bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue Reliability Analyses of Fixed Offshore Structures
Authors: Wouts M. A. , van der Graaf J. G. , Vrouwenvelder A. W. C. M. 
Published: December 2007

Abstract
The results of fatigue analyses of fixed offshore structures are very sensitive to the description of the applied loading and the strength of the structure. Conservative values are commonly incorporated in the analyses on the account of uncertainties in regard to pertinent parameters. Hence, a structure can be designed with an acceptable classical factor of safety having, however an unknown probability of fatigue failure. This paper describes a fatigue damage calculation method which accounts explicitly for the uncertainties of the input parameters and thus provides a measure of the probability of fatigue failure. Results of case studies are presented to demonstrate the rationale of the method.
Horizontal Drilling and Completion: Denmark
Authors: Andersen S. A. , Hansen S. A. , Fjeldgaard K. 
Published: December 2007

ABSTRACT
The application of horizontal drilling technique to improve production performance from selected tight chalk reservoirs in the Danish sector of the North Sea has shown to be technically feasible and economically viable.
Maersk Oil and Gas has drilled and completed three horizontal wells with horizontal drainhole sections ranging from 1000 feet to 3000 feet and with displacement of some 9000 feet from the wellhead platform slot.
The essential early planning aspects leading to evaluation and solution of preferred options are discussed. Modifications to the approach adopted as experience is gained and a generalised overview of problems, solutions and costs is included.
Prediction of Laminar and Turbulent Friction Pressures of Cement Slurries in Pipes and Centered Annuli
Authors: Guillot D. J. , Denis J. H. 
Published: December 2007

Abstract
Friction pressures of different cement slurry formulations with properly characterized rheologyhave been measured in a wide variety of flow situations, including laminar (20 to 1000 s-1) and turbulent (2000 &lt;Re&lt; 10000) flow regimes. Tests were performed in pipe and concentric an- nular geometries, using a pilot-scale rig.
In laminar flow, it was established in a previous publication that pipe flow friction losses of cement slurries can be reliably predicted from rotational viscometer measurements made inthe shear rate range of the actual pipe flow. In this paper it is shown that valuable predictionscan also be obtained for concentric annuli, at least when the radius ratio (inner/outer) is greater than 0.3, if the geometry is approximated by a rectangular slot.
Pipe flow experimental data obtained in the turbulent flow regime are compared to several existing models. A modified Dodge and Metzner approach to the problem was found to give the best agreement with the measurements. For concentric annuli, a similar procedure is shown to be acceptable when used with the rectangular slot approximation. Reasonable agreement is found between model predictions and experimental results.
For both flow regimes, the proposed method is no more complicated and is proved, for most field situations, to be much more accurate than the API procedure in predicting pressure drops.
Efficient Use of Locally Refined Grids for Multiphase Reservoir Simulation
Authors: Ewing R. E. , Boyett B. A. , Babu D. K. , Heinemann R. F. 
Published: December 2007

Abstract
Three-dimensional, multiphase flow problems are solved on static, composite grids. The composite grid consists of a global, rectangular coarse grid and a set of locally refined patches around active wells or other areas with important local flow properties. Curvilinear (locally orthogonal) refinements can be utilized to approximate radial or near-radial flow around wells if such flow is assumed to be appropriate. More general localized refinement can be utilized otherwise. Finite differencing is presented which connects the local and global grid cells in an accurate manner.
Other methods for composite grid applications which have appeared in the SPE literature generate linearizations which have lost their banded structure and must utilize corresponding solution algorithms that are extremely difficult to vectorize for efficient solution. Preconditioned iterative techniques will be discussed which allow easy implementation of the composite grid techniques in existing simulators with full vectorization capabilities.
Pressure calculations in a single-phase flow problem with a distribution of injection and production wells exhibit excellent agreement between numerical calculations on locally radial grids and analytical solutions. Water and gas coning results for a single well also show very good agreement between computations on a hybrid grid and a circular cylindrical grid. This indicates the potential for incorporating coning models around any well in a full field-scale application without destroying the efficiency of the original simulator.
Stability Analysis and Switching Criteria for Adaptive Implicit Methods Based on the CFL Condition
Authors: Russell T. F. 
Published: December 2007

ABSTRACT
Adaptive implicit methods seek an efficient middle ground between IMPES and fully implicit time stepping. The principal issue in implementation of these methods is the switching criterion that determines whether a given unknown is implicit or explicit. We develop and justify a criterion based on the Courant-Friedrichs-Lewy (CFL) stability condition. This could also be used for time-step control in IMPES models by indicating the maximum stable time step.
First, we analyze simple problems theoretically and find that adaptive implicit stability, like fully explicit stability, depends on a CFL condition. Next, we develop a switching criterion for a black-oil model and indicate how it could be extended to compositional simulation. The CFL-based criterion involves quantities that an implicit Jacobian must already compute, so its use costs virtually nothing. Each unknown has its own CFL number at every outer Newton iteration, so any combination of implicit and explicit unknowns is possible and a given unknown may switch back and forth through time.
While discussing the simple problems, we analyze and compare three adaptive implicit methods that have been suggested in the literature. One of the methods yields better answers by reducing numerical dispersion. Also, its CFL restriction for practical calculations is looser than those of the other methods, allowing it to make more unknowns explicit.
The Formulation of a Thermal Simulation Model in a Vectorized, General Purpose Reservoir Simulator
Authors: Chien M. C. H. , Yardumian H. E. , Chung E. Y. , Todd W. W. 
Published: December 2007

ABSTRACT
This paper describes the formulation of a thermal simulation model in a vectorized, general purpose reservoir simulator. The thermal simulation model, an option in this general purpose simulator, is equivalent to a three-phase, three-dimensional, thermal compositional simulator. It has a variety of options for modeling fluid properties and phase behavior. These include the EOS method (the three parameter Peng-Robinson equation of state) and the non-EOS methods (table look-ups and correlations). The model also considers the solubility of water in the oil phase. Furthermore, all calculations are extensively vectorized.
Test problems including problem No. 3 of the Fourth SPE Comparative Solution Project are used to evaluate the effectiveness of vectorization. Results show that the vectorized calculations outperform the nonvectorized ones by about an order of magnitude in computational speed on the Cray X-MP/48. Overall, this thermal model runs about 5 times faster than a previously reported conventional, partially vectorized thermal simulator.
Finally, the use of this thermal simulation option to study the sensitivity of simulation results to various fluid property and phase behavior calculation methods is illustrated with a hypothetical problem. Results show that simulation results can be used to determine the importance of different K-value and volume calculation methods, and the inclusion of water-in-oil solubility.
A Comprehensive Wellbore/Reservoir Simulator
Authors: Stone T. W. , Edmunds N. R. , Kristoff B. J. 
Published: December 2007

ABSTRACT
This paper describes a fully implicit, three dimensional thermal numerical model for simulating flow through a porous media and through a wellbore. Darcy's law is used together with conservation of energy and mass to model flow in the porous media. The wellbore simulator is a time dependent, thermal, three-phase, one dimensional model which conserves energy, momentum of all phases and mass. Wellbore grid blocks are embedded in reservoir grid blocks. Variables in the reservoir and wellbore are solved for simultaneously. Many options are included in the wellbore simulator including the ability to model parallel flow in inner tubing and outer annuli and specification of slant angles or other parameters per wellbore grid block. This coupled model is targeted mainly at horizontal well or other applications in which a high degree of dynamic interaction occurs between the wellbore and reservoir.
Compositional Modeling of High-Temperature Gas-Condensate Reservoirs With Water Vaporization
Authors: Betté S. , Heinemann R. F. 
Published: December 2007

SUMMARY
An equation of state compositional model capable of simulating water vaporization is presented. This approach treats water as a component among other species in the hydrocarbon phases and allows for mass transfer between the aqueous phase and the hydrocarbon phases. The model is validated against single cell PVT experiments. The impact of this formulation on the basic compositional model equations and the solution of the nonlinear and linear system of equations will be discussed. The simulator incorporates a sophisticated well management scheme with a model of a gas plant to evaluate performance under various facility constraints.
The application of this simulator in the management of the Arun gas-condensate reservoir in Indonesia is presented. The first phase of this 5000 cell, 8 component, 50 well study involves establishing reservoir parameters by matching historical pressure performance of individual wells. Predicted total field wellstream composition and cluster condensate gas ratios match historical data very well. The accuracy with which this formulation simulates water vaporization is demonstrated by comparing predicted and measured water vapor production. In the second phase, the reservoir model is used to predict future performance. This simulator has the unique capability of simulating gas processing plant operation to calculate and predict product streams such as LNG, LPG and stabilized condensate. This feature allows one to specify future demand for a product such as LNG. The specification is translated into exact individual well production rates based on their produced well stream composition. Water evaporation has a significant effect on reservoir performance and an even greater effect on tubing flow performance. The model predicts injection gas profiles, extent of retrograde condensation, subsequent revaporization by injection gas, and composition and saturation distributions across the reservoir. The utility of the model predictions in the design of surface facilities, in the determination of well requirements, and in developing strategies to improve product recoveries will be discussed.
Use of Parameter Gradients for Reservoir History Matching
Authors: Anterion F. , Eymard R. , Karcher B. 
Published: December 2007

ABSTRACT
In reservoir simulation, history matching has long been performed in an empirical way. Applying inverse problem methods to reservoir simulation requires the calculation of gradients of observations at producing wells with respect to reservoir characteristics, which leads to a local linearisation of the full non linear reservoir simulation problem.
This paper describes a rigorous analytical method for the computation of gradients. The gradient calculation has been implemented in the fully implicit, 3-phase, 3-dimensional reservoir simulator, SCORE, in a way which leads to significantly reduced computation time compared to other methods.
The second part of the paper reports on a preliminary attempt at computer aided history matching, based upon a meta simulator which uses the calculated values of the gradients and a minimisation procedure together with several extrapolation laws. Two applications of the method are presented. They serve to demonstrate that the experience of the reservoir engineer cannot be replaced by such a method, used in an automatic way, because the system cannot decide which parameters should be changed. However, once an appropriate choice had been made, the meta-simulator provided an accurate estimate of the modified parameters which had to be used in order to simulate precisely the observed results.
Application of this method increased the accuracy of the history match whilst significantly reducing both the number of computer runs and the total processing time required compared to other methods.
Acid Reactions and Damage Removal in Sandstones: A Model for Selecting the Acid Formulation
Authors: Perthuis H. , Touboul E. , Piot B. 
Published: December 2007

ABSTRACT
For removing a clay-based damage in sandstone formations, diluted HCl-HF acids are often recommended when the standard 12%HCl-3%HF acid is found or thought to be incompatible with the formation through one of the possible mechanisms: deconsolidation, fines migration or by-product precipitation. But the dissolving power of such acids, which varies with rock mineralogy, is generally not assessed.
Dissolution kinetics parameters for aluminosilicate minerals with these acids, as well as with other acids which are able to progressively generate HF, have been verified and established as a function of temperature, mineral concentration and mineral surface area, acid concentration and ionic strength (catalytic effect).
These complete acid-rock reaction parameters have been implemented into a dissolution simulator coupling chemical reactions and flow in a porous medium. This implementation has been validated against flow tests in linear geometry. The dissolution power of commercial acid formulations can thus be compared during simulations of real treatments and the best system for effective damage removal be selected. Examples show how treatment parameters (permeability, porosity, clay and silica content in the damaged area) are affected to varying degrees by these different acid solutions.
A New Nondamaging Particulate Fluid-Loss Additive
Authors: Williamson C. D. , Allenson S. J. 
Published: December 2007

ABSTRACT
Recently there has been a push to pursue a cleaner fracturing system. This includes using a fluid loss additive that is nondamaging. Conventional particulate fluid loss additives are usually made up of inert materials such as silica flour or clay. These types of materials are well known for their ability to plug pore spaces and enhance the formation of a filter cake. Once flow back is started, however, these materials can stay in place possibly causing reduced permeability. Since the materials are inert, they can remain in the pore space for a long period of time. To circumvent these problems, a non-formation damaging particulate fluid loss additive is needed.
This paper describes the development of a new non-formation damaging particulate fluid loss additive that is degradable under downhole conditions. This fluid loss additive is a blend of various starches and substituted starches with a broad particle size distribution ranging from 5 to 200 microns and with a portion of the starches being water soluble.
A synergistic effect occurs between the starches and modified starches that comprise the subject fluid loss additive. This is evident from results seen in standard API fluid loss tests. The blend provides significantly lower spurt losses and Cw values than any of the individual components.
Additional laboratory studies on the non-damaging aspect of this fluid loss additive have shown excellent degradation results with respect to time, temperature, and addition of an enzyme or persulfate.
Inorganic Chemical Souring of Oil Reservoirs
Authors: Marsland S. D. , Dawe R. A. , Kelsall G. H. 
Published: December 2007

Abstract
Many North Sea oil production reservoirs are producing increasing quantities of hydrogen sulphide, perhaps as high as 30 ppm, although the oil itself is naturally sweet. This high level is endangering the sales of oil and gas, giving rise to enhanced corrosion effects in pipelines and production facilities as well as causing concern for health and safety.
The mechanism put forward in this paper for hydrogen sulphide generation within the reservoir is via Non-oxidative dissolution of formation components:
MS + 2 H + ↔ M 2 + + H 2 S
(where MS. is especially components containing iron sulphide species such as Fe1 − xS, FeS1 − x and FeS2)
The acidic component in the above reactions is provided either from the injection water on breakthrough, or degradation species from injected components such as biocides and corrosion and scale inhibitors.
The objectives of this continuing study are to investigate the kinetics and mechanisms of formation dissolution in reservoir environments of high temperature, high pressure and high ionic concentration based on:
Preparing pure iron sulphides of known stoichiometry and homogeneity Using generated thermodynamics diagrams to predict the behaviour of the iron-sulphur-water system at any required conditions relevant to the reservoirs Combining the thermodynamic predictions of 2) with experimental work utilising 1) in a rotating-ring-disc electrode assembly to determine the mechanism and kinetics of the dissolution reactions
This paper presents the preliminary work on this study.
Hydrolytic Stability of Ethoxylated Sulfonates
Authors: Talley L. D. 
Published: December 2007

ABSTRACT
This paper discusses the reactions that are responsible for the decomposition of alkyl ethoxylated sulfonates under reservoir conditions. Experimental results are presented to substantiate the derivation of several kinetics equations. The equations form the basis for a mathematical model capable of predicting the lifetime of an ethoxylated sulfonate at’ all reservoir temperatures, salinities and brine pH.
What Is the Rheology of Foam in Porous Media? A Micromodel Study
Authors: Armitage P. , Dawe R. A. 
Published: December 2007

ABSTRACT
Snap-off, a bubble/lamella generating process is believed to be responsible for the generation of strong foams in porous media. It is thought to be dependent upon a number of system parameters such as the pore geometry, surfactant concentration, wetting fluid viscosity, flow rate and the quality (gas to liquid flow rate ratio). A study has been conducted to assess the degree of influence these parameters have on the process of snap-off.
This paper reports in detail a number of qualitative and quantitative results obtained from a 2-D mechanistic study of the flow of an interface (constituent part of a foam) through various simple rectangular pore-throat pore-body junctions. The study was conducted using 2-D micromodels made from a clear, araldite epoxy resin so that visual evidence of the results could be recorded.
Roof's theoretical analysis of the static geometric criterion required for snap-off to occur has been modified to accommodate our physical models and its predictive capabilities explored in a dynamic situation. Also the pressure regimes manifest in the process of snap-off have been recorded as a function of time in an attempt to quantify the events more fully.
The findings reported here give further insight into one of the major pore-scale foam generating mechanisms.
Discount Rates, Cost of Capital, and Property Acquisition Evaluations
Authors: Miller R. J. , Vasquez R. 
Published: December 2007

Abstract
The purpose of this paper is to examine the role of the discount rate in determining the fair market value of a producing oil and gas property; to assess the validity of a discount rate based on a derived source and on an observed or market source, and to evaluate the relationship between discount rates obtained from these two sources. The derivation of a discount rate based on a Cost of Capital approach is compared to the observed effective rate-of-return obtained from analysis of actual producing property acquisitions to (1) determine if a rational relationship occurs between discount rates obtained from the two methods, and (2) how the discount rates obtained from the two methods may reflect changes in the oil and gas industry. The use of derived and observed discount rates in FMV analysis is examined and discussed, particularly as it applies to property acquisitions.
The source of the study reported by this paper is an annual review and analysis of oil and gas property transactions in California which is done for the Western Oil and Gas Association (WOGA) and the California Independent Producers Association (CIPA) and which is generally referred to as the "WOGA Study."(1) The WOGA study attempts to define market economic parameters used in the acquisition of producing properties in California. The study examines several economic factors, including price/cost projections, but particular attention is given to the effective discount rate related to the determination of Fair Market Value. This market data forms the basis for industry recommendations to the county tax assessors regarding the methods and parameters to be used in appraising oil and gas properties for ad valorem taxes. The objective of industry and assessors is to define a method, and the economic parameters necessary, to determine the present value and, more to the point, the Fair Market Value (FMV) of an oil and gas producing property. The same concern for proper evaluation methods and appropriate economic functions is thought to exist throughout the industry where operators, interest owners, financiers, and investors need to determine the market values of producing properties.
The study concludes that:
The pre-tax cost of capital of a company or industry group provides a reasonable "base" discount rate for evaluation of producing properties. The effective FMV ROR on actual acquisitions consistently exceeds pre-tax cost of capital by several percentage points. The divergence between observed ROR and cost of capital appears to vary depending, at least in part, on the perceived risk in the property appraisal. Risk adjustments on a project or other basis, if identifiable, are not quantifiable from the data available. The Cost of Capital for the oil and gas industry, from a sample group, averaged 19–20% for 1983–1985 declining to 14.9% in 1987. The market discount rate from actual sales of properties for the 1983–1987 period, ranged between 26–28% which provided a reasonable and safe return above the cost of capital.