bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reference range of serum calcitonin levels in humans: influence of calcitonin assays, sex, age, and cigarette smoking
Authors: d'Herbomez Michèle , Caron Philippe , Bauters Catherine , Do Cao Christine , Schlienger Jean-Louis , Sapin Rémy , Baldet Line , Carnaille Bruno , Wémeau Jean-Louis , _ _ 
Published: December 2007

ObjectiveThe objective of this study was to re-evaluate the adult CT reference values determined by five different immunoassays and by introducing criteria for selecting control subjects.DesignA prospective multicenter study.PatientsThree hundred and seventy-five clinically euthyroid subjects.MethodsWe used five different CT immunoassays. Sera were assayed for the concentration of TSH, gastrin, procalcitonin, urea, calcium, and anti-thyroperoxidase antibodies.ResultsScreening for the various potential causes of hypercalcitoninemia led to the exclusion of 23% of the sera. Our reference value analysis dealt with 287 subjects (142 men and 145 women). The proportion of samples in which no CT was detected varied from 56% (for assay D) to 88% (for assay C). We observed significant correlations (whose magnitude depended on the assay used) between CT levels and age or body mass index (BMI) (primarily in men). The distribution of CT levels showed that 4.7, 9.8, 2.5, 6.5, and 8.0% of the values were over 10 pg/ml respectively. These values corresponded essentially to samples from 11 male subjects (median age: 55 years), most of whom were smokers. The highest CT values were around twice as high in men than women, and were higher in smokers than non-smokers.ConclusionIn clinical practice (and after having excluded the usual causes of raised CT levels), the interpretation of CT assay results must take into account i) the method used; ii) the patient's gender, age, and weight; and iii) the potential influence of cigarette smoking.
Using Neural Networks for Candidate Selection and Well Performance Prediction in Water-Shutoff Treatments Using Polymer Gels—A Field-Case Study
Authors: Saeedi A. , Camarda K. V. , Liang J. T. 
Published: December 2007

SummaryUsing actual field cases, a neural network model was developed to identify candidate wells and predict well performance for water shutoff treatments using polymer gels. A feed forward back propagation algorithm was used to develop the neural networks. The before and after treatment data for 22 wells treated with polymer gels in the Arbuckle formation in central Kansas were used to train and verify the neural networks.Polymers and gels have been used extensively in field applications to suppress excess water production and improve oil productivity. Field experience has demonstrated that candidate-well selection is critical to the success of gel-polymer treatments. To date, most candidate-well selections are on the basis of anecdotal screening guidelines, which often results in inconsistent treatment outcomes. With only pretreatment well data as input parameters, the neural networks developed in this work can accurately predict the post-treatment cumulative oil production of the well one month after treatment with an average error of 16%, and the post-treatment cumulative oil production three months after treatment with an average error of 10%. This is a dramatic improvement over the current method of using anecdotal screening guidelines for candidate-well selections.This method represents a major breakthrough where the candidate selection can now be on the basis of the accurate predictions of treatment outcomes without having to use complicated reservoir models to simulate the well performance after treatment.
Capillary Equilibrium in Porous Materials
Authors: Morrow Norman R. , Harris Colin C. 
Published: December 2007

Abstract
The experimental points which describe capillary pressure curves are determined at apparent equilibria which are observed after hydrodynamic flow has ceased. For most systems, the time required to obtain equalization of pressure throughout the discontinuous part of a phase is prohibitive. To permit experimental points to be described as equilibria, a model of capillary behavior is proposed where mass transfer is restricted to bulk fluid flow. Model capillary pressure curves follow if the path described by such points is independent of the rate at which the saturation was changed to attain a capillary pressure point. A modified suction potential technique is used to study cyclic relationships between capillary pressure and moisture content for a porous mass. The time taken to complete an experiment was greatly reduced by using small samples.

Introduction
Capillary retention of liquid by porous materials has been investigated in the fields of hydrology, soil science, oil reservoir engineering, chemical engineering, soil mechanics, textiles, paper making and building materials. In studies of the immiscible displacement of one fluid by another within a porous bed, drainage columns and suction potential techniques have been used to obtain relationships between pressure deficiency and saturation (Fig. 1). Except where there is no hysteresis of contact angle and the solid is of simple geometry, such as a tube of uniform cross section, there is hysteresis in the relationship between capillary pressure and saturation. The relationship which has received most attention is displacement of fluid from an initially saturated bed (Fig. 1, Curve Ro), the final condition being an irreducible minimum fluid saturation Swr. Imbibition (Fig. 1, Curve A), further desaturation (Fig. 1, Curve R), and intermediate scanning curves have been studied to a lesser but increasing extent. This paper first considers the nature of the experimental points tracing the capillary pressure curves with respect to the modes and rates of mass transfer which are operative during the course of measurement. There are clear indications that the experimental points which describe these curves are obtained at apparent equilibria which are observed when viscous fluid flow has ceased; and any further changes in the fluid distribution are the result of much slower mass transfer processes, such as diffusion. Unless stated otherwise, this discussion applies to a stable packing of equal, smooth, hydrophilic spheres supported by a suction plate with water as the wetting phase and air as the nonwetting phase.
SPEJ
P. 15ˆ
A Computer Simulation of Gas Flow in Long Pipelines
Authors: Taylor T.D. , Wood N.E. , Powers J.E. 
Published: December 2007

Abstract
A computer program has been developed to simulate a gas transmission line operating under transient conditions. The program was developed by application of the basic mass and momentum balance equations. The nonlinear equations thus obtained were transformed by the method of characteristics and finite-difference techniques to make them suitable for machine computation. Three tests of the computer program were made. In each of these, the initial condition was assumed to be steady-state flow, the inlet density was held constant at the initial condition, and the outlet mass flow rate was varied with time. One test was theoretical in nature, but the others were made for direct comparison with actual field data. Results of the tests are presented in graphical form.

Introduction
Theoretical investigations of the transient flow of gas in long pipelines have been limited in number. In 1951, Olds and Sage developed a graphical method of solving the nonlinear flow equations describing transient gas flow in a long pipeline. Research in this field at the U. of Oklahoma was initiated by Nelson in 1956. Nelson utilized a computer to solve numerical equations involving a lengthy trial-and-error procedure, and his results have been reported in the literature. It does not seem likely that Nelson's method can be extended to the analysis of transient behavior of pipeline networks; therefore, the investigation to be discussed in this paper was undertaken to improve and extend the previous work. The following discussion presents, briefly:the basic differential equations governing transient flow,transformation of these equations into a form suitable for machine computation,role of boundary conditions in the calculations,a very brief description of the computer program which was developed to simulate the pipeline andresults of tests of the computer program.

DEVELOPMENT OF EQUATIONS

BASIC DIFFERENTIAL EQUATIONS
The isothermal flow of fluids can be adequately described by the mass and momentum balance equations as applied to the system under consideration. Using as a system a section of pipe having a differential length, the continuity equations were developed as follows. Mass balance:
.......................(1)
Momentum balance:
.......................(2)
where p = gas density, G = mass flow rate of gas, x = distance along pipe from system inlet, t = time from start of time interval of interest, gc = gravitational constant, R = gas constant T = gas temperature, absolute, M = gas molecular weight, D = pipe diameter, and f = Moody friction factor.
The following assumptions are involved in the development of Eqs. 1 and 2: constant temperature, rod-like flow, negligible effect of changes in elevation, no chemical or atomic reactions, single-phase fluid, pipe has constant cross-sectional area, and ideal gas.
SPEJ
P. 297^
Produced Water Management Strategy and Water Injection Best Practices: Design, Performance, and Monitoring
Authors: Abou-Sayed Ahmed S. , Zaki Karim S. , Wang Gary , Sarfare Manoj D. , Harris Martin H. 
Published: December 2007

Summary
Key factors in framing a produced water management (PWM) strategy include a company's internal and external environments, technology, and business drivers. Emerging trends for establishing an environment-friendly PWM position comprise adoption of these policies:
Move toward zero emissions. No discharge to surface or seas. Waste-to-value conversion. Incremental and progressive separation. Proactive efforts to influence partners, regulators, and environmental laws.
This paper covers technical approaches for addressing the production, separation, and disposal/injection segments of water injection and reservoir waterflooding procedures and the basis for selecting strategy components and PWM actions. Best practices result both from comprehensive assessments of current PWM tools and from the insights obtained from a decade-long joint industry project (JIP) on produced water re-injection (PWRI).
PWRI for waterflooding or disposal is an important strategy for deriving value from waste while preserving environmental integrity during exploration and production (E&P) operations. Advances in best practices and lessons learned for injector design, operation, monitoring, assessment, and intervention provide the basis for cost minimization and green operations. Facility and subsurface engineering are linked through PWM quality targets, pumping needs, injector completions, and facility constraints. Field cases and data mining results (Abou-Sayed et al. 2005) show the variation in injector responses and underline the key elements contributing to performance. Field evidence indicates that injec-tivities suffer in matrix injection schemes despite the injection of clean water. Alternatively, injectivity maintenance using untreated produced water is feasible.
The majority of injectors fracture during injection, thereby impacting facilities' statement of requirement (SOR), injector completion, sweep, and vertical conformance. This paper assesses fracture propagation during seawater and produced water injection and its impact on injector performance. Models depicting plugging of formations and fractures, vertical water partitioning, and well testing are discussed. Best practices are highlighted and the impacts on injection strategy outlined. Several field cases, as well as water injection design and analysis tools for quantifying the impact on flood and well performance, are presented.
Analysis of Buildup Tests With Short Producing Time
Authors: Soliman M. Y. 
Published: December 2007

Summary
Pressure buildup data with short producing time are often difficult to analyze. Although the semilog method, known as the Horner1 method, can be used, the drawdown type curve should not. Thus it is difficult to determine whether the semilog plot actually includes the correct straight line.
In this paper, a new log-log graph specially designed for a pressure buildup test with short producing time is suggested. This graph allows the user to determine easily the type of flow regime (linear, bilinear, or radial). Consequently, it can be used to detect the presence of the correct semilog straight line. The new graph can also be used to calculate the formation permeability or fracture conductivity in a fashion similar to the semilog method. The analytical models used to develop the new technique are presented. The models consider both well-bore storage and skin effect. A field example is presented and discussed. Use of the new technique to analyze a buildup test with short producing time is presented and briefly compared with the existing techniques.
A Method to Account for Afterflow at the Pulsing Well During Pulse Tests
Authors: Winston Hubert 
Published: December 2007

Abstract
The nature of wellbore storage is such that afterflow during a pulse test can affect the reservoir pressure performance and can lead to the calculation of erroneous values for formation transmissibility and storage. This is most likely to occur when the wells of interest are close together or when afterflow persists for a long time relative to the pulse length. This article describes a technique that was developed to account for the effects of afterflow at the pulsing well during pulse testing of a small production pilot. The technique is not general because it requires that a computer-generated simulation of each pulse test be made. An application of the method is given.
Effect of Surfactant Structure on Phase Behavior of Alkylxylenesulfonate/Crude-Oil/Brine Systems
Authors: Bolsman T. A. B. M. , Daane G. J. R. 
Published: December 2007

Summary
One of the major criteria for designing surfactants for micellar flooding is their effectiveness in stabilizing a middle-phase microemulsion under the conditions of the candidate reservoir. We studied the performance of linear alkyl-o-xylenesulfonates (Enordet™ LXS) with equivalent weights ranging from 345 to 472 with well-defined molecular structures.
We used information about a previously described quantitative relationship between the mole fractions of the individual surfactant components and their effect on the optimal salinity in surfactant/crude-oil/brine systems. This relationship makes it possible to calculate blend compositions that have near-optimal properties with respect to the required salinity at which the three phases—i.e., oil, microemulsion, and brine—occur. In this work, however, we have further refined the correlation between surfactant structure parameters and performance by including the effect of factors such as the mole-fraction distribution, the aromatic substitution pattern of the alkylxylenesulfonates, and the presence of the cosurfactant Enordet 3ES.
We studied the performance aspects of optimal salinity, the solubilization of crude oil and brine at the optimal salinity, and the sensitivity to divalent ions expressed as the "effectiveness ratio."
The data generated in this study make it possible to adjust the properties of a surfactant blend in relation to the characteristics of a crude-oil reservoir, thus minimizing the need for trial-and-error experiments.
Numerical Simulation of the Transient Behavior of Coal-Seam Degasification Wells
Authors: King Gregory R. , Ertekin Turgay , Schwerer Fred C. 
Published: December 2007

Summary
This paper describes the mathematical and numerical developments for a series of fmite-difference models that simulate the simultaneous flow of water and gas through dual-porosity coal seams during the degasification process. Models for unstimulated and hydraulically stimulated degasification wells are included in this series. The hydraulically stimulated wells are assumed to be intercepted by a single infinite- or finite-conductivity vertical fracture.
Practical Control of Timestep Selection in Thermal Simulation
Authors: Sammon P. H. , Rubin B. 
Published: December 2007

Summary
We present a new technique for estimating accumulating time truncation error in thermal reservoir simulation. The calculation uses only current reservoir information, thereby avoiding difficulties encountered by some past formulations, and is integrated easily into fully implicit reservoir simulators. We describe an error-controlled timestep selector based on this estimate as well as provisions for limiting the calculated timestep based on the imminent appearance or disappearance of a gas phase. We also provide a new technique for estimating the solution of certain Newtonian iterations. The algorithm is capable of calculating timesteps at the beginning of a simulation and when major well rate changes are specified.
The resulting timestep selector enhances simulator accuracy without increasing computational work and affords greater reliability through the reduction of failed timesteps.
A Laboratory Study of Chemical Reactions With Reservoir Sand in the Recovery of Petroleum by Alkaline Flooding
Authors: Lieu Van T. , Miller Samuel G. , Miller Steve 
Published: December 2007

Abstract
This paper presents the results of a laboratory study of the chemical reactions between alkaline chemical solutions and petroleum reservoir sand material. Long-term studies were made of alkaline solution flow through reservoir sandpacks. Analyses were conducted to determine the chemical compositions of the effluents.
The results obtained are related to the mineral content of the reservoir sand material. Individual chemical reactions of various minerals are discussed. It appears that mere is an important initial combination of rapid reversible adsorption and chemical reactions followed by slower nonreversible chemical reactions that later can assume great importance because of the long contact time that may prevail in flooding a petroleum reservoir.
This long-term alkali consumption is critical, because successful alkaline flooding must provide sufficient alkalinity to survive the time it takes to traverse the reservoir from injection well to production well.
Field Tests of the Stem-Induced Explosive Fracturing Technique
Authors: Young Chapman , Barker D. B. , Clark H. C. 
Published: December 2007

Summary
The explosive stem-induced fracturing technique has been field tested in over 20 producing oil wells in western Pennsylvania. The technique basically involves the placement of a primary explosive charge in an expendable rathole below the pay zone(s) to be fractured and of a solid gravel stem near the top of the pay zone to cause local fracturing through the dynamic reflection of the explosive gases. In the best cases, production increases realized with the technique are comparable to those obtained with conventional hydraulic fracturing in the area. A 35-mm downhole camera was developed and used to obtain photographs that show the absence of any vertical fracturing before the explosive treatments and well-developed vertical fractures in all zones designed to be fractured. This vertical fracturing is developed despite the fact that the in-situ stresses favor horizontal fracturing. The photographs also show that multiple radial fracturing, which might be expected with the high rates of the explosive loading, does not usually occur and that wellbore damage is less than predicted.
Semisubmersible Drilling Tender Unit
Authors: Chitwood James E. , McClure Alan C. 
Published: December 2007

Summary
The offshore industry has shown significant interest in deepwater production in the Gulf of Mexico, as evidenced by the large number of deepwater leases. This paper addresses an innovative method to control cost of field-development wells on deepwater leases. Drilling tender rigs have been economically attractive in shallow water depths. The limitations experienced by conventional tenders in deep water with regard to mooring and motions in a seaway can be overcome by use of a semisubmersible tender.
A Method for Drilling Moving Salt Formations—Drilling and Underreaming Concurrently
Authors: Holt Charles A. , Johnson Joseph B. 
Published: December 2007

Summary
Casing deformation opposite the Preuss salt formation in the Anschutz Ranch East (ARE) field of northern Utah has been a constant problem since the field was discovered in 1979. To improve hole geometry in the salt, an oil-based mud was used to drill a flank West Lobe well thought to have a thick, complex salt section.
After field-established salt-drilling techniques failed, a unique method of drilling and underreaming concurrently was employed and perfected. With modifications, the technique can be used to drill any moving formation.
Approximate Flash Calculations for Equation-off-State Compositional Models
Authors: Nghiem Long X. , Li Yau-Kun 
Published: December 2007

Summary
An approximate flash-calculation (AFC) method with an equation of state (EOS) is presented. The equations for AFC are obtained by linearizing the thermodynamic equilibrium equations at an equilibrium condition called the reference condition. The AFC equations are much simpler than the actual equations for flash calculations and yet give almost the same results. A procedure for generating new reference conditions to keep the AFC results close to the true flash-calculation (TFC) results is described. AFC is compared with TFC in the calculation of standard laboratory tests and in the simulation of gas-injection processes with a compositional model. Excellent results are obtained with AFC in less than half the original execution time.
Guidelines for Converting Steamflood to Waterflood
Authors: Hong K. C. 
Published: December 2007

Summary
This paper presents a set of guidelines that field engineers can use for the optimum conversion of maturing steamflood projects to waterfloods. The guidelines were developed from a simulation study of Chevron's oldest steamflood-followed-by-waterflood project, the Kern River 10-Pattern project in California. They have been validated against different reservoirs and operating conditions.
The simulation study showed that by judicious conversion of a steamflood to a waterflood as the steamflood matures, the cumulative net salable oil (cumulative oil produced minus oil used as steam generator fuel) can be maximized. The optimum time of conversion has been characterized in terms of eight performance variables that can be monitored in the field. A field engineer can use these characteristics or guidelines to estimate the optimum time of conversion and use this result to maximize the net salable oil production from his project.
The procedures used for developing the guidelines from the Kern River 10-Pattern project performance and for validating them against different reservoirs and operating conditions are presented. The recommended procedure for applying these guidelines to other fields is also discussed.
Bit Sticking Caused by Borehole Deformation
Authors: Dunbar M. E. , Warren T. M. , Kadaster A. G. 
Published: December 2007

Summary
The stress relaxation associated with drilling a hole in the earth causes the borehole wall to deform toward the center of the hole. Usually this deformation is inconsequential, but sometimes the deformations are sufficient to cause the borehole to be smaller than the bit. The problems associated with this phenomenon are related largely to the magnitude of the lateral earth stresses, formation mechanical properties, and drilling-tool geometry.