bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase Envelope Calculations for Hydrocarbon-Water Mixtures
Authors: Lindeloff Niels , Michelsen Michael L. 
Published: December 2007

Summary
The present work describes how the pressure-temperature phase diagrams for hydrocarbon-water mixtures can be calculated. This requires a thermodynamic model that can account for the polar interactions caused by the aqueous compounds and an algorithm that can trace the two-and three-phase boundaries encountered in such systems. Models and algorithms that can handle this task are described. The paper further describes a number of examples in which the methods are applied.
Fatigue Analysis of the Cognac Platform
Authors: Kinra R.K. , Marshall P.W. 
Published: December 2007

This paper describes preliminary and detailed fatigue analyses of the 1,000-ft-deep Cognac platform. Dynamic structural analysis is used to generate local member stress transfer function data, and probabilistic spectral techniques are employed to evaluate long-term stress statistics and fatigue lives using Miner's cumulative damage rule. Directional spreading of wave energy is considered in the analysis.

Introduction
The Cognac platform is located in 1,025 ft (310 m) of water in the Gulf of Mexico. Fatigue damage considerations played an important role in the structural design of the platform. Many of the heavy-wall joints in the structure were controlled by fatigue rather than by punching shear under the design wave. The reason is that the natural period of the Cognac platform is in the 4- to 5-second range, whereas the natural periods of other structures in the gulf are generally less than 2 seconds. Thus, the Cognac platform responds dynamically to everyday waves in the gulf, which typically have zero-crossing periods between 3 to 5 seconds. In comparison, other Gulf of Mexico structures tend to respond statically. To make matters more difficult, the hydrodynamic damping due to low waves is very small. Recent studies by Ruhl indicate that the total damping - including structural, foundation, and hydrodynamic contributions - may be only about 20% of critical for platform response in low sea states. Low damping values result in large dynamic amplifications when the period of the forcing function (the wave period) is close to the natural period of the structure. The combination of low damping and a natural period close to that of frequently occurring Gulf of Mexico sea states results in a fatigue-sensitive structure .The steps taken to ensure the integrity of the structure against fatigue damage consisted of (1) a preliminary fatigue analysis that served as a basis for the design of the structure and (2) a detailed member-by-member check of the final design using probabilistic techniques described here.

Preliminary Fatigue Considerations
The overall strategy of fatigue design consists of a two-stage approach:initial design of members and joints using allowables derived from generic analysis, andfinal hot-spot by hot-spot fatigue analysis,
which requires that all details of the structure be established a priori.Of necessity, the detailed analysis is done after all other design work has been completed and often after fabrication has begun. If any areas with undesirably short calculated fatigue lives are found, these can be upgraded - either by grinding welds to improve fatigue performance, locally building up the section thickness to reduce cyclic stress, or making other minor modifications.This general approach has been used on several platforms in the North Sea, the Gulf of Mexico, and offshore southern California.
JPT
P. 374＾
High- and Low-Cycle Fatigue Behavior of Prestressed Concrete in Offshore Structures
Authors: Gerwick B. C. , Venuti W. J. 
Published: December 2007

Abstract
The expanding use of prestressed concrete in offshore structures, both fixed and floating, in increasingly hostile environments has generated intense interest in its fatigue endurance capabilities, even though no known fatigue problems have arisen in actual structures. Although concrete does suffer progressive loss of strength with increasing number of cycles, a comparison of the Wohler curves developed on the basis of laboratory tests with the probable distribution of compressive stresses during a service life in an environment such as the North Sea shows extremely low cumulative usage at the high-cycle end of the spectrum. However, significant damage can occur at the low-cycle, high-amplitude end of the spectrum under a relatively small number of cycles of very high magnitude. This damage is displayed by a reduction in stiffness and by rapidly increasing axial and lateral strains that lead to cracking and spalling.
Repeated cycling into high compressive ranges causes a substantial increase in creep, reducing the effective prestress. Confining reinforcement resists lateral deformation and delays compressive fatigue failure. Cycling into the tensile range a large number of times can produce cracking due to tensile fatigue at about half the static tensile strength. Cracking also can occur due to overload, accident, construction procedures, and thermal strains. Repeated excursions of submerged concrete into the crack-opening range leads to pumping of water in and out of the crack and hydraulic wedging, leading to concrete splitting.
Cracking subjects the reinforced and prestressed steel to cyclic tension. Loss of bond ensues and may lead to eventual fatigue failure. Adequate endurance can be ensured by prestressing to avoid a large number of cycles extending into the crack-opening range and by providing adequate percentages of steel across the section plus transverse and confining steel.
Cyclic membrane shear may produce diagonal tension cracking at about half the static strength. Conventional reinforcing in an orthogonal grid pattern is very inefficient in resisting such cracking. Crack widths grow rapidly. Repeated loading may lead to abrasion of concrete surfaces and failure of the steel due to combined axial force and bending. Vertical prestress is an efficient and practical method of resisting high-amplitude cylic shear.
For the typical concrete sea structure, high-cycle, low-amplitude, cumulative fatigue is not a significant problem. However, low-cycle, high-amplitude fatigue requires consideration, especially when there are numerous cycles into the tensile cracking range. In this latter case, fatigue of the steel and/or concrete may occur unless adequate amounts of steel are provided to ensure that crack widths and steel stresses are kept within allowable values.
Combining Pulsed Neutron Spectroscopy and LWD Resistivity for Analysis Behind Casing in Small Holes
Authors: Beaumont-Smith N. , Webber G. D. , Shepherd P. J. , Kalyanaraman R. S. 
Published: December 2007

Summary
Formation analysis from behind casing is gaining more relevance in assessing reservoirs, not only in aging fields but also in new wells completed either without the full complement of openhole petrophysical measurements or with openhole measurements of inadequate quality. Before this technology was available, formation evaluation in freshly drilled holes was dependent on the availability of openhole log measurements. This paper discusses field examples in which reservoirs were evaluated without a full suite of openhole log measurements. Examples from two sidetracks in a mature North Sea field supported by water injection are presented. The small hole size limited openhole data acquisition to resistivity and gamma ray (GR) measurements, which were acquired using logging-while-drilling (LWD) technology.
In both cases, pulsed neutron (PN) measurements were recorded through casing to augment the existing data. Porosity and formation sigma (macroscopic thermal neutron capture cross section) measurements were obtained. Fluid saturations were computed using this porosity and the LWD resistivity. Saturations also were computed from the carbon/oxygen measurement, and these agreed with the resistivity-based answers. Lithology analysis was performed using elemental spectral capture yields and was reliable and consistent fieldwide.
The results show that, in a mature oil field, PN measurements can provide a complete lithology and saturation analysis in circumstances in which insufficient openhole petrophysical measurements are available.
A Linear Programming Model for Scheduling Crude Oil Production
Authors: Lee A.S. , Aronofsky J.S. 
Published: December 2007

Introduction
In recent years considerable progress has been made in the development and application of mathematical techniques for the solution of certain problems involving economic "strategies". Such a problem might involve, for example, the scheduling of shipments of a commodity from a number of sources to a number of destinations. The object would be to schedule the shipments in a manner so as to satisfy the destination requirements and at the same time minimize the transportation costs. The solution to such a problem is not necessarily intuitively obvious. The "obvious" solution is frequently far from optimum. If the shipments are to be made from, for example, only two sources to four destinations, the optimum schedule is readily found. However, if shipments are to be made from, say, 10 sources to several hundred destinations, even a competent and experienced scheduler may spend considerable time in finding a reasonable answer. Even then he is not sure that he has the optimum solution. Furthermore, he has no way of knowing how far from optimum the answer is. Consequently, he does not know whether he should accept this solution or seek a better one.
Prior to the advent of large high-speed digital computers, little more could be done with such problems because of their great size and multiplicity of possible solutions. A problem involving 20 sources and 50 destinations would require choosing, from a very large number of possible combinations, the optimum combination of 1,000 variables. The best one could do was to utilize intuition, extrapolation from past experience, and other non-exact approaches. With a high-speed computer, however, such problems can be solved providing a reasonable computational procedure (or algorithm) can be utilized. The purpose of this paper is to describe such a procedure (linear programming) and to apply this procedure to a production scheduling problem.
A Systematic Approach for Characterizing Hydrocarbon Solids
Authors: Jamaluddin* A. K. M. , Nighswander J. , Joshi N. 
Published: December 2007

SummaryThe potential for hydrocarbon solid formation and deposition adversely affecting flow assurance in deepwater production systems is a key risk factor in assessing deepwater developments. To reduce this risk, a systematic approach to defining and understanding the thermodynamic factors impacting flow assurance is required. The development of experimental techniques to provide this information is a current focus of attention in the reservoir fluid-phase behavior community. This paper provides a systematic experimental approach to characterization of the hydrocarbon solids in crude, and the impact of this knowledge on potential production and flow-assurance strategies.
Producer/Injector Ratio: The Key to Understanding Pattern Flow Performance and Optimizing Waterflood Design
Authors: Hansen C. E. , Fanchi J. R. 
Published: December 2007

Summary
When designing a waterflood, the important aspect of processing rate with respect to pattern selection has not been addressed adequately in the literature. It has not been possible, using the existing analytical background, to determine and compare the flowrate performance of all the patterns for any given rock/fluid (mobility) system. While general two-phase equations exist for the five-spot and line-drive patterns, flow equations for other patterns either have not been presented (e.g., the seven-spot) or are not sufficiently general (e.g., the nine-spot) to apply to all mobility conditions. A general treatment of skin effect also has not been given.
This paper presents a new, comprehensive analytical treatment of pattern flow for isotropic, homogeneous reservoirs that applies to all patterns and mobility conditions. This is made possible by a new equation for the volumetric average reservoir pressure of regularly spaced, repeated patterns. The new formulas demonstrate how the producer/injector ratio (P/I) controls reservoir pressures and flow rates and (for the first time) allow the differences in the flow capacity of patterns to be quantified. The mobility characteristics that control flow rates are described fully by a newly defined total mobility ratio, MT. The form of the new equations allows for modifications for skin effect and reservoir heterogeneity. We show how skin effect can act disproportionately with injectors and producers because of its interaction with P/I and MT.
A Report on the Displacement Log
Authors: Winn R.H. 
Published: December 2007

Introduction and History
Campbell and Martin described a new exploratory logging tool which was developed as the result of a new concept of the phenomenon that takes place when a porous formation containing mobile hydrocarbons and irreducible interstitial water is invaded by mud filtrate. They postulate that invasion will create a bank of interstitial water between the flushed zone and the undisturbed formation. This postulate was confirmed by Wyllie.
Thus, if Rmf is greater than Rw and mobile hydrocarbons are present, the resistivity profile with increasing radii from the borehole is high:low:high, as shown in Fig. 1. If mobile hydrocarbons are absent, the bank of interstitial water is indistinguishable from the undisturbed formation and the resistivity profile, when Rmf is greater than Rw, is high:low, as shown in Fig. 2. The zone containing the bank of interstitial water and residual oil was named the "low zone".
Campbell and Martin conducted extensive electrolytic wedge and resistivity analog model studies to select a logging system that would reflect the presence or absence of the low zone. The system they selected was that of a family of lateral curves. The model studies indicated that the presence of a low zone could be detected in approximately 60 to 70 per cent of the producing sand reservoirs with a family of lateral curves provided that the sonde effectively occupies 90 per cent of the diameter of the hole. These studies were conducted with Di = 5d. The presence or absence of the low zone is best determined by a plot of the apparent resistivity vs spacing as shown in Figs. 3 and 4. A dip or inflection in the profile that repeats at successive depth intervals is considered diagnostic. To reduce the shunting effect of the hole and mud, a sonde of insulating material that is surrounded by a series of flexible rubber bumpers was designed. The bumper efficiency is considered to be the ratio of the bumper diameter to the hole diameter. Field tests conducted by Campbell and Martin on 10 wells with a tool that provided for station readings indicated that dips or inflections could be detected in 19 out of 25 known producing zones.
Determination of Thermal Conductivity of Soils: A Need for Computing Heat Loss Through Buried Submarine Pipelines
Authors: Rawat P. C. , Agarwal S. L. , Malhotra A. K. , Gulhati S. K. , Rao G. Venkatappa 
Published: December 2007

Abstract
An important parameter required for computing heat loss through buried submarine pipelines transporting crude oil is the thermal conductivity of soils. This paper describes an apparatus designed for determination of the thermal conductivity of soils at the desired moisture/density condition in the laboratory under steady-state conditions. Experimental results on the three soils studied show that thermal conductivity increases as dry density increases at a constant moisture content and that it increases as water content increases at constant dry density. These results confirm the trends isolated earlier by Kersten,1 The experimental results are compared with the available empirical relationships. Kersten's relation1 is observed to predict the thermal conductivity of these soils reasonably. The predictions from Makowski and Mochlinski's relation (quoted by Szilas2) are not good but improve if the sum of silt and clay fractions is treated as a clay fraction in the computation.
Artificial Neural Network Models for Identifying Flow Regimes and Predicting Liquid Holdup in Horizontal Multiphase Flow
Authors: Osman El-Sayed A. 
Published: December 2007

SummaryThis paper presents two artificial neural network (ANN) models to identify the flow regime and calculate the liquid holdup in horizontal multiphase flow. These models are developed with 199 experimental data sets and with three-layer back-propagation neural networks (BPNs). Superficial gas and liquid velocities, pressure, temperature, and fluid properties are used as inputs to the model. Data were divided into three portions: training, cross validation, and testing. The results show that the developed models provide better predictions and higher accuracy than the empirical correlations developed specifically for these data groups. The developed flow-regime model predicts correctly for more than 97% of the data points. The liquid-holdup model outperforms the published models; it provides holdup predictions with an average absolute percent error of 9.407, a standard deviation of 8.544, and a correlation coefficient of 0.9896.
Chemical Osmosis, Shale, and Drilling Fluids
Authors: Schlemmer R. , Friedheim J. E. , Growcock F. B. , Bloys J. B. , Headley J. A. , Polnaszek S. C. 
Published: December 2007

Summary
This paper describes continuing efforts to develop a water-based drilling fluid that will provide the osmotic membrane behavior and wellbore stability of an oil-based drilling fluid. A pore-pressure-transmission technique in use for several years as a tool to measure osmotic behavior has been refined for improved measurement of changes in shale permeability and pore pressure in response to interaction with drilling fluids. Conventional invert-emulsion and water-based drilling fluids containing selected additives were tested with outcrop and preserved shale specimens using an innovative screening method.
Observed pressure differences across each shale specimen were compared with the values predicted by osmotic theory. From this comparison, an empirical concept of "membrane efficiency" was developed. Three distinct types of "membranes" are postulated to describe the interaction of various drilling fluids with shales. Type 1 membranes are generally characterized by coupled flows of water and solutes between fluid and shale. Type 2 membranes greatly reduce the near-wellbore permeability of shale and restrict the flow of both water and solutes. Type 3 membranes transport water more selectively, but shale permeability and fluid chemistry may alter performance measurements. Invert-emulsion fluids tend to form efficient, Type 3 membranes; however, under certain conditions, these fluids can yield lower capillary pressures than described previously and invade the interstitial fabric of high-permeability shales.
Several water-based mud formulations were prepared that achieve approximately one-quarter to one-half the measured osmotic pressure of a typical oil-based mud (OBM). Fluid additives that supplement or reinforce a Type 1 membrane, such as saccharide polymers (especially in combination with calcium, magnesium, or aluminum salts), can induce relatively high efficiencies. As expected, fluids that form a Type 2 membrane, such as silicate and aluminate muds, provide the highest membrane efficiencies.
A Mixed-Wet Hysteretic Relative Permeability and Capillary Pressure Model for Reservoir Simulations
Authors: Delshad M. , Lenhard R. J. , Oostrom Mart , Pope G. A. 
Published: December 2007

Summary
A crucial component of all multiphase flow models is the relationship among relative permeabilities, fluid saturations, and capillary pressures. Relative permeability and capillary pressure parametric models can be very useful for predicting fluid behavior in porous media. However, relative permeabilities and capillary pressures used in oil reservoir simulators are commonly determined through interpolation between laboratory measurements. A problem with this approach is that the relations are valid only for the specific saturation path measured. Therefore, simulations of oil production using different saturation paths from those measured are likely to be in error and can limit the investigation of alternative production scenarios. In this paper, saturation-history-dependent relative permeability and capillary pressure functions for two-phase flow in mixed-wet rocks are discussed. Relative permeabilities are predicted by integrating a pore-distribution model between limits that reflect how oil and water are distributed in mixed-wet porous media. The proposed model was tested against mixed-wet capillary pressure data. The model then was incorporated in the U. of Texas Chemical Compositional Simulator (called UTCHEM) to compare waterflood simulations in water- and mixed-wet reservoirs. The simulation results agree qualitatively with laboratory core and field observations. The model and its implementation also were validated against a sandpack experiment.
Determining Fracture Closure Pressure in Soft Formations Using Post-Closure Pulse Testing
Authors: Upchurch E. R. 
Published: December 2007

Summary
This paper discusses the theory and application of a pressure-pulse testing technique to determine the fracture closure pressure (Pc) in soft formations. This technique is intended for use only after a data fracture has been pumped and is closed. Implementing the pulse technique post-closure rather than while the fracture is still open allows it to be used as an independent determination of Pc without diminishing the accuracy of the fluid leakoff coefficient (CL) determined from the data-fracture. Previous pulse-testing techniques1 require pumping into a fracture while it is still open. This practice reduces the accuracy of CL by altering the time necessary for the fracture to close (tc). Furthermore, previous pulse-testing techniques yield only a possible range for Pc, whereas the post-closure pulse technique yields a better-defined, singular value of Pc.
The accuracy of post-closure pulse testing is validated with several field examples from a soft formation on Alaska's North Slope by comparing a definitive Pc determined using pressure decline analysis with Pc determined from post-closure pulse testing.