bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduction of Grid Effects Due to Local Sub-Gridding in Simulations Using a Composite Grid
Authors: Quandalle P. , Besset P. 
Published: December 2007

ABSTRACT
Our previous paper [1] described and analyzed the performance and some of the advantages obtained when a reservoir simulator is upgraded with: the possibility of flow between any given grid blocks, especially from one to several blocks;a multiple time step calculation.
These improvements were appreciated by modelling engineers. The upgraded simulator was used for the simulation of actual reservoirs with complex geometry (such as faulted reservoirs), and for its possibility of having a composite discretization grid (i.e. a grid with several nested levels of local sub-gridding). This practical need justified further extensive study of the flow behaviour near a sub-gridding boundary in a composite grid.
Composite grids possess some features which do not exist in regular classical grids. In a regular grid system, when two blocks are neighbours in a certain direction, their grid centers are always drawn up in that direction. In a composite grid, this is not always the case for neighbouring blocks belonging to different levels of local sub-gridding. As a consequence, in a composite grid, approximation of material exchange between two blocks by the classical two point finite difference scheme may be less accurate than in a regular grid. Tests have shown that a significant grid effect may be induced by computing flows between neighbouring blocks belonging to different sub-gridding levels with this scheme. To eliminate these effects, a more sophisticated numerical scheme, involving more than two points, must be used for flow computation.
This paper reports an analysis of this phenomenon. It also gives a description of some schemes especially designed for this purpose. These schemes may be viewed as being the classical two point scheme with one of the two points being a grid point but not a grid block center. Reservoir data are then approximated at this new grid point by interpolating data values at the grid block centers. More or less sophisticated interpolations are considered. It also describes some numerical examples performed to compare these schemes when they are used for the simulation of multiphase flows with a composite grid. One of the schemes is selected for its accuracy, its reliability, and its simplicity. On numerical examples, it is shown to nearly reproduce, with a composite grid, results obtained with a fine regular grid having a much larger number of blocks. Moreover, this scheme is implemented on a black oil simulator using a Sequential Solution Method and designed for the simulation of three dimensional three phase flows in large reservoirs with composite grids and several thousands of blocks.
Averaging Laws for Flow Through Grid Blocks Containing Heterogeneities
Authors: Shaw D. C. , Dawe R. A. 
Published: December 2007

ABSTRACT
Many natural rock systems contain small patches of different permeability which affect the flow of fluids through them. As these heterogeneities become smaller and more numerous, they become harder to model numerically. We consider two dimensional flows through such systems, where each patch is many radii away from another. For finite numbers of heterogeneities, they can be replaced by single dipoles to leading order, and this approximation predicts a number of features of the flow. In some circumstances, the entire system can be described by assigning an average permeability tensor to it. Several infinite systems including vertical and horizontal bands are also considered, leading to quite simple expressions for the flow rate and average permeability. The theory is extended to the case where there is a small change in capillary pressure within each heterogeneity as well as a nearly-unit mobility ratio at the displacement front. First-order corrections for these effects are found and applied to the model.
Sparse Gaussian Elimination for Complex Reservoir Models.
Authors: Sherman A. H. 
Published: December 2007

ABSTRACT
The simulation industry is rapidly moving towards the frequent use of complex reservoir models including such features as faults, implicit well terms, and thermal or compositional effects. All of these things can pose great difficulties for the standard direct elimination methods typically found in reservoir simulators. This paper takes a new look at sparse Gaussian elimination methods in the context of the current technology and trends in simulation and computing. A novel implementation is described, and numerical results are presented that indicate that this implementation can be a more effective tool for simulation than previous versions of sparse elimination.
Constrained Residual Acceleration of Conjugate Residual Methods
Authors: Wallis J. R. , Kendall R. P. , Little T. E. 
Published: December 2007

ABSTRACT
This paper describes a new iterative technique for the solution of linear systems of equations arising in petroleum reservoir simulation. The procedure exploits a powerful, vectorizable preconditioner to accelerate generalized conjugate residual methods. Speed and robustness of the new method compare favorably with previously published schemes. These attributes will be demonstrated in actual applications.
Release and Deposition of Clays in Sandstones
Authors: Sharma M. M. , Yortsos Y. C. , Handy L. L. 
Published: December 2007

ABSTRACT
An attempt is made to prescribe conditions under which deposition or release of physically adhering clay particles occurs on pore walls in sandstones. Quantitative models for the physicochemical interactions between clay particles and pore walls are used to estimate rates of deposition and release in a single pore. It is found that the rates change rapidly from zero to a finite value governed only by the local Peclet number. This makes it possible to delineate regions in the ψ1 – ψ2 phase plane where deposition or release dominates. The onset of clay release or deposition is determined by these surface chemical parameters. However in the deposition or release dominated regimes, the actual rates are shown to be only functions of fluid pore velocity.
Since the surface electrostatic potentials ψ1 and ψ2 are crucial in determining the onset of deposition or release, they were experimentally measured. Ottawa sand, kaolin, and fired and unfired Berea sandstone samples were studied. The sandstone samples were disaggregated and separated into the oxide fraction and the clay fraction. Surface charges were measured on each as a function of pH and ionic strength. These experimental results in conjunction with the regions of deposition and release in the ψ1 – ψ2 phase plane were used to construct stability diagrams. The stability diagrams delineate regions in the pH – ionic strength phase plane where clays will be released from pore walls. These regions are referred to as regions of instability for the sandstone. The results obtained for Berea sandstone agree well with those reported earlier. Similar stability diagrams can be constructed when other species such as polyvalent cations or anions are present in the system. Some experimental results are provided here towards this end.
Bulk Gel Strength Tester
Authors: Meister J. 
Published: December 2007

ABSTRACT
A simple screen extrusion rheometer (Gel Strength Tester) was designed to quantitatively compare strong bulk gels of the compositions used for conformance improvement in near-wellbore treatments. In addition, this tester should be able to measure other strong gels, such as thick drilling muds.
To demonstrate this device, the strength of aluminum crosslinked polyacrylate-acrylamide copolymer type gels was measured as a function of the effects of gel age, sheared polymer, salinity, polymer concentration, intrinsic viscosity and percent anionic character. All gel systems investigated had a characteristic yield pressure, below which the gel could not be extruded, and also an apparent viscosity which was dependent on shear rate.
It may be possible to correlate bulk gel strength with permeability reduction in cores.
Graphical Prediction Of Waterfloods
Authors: Higgins R.V. , Boley D.W. , Leighton A.J. 
Published: December 2007

Abstract
A method using relative permeability curves is presented to determine in about 30 minutes by the use of a desk calculator and graphs the recovery vs. cumulative water-injected of linear and 5-spot waterfloods. The determinations for the linear model are nearly identical to, and for the 5-spot within an average of 2 percent of, those calculated by the electronic computer used in the Higgins and Leighton technique. The 5-spot results by the graphical method are also within an average of 5 percent of those for presently available experimental 5-spot waterfloods. The graphical method does not give, however, the time or rate of oil recovery. The procedure uses the fractional flow, or fw, curve from the relative permeability curves and uses Welge tangents to the fw curve. Cumulative water injection is calculated from the slopes of the tangents, and recovery is calculated using extension of tangents to fw=1 From these data, recovery vs. pore volumes injected for a linear waterflood are plotted.
Qualitative and Quantitative Analysis by High-Performance Liquid Chromatography of Synthetic Alkylaryl Sulfonates: Surfactants for Potential Application in Enhanced Oil Recovery
Authors: Pols P. D. , Agterof W. G. M. 
Published: December 2007

ABSTRACT
In chemical enhanced oil recovery methods such as surfactant flooding and steam-foam soaks or drives, surfactants are used to achieve low interfacial tensions or to make a viscous foam respectively. These products consist of a mixture of homologuous series of surfactant components, while each homologue contains isomers. A careful design of the surfactant system is required to tailor its composition to the characteristics of the reservoir in which it is to be applied. From this work a laboratory prototype surfactant mixture is produced which is the basis for a blend to be manufactured on a large scale. A quality control procedure is imperative in this stage. A direct approach is a comparison from a detailed analysis of the laboratory prototype and the product manufactured on a large scale. It has been shown before that high performance liquid chromatography (HPLC) is a very useful technique for this purpose.
We report on the separation by reversed-phase ion-pair HPLC of synthetic alkylaryl sulphonates into their individual components, which has been significantly improved by the modification of previously published experimental conditions. Good baseline separation of homologues can be reached and isomers can be easily recognised in the chromatograms. Specific UV detector response factors are reported, which enable reliable quantitative composition analysis of sharp cuts and blends.
The Effect of Inaccessible Pore Volume on Polymer Coreflood Experiments
Authors: Lötsch T. , Müller T. , Pusch G. 
Published: December 2007

ABSTRACT
Laboratory flooding experiments with polymer solutions in sandstone cores are usually performed for studying the mechanisms of polymer flooding processes, and for measuring the properties which describe the process. A determination of the slug profile of the polymer solution allows the measurement of retention characteristics while taking into account the portion of the pore volume not in contact with the polymer solution.
By means of a simple tracer test with the use of inorganic salts, the inaccessible pore volume for a xanthan-type and a scleroglucan-type polymer in highly saline brine was measured. The amount of inaccessible pore volume had to be considered in the determination of retention isotherms for these polymers in core flooding experiments. An analytical simulation model according to immiscible displacement theory was applied for simulating linear displacement experiments effectively by considering inaccessible pore volume and retention characteristics.
Gas Hydrates at Two Sites of an Active Continental Margin
Authors: Kvenvolden K. A. 
Published: December 2007

ABSTRACT
Sediment containing gas hydrates from two distant Deep Sea Drilling Project sites (565 and 568), located about 670 km apart or the landward flank of the Middle America Trench, was studied to determine the geochemical conditions that characterize the occurrence of gas hydrates. Site 565 was located in the Pacific Ocean offshore the Nicoya Peninsula of Costa Rica in 3,111 m of water. The depth of the hole at this site was 328 m, and gas hydrates were recovered from 285 and 319 m. Site 568 was located about 670 km to the northwest offshore Guatemala in 2,031 m of water. At this site the hole penetrated to 418 m, and gas hydrates were encountered at 404 m.
Both sites are characterized by rates of sedimentation exceeding about 30 m/m.y. and organic carbon contents exceeding about 0.5%. The magnitudes and trends of gas compositions, residual gas concentrations and chlorinity variations are generally similar at both sites. The major organic geochemical differences at these sites appears to be in the carbon isotopic composition of methane [δ13 C(CH4)] and pore water ΣCO2[δ13C(ΣCO2)] at depth. The carbon isotopic compositions are significantly heavier at Site 568 than at Site 565. For example, δ13C(CH4) values at sites 565 and 568 are about −64 and −40 per mil, respectively; δ13C(ΣCO2) values are about +17 and +35 per mil. The isotopic compositions and trends at Site 565 are typical of biogenic methane generation. At Site 568, the isotopic compositions are very heavy, reflecting an unusual source of ΣCO2. In spite of its heavy carbon isotopic composition, this methane is believed to have a biogenic source.
Injection-Production Strategies for Reservoirs Having a Bottomwater Zone
Authors: Singh B. , Malcolm J. D. , Heidrick T. R. 
Published: December 2007

Abstract
The major oil sands deposits of Alberta are estimated to contain 197 billion cubic meters (1.23 × 1012 bbls) of heavy oil. In situ, thermal recovery techniques must be used to recover the vast majority of this resource. These techniques are complicated by the fact that about 25% of the deposits have a high water saturation zone underlying the formation. The extent of this bottom water zone varies from a few meters to tens of meters under a payzone averaging between 10–25 meters depending on the particular reservoir.
In designing a suitable thermal recovery method for these deposits, the presence of bottomwater is likely to have two important but competing effects. First, it may serve the purpose of providing initial injectivity in the highly viscous oil sand deposits. The second effect, however, is that this zone may act as a heat sink and significantly reduce the efficiency of heating oil sand above. The magnitude of these effects will depend on a variety of factors, notably oil viscosity, vertical permeability, injection rates, and oil saturation in the water sand, if any. Thus it is evident that for most reservoirs, the injection-production strategy must be "tailor-made" to optimize recovery.
This paper presents the results of numerical simulation studies undertaken to evaluate the effectiveness of steam and steam-additive processes to recover heavy oil from deposits with bottom water zone. It is concluded that additives such as carbon dioxide and permeability blocking agents do not improve recovery in many cases. However, it is shown that suitable injection-production strategies can be developed to improve oil recovery by using steam-additive processes.
Pressure Behavior of Layered Reservoirs with Crossflow
Authors: Bourdet D. 
Published: December 2007

Abstract
Experience with a large number of well tests has shown that the analysis of some field tests using currently available interpretation models is not satisfactory. Marked departure from homogeneous behavior is evident and none of the available heterogeneous models, such as the double porosity models, yields a convincing interpretation. This is particularly apparent when the pressure derivative behavior is examined.
In this paper, a new analytical solution is presented that describes the pressure response of a well intercepting a layered reservoir with crossflow. The model is designed to describe a system of alternating beds of relatively high permeability contrast. The interpreation models currently in use (homogeneous reservoir, two layers without crossflow, double porosity reservoir) are shown to be limiting forms of the new solution which is therefore a more general description of transient pressure responses.
The layered reservoir behavior is discussed in terms of the pressure and the derivative of pressure. The limits of applicability of the homogeneous and the double porosity solutions for analysis of tests in layered formations are clearly defined.
The new model is used to analyze an actual field case and a good match is obtained when no other solution is found to be applicable. In addition to the usual well and reservoir parameters (total permeability thickness product, skin and wellbore storage constant), analysis yields quantitative information on the storativity and permeability of the contrasting layers.
A Particle Sizing Technique Using Rayleigh Backscattered Ultrasonic Waves
Authors: Maharidge Russell L. 
Published: December 2007

Abstract
An ultrasonic technique, based upon Rayieigh scattering, is described for calculating the size distributions (2–10μm dia.) of low concentrations of particles in water from the amplitude measurements of backscattered acoustic pulses. Results of the particle size distribution calculations agree well with the size distributions measured with a Coulter counter. This technique was applied to particle systems that had identical material properties and size distribution functions which decreased with increasing size. With further development, this method may provide valuable solids content and size distribution information in source waters that are injected during waterflood operations.
Hydrogen Generation During In-Situ Combustion
Authors: Hajdo L. E. , Hallam R. J. , Vorndran L. D. L. 
Published: December 2007

ABSTRACT
BP Resources Canada Ltd. is operating an oxygen in-situ oil recovery pilot at Marguerite Lake, part of the Cold Lake heavy-oil deposit in eastern Alberta. The pilot consists of two principal areas: a three-well, wet air combustion test and an infill-drilled, four five-spot, wet oxygen combustion project on 2 hectare spacing (5 acres). All the wells were initially steam fractured and steam operated through several cycles. Thereafter, selected wells were converted to air or enriched-air i njectors.
Eight adiabatic combustion-tube tests were conducted at the University of Calgary on reservoir materials under various conditions. During several, but not all, of the tests small amounts of hydrogen gas were produced in a discontinuous fashion. In contrast to this, most wells in the field have produced hydrogen, some consistently as high as 20 mole percent.
The present study was undertaken in order to better understand the flow and reaction processes that generate hydrogen in situ and thereby to suggest ways of influencing its production. The results are interpreted in terms of five reaction processes involving hydrogen: aquathermolysis, thermolysis, coke gasification, the water-gas shift reaction and methanation.
It is concluded that the hydrogen is generated by the coke gasification reaction followed by the water-gas shift reaction. Methanation processes also play an important role. Thermal cracking is a minor contributor to the gas production and aquathermolysis is negligible.
Well Testing in Low-Transmissivity Oil Reservoirs
Authors: Kabir C. S. , Kucuk F. 
Published: December 2007

ABSTRACT
Well testing in a heavy-oil reservoir, characterised by low transmissivity, involves a long testing time because of long-duration wellbore storage effect. In some cases, several weeks may be required to reach the correct semilog straight line on the Horner graph.
This long-duration storage could be significantly reduced if a well is allowed to build up against the atmospheric pressure rather than the increasing shut-in wellhead pressure as commonly practised. Such a test could be easily conducted on a pumping oilwell. The procedure involves turning off the pump, opening the casing-head valve to atmosphere, and monitoring the rise of the annular liquid level with an acoustic well sounder (AWS). Measurement of the continuously moving annular liquid column provides both the bottom-hole pressure and the downhole rate during the buildup period. In other words, AWS data are translated to bottomhole pressures and downhole rate needed for transient analysis.
Field data indicates that a test conducted in this manner reduces the testing time to a fraction of the time required for a conventional test. A true static reservoir pressure (p¯) is attained in a very short time; consequently, uncertainty of correcting Horner's p* to p¯ is avoided. In essence, semilog straight line begins much earlier when the proposed testing technique is adopted.
This study attempts to reduce the wellbore storage distortion period in a pumping oil well test in two ways. First, we consider the convolution and deconvolution treatments of test data. Second, we propose a test technique that accelerates a pressure buildup process. The proposed technique is however limited to wells not capable of flowing to the surface upon shut-in. This imposed constraint is strictly based on practical considerations associated with such a test, and is not a limitation of the model considered in this work.
Use of Pressure Falloff Tests To Locate the Burning Front in the Miga Field, Eastern Venezuela
Authors: Da Prat G. , Bockh A. , Prado L. 
Published: December 2007

ABSTRACT
A study was made to determine the burned volume and the location of the firefront in the Miga P2,3 in-situ combustion project (Eastern Venezuela). This study was based on pressure fall-off data taken with a high resolution crystal pressure gauge with an automatic data acquisition and processing system. The importance of it lies in the fact that besides verifying, from a practical viewpoint, the predictions of the theoretical models available for composite systems, it shows some of the pitfalls associated with the use of quartz crystal pressure gauges.
A critical analysis of the observed pressure vs time data revealed some anomalies which may be associated with temperature effects in the pressure probe.
The actual pressure vs time data matches quite well the predictions made with a composite system model, and, therefore, the values obtained for the burned volume and the location of the burning front are believed to be reliable.
Khuff Development: Overview
Authors: Fathaila M. 
Published: December 2007

Abstract
The development of the Khuff Reservoir in Bahrain and the Gulf as a whole started way back in 1947, when crestal Well 52 in the Bahrain Field was deepened to discover the Khuff Reservoir at a depth of 10078'. In the hope of finding an oil column associated with the gas found in crestal Well 52, Wells 88 & 128 was drilled on the east and West flanks respectively with no show of oil in either of them.
At that time there was a limited source of rich gas in Bahrain from the relatively shallow zones of Arab A & C feeding the refinery and a power plant and consequently there was no requirement for an additional source of gas and as such the development of the Khuff Reservoir was stopped.
In the late sixties the Bahrain Government managed to interest investors to build an aluminium plant. The viability of the project was partly based on the availability of an abundant and reliable source of natural gas reasonably priced. Well 254 and 255 were drilled in 1969 specifically for this purpose. These two wells were followed by other wells, initially two at a time, to meet the continuous demand for the power sector and industrial use. We are at present at the final stages of a ten well program which will bring the total number of wells drilled and completed to 21 by Mid 86. The whole demand for gas on the island is ncw supplied from the Khuff and associated gas which is mostly cycled Khuff gas. The Arab gas reservoirs were shut-in in early '74 for conservation.