bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wettability Effects on Oil Recovery Mechanisms in Fractured Reservoirs
Authors: Graue A. , Bognø T. 
Published: December 2007

Abstract
Iterative comparison between experimental work and numerical simulations has been used to predict oil recovery mechanisms in fractured chalk as a function of wettability. Selective and reproducible alteration of wettability, by aging in crude oil at elevated temperature, produced chalk blocks which were strongly-water-wet and moderately-water-wet, but with identical minerology and pore geometry. Large scale, nuclear-tracer, 2D-imaging experiments monitored waterflooding these blocks of chalk, first whole, then fractured. This data provided in-situ fluid saturations for validating numerical simulations and evaluating capillary pressure- and relative permeability input data used in the simulations. Capillary pressure and relative permeabilities at each given wettabilities were experimentally measured and used as input for the simulations. Optimization of either Pc- data or kr-curves gave indications of which of these input data could be trusted. History matching both the production profile and the in-situ saturation distribution development gave higher confidence in the simulations.
Effects of Organic Acids and Bases, and Oil Composition on Wettability
Authors: Skauge A. , Standal S. , Boe S. O. , Skauge T. , Blokhus A. M. 
Published: December 2007

Abstract
Correlations between acid and base numbers, crude oil composition and wettability for crude oil/water/quartz systems have been investigated. Twelve North Sea crude oils were characterised with respect to asphaltene content and composition of saturates, resins and aromatics by the use of thin liquid chromatography. Acid and base numbers were measured for each crude oil. The acid numbers varied from 0.02 to 2.8, while the base numbers were in the range of 0.3 to 1.6.
One of the crude oils was separated into asphaltenes and deasphaltened oil, measuring acid and base number for both fractions. Based on different acid and base contents three of the oils were chosen for adhesion tests and contact angle experiments on quartz surfaces as a function of pH. These crude oils were also investigated with respect to interfacial activity.
The amount of acids and bases was found to be proportional to the amount of polars (NSO and asphaltenes). The acid and base numbers were correlated, meaning that a high acid number usually corresponded to a high base number. For the fractionated oil the deasphaltened oil was found to contain approximately equal amounts of acids and bases as the original crude oil. The results from contact angle measurements show more water wet surface at higher acid number, and more oil wet behaviour at higher base number. The interfacial tension of the crude oil/brine interface increased with increasing base/acid ratio.
Network Modeling to Predict the Effect of Wettability Heterogeneities on Multiphase Flow
Authors: Laroche C. , Vizika O. , Kalaydjian F. 
Published: December 2007

Abstract
In gas injection processes it has been already shown that the wettability characteristics of the solid surface and the spreading characteristics of the fluid system hold the key roles. Network modeling has proved to be a useful tool to phenomenological studies of multiphase flow. The objective of the present paper is to describe a network model of three- phase flow in porous media with heterogeneous wettability. Experimental support to validate the model is provided in the study by Laroche (SPE 52067) using micromodels with different wettability patterns.
The developed numerical tool is used to demonstrate the impact of small scale wettability heterogeneities on gas injection efficiency, for various patterns and spatial heterogeneity distributions. The model permits to impose heterogeneous wettability by assigning different water/oil contact angles according to the desired heterogeneity pattern. The initial distribution of oil and water in the network is established by simulating a two-phase displacement, which corresponds to a drainage in the water-wet region and to an imbibition in the oil-wet region. When gas is injected, three phases coexist within the network. The three-phase displacement is dominated by drainage mechanisms. Oil is assumed to flow through wetting films in the oil-wet regions and through spreading films on water in the water-wet regions. The simulations clearly demonstrate the effect of the size and distribution of wettability heterogeneities on water/oil displacement and three-phase gas injection. Also the effect of wettability heterogeneities distribution on water/oil capillary pressure is investigated by simulating quasi-static displacements.
Effect of Capillary Forces on Immiscible Displacement in Porous Media
Authors: Dong M. , Dullien F. A. L. 
Published: December 2007

Abstract
The complete fractional flow equation obtained previously by the authors from capillary models of both counter-current and co-current imbibition has been solved numerically, together with the mass conservation equation of water to obtain saturation profile histories in waterfloods in models of lengths ranging from lm to 200m, at an injection rate of 10−4cm/s. The saturation profiles change from near horizontal in the lm long model to near piston like in the 200m model. Equivalent roles are played by model length and by water injection rate in determining saturation profile history. Calculated saturation profiles match those determined in the laboratory when plotted against dimensionless distance coordinates. The complete and the simplified fractional flows, derived from calculated saturation profiles, have been compared: unlike the former ones, the latter are s-shaped curves. It is demonstrated with the help of the simple capillary model of imbibition that development of the Buckley-Leverett front under conditions when viscous forces dominate is nevertheless due to capillary forces. Capillary pressure gradient in the fractional flow equation can be neglected only at very low interfacial tensions when the relative permeability curves become straight lines. Multiple-valued saturation profiles are obtained from physically inconsistent simplified fractional flow equation in which the capillary pressure gradient is neglected but relative permeability data obtained under conditions of non-negligible capillarity are used.
A Simplified Approach to Geochemical Modeling and Its Effect on Well Impairment
Authors: Araque-Martinez A. , Lake Larry W. 
Published: December 2007

Abstract
Solids can easily cause impairment of wells by plugging flow channels. A source of these solids is the dissolution and subsequent precipitation of minerals caused by transport of fluids out of equilibrium with the host formation. To model these geochemical processes, allowing for the transport of fluids with kinetic reactions, it is necessary to solve the mass balance equations for each component flowing in the medium. This work presents a new approach, based on the method of characteristics (MOC), to greatly simplify these solutions. Based on this solution technique, we build a model that includes kinetic (aqueous-solid) as well as equilibrium (aqueous-aqueous) reactions. We define new dimensionless groups to scale the solution. Unlike many previous geochemical models, we focus on flow that is substantially out of local thermodynamic equilibrium.
The MOC model has been tested against results from the more general geochemical KGEOFLOW simulator and against experimental literature data. Results match the KGEOFLOW solution closely, but computing time is reduced at least 50 times. The MOC model can run quite general geochemical problems on a desktop personal computer. We applied the MOC model to a radial flow around a well to study the effect of precipitation, supersaturation, and dissolution on injection well impairment. We focussed on cases in which there was substantial well impairment in calculations based on local thermodynamic equilibrium. Results show that, at certain rates, a well's injectivity can be impaired, though the damage will be less severe than when local thermodynamic equilibrium is assumed. However, injection rates must be unrealistically large to completely prevent damage.
Calibrate Flow Simulation Models with Well-Test Data to Improve History Matching
Authors: He Nanqun , Chambers K. T. 
Published: December 2007

Abstract
In this paper we present a methodology to verify and update geostatistically based reservoir models using numerical simulation and automatic history matching of well-test data. A Bayesian estimation technique provides the framework for the inversion procedure used to update reservoir models. A restricted-step Gauss-Newton method and an extension of Carter's method for sensitivity coefficients make the methodology efficient and practical. Reservoir models (permeability, porosity and skin factor) can be updated based on individual simulation cells, geological feathers, or on constant multipliers applied in the well-test radius of investigation. When short-term well-test data is available from many wells, we found it useful to calculate property multipliers around each well and then interpolate the multipliers to unsampled areas in the reservoir.
Field examples demonstrate the utility of conditioning reservoir models with well-test data. In the examples, flowing bottomhole pressure mismatches are as high as 2000 psi and core based permeabilities deviate by two orders of magnitude from the well-test results. After conditioning to well-test data, pressure mismatches are significantly reduced, permeabilities are updated to the correct magnitude, and the skin factor closely matches the classic well-test analysis result.
We applied our updating methodology to a full-field simulation study on a large carbonate reservoir. Comparisons of historical pressure and production data to the updated full- field model demonstrate good agreement.
Effect of Pressure Uncertainty on Material-Balance Plots
Authors: Walsh Mark P. 
Published: December 2007

Abstract
Straight-line material-balance plots are routinely used to ana- lyze reservoir performance and estimate the OOIP and OGIP. Application necessarily requires average reservoir pressure measurements. Invariably, these measurements are subject to error. This paper presents a statistical analysis of the effects of pressure uncertainty on the practical applicability of these plots.
Results reveal that pressure uncertainty can drastically affect the reliability of certain plots. While all proposed plots are theoretically valid, certain plots are practically and categorically flawed because they require virtually error- free pressure measurements—a practical impossibility. The problem is further exacerbated by the observation that flawed and valid plots alike yield the same apparent linear character. This observation has lulled practitioners into a false sense of confidence that the flawed plots are meaningful and applicable. The plots are ultimately classified in terms of their error tolerance and sensitivity. The hypersensitive plots should be avoided.
A New Approach to the Analysis of Gas-Well Performance With Periodic Interruptions
Authors: Helmy M. Wael , Wattenbarger R. A. 
Published: December 2007

Abstract
This paper presents several techniques for the analysis of monthly production data of gas wells producing at constant bottomhole pressure from linear reservoirs, and subjected to periodic shut-ins. The frequent well interruptions cause severe scatter in the production data, which hinders the analysis using conventional methods: specialized-plots, deconvolution, etc...
We propose two different approaches to the analysis. First, we present an application of the superposition principle to identify an analytical reservoir model that gives a bottomhole pressure response similar to that observed in the field. The model is used to locate reservoir boundaries, calculate reservoir parameters and estimate the gas in place.
Second, we present a new analytical solution for the production rate following a shut-in period. The analytical solution is used to filter out the scatter in production data and establish the production trend had there been no production interruptions.
The first analysis technique is applicable to linear bounded reservoirs. However, the second method is limited only to linear infinite-acting reservoirs. Two field examples are given to illustrate the use and validity of the proposed methods.
Managing Uncertainties on Production Predictions Using Integrated Statistical Methods
Authors: Dejean J. P. , Blanc G. 
Published: December 2007

Abstract
Reservoir engineering requires to manage many sources of uncertainties that can be classified in two categories : (a) uncontrolled uncertainties on the physical reservoir description parameters and (b) controlled uncertainties on the reservoir development scheme parameters. In this context engineers must answer several problems : describe prior uncertainties, identify the ones that actually influence the oil production process, make safe production forecasts and optimize the reservoir production scheme.
In this paper, several statistical methods dealing with these problems are presented. They are (a) Experimental Design, (b) Response Surface Methodology and (c) Monte-Carlo methods. Integrating these techniques enables to build a simplified model of a process and to estimate the uncertainties on the response predictions. The entire procedure was applied to a field case showing both types of controlled and uncontrolled uncertainties. The result is a new frame allowing engineers to quantify uncertainties on the reservoir production forecasts conditionally to uncertainties on the reservoir modeling parameters. The procedure has lower computational costs than the traditional one but is quite complex and needs adapted software to be used by reservoir engineers.
Local Geomagnetic Field Modelling Closes the Gap Between MWD and Gyro Directional Surveying
Authors: Waag Tor Inge , Torkildsen Torgeir , Inderhaug Odd Helge , Carlsen Inge M. 
Published: December 2007

Abstract
A method for estimation of the influence of local geomagnetic anomalies on magnetic directional surveys has been developed. The method has been verified by comparisons between gyro and magnetic positioning.
The method relies upon aeromagnetic survey data, and estimates the 3 components of the local geomagnetic field along the wellpath from field data at flying altitude, and from downward continuation of the field data to reservoir depth. The field components can be predicted at depths down to the shallowest magnetic layer, and applied to enhance the accuracy of magnetic surveying. With access to core data the influence of magnetic material above the reservoir can also be included.
A comparison has been run with real magnetic and gyro data from 11 wells at 3 different fields offshore Norway. The results indicate a reduction in lateral position uncertainty by 50% typically. This is very significant when trying to hit small targets.
The method has been tested by major service companies and will soon be available as a part of their drilling services. This will benefit drilling with tight tolerances, especially in areas with large local magnetic anomalies such as the North Sea and Arctic regions. Local field strength anomalies can exceed 500 nanoTesla, declination errors can be more than 2 degrees and dip errors more than 0.5 degrees in these areas. The lateral position difference between magnetic and gyro surveying has been reduced from 20-50 m to 1-25 m in actual cases. The method has so far been applied in post-processing to verify the results, and is now being applied while drilling for correction of surveys.
Development for Acoustic Sensing System Ahead of the Bit for Detection of Abnormally High-Pressured Formation
Authors: Sugimura Yuzo , Masukawa Toru , Yonezawa Tetsuo , Hattori Shinichi , Taniguchi Ryosuke , Shimada Takashi 
Published: December 2007

Abstract
Japan National Oil Corporation, Technology Research Center (JNOC/TRC) Drilling and Completion Laboratory, has developed a technology which was able to measure formation velocity ahead of the bit in collaboration with Mitsubishi Electric Corporation.
In this paper, we are going to introduce you the research and development efforts enforced since 1996 to 1998 for establishing a sensor system to detect abnormal high-pressure zone while drilling. The system employs longitudinal elastic wave to detect formation boundary ahead of the bit, and measure formation velocity with distance to the boundary precisely. The system will give further prospect and detect abnormal high-pressure zone based on the formation velocities obtained there.
A New Platform for Attitude Determination and Declination Correction
Authors: Morsy Hatem , Estes Robert 
Published: December 2007

Abstract
Conventional directional measurement methods for MWD and Survey systems rely on measurement of the borehole orientation relative to the geomagnetic field. The borehole orientation can then be referred to the geographical coordinate system from the knowledge of the magnetic field orientation relative to True North and the horizontal plane. Calibration of the directional sensors relies on knowledge of the Geomagnetic Field intensity.
The geomagnetic field intensity is obtained annually from look up tables referred to as the British Geological Survey Model (BGSM) taken as a function of time and location. However, the Earth's Magnetic Field is not stable and may have noticeable, short term fluctuations due to diurnal variations, proximity to masses of magnetic material, local anomalies originating in the upper mantle, crust, or surface, and other phenomenon like solar activities. As a result, declination calculation and magnetic survey measurement will not be as accurate as they seem to be in most cases for the above mentioned reasons.
This new method is introduced to measure the local earth magnetic field, local magnetic dip angle, apparatus platform orientation with respect to the axis of the earth local magnetic field, the roll and tilt of that platform, and its longitudinal axis with respect to true north. This is done using the following combination of sensors: Inertial Motion Reference Unit (IMRU)tri-axial magnetometertri-axial accelerometerGlobal Positioning System (GPS) receiver antenna matrix.
Based on these measurements, an accurate declination calculation can be performed in real time. Thus, performing magnetic corrections and detection of magnetic anomalies can then be compensated. This is particularly critical in high latitude locations.
Very promising results were obtained through lab testing in Houston and Field Testing in Canada (the system shows excellent added value in high latitude locations).
This paper presents the results of the lab and field testing of the system that will be of great value to the drilling industry due to the enhanced accuracy provided by the system.
Dynamic Simulation of the Europa and Mars Expansion Projects: A New Approach to Coupled Subsea and Topsides Modeling
Authors: Lamey M. F. , Schoppa W. , Stingl K. H. , Turley A. J. 
Published: December 2007

Abstract
Accurate computational modeling of time-dependent flow in petroleum production systems - Dynamic Simulation - remains a crucial ongoing effort within Shell to identify and implement significant improvements in facility design and operation, particularly for Deepwater applications. To date, dynamic simulations of topsides processing facilities have been decoupled from flow transients in wellbores and subsea flowlines. An innovative approach to full-system dynamic modeling has been developed for the Mars Tension Leg Platform to accommodate production from the Europa Subsea Project that will utilize an existing topsides model and interface to an expanded topsides facility and subsea system flow model. The resulting simulation is unprecedented in scope and size, providing full thermal-hydraulic data from the sand face to the export pipelines. Despite the impressive scope of the model, its cost is reasonably low in relation to the total engineering effort. The dynamic interface consists of (i) OLGA simulation of transient multiphase flow in four subsea wells (with individual reservoir characteristics) and dual pipe- in-pipe insulated flowlines (20 mile offset), coupled to (ii) OTISS simulation of Mars topsides production equipment, including parallel compressor trains, multi-stage separators, oil export pumps, and numerous control valves, in addition to chemical injection umbilicals and well annulus vent facilities.
The principal goals of this integrated modeling approach were to identify, understand, and control unique transient operating conditions, including implications of varying field characteristics. Hence, this dynamic model is a powerful tool for (i) validating facility design, (ii) training of operations personnel (including elimination of surface/sub-surface communication barriers), and (iii) for optimization in surveillance planning. In fact, preliminary model results have revealed the necessity for some important modifications of facilities and operating procedures. Using the model in this fashion allows the engineer to reduce uncertainty factors in the design, which then lead to lower capital costs and/or operating expenses. A survey of the model's functionality is presented and discussed, including, but not limited to, well start-up and flowline blowdown.
The Effect of Side Arm Diameter on Phase Split at T-Junctions
Authors: Azzopardi B. J. 
Published: December 2007

Abstract
The effect of the ratio of side arm to mian pipe diameter on phase maldistribution during the division of gas/liquid flow at T-junctions is illustrated using data from experiments at two scales. The similarity and differences between data from different sources is highlighted. The ability of published models to predict the phase split is tested and possible sources of the shortcomings of the models are identified.
Advances in Liquid/Liquid Centrifuge Design Provide New Options for Petroleum Production
Authors: Meikrantz D. H. , Macaluso L. L. , Flim W. D. , St. George M. M. 
Published: December 2007

Abstract
Recent advances in liquid-liquid centrifuge design coupled with experience gained in separating water from oil and oil from water provides a powerful, new option for petroleum production. The annular centrifugal contactor is a vertical, liquid-liquid, direct drive, low speed centrifuge that is capable of both mixing and separating in a single unit. Further design improvements which enhance this centrifuge's utility and efficiency in two-phase liquid separation are a low mixing sleeve and a clean-in-place rotor. Using the low mix mode, oil in water concentrations at the centrifuge outlet are typically in a range of 20 to 200 ppm, dependent upon the process conditions. Water in oil levels of less than 1% can be reached in heavier oil stocks and are even lower for light crudes and refined products. This new design is capable of processing input oil-water ratios which vary from 0–100% without adjustment. This important advancement is possible because, in this design, the oil-water interface can shift position within the separating zone of the rotor without causing a loss of separation quality. A clean-in-place (CIP) option consisting of numerous spray nozzles installed in the rotor's central hollow shaft is employed to deliver a cleaning solution to the inside diameter wall for rapid and efficient solids removal. The entire process can be automated to clean multiple centrifuges, sequentially, requiring only five minutes per unit. Examples of applications for this technology include; single stage oil dehydration, de-oiling process water, desalting of oil via washing, and other custom liquid-liquid processes.