bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Wellbore Condition on Wireline and MWD Neutron Density Logs
Authors: Allen David F. , Best David L. , Evans Mike , Holenka Jacques M.
Published: December 2007

The wellbore condition and its corresponding effect on log readings must be assessed and corrected for during log quality control and formation evaluation. Differences arise between measurement-while-drilling (MWD) and wireline neutron density, photoelectric factor (PEF) logs made in the same well because the two systems respond differently to the wellbore environment. Differences also occur because of changes in wellbore condition over time.
Determination of the Effective Stress Law for Permeability and Deformation in Low-Permeability Rocks
Authors: Warplnski N. R. , Teufel L. W.
Published: December 2007

Laboratory experiments were performed to determine the effective stress law of tight sandstones and chalk for permeability and deformation. Permeability and volumetric strain data were taken at various stresses and pore pressures and were analyzed with a statistical model-building approach. Results show that the effective stress laws for both processes are variable with stress and pressure, depend on the material, and do not agree well with present theories.
Diagnosis and Evaluation of Fracturing Treatments
Authors: Ayoub J. A. , Brown J. E. , Barree R. D. , Elphick J. J.
Published: December 2007

This paper introduces the pressure derivative in fracturing-pressure analysis. The derivative is shown to enhance the analysis capabilities significantly. The interpretation methodology is presented, and several field data sets and simulations are discussed to illustrate the technique.
Field Performance in the Practical Application of Chlorine Dioxide as a Stimulation Enhancement Fluid
Authors: McCafferty J. F. , Tate E. W. , Williams D. A.
Published: December 2007

New, innovative, and successful application technology has evolved in the practical use of chlorine dioxide for well stimulations. The safe generation and use of chlorine dioxide is paramount in well-stimulation procedures. More than 1, 000 well stimulations have been completed safely with the described method of chlorine dioxide generation. Guidelines and operational procedures have been established for the safe handling of chlorine dioxide in well stimulations. Chlorine dioxide is a powerful oxidant that has been coupled safely with conventional acidization to stimulate producing wells, waterflood injection wells, and saltwater disposal wells. Field applications of chlorine dioxide and acid indicate a synergistic relationship that increases the longevity of the stimulation by removal of formation skin damaging agents. Field results correlate well with laboratory core tests for remediation of formation skin damage. This technology is being applied successfully with consistent results in the V.S., although safety has been a primary issue. This paper provides safe guidelines for the process.
Critical and Subcritical Flow of Multiphase Mixtures Through Chokes
Authors: Perkins T. K.
Published: December 2007

Equations that describe isentropic (adiabatic with no friction loss) flow of multiphase mixtures through chokes can be deduced from the general energy equation. These flow equations are valid for both critical and subcritical flow. Equations, physical property correlations for oil/water/natural gas systems, and a computer method that will handle both flow regimes are described. The procedure will determine whether flow will be in the critical or subcritical regime. The analysis method has been tested by comparing measured and calculated flow rates of 1, 432 sets of literature data comprising both critical and subcritical air/water, air/kerosene, natural gas, natural gas/oil, natural gas/water, and water flows. An average discharge coefficient of 0.826 gave a negligible average error with a 15.4% standard deviation.
A Method for Correcting Dimensionless Fracture Conductivity for Non-Darcy Flow Effects
Authors: Gldley J. L.
Published: December 2007

This paper provides a method of extending the concept of dimensionless fracture conductivity to the design of fracture conductivity in wells to be produced at rates that cause non-Darcy flow down the fracture. Such flow rates are common in gas wells and occasionally occur in oil wells. The correction requires knowledge of the expected producing rate and calculation of a Reynolds number characterizing flow in the fracture near the wellbore.
Material-Balance Techniques for Coal-Seam and Devonian Shale Gas Reservoirs With Limited Water Influx
Authors: King G. R.
Published: December 2007

This paper presents the development of two material-balance methods for unconventional gas reservoirs. One method is appropriate for estimating original gas in place; the second is appropriate for making reservoir predictions. These techniques differ from the material-balance methods for conventional gas reservoirs in that the effects of adsorbed gas are included. For estimating original gas in place, the assumption of equilibrium between the free- and adsorbed-gas phases is required. No additional assumptions are required for reservoir predictions.
Considerations Affecting the Scaling of Displacements in Heterogeneous Permeability Distributions
Authors: Hewett Thomas A. , Behrens Ronald A.
Published: December 2007

Dispersion and convection scaling can be used to model 1D miscible and immiscible flows, respectively, but these scaling techniques fail in multidimensional heterogeneous permeability distributions. The length dependence observed for dispersion induced by correlated heterogeneity in miscible displacement processes precludes the definition of an effective dispersion coefficient. Effective relative permeabilities can be defined that will reproduce the results of the cross-sectional simulations from which they were derived, but complications arise when they are used in areal models.
Modeling the Vertical Confinement of Injection-Well Thermal Fractures
Authors: Clifford P. J. , Berry P. J. , Gu Hongren
Published: December 2007

Cooling of rock by water injection frequently causes fracturing of wells. This paper describes a 3D simulation model of thermally induced fracturing. It is used to show that fractures often tend to grow vertically into permeable zones. Procedures are outlined for confining fracture growth in wells where it will assist waterflood sweep performance.
Design and Installation of a Subsea Multiwell Drilling Template at Garden Banks Block 189
Authors: Domangue R. J.
Published: December 2007

This paper describes the economics, design, and installation of a simple drilling template that was used to retain or save subsea exploratory and delineation wells in Garden Banks Block 189 (GB 189) in the Gulf of Mexico.
Use and Application of Permanent Downhole Pressure Gauges in the Balmoral Field and Satellite Structures
Authors: Shepherd C. E. , Neve Patrick , Wilson D. C.
Published: December 2007

Downhole gauges installed in Block 16/21 in the North Sea have given invaluable real-time data during extended well testing. These data have improved our understanding of Balmoral and Glamis well and reservoir behavior in the early stages of production. The long-term reliability of these systems has been disappointing. We hope that experience gained with these systems will help others considering their use or contemplating further development of downhole pressure systems.
Reliability Management of Surface-Controlled Subsurface Safety Valves for the TOGI Project
Authors: Moines Einar , Iversen Morten
Published: December 2007

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

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

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

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

The 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

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

Berea 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

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

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

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.
Productivity of Multiple Drainholes or Fractured Horizontal Wells
Authors: Raghavan Rajagopal , Joshi Sada D.
Published: December 2007

This paper provides guidelines to assess the productivity of horizontal-well completions by drilling multiple drainholes or by stimulation with vertical fractures. The paper also offers reliable methods to compute productivity gains for realistic conditions.
Water-Alternating-Steam Process Improves Project Economics at West Coalinga Field
Authors: Hong K. C. , Stevens C. E.
Published: December 2007

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

Development 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

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

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

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

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

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

Water dissolution in crude oil becomes significant at temperatures > 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

A 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

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

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.
Generalized Inflow Performance Relationships for Three-Phase Flow
Authors: Wiggins Michael L.
Published: December 2007

This paper presents generalized liquid inflow performance relationships (IPR's) for three-phase flow in bounded, homogeneous reservoirs and new methods to predict present and future performance during boundary-dominated flow.
A Model for Calculation of Formation Force and Its Application
Authors: Yan Tie , Zhang Jianqun , Hareland Geir , Rajtar J. M.
Published: December 2007

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

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

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.
Exploiting High-Rate Injection and Fracturing To Improve Areal Thermal Conformance in Cyclic Steam Stimulation
Authors: Boone Thomas J. , Gallant Richard J. , Kry P. R.
Published: December 2007

Achieving good areal thermal conformance is a key component in developing an effective steam-based recovery process. This paper describes a test where high-rate pulsed injection (HRPI) of steam has been used to improve areal thermal conformance as part of an operation that uses cyclic steam stimulation. In this process, steam was repeatedly injected at high rates [≈ 2000 m3/d, cold water equivalent volume (CWEV)] for relatively short periods (hours), rather than constantly injecting at lower rates (200 to 300 m3/d) for several weeks or months. The objective of the high-rate injection was to create extensive horizontal fractures at a well. Then, the heat transport capability of steam flow in the fractures was exploited to improve areal thermal conformance. The well at which this test was conducted is surrounded by six observation wells. In the previous 5 years of cyclic steam stimulation at the injector, little temperature change had occurred in these wells. Within hours of starting HRPI, significant heat was seen at three of the surrounding observation wells. After several pulses, a fourth observation well showed significant temperature increases. This paper documents the procedures used in the test and data collected during the test.
A New Wireline Tool for In-Situ Stress Measurements
Authors: Thiercelin M. J. , Plumb R. A. , Desroches Jean , Bixenman P. W. , Jonas J. K. , Davie W. R.
Published: December 2007

This paper describes the development of a wireline tool for open-hole stress measurements. This tool includes a straddle packer module comprising surface controlled valves, pressure gauges, and a downhole pump. Stress measurements are either based on the micro-hydraulic fracturing technique or the H.T.P.F. technique (Hydraulic Tests on Pre-existing Fracture). Before presenting the tool, we derive specifications for obtaining reliable stress measurements. The maximum differential pressure (which is the interval pressure minus wellbore pressure) that the tool can currently sustain is 28 MPa (4000 psi) and flow rates of the order of 1 liter/min can be achieved. Results of field tests are described which demonstrate the high quality of the tool response.
Physical Explanations of Non-Darcy Effects for Fluid Flow in Porous Media
Authors: Ma Huiping , Ruth Douglas
Published: December 2007

The nature of nonlinear flow in porous media is analyzed by means of the volumetric averaging approach for a medium modeled by di-verging/converging capillaries. To clarify the mechanism responsible for the nonlinearity, a physical explanation is deduced for the dispersion term in the averaged momentum equation. With the present periodical model, the numerically obtained microscopic flow fields, in association with the macroscopic coefficients calculated by the average momentum balance, indicated quantitatively that the microscopic inertial phenomena, which lead to distorted pore velocity and pressure fields, is the fundamental reason for the onset of nonlinear effects as filtration velocity increases.
Pushing the Limits for Extended Reach Drilling: New World Record From Platform Statfjord C, Well C2
Authors: Alfsen Turid E. , Heggen Steinar , Blikra Harald , Tjøtta Helge
Published: December 2007

Well 33/9-C2 with its horizontal reach of 7290 m is a new world record in extended-reach drilling. The well was drilled from the Statfjord C platform in the North Sea, Norwegian sector, and has a total length of 8761 m MD. This paper will describe the planning techniques used, with focus on coping with limitations in equipment and formation. It will also present a case history of the drilling operations including operational experience gained and comparisons between simulated drilling parameters and field data.
A Nonlinear Approximation for the Pressure Behavior of Heterogeneous Reservoirs
Authors: Kuchuk Fikri J. , Habashy Tarek M. , Torres-Verdin Carlos
Published: December 2007

Recent years have seen extensive use of analytical techniques to study pressure behavior in layered, laterally, and radially composite systems. In this paper, we present a new approximate method to describe the transient pressure behavior of heterogeneous reservoirs. The reservoir is subdivided into a collection of subregions with different rock properties embedded in an otherwise homogeneous background that is defined as a homogeneous region, a stack of layers, or a radially symmetric composite structure. However, both the background medium and the anomalous region may exhibit three-dimensional (3D) anisotropy. The proposed method of solution is formulated in the Laplace transform domain wherein both wellbore storage and skin effects can be included in an algebraic fashion. Beginning with the integral equation solution for the pressure diffusion in porous media, we derive a nonlinear approximation with respect to the spatial variations in reservoir properties. This solution may accurately handle high contrasts in reservoir properties as well as large anomalous regions such as deltaic sandstones and sorted channels systems. For small contrasts, the proposed nonlinear approximation reduces to the Born approximation. We present comparison tests with available analytical solutions such as those related to finite-width strips.
Deepwater Gulf of Mexico Turbidites— Compaction Effects on Porosity and Permeability
Authors: Ostermeier R. M.
Published: December 2007

The deepwater Gulf of Mexico is now a major area of activity for the U.S. oil industry. Compaction causes particular concern because most prospective deepwater reservoirs are highly geo-pressured and many have limited aquifer support; water injection may also be problematic. Thus, economic development may require significant drawdowns with ensuing compaction and its attendant problems.

To address some of the issues associated with compaction, we initiated a special core-analysis program to study compaction effects on turbidite sand porosity and permeability specifically. This program also addressed a number of subsidiary but no less important issues, such as sample characterization and quality, sample preparation, and test procedures. These issues are particularly pertinent, because Gulf of Mexico turbidites are generally unconsolidated, loose sands, and are thus susceptible to a whole array of potentially serious core-disturbing processes.

One key result of the special core analysis program is that turbidite compressibilities exhibit large variations in both magnitude and stress dependence. These variations correlate with creep response in the laboratory measurements. The data suggest creep may be important because observed creep relaxation rates, although slow on a laboratory time scale, are much faster than typical reservoir drawdown rates.

The effects of compaction on permeability are significant. To eliminate complicating effects caused by fines movement, we made oil flow measurements at initial water saturation. The measurements indicate compaction reduces permeability four to five times more than porosity on a relative basis.
Integrated Geostatistics For Modeling Fluid Contacts and Shales in Prudhoe Bay
Authors: Pérez Godofredo , Chopra A. K. , Severson C. D.
Published: December 2007

Geostatistics techniques are being used increasingly to model reservoir heterogeneity at a wide range of scales. A variety of techniques is now available with differing underlying assumptions, complexity, and applications. This paper introduces a novel method of geostatistics to model dynamic gas-oil contacts and shales in the Prudhoe Bay reservoir.

The method integrates reservoir description and surveillance data within the same geostatistical framework. Surveillance logs and shale data are transformed to indicator variables. These variables are used to evaluate vertical and horizontal spatial correlation and cross-correlation of gas and shale at different times and to develop variogram models. Conditional simulation techniques are used to generate multiple three-dimensional (3D) descriptions of gas and shales that provide a measure of uncertainty. These techniques capture the complex 3D distribution of gas-oil contacts through time.

We compare results of the geostatistical method with conventional techniques as well as with infill wells drilled after the study. Predicted gas-oil contacts and shale distributions are in close agreement with gas-oil contacts observed at infill wells.
In-Situ Optical Fluid Analysis as an Aid to Wireline Formation Sampling
Authors: Smits A. R. , Fincher D. V. , Nishida Katsuhiko , Mullins O. C. , Schroeder R. J. , Yamate Tsutomu
Published: December 2007

This paper describes the basic theory of operation for a newly developed wireline tool that uses optical principles for continuous analysis of fluid in the flowline of a wireline formation fluid sampler. The tool has a visible and near-infrared absorption spectrometer for fluid discrimination and a refractometer for free gas detection. The Effective Flow Stream (EFS) model has been developed to interpret the measured data and to estimate the volume fraction of water and oil in the tool's flowline for biphasic flow. For triphasic flow, the technique can give a quantitative estimate of water, along with a qualitative evaluation of the amount of oil and gas. We present an example of showing tool response in the laboratory, introduce applications of the technique for aiding formation sampling, and, finally, illustrate the implementation of this technique with field examples.
A Parameter-Based Approach for Two-Phase-Equilibrium Prediction With Cubic Equations of State
Authors: Kaul Pradeep , Thrasher R. L.
Published: December 2007

A parameter-based approach for two-phase-equilibrium prediction that uses the two-parameter Peng-Robinson equation of state (EOS) has been developed. This approach takes advantage of the special mathematical forms of the ideal mixing and excess parts of the Gibb's free energy to reduce the NC-component equilibrium problem to a minimization problem in three or four variables, depending on whether binary interaction coefficients (BIC's) are zero or nonzero. The Gibb's free energy is minimized in two steps. The ideal mixing term is minimized first subject to certain constraints that include the mixing rules for the EOS parameters. A second minimization is performed over the total Gibb's free energy with the Lagrange multipliers from the first minimization as a reduced set of variables in place of the usual component-related variables.

The new approach has been applied to develop parameter-based versions of the Newton-Raphson and trust-region methods for performing flash calculations as well as the phase-stability test to handle the transition from one to two phases. These methods have been implemented in computer programs and tested on phase-behavior problems taken from the petroleum literature.

In the case of zero BIC's, the reduction in the number of variables produces substantial reduction in computational cost compared with component-based methods, especially as the number of components increases, while convergence behavior is essentially unchanged. For the nonzero BIC case, however, a practical implementation requires the introduction of approximations that compromise convergence and offset the lower cost per iteration.
A Simple Predictive Calculation for the Viscosity of Liquid Phase Reservoir Fluids With High Accuracy for CO2 Mixtures
Authors: Fong W. S. , Sandler S. I. , Emanuel A. S.
Published: December 2007

A simple and accurate correlation has been developed for predicting the viscosity of CO2-reservoir oil mixtures from composition. The method is suitable for equation-of-state based reservoir simulations, and is useful for a wide range of oil viscosities from 0.2 to 400,000 cp. The correlation is based on a generalized power mixing rule and was developed with experimental viscosity data from 20 oil systems, ranging from light oils to heavy bitumens. The pressure-temperature range of the data was 14.7–7000 psi and 70–255°F. A Peng-Robinson equation of state characterization was developed for each of the oils to match PVT data. This characterization was then used in the viscosity correlation. Accurate predictions require an experimental value of CO2-free reservoir oil viscosity at reservoir temperature and above bubble point pressure. For the oils and bitumens tested, this method predicts oil-solution gas- CO2 mixture viscosity with 12.5% average absolute deviation (AAD).
Simulation of Production and Injection Performance of Gas Storage Caverns in Salt Formations
Authors: Hagoort Jacques
Published: December 2007

This paper presents a simple yet comprehensive mathematical model for simulation of injection and production performance of gas storage caverns in salt formations. The model predicts the pressure and temperature of the gas in the cavern and at the wellhead for an arbitrary sequence of production and injection cycles. The model incorporates nonideal gas properties, thermodynamic heat effects associated with gas expansion and compression in the cavern and tubing, heat exchange with the surrounding salt formation, and nonuniform initial temperatures but does not include rock-mechanical effects. The model is based on a mass and energy balance for the gas-filled cavern and on the Bernoulli equation and energy balance for flow in the wellbore. Cavern equations are solved iteratively at successive timesteps, and wellbore equations are solved within an iteration cycle of the cavern equations. Gas properties are calculated internally with generally accepted correlations and basic thermodynamic relations. Example calculations show that the initial temperature distribution has a strong effect on production performance of a typical gas storage cavern. The primary application of the model is in the design, planning, and operation of gas storage projects.
System Safety Analysis of Well-Control Equipment
Authors: Fowler J. H. , Roche J. R.
Published: December 2007

Two techniques are used for reliability analysis of a blowout preventer (BOP) and a hydraulic control system. Failure modes and effects analysis (FMEA) examines each part and the consequences of its malfunction. Fault tree analysis (FTA) traces undesired events to their causes. Reliability calculations and data sources are addressed.
Design, Drilling, and Testing of a Deviated HTHP Exploration Well in the North Sea
Authors: Seymour K. P. , MacAndrew Robert
Published: December 2007

Significant quantities of hydrocarbon reserves are contained in North Sea high-temperature, high-pressure (HTHP) reservoirs. De-velopment of these reserves will require deviated wells. This paper outlines the planning, drilling, and testing of the first deviated HTHP well in the U.K. sector of the North Sea.
Field and Laboratory Verification of Sand-Production Prediction Models
Authors: Morita Nobuo
Published: December 2007

Many completion options are available to minimize sand problems. Formation-strength analysis is essential to selecting and designing the best completion method from these options. This paper addresses the accuracy of several formation-strength models to help those who plan to develop or to use these models in the future.
Dual Openhole Gravel Pack in Shaly Fine Sands
Authors: Moricca Giuseppe , Ripa Giuseppe , Rucci Domenico , Pitoni Enzo
Published: December 2007

This paper discusses the design and execution of dual-zone gravel packs in very shaly and silty formations of median sand grain size less than 30 μm. An oversized gravel was selected for sand control and, as a consequence, the openhole gravel-pack technique was adopted to reduce the effect of intermixing between formation and gravel-pack sand. During the completions in the first five wells, we encountered and solved several operational problems, including those involving (1) borehole stability, (2) setting of inflatable packer for zone isolation, (3) hole preparation, and (4) gravel placement. From the lessons we learned, another 11 wells were completed with dual openhole gravel packs without significant problems. After 1 year of production, the flow performance from the wells met or exceeded the initial objectives.
Equilibrium and Stability of Static Interfaces in Biconical Pore Segments
Authors: Toledo Pedro G. , Scriven L. E. , Davis H. Ted
Published: December 2007

The equilibrium and stability of interfaces largely set the fluid distribution in a porous medium. Here we determine the equilibrium and stability of axisymmetric interfaces, namely head and neck menisci, in biconical pore segments. We also report relationships between capillary pressure, Pc, and mercury volume, VHg, for stable interfaces. These results are used in our Monte Carlo simulation of volume-controlled mercury porosimetry.