bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pressure Transient Behavior In Reservoirs With An Internal Circular Discontinuity
Authors: Rosa Adalberto J. , Horne Roland N. 
Published: December 2007

Abstract
This paper presents the pressure transient response for reservoirs with an internal circular subregion. The solution is a generalization of that previously presented in the literature, which assumed that the subregion was either an impermeable barrier or a constant pressure circle. Two cases were considered, with the well located either inside or outside the circular discontinuity. When the well is located inside the circular subregion, the solution developed in the study is also a generalization of the well-known pressure response for a composite two-region system.
The solution was obtained by using the concept of Green's function and by applying the Laplace transformation technique. The Laplace space response, although very complex, was inverted to real space with the Stehfest1 algorithm.
When the well is located inside the circular subregion, the wellbore pressure response shows a behavior typical of radial composite systems, except for the effect of the well eccentricity, which acts as a skin factor. For the case where the active well is external to the subregion, three flow regimes are observed. The initial infinite-acting behavior and the late-time pseudoradial flow produce semilog straight lines which are parallel and reflect the transmissivity of the external region. The long-time effect of the discontinuity can be regarded as an apparent skin effect.
The dependence of the solution on the diffusivity ratio, the mobility ratio, the geometric configuration and the size of the system was also investigated in the study.
The solution can be used to simulate the pressure behavior for reservoirs which contain circular or approximately circular discontinuities, such as those caused by variations in rock and/or fluid properties due to the presence of shale lenses or fluid injection, for instance. The pressure solution can also be used to interpret single-well or interference tests in systems with these configurations.
Pressure Behavior in Finite Channel-Levee Complexes
Authors: Bourgeois M. J. , Daviau F. H. , de la Combe Jean-Luc Boutaud 
Published: December 2007

Summary
In a channelized environment, the overbank facies (levees, crevasse-splays) have poorer reservoir qualities than the channel itself. In this type of environment, the geometry of this two-feature complex, together with its permeability contrast, influences the pressure transient response. The pressure behavior of this kind of reservoir has been computed for well-test analysis purposes.
Our geometric model comprises a main channel bounded laterally with finite or infinite width levees. It is conceptualized as a composite linear strip reservoir with different mobilities and diffusivities. The length of the whole system also can be either finite or infinite. The solution uses a time-space Laplace transform and a spatial Fourier transform already used by Ambastha,1 Butler,2 and Kuchuk.3 Moreover, our model adds lateral limits by no-flux boundary conditions and longitudinal limits by superposition of image wells or by using a finite Fourier transform.
This paper exhibits specific features of the type curves generated for the model. The influence of the levees and of the permeability ratio between channel and levees on the derivative signature is discussed. Hints are given for diagnostic purposes and parameter estimation. Fieldcase buildup analyses show the applicability of the approach.
Distinct Element Simulation of Faulted Reservoir Behavior
Authors: Makurat A. H. , Gutierrez Marte , Knapstad Børge , Johnsen J. H. , Koestler A. G. 
Published: December 2007

Summary
With a distinct element code, we analyzed a compartmentalized North Sea oil reservoir's mechanical behavior during fluid pressure drawdown. Special emphasis was given to the affect of compartment pressure reduction on the activation of existing faults, the change of the fault-sealing properties as a result of fracturing of the intact rock mass, and the determination of the existing faults' behavior during fluid pressure drawdown with respect to shear displacement and changes in the fault/fracture conductivities. The simulations showed that several segments of the existing faults in the vicinity of the drawdown region could be activated. Some faults with shear stresses below peak showed large shear displacements and were therefore considered to be activated. Shear fracturing of the intact rock was found to be possible in several zones around the drawdown region.
An Improved Method for Acidizing Oil Wells in Sandstone Formations
Authors: Gidley J. L. , Brezovec E. J. , King G. E. 
Published: December 2007

SummaryA previous analysis of field experience1 indicates that in the acidization of oil wells, unlike that of gas wells, response peaks at relatively low acid volumes per foot of formation treated, and declines beyond the optimum treating volume. One method of removing this treatment-volume barrier is to displace oil from the zone to be acidized and to replace it with gas. In this manner, the interaction between the spent acid products and formation fluids is similar to that found in a gas zone. This paper describes the results of acidizing oil wells where the resident oil in the near-wellbore region has been replaced with a gas. Early results with this treatment indicate an improved acid response, less stimulation of water, and reduced emulsion separation problems at the surface.
The Effects of Unbroken Fracture Fluid on Gaswell Performance
Authors: Voneiff G. W. , Robinson B. M. , Holditch S. A. 
Published: December 2007

Summary
Research sponsored by the Gas Research Inst. (GRI) indicates unbroken fracture fluids can lower gas reserves by 30%, reduce initial gas rates by 80%, and delay fracture-fluid cleanup by weeks or months. The unbroken fracture fluids flatten the production profile. In extreme cases, gas production slowly increases for weeks or months despite constant flowing pressures. The fracture fluids must break to a viscosity of 50 cp or less to ensure that gas reserves are maximized.
The Application of Advanced PDC Concepts Proves Effective in South Texas
Authors: Dahlem J. S. , Baxter R. L. , Dunn K. E. , Arfele R. W. , Hicks M. G. 
Published: December 2007

SummaryOver the years, a variety of problems with polycrystalline diamond compact (PDC) bit design and application has been documented, with "bit whirl" being identified as the cause of many inherent problems. The goal of most PDC manufacturers, and the subject of this paper, is development of a better-performing, "whirl-resistant" PDC bit design. Similarly, the goal for most operators is the lower cost resulting from effective application of such bits.Toward those ends, a cooperative development effort between operators and a manufacturer was undertaken to apply advanced concepts effectively to the design, manufacture, and application of a new series of PDC bits in south Texas. Adoption of design concepts, such as force-balanced cutting structures, asymmetric blade layouts, spiral blade designs, and tracking cutter arrangements, proved effective in countering the destructive effects of bit whirl, and allowed PDC bits to be used in harder formations. Summaries of both operational and economic performance confirm the success of the undertaking.
Narrow Annulus Cementing in the Deep Anadarko Basin
Authors: Waters G. A. , Wray B. L. 
Published: December 2007

Abstract
With the widespread use of tubingless completions and narrow annulus liners now employed in the Anadarko Basin the applicability of conventional cementing placement techniques and cement systems has been brought into question. The narrower annuli necessitate the use of a more dispersed cement to impart acceptable friction pressure. Excessive friction pressure may lead to formation breakdown, lost circulation and potential well control problems. If lower friction pressures can be achieved higher pump rates should be attainable which may improve fluid placement efficiency.
The dispersed slurry must still maintain acceptable fluid loss control and solids suspension properties. These parameters are critical in narrow annulus cementing since high fluid loss and/or sedimentation is much more likely to cause annular bridging than in a conventional annulus.
As in most cases, it is desirable to use a slurry with a rapid and predictable transition from a fluid to set state. This will reduce the likelihood of reservoir fluids flowing into the wellbore and compromising the integrity of the cement as compressive strength develops.
It must be recognized that mud removal is critical in a narrow an-nulus because a small volume of contaminated fluid can occupy a large interval in the annulus. Fortunately, because of the narrow an-nulus, it may be possible to utilize turbulent flow profiles to remove drilling mud during the cementing process.
To address these issues a study was initiated to develop a methodology for cementing in this environment. The first step was to determine spacer and cement properties required to optimize mud removal and cement placement via computer modeling. Laboratory testing was then performed to develop spacer and cement systems to meet the required parameters. Third, the new fluids and placement techniques were employed in the field using placement pressures as an initial indicator of success or failure. Finally, a measure of zonal isolation was estimated through wireline bond logs to quantify the degree of success.
Asymmetrically Propped Hydraulic Fractures
Authors: Jeffrey R. G. 
Published: December 2007

SummaryMapping during and after mining of four hydraulic fractures placed in the German Creek coal seam of the Bowen Basin in Queensland, Australia, revealed that in all four cases the fractures were propped asymmetrically. Three treatments resulted in vertical fractures and one resulted in a T-shaped but mostly horizontal fracture. In all cases, the proppant extended to a greater distance in the down-dip than in the up-dip direction. The transport of proppant in the down-dip direction by gravity currents is consistent with the field and laboratory data and is able to explain the asymmetry.
Performance Evaluation of Trilateral Wells: Field Examples
Authors: Vo D. T. , Madden M. V. 
Published: December 2007

SummaryRecent advances in horizontal drilling and completion technology have led to the successful completion of multilateral horizontal wells (wells with two or more laterals penetrating separate zones that produce through a single wellbore to the surface). Evaluating performance of these commingled horizontal wells poses unique problems that have led to development of a practical procedure for that puφose. This paper demonstrates a practical procedure used in evaluating the performance of three lateral (trilateral) horizontal wells. The procedure, coupling the analysis of pressure-buildup and rate/time data, involves use of a consistent mathematical model to generate pressure and rate responses for pressure-test interpretation and performance prediction. The procedure is demonstrated for several new trilateral wells drilled in the Dos Cuadras field, offshore California. Results from field tests indicate that the procedure is efficient in evaluating the performance of these wells. Reservoir and well parameters are obtained and the contribution of all laterals is confirmed from pressure-test interpretation. The computed model parameters are then used in a rate history match and accurate long-term performance predictions are made. Deconvolution is shown to improve the history-match process. In addition, the performance evaluation of these trilateral wells is compared with previously drilled single-lateral horizontal wells in the same field. The comparison confirms that the new trilateral horizontal well technology is economically viable, allowing reserves to be developed for approximately two-thirds the cost of three single-lateral horizontal wells.
Nash Reservoir Management Study With Stochastic Images—A Case Study
Authors: Fanchi J. R. , Meng Hai-Zui , Stoltz R. P. , Owen M. W. 
Published: December 2007

Summary
An application of geostatistical modeling in the context of a full-field reservoir model study of the Northeast Nash waterflood is described. Geostatistics provides value in preparing and quickly modifying a self-consistent model of reservoir geology. It does not, however, provide a complete description of all the geologic features that impact fluid flow. A rationale for selecting a stochastic description instead of a deterministic description is presented.
Improved Borehole Imaging by Ultrasonics
Authors: Hayman A. J. , Parent Philippe , Cheung Philip , Verges Patrick 
Published: December 2007

Summary
A new ultrasonic tool for borehole and casing imaging has been developed based on recent cementation-imaging technology. A rotating ultrasonic transducer scans the borehole at a high sampling rate to provide detailed images of echo amplitude and radius.
A 250- or 500-kHz focused transducer gives high resolution, penetration in heavy mud, and low sensitivity to tool eccentering. The echoes are analyzed by a downhole digital signal processor to optimize the accuracy and reliability of the radius measurement. The measurements are corrected for eccentering, and the image color scales are dynamically adjusted for optimum sensitivity in real time by the surface computer.
Comparisons with electrical imaging tools show that the ultrasonic amplitude measurement tends to respond to lithology indirectly by changes in borehole radius or rugosity. Ultrasonic imaging is unique in making quantitative high-resolution measurements of borehole geometry that are useful for borehole-stability analysis. Examples of automatic hole-shape analysis are shown. The tool can also evaluate internal casing corrosion and detect holes.
Rheology of Crosslinked Foams
Authors: Harris P. C. , Heath S. J. 
Published: December 2007

Summary
The rheology of foam fracturing fluids has been previously described as a yield-pseudoplastic fluid for a broad range of qualities, linear gel concentrations, and temperatures. With the increased use of foams for fracturing with higher proppant concentrations, crosslinking agents are often added. Because the viscous character of the external phase of the foam strongly influences the viscous properties of the foam, the viscosity of the foam will increase if the external phase is crosslinked.
Rheological properties of 25%- to 75%-quality N2 foams containing borate-crosslinked guar were measured on the recirculating flow-loop viscometer at temperatures from 75 to 300°F. When polymer was crosslinked in the foam, viscosity increased by factors of 3 to 10 or more over foams that contained only linear gel.
The fluid viscosity developed in a foam is a product of gas quality, external phase fluid viscosity, and crosslinking of the polymer in the external phase. The extent to which each of these factors is important depends upon both the quality and the concentration of the crosslinked polymer. Viscosity resulting from borate crosslinking is a stronger factor than either quality or linear polymer concentration. Borate crosslinking influence is greatest at low quality and at high polymer concentration.
Dynamic Fluid Loss in Hydraulic Fracturing Under Realistic Shear Conditions in High-Permeability Rocks
Authors: Navarrete R. C. , Cawiezel K. E. , Constien V. G. 
Published: December 2007

SummaryA study of the dynamic fluid loss of hydraulic fracturing fluids under realistic shear conditions is presented. During a hydraulic fracturing treatment, a polymeric solution is pumped under pressure down the well to create and propagate a fracture. Part of the fluid leaks into the rock formation, leaving a skin layer of polymer, or polymer filter cake, at the rock surface or in the pore space. The fluid-loss behavior depends on the extent to which the polymer invades the porous rock and the thickness of the polymer filter cake, which is limited by the shear stress that the flowing fracturing fluid exerts on it. The effect of shear rate on the dynamic fluid-loss behavior of linear gels and crosslinked borate guars was studied using cores of permeabilities ranging from 0.5 to 70 md, pressure drops of 1,000 psi, and temperatures between 75 and 150°F. The effect of shear on the formation of external filter cake and on the effectiveness of particulate fluid-loss additives was also studied. A shear rate history representative of that experienced by a rock segment in the fracture was used. In this history, the shear rate drops from a very high rate of 380 sec−1 down to 40 sec−1 because of the widening of the fracture width as time advances.Constant shear rate results show that high shear rates eliminate external filter cakes. In the absence of external cakes, the formation of internal filter cakes controls fluid loss, especially in high-permeability cores. The effectiveness of particulate fluid-loss additives increases with the permeability of the rock and decreases with shear rate and viscosity of the fluid. Shear history results show that the highest leakoff rates and volumes occur during the first 10 minutes of leakoff, i.e., when the rock surface is exposed to high shear rates. Once the shear rate drops below a critical shear value, polymer filter-cake deposition begins and the rate of leakoff slows down. The effect on fluid loss is that a majority of the fluid is lost at high shear rates during a fracturing treatment (i.e., when no polymer filter cake is formed), especially at the beginning of the treatment. To have a major effect on reducing fluid loss, the emphasis has to be placed on plugging the pore throats at the surface of the rock.
Water-Salinity Variations in the Ivishak and Sag River Reservoirs at Prudhoe Bay
Authors: McCoy D. D. , Warner H. R. , Fisher T. E. 
Published: December 2007

Summary
More than 2,000 chloride-concentration measurements made on extracted water from oil-base-mud cores show areal and vertical varia-tions in the salinity of Ivishak and Sag River reservoir brines. These data compare favorably with compositional analyses of produced and extracted water, spontaneous-potential (SP) analyses, and resistivity-log calculations. In calculating water saturations with the Archie equation, it was critical that variations in resident water resistivity be recognized. This paper describes the variations observed and the work done to validate the extent and magnitude of the salinity variations.
Validation of As-Received Oil-Based-Core Water Saturations From Prudhoe Bay
Authors: Richardson J. G. , Holstein E. D. , Rathmell J. J. , Warner H. R. 
Published: December 2007

Summary
Determining connate-water saturations is a key factor in calculating original hydrocarbon pore volume (HCPV) for the Ivishak reservoir, the largest productive horizon in the Prudhoe Bay field. As-received water saturation, Sw, measurements on oil-based-mud cores (OBC's) from 27 wells were used as the core standard for Sw determination. Measured values ranged from &lt; 1 to &gt;56% PV, which raised questions as to the validity of these values as being representative of in-situ conditions. Studies of the effects of the cutting, surfacing, and handling of these cores were conducted. Some cores were recovered with centers uninvaded by mud filtrate. Sw values in these sections were the same as those in mud-filtrate-invaded sections of other portions of the same core. Pressure and conventional cores had similar Sw values in adjacent intervals and to nearby oil-based-mud-cored wells. Rigsite Sw were measured and found to be the same as those determined routinely by Core Laboratories in Anchorage. These data offered convincing proof that, above the oil/water transition zone, water was not flushed from the core during the coring process, expelled or evaporated during surfacing, or evaporated while in transit to Anchorage for routine measurements.
A large, alternative, centrifuge capillary pressure database was developed to provide an independent check of the OBC results. De-velopment of this database required selection of samples statistically representative of rock types in the reservoir and use of laboratory techniques that produced reliable results. Comparing Swpc with Swobc values required the consideration of the burial and hydrocarbon accumulation histories and the variations in hydrocarbon properties within the reservoir.
Measurement and Prediction of Hydrate-Phase Equilibria for Reservoir Fluids
Authors: Tohidi Bahman , Danesh Ali , Todd A. C. , Burgass R. W. 
Published: December 2007

Summary
Problems associated with gas hydrates in the production and transportation of unprocessed wellstreams can be avoided by either preventing hydrate formation or allowing the formation of hydrates, but preventing their aggregation, and transporting them as slurry.
The first approach, which is the current practice in the industry, can be made more cost effective by determining the hydrate-phase boundary more reliably. For the second approach, it is necessary to determine the amount of hydrates to be transported as slurry.
This paper reviews the effect of electrolyte solutions and heavy hydrate formers (such as benzene, cyclohexane, and methylcyclopentane) on the hydrate-free zone and discusses new methods and equipment for measuring the amount and composition of different phases in hydrate-forming conditions. An in-house numerical model has been successfully employed for prediction of the hydrate-free zone and the compositional data.
Deasphalted Oil: A Natural Asphaltene Solvent
Authors: Jamaluddin A. K. M. , Nazarko T. W. , Sills Suzanne , Fuhr B. J. 
Published: December 2007

Summary
Asphaltene deposition in the near-wellbore region can block pore throats, change wettability characteristics and relative-permeability relationships, and therefore, reduce oil production. Conventional aromatic solvents (e.g., toluene and xylene) alone or in combination with various dispersants are used to remove asphaltene damage from the near-wellbore region. However, these aromatic solvents are expensive and are not environmentally friendly. The objective of this work was to systematically evaluate the asphaltene-solvating power of various nonconventional solvents, including deasphalted oil, using a light-scattering technique.
Experimental results suggest that deasphalted oil is a strong asphaltene solvent presumably because of its native resin and aromatic contents. Addition of asphaltene dispersants also increases the solubilizing power of the deasphalted oil. Furthermore, various refinery and heavy oil upgrader streams show strong ability to solubilize asphaltenes.
Residual Oil Reservoir Recovery With Seismic Vibrations
Authors: Nikolaevskiy V. N. , Lopukhov G. P. , Liao Yizhu , Economides M. J. 
Published: December 2007

Summary
Evidence suggests that certain vibrations, generated either by natural seismic events or by artificial explosions, have altered the production behavior of oil wells at distances as much as 200 km from the epicenter. These changes have affected the produced water/oil ratio: the water production rate increased from a formation that was at approximately the interstitial water saturation, while the oil rate increased in watered-out reservoirs that were near the residual oil saturation.
Theoretical and field investigations of the phenomena suggest that vibrations may influence substantially the water or oil relative permeability that appears to be partially reconstituted at saturations that ordinarily would prohibit the flow of a particular phase. The key role is played by ultrasound oscillations, generated by seismic waves within the stratum, and it has been confirmed by in-situ measurements during the vibrostimulation of reservoirs.
This paper provides an interpretation of the process and describes wave requirements, wave generation, and propagation in oil-bearing porous media supported by laboratory experiments and field cases of vibrostimulation of oil production from water-flooded reservoirs.