bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Use of Real-Time and Time-Lapse Logging-While-Drilling Images for Geosteering and Formation Evaluation in the Breitbrunn Field, Bavaria, Germany
Authors: Rohler Hendrik , Bornemann Ted , Darquin Alexis , Rasmus John 
Published: December 2007

Summary
Six horizontal wells were drilled into the Tertiary Chatt Sand reservoir of the Breitbrunn gas field in Bavaria, Germany. The purpose of this campaign was to develop part of the depleted reservoir into a gas-storage sand. A detailed geological and petro-physical study was prepared before drilling and resulted in the identification of high-quality reservoir layers that were targeted by the horizontal wells. Despite the simple anticline structure of the field, geometric drilling was ruled out because of remaining geological and directional uncertainties. The geosteering approach adopted relies on real-time resistivity-at-bit images, which were used for the first time during this drilling campaign. The image data are compressed downhole and transmitted to the acquisition computer on the rig, where they are decompressed and analyzed. The images allow the precise placement of the borehole relative to the geology. Layer heterogeneity such as tight streaks, concretions, or patchy porosity can be identified as such and is not interpreted as a different layer entered by the hole, which would lead to a wrong geosteering decision. Logging-while-drilling (LWD) azimuthal data are acquired during drilling and during washdown passes that follow a bit change. A comparison of these time-lapse data sets can provide invasion profiles through time and around the borehole.
Reaction Kinetics of In-Situ Combustion: Part 1—Observations
Authors: Fassihi Mohammad Reza , Brigham William E. , Ramey Henry J. 
Published: December 2007

Abstract
Continuous analysis of produced gases from a small packed bed reactor, at both isothermal and linearly increasing temperatures, has shown that combustion of crude oil in porous media follows several consecutive reactions. Molar carbon dioxide/carbon monoxide (CO2/CO) and apparent hydrogen/carbon (H/C) ratios were used to observe the transition between these reactions at different temperature levels.
A new kinetic model for oxidation of crude oil in porous media is presented in Part 2 of this paper (Page 408).
Chemical Characterization Problems of Water-Soluble Polymers
Authors: Tyssee D. A. , Vetter O. J. 
Published: December 2007

AbstractWater-soluble polymers are being used increasingly in oil, gas, and geothermal production. Applications include drilling, stimulation, workover and completion, and reservoir flooding fluids. The development of polymers and their application has been mostly empirical. Such a course of development was suitable in the past. However, empirical techniques do not satisfy present and future needs which include (1) the cost/performance relationship and (2) environmental effects associated with expanding polymer application. Therefore, a more thorough understanding of the polymer chemistry is required.The first step in doing this is to develop laboratory methods to characterize these complex materials and their degradation products. The problems are (1) understanding polymer chemistry under field conditions and (2) developing analytical procedures. These problems emerged dramatically during analysis of recent fracture stimulation of some geothermal wells. An involved study of the potential analytical methods was conducted. Polysaccharides were used for the actual field fracture jobs as well as for the analytical procedures. Correlations were made between the total organic content and carbohydrate content of the return waters as a function of residence time under simulated reservoir conditions. Preliminary indications are that more sophisticated information can be obtained by the use of emerging analytical techniques such as high pressure liquid chromatography (HPLC).Advantages gained from use of these methods and others are discussed.
Prediction of Viscosity for Partially Hydrolyzed Polyacrylamide Solutions in the Presence of Calcium and Magnesium Ions
Authors: Ward J. S. , Martin F. David 
Published: December 2007

Abstract
Loss of solution viscosity in water of increasing ionic strength is a major problem encountered in the use of the partially hydrolyzed polyacrylamide polymers for improved oil recovery. It is recognized widely that the viscosity loss is more drastic in the presence of multivalent cations than is observed for sodium ions. There is, however, little information available on the relationships between total ionic strength, concentrations of multivalent cations, and solution viscosities.
The purpose of this study is to establish relationships between total ionic strength, concentration of calcium or magnesium ions, polymer concentration, and the resulting viscosity for partially hydrolyzed polyacrylamides with varying degrees of hydrolysis. Solutions at constant ionic strength with varying ratios of calcium or magnesium to sodium ions are compared, and the loss of viscosity as a function of the fraction of divalent cations in the system is determined. For shear rates in the power-law region, the fractional loss in viscosity is a function of the fraction of multivalent cations and, in the range studied, is independent of the total ionic strength. A more complicated relationship is found at lower shear rates where the fractional viscosity loss does vary with total ionic strength.
The relationship in the power-law region should prove valuable in predicting viscosities on the basis of the dependence of viscosity on ionic strength and on multivalent cation concentration at a single ionic strength, eliminating the need for many individual measurements of viscosity. More work is needed before useful predictions will be possible at lower shear rates.
Phase Behavior and Properties of a Petroleum Sulfonate Blend
Authors: Bae J. H. , Petrick C. B. 
Published: December 2007

Abstract
A sulfonate system composed of Stepan Petrostep™ 465, Petrostep 420, and 1-pentanol was investigated. The system was found to give ultralow interfacial tension against crude oil in a reasonable range of salinity and sulfonate concentrations. It also was found that sulfonate partitioned predominantly into the microemulsion phase. However, a significant amount also partitioned into water and, at high salinity, into the oil phase. On the other hand, the oil-soluble 1-pentanol partitioned mostly into oil and microemulsion phases.
The interfacial tension between excess oil and water phases was ultralow, in the range of 10−3 mN/m. The tensions were close to and paralleled those between the middle and water phases. The trend remained the same even when the alcohol content changed. This means that in the salinity range that produces a three-phase region, below the optimal salinity, the water phase effectively displaces both oil and middle phases, even though the oil may not be displaced effectively by the middle phase. The implication is that, from an interfacial tension point of view, the oil recovery would be more favorable in the salinity range below the optimal salinity with the mixed petroleum sulfonate system used here. This was confirmed by oil recovery tests in Berea cores. It also was concluded that the change in viscosity upon microemulsion formation might have a significant influence on the surfactant flood performance.
A Chemical Theory for Linear Alkaline Flooding
Authors: deZabala E. F. , Vislocky J. M. , Rubin E. , Radke C. J. 
Published: December 2007

Abstract
A simple equilibrium chemical model is presented for continuous, linear, alkaline waterflooding of acid oils. The unique feature of the theory is that the chemistry of the acid hydrolysis to produce surfactants is included, but only for a single acid species. The in-situ produced surfactant is presumed to alter the oil/water fractional flow curves depending on its local concentration. Alkali adsorption lag is accounted for by base ion exchange with the reservoir rock. The effect of varying acid number, mobility ratio, and injected pH is investigated for secondary and tertiary alkaline flooding.
Since the surface-active agent is produced in situ, a continuous alkaline flood behaves similar to a displacement with a surfactant pulse. This surfactant-pulse behavior strands otherwise mobile oil. It also leads to delayed and reduced enhanced oil recovery for adverse mobility ratios, especially in the tertiary mode. Caustic ion exchange significantly delays enhanced oil production at low injected pH.
New, experimental tertiary caustic displacements are presented for Ranger-zone oil in Wilmington sands. Tertiary oil recovery is observed once mobility control is established. Qualitative agreement is found between the chemical displacement model and the experimental displacement results.
Modeling of a Micellar/Polymer Process
Authors: Bang Hwi W. , Caudle Ben H. 
Published: December 2007

Abstract
A highly implicit, multidimensional, multicomponent, multiphase, unsteady-state flow model has been formulated to simulate a micellar/polymer process. Unlike most compositional approaches, the proposed model accounts for capillary pressure. In addition, the model describes the unsteady-state flow of fluids and accounts for additional pressure- and concentration-dependent variables such as average mass velocity, effective dispersivity, and FVF that most compositional models do not. Numerical solutions to this model are obtained by a finite-difference method. For a one-dimensional (ID) case, the system is treated in terms of five pseudocomponents and two mobile phases. The proposed model is represented by a system of nonlinear partial differential equations in the dependent variables, component concentrations, and phase pressures. The model incorporates the process variables. These include those mentioned above plus interfacial tension (IFT), relative permeability, partition coefficient, adsorption concentration, and viscosity. The model was validated by history-matching with a laboratory core displacement test. The agreement of the numerical results and laboratory results shows the model's reliability and gives a realistic insight into its usefulness as a multidimensional, multicomponent, multiphase simulator. After testing, the model was used to investigate the effect of variations in the input parameters on the production history.
Effect of Burial History on the Subsurface Horizontal Stresses of Formations Having Different Material Properties
Authors: Prats M. 
Published: December 2007

Abstract
Although current mechanical properties of formations may provide rough estimates of subsurface horizontal stresses, they are inadequate to ascertain which of two adjacent formations has the higher horizontal stress. Temperatures, creep, and changes in material properties and strain during burial have a significant influence on today's state of stress.
Xanthan Gum—A Lyotropic, Liquid Crystalline Polymer and its Properties as a Suspending Agent
Authors: Salamone J. C. , Clough S. B. , Salamone A. Beal , Reid K. I. G. , Jamison D. E. 
Published: December 2007

Abstract
A variety of polysaccharides have been used in drilling fluids,1–4 and some of these polymers have been studied in tertiary recovery. Of particular interest in both these areas has been xanthan gum, the extracellular polysaccharide produced by Xanthomonas campestris, because of its relatively stable viscosity properties as a function of salt concentration, pH, temperature, and shear degradation. Indeed, no synthetic polymer or any other commercially available, naturally occurring polymer, or polymer derivative has been able to duplicate the solution behavior of xanthan gum.
During a study of xanthan gum's ability to suspend barium sulfate, it appeared that xanthan gum in aqueous solution at relatively low concentrations could have lyotropic liquid crystalline behavior. Behavior of this type has been noted for other biopolymers5 and recently has been demonstrated for various cellulose derivatives.6–10 An anisotropically ordered polymer solution would be extremely difficult to reproduce synthetically but could explain most of the unique properties of xanthan solutions.
To test the possibility that xanthan gum could have liquid crystalline order, a variety of xanthan solutions of various polymer concentrations in the presence and absence of various salts were studied under a polarized light microscope (100X). With solutions from 2 to 10% (wt/vol) xanthan gum in distilled water at room temperature, birefringent, ordered domains were observed at 10% concentration, with a decrease in birefringence as the polymer concentration decreased. At 2% concentration, no birefringence was observed, indicating the apparent area of change from an isotropic to an anisotropic phase. This point appears to occur at 2.9% by optical determination. In fact, this value could be considerably lower as revealed by other techniques for anisotropic xanthan solutions.8–10 For the 10% solution of xanthan gum, heating in a roller oven at 150°F (66°C) for 2 hours did not diminish the birefringence. Similarly, when a 10% xanthan gum solution was prepared in 10% KCI and in 33% CaCl2 solutions, birefringence was not decreased.
Effects of Impurities on Minimum Miscibility Pressures and Minimum Enrichment Levels for CO2 and Rich-Gas Displacements
Authors: Metcalfe R. S. 
Published: December 2007

Abstract
Multicontact miscible displacement processes are becoming increasingly popular as a means of recovering secondary and tertiary oil reserves in the U.S. and Canada. Economics of multicontact miscible flooding are governed to some extent by the availability of large sources of high purity CO2 or suitable liquefied petroleum gas (LPG) streams. This is because achievement of miscibility depends on the solvent composition as well as the system temperature and pressure. Atypical components in a CO2 or solvent stream therefore may increase the required pressure or enrichment levels for achievement of miscibility.
Several papers have been published discussing the pressure (for CO2) and composition (for rich gas) levels required for miscible displacement. The potential CO2 supply could be increased if complicated cleanup procedures for injected and produced fluids were not required. For engineering studies it is important that CO2 streams containing H2S and hydrocarbons be evaluated for their miscible flooding potential. It is also important to evaluate the effects of CO2 and C5 + components in rich gas mixtures to determine whether they can be used to reduce calculated enrichment levels for solvent systems.
This paper presents results of studies using mixtures of CO2, H2S, and C1, CO2-LPG, and rich gas solvents containing CO2 or C5 to displace oil miscibly in slim-tube experiments. The purpose of this work is to show the effects of various components on pressure and compositions required for miscibility. As expected, the changes in CO2 miscibility pressure are direct functions of temperature. It is reported that the addition of H2S and C2+ hydrocarbons lowers the miscibility pressure for CO2, whereas the presence of C1 in a CO2 solvent increases it. More important, the results give a quantitative titative measure of the degree of reduction/elevation in miscibility pressure to be expected with impure CO2 streams. The paper also presents similar results from displacements with typical rich gas solvents mixed with CO2 and/or C5. It is reported that CO2 increases the minimum enrichment required, while a heavier hydrocarbon component actually can reduce anticipated enrichment levels.
Computation of Multiphase Equilibrium For Compositional Simulation
Authors: Mehra Rakesh K. , Heidemann Robert A. , Aziz Khalid 
Published: December 2007

Abstract
A numerical scheme has been developed for calculation of multiphase equilibria. The scheme is applied to a thermodynamic model that employs a modified version of the Peng-Robinson equation for all phases except possibly an aqueous phase. Henry's constants are used for computation of solute fugacities in the water phase. The numerical scheme makes "optimal" use of first-and second-order iterative schemes and circumvents the problems reported by previous investigators. An outline of the scheme is presented with references to other sources where complete details are available. Examples of two-, three-, and four-phase separations are presented to demonstrate the range of the proposed scheme. Limited comparison with experimental data also is provided. The scheme may be embedded in compositional reservoir simulators for the modeling of oil recovery by such processes as hydrocarbon gas injection, nitrogen injection, and CO2 floods.
The Contribution of Logging Data to Sedimentology and Stratigraphy
Authors: Serra O. , Abbott H. T. 
Published: December 2007

Abstract
Until recently, the lithology and sedimentology of formations penetrated by a well could be studied only through the analysis of cores. Now a technique has been developed using multivariate analysis of logging data to give a high-resolution sedimentological description of any sequence of formations.
The number of different logs and their range allow determination of many of the physical characteristics of the rock.
The definition of a lithofacies has been extended by introducing the concept of an electrofacies, constructed on the basis of all the logging data at any depth interval. Thus, each logging datum is considered a descriptor for purposes of establishing electrofacies in a logged interval. Once established, electrofacies then can be correlated with actual geologic facies, if the logged interval has been cored.
Ion Exchange With Clays in the Presence of Surfactant
Authors: Hirasaki George J. 
Published: December 2007

Abstract
The transport of sodium and calcium through porous media in the presence of clays and surfactant has been calculated. The exchange of the cations with both the clays and the surfactant micelles is assumed to result entirely from electrostatic association. The results show that a system in which the preflood, slug, and drive have the same sodium and calcium concentration can have a significant increase in the calcium concentration in the surfactant bank and a significant decrease in calcium concentration in the drive because of ion exchange. A process with a salinity gradient design can have a decrease in calcium concentration in the surfactant bank compared with the injected slug because of ion exchange.
Evaluation of the Interfacial Tension Between a Microemulsion and the Excess Dispersed Phase
Authors: Ruckenstein E. 
Published: December 2007

Abstract
From a consideration of the thermodynamic stability of microemulsions, one can establish a relation between the interfacial tension y at the surface of the globules and the derivative, with respect to their radius re, of the entropy of dispersion of the globules in the continuous medium. Expressions for the entropy of dispersion are used to show that γ is approximately proportional to kT/re2, where k is Boltzmann's constant and T is the absolute temperature. Since the environment of the interface between the microemulsion and the excess dispersed medium is expected to be similar to that at the surface of the globules, these expressions are used to evaluate the interfacial tension between microemulsion and excess dispersed medium. Values between 10−1 and 10−3 dyne/cm that decrease with increasing radii are obtained, in agreement with the range found experimentally by various authors. The origin of the very small interfacial tensions rests ultimately in the adsorption of surfactant and cosurfactant on the interface between phases. The effect on the interfacial tension of fluctuations from one type of microemulsion to the other, which may occur near the phase inversion point, is discussed.
Applications for Polycrystalline Diamond Compact Bits From Analysis of Carbide Insert and Steel Tooth Bit Performance
Authors: Madigan J.A. , Caldwell R.H. 
Published: December 2007

Summary
A thousand field runs of typical roller cone and diamond drill bits were studied to form a comparative basis for assessing the impact of the polycrystalline diamond compact bit. Statistical analysis of mud log data was conducted on a formation-by-formation basis involving 2,581 data intervals. Baseline performance in general drilling was established, and key drilling situations for improved performance with the new bits were determined.

Introduction
During 1979, a study was conducted to document performance of specific commercially available drill bits in more than 1,000 actual field runs to form a comparative basis for assessing the impact of a new innovation - the polycrystalline diamond compact bit. Three basins were studied - the Williston and Permian basins in the U.S. and the North Sea basin. Sedimentary environments ranged from easily drilled, soft sediments to dense, extremely hard and abrasive rock, with an associated range of drilling practices and problems. Statistical analysis of data derived from mud logs was conducted on a formation-by-formation basis, involving 2,581 data intervals. The resulting information is a computerized bit performance data base detailing rate of penetration, footage, rotary hours, and key drilling parameters including mud properties, weight on bit, rotary speed, and rock type.
In addition to forming a baseline to evaluate performance of new bit designs, the study highlights key problem drilling situations where polycrystalline diamond compact bits can provide improved performance - e.g., overbalanced drilling, deviation control, high-rpm drilling, slim-hole drilling, and other applications. Actual testing of polycrystalline diamond compact bits in these applications has been in progress both in the U.S. and Europe, with favorable results to the baseline data. The paper outlines the study and offset comparisons of polycrystalline diamond compact bits with conventional bits in slim-hole drilling, oil-base fluids, pressure coring, and offshore drilling.
Early Development Efforts on Polycrystalline Diamond Compact Drag Bits
The U.S., consuming some 40% of the free world's oil production while producing only 19%, is faced with the challenge of rapidly boosting production to avoid increasing dependence on expensive foreign oil and the resulting consequences to the economy. This must result in more drilling. Drilling costs have increased at almost exponential rates, and the industry continually is looking to new technology to halt this trend. This new technology includes advances in drill bit design directed toward improving both overall performance and performance of specific designs in particular problem drilling situations.