bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential of Repeated Polymer Well Treatments
Authors: Lakatos István , Lakatos-Szabó Julianna , Munkácsi István , Tröböczki Sándor
Published: December 2007

This paper analyzes field results obtained by routine application of a polymer/silicate well treatment technique at the Algyó-2 field in Hungary. First, the reservoir is described briefly; then, the basic concept of the method is outlined. Reference is made to the multifunctioning chemical mechanism of gelation and the favorable rheological properties of the treating fluids that jointly result in a highly selective placement and an efficient permeability reduction in the target reservoir space. Application of the method 17 times in 16 producing wells yielded more than 90 000 Mg of incremental oil production. Typical well behaviors also are illustrated. Finally, the potential of repeated treatments is discussed, taking laboratory and field results into account.
Three-Fluid Wetting Transitions and Their Effects on Three-Phase Flow Through Porous Media
Authors: Smith Duane H. , Covatch Gary L. , Lowry William E.
Published: December 2007

From phase and wettability studies on bulk phases, we predicted the fluid-fluid-fluid dispersion morphologies that could be expected for ex-situ dispersions (formed before injection) and for the dispersions after they were injected into a porous medium. From videomicroscopic studies of the flow of the dispersions through an etched microvisual cell, we determined the actual morphologies of the dispersions during flow. Three different wettability conditions and three different morphologies of flowing dispersions were observed.
Stochastic Modeling of Reservoir Architecture for Field Management
Authors: Taheri Mojtaba
Published: December 2007

This paper outlines a probabilistic geologic modeling system developed to describe and characterize heterogeneous fluvio-deltaic sandstone reservoirs in the San Diego area, Orinoco belt, eastern Venezuela. The model uses field, well, and laboratory data to simulate synthetic stratigraphic sections in different directions and to delineate the geometry, continuity, and anisotropy of sand bodies and the regional distribution of internal reservoir properties (porosity, permeability, and hydrocarbon saturation). From a stochastic viewpoint, the model introduces the following improvements: (1) a Poisson process to predict the occurrence of sedimentary sand bodies in the stratigraphic sections, (2) facies proportion curves to condition the occurrence of sand bodies on the depositional environments, (3) Latin hypercube sampling (LHS) as a more precise sampling method in simulation, and (4) a geometric computer modeling technique (QUADTREES) to calculate the reservoir properties and to delineate complex geometries and effective drainage areas. These techniques are illustrated by use of field data from a pilot development in the San Diego area.
Novel Simulation Techniques Used in a Gas Reservoir With a Thin Oil Zone: Troll Field
Authors: Henriquez Adolfo , Apeland Odd J. , Lie Øystein , Cheshire Ian
Published: December 2007

Choice of production strategy in modem reservoir management relies heavily on numerical simulation. Large fields may require prohibitively large computer times. New techniques were developed to save computer and engineering time: local grid refinement with small timesteps and flux boundary conditions for simulating regions of special interest. The combined use of these techniques allowed flexible, non-time-consuming, user-friendly reservoir simulation of a variety of reservoir management scenarios for Troll field.
Casing Deflection and Centralizer Spacing Calculations
Authors: Juvkam-Wold H. C. , Wu Jiang
Published: December 2007

Equations for calculating casing deflection and determining casing centralizer spacing are derived for 1D, 2D, and 3D wellbores. The load-deflection differential equation for a span of casing between two centralizers is solved by use of the "fixed-ends" boundary condition. The combined effect of casing weight and axial tension on casing deflection is analyzed in detail.
Pressure Transient Analysis of Naturally Fractured Reservoirs with Uniform Fracture Distribution
Authors: Kazemi H.
Published: December 2007

An ideal theoretical model of a naturally fractured reservoir with a uniform fracture distribution, motivated by an earlier model by Warren and Root, has been developed. This model consists of a finite circular reservoir with a centrally located well and two distinct porous regions, referred to as matrix and fracture, respectively. The matrix has high storage, but low flow capacity; the fracture has low storage, but high flow capacity. The flow in the entire reservoir is unsteady state.

The results of this study are compared with the results of the earlier models, and it has been concluded that major conclusions of Warren and Root are quite substantial. Furthermore, an attempt has been made to study critically other analytical methods reported in the literature.

In general, it may be concluded that the analysis of a naturally fractured reservoir from pressure transient data relies considerably on the degree and the type of heterogeneity of the system; the testing procedure and test facilities are sometimes as important. Nevertheless, under favorable conditions, one should be able to calculate in-situ characteristics of the matrix-fracture system, such as pore-volume ratio, over-all capacity of the formation, total storage capacity of the porous matrix, and some measure of matrix permeability.

Introduction

The analysis of flow and buildup tests for obtaining in-situ characteristics of oil and gas reservoirs has received considerable attention in the past decade.

Most of the available techniques result in reliable conclusions in macroscopically homogeneous reservoirs or in the homogeneous reservoirs with only certain types of induced and/or inherent heterogeneity (such as wellbore damage, etc.).
Discriminant Analysis and Neural Nets: Valuable Tools To Optimize Completion Practices
Authors: Nitters Gerrit , Davies D. R. , Epping W. J. M.
Published: December 2007

This paper describes the application of multi-variate statistical techniques, discriminant analysis and neural networks in identifying drilling and other completion practices that impact on well productivity. Discriminant analysis determines whether a well can be assigned to a group of wells, on the basis of a number of common characteristics and using linear multivariate correlations. Neural nets enable the use of nonlinear correlations for such a classification.

In this study, 47 gas wells from two fields were classified into three groups:

Group 1: no production;

Group 2: production below 5900 std m3/h (5 MMscf/D);

Group 3: production over 5900 std m3/h (5 MMscf/D).

The variables used in the discriminant analysis included parameters such as completion type, total height of the perforated interval, mud weight, drawdown during perforation, type of mud and perforation size.

The study has identified and, to some extent, quantified those parameters that either adversely or favourably affect well productivity. The results can be used to adjust operational procedures to maximize well productivity. The parameters identified as increasing productivity reflect, for the most part, sound engineering practices.

Application of neural nets enables further quantification of the effects of petroleum engineering parameters on well productivity and is being developed to make it possible for the most economical preventive and remedial measures to be selected.

However, statistical techniques are applicable only when a sufficiently large data base is available, i.e., they are suitable for reasonably large and fairly mature fields and/or areas.
Computation of the Pseudoskin Factor for a Restricted-Entry Well
Authors: Ding Wenzhong , Reynolds Albert C.
Published: December 2007

Papatzacos and Vrbik proposed formulas for calculating the pseudoskin factor from a restricted-entry well in a single-layer homogeneous reservoir. This work extends their simple analytical formulas to a multilayer case. It is shown that, in applying the new equations, the effective average vertical permeability Yeh and Reynolds defined should be used.
Simulation of Heterogeneous Sandstone Experiments Characterized With CT Scanning
Authors: Ganapathy Seetharaman , Wreath Dana G. , Lim Min T. , Rouse Bruce A. , Pope Gary A. , Sepehrnoori Kamy
Published: December 2007

Coreflood experiments in naturally heterogeneous sandstone outcrop cores were conducted 1ijld simulated. Displacements included waterfloods and polymer floods containing tracers for oil or water during single-phase and two-phase flows. Displacements of viscous polymer solution were unstable. The cores were characterized by air permeability measureIllentson each square centimeter of each face and by computerized tomography (CT) scans of core cross sections spaced 1 cm apart along the core length. Characterization data were used for fine-grid simulations. The agreement between the experiments and simulations is good. Sipmlations with coarser-grid physical descriptions then were made by use of effective properties.
Optimizing Production by Fluid and Rock Studies for the Stevens Sands, North Coles Levee Field, Kern County, California
Authors: Underdown David R. , Schultz Douglas J. , Marino Anthony W. , Miranda Roger , Kullman John M.
Published: December 2007

Drilling and completion fluids optimized by petrographic and capillary suction time (CST) analyses improved well productivity for the lower Stevens sands in Kern County, CA. The fluid systems allowed drilling of a gauge hole, which was essential to a good cement bond and a successful fracture stimulation of the low-permeability formation.
Microseismic Logging: A New Hydraulic Fracture Diagnostic Method
Authors: Mahrer Kenneth D.
Published: December 2007

Hydraulic fracture treatments and fluid injections into fractured wells induce a useful cloud of microseismic sources in the fractured zone. This induced seismicity can last for hours after pumping and pervades the fracture. The source-size population distribution ranges from a countable (50 to 500) number of large, individually distinguishable events to a din of background events. Each source radiates wave motion, which can be recorded only in and near the fracture. A new method uses these motion data, recorded in the cased treatment well, to determine the fracture height and azimuth. The height is found by delineating the location and vertical extent of a spatial anomaly in the background-motion data. The azimuth is derived from the particle-motion polarization of the largest events of the microseismic event population. This paper describes the method, exemplary data sets, theory, and simulations that substantiate this method.
Core-Based Prediction of Lithologic Stress Contrasts in East Texas Formations
Authors: Thiercelin M. J. , Plumb R. A.
Published: December 2007

This paper presents an evaluation of two fundamentally different stress models: an elastic model, which is based on linear transverse isotropic elasticity, and a failure model, which is based on the concept that rocks are in an equilibrium state of shear failure. The models arc evaluated by using physical parameters measured on core, pore pressure, and in-situ stress data from the Gas Research Institute (GRI) Staged Field Experiments (SFE's) in east Texas. It is shown that the elastic and failure models provide satisfactory predictions for most of the lithologies encountered. However, the failure model is more accurate for predicting stress in soft shales. An example of stress predictions based on log-derived elasticity parameters that gives stress estimations comparable to core-based predictions is also shown.
Comparisons of Empirical Viscous-Fingering Models and Their Calibration for Heterogeneous Problems
Authors: Fayers F. J. , Blunt M. J. , Christie M. A.
Published: December 2007

This paper reviews the formulation and parameters for three principal empirical viscous-fingering models: the Koval, Todd and Longstaff, and Fayers methods. All three methods give similar levels of accuracy when compared with linear homogeneous experiments, but they differ in performance in 2D applications. This arises from differences in the formulation of the total mobility terms. The superiority of the Todd and Longstaff and Fayers methods is demonstrated for 2D and gravity-influenced flows by comparison with experiments and high-resolution simulation. The use of high-resolution simulation to calibrate empirical models in a systematic manner is described. Results from detailed simulation demonstrate the sensitivity of empirical model parameters to viscous/gravity ratio, recovery process [secondary, tertiary, or water-altemating-gas (WAG)], and geological heterogeneity. For large amplitude heterogeneities with short correlation lengths, the accuracy of the empirical models is shown to be less satisfactory, but improved by the addition of a diffusive term.
Wettability Studies at the Pore Level: A New Approach by Use of Cryo-SEM
Authors: Robin Michel , Rosenberg E. , Fassi-Fihri Omar
Published: December 2007

Cryo-scanning electron microscopy (Cryo-SEM) is used to study the wettability of reservoir rocks from fluid distribution at irreducible water saturation, Swi, and residual oil saturation, Sor. Results on mixed-wettability cores point out the importance of composition, distribution, and accessibility of minerals in determining the macroscopic behavior of the rocks. For the studied samples, wettability of sandstones is related to the presence of kaolinite, while wettability of carbonates seems to be related to pore-size distribution.
Well-Test-Model Recognition With Laplace Space
Authors: Bourgeois Marcel J. , Horne Roland N.
Published: December 2007

This study presents a mathematical background that justifies a new use of Laplace space in well-test analysis. It enables us to perform the whole parameter identification (CD S, k, h, etc.) in Laplace space or at least gives us a powerful tool to treat pressure data to recognize the model to use for parameter identification in real space. It shows how the Laplace transform of pressure can be plotted with exactly the same behavior as the real pressure function so that the plots keep their familiar shape. The coefficients of the dimensionless parameters also remain the same, which enables us to display a new set of characteristic and easily understandable type curves in Laplace space. The mathematical background also sheds light on use of the Laplace transform to deconvolute flow rates by modifications of earlier techniques that were extremely sensitive to noise in the data. The Laplace-space approach provides an entirely new way of examining and understanding well-test results. It has been applied successfully to noisy, simulated data and real field data where conventional interpretation could not illuminate ambiguities.
Multipoint Interference Test in a Single Horizontal Well
Authors: Zhu Tao , Tiab Djebbar
Published: December 2007

A new horizontal well testing technique, the multipoint interference (MPI) technique, is developed in a single horizontal well. This method is more sensitive than conventional buildup or drawdown tests to reservoir heterogeneities along the horizontal segment of the well. In MPI tests, the fluid is produced at a section or perforations at one end of the horizontal portion of the well and the pressure is recorded at one or more observation points (gauges) at the other end. Solutions of the pressure-transient behavior for spherical fluid flow near a linear discontinuity in a vertically confined formation are developed by using unconventional image theory. The pressure derivative was found to provide distinguishing features for analyzing pressure behavior of MPI tests in a heterogeneous reservoir. The straight-line plot of p vs. 1t provides a simple method for analyzing MPI tests. Type curves based on the model developed in this study can be used to determine reservoir properties, such as permeability and porosity, and to detect and locate the reservoir boundaries. The practical utility of MPI tests is demonstrated by several theoretical examples. The solutions developed in this study provide new insight into the pressure behavior of various flow regimes observable in MPI tests. The resulting equations are relatively simple and easy to apply.
Characterization of Devonian Shales With X-Ray Computed Tomography
Authors: Watson A. T. , Mudra Jim
Published: December 2007

The paper investigates use of X-ray computed tomography (CT) for determining properties of Devonian shales. A dual-scan method is used to determine storage distribution quantitatively. Fractures considerably smaller than the resolution of the instrument were detected. Features observed in the CT images were validated by thin-section analysis.
Influence of an Invaded Zone on a Multiprobe Formation Tester
Authors: Goode Peter A. , Thambynayagam R. K. Michael
Published: December 2007

When an oil or gas well is being drilled, some of the borehole fluid (mud filtrate) leaks into the formation, displacing the native reservoir fluid. This creates an invaded zone around the wellbore. The invading fluid will generally have a mobility and compressibility that differ from the formation fluid. The presence of the invaded zone will affect the pressure transients measured by a formation tester.

In this paper, a model that includes an invaded zone is presented together with an analysis of its effect at each of the probes of a multiple probe formation tester. The results show that the properties of the invaded zone dominate the pressure transient measured at the sink probe, strongly influence the transient at the horizontal probe, and only modestly affect the vertical probe transient. A suggested modification to the current interpretation procedure (which does not consider the invaded zone) for determining the horizontal and vertical mobility is also presented. The application of this modified procedure is discussed using a model example.
Monitoring Compaction and Compressibility Changes in Offshore Chalk Reservoirs
Authors: Dean Graham , Hardy Robert , Eltvik Petter
Published: December 2007

Compressibility of offshore reservoirs can result in platform subsidence and a compaction drive mechanism for oil extraction. Permanent downhole pressure gauges can be used to monitor compressibility by measuring reservoir pressure changes caused by the sea tide.
Pseudofunctions and Extended Dietz Theory for Gravity-Segregated Displacement in Stratified Reservoirs
Authors: Ingsøy Pål , Gauchet Renaud , Lake Larry W.
Published: December 2007

This paper develops a new vertical equilibrium (VE) theory that accounts for gravity-segregated displacement in stratified reservoirs and is expressed either in terms of pseudofunctions or as an extended Dietz model. The theory includes reservoir stratification and capillary effects. An example calculation based on field data compares favorably with the more general numerical simulation.
Injecting Polyacrylamide Into Gulf Coast Sands: The White Castle Q Sand Polymer-Injectivity Test
Authors: Shahin G. T. , Thigpen D. R.
Published: December 2007

A polymer-injectivity test designed to control mobility in cosurfactant-enhanced alkaline flooding was performed in the Q sand of the White Castle field, LA. Analysis of test data indicates that a polymer bank with an average viscosity of 4 cp was propagated as far as 90 ft into the reservoir with no measurable sign of degradation. It is estimated from pilot and laboratory data that injection of 500 ppm polyacrylamide through perforations at a rate of at least 32 B-D/in.2 of perforation into gulf coast sands is feasible. Monitoring of backproduced reservoir samples indicates that, to date, no detectable change in viscosity has occurred over a 2-year period.
A Type-Curve Approach to Analyzing Two-Well Tracer Tests
Authors: Datta-Gupta Akhil , Lake L. W. , Pope G. A. , King M. J.
Published: December 2007

The traditional approach to analyzing field tracer data generally involves a history-matching procedure that is time-consuming and frequently results in a nonunique solution. In this paper, we use theoretical frequency response functions to build type curves of "transfer function" and "phase spectrum" that have a dimensionless heterogeneity index as a parameter to characterize a stochastic permeability field. The transfer function contains information regarding the amplitude-attenuating characteristics of the heterogeneous medium, and the phase spectrum provides information about the spacing between the frequency components of the input and output tracer pulses. In a manner analogous to type-curve matching for well testing, we can analyze field tracer history by comparing the theoretical and field-observed transfer function and phase spectrum. This analysis leads to an estimate of the heterogeneity index and PV. We demonstrate the technique by analyzing field tracer data from the Big Muddy field, WY, and compare the use of parameters obtained in scaling up. Results show very good agreement with the field data.
Scale Consistency From Cores to Geologic Description
Authors: Damsleth Eivind , Tjølsen C. B.
Published: December 2007

This paper describes a technique for conditioning stochastic simulation of permeability on a geologic description grid to the observed core-plug measurements. The technique handles the transition from core-plug to reservoir-description scale correctly and consistently, provided that some model assumptions are fulfilled. A North Sea case study is included for illustration.
Critical Evaluation and Processing of Data Before Pressure-Transient Analysis
Authors: Mattar Louis
Published: December 2007

With the common use of highly sensitive electronic pressure recorders and the widespread use of reservoir characterization by type-curve pressure-derivative techniques, preprocessing data has now become an important prerequisite to pressure-transient analysis. In almost all cases during a well test, the electronic pressure recorders measure a multitude of effects other than the intended reservoir pressure transients. For example, multiphase, geotidal, microseismic, changing liquid levels, recorder drift, recorder plugging, etc. can mask the reservoir transient. If not properly identified, these effects could easily be misinterpreted as reservoir characteristics, such as pressure depletion, boundaries, or dual porosity. The preprocessing of the digital data, starting with the comparison of pressures from multiple recorders and ending with data filtration to remove the noise associated with the signal, is a significant component of well-test interpretation and is a prerequisite to pressure-transient analysis.

From experience with thousands of well tests, we have chosen several examples to illustrate the need for preprocessing the data. The observed pressures must be corrected to remove the nonreservoir effects before pressure-transient analysis is attempted. Often, diagnosis of the observed data can only be done with the help of information other than the pressure trace.
A New, Fast, Accurate Pressure-Decay Probe Permeameter
Authors: Jones Stanley C.
Published: December 2007

The theory, design, and operation of a new probe permeameter based on a pressure-decay technique are discussed. Its useful range is from 0.001 to 30,000 md. Measurement time varies from ≈2 to 35 seconds. Slip-corrected (Klinkenberg) and conventional gas permeabilities, both of which are free from inertial flow-resistance effects, and measurement-position coordinates are obtained automatically. Computer-stored data facilitate generation of permeability "profiles" (permeability/depth logs), permeability contour plots, or "calibration" of wireline logs that imply permeability.
Fundamentals of Shale Stabilization: Water Transport Through Shales
Authors: Ballard Tracey J. , Beare Steve P. , Lawless Tom A.
Published: December 2007

One area where water-based muds need improved performance is in shale inhibition. However, before existing mud systems can be improved, the mechanisms by which water invades shales and how present-day inhibitive additives operate must be fully understood. An experimental technique has been developed that uses radioactive tracers to monitor the progress of water and selected dissolved ions through a shale core plug. By varying experimental parameters, such as water composition and applied pressure drop, the dominant mechanisms by which water is transported through shales have been identified. Under conditions of zero applied pressure, diffusion processes control water and ion movement through shales. Concentration gradients are the driving force for mass transfer of ionic species through shales. We observed no evidence to indicate that osmosis caused mass transfer of water. Applied pressure caused an increase in water and ion transport rates. Above a threshold pressure, water and dissolved ions travel at the same rate irrespective of the ion concentration.
Scale Control in the South Brae Field
Authors: Hardy J. A. , Barthorpe R. T. , Plummer M. A. , Rhudy J. S.
Published: December 2007

Severe scaling conditions exist in South Brae because of the high barium content of formation water and low pH downhole. Formation water is also susceptible to calcium carbonate scaling. This paper presents experiences with scale control on topsides and down-hole during field development. Topsides control has been achieved at the expense of high dose rates and secondary effects on produced-water quality. A sulfonate-based inhibitor was developed and applied for downhole control of BaSO4. This paper presents the benefits achieved by the use of desulfated seawater to minimize the BaSO4 potential and describes the methods developed to control calcium carbonate scale.
Effect of Mixing Energy Levels During Batch Mixing of Cement Slurries
Authors: Hibbert A. P. , Kellingray D. J. , Vidick Benoit
Published: December 2007

The properties of batch-mixed slurries prepared in a series of yard tests using full-scale equipment are compared with laboratory tests on the same materials. Dramatic differences have been observed between conventional laboratory tests and field scale properties.

By splitting the batch-mixing process into distinct steps, a laboratory method is tested against the observed differences.

It is shown that mixing energy is an important parameter in slurry design and that energy levels substantially above the conventional API laboratory mixing energy may degrade slurry properties such as pumping time.
Modeling Off-Center Wells in Reservoir Simulation
Authors: Su Ho-Jeen
Published: December 2007

In conventional reservoir simulation, wells are assumed to be at cell centers. Thus, the fluid flow pattern around an off-center well is represented incorrectly. This is especially true for large fieldwide models, which are gridded by very coarse blocks resulting in numerous off-center wells. This paper describes a new, rigorous method to model single or multiple off-center wells in a gridblock. Fluids can be drawn directly from the four closest neighboring cells into an off-center producer. Well location is honored exactly. With the new method, the calculated wellblock pressure can be interpreted at cell center rather than away from cell center as in the conventional approach. The new method is formulated fully implicitly, and although it adds more nonzero elements to the Jacobian matrix, its dimension remains unchanged. Therefore, implementation of this method is not difficult and the increase in computing costs is minimal. This work has been validated by fine-grid simulation results. Several single- and multiple-phase test cases are presented. We show that the new method can improve the accuracy of numerical results for large fieldwide models.
Induction Log Analysis of Thinly Laminated Sand/Shale Formation
Authors: Hagiwara Teruhiko
Published: December 2007

We examine induction log responses to a thinly laminated sand/shale sequence in a deviated borehole for arbitrary deviation (or dip) angle and sand/shale composition. We found that the induction log responses in a thinly laminated sand/shale sequence are the same as they would be if the tool is placed in a homogeneous but anisotropic formation with the horizontal and vertical conductivities given respectively by the parallel and the series conductivities of the sequence.

Conversely, a thinly laminated sand/shale sequence can be identified as an anisotropic formation by induction logs. We discuss three methods to identify an anisotropic formation using induction-type logs alone.
Forces on Curved Tubulars Caused By Fluid Flow
Authors: Mitchell R. F.
Published: December 2007

This paper examines the effects of fluid pressures and flowing fluid momentum on curved tubing, casing, or drillpipe in a wellbore. A general expression for fluid forces on curved tubing is developed. Special cases, such as the "fictitious force" used in tubing buckling analysis, are developed and explained in terms of actual physical behavior. New problems, such as the effect of tubing eccentricity on fluid forces and the effect of external flow on tubing buckling, are identified. Lateral forces developed in curved tubulars caused by fluid pressure can be much higher than expected, with significant impact on friction drag loads and pipe sticking.
Reservoir Permeability Estimation From Time-Lapse Log Data
Authors: Yao C. Y. , Holditch S. A.
Published: December 2007

This paper presents a method to estimate permeability using time-lapse log data. The reservoir permeability values are also obtained by history matching production data and analyzing core data. These permeability values are in agreement with the estimates derived from logs.

When a well is drilled, mud filtrate invades the formation around the borehole. The volume of mud-filtrate invasion is related to time, formation permeability, and other wellbore and formation parameters. As mud-filtrate invasion progresses, unique saturation profiles and, thus, unique profiles of resistivity and water saturation, are created in the formation surrounding the borehole. Therefore, the data from well logs change with time. By observing and analyzing the changes in log data vs. time, one can estimate formation permeability.
Slimhole Early Kick Detection by Real-Time Drilling Analysis
Authors: Swanson B. W. , Gardner A. G. , Brown N. P. , Murray P. J.
Published: December 2007

Early kick detection has been identified as being of primary importance in slimhole wellbores. Small annular volumes mean that, to maintain the integrity of the well, allowable kick volumes must be small. Gas influxes must therefore be detected and shut in rapidly. This paper describes an early kick-detection system developed for slimholes to detect and confirm the presence of an influx rapidly. This system has been run successfully on a number of slimhole operations.

The early kick-detection (EKD) system is based on real-time analysis of drilling data obtained directly from a comprehensive mud-logging system on the rig. The analysis technique compares predictions of mud flow out and standpipe pressure from a dynamic wellbore model with corresponding values from the rig. The predicted values are derived from a model driven in real time by rig data such as pump rate and pipe rotation rate. Kick detection is based on deviations between measured data and idealized model predictions.

The EKD system has been incorporated into an operational engineer-oriented graphical interface, which has provided easy access to the model for both input and output of data, and for the interpretation of results. This paper describes the design considerations and technology behind the EKD system and the engineering interface. The paper also presents examples of the system running in real time at a slimhole rig site.
Effects of Steam Quality and Injection Rate on Steamflood Performance
Authors: Hong K. C.
Published: December 2007

A comprehensive numerical simulation study showed that for a typical heavy-oil reservoir, steamflood performance improves monotonically with increases in steam quality and injection rate. Hence, for this reservoir, the optimum quality and injection rate are the highest values that were investigated. In general, however, optimum steam conditions depend on reservoir type and operating mode (e.g., line drive or pattern flood). For most situations, published "rule-of-thumb" steam conditions are not optimum. Therefore, we recommend that optimum steam conditions for a specific reservoir be determined through economic comparison of predicted oil recoveries for ranges of steam conditions, as demonstrated in this study.
Development of a New Cuttings-Transport Model for High-Angle Wellbores Including Horizontal Wells
Authors: Larsen T. I. , Pilehvari A. A. , Azar J. J.
Published: December 2007

This paper presents a new design model that will enable the drilling engineer to select the proper hydraulics for problem-free drilling in high-angle holes (from 55 to 90° from vertical). Empirical correlations have been developed after carrying out an extensive experimental study of cuttings transport in a 5-in. full-scale flowloop. The model predicts the required critical transport fluid velocity (CTFV), the average cuttings travel velocity (CTV), and the annular cuttings concentration under most given sets of drilling operating conditions.
A New MTV Computer Package for Hole-Cleaning Design and Analysis
Authors: Ford J. T. , Gao Erhu , Oyeneyin M. B. , Peden J. M. , Larrucia M. B. , Parker David
Published: December 2007

This paper describes a computer package that can be used to calculate the minimum transport velocity (MTV) required to ensure efficient hole cleaning during deviated drilling operations. The package was developed in the Dept. of Petroleum Engineering at Heriot-Watt U. It operates in a Windows environment and allows the user to do the following:

Define, from viscometer data, the rheological model (PowerLaw, Bingham Plastic, or Herschel-Bulkley) that best describes a particular drilling fluid. Model the drilling fluid velocity profile in a defined annular geometry. Predict the minimum circulation rate required to ensure efficient cuttings transport for a wide range of operational conditions.

The paper describes how the lift and drag forces on the cuttings have been determined and used in the development of the package. Case studies that demonstrate the functionality of the package are also presented.
Coiled Tubing Buckling Implication in Drilling and Completing Horizontal Wells
Authors: Wu Jiang , Juvkam-Wold Hans C.
Published: December 2007

This paper discusses coiled tubing buckling and load transmission when drilling and completing horizontal wells. Comprehensive analyses and new equations are presented to predict buckling of coiled tubing, "slack-off" weight transmission, actual bit weight or packer load, and maximum horizontal length. Coiled tubing "lockup" and yield due to buckling are also discussed. These equations can also be used for other coiled tubing operations, such as coiled tubing workover, coiled tubing well stimulation, and even for conventional joint-connected drill strings. Calculations based on the equations presented are also compared with the previous literature.
Adsorption Studies of Natural Gas Storage in Devonian Shales
Authors: Lu Xiao-Chun , Li Fan-Chang , Watson A. Ted
Published: December 2007

Significant amounts of natural gas exist as an adsorbed, or condensed, phase in Devonian shale formations and other unconventional gas resources. The amount of the adsorbed phase depends on the pressure and temperature. The Langmuir isotherm has been used to describe the pressure dependence. However, temperature dependence has not been explored. This is important to evaluate thermal stimulation as a recovery method and to extrapolate laboratory measurements to reservoir conditions. We investigate adsorption as a function of both pressure and temperature. We found that the effects of temperature are significant and that the Langmuir model does not describe adsorption adequately. We reconciled the data with bi-Langmuir models.
Application of Linear Programming to Reservoir Development Evaluations
Authors: Lo K. K. , Starley G. P. , Holden C. W.
Published: December 2007

A production forecasting model that uses linear programming concepts has been developed to generate composite forecasts from multiple streams produced through a common facility. The model treats petroleum processing as a linear optimization problem to maximize oil production under a set of independent constraints. The model represents production streams competing for limited facility capacity on a consistent basis. This approach allows resolution of production streams of varying character [GOR, gas/liquid ratio (GLR), or WOR] into a composite rate forecast while facility capacity is used optimally. In particular, the model may be used to forecast production of several unrelated fields producing through a common facility. The model was applied to forecast production for three Alaska North Slope reservoirs (Kuparuk, Lisbume, and Point McIntyre) for development and facility-expansion evaluations.
Field Trial Results of Annular Pressure Behavior in a High-Pressure/High-Temperature Well
Authors: Oudeman P. , Bacarreza L. J.
Published: December 2007

The problem of annular pressure buildup due to heating of the strings by the (hot) well effluent, will typically be of concern in the design of casing strings for high-pressure/high-temperature (HP/HT) sub-sea wells. In such completions bleeding off the pressure through the wellhead, as done routinely with surface wells, is not possible.

Theoretical studies indicated that, potentially, extreme pressures could develop in confined sealed annuli of subsea completions, posing a severe threat to well integrity. To investigate the effect under realistic conditions, Shell Expro (UK) ran battery operated gauges in the 9 5/8 in. × 13 5/8 in. annulus of an offshore HP/HT well, to record pressure and temperature changes during drilling, cementing and production testing.

This paper presents the results of these tests and a general model for pressure buildup in unconfined sealed annuli to correlate the field data. Since only pressure and temperature measurements were available certain assumptions had to be made with respect to, e.g., formation response to pressure buildup, in situ liquid properties, etc. Although these assumptions could be debatable, it is hoped that by publishing and sharing ideas, a better understanding of annular pressure behavior can be developed.
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

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

This 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

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

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

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

Compositional 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

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.