bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reliability Management of Surface-Controlled Subsurface Safety Valves for the TOGI Project
Authors: Moines Einar , Iversen Morten 
Published: December 2007

Summary
This paper describes Norsk Hydro and SINTEF's efforts to obtain higher reliability of surface-controlled subsurface safety valves (SCSSV's) for the Troll-Oseberg gas-injection (TOGI) project. Because of the severe consequence of system failures, reliability management was fully implemented on the TOGI subsea production system. The methodology used combines reliability theory with operating experience. Data bases with relevant field data, design review techniques, valve prototype testing, and review of test results are other elements of the reliability management program. Although this specific application was for SCSSV's, the methodology presented in this paper can easily be applied to systems where the consequence of failure is severe.
Nonlinear Simulation of Jackup Platform Models
Authors: Liu Ping , Massie W. W. , Wolters J. G. , Blaauwendraad Johan 
Published: December 2007

Summary
This paper summarizes laboratory studies and associated computer simulations for three jackup models. Comparison of computed results with measured data shows that such simulations are reliable. Further results demonstrate that hydrodynamic interaction must include relative velocities, the P-δ effect is essential, and damping and stiffness at the deck/leg connection can be "traded off. " Parameter studies, such as the influences of linearization, free-surface treatment, different wave theories, and hydrodynamic force cancellation, also are presented.
Pore-Pressure Influence in the Poroelastic Behavior of Rocks: Experimental Studies and Results
Authors: Laurent Jérôme , Boutéca Maurice J. , Sarda Jean-Paul , Bary Daniel 
Published: December 2007

Summary
The influence of pore pressure on the elastic strain of rocks is basic to reservoir compaction and subsidence problems and in reservoir engineering and environment studies. Biot's coefficient is an important parameter used to determine the influence of pore pressure on rock deformation. This paper presents measurements of Biot's coefficient on limestone samples and interprets these measurements. The coefficients used in poroelastic studies first are defined as Biot's coefficient and compressibility coefficients proposed by Zimmerman. Then, the experimental apparatus and procedures used to measure these coefficients are described. Finally, the results, which confirm the theoretical framework of poroelasticity, are presented and discussed. The compressibility coefficients and Biot's coefficient increase with porosity according to a law that is formally similar to a Hashin-Shtrickman's type law. For porosities in the 4.5% to 23% range, Biot's coefficient increases from 0.34 to 0.83
Acoustic-Emission Monitoring During Hydraulic Fracturing
Authors: Stewart Lisa , Cassell B. R. , Bol G. M. 
Published: December 2007

Summary
Microseismic events or acoustic emissions associated with hydraulic fracturing are recorded with a borehole seismic tool in a deviated well during multirate injection, shut-in, and flowback. The event locations indicate that fracture orientation, length, and height are compatible with regional stress directions and estimates of the fracture size that are based on pressure decline.
The Performance of Hydraulically Fractured Stimulated Wells in Tight Gas Sands: A Southern North Sea Example
Authors: Ovens Jonathan E. V. 
Published: December 2007

SummaryThe development of the tight gas sands in the northwest flank of Shell/EssQ's Leman field required massive hydraulic fracture (MHF) stimulation. Well tests were commissioned to help understand the link between fracture design and performance. A statistical analysis of the test results gave credence to the hypotheses that hydraulic fractures connected these wells to a large natural fracture system, that the hydraulic fractures were semiradial in shape, and that a minimal productivity loss arose from the limited communication between wellbore and fracture. These results have assisted in further stimulation design.
An EOS for High-Pressure Aqueous Electrolyte Systems—Predicting the Solubility of Natural Gas in Formation Water
Authors: Zuo You-Xiang , Guo Tian-Min 
Published: December 2007

Summary
A new Helmholtz energy equation is developed for high-pressure aqueous electrolyte systems, and a corresponding equation of state (EOS) is derived. The model parameters are determined from ionic activity coefficient and vapor/liquid equilibrium data of binary and ternary mixtures. The new EOS predictions of the solubilities of pure gas and natural gas mixtures in brines show satisfactory agreement with measured experimental data.
Effect of Firing on Petrophysical Properties of Berea Sandstone
Authors: Ma Shouxiang , Morrow Norman R. 
Published: December 2007

SummaryBerea sandstone is widely used as a model rock for studying fluid flow through porous media. Firing has been a common step in core preparation. Changes in properties of Berea sandstone caused by firing were determined from petrophysical measurements and petto-graphic studies. Results show that firing usually creates more problems than it solves. Use of fired cores generally should be avoided.
Flow Modeling of Alkaline Dissolution By a Thermodynamic or By a Kinetic Approach
Authors: Labrid Jean , Bazin Brigitte 
Published: December 2007

Summary
This paper presents a calculation of the propagation of basic pH in a reservoir rock based on either a kinetically controlled reaction or a thermodynamic equilibrium assumption. Results demonstrate that the kinetic approach is the only way to analyze the interactions of alkaline chemicals with clayey sandstones properly.
Modeling Fluid Flow Through Complex Reservoir Beds
Authors: Durlofsky Louis J. 
Published: December 2007

Summary
Complex beds can significantly affect the flow of fluids in reservoirs. However, current simulators generally are not well-suited to model such flows, in part because they typically do not model permeability as a tensor quantity. This paper demonstrates the importance of treating permeability as a full tensor quantity in simulating flow through complex beds by considering two related problems. First, fluid flow through cross-stratified beds is studied. In this case, heterogeneities appear on the fine scale, and a scale-up procedure is required to model explicitly the effects of these beds. A general numerical procedure, which properly preserves the tensor nature of the effective permeability of such strata, is presented for this computation. The method is based on a finite-element solution of the fine-scale pressure equation with periodic boundary conditions imposed. Second, the modeling of flow through anisotropic, inclined reservoir beds is studied. It is shown that the commonly used techniques for modeling flow through such features, stratigraphic and horizontal layering, implicitly assume principal directions (or orientations) for the permeability tensor. With simple model problems, the differences between simulation results for different orientations of the permeability tensor and differences between results from horizontal and stratigraphic layering are quantified. These differences, which are substantial in the case of high reservoir dip and high anisotropy, emphasize the importance of a knowledge of the full permeability tensor in predicting flow through complex reservoir features.
A New Approach to Flow Simulation in Highly Heterogeneous Porous Media
Authors: Ramé Marcelo , Killough J. E. 
Published: December 2007

Summary
Applications are presented for a new numerical method—operator splitting on multiple grids (OSMG)—devised for simulations in heterogeneous porous media. A coarse-grid, finite-element pressure solver is interfaced with a fine-grid timestepping scheme. The CPU time for the pressure solver is greatly reduced and concentration fronts have minimal numerical dispersion.
Water-Alternating-Steam Process Improves Project Economics at West Coalinga Field
Authors: Hong K. C. , Stevens C. E. 
Published: December 2007

Summary
The water-alternating-steam process (WASP) was applied to vertical expansion (VE) sands in the pilot area of Section 13D, West Coalinga field to stop wasteful steam production and to improve vertical conformance of injected steam. Before the WASP application, steam breakthrough in the VE sands caused well sanding, cutting of downhole tubulars, and high-temperature-fluid handling problems. To alleviate these problems, pumps had to be raised in five wells and one well had to be shut in, reducing oil production from the VE sands and the lower waterflooded zones. A WASP field test, based on a numerical simulation study, was implemented in July 1988 with alternating slugs of water and steam, each injected over 4 months. The WASP eliminated steam production, allowing the pumps to be lowered and the one shut-in well to return to production. Oil production remained constant through the first WASP cycle and increased during the second cycle. Sales oil (total production minus oil used to generate steam) increased as a result of saving generator fuel during the water leg of each WASP cycle, resulting in improved project economics.
Formation Evaluation of Exploration Coalbed-Methane Wells
Authors: Mavor M. J. , Close J. C. , McBane R. A. 
Published: December 2007

SummaryDevelopment of coalbed-methane reservoirs requires accurate determination of gas in place and natural fracture permeability. This paper outlines steps needed to evaluate reservoir properties and to predict well deliverability. Procedures are documented with data and analyses from San Juan basin development projects. The paper includes an example of the accuracy of gas-content determinations from pressure-, sidewall-, and conventional-core and drill-cuttings samples; presents specifications for complete log suites and analysis techniques for gas-content estimates; discusses drillstem-test (DST) procedures; and outlines prediction of well deliverability.
Partitioning Tracers and ln-Situ Fluid-Saturation Measurements
Authors: Tang Joseph S. 
Published: December 2007

Summary
This paper reviews applications of partitioning tracers in the petroleum industry. Partitioning between phases slows the partitioning tracers in a phenomenon known as chromatographic retardation, from which fluid saturations and surface properties can be deduced. Single-well tracer testing (SWTT) to determine residual oil saturation to waterflood, Sorw, is the most common application of partitioning tracers. More than 200 tests have been run since its invention in 1971. In addition to development of new simulators, a mass-balance method and an internally calibrated method were proposed for direct calculation of Sorw from the tracer reaction rates. With the introduction of the chromatographic transformation technique, several successful interwell tests to determine residual oil saturations in watered-out and gas-saturated reservoirs have been reported. The technique involves direct comparison of the partitioning and nonpartitioning tracer profiles with no need for simulation. In a different approach, full-field simulation of a multiwell test has also been used to estimate oil saturation distribution. Other interesting applications include in-situ miscibility measurement, determining trapped gas saturation during a foam flood, relative permeability ratio measurement, and direct logging of gamma-emitting partitioning tracers through casing to determine residual oil saturation, Sor, vertical distribution.
Pressure Behavior of Horizontal Wells in Multilayer Reservoirs With Crossflow
Authors: Kuchuk F. J. , Habashy Tarek 
Published: December 2007

Summary
New analytic solutions for horizontal wells with wellbore storage and skin in layered reservoirs with crossflow are presented. These layered systems can be bounded by two horizontal impermeable boundary planes at the top and the bottom, or either one of the boundary planes can have a constant pressure (the system either has a gas cap or an active aquifer), while the other is maintained as a no-flow boundary. The new solutions are derived by utilizing the reflection and transmission concept of electromagnetics to solve fluid flow problems in three dimensional layered reservoirs, where non-homogeneity is in only one direction. The solution technique is sufficiently general that it may be applied to a wide variety of fluid flow and well testing problems involving single-phase flow. The solutions are applied to a number of layered-reservoir examples. It is shown that a gas cap or aquifer should automatically not be treated as a constant-pressure boundary. It is also shown that estimation of layer parameters from conventional well tests is difficult. A field example is presented for the use of the new solutions for the interpretation of a buildup test from a horizontal well in a multilayer reservoir, where the layers are separated sporadically by low permeability zones. The Horner method is also used to interpret the field test; however, Horner does not work well for layered systems with horizontal wells.
Reservoir Monitoring in Low-Salinity Environments With Pulsed-Neutron-Capture and Gamma Ray Logs
Authors: Mills Andrew A. 
Published: December 2007

Summary
Accurate quantitative interpretation of pulsed-neutron-capture (PNC) logs cannot be achieved in the low-salinity formation-water environment of the Gippsland basin because formation fluid responses are small relative to uncertainties introduced by lithologic variation. Time-lapse interpretation is used effectively although formation responses often are masked by larger responses caused by changes in the logging environment. Several easy techniques, such as using the gamma ray log to indicate formation-water movement, are used to aid interpretation.
Evaluation of Pulse Tests With Noise Suppressing
Authors: Tóth Béla , Megyery Mihály 
Published: December 2007

Summary
Pulse testing is an effective way of understanding fluid reservoirs. Several noise components bias high-sensitivity pressure measurements so that a considerable part of the tests cannot be interpreted conventionally, thus impeding pulse testing's wide-range application. To improve noise filtering, we developed a computerized method of evaluation and noise suppression, which can enhance interpretability effectively. Only 17% of 617 tests performed in Hungary can be interpreted in the usual way, whereas 78% can be interpreted by the method reviewed in this paper.
After an enumeration of the pressure changes (noises) disturbing pulse tests, we illustrate our cycle-sum-up method of noise suppressing and the related interpretation procedure. We also report on results of the reproducibility investigations, and we give a brief outline of the basic principles of interpreting reservoirs with multiple faults.
Determining Circulating Fluid Temperature in Drilling, Workover, and Well Control Operations
Authors: Kabir C. S. , Hasan A. R. , Kouba G. E. , Ameen M. M. 
Published: December 2007

Summary
Estimation of fluid temperature in both flow conduits (drillpipe or tubing and the annulus) is required to ascertain the fluid density and viscosity and, in turn, to calculate the pressure drop or the maximum allowable pumping rate for a number of operations. These operations include drilling, workover, and well control. The fluid temperature estimation becomes critical for high-temperature or geothermal reservoirs where significant heat exchange occurs or when fluid properties are temperature sensitive, such as for a non-Newtonian fluid.
In this work, we present an analytical model for the flowing fluid temperature in the drillpipe/tubing and in the annulus as a function of well depth and circulation time. The model is based on an energy balance between the formation and the fluid in the drillpipe/tubing and annulus. Steady-state heat transfer is assumed in the wellbore while transient heat transfer takes place in the formation. Solutions are obtained for two possible scenarios: (1) the fluid flows down the annulus and up the drillpipe/tubing, and (2) the fluid flows down the tubing and up the annulus. The analytic model developed is cast in a set of simple algebraic equations for rapid implementation. We also show that the maximum temperature occurs not at the well bottom, but at some distance higher from the bottom for flow up the annulus.
The solution approach is flexible enough to use the formation temperature distribution function, TD, developed by various authors. A limited sensitivity study shows that all the TD models give comparable solutions, with the exception of line-source solution at early times.
Effect of Water Dissolution on Oil Viscosity
Authors: Glandt C. A. , Chapman W. G. 
Published: December 2007

Summary
Water dissolution in crude oil becomes significant at temperatures &gt; 150°C, and at 250°C, water solubilities in heavy crudes are ≈ 40 mol%. Dissolved water acts as a low-viscosity solvent that reduces oil-phase viscosity. This phenomenon has been considered in thermal recovery simulations but has never been substantiated. In this work, the effect of water on viscosity was measured for four crude samples with gravities ranging from 0.97 to 1.03 g/cm3. At the highest experimental temperature of 286 °C, viscosities of water-saturated samples were about one-half those of water-free counterparts. The viscosity reduction, although quite significant, was not as pronounced as the drop estimated by viscosity mixing rules used for hydrocarbon systems. While a log mixing rule or a one-quarter power mixing rule overestimated viscosity effects, a mole-fraction-weighted average of oil and water viscosities matched the experimental data. A possible explanation for failure of the log mixing rule is that the water dissolved in the oil exists not as monomers but as hydrogen-bonded clusters. We find good agreement with experiment when the mole fraction of water clusters, calculated from a statistical mechanics based theory, is used in the log mixing rule.
Random Genetic Simulation of the Internal Geometry of Deltaic Sand Bodies
Authors: Hu L. Y. , Joseph Philippe , Dubrule Olivier 
Published: December 2007

SummaryA new stochastic approach for modeling the internal geometry of deltaic sand bodies is presented that incorporates both genetic (or process-based) and geometric aspects. The genetic aspect takes geologic concepts into account, whereas the geometric aspect reduces the number of parameters for use in applications. Sand-body models resulting from this method honor the well data. This approach is applied to model the internal architecture of an Eocene deltaic sand-body outcropping near Roda, Spain. The simulations using a few wells are compared with the geologic reference model obtained using all the outcrop and log data. The sensitivity of the simulation results is also checked with respect to the fluctuation of the input parameters.
Supercritical Production From Horizontal Wells in Oil-Rim Reservoirs
Authors: Tiefenthal S. A. 
Published: December 2007

Summary
A model for the prediction of supercritical production rates from horizontal wells in oil rims is presented. The model is based on an extension of the 2D gravity-drainage model for critical rates in two-phase scenarios. The extended model can be used for two- (gas/oil or water/oil) or three-phase (gas/oil/water) situations with unfavorable mobility ratios. A field example from the Troll West oil rim illustrates the applicability of the model.
Geometry of Hydraulic Fractures Induced From Horizontal Wellbores
Authors: Weijers L. , de Pater C. J. , Owens K. A. , Kogsbøll H. H. 
Published: December 2007

Summary
In the Dan field, very high breakdown pressures were observed for wellbores drilled with a high azimuth with respect to the preferred fracture plane. The increased breakdown pressure was caused by significant near-wellbore friction. In scaled laboratory tests, variation in breakdown pressure was accompanied by a change in fracture geometry. Therefore, the variation in breakdown pressure in the field treatments could not be related simply to in-situ stresses.
A Model for Calculation of Formation Force and Its Application
Authors: Yan Tie , Zhang Jianqun , Hareland Geir , Rajtar J. M. 
Published: December 2007

Summary
The paper presents a model of a rock-bit interaction. The model allows us to calculate formation forces that develop from rock-bit interactions and weight on bit (WOB). The model accounts for the effects of drilling trajectory changes and formation anisotropy and it may eliminate the shortcomings of other models that do not specifically consider these effects. The paper discusses in detail the features and factors that affect formation forces. The model was applied to modify drilling technology in the south region of Daqing, China. Drilling data were collected and the formation forces were calculated. The results showed that the average formation force to WOB ratio was about 0.74%. The results also indicated what strata are primarily responsible for uncontrolled changes of drilling trajectory. This analysis allowed us to improve the drilling technology in the region.
Successful Use of a Modified MWD Tool in a High-Concentration LCM Mud System
Authors: Attong D. J. , Singh U. B. , Teixeira Gary 
Published: December 2007

Abstract
This paper presents the successful field testing of a modified measurements while drilling (MWD) tool to handle high concentrations of lost circulation material (LCM) in the mud system. This specially formulated high concentration LCM mud system is commonly used to enable drilling through severely depleted and unconsolidated sandstone reservoirs without lost circulation. In this application the MWD tool is used to provide real time directional surveys, formation evaluation and drilling efficiency data.
The original design of the MWD tool limited its use with this LCM mud system because of the tool's high susceptibility to plugging. Research and development by the MWD company in cooperation with the Operator led to modifications of the MWD tool which now enables it to handle very high LCM concentrations without plugging, resulting in considerable cost savings to the Operator. The MWD company has also benefitted by extending their tool's application to a harsh LCM environment.
Practical Advantages Of Mud Cooling Systems For Drilling
Authors: Guenot Alain , Maury Vincent 
Published: December 2007

Abstract
Field case studies of borehole stability have shown that some failures, previously unexplained, were due to thermal effects, such as heating the upper part of open hole sections by mud circulation when drilling deeper or reheating of the bottomhole when mud circulation is stopped.
A complete analysis of the thermal regime in boreholes was performed and as a consequence, cooling of mud appeared as a means to mitigate these effects.
A series of tests were then carried out to check the practicality of installing such mud cooling systems. Many other advantages then appeared: decrease of the temperature of the borehole allowing better operation of the logging tools, better control of the mud rheology with less additives, extended use of MWD/LWD devices. But the most significant advantage is for the oil based muds which can be maintained at surface below their flash point, improving the safety of operations.
This paper recalls and summarizes the results of observations, measurements and studies performed to determine the feasibility of such systems. Operational results are given for several field cases with emphasis on safety. The use of these very simple devices, which have been field proven on normal and high temperature (BHCT = 150°C), is now contemplated for future HP-HT wells.