bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiphase Non-Darcy Flow in Proppant Packs
Authors: Barree R. D. , Conway M. W. 
Published: July 2009

Summary
This paper builds on a model for single-phase, non-Darcy flow in porous media presented in by Barree and Conway (2004). In this work, the generalized equation for single-phase non-Darcy flow is extended to multiphase-flow conditions. Laboratory measurements of gas/water flow were conducted in several flow cells to determine relative permeability curves and the nonlinear relationship between individual-phase flow rate and induced potential gradient over a wide range of input fractional-flow conditions and over a range of Reynolds numbers (Re). A model is presented to predict multiphase non-Darcy flow in porous media that is applicable to high-deliverability reservoirs and hydraulically fractured wells.
A Robust Steady-State Model for Flowing-Fluid Temperature in Complex Wells
Authors: Hasan A. R. , Kabir C. S. , Wang X. 
Published: July 2009

Summary
This paper presents an analytic model for computing the wellbore-fluid-temperature profile for steady fluid flow. Although wells with a constant-deviation angle can be handled with existing analytic models, complex well architectures demand rigorous treat-ment. For example, changing geothermal-temperature-gradient and deepwater wells present significant challenges. Additionally, available analytic models rarely provide calculation methods for various required thermal parameters, such as the Joule-Thompson (J-T) coefficient and fluid expansivity.
The approach taken in this study entails dividing the wellbore into many sections of uniform thermal properties and deviation angle. The governing differential equation is solved for each section, with fluid temperature from the prior section as the boundary condition. This piecewise approach makes the model versatile, allowing step-by-step calculation of fluid temperature for the entire wellbore. We present simple, thermodynamically sound approaches for estimating thermal parameters.
Success is indicated when performance of the proposed model is compared with data from three wells, producing two-phase gas/oil mixture, single-phase oil, and single-phase gas. Sensitivity of the estimated fluid temperatures to various thermal properties is also examined with our model. Overall, the effects of the J-T coefficient and liquid expansivity are found to be significant.
Development of World-Class Oil Production and Water Injection Rate and High Ultimate-Recovery Wells in Deepwater Turbidites—Bonga Example
Authors: Inikori Solomon O. , Coxe Bert , Ageh Ebenezer , Van Der Bok Jaap 
Published: July 2009

SummaryBonga field in deepwater Nigeria produces hydrocarbons from classic deepwater turbidite reservoirs deposited in channel settings. The reservoirs consist of a series of amalgamated channel complexes with varying degrees of compartmentalization. The depostional configuration presented significant uncertainties in connected volumes, well placements, and sweep efficiency between water injector/producer well pairs. However, because of the high costs of deepwater developments, well count needs to be as low as practical, and production rates must be sustainably high to ensure economic robustness of the project. High rates and high ultimate recoveries are the foundations of successful deepwater projects. At Bonga, constant pressure maintenance is a key component to achieving high-rate, high-ultimate-recovery wells. Several research studies concluded that the required water-injection wells be designed for fracture injection (i.e., above sandface-fracture pressure) to sustain the required high rates, as opposed to reservoir matrix injection. This paper presents the results of these research efforts leading to this conclusion and the implications on reservoir management. Also presented is an overview of the challenges of developing these complex channel deposits and the new approach to modeling high-rate wells in deepwater turbidites.Key to successful understanding of reservoir behavior (connectivity) and early indications of future reservoir performance is a systematic undertaking of interference tests at production startup.After approximately 2 years of production, the results from the Bonga wells demonstrate that sustained high oil rates could be achieved with adequate pressure maintenance. Average oil production rates of vertical/deviated wells range from 15,000 to 22,000 BOPD and that of horizontal wells range from 25,000 to 35,000 BOPD. Estimated ultimate recovery (EUR) per well ranges from 20 to 100 million STB for Phase 1 wells and from 10 to 30 million STB for Phase 2 development wells, with several additional opportunities for infill drilling of lower-EUR wells. Nameplate capacity of 225,000 BOPD was achieved and sustained with just nine producers and six injectors. To maintain these high production well rates, world-class water-injection well rates (of between 40,000 and 70,000 B/D per well) have been sustained since first oil.The fracture-injection approach is applicable both for onshore and offshore reservoir development but, more significantly, for deepwater reservoir development in which sustained high rates and economic considerations are paramount.
On the Influence of Viscosity on ESP Performance
Authors: Amaral Gilmar , Estevam Valdir , Franca Fernando A. 
Published: July 2009

Summary
This paper presents experimental data and a preliminary analysis of the influence of fluid viscosity on centrifugal-pump performance. Two centrifugal pumps, a conventional radial (specific speed Nq=8 rev/min) and a semi axial electrical submersible pump (ESP) (Nq=28 rev/min) were tested with 1-cp water and clear glycerin. Adjusting and controlling the fluid temperature in a closed test loop, it was possible to vary the glycerin viscosity from 67 to 1,020 cp within the range of light and heavy crude oils.
The main purpose of these tests, in addition to appraising the influence of viscosity on the pump's overall performance through the measurement of the derating factors for head, flow, and power, was to supply detailed information on the energy-transfer processes taking place in the pump's internal components. To accomplish this, the pressure distribution along the flow path from the pump inlet eye to the discharge section, including detailed pressure difference across impellers and diffusers, was measured. Thus, in addition to measuring the flow rate, the overall pressure difference, the speed, the power and the mean operation temperature for fluids with various viscosities within a full range of operational conditions, detailed data on the energy-transfer processes performed by impellers and diffusers were also taken.
Later analyses indicated that, in addition to the physical dimensions, operational conditions, and fluid properties, the pump performance is set by the strong flow interactions that exist between impellers and diffusers. In other words, these succeeding internal blade rows influence each other in terms of the head gain and the viscous dissipation effects. Thus, any generalizing approach dealing with the influence of viscosity on the pump performance must account for those interactions to give a proper measure of the derating factors over an extended range of operational conditions. Unfortunately, this is not true for the procedures available in the open literature. They lack representation and do not deliver proper correction factors for pumps that are not similar to those that generate the correlation database or for pumps working under operational conditions other than at the best-efficiency point (BEP). The data presented herein can be a launching point for a deeper analysis aimed to tackle these limitations.
Evidence of a Horizontal Hydraulic Fracture From Stress Rotations Across a Thrust Fault
Authors: Maxwell S. C. , Zimmer U. , Gusek R. , Quirk D. 
Published: July 2009

Summary
Microseismic imaging of a hydraulic-fracture stimulation showed significant fracture reorientation across a thrust fault. Fracture orientations were identified through a combination of alignment of event locations, polarization of the seismic waves, and injection details. Stimulation below the fault indicated a near-horizontal fracture geometry. Above the fault, a near-vertical fracture geometry was observed. A change in fault orientation was supported by differences in the microseismic-signal characteristics and the treatment-injection data. This difference in fracture geometry was attributed to rotations in the direction of minimum principal stress, which is consistent with observed differences in the injection pressures.
Optimizing Downhole Fluid Production of Sucker-Rod Pumps With Variable Motor Speed
Authors: Palka Krzysztof , Czyz Jaroslaw A. 
Published: July 2009

Summary
Reciprocating oil pumps are operated traditionally by prime movers rotating at a constant speed. This paper demonstrates that by changing motor speed rapidly within a single stroke, pump production can be increased while stresses in the sucker rod and motor energy consumption are reduced. The optimal motor-speed profile is determined by representing the motor speed with Fourier series and searching for Fourier coefficients that maximize the production while satisfying the imposed constraints on stresses in the rod and on energy consumption. The pump-performance parameters required in the optimization process, such as fluid production, stresses in the rod, and motor torque resulting from a given variable motor speed, are calculated by predictive analysis. The analysis is based on a comprehensive dynamic model of the entire pumping system, comprising surface and downhole equipment.
During, and beyond, a minimum 6-month field-validation period, the calculated optimal speed profile has been applied to control the movement of more than 20 pumps currently operating in Alberta, Canada. The resulting increased production and lower operating cost confirmed clearly the benefits of implementing a variable speed of the prime mover to improve pump performance. Presented examples demonstrate an increase of up to 133% in production without increasing energy consumption or loads in the system. Results similar to those with beam pumps can be achieved for hydraulically actuated pumps by applying variable flow rate or pressure to induce the calculated optimal polished rod velocity.
Unbiased Estimation of Intrinsic Permeability With Cumulants Beyond the Lognormal Assumption
Authors: Vargas-Guzmán J. A. 
Published: July 2009

Summary
The usual practice is to transform intrinsic-permeability data with logarithms to get a linear relation with porosity. Such transformations are known to produce undesired effects in 3D geocellular-models (i.e., smoothing data, elimination of extreme values, and biased estimates). Ideally, logarithms of data may lead to Gaussian distributions, which are easily handled by classical spatial statistics and linear collocated-cokriging. The exponential model from back-transformed linear regression "underestimates" permeability. If the lognormal assumption is not met, a second order correction may "overestimate" permeability. Transformations of permeability data may uncover the fact that a truly non-Gaussian statistical distribution cannot be avoided, and this brings complications to the modeling of permeability. Shortcomings of transforms for non-Gaussian cases may affect the quality of reservoir models for history match forcing to the use of arbitrary multipliers. Systematically biased flow predictions might be avoided by proper modeling of flow parameters including intrinsic permeability. Truly non-Gaussian modeling of permeability is developed in this paper to find a solution to these problems. The analysis starts by linking the exponential model to power transformations from Taylor series. Residual-terms (RTs) are introduced for correct back-transformation of estimates. An advanced result, for the truly non-Gaussian case, is that the RTs take the form of numerical higher order cumulants and not moments. RTs represent the contribution of spatial heterogeneous components that occur when spatial permeability varies beyond a pair-wise covariance or variogram. Results in this paper show that "higher-order cumulants" improve permeability estimates significantly in rocks with large dispersion of values dominated by higher permeabilities (e.g., shaley sands and laminated grainstone carbonates). This study has proposed new ways for spatial modeling of permeability, avoiding under or overestimations, and the proposed approach provides the basis for the use of cumulants for spatial higher-order estimation.
Verification of Asphaltene-Instability-Trend (ASIST) Predictions for Low-Molecular-Weight Alkanes
Authors: Creek Jefferson L. , Wang Jianxin , Buckley Jill S. 
Published: July 2009

Summary
Anticipating when and where asphaltenes may flocculate during oil production is a key step in successfully preventing or mitigating asphaltene problems in the field. Because there will be no deposition without precipitation, mapping of asphaltene stability over a wide range of temperature, pressure, and composition is required. The ASIST allows the determination of the onset of asphaltene instability to be established with a series of liquid n-alkanes. These data are used to predict asphaltene stability of live fluids by extrapolating the onset condition from the base data to reservoir conditions by use of a linear extrapolation of the onset solubility parameter vs. square root of the partial molar volume of the precipitant. This extrapolation has been demonstrated previously to be accurate for methane and a model oil. The present work verifies that such an extrapolation is valid for predicting the asphaltene instability for mixtures of methane, ethane, and propane with a representative stock-tank oil (STO). The STO was combined with known amounts of methane, ethane, or propane. The asphaltene onset pressure was determined by a combination of near-infrared (NIR) light scattering and microscopic observation. The onset conditions at ambient pressures were examined for flocculation periods ranging from 20 minutes to 24 hours. Onset pressures calculated with the 5-hour ASIST trends compared well with measured onset pressures.
Prediction of Gas Productivity From Eastern Nankai Trough Methane-Hydrate Reservoirs
Authors: Kurihara Masanori , Sato Akihiko , Ouchi Hisanao , Narita Hideo , Masuda Yoshihiro , Saeki Tatsuo , Fujii Tetsuya 
Published: July 2009

Summary
The Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) has been evaluating methane-hydrate (MH) reservoirs located in the eastern Nankai trough from the viewpoints of geology, geophysics, petrophysics, and reservoir/ production engineering. As one of these studies, we have been predicting gas/water production performances from these MH reservoirs showing diverse characteristics. This paper presents the results of our examinations on the applicability of a variety of MH dissociation/production methods to these MH reservoirs and on the feasibility of future development in terms of gas production and economics.
Eastern Nankai trough MH reservoirs, which are composed of alternating beds of sand, silt, and clay in turbidite sediments, have various conditions of clay distribution and of initial pressure, temperature, permeability, and MH saturation. Some of these reservoirs contain MH of high saturation at a certain interval (MH concentrated reservoir), while in the others, MH is deposited sparsely (MH-nonconcentrated reservoir). Detailed numerical reservoir models were constructed for both MH-concentrated and -nonconcentrated reservoirs, consulting the well-log and seismic-interpretation results.
MH-dissociation/-production performances were then predicted through numerical simulation, assuming the application of various MH-dissociation methods (such as depressurization, well-bore heating, hot-water huff'n'puff, and hot waterflooding. The simulation studies clarified the difference in the gas production between MH-concentrated and -nonconcentrated reservoirs. These studies also revealed that the permeability not only of sand layers but also of clay layers has a significant effect on the gas productivity from MH-concentrated reservoirs. Furthermore, it was suggested that the hot-water injection was effective when it was applied as a secondary-recovery method after depressurization. Simple economic analyses on the basis of these simulation results exhibited the promise that some MH reservoirs in the Eastern Nankai trough could be developed economically if the well spacing and MH-dissociation/-production methods were designed appropriately.
Displacement Mechanisms of Micellar Solutions
Authors: Davis J.A. , Jones S.C. 
Published: July 2009

Abstract
This paper describes displacement mechanisms of micellar solution slugs, displaced by a thickened water "mobility buffer", in a glass micromodeland in consolidated Berea sandstone cores. Colored motion pictures, takenthrough a microscope, recorded interactions on a pore-to-pore basis in themicromodel. Production and differential pressure data from consolidated corespreviously waterflooded to residual oil saturation revealed displacementmechanisms macroscopically.
Oil is displaced miscibly, while interstitial water is displaced immisciblyby the injected micellar solution slug. Part of this water is dispersed andcarried near the leading edge of the slug, and some may remain as a residualsaturation. Thickened water displaces any residual water. It also emulsifieswith the slug material, thereby displacing it. The displacement sequence formsbanks of oil and water with relatively constant fractional flows, saturations, and mobilities. The mobility of oil and water flowing ahead of the slug definesslug viscosity required for stable displacement.
Equations are presented that describe several aspects of the displacementflow behavior: oil breakthrough, oil cut during production of the stabilizedbank, breakthrough of banked water and the resulting decreased fractional flowof oil, fluid mobilities, etc. Breakthroughs, calculated from the equations, are compared with experimental data.
Slugs of micellar solution, ranging from 1 to 5 percent PV, producedunusually high oil recoveries (up to 100 percent) in previously waterfloodedconsolidated cores. Investigation of the effect of mobility buffer size on oilrecovery indicated that recovery is reduced in 3-in. X 4-ft cores for mobilitybuffer sizes smaller than 50 percent of the pore volume.
Valuation of Natural Gas Property
Authors: Davis Ralph E. , Stephenson Eugene A. 
Published: July 2009

The appraisal of natural gas properties is a complex problem affected bymany non-engineering factors. Attention will be brought here to the moreimportant matters that influence value of such properties, such as thenecessity of competent estimates of reserves, availability of the products andof market outlets, the expected rate of recovery, the anticipated prices ofproducts and future costs, the effect of the graduated income tax on profitswhich lead to greater value of a property to one owner than to another, andother items. To a degree, in each appraisal the problems are unique in that theapproach must be suited to the particular case.
During the past 30 years and more, many engineers and geologists haveaccumulated considerable experience in the problems of evaluating propertiescapable of producing oil and natural gas. An extensive literature has developedoutlining the principles and methods that govern appraisals. Emphasis is placedherein on the importance of careful analysis of the various factors whichshould lead to a determination of value, and to point out the inadequacy ofrather common engineering appraisals that frequently have little relation towhat has been termed "fair market value." In a Delaware court someyears ago an engineer admitted freely on cross-examination that his appraisalwas "an engineering valuation - not a determination of the fair marketvalue. Such so-called "engineering appraisals" are perhaps interesting, and occasionally may be of some use, but must not be considered of fairvalue.
During the past few years the effect of the graduated income tax has becomeespecially important in the appraisal of properties yielding income, andpromises to continue to be so far a long time. This tax places somecorporations in the 52 per cent bracket and subjects individuals to rates thatmay be as high as 85 to 90 per cent. To those institutions whose income is nottaxed, a property can be worth two or three times as much as it may be to theindividual in a high tax bracket.
Differences in Baseline Lymphocyte Counts and Autoreactivity Are Associated With Differences in Outcome of Islet Cell Transplantation in Type 1 Diabetic Patients
Authors: Hilbrands Robert , Huurman Volkert A.L. , Gillard Pieter , Velthuis Jurjen H.L. , De Waele Marc , Mathieu Chantal , Kaufman Leonard , Pipeleers-Marichal Miriam , Ling Zhidong , Movahedi Babak , Jacobs-Tulleneers-Thevissen Daniel , Monbaliu Diethard , Ysebaert Dirk , Gorus Frans K. , Roep Bart O. , Pipeleers Daniel G. , Keymeulen Bart 
Published: July 2009

OBJECTIVE
The metabolic outcome of islet cell transplants in type 1 diabetic patients is variable. This retrospective analysis examines whether differences in recipient characteristics at the time of transplantation are correlated with inadequate graft function.

RESEARCH DESIGN AND METHODS
Thirty nonuremic C-peptide–negative type 1 diabetic patients had received an intraportal islet cell graft of comparable size under an ATG-tacrolimus–mycophenolate mofetil regimen. Baseline patient characteristics were compared with outcome parameters during the first 6 posttransplant months (i.e., plasma C-peptide, glycemic variability, and gain of insulin independence). Correlations in univariate analysis were further examined in a multivariate model.

RESULTS
Patients that did not become insulin independent exhibited significantly higher counts of B-cells as well as a T-cell autoreactivity against insulinoma-associated protein 2 (IA2) and/or GAD. In one of them, a liver biopsy during posttransplant year 2 showed B-cell accumulations near insulin-positive β-cell aggregates. Higher baseline total lymphocytes and T-cell autoreactivity were also correlated with lower plasma C-peptide levels and higher glycemic variability.

CONCLUSIONS
Higher total and B-cell counts and presence of T-cell autoreactivity at baseline are independently associated with lower graft function in type 1 diabetic patients receiving intraportal islet cells under ATG-tacrolimus–mycophenolate mofetil therapy. Prospective studies are needed to assess whether control of these characteristics can help increase the function of islet cell grafts during the first year posttransplantation.