bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computer Simulation Predicts Unfavorable Mud Rate and Optimum Air Injection Rate for Aerated Mud Drilling
Authors: Guo Boyun , Hareland Geir , Rajtar Jerzy 
Published: December 2007

Summary
In certain areas, the use of aerated mud as a circulating medium for drilling oil and gas wells is becoming an attractive practice. This is because aerated drilling has many advantages over conventional mud drilling, such as a higher penetration rate, less formation damage, minimized lost circulation, and lower drilling cost. The importance of maintaining adequate air and mud flow rates is generally recognized in aerated drilling operations. However, it remains unclear to drilling operators as to what constitutes an "adequate flow rate." On the basis of computer simulation, this paper discusses carrying capacity of an aerated mud and the optimum air-injection rate that ensures a maximum penetration rate. It is found in this study that the carrying capacity of an aerated mud is very different from that of both the conventional mud and pure air. There is an unfavorable range of mud flow rate that provides lower carrying capacity of the aerated fluid for a given air injection rate. As a unique characteristic of multiphase flow, there exists an air injection rate that gives the lowest flowing annulus pressure for a given well geometry and a mud rate. By considering both the carrying capacity and flowing annulus pressure, an optimum combination of mud and air rates can be determined. This optimum combination of flow rates should ensure a maximum penetration rate for a given well geometry. This paper provides drilling operators with a means of optimizing aerated mud drilling.
Performance of Tubular Connections Under the Loading Conditions of Horizontal Wells
Authors: Tsuru Eiji , Ueno Masakatsu , Ogasawara Masao , Yonezawa Tetsuo 
Published: December 2007

SummaryThis study deals with the negative effects of bending stress and casing wear on tubular connections. The joint strength of three connection types, API long round thread (LTC), API buttress thread (BTC), and typical premium joint (PJ), was measured with a full-size combined loading tester. Measurements were also made for the connections simulating wear induced by drilling operations. The sealing ability of the connections was evaluated under bending and wearing conditions. Numerical simulations were undertaken to investigate the failure mechanism of the connections.The results indicate that LTC joint strength is lowered by bending, though that of BTC and PJ is not degraded. Joint strength is reduced in direct proportion to the wear area ratio of the pipe body. In sealing ability, only the premium connection maintained leak resistance under combined loading with bending. Axial loading is more detrimental to sealing integrity than the bending moment. In conclusion, the connection performance data can be useful in designing safer horizontal well casings.
Normalization of Cased-Hole Neutron Logs, Slaughter Field, Cochran, and Hockley Counties, TX
Authors: Dobitz J. K. , Cole R. M. 
Published: December 2007

Summary
Currently accepted methods of normalizing cased hole neutron logs to porosity were determined to be unusable under conditions encountered during a reservoir study of the Texaco Bob Slaughter Block and nearby leases in Slaughter Field, Cochran, and Hockley Counties, TX. A new method for normalizing a large number of neutron logs was developed that is applicable in a wide range of situations.
The method uses statistical parameters derived from available core and modern log suites to transform dependably the neutron log response. Unlike earlier techniques, a linear transform equation is developed for each log being normalized. The method calculates the slope of the transform equation by comparing the standard deviation of the neutron values to a reference log with similar characteristics over a specified depth interval. The intercept of the transform line is then calculated from average porosity values for a specific interval, but not necessarily the same interval used to calculate the standard deviation. The technique eliminates inaccuracies in the normalization process created by tool differences, scale factors, and hole size. The effect of changes in lithology and formation fluid on the resulting porosity values are also minimized.
Detailed Characterization of a Fractured Limestone Formation by Use of Stochastic Inverse Approaches
Authors: Datta-Gupta Akhil , Vasco D. W. , Long J. C. S. , D'Onfro P. S. , Rizer W. D. 
Published: December 2007

Summary
We discuss two inverse approaches to construction of fracture-flow models and their application in characterizing a fractured limestone formation. The first approach creates "equivalent discontinuum" models that conceptualize the fracture system as a partially filled lattice of conductors that are locally connected or disconnected to reproduce the observed hydrologic behavior. An alternative approach— i.e., "variable aperture lattice" models—represent the fracture system as a fully filled network composed of conductors of varying apertures or hydraulic conductivities. The fracture apertures are sampled from a specified distribution, usually log-normal, which is consistent with field data. The spatial arrangement of apertures is altered through inverse modeling to fit the available hydrologic data, such as transient pressure and/or tracer data.
Unlike traditional discrete fracture-network approaches that rely on fracture geometry to reproduce flow and transport behavior, the inverse methods directly incorporate hydrologic data in deriving the fracture networks and thus naturally emphasize the underlying features that impact fluid flow and transport. However, hydrologic models derived by inversion are nonunique in general. We have addressed such nonuniqueness by examining an ensemble of models that satisfy the observation data within acceptable limits. We then determine properties that are shared by the ensemble of models and their associated uncertainties to create a conceptual model of the fracture system. We show the fracture-flow model to be consistent with geophysical imaging.
Predictive Model for Viscous Fingering in Compositional WAG Floods
Authors: Barker J. W. , Evans S. C. 
Published: December 2007

Summary
We present a predictive model, with no adjustable parameters, for viscous fingering in compositional water-alternating-gas (WAG) floods. The model is used to generate pseudofunctions for use in a conventional compositional simulator. The model is applied successfully to three test cases, including one in a simple, heterogeneous reservoir.
V-L-L Equilibria Data andK-Values for Pseudo-components of a Crude Oil
Authors: Beladi Michael K. , Barrufet Maria A. , Eubank Philip T. , Wu Ching H. 
Published: December 2007

AbstractCompositional simulation of thermal recovery processes requires V-L-L (vapor/liquid-hydrocarbon/liquid-water) equilibria data to model distillation mechanisms. We have performed steam distillation experiments to obtain 3-phase equilibrium data and equilibrium ratios (K-values) for crude oil pseudo-components.A laboratory/empirical technique is developed to determine 3-phase K-values of crude oil pseudo-components/water systems at high temperatures and pressures. A 12 °API gravity crude oil is used as the test oil for this study. Isochoric steam distillation experiments are performed to obtain the vapor phase compositions for temperatures ranging from 250 to 500 °F at equilibrium saturation pressures.Three experimental models are devised to calculate the 3-phase K-values. These models are,SWID-1 stage-wise isochoric distillation of type 1; this test is conducted under stepwise increase of temperature between each equilibrium stage.SWID-2 stage-wise isochoric distillation of type 2; this test is conducted at a constant temperature for all equilibrium stages.IDA-3 isochoric distillation analysis of type 3; this test uses a constant initial composition in the cell for each equilibrium stage.Three-phase equilibrium AT-values are computed using the experimental data (SWID-1, SWID-2 and IDA-3) and a compositional material balance model (CMBM). This model uses experimental vapor phase compositions and a correlation for the hydrocarbon solubility in water to calculate the liquid hydrocarbon compositions. The correlations for hydrocarbon solubility in the water phase are based on data and correlations from literature. The pseudo-components are defined using a modified pseudoization technique based on Whitson's characterization scheme.These results may provide basic separation data that account for steam distillation mechanisms involved in thermal processes. We conclude that 3-phase equilibrium K-values for the oil pseudo-components are a function of pressure, temperature and a weak function of the initial compositions.
Foam-Proppant Transport
Authors: Valkó Peter , Economides M. J. 
Published: December 2007

Summary
The rheology of foams has been the subject of recent work in which the principle of volume equalization has been proved to describe flow behavior effectively. In the present work this model is combined with the constant-internal-phase/constant-viscosity assumption to describe the transport of solid particles. Laminar and nonlaminar (drag-reduced) friction pressures, the transition criterion, and solid settling velocity are given in a unified framework.
The Impact of Constitutive Laws on Wellbore Stability: A General Review
Authors: Charlez P. A. 
Published: December 2007

Summary
This paper is focused on soft deep rocks that can induce strong well-bore-stability problems. In the first part, it is shown that these rocks generally exhibit plastic-type behaviors. In the second part two elasto-plastic models (Cam-Clay and Laderock) are briefly presented. In the third part, these constitutive laws are applied to wellbore stability through analytical solutions or finite element codes. Finally, in the fourth part, a case history is discussed in detail. We insist on the difficulty to properly define the boundary conditions of the problem (in-situ stresses and virgin pore pressure) and on the subjectivity of the criterion translating the boundary wellbore problem in stability recommendations. Some keys for future research are proposed.
Abnormally High Fluid Pressures and Associated Porosities and Stress Regimes in Sedimentary Basins
Authors: Yassir N. A. , Bell J. S. 
Published: December 2007

Summary
The relationships between overpressures and porosity and overpressures and stress regime are found to differ significantly according to the geological setting and overpressure generating mechanism. These factors must be taken into account in pore pressure prediction techniques and in correlations between pore pressure and minimum horizontal stress. Two examples from overpressured Canadian basins are presented to illustrate the above.
Hole-Cleaning Capabilities of an Ester-Based Drilling Fluid System
Authors: Kenny Patrick , Hemphill Terry 
Published: December 2007

Summary
Well 33/9-C02, located in the Statfjord field in the Norwegian sector of the North Sea, held the world record in extended-reach drilling from 1993-95. To successfully drill a well of this type, an efficient drilling fluid is required to suspend the weighting material and provide good carrying capacity. The ester-based mud system used in the 12¼ and 8½-in. hole sections of this well exhibited excellent holecleaning capabilities. This paper describes the fluid's performance in the field and in the laboratory where the fluid was tested under downhole conditions. Fluid rheological behavior is described with the more accurate yield-power law (YPL) (Herschel-Bulkley) model.
Passive Imaging of Hydrofractures in the South Belridge Diatomite
Authors: Ilderton D. C. , Patzek T. W. , Rector J. W. , Vinegar H. J. 
Published: December 2007

Summary
We present the results of a seismic analysis of two hydrofractures spanning the entire diatomite column (1110-1910 ft or 338-582 m) in Shell's Phase II steamdrive pilot in South Belridge, California. These hydrofractures were induced at two depths (1110-1460 and 1560-1910 ft) and imaged passively using the seismic energy released during fracturing. The arrivals of shear waves from the cracking rock ("microseismic events") were recorded at a 1 ms sampling rate by 56 geophones in three remote observation wells, resulting in 10GB of raw data. These arrival times were then inverted for the event locations, from which the hydrofracture geometry was inferred. A five-dimensional conjugate-gradient algorithm with a depth-dependent, but otherwise constant shear wave velocity model (CVM) was developed for the inversions. To validate CVM, we created a layered shear wave velocity model of the formation and used it to calculate synthetic arrival times from known locations chosen at various depths along the estimated fracture plane. These arrival times were then inverted with CVM and the calculated locations compared with the known ones, quantifying the systematic error associated with the assumption of constant shear wave velocity. We also performed Monte Carlo sensitivity analyses on the synthetic arrival times to account for all other random errors that exist in field data. After determining the limitations of the inversion algorithm, we hand-picked the shear wave arrival times for both hydrofractures and inverted them with CVM. Finally, to correct for the areal inhomogeneity of the rock, we calculated the distortion of conical waves that were generated by air gun blasts in a remote observation well. This novel technique improved significantly the accuracy of the event locations in the shallow hydrofracture. The azimuth of both hydrofractures was N21° ±4°E. In each treatment well, there were two separate hydrofractures at two different depths that correspond to the diatomite layers with higher permeabilities. Both shallow hydrofractures were asymmetrical. Initially, the upper NE wing was 230 ft long, whereas the lower SW wing was only 30 ft long. The deep hydrofracture was symmetrical and the wings of its two parts were initially 130 and 10 ft long, respectively. These conclusions agree well with temperature surveys in the surrounding observation wells during steam injection.
Vertical Multiphase Flow Correlations for High Production Rates and Large Tubulars
Authors: Aggour M. A. , Al-Yousef H. Y. , Al-Muraikhi A. J. 
Published: December 2007

Summary
Numerous correlations exist for predicting pressure drop in vertical multiphase flow. These correlations, however, were all developed and tested under limited operating conditions that do not match the high production rates and large tubulars normally found in the Middle East fields. This paper presents a comprehensive evaluation of existing correlations and modifications of some correlations to determine and recommend the best correlation or correlations for various field conditions. More than 400 field data sets covering tubing sizes from 2⅜ to 7 in., oil rates up to 23,200 B/D, water cuts up to 95%, and gas/oil ratio (GOR) up to 927 scf/STB were used in this study. Considering all data combined, the Beggs and Brill correlation provided the best pressure predictions. However, the Hagedorn and Brown correlation was better for water cuts above 80%, while the Hasan and Kabir model was better for total liquid rates above 20,000 B/D. The Aziz correlation was significantly improved when the Orkiszewski flow-pattern transition criteria were used.
A Model for Predicting Injectivity Decline in Water-Injection Wells
Authors: Pang Shutong , Sharma M. M. 
Published: December 2007

SummaryWe propose a new method to predict the injectivity decline for water-injection wells. Both internal and external filtration are considered in this method. A transition time from internal to external filtration is calculated by use of the trapping efficiency obtained from Stokesian dynamics simulations. The radius and the permeability of the damage zone are calculated by use of a deep-bed filtration model. Equations are derived that allow us to combine the flow resistance in the external and internal filter cakes to obtain the overall decline in injectivity.
A Modern Gunbarrel of Unique Design
Authors: Powers M. L. 
Published: December 2007

Summary
Although regarded by many as obsolete, gunbarrels (or wash-tanks) are still used for primary oil treating in many areas. This paper describes a modern gunbarrel constructed from an existing 5,000-bbl tank. Oil treating without the addition of heat was feasible because of the combination of relatively warm produced fluid and lenient basic sediment and water (BS&W) limits. The subject vessel provides gas separation and contains two spreaders that were designed to provide good oil- and water-phase retention and to facilitate solids separation and removal. The oil-phase spreader has a diameter equal to 78% of that of the vessel. It incorporates a unique deep skirt, having a pattern of restrictive exit ports that imposes uniform radial oil-phase flow over a wide range of rates and is relatively insensitive to minor misleveling, which is not the case for common serrated-skirt spreaders. The design of the unique vessel internals permitted assembly without welding at the battery site. Differences in the contribution of the water-bath zone of heated and nonheated gunbarrels are discussed, and it is shown that nonheated-vessel designs that increase water-phase residence time and facilitate convection in the water-bath are the most effective, a result of conservation of intrinsic well-stream heat. It is also demonstrated that the optimum oil-blanket thickness is a compromise between oil-residence time and oil temperature in nonheated vessels that capture water-phase heat. Vessel internals that entrap oil beneath water (such as the oil-phase spreader of the subject vessel) are subjected to a buoyant force in addition to the weight of water displaced by steel. This effect is discussed, and design equations are developed to calculate the net buoyant force exerted upon a specific spreader and the gauge steel from which a spreader must be constructed to preclude floating. An example is included that illustrates the application of these equations to the subject vessel.
Wettability and Relative Permeability of Prudhoe Bay: A Case Study in Mixed-Wet Reservoirs
Authors: Jerauld G. R. , Rathmell J. J. 
Published: December 2007

Summary
This paper describes the variation in wettability and relative permeability at Prudhoe Bay. We show that measurements are consistent with recent theories of the relationship between water-saturation, pH, wettability and relative permeability.1 In particular, the wettability of the reservoir changes from water-wet low on structure near the water/oil contact to mixed-wet behavior higher on structure. Increasing oil-wetting character is correlated to decreasing water saturation. Changes in wettability are also accompanied by changes in water-flood recovery efficiency and are optimum at Amott indices approaching zero. Lithology also impacts recovery efficiency, with more clay-rich rocks having higher residual oil saturations.
The Scaleup of Two-Phase Flow in Porous Media Using Phase Permeability Tensors
Authors: Pickup Gillian E. , Sorbie Kenneth S. 
Published: December 2007

Abstract
The effects of different levels of geological heterogeneity on a fluid displacement process may be captured at a larger scale using scaleup techniques. In the context of reservoir simulation, these are algorithms which should reproduce the results of fine grid calculations on a coarser grid. These techniques are referred to as pseudo-isation, the main objective being to produce pseudo-functions which can be used on the coarse grid. When carried out successfully, the pseudo-functions (e.g. pseudo relative permeabilities) incorporate the interaction between the fluid mechanics and the heterogeneity as well as correcting for numerical dispersion. These pseudo-functions also depend on the viscous/capillary and viscous/gravity ratios and are valid for the boundary conditions relevant to the particular flows.
For single phase flow, the scaleup problem involves the derivation of effective permeability which, in general, is a tensor quantity. Multi-phase flow is more complex since scaled-up dynamic transport quantities must be calculated which depend on phase saturation, flow rate etc. In this paper, we present a method which extends the idea of tensor (absolute) permeability to tensor effective phase permeabilities. They are extensions of conventional functions which also include the off-diagonal phase crossflow terms which may be important in certain systems. Two phase tensor methods are presented which are valid (a) in the capillary equilibrium limit and (b) for arbitrary values of viscous/capillary and viscous/gravity ratios. Numerical examples of the application of these methods are presented for ripple-bedded systems where the two phase crossflow effects are significant, and where oil trapping within the lamina structure may occur under certain conditions. The results show that it is important to use phase tensors in upscaling where gravity effects are significant, in order to generate the correct vertical flows.
Application of Oil-Based-Mud Pressure Coring to the Determination of In-Situ Water Saturations
Authors: Charlson G. S. , DeRuiter R. A. , Spence A. P. , Warner H. R. 
Published: December 2007

Summary
This paper describes a field project which applied pressure coring using oil-based mud (OBM) to determine whether a surfacing correction was needed to use OBM-core water saturations (SW) as accurate values for in-situ Sw. Six OBM pressure cores were cut in two Prudhoe Bay field wells, one in the low Sw area and the other in the higher SW area. This paper discusses the equipment and procedural changes, both in the field and in the laboratory, required for this project.
Pressure cores were taken from two geologically different intervals: the Sag River sandstone and the Ivishak (Sadlerochit) sandstone. The results of this project are that for the Ivishak sandstone, no water was expelled during the thawing (taken to be equivalent to core depressuring) for the full range of Sw (1 to 45%); but for the Sag River sandstone, some water was expelled for samples with Sw values of 25 to 40%. The difference in water-expulsion results is attributed to differences in pore structure. Finally, the application of these results to the calculation of in-situ Sw is discussed.
Microbial Profile Modification With Spores
Authors: Bae J. H. , Chambers K. T. , Lee H. O. 
Published: December 2007

Summary
To overcome the shortcomings of conventional, near-wellbore profile modification methods, a microbial profile modification (MPM) method with spores was investigated. A halotolerant, spore-forming mesophile was isolated and characterized. These biopolymer-producing spores propagate easily in Berea cores with permeabilities more than about 500 md. With a specifically formulated nutrient package, they are readily germinated and produce biofilm, which reduces the permeability of the rock. The depth of penetration and the degree of permeability reduction can be controlled by varying injection schemes.
Useful Concepts for Decline-Curve Forecasting, Reserve Estimation, and Analysis
Authors: Fetkovich M. J. , Fetkovich E. J. , Fetkovich M. D. 
Published: December 2007

Summary
The purpose of this paper is to give engineers responsible for making forecasts and determining reserves for numerous operated or nonoper-ated wells some guidelines and fundamental concepts to allow them to make these forecasts and determinations more quickly and accurately.