bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concrete FPSO
Authors: Harris R. J. S. , des De´serts Loic , Kenison R. C. , Snell Richard , Kerr David 
Published: December 2007

Summary
The paper identifies the advantages, features and applicability of a concrete hull for an FPSO and the issues related to project execution. For those considering the options for other field developments, the paper identifies the conclusions and the work on which these were based. The content of the paper is based on extended studies on the advantages, design features and feasibility of fabrication of this new design of the floating production storage and offloading facility (FPSO) hull. This work formed part of British Petroleum's (BP's) review of options for the development of their Schiehallion field in 375 m water depth West of Shetland, the Atlantic Frontier. The conceptual design of the vessel hull was carried out with the objective of providing the best solution for a concrete FPSO for BP's application. This included consideration of capital cost, system availability, operating costs, HSE aspects, decommissioning and disposal. The flexibility ofthe concept, e.g., for addition and modification during service, were also examined. The design process was taken to the stage where these matters had been examined and the design has approval in principal for certi- fication. During the design process the mathematical modeling of vessel motions and mooring forces were confirmed in tank tests. BP participated in the proof of concept, retaining the concept on their final short list of two options for the field development. It was concluded by all parties that this new concept had been fully examined and proved technically.
New Perforation Pressure-Loss Correlations for Limited-Entry Fracturing Treatments
Authors: El-Rabba A. M. , Shah S. N. , Lord D. L. 
Published: December 2007

Summary
Estimating the perforation pressure loss is an essential part in the design and analysis of hydraulic fracturing treatments. Accurate determination of perforation pressure loss for the rheologically complex fracturing fluids being used today can best be achieved through experimental study. Investigation of the perforation pressure loss for linear polymer solutions, crosslinked gels, and fracturing slurries has been conducted at the Fracturing Fluid Characterization Facility since 1994. Using the data acquired from these experiments, new correlations are developed to estimate the coef- ficient of discharge used in the orifice equation that governs the perforation pressure loss. The correlations can be used to accurately predict the coefficient of discharge for linear polymer solutions and titanium/borate-crosslinked gels. In addition, the slurry correlation can be utilized to determine the dynamic change in the coefficient of discharge for fracturing slurries due to erosion. The presented correlations are developed such that they can easily be incorporated into current fracturing simulators.
Impact of Fluid Selection on High-Permeability Fracturing
Authors: Aggour T. M. , Economides M. J. 
Published: December 2007

Summary
High permeability fracturing has become a major well completion technique both for production rate increase and, especially, for pressure drawdown decrease. Today, this type of treatment is the main means of sand control in some petroleum regions. Several of these treatments which are characterized by short lengths and, often, disproportionate widths, have been reported to exhibit positive post-treatment skin effects. This can only be the result of fracture face damage. This paper indicates that if the extent of fracturing fluid invasion is minimized, the degree of damage (i.e., permeability impairment due to filter cake or polymer invasion) is of secondary importance. Thus, if the fluid leak-off penetration is small, even severe permeability impairments can be tolerated without exhibiting positive skin effects. While the first priority in designing fracture treatments should be to maximize the fracture conductivity, it is recommended that in high permeability fracturing, high polymer concentration cross-linked fracturing fluids with fluid loss additives and breakers should be used. Experimental work corroborates these contentions.
Influence of Effective Stress on the Acoustic Velocity and Log-Derived Porosity
Authors: Khaksar Abbas , Griffiths C. M. 
Published: December 2007

Summary
Experimental studies indicate that when effective stress increases, compressional wave velocity in porous rocks increases. Reservoir pressure reduction, resulting from hydrocarbon production, increases effective stress. For a rock with a given porosity the sonic log may show decreasing values as the pressure in the reservoir decreases. This in turn may lead to underestimation of the actual porosity of the reservoir rocks in low pressure reservoirs. The range of such underestimation for liquid saturated reservoirs may not be significant, but since the influence of effective stress on velocity increases as fluid saturation changes to gas, porosity underestimation by conventional velocity-porosity transforms for gas bearing rocks may increase. Examples are taken from partially depleted gas reservoirs in the Cooper basin, South Australia. The stress dependent nature of velocity requires that the in situ pressure condition should be considered when the sonic log is used to determine the porosity of gas producing reservoir rocks.
Stress Concentration in Tubular Joints
Authors: Potvin A.B. , Kuang J.G. , Leick R.D. , Kahlich J.L. 
Published: December 2007

Abstract
Fatigue cracking caused by stress concentrations in tubular joints has been observed in some fixed platforms installed in hostile environments. platforms installed in hostile environments. Consequently, the ability to assess the magnitude of the stress concentration is a Prerequisite to dealing with the fatigue problem of tubular joints. This paper deals with the problem of computing the stress concentration in three types of simple, nonreinforced joints: T-joints, K-joints, and TK-joints. Semi-empirical equations are presented for estimating the stress concentration due to axial loads and bending moments.

Introduction
In off shore structures stress concentrations usually occur at the intersections of tubular members (i.e., tubular joints). For some joints, the stress concentration can produce a maximum stress at the intersection as high as 20 times the nominal stress acting in the members. Stress concentrations have aggravated the fatigue of tubular joints in many existing offshore structures. Therefore, an accurate computation of stress concentrations is of utmost importance in a tubular joint design.
The first part of this paper presents a discussion of the finite-element analysis method and the associated computer program developed exclusively for the analysis of tubular joints. The second part of this paper describes the parameter study carried out by means of the computer program. Formulas for estimating stress-concentration factors for simple joints commonly used in offshore structures are derived from the results of the parameter study. The usage of the resulting formulas is illustrated by a numerical example.

ANALYTICAL TECHNIQUE
In offshore structures such as fixed platforms and semisubmersible drilling vessels, tubular members comprise the main load-carrying components. Examples of cracking and even complete separation at the intersections of such members have been cited previously throughout the literature. A typical example of such an intersection is shown in Fig. 1. The member of greatest diameter will be referred to as the chord. The smaller diameter members framing into the chord will be called branches. The sections of the chord wall lying within the branch intersection line (if present) will be called plugs. Fig. 2 shows the various simple joint types referred to in this paper.
Because of the relative complexity of the geometrical configuration of tubular intersections as well as the thin-shell theory governing their behavior, reliable prediction of the stresses in such joints by analytical techniques has proven to be costly as well as difficult. Early attempts at analysis ranged from elementary strength-of-materials approaches such as the "punching shear" method to more complicated treatments that solve the governing equations by means of Fourier Series superposition.
SPEJ
P. 287
Mechanical Properties of Friable Sands From Conventional Log Data (includes associated papers 6426 and 6427 )
Authors: Stein N. 
Published: December 2007

A new log interpretation method is presented for determining mechanical properties of friable sands. Factors considered in the method include overburden weight, fluid pressure, and additional earth loads caused by local geological conditions. Log data needed for the interpretation include conventional sonic, density, induction, and open-hole gamma ray.

Introduction
Certain in-situ mechanical properties of friable sands must be measured to determine if such formations will remain stable under different wellbore conditions. Stability problems that can then be resolved include estimating (1) how fast oil or gas may be produced without casing a sand problem,1,2 (2) if there is sufficient cementation between adjoining sand grains to avoid a possible sand problem when water production occurs,1,3 and (3) the formation fracture pressure gradient.4 Specific mechanical properties that enable such estimates are sand strength, strength of cementation between grains, bulk compressibility, and Poisson's ratio. This paper presents techniques for calculating these properties.
The means for determining the in-situ mechanical properties of friable sands is through the use of well-log data. The accuracy of these properties determined from log data should be better than the properties determined from log data should be better than the properties determined by direct strength tests with core samples. Weakly cemented materials probably would disaggregate during the core recovery operation, and no strength of cementation would be detected in direct strength measurements. Relief of overburden load results in core expansion and subsequent breaking of weak bonds.
Logs used include conventional sonic, density, induction, and open-hole gamma ray. The conventional sonic log is used in preference to a full-wave sonic log for calculating the mechanical properties of friable sands. The full-wave log can provide both compression and shear-wave travel times if the formation grains do not slip by each other as the acoustic signals pass through. Many of the rock properties could then be calculated directly5,6 from such measurements. Grain slippage apparently occurs readily in many friable sands; the shear-wave signal is dampened severely, and it is difficult to record reliable data. Techniques are developed in this paper that make it possible to substitute conventional sonic-log data for full-wave log data for calculating the mechanical properties of friable sands.
Other methods have been reported1,4,7 for using log data to measure the mechanical properties incorporated all the following factors that can affect the mechanical properties:overburden weight gradients at different depths,other earth loads caused by local geological conditions,cementation,fluid saturation,fluid pressure,different bulk compressibilities, andthe change in elastic modulus values 1 of friable sands at different load conditions. These factors are considered in the calculation technique reported here.
Buckling Analysis in Deviated Wells: A Practical Method
Authors: Mitchell R. F. 
Published: December 2007

Summary
Current helical buckling models are valid for vertical wells, but provide only approximate solutions for horizontal wells. Solutions of the nonlinear buckling equations for arbitrary well deviation have been developed, but are too complex for practical use. This paper presents a set of correlations that match the exact solutions extremely well, but are simple to use. These correlations show the effects of well deviation on buckling shape, tubing length change, contact force and bending stress.
Silicate Based Muds: Chemical Optimization Based on Field Experience
Authors: Ward I. , Chapman J. W. , Williamson R. 
Published: December 2007

Summary
Since the reintroduction of silicate fluids into the North Sea in 1994 over 45 hole sections have been drilled using these fluids. The performance of the fluid during the early field trials is discussed together with the compositional changes made as the envelope of performance was extended. The current state of the art in sodium silicate and mixed silicate formulations is presented together with field data to illustrate drilling performance.
New Techniques for Oriented-Density Evaluation
Authors: Holm A.E. , Kleinegger J. 
Published: December 2007

By using a digital readout panel, a quantitative evaluation of the densities surrounding casing strings was made with a motorized oriented-density tool. Subsequent drilling-out alongside the casing confirmed the log evaluation.

Introduction
Since earlier tools could give only a qualitative evaluation of the densities surrounding the casing, a digital readout panel with some electronic modifications was used with the motorized oriented-density tool. This tool now can be used to quantitatively evaluate the wellbore and to orient perforations in dual or multiple casing-string wells.
A simulated-well calibrator was built to calibrate the oriented-density tool while looking through neat cement. Correlation of the calibrator with the actual well logs was excellent. The effective depth of investigation of this tool was also determined using the simulated-well calibrator.

Hypothesis
By plotting tool counts per second vs bulk density, this tool can detect other casing strings, neat cement, pozmix cement, mud, water, and gas with reliable results.

Well Conditions Used
Casing: 2 7/8-in., 6.4-lb, J-55, NU, 10 round tubing; two strings cemented nonconcentrically in an 8 3/4-in. wellbore using rubber turbilizers.
Completion cement: Class B neat cement mixed at 15.6 ppg; 1.96-gm/cc bulk density when set up; pumped as tail-in slurry.
Filler cement: 65/35 Class B pozmix cement with 12-percent get added; mixed with 15.56 gal of water per sack at 11.3 ppg; 1.48-gm/cc bulk density when set up; pumped as lead-in slurry. pumped as lead-in slurry. Motorized oriented-density tool: 1-11/16-in.-OD collar locator and motor sections above a 2 1/8-in.-OD window-type detector and radioactive source sections, which can be installed above a 2-in. cased gun for oriented perforating (Fig. 1).

Tool Calibration Simulated-Well Calibrator
To accurately determine the response to neat cement, a calibrator was built to simulate a single string of 2 7/8-in. casing cemented in a wellbore with neat cement. The calibrator is a 14 1/2-in.-ID, 36.71-lb, Grade B line pipe with a pup joint of 2 7/8-in., 6.4-lb, J-55 tubing capped on the bottom end and cemented adjacent to the inner wall of the line pipe. The 2 7/8-in. tubing was then filled with water (Fig. 2).

Calibrator Results
A 5-counts/sec statistical variation resulted. Logging was performed without tool rotation; then the detector performed without tool rotation; then the detector window was placed looking directly toward the neat cement (180 degrees) and was recorded on the chart. An average 115 counts/sec was recorded. with an over-all statistical variation of 5 counts/sec.
The effective depth of investigation was 4.5 in. Logging with tool rotation in the calibrator, a sweep of 154 degrees was observed in the neat cement before encountering the 14 1/2-in. line pipe (Fig. 3).
JPT
P. 1151
Convection in Fractured Reservoirs - The Effect of Matrix-Fissure Transfer on the Instability of a Density Inversion in a Vertical Fissure
Authors: Peaceman D.W. 
Published: December 2007

Abstract
In a fractured reservoir undergoing pressure depletion, evolution of gas at the top of the oil zone leads to an unstable density inversion in the fissures. The resulting convection brings heavy oil into contact with matrix blocks containing light oil, and results in the transfer of dissolved gas between matrix and fissure in the undersaturated region of the oil zone. To provide a better understanding of dis process, an earlier perturbation analysis of a density inversion in a vertical fissure has been extended to include the matrix-assure transfer.
It was found that matrix-fissure transfer does not affect the stability or instability of a density inversion, nor does it affect the spacing of density angers or the size of convection cells. A quantitative expression for the rate of growth of unstable density fingers was derived. The effect of matrix-fissure transfer is always to reduce the rate of growth. For practical reservoir cases, while any density inversion should be highly unstable, matrix-fissure transfer can be expected to cause a significant reduction in the linger growth rate.

Introduction
Most fractured reservoirs of commercial interest are characterized by the existence of a system of high-conductivity fissures together with a large number of matrix blocks containing most of the oil. It has been recognized for some time that the analysis of the behavior of a fractured reservoir must involve an understanding of the performance of single matrix blocks under the various environmental conditions that can exist in the fissures. However, only recently has it been recognized that a similar need exists for a better understanding of the convective mixing that probably takes place within the oil-filled portion of the fissure system.
In a fractured reservoir undergoing pressure depletion, gas will be evolved at all points of the reservoir where the oil pressure has declined below the original saturation pressure. This depth interval is referred to as the gassing zone. Because of the high conductivity of the fracture, the gas in the fissures will segregate rapidly from the oil before reaching the producing wells and most, if not all, of it will join the expanding gas cap.
At a sufficient depth, however, the oil pressure will still be higher than the saturation pressure, and the oil there remains in an undersaturated condition. (See Fig. 1.)
In the gassing zone, gas evolves from the oil in both the fissures and the matrix. The oil left behind in the fissures within the gassing zone contains less dissolved gas and is heavier than the oil below it in the undersaturated zone.
SPEJ
P. 269
Programming Reservoir Problems on the Electric Analyzer
Authors: Barrett Mary , Rose Walter 
Published: December 2007

Introduction
The conventional way to program reservoir problems for solution on the electric analyzer is one which concentrates the block units towards the inner radius of the prototype system being represented by the analog model.

Present Programming Method
While this conventional way of programming problems is quite adequate for routine uses of the electric analyzer, it leads to difficulties in those cases where the inner radius of the prototype system (e.g., the wellbore) is small compared to the external radius (e.g., the external reservoir boundary). To handle such a case by the conventional method would require either that a large value be selected for the constant a or that a large number n, of radial block units be chosen. In consequence, the capacitance and vertical resistance ratios become impossibly large, as will be evident from the relations, given above. In any event, the size of the smallest and largest capacitors will always be limited by the size of commercially available components, and the analyzer itself will determine how many mesh points are available for radial block units.
A Compositional Material Balance for Combination Drive Reservoirs with Gas and Water Injection
Authors: Lohrenz John , Clark George C. 
Published: December 2007

Abstract
Compositional material balance methods have been extended to solution gas-gas cap-water drive reservoirs. Partial or complete pressure maintenance as well as reservoir repressuring by gas and/or water injection may be considered. Increments of reservoir withdrawals and injections equivalent to a given time increment are used as the basic iterative step to allow the extension. An example field study shows how the reservoir volumes, extent of the water drive, and relative permeability ratio function may be estimated. Knowing these, the methods can be used to predict reservoir behavior.

Introduction
The compositional material balance is similar to conventional material balances in many aspects. The assumption of a pressure-homogenous reservoir with no transients is common to all conventional material balances although numerical methods are different. The compositional material balance also contains this assumption. Inclusion of phase equilibria directly in reservoir calculations is the key difference and improvement in the compositional material balance. A continuous account of the compositions of the reservoir fluids and effluents is determined. Calculations of fluid phases and properties can be based on these compositions. Excepting fluid phases and properties determined in this manner, the compositional material balance uses procedures exactly analogous to conventional methods. Brinkman and Weinaug and Jacoby and Berry have given compositional material balances for simple solution gas drive reservoirs; subsequently Jacoby and Berry, extended their procedure to include pressure maintenance by gas injection at constant reservoir pressure. This paper extends compositional material balance techniques to a more general combination drive reservoir with various types of pressure maintenance operations. The procedure for this extended compositional material balance and an example of its field application are presented.