bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Model for Calculating Polymer Injectivity Including the Effects of Shear Degradation
Authors: Sorbie K. S. , Roberts L. J. 
Published: December 2007

Abstract
Polymers are frequently injected into oil reservoirs in order to improve recovery. As they reduce the in-situ mobility of the aqueous phase (either by viscosity increase or permeability reduction), the fluid injectivity generally drops. It is very useful to be able to estimate in advance from a few laboratory measured quantities (a) the injectivity of the polymer and (b) whether the polymer is likely to be seriously degraded by the high shear experienced in the near-wellbore region. It is difficult to calculate the injectivity of the polymer solutions due to their complex rheological behaviour within porous media, especially when the polymer mechanically degrades.
In this paper, we investigate one approach to calculating the injectivity of polymers in the general case where mechanical degradation occurs. A kinetic model for polymer degradation is proposed which is used to obtain the radial viscosity profile of the degrading polymer. This may in turn be used to calculate the steady-state pressure drops associated with the degrading polymer. The model is based on a discrete multicomponent representation of the polymer molecular weight distribution (MWD). During mechanical degradation, the MWD changes as higher components degrade into lower molecular weight fragments. The degradation rate of a given component of the MWD is related to the local shear/elongational stress within the porous medium and the concentration of the component (Ci).
The model is used to match the results of experiments studying the shear degradation of polyacrylamide (PAM) in radial sandstone cores. The quantitative predictions of the model are very satisfactory. In addition, the model gives insight into the mechanism of shear degradation of polymers in porous media.
Analysis of the Performance of the M-6 Area of the Tia Juana Field, Venezuela, under Primary, Steam-Soak, and Steamdrive Conditions
Authors: Puig Fernando , Schenk Leendert 
Published: December 2007

Summary
This paper deals with the reservoir performance of the M-6 Project Area in the south-east of the Tia Juana field. The field is one of the four heavy oil fields located along the eastern shore of Lake Maracaibo in Venezuela, collectively known as the Bolivar Coast fields. Since the early 1930's the area covered by these fields suhsides, an observation which one could not fail to make in this swampy coastal area. The subsidence prompted the construction of coastal dykes for protection against flooding and also the installation of a network of benchmarks which are surveyed biannually, to monitor ground level changes in detail. It soon became apparent that there was a direct correlation between subsidence and oil withdrawal, implying that the compaction phenomenon acts as an oil production mechanism. This established a cause/effect chain of oil production/pressure decline/formation compaction/surface subsidence which has since been a fertile field for investigation.
The application of thermal recovery methods in these fields has been geared to make full use of the compaction pheonmenon. First steam soak is applied to accelerate oil production, bringing down the reservoir pressure to the lowest possible level. This maximises the oil recovery contribution by compaction, which is as high as 15% STOIIP. The resulting low reservoir pressure level is favourable for steam drive as follow-up phase.
Because subsidence is measured on a routine basis in the fields and compaction is not, an important aspect of the study is the subsidence/compaction relationship. There are theoretical considerations which indicate that compaction approximately equals subsidence volumetrically for reservoirs which are large in relation to depth. This is supported for the M-6 area by the results of the reservoir performance analysis. The compaction of the area has been compared with theoretical values based on formation compressibilities measured on Tia Juana core samples, petrophysical data and the reservoir pressure performance. To obtain a match the pressure data had to be adjusted for vertical heterogeneity of the oil sands and time delay in the pressure decline of shales caused by their extremely low permeability. The calculation procedure developed to describe the reservoir behaviour of Bolivar Coast type heavy oil fields during depletion enhanced by steam soak, is considered satisfactory for practical considerations (oil production forecasts, dyke design).
During the steam drive phase of M-6 the relative importance of compaction has strongly decreased. Additional performance is required, however, to enable definitive conclusions on the effect of steam drive on compaction.
An Automated Method for Predicting Full-Scale CO2 Flood Performance Based on Detailed Pattern Flood Simulations
Authors: Rester Stephen , Todd M. R. 
Published: December 2007

Abstract
A procedure is described for estimating the response of a field scale CO2 flood from a limited number of simulations of pattern flood symmetry elements. This procedure accounts for areally varying reservoir properties, areally varying conditions when CO2 injection is initiated, phased conversion of injectors to CO2, and shutin criteria for producers. Examples of the use of this procedure are given.
Progress Report: Big Muddy Field Low-Tension Flood Demonstration Project with Emphasis on Injectivity and Mobility
Authors: Ferrell H. H. , Gregory M. D. , Borah M. T. 
Published: December 2007

ABSTRACT
A Demonstration Project for the low tension flood process was initiated in the Big Muddy Field in 1980. This paper introduces the concept of optimum slug mobility for maximum oil recovery and injectivity in the Second Wall Creek reservoir. A procedure to determine the optimum mobility for a low tension flood is described, and the early field performance data is compared to the laboratory design.
Statistical Network Theory of Three-Phase Relative Permeabilities
Authors: Heiba A. A. , Davis H. T. , Scriven L. E. 
Published: December 2007

ABSTRACT
The statistical network model and percolation theory of capillary pressure and relative permeabilities in low capillary number displacements account for much of the behavior of two fluid phases under the gamut of wetting conditions encountered in reservoir rocks (SPE 11015, SPE 12172). The model and theory are here extended to three fluid phases, viz. gas, oil, and water. For convenience in illustrating the theory the gas is taken as everywhere nonwetting against the oil and water, and the oil as everywhere nonwetting against the water.
The starting point is the representation of the chaotic connectivity of porespace by a bond-disordered Bethe tree; also as before, the bonds are characterized by a single statistically distributed parameter, porethroat radius, with which other pore dimensions are regarded as completely correlated. The distribution of the three phases among the poresegments, or bonds, is taken as controlled by capillary pressure, wettability, and prior occupancy criteria of allowability to a locally invading phase: the complication is the competition among three phases. These criteria and accessibilities evaluated with percolation theory in turn define the pore filling sequence in terms of phase-occupancy-conditioned poresize distributions. From this follow occupancy-conditioned distributions of segment volumes, and thus saturations; and occupancy-conditioned distributions of hydraulic conductance, from which relative permeabilities are again calculated using Stinchcombe's method from percolation theory.
Examples include simultaneous displacement of oil by gas and water, and waterflooding in the presence of an evolved gas saturation. Effects of oil wettability and of phase swelling by mass transfer are touched on. The predictions of relative permeabilities and saturation states accessible by a given process from a given initial state highlight the sensitivity of displacements to the history of the process, or to the details of a laboratory experiment, when three phases are present. Limited comparisons are made with the few published data.
A Group Contribution Activity Coefficient Model for Enhanced Oil Recovery Process Involving Electrolyte Solutions: Part II—Solutions in the Presence of Partial Molecular Association
Authors: Chien M. C. H. , Lee Sheng-Tai 
Published: December 2007

ABSTRACT
In Part I of this series, a group contribution activity coefficient model for electrolyte solutions was developed based on Debye-Hückel theory, solvation theory and local composition theory. It was demonstrated that the model can satisfactorily correlate the complex thermodynamic properties of electrolyte solutions in the absence of partial molecular association. In this work, the above described model is extended to electrolyte solutions which exhibit partial molecular association.
In addition to the thermodynamic theories introduced in the preceding paper, the present model further includes the chemical equilibrium theory to represent chemical association between molecular species in the solution. The equilibrium thermodynamic properties are then solved by invoking a recently developed simultaneous phase and chemical equilibrium calculation scheme.
The reliability of the proposed model is tested for two important thermodynamic behaviors occurring in related solutions, namely, micellization and the phase transition upon salt addition.
First, experimental mean ionic activity coefficients of the homologous sodium carboxylates in aqueous solutions are compared with the correlation. Chemical equilibria are introduced to account for the micellization of sodium carboxylates. The chemical equilibrium constant and aggregation number are found to increase with the length of hydrocarbon tail in the ampliphile. The sudden drop in the mean ionic activity coefficient caused by micellization is correctly predicted. The average deviations between the predicted mean ionic activity coefficients and experimental-data are generally less than 5%.
Second, published experimental phase behavior data of water-NaCl-t-butanol-n-paraffin mixtures are compared with the correlations. It is found that the aggregation between water and tbutanol is responsible for the abnormal amounts of water in the upper phase, while the aggregation between water and oil is responsible for the large amounts of oil in the middle phase. The aggregations are modelled by chemical equilibria. The type II-/III/II+ phase transition for the above system upon successive addition of salts are correctly predicted. The critical salinities and phase compositions are also well correlated. Studies also show that the vertices of the three phase region are very sensitive to the alcohol concentration and suggest empirical correlations, such as Hand plots, may have to consider the surfactant effect as well as the salinity effect on the vertices of the three phase region.
Our studies show that the model is capable of modelling micellization and the complex phase transion of oil-water mixture containing an amphilphile, and that it can be incorporated in a simulator to study the mechanisms of recovery processes involving electrolyte solutions or to design such processes.
A Laboratory and Computer Model Evaluation of Immiscible CO2 Flooding in a Low-Temperature Reservoir
Authors: Sigmund P. M. , Kerr William , MacPherson R. E. 
Published: December 2007

ABSTRACT
This paper describes the procedures used in evaluating CO2 for immiscible displacement of a 22-24 API oil saturated at its bubble point of 1650 psi (11373 kPa). The oil is contained in the low temperature 95.9°F (35.5°C) Glauconitic sand of the Retlaw Mannville V Pool located in South Eastern Alberta. A combination of laboratory experimental data and computer model studies used in the evaluation are discussed.
Phase behaviour and multiphase flow characteristics are examined for the CO2 – reservoir oil system at conditions where liquid/liquid and liquid/liquid/vapour phases exist. Measured experimental equilibrium phase, compositions, densities and viscosities are reported for single contact and multiply-contacted mixtures of recombined oil and CO2. Measurement of composition profiles obtained during slim tube displacement of recombined oil by CO2 at L/L and L/L/V conditions of temperature and pressure are also reported. The high displacement efficiencies that occur are attributed to the solvency of the CO2 rich phase that forms in the flood front after methane and nitrogen have been stripped from the oil. The effects of swelling and viscosity reduction on displacement efficiency are also discussed.
A 1-D model, calibrated with the experimental data was used to predict the effect of using a 25% PV CO2 slug before waterflood on recovery in swept portions of the pool. The results suggest that the use of CO2 followed by waterflood will result in high microscopic displacement efficiencies in swept portions of the reservoir even though miscibility between oil and CO2 does not develop.
Pressure Transients Caused by Fracturing
Authors: Oliver D. S. 
Published: December 2007

ABSTRACT
Porous-elastic theory is used to explain how hydraulic fracturing operations can cause nearly instantaneous pressure responses in nearby wells. The theory is applied to a field example where it is used to estimate fracture azimuth for a vertical hydraulic fracture. Knowledge of fracture azimuth can be used to increase productivity from a reservoir.
Partially Penetrating Fractures: Pressure Transient Analysis of an Infinite Conductivity Fracture
Authors: Rodriguez Fernando , Horne R. N. , Cinco-Ley Heber 
Published: December 2007

ABSTRACT
The effect of the partial penetration of an infinite conductivity fracture on the transient pressure behavior of a vertically fractured well is investigated.
Analysis of results shows that the pressure behavior of a well intersected by a partially-penetrating infinite conductivity vertical fracture can be divided into three flow periods: 1) the early time flow period which is characterized by a formation linear flow as in the case of a fully-penetrating infinite-conductivity vertical fracture, 2) the infinite-acting flow period and 3) the pseudoradial flow period which develops after the effects of the vertical boundaries of the reservoir are felt in the pressure behavior of the well.
A log-log graph of log(hf/h)pwD versus log tDxf shows a slope of one half during tine early time How period of a well with an infinite-conductivity partially penetrating fracture. The time for the end of the early time flow period is directly related to the square of the dimensionless height of the fracture, hfD, which is defined as the ratio between the height of the fracture and its half length. This time becomes so small for small values of hfD that the linear formation flow period will not show up for practical purposes.
The solutions during the infinite-acting flow period are, for the different values of penetration ratio and a given value of hfD, characterized by a single envelope curve in the log-log graph previously mentioned.
The time for the start of the pseudoradial flow period shows no dependence on the penetration ratio and on the dimensionless fracture height except for fractures with dimensionless heights larger than about 1 and penetration ratios smaller tha 1/5.
Even though solutions were mainly obtained for the case of a fracture located at the middle of the formation, the effect of offsetting the fracture was investigated for some particular cases. As expected, the solutions are the same up to the end of the infinite acting flow period which slightly varies as a function of the fracture location.
The solutions are presented in the form of type curves suitable for transient pressure analysis procedures.
Prevention of Calcium Carbonate Precipitation From Calcium Chloride Kill Fluid in CO2-Laden Formations
Authors: Kapelke M. S. , Caballero E. P. 
Published: December 2007

ABSTRACT
Water containing high concentrations of calcium chloride can now be efficiently used as a kill fluid in production wells having heavily laden carbon dioxide formations. This investigation has determined that the amount of calcium carbonate scale normally produced under these conditions can be reduced by increasing the carbon dioxide partial pressure and increasing the tubing pressure leading from the casing annulus.
An Evaluation of Analysis Methods Used To Estimate Well Damage From Pressure Buildup Tests in the Prudhoe Bay Reservoir
Authors: Jones K. D. 
Published: December 2007

ABSTRACT
This work shows that effective well damage determination from pressure buildup tests in complex, developed reservoirs may be best achieved through early time data analysis. Extensive analysis was done using field data from the Prudhoe Bay reservoir in Alaska· Conventional Horner analysis is largely ineffective in this reservoir because of distortion of the late time data by boundary effects. The early time data are affected by partial completion of a large net pay zone. Five different analysis techniques were used to analyze the pressure buildup data. Results from these methods were correlated with production histories and scale damage removal treatments on thirty-two Prudhoe Bay wells. A radial implicit simulator was also used to history match the pressure behavior in several buildup tests to verify the analytic results.
It was found that the McKinley Early Time Analysis Method, modified for partial completion, provided the most reliable estimate of well damage at Prudhoe Bay. The method can provide a qualitative indication of well damage in the presence of a constant-pressure boundary (the gas cap at Prudhoe Bay). The more reliable estimates of well damage allowed us to plan a more effective well stimulation treatment program.
NOX Reduction Methods for California Steam Generators by Applied Technology
Authors: Anderson D. F. , Szytel Thomas 
Published: December 2007

ABSTRACT
In recent years heavy oil operators in California have been required to meet increasingly stringent Air Pollution Control District Regulations, especially regarding NOx emissions associated with Thermal Enhanced Oil Recovery (TEOR) projects. This has resulted in the employment of state-of-the-art NOx control techniques. Of the currently known NOx reduction techniques investigated by TEOR operators, low NOx burners have been most frequently utilized to date. Generally, low NOx burner manufacturers design and construct their burners for a specific set of assumed operating conditions. However, in actual field applications these conditions are not always met, resulting in performance inconsistencies. Field testing has demonstrated that the overall NOx performance of a system is quite sensitive to operational changes. Through applied technology, optimum emission performance can be achieved.
Drain Hole Drilling-An Old Idea Whose Time is Now
Authors: Hyland Craig R. 
Published: December 2007

ABSTRACT
The drilling of horizontal laterals from vertical bores for the production of crude oil has been the subject of recurrent interest for more than a century. Often touted as a cure-all for declining or marginal wells, the use of drainholes has shown some notable successes in spite of deficiencies in technology and the lack of strong economic incentives. Modern engineering's knowledge of reservoir behavior can greatly increase the success of drainhole completions for diverse applications. Today's energy environment offers substantial economic incentives which, together with technological expertise, dictate the wider application of drainhole drilling and production technicques in todays oil and gas industry.
The Technology of Drilling in 7,500 Ft of Water
Authors: Johnson A. S. , Smith G. D. 
Published: December 2007

ABSTRACT
Deep water drilling technology has progressed rapidly since 1965 when the first wells were drilled in Water depths greater than 600 feet (183 m). Since the advent of dynamically positioned drilling vessels in the early 1970's, the move toward deeper waters has seen continuous progress. The state of the art of present day technology in deep water has been demonstrated by Shell Offshore, Inc., utilizing the Discoverer Seven Seas drillship which is currently rated for operations in 7500 feet (2286 m) of water.
Some of the major factors addressed by Shell Offshore, Inc., and Sonat Offshore Drilling Inc., in order to successfully explore for hydrocarbons in 7500 feet (2286 m) of water are the subject of this paper. These include marine riser, BOP controls and station keeping systems. The topics of riser tension required in deep water, riser hangoff requirements and riser recoil systems are discussed. Blowout preventer stack strength, the integration of two different types of positioning systems and reentry techniques are also important and to some extent not previously addressed.
The significance of this technology is that it is specialized to the extent that only one Operator, with its partners, is actively drilling in ultra-deep waters and only one rig is fully capable of completing a 7500 feet (2286 m) water depth drilling program. A tremoundous commitment of resources from Shell Offshore Inc., has resulted in this ability which is clearly on the leading edge of drilling technology.
The Cascade Method for Accelerated Convergence in Implicit Simulators
Authors: Appleyard John R. , Cheshire Ian M. 
Published: December 2007

ABSTRACT
Several iterations may be required when Newton's method is used to solve the fully-implicit reservoir simulation equations. This paper presents a new technique, called "Cascade", to complement the standard Newton method and minimise the number of Newton iterations required at each timestep. The method exploits the use of upstream relative permeabilities to compute saturations one cell at a time, starting with the cell of highest potential and proceeding down the potential sequence to the cell of lowest potential. The power of the technique is demonstrated for highly non-linear problems containing strong counterflow and with saturation fronts advancing through many cells in a single timestep.
Hydrologic Applications Of Lithofacies Clastic-Ratio Maps
Authors: Pettyjohn Wayne A. , Randich P.G. 
Published: December 2007

Abstract
A sequence of lithofacies clastic-ratio maps will reveal the stratigraphy of an aquifer. The use of these maps in conjunction with a study of the water-level fluctuations of wells and streams will aid in determining the relationship of surface water and ground water. In addition, these maps should indicate boundaries and water-table or artesian conditions of aquifers. They may also provide information concerning changes in quality of ground water.
Introduction
Lithofacies maps in combination with several types of ratio maps have been used in stratigraphic studies for many years. The value of these maps for the interpretation and reconstruction of paleogeography is unquestioned. Until the present, however, this concept of map making has not been utilized to a great extent for geohydrologic purposes. Hydrologists have the benefit of numerous complex formulas to be used in the determination of aquifer characteristics but the concept of an aquifer "constant in thickness, infinite in areal extent, homogeneous and isotropic" is one that normal does not exist in nature. Obviously, if aquifer characteristics are dependent on the structure, composition, and lateral and vertical changes in lithology of any water-bearing zone, then one must first determine as accurately as possible the, geology and then select the hydrologic formula that best conforms to the total picture. The collection of hydrologic data by means of pumping or aquifer tests is an expensive and time-consuming process.