bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemistry and Rheology of Borate-Crosslinked Fluids at Temperatures to 300F
Authors: Harris Phillip C. 
Published: December 2007

Summary
This paper explains the variables involved in borate chemistry as they affect crosslink formation, stability, and breaking properties. The borate-ion concentration in solution is a function of pH and temperature. A method for calculating borate-ion equilibria is used to help establish the required final pH value for application of a borate-crosslinked gel at a specific temperature.

Introduction
Many of the properties of borate-crosslinked fluids can be explained in terms of the shift in borate-ion equilibria with pH and temperature. Syneresis, the process of forming a dense polymer mass and excluding liquid from the structure, is easily understood as a product of increased borate-ion concentration when a fluid is cooled. Proppant-settling behavior that is pH-dependent also can be explained. As the equilibrium concentration of borate ion increases with increasing pH, the number of network crosslinks increases and hence the proppant-settling rate decreases.
Rheological measurements from flow-loop and Fann Model 50 viscometers are used to help identify the chemical variables that control such fluid properties as crosslinking time, viscosity development, and the rehearing character of borate fluids. A new theological procedure using steady-state shear rate is presented for obtaining viscosity data for fluids used in fracture design programs.

Background
Borate-crosslinked fluids have been gaining popularity in the fracturing industry. Even though such fluids have been used for more than 20 years, new developments in borate-fluid technology are occurring rapidly, particularly with respect to high-temperature capability. For years, borate-crosslinked fluids were considered inexpensive, high-viscosity fluids limited to low temperature. More recently, wells up to 300F have been treated with borates. To understand the extension to high temperature, we should reconsider the chemistry of borate-crosslinked fluids.

Borate Crosslinking
Borate-crosslinked fluids used for fracturing consist of polysaccharide polymers crosslinked with borate salts. These gels are difficult to investigate with analytical instruments, so model diol chemical systems and model sugars have been used to study the formation of borate esters and crosslinking reactions. Borate crosslinks are viewed as rapid exchange equilibria of monoborate ion on the cis-diols of galactomannan polymers (guar).
Integrated Engineering Decision Making Through the Use of a Data Extract System
Authors: Alameda G. K. , Brink J. L. , Jarzombek L. S. , Maslanka P. M 
Published: December 2007

Summary
This paper describes Chevron U.S.A. Production Co.'s data extract system, CDX. CDX integrates our corporate mainframe databases with a set of ad hoc data analysis tools. Tools include statistical analysis software, database packages, and a widely used spreadsheet. CDX allows the user, through a single user interface, to access and retrieve data from a variety of databases written in industry-standard languages. CDX also allows access of large indexed data sets, such as Chevron's digital well-log archives. Data are delivered to the user's work environment—mainframe, workstation, or PC—ready to be loaded into ad hoc analysis programs or technical applications. This approach to system integration gives users the ability to mix, match, and reanalyze both technical and financial data in ways only experts could previously.
Examples of how CDX has increased our ability to manage business more effectively include analyzing individual wells and patterns for profitability and optimizing flood operations by generating maps of individual well plots. The benefits of CDX are numerous, considering the business pressures now in effect that drive companies harder than ever to reduce operating costs, increase production, and optimize property portfolios. CDX offers a way to realize the benefits of data integration without having to rewrite multimillion-dollar data systems immediately. CDX also provides an organized way to shift information systems, data, and work processes to the newer relational technologies. Lastly, information derived from operating CDX is allowing Chevron to plan and optimize new relational data models and information systems.
The Ability of Rate-Time Decline Curves to Predict Production Rates
Authors: Ramsay H.J. , Guerrero E.T. 
Published: December 2007

Although decline curves have wide use in petroleum engineering problems and have been used for many years, the available literature contains little statistical information comparing the ability of various types of decline curve equations to predict producing rates. Cutler and Nomoto both compared producing rates. Cutler and Nomoto both compared the exponential and hyperbolic equations and arrived at different conclusions. Cutler expressed a preference for the hyperbolic equation while Nomoto preference for the hyperbolic equation while Nomoto preferred the exponential equation. Shea, Higgins, preferred the exponential equation. Shea, Higgins, and Lechtenberg reviewed 347 California reservoirs and tested four decline curve equations. They reported that a coordinate relationship provided the best lit to production data in terms of a deviation factor from a least-squares fit. However, in taking a 5-year production history, extrapolating this over the next production history, extrapolating this over the next 5 years, and then comparing the results with the actual production for the second 5 years, the exponential curve gave the best fit. They did not test the hyperbolic equation. A study was made to test these and other equations against a statistical sample of broad geographic distribution. The equations tested were:
(1) Coordinate (2) Exponential (3) Hyperbolic (4) Reciprocal rate
(also harmonic)
(5) Reciprocal time (6) Reciprocal rate-time
The first three equations are decline curves commonly used. The last three equations were suggested by Pirson. Note that with the proper definition of the constants of integration. Eq. 4 is identical with the so-called harmonic curve:
.....................(7)
defined by Arps as a special case of Eq. 3 when b = 1. To obtain production data for the statistical sample, about 1,150 leases in 250 pools were reviewed. The sample consisted of production data from 202 leases having a geographical distribution as follows:
Number of State Leases Pools Formations Colorado 5 1 1Kansas 3 3 3Wyoming 5 2 2New Mexico 38 18 12North Dakota 33 7 1Oklahoma 46 25 18Texas 72 20 13202 76 50
When combining a group of equations, the lowest percent error for each lease was selected from results percent error for each lease was selected from results of applying each equation in the group. For example, if a lease had percent errors at 10.34, 5.17 and 15.45 for Eqs. 2, 3 and 4, respectively, the error of 5.17 corresponding to Eq. 3 was selected.
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Estimating Perforation Flow Performance From Variations in Indentation Hardness
Authors: Halleck P. M. , Poyol Edmund , Santarelli F. J. 
Published: December 2007

Summary
We mapped the hardness of the rock surrounding shaped-charge perforations with an indentation technique based on the Brinell method. We fired conventional perforators (3.2-g explosive weight) into a friable sandstone (approximately 6.9 MPa unconfined compressive strength) under 10.3 MPa effective stress. We observed substantial reductions in hardness extending more than 10 cm away from the perforation tunnel. The severity and extent of the damage was not uniform and was greatest near the perforation at the entrance hole, decreasing toward its tip. A comparison with a similar test with a drilled hole demonstrated that the observed damage was caused by the impact of the shaped-charge jet on the rock. The extent of the damage was independent of the diameter of the rock specimen used during the test. By assuming that permeability reduction is proportional to mechanical damage (i.e., hardness reduction), we obtained numerical simulations of flow rate and distribution. The calculated flow rates were consistent with those measured after perforating the samples. Careful analysis of the data suggested that the mechanical damage and permeability reduction were related to increases in finer particle sizes and smaller pore sizes that were observed by other workers. These led to increased tortuosity in the flow paths.
The classic vision of a thin, uniform crushed zone with reduced permeability surrounding the perforation tunnel did not seem to apply in the case of more friable materials. The calculated permeability map suggested that much of the flow occurred at the perforation tip for such rocks, indicating that downhole conditions were probably better simulated by linear-flow-rather than radial-flow-model targets. Finally, the radial extent of the damaged zone around the perforation tunnel raised questions concerning the interaction between adjacent perforations in a vertical plane when large shot densities were used.
Determining and Averaging Gas Reservoir Pressures
Authors: Doyle R.E. , Young T.S. 
Published: December 2007

The results of this study indicate that the nearest fit to a linear gas material balance plot (the best estimate of initial gas in place) is obtained by correcting the estimated average well pressure for asymmetrical drainage effects, then weighting the individual average pressures by the pore volume drained by each well. A significant error may result in the estimated gas in place if geometric effects or asymmetrical drainage for the individual wells is not considered. This study is confined to one of the major Wilcox gas condensate sandstone reservoirs under the Sheridan field, Colorado County, Tex. Production is from 29 irregularly spaced wells located in the central two-thirds of the reservoir. The last one-fourth of the production period under consideration was influenced production period under consideration was influenced by transient drainage effects.
Production acceleration caused a sustained period of transient pressure behavior that resulted in an erratic plot of the ratio of average pressure/gas deviation (P/Z) vs cumulative production. By contrast, the gas material balance curve should be linear for a volumetric reservoir and should not be affected by transient flow if average reservoir pressure can be determined accurately. The pressures used to prepare this performance curve were based on radial flow assumptions and rate weighting techniques.
Similar material balance curves were prepared by estimating the pore volume and area for each well from the linear or semisteady-state portions of pressure-time plots. These data resulted in three pressure-time plots. These data resulted in threeadditional P/Z plots: geometrically corrected; pressure weighted by both Pore volume and production rates; and a pore volume weighted pressure based on radial drainage.
Three indicators were used to measure the effectiveness of the four techniques: the magnitude of the standard deviation; a comparison of the extrapolated and actual initial pressure; and the shape of the performance curve in the anomalous region. The first performance curve in the anomalous region. The first two of these indicators are presented in Table 1 and the third is illustrated graphically in Fig. 1.
It is apparent that volumetrically weighting the individual average well pressures is superior to rate weighting for either method of determining average pressure. This is to be expected since wells draining pressure. This is to be expected since wells draining this reservoir have different rates of pressure decline due to variable extent of formation damage and asymmetrical well drainage geometry. In addition, it is clear that smaller standard deviations result if the effects of asymmetrical (non-radial) drainage are considered.
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Field Experiment Gathers Friction-Pressure Data for CO2-Energized Fluids
Authors: Tan H. C. , McGowen J. M. , Ridens J. C. , Sandy J. M. 
Published: December 2007

SummaryA field experiment was conducted on a well with 10,000 ft of 3½-in., 12.9-lbm/ft tubing to gather friction-pressure data for CO2-energized fluids. Seventy-three stages were pumped at various rates, gel concentrations, proppant concentrations, and CO2 qualities to gather sufficient data for modeling and for correlation development. Four side-pocket bundle carriers, with two electronic memory gauges per carrier, were installed at 2,500-ft intervals to monitor pressure and temperature. Four computer data-acquisition systems were used to confirm the integrity of the data collected. The actual friction data that were collected demonstrate the effects of treatment rate, gel concentration, CO2 quality, proppant concentration, and wellbore depth. This information will help researchers better understand the friction-pressure behavior of CO2-energized fluids and should enhance treatment diagnostics, the design of friction-pressure correlations, and existing friction-pressure correlations.
Gas Pricing in Developing Countries: A Case Study of Pakistan
Authors: Sohail H.M. , Abid M.S. , Ansari A.M. 
Published: December 2007

Summary
Pakistan, a developing country, has gone through various phases of formulating gas pricing policies during its 40-year history of natural gas production and consumption. This paper identifies critical factors that influenced gas pricing policies in Pakistan and adverse effects experienced when any of these factors was not given proper consideration. For instance, on the producer's side, discounted pricing formulas discouraged further exploration and development, leaving high-potential areas unexplored and discovered fields dormant for more than a decade. On the consumer's side, subsidized gas prices encouraged consumption to rise steeply without new discoveries to offset additional surplus consumption. The paper also discusses various short- and long-term variables that should go into a gas pricing policy for developing countries. References to recent policies are also given, indicating how these variables were incorporated in real terms. The conclusions and recommendations, based on Pakistan's long experience with the gas industry, should be useful for other oil-importing countries rich in indigenous gas resources.

Introduction
The development of the gas industry in Pakistan can be traced to 1952, when a large gas discovery was made at Sui. However, the controlled and artificially low gas price initially allowed to producers adversely affected the future of gas exploration and development. This resulted in an energy imbalance, which continued to threaten the economic growth of the industry until recently.
This paper discusses the gas pricing trends during the 40-year history of the natural gas industry in Pakistan. The short-term policy objectives and long-term effects of this pricing policy are also discussed. Using Pakistan as a case study, this paper identifies the major factors that significantly affect the gas pricing framework of a developing country. Though the relative influence of these factors may vary from country to country, their overall importance holds true for all energy-importing developing countries that have indigenous natural gas resources.
Paraffin Deposition from Refined Wax-Solvent Systems
Authors: Patton Charles C. , Casad Burton M. 
Published: December 2007

Abstract
Paraffin deposition from several relined wax-solvent systems was studied by using a coldspot test apparatus The purpose of the investigation was to determine the effect of surface roughness, plastic coatings and solution composition on the plastic coatings and solution composition on the amount of deposition. No correlation was observed between surface roughness and deposit weight. The wax composition determined whether or not a given deposit remained on a given surface. Normal paraffin waxes of lower molecular weight formed paraffin waxes of lower molecular weight formed deposits that sloughed or slid off smooth steel or plastic coated surfaces and flaked off roughened plastic coated surfaces and flaked off roughened steel or plastic coated surfaces. Wax of a higher molecular weight, containing more microcrystalline material, formed deposits that did not slide or flake off either smooth or roughened steel or plastic coated surfaces. Plastic coatings decreased deposit weights by 30 percent or more for the higher molecular weight wax due to thermal insulation. Deposit weight decreased with stirring rate and increased with time and temperature differential.

Introduction
Why paraffin adheres to a surface has long been a point of discussion. Two theories that have evolved are summarized as follows.

WETTABILITY OR FREE SURFACE ENERGY
"As paraffin is deposited on a surface, it is held in place by adsorption forces. These adsorption forces are dependent upon the bee surface energy possessed by both the paraffin and the surface. As possessed by both the paraffin and the surface. As the free surface energy of the plate or surface is reduced, a resultant decrease in the adsorption force holding the paraffin to the plate or surface takes place. This causes a decrease in the amount of paraffin which can be retained on the plate surface for the flow conditions present."

SURFACE ROUGHNESS
"The results obtained in this investigation indicate that wax does not adhere to the pipe wall but is held in place by surface roughness and/or irregularities. As a wax particle grows along the pipe wall and out into the oil stream, the force pipe wall and out into the oil stream, the force tending to move it out of the tubing would increase. The smoother the surface, the more easily the embryonic deposit would be removed from the surface… Thus, it is concluded that wax does not adhere to steel but that deposits which form on steel surfaces are held in place by surface roughness." Or stated more concisely, "Paraffin deposition on metallic or nonparaffinic plastic surfaces at a given temperature is governed by surface roughness." The purpose of this investigation was to determine the effect of surface roughness, plastic coatings and solution composition on paraffin deposition from refined wax-solvent systems. Transparent refined systems were used so that the process could be studied visually. A cold spot test apparatus similar to that used by Hunt and Jorda was used.
Mathematical and Numerical Properties of Control-Volume, Finite-Element Scheme for Reservoir Simulation
Authors: Eymard Robert , Sonier Fernand 
Published: December 2007

Summary
This paper presents the mathematical properties of a control-volume, finite-element (CVFE) scheme. We show that appropriate constraints on finite-element grids and convenient definitions for volumes and transmissibilities lead to a convergence property for the CVFE scheme. This convergence property proves that use of the CVFE scheme is mathematically correct for reservoir simulation. With the control-volume concept, the local balances of each component are fully satisfied. Because the discretized equations resulting from the scheme can be solved by classic methods, the CVFE scheme can be implemented easily in a general-purpose simulator. In the implementations in this paper, we use prismatic finite elements for 3D full-field simulations and triangles for 2D simulations. The grid is generated with automatic techniques, popular in structural engineering, resulting in numerical diffusion that is as isotropic as possible; therefore, grid-orientation effects are controlled and accuracy is easily improved through natural grid refinement. Examples show that, for the same accuracy, computational costs are lower for results obtained with the CVFE scheme than for those obtained with finite-difference grids. The CVFE scheme is an excellent alternative to flexible gridding techniques used in finite-difference simulators because the entire reservoir can be gridded as required, without use of special techniques for local grid modifications.
Interpretation of Calculated Forces on Sucker Rods
Authors: Lea J. F. , Pattillo P. D. , Studenmund W. R. 
Published: December 2007

Summary
An examination of the forces acting on a sucker rod string and the relation of those loads to the tendency of a rod string to buckle is presented. Emphasis is placed on the fact that effective, as opposed to true force is the governing parameter for rod buckling. Sample calculations indicate the importance of effective tension in both up-hole rod analysis and near pump rod and sinker bar design.
Application of Artificial Neural Network to Pump Card Diagnosis
Authors: Nazi G.M. , Ashenayi Kaveh , Lea J.F. , Kemp Frank 
Published: December 2007

Abstract
Beam pumping is the most frequently used artificial lift technique. Down hole pump cards are used to evaluate performance of the pumping unit. Pump cards can be generated from surface dynamometer cards using one-dimensional wave equation with viscous damping, as suggested by Gibbs.
Pump cards contain significant information describing the behavior of the pump. However, interpretation of these cards is very tedious and time consuming. Hence, an automated system capable of interpreting these cards is very useful.
This work presents a DOS based computer program capable of correctly classifying pump cards. The program uses a hybrid artificial neural network (ANN) to identify significant features of the pump card.
The hybrid ANN utilizes classical and sinusoidal perceptrons. The network is trained using error back propagation technique.
The program has been able to correctly identify problems in over 100 different training and test pump cards. The ANN requires total of 80 data points as input. Sixty data points are collected from the pump card perimeter itself and the remaining 20 data points represent the slope at selected points on the pump card perimeter.
The problem conditions are grouped into distinct classes such as malfunction anchor tubing, fluid pound, gas interference, and worn traveling valve. The network is capable of identifying one or more of these problem conditions for each pump card. Several examples will be presented and discussed.

Introduction
Sucker-rod pumping system is a very popular means of providing artificial lift for wells. It is estimated that 90 percent of artificially lifted wells use sucker-rod pumping systems.
In order to assure proper operation of these systems it is necessary to monitor them on a regular basis. This is done by means of a dynamometer which is attached to the polished rod of the pumping unit. The plot of load versus position generated by the dynamometer is known as a surface card.
Using the technique proposed by Gibbs this surface card can be used to obtain down hole "pump card". The pump card presents the load versus position at the pump down hole instead of the load versus position at the polished rod on the surface.
The shape of the pump card can be used as a diagnosis tool. For example, when the pump is functioning properly and pumping to its full capacity the pump card will have a rectangular shape. When the pump capacity is not being fully utilized then we may have a condition called "fluid pound".
The petroleum industry is in the process of automating the control of pumping wells. Computers are being used to continuously monitor the pump and transmit data to a central office for further analysis. The shear volume of data received makes it necessary to develop tools for automatic analysis of the pump cards.
Various pattern recognition techniques have been used to analyze the down hole pump card. Traditional techniques require significant processing time.
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