equivalent continuous porous media are superimposed: one for the fracture system and another for the rock matrix. Continuity equations for each system are connected by so-called transfer functions that characterize flow between matrix blocks and fractures. Since Kazemi et al. (1976) introduced the first multiphase dual porosity model, almost all subsequent dual porosity models have been based on modifications of the transfer functions. These transfer functions are what distinguish various dual porosity models in the literature. Various transfer functions in the literature can be classified into three categories:the basic transfer function and its modifications,subgrid methods, anddiffusion methods.
P. 461^
Core Damage Effects On Compaction Behaviour
Authors: Holt Rune M. , Brignoli Marco , Fjær Erling , Unander Tor Erling , Kenter Cor J. 
Published: December 2007

Abstract
Core damage caused by stress release is a source of potentially large errors in reservoir compaction predictions. Synthetic sandstone (with properties close to a certain reservoir rock) created under controlled stress conditions, can simulate the behaviour of both a virgin reservoir rock and a cored rock. The difference in behaviour is then an effect of coring. For low levels of depletion, uncorrected core measurements may lead to largely overestimated compaction in very weak sandstone. Core damage effects increase with stress and stress anisotropy. Field data supports the relation between core damage (seen through core recovery) and compaction behaviour.
Waterflooding of oil saturated Stevns outcrop chalk
Authors: Vanggaard Morten , Christensen Helle F. 
Published: December 2007

Abstract
Oil saturated specimens of Stevns outcrop chalk were tested in a standard Hoek cell. The test programme included uniaxial strain and waterflooding. The waterflooding test results lead to the conclusion that above the yield stress level the Stevns chalk compacts due to waterflooding. Strain gauges measurements in 3 levels on the specimen indicated that the waterflooding may be characterized as a plug flow and local compaction due to waterflooding was recorded. SEM studies showed no significant signs of cementation due to specimen preparation before testing.
Wellbore stability analysis in brittle rocks with continuous damage model
Authors: Shao J. F. , Khazraei R. 
Published: December 2007

Abstract
In this paper, the application of continuum damage mechanics to wellbore stability analysis is presented. In order to show the impact of the induced damage by microcracking process, three constitutive models are considered; an elastoplastic model, an isotropic damage model and an anisotropic damage model. All these models are calibrated from the same triaxial test on a sandstone. The application of the models to a plane strain borehole allows to clearly show impacts of different irreversible deformation mechanisms on predicted wellbore stability.
A Semi-Analytic Elastoplastic Model for Wellbore Stability with Applications to Sanding
Authors: Bradford I. D. R. , Cook J. M. 
Published: December 2007

ABSTRACT
A semi-analytic elastoplastic model predicting the onset of failure in wellbores subjected to in-situ stress and pore pressure fields is presented. The model also has sanding applications. Rock elastic behaviour is modelled as being linear, with the plastic response described by a non-associated Mohr-Coulomb strain hardening deformation theory. The pore pressure gradient is taken into account using a source solution at the wellbore. Constitutive relations are calibrated using triaxial tests on Castlegate Sandstone cores. Hollow cylinder experiments, again performed with Castlegate sandstone, are used to evaluate predictions. Numerical examples illustrate how constitutive parameters influence the stress state around the wellbore and the onset of failure.
The Crack Tip Solution for Hydraulic Fracturing in Rock of Arbitrary Permeability
Authors: Lenoach B. 
Published: December 2007

ABSTRACT
This paper extends previous work on analytical solutions for a KGD hydraulic fracture to include the effect of fluid loss. Our main new results are intermediate asymptotic solutions for arbitrary rock permeability; it is shown how these may be obtained in an asymptotic series whose leading term is the near-tip solution in the high permeability limit. In fact there is always a region immediately adjacent to the fluid front where the solution is dominated by fluid loss. The extent of this region depends on the fundamental parameter δ; our most important conclusion is that the solution may always be constructed as a series in δ which starts from the loss dominated limit.
Simulation and Field Analysis of Waterflood Induced Fracturing
Authors: Settari A. , Warren G. M. 
Published: December 2007

Abstract
The paper describes the theory of modelling waterflood induced fractures and the features which distinguish this process from conventional hydraulic fracturing. The mechanisms which are described in detail and illustrated by examples include 2-dimensional leak-off, the effect of previous injection, relative permeability and thermal effects, and pre-existing propped or acid fractures. All of these features have been found necessary for accurate matching of complex injection history of North Sea wells.
In-Situ Reservoir Compaction Monitoring in the Groningen Field
Authors: Mobach E. , Gussinklo H. J. 
Published: December 2007

Abstract
In-Situ reservoir compaction measurements have been performed in the Groningen field since 1974. The technique is based on regularly monitoring the distance between radio-active markers shot at regular distances across the reservoir. The application of this technique in the Groningen field is unique in the sense that it is normally used to monitor compaction in unconsolidated reservoirs, that compact much more than the Groningen reservoir. In practice, it has been proven difficult to obtain the required accuracy, 1 mm per 10 m. Until recently, the vertical rock compressibility could only be measured in three of the eight wells. The reservoir rock is so competent, that the target resolution is very close to the instrument resolution. Over the years, much effort has been put into improving the accuracy and reliability of the measurements, improvement on tools as well as on interpretation techniques. In 1993/1994, part of the surveys has been re-interpreted, using a new marker position algorithm, and a selection mechanism has been developed to identify statistically significantly deviating data. As a result, in all but one well could the vertical compressibility be obtained. The in-situ measured compressibilities match with the compressibility as inferred from the surface subsidence over the field.
Reservoir Microseismicity at the Ekofisk Oil Field
Authors: Rutledge James T. , Fairbanks Thomas D. , Albright James N. , Boade Rodney R. , Dangerfield John , Landa Geir H. 
Published: December 2007

Abstract
A triaxial, downhole geophone was deployed within the Ekofisk oil reservoir for monitoring ambient microseismicity as a test to determine if microearthquake signals generated from discrete shear failure of the reservoir rock could be detected. The results of the test were positive. During 104 hours of monitoring, 572 discrete events were recorded which have been identified as shear-failure microearthquakes. Reservoir microseismicity was detected at large distances (1000 m) from the monitor borehole and at rates (&gt; 5 events per hour) which may allow practical characterization of the reservoir rock and overburden deformation induced by reservoir pressure changes.
Underground Storage of Hydrocarbons in Japan – Past and Present
Authors: Ogawa T. , Yamaguchi U. , Yamaguchi K. 
Published: December 2007

Abstract
Underground spaces are becoming more and more attractive as a new frontier, with the increase in public necessities such as rearrangements of infrastructures, conservation of natural environments, and preservation of landscapes in urban areas. They are also important for the storage of hydrocarbons, such as oil, LPG and LNG. This paper reviews the history and current situations of hydrocarbon storage in Japan, and the state of the art applied in design is highlighted.
Waste Disposal Monitoring Using the Surface Displacement Field
Authors: Rothenburg Leo , Dusseault Maurice B. , Bilak Roman A. , Bruno Michael S. 
Published: December 2007

Abstract
Massive injection of slurried solid waste generates permanent strains and displacements. These can be measured and analyzed to give useful information related to the shape and orientation of the injected body, and therefore lead to a monitoring approach based on accurate surface measurements of vertical movements or tilt. We discuss waste emplacement, present information showing the magnitudes of the final deformations, and show how some displacement field features are sensitive to certain parameters, whereas others are insensitive. Tilt measurements continuously through time give the best possibility of accurate monitoring of the waste body.
Sensitivity and Uncertainty Analysis Applied to Cavity Design Computations in Rock Salt
Authors: Wallner Manfred 
Published: December 2007

Abstract
Geotechnical safety for a cavity field will be assessed on the basis of model computations. The statistical uncertainty of rock salt parameters as well as possible variations in the dimensions of a cavity field under design result in the necessity to carry out a parametric study. The purpose of the paper is to explain probabilistic modeling with respect to structural response computations, using sensitivity and uncertainty analysis. Probabilistic finite element computations have been carried out for a hexagonal cavity configuration. The results are discussed with respect to the variability of the following parameters and their interrelation: diameter, spacing, depth and height of the cavities, creep of the salt rock, and stiffness of the overburden.
Modelling of the Compaction Behaviour of Fractured Chalk
Authors: Gutierrez Marte , Tunbridge Lloyd , Hansteen Harald , Makurat Axel , Barton Nick , Landa Geir Helge 
Published: December 2007

Abstract
Numerical modelling of the behaviour of the fractured chalk in the Ekofisk reservoir was performed using the distinct element code UDEC-BB. The non-linear fracture behaviour was modelled by the Barton-Bandis model, while the pore collapse of the rock matrix was modelled by NGI's cap plasticity formulation. The analyses were performed to investigate the effects of fractures, both natural and compaction induced on the compaction behaviour of the Ekofisk reservoir, and to determine the shear/normal displacement and permeability coupling of the fractures during pressure depletion and water injection. The results of the modelling could be used as basis for explaining the observed behaviour of the Ekofisk field, provide possible guidelines to future actions in the development of the Ekofisk field, and as input to large-scale models of the Ekofisk field.