bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Model for Two-Phase Oil/Water Flow: Production Log Interpretation and Tubular Calculations
Authors: Hasan A. Rashid , Kabir C. Shah
Published: December 2007

This work presents the results of an experimental and theoretical investigation of two-phase oil/water flow behavior in vertical pipes. Bubbly flow is observed to be the predominant flow pattern, although at high flow rates, slug flow was noted. The proposed method, developed from the drift-flux principle, is validated by our experimental data and those obtained from other sources. Limited study indicates the proposed method's superiority over others available in the literature. This work further shows the error involved when oil/water flow behavior is predicted by homogeneous, gas/liquid, and constant-slip models. Application of the model for production log interpretation is also documented.
Recent Performance of the Dual-Resistivity MWD Tool
Authors: Grupping Theo I. F. , Wagstaff J. D.
Published: December 2007

The dual-resistivity MWD tool uses sections of the drill collar as electrodes and provides two independent resistivity measurements: a principal well-focused lateral measurement of the current flowing radially from a defined segment of the drill collar and a secondary axial or bit measurement of the current flowing from a defined portion of the lower bottomhole assembly (BHA). In oil-based muds, a single (bit) measurement is made of the current flowing to the formation through the drill bit.
Optimal Input Design—A Method for Enhancing Data Quality
Authors: Foss Bjarne A.
Published: December 2007

This paper presents a generic design method for specifying the flow sequence from one or multiple wells. The method seeks to maximize the information content in collected data. It is shown how the information content, defined in precise terms, is a function of the flow sequence. Three examples demonstrate how the proposed method improves data quality, and guidelines for practical use are presented.
Physics and Modeling of Thermal Flow and Soil Mechanics in Unconsolidated Porous Media
Authors: Settari Antonin
Published: December 2007

This paper describes a new formulation of nonlinear soil mechanics and multiphase thermal flow. The nonlinearities of the soil behavior and their interactions with fluid flow causing shear failure of the soil are the dominant features of the process. The numerical formulation of the coupled flow/stress solution model includes nonlinear compressibility and flow properties as functions of pressure, stress, and temperature; nonlinear, incremental, thermal poroelastic stress analysis; and shear or tensile failure and its effects on transport properties, porosity, and stress. An efficient sequential numerical scheme was developed. It is mass conservative and applicable to external coupling of existing simulators. The 1D examples show some startling new features of reservoir mechanics in unconsolidated media.
Effect of the Presence of Oil on Foam Performance: A Field Simulation Study
Authors: Law D. H. -S. , Yang Z. -M. , Stone T. W.
Published: December 2007

This paper describes a field-scale sensitivity study of the effect of the presence of oil on foam performance in a steam-foam-drive process. The 2D field-scale simulation was based on a field pilot in the Karamay formation in Xin-Jiang, China. Numerical results showed that the detrimental effect of oil on the foam performance in field operations is significant. The success of a steam-foam process depended mainly on the ability of the foam to divert steam from the depleted zone.
Calculating the Effective Permeability Tensor of a Gridblock
Authors: Kasap Ekrem , Lake Larry W.
Published: December 2007

We propose an analytical method to calculate effective block permeabilities as a full tensor based on the geometry, block size, full local tensorial permeabilities, and the geology within the block. The method was validated with a finite-element numerical simulator and was applied to a simulation of flow through an outcrop of the eolian Page sandstone. Results show that the relative positions of the main geologic features and the ratio between the grain-flow and wind-ripple permeabilities are more important than bounding surfaces and dispersion in determining flow behavior.
Volumetric Treatment Efficiencies of Some Commercial Clay Stabilizers
Authors: Hesterberg Dean , Reed M. G.
Published: December 2007

Volumetric treatment efficiencies of three commercially available clay-stabilizer treatments were evaluated in the laboratory. Rock volume treated per unit chemical volume varied up to three-fold between stabilizers and depended on sandstone mineral properties. The results are valuable for designing clay-stabilizer treatments and maximizing stabilizer cost-effectiveness.
A Bayesian Methodology for Estimating Relative Permeability Curves
Authors: Yang P. -H. , Watson A. T.
Published: December 2007

Among the various properties important for simulating reservoir behavior, relative permeability curves may be the most poorly determined by current methods. This paper presents a method for obtaining improved estimates of relative permeability curves. A Bayesian-type performance index is used to incorporate prior estimates of relative permeability curves into an automatic history-matching algorithm. Estimates obtained with the method are consistent with the reservoir production and yet conform to the prior estimates.
A Practical Equation of State
Authors: Ahmed Tarek
Published: December 2007

To use the Peng-Robinson equation of state (PREOS) to predict the phase and volumetric behavior of hydrocarbon mixtures, one needs to know the critical pressure, pc, critical temperature, Tc, and acentric factor, ω, for each component present in the mixture. For pure compounds, the required properties are well-defined, but nearly all naturally occurring gas and crude oil fluids contain some heavy fractions that are not well-defined and are not mixtures of discretely identified components. These heavy fractions often are lumped and called the "plus fraction" (e.g., C7+ fraction). Adequately characterizing these undefined plus fractions in terms of their critical properties and acentric factors has long been a problem. Changing the characterization of the plus fraction can have a significant effect on the volumetric and phase behavior of a mixture predicted by the PREOS. This limitation of the PREOS results from an improper procedure of determining coefficients a, b, and α for the plus fraction and for hydrocarbon components with critical temperatures less than the system temperature (i.e., methane and nitrogen). This paper presents a practical approach to calculating the parameters of the PREOS for the undefined fractions to improve the predictive capability of the equation. Use of the modified equation is illustrated by matching laboratory data on several crude oil and gas-condensate systems.
Rate Performance of a Layered Reservoir With Unsteady-State Interlayer Crossflow
Authors: Olarewaju J. S. , Lee W. J.
Published: December 2007

This paper presents an analytical solution for rate performance of a well intercepting a bounded two-layer reservoir. The solution is for modeling two-layer reservoirs with or without crossflow, with each layer having different layer skins and drainage radii. We present the effects of partial completion and of different layer skins and drainage radii on the rate behavior in layered reservoirs.
Case Studies off the Bending Vibration and Whirling Motion off Drill Collars
Authors: Vandiver J. Kim , Nicholson James W. , Shyu Rong-Juin
Published: December 2007

This paper describes two principal sources of bottomhole-assembly (BHA) bending vibration: (1) drill-collar whirling and (2) linear coupling between weight-on-bit (WOB) fluctuations and bending vibration of an initially curved BHA. It also evaluates the consequences of bending vibration in terms of drill-collar wear and connection fatigue. Equations are given for forward and backward whirl rate and for tangential velocity at the borehole wall. Downhole measurements of bending moment are used to detect and to identify bending-vibration events, and data taken with a downhole vibration-measurement system are used to illustrate cases of linearly coupled bending vibration, forward and backward whirl, and bit bounce.
Improvement of Drill-Collar Fatigue Property by Last-Engaged-Thread-Height Reduction of Pin
Authors: Tsukano Yasushi , Nishi ShunJi , Nishida Shin-Ichi , Ueno Masakatsu
Published: December 2007

This paper describes a method to increase the fatigue life of a drill collar by reducing the height of a pin's last-engaged thread (LET). The effectiveness of the method was verified with finite-element analysis (FEA), and the results were evaluated by full-size fatigue tests. Also, the practicality of the redesigned connection was confirmed through overmakeup, make-and-break, and full-size tensile testing.
Hydraulic Fracturing Slurry Transport in Horizontal Pipes
Authors: Shah Subhash N. , Lord David L.
Published: December 2007

Horizontal-well activity has increased throughout the industry in the past few years. To design a successful hydraulic fracturing treatment for horizontal wells, accurate information on the transport properties of slurry in horizontal pipe is required. Limited information exists that can be used to estimate critical deposition and resuspension velocities when proppants are transported in horizontal wells with non-Newtonian fracturing gels.

This paper presents a study of transport properties of various hydraulic fracturing slurries in horizontal pipes. Flow data are gathered in three transparent horizontal pipes with different diameters. Linear and crosslinked fracturing gels were studied, and the effects of variables—e.g., pipe size; polymer-gelling-agent concentration; fluid rheological properties; crosslinking effects; proppant size, density, and concentrations; fluid density; and slurry pump rate—on critical deposition and resuspension velocities were investigated. Also, equations to estimate the critical deposition and resuspension velocities of fracturing gels are provided.
Laboratory and Field Evaluations of Clad Christmas Tree Equipment
Authors: Sisak W. J. , Gordon J. R.
Published: December 2007

A methodology is presented for evaluating the corrosion resistance of clad equipment in sour environments. This paper describes the laboratory and field test programs used to evaluate the suitability for sour service of gate valves clad with Alloy UNS N06625 by weld overlay and by hot, isostatic pressing (HIP). The laboratory tests used to evaluate corrosion and cracking resistance of the clads are reviewed. Experience with actual field installations of both types of clad valves is presented, and the test/inspection methods used to evaluate the equipment during and after the service period are discussed. Finally, laboratory and field results are compared to highlight key findings related to the clad valve bodies and to the trim components.
Comparison of Laboratory and In-Situ Measurements of Waterflood Residual Oil Saturations for the Cormorant Field
Authors: van Poelgeest Frits , Niko Helmut , Medwld Andrew R.
Published: December 2007

Shell Expro and Koninklijke/Shell E&P Laboratorium (KSEPL) have been engaged in a multidisciplinary effort to deter mine the waterflood residual oil saturation (ROS) in two principal reservoirs of the Cormorant oil field in the U.K. sector of the North Sea. Data acquisition included special coring and testing. The study, which involved new reservoir-engineering and petrophysical tech niques, was aimed at establishing consistent ROS values.

Reservoir-engineering work centered on reservoir-condition corefloods in the relative-permeability-at-reservoir-conditions (REPARC) apparatus, in which restoration of representative wettability conditions was attempted with the aging technique. Aging results in a con sistent reduction of water-wetness of all core samples. The study indicated that ROS values obtained on aged cores at water throughputs of at least 5 PV represented reservoir conditions. The petrophysical part of the study involved ROS estimation from sponge-core analy sis and log evaluation.
A Newly Developed Chromium(lll) Gel Technology
Authors: Sydansk Robert D.
Published: December 2007

Laboratory testing of a recently developed chromium(III) [Cr(III)] gel technology is reported. The gels can be used in conjunction with a number of oilfield treatments. The single-fluid acrylamide-polymer/Cr(III)-carboxylate aqueous gels are formed by crosslinking acrylamide polymer with a Cr(III)-carboxylate-complex crosslinking agent. Representative gel compositions and associated gel properties are discussed.
An Experimental Study of the Annulus Pressure Drop in a Simulated Air-Drilling Operation
Authors: Supon S. B. , Adewuml M. A.
Published: December 2007

A comprehensive experimental wellbore model was built to simulate the multiphase flow of compressed air and sand that occurs in an air-drilling process. The model was designed to control the air volumetric flow rate and sand mass flow rate through a transparent annulus. The model also permitted observation of the sand and air in the annulus and allowed measurement of the pressure drop across the annulus. An empirical equation was developed for the minimum annulus pressure drop as a function of the sand mass flow rate through the system, the optimum annulus air velocity, the weight fraction of coarse sand particles entering the annulus, the weight fraction of coarse sand particles in the annulus, and solids loading in the annulus. The experimental results were compared with annulus pressures predicted by a semiempirical model of the air-drilling process developed by Angel. Angel's model failed to predict the observed minimum annulus pressure drops. In addition, the experimental results indicated that an annulus air velocity lower than the value assumed by Angel's model may be required.
New System Provides Continuous Quantitative Analysis of Gas Concentration in the Mud During Drilling
Authors: Roberts G. L. , Kelessidls V. C. , Williams J. M.
Published: December 2007

Continuous monitoring of hydrocarbon gases in drilling fluids at the surface is essential for identification of prospective reservoir zones as well as for safety. This paper describes a new gas-analysis system that determines the total amount of gas in the mud below the bell nipple. The system is continuous, consistent, and fully quantitative (unlike a gas trap) but not labor-intensive (like a steam still). It also recovers and analyzes gas liberated into the air at the bell nipple, which test results have shown to be almost 50% of the total gas in the mud below the bell nipple.
Permeability Reduction Induced by a Nonhydrostatic Stress Field
Authors: Holt Rune M.
Published: December 2007

Stress-dependent permeability was measured in a high-porosity/high-permeability sandstone with mechanical and fluid-flow parameters similar to those found in typical North Sea reservoirs, particularly the little-investigated effect of triaxial stress configurations. Hydrostatic loading from atmospheric conditions to stress levels comparable to those found in situ causes a slight permeability reduction. When the applied stress is nonhydrostatic, the permeability decrease is more pronounced. In particular, as failure is approached in triaxial loading or unloading, the permeability may be significantly reduced (in some cases to < 10% of its initial value). This paper discusses the consequences of these results for interpretation of standard permeability measurements. An example quantifies the formation damage (skin) induced by the near-wellbore stress field.
Computer Simulation off Cased-Hole Density Logging
Authors: Jacobson Larry A. , Fu Chu-Chiu
Published: December 2007

The response of a density tool in the presence of casing is assessed by means of mathematical modeling. Response variations for changes in cement thickness and density, casing thickness, and tool standoff as a function of formation density and source energy are presented.
Modeling Low Interfacial Tension Hydrocarbon Phenomena in Porous Media
Authors: Gray Jane D. , Dawe Richard A.
Published: December 2007

This paper investigates pore-scale mechanisms of both wetting and nonwetting phase dropout and flow at low interfacial tensions (IFT's) (approximately 0.1 to < 0.01 mN/m) by use of transparent 2D micromodels with a partially miscible binary fluid system. Quantification is possible with this liquid system because it has uniquely defined physical properties at any given temperature. Phase dropout and flow behavior at phase saturations of < 10% are emphasized. Wettability effects are dominant, but the fluid/fluid interactions change as the IFT drops. The ramifications for the relative permeability curves are discussed.
Annular Packer Fluids for Paraffin Control: Model Study and Successful Field Application
Authors: Ashford James D. , Blount Curtis G. , Marcou John A. , Ralph Joseph M. , Skaalure Eric W.
Published: December 2007

This paper covers the evolution, full-scale model study, and field application of gelled packer fluids for paraffin control in naturally flowing wells. Field application of these insulating packer fluids has resulted in significant increases in the flowing tubing temperature in the seven wells treated to date. The temperature increases from gelled-packer-fluid application alone have eliminated paraffin problems previously controlled with repeated hot-oil treatments. Before this application, chemical inhibition attempts were unsuccessful.

The gelled fluid currently used is based on a phosphate ester and sodium aluminate reaction that produces an aluminum phosphate ester association polymer. The gellant is commonly used in oil-based fracturing fluids.
Effect of High Silica Content on Scale Deposition and Pipe-Wall Loss in Oilfield Steam Generators
Authors: Khatib Z. I. , Olson E. E. , Place M. C.
Published: December 2007

Studies were conducted on site in the Coalinga, Belridge, and Midway Sunset fields in California to research the cause of metal losses detected in the radiant section return bends and immediate piping downstream from the steam generators. Surveillance of silica content in the influent and effluent streams of the selected steam generators and the results of X-ray inspection of bends, elbows, welds, and pipings indicated that (1) a correlation is likely to exist between the silica and bicarbonate concentration in the feed-water and the silicate scale buildup, and incident rate of wall loss and (2) the cause of wall loss/pipe failures is a combination of corrosion and erosion mechanisms accelerated at higher steam qualities.
Tip Screenout Fracturing Applied to the Ravenspurn South Gas Field Development
Authors: Martins J. P. , Leung K. H. , Jackson M. R. , Stewart D. R. , Carr A. H.
Published: December 2007

Tip screenout (TSO) fracturing is a means of creating greater propped fracture widths and hence fracture conductivities than can be achieved by conventional fracture treatments. This allows more cost-effective stimulations of higher-permeability reservoirs, especially where non-Darcy pressure losses are significant. This paper presents a procedure to design TSO schedules and reviews field results from the Ravenspurn South gas field, which was developed between 1988 and 1989. Evidence is provided to support the view that TSO pressure responses are indeed the result of processes occurring close to the fracture tip, rather than slurry-enhanced viscosity effects along the fracture length.
Application of Alkylnaphthalene Absorption Oil as a Sulfur Solvent in Sour-Gas Wells
Authors: Wilken Gerdt
Published: December 2007

Elemental sulfur is soluble in sour gas and often precipitates in sour-gas wells during production. Prevention of sulfur deposition in the production equipment requires the application of a sulfur solvent. An aqueous alkaline solvent is inadequate at increasing formation-water inflow resulting in severe carbonate precipitation. The new solvent is based on a mixture of alkylnaphthalenes diluted in a mineral oil. Both can combine physically with the precipitated sulfur. The performance of the solvent during circulation, its regeneration, and its behavior in corrosion inhibition is outlined. Application of this solvent improved the production of the treated sour-gas wells.
An Implicit Numerical Model for the Closed-Chamber Test
Authors: Mfonfu G. B. S. , Grader A. S.
Published: December 2007

An implicit Lagrangean model is presented for the closed-chamber test (CCT). Pressure drops from 5, 000 to 50 psi are not uncommon during a CCT. High fluid velocities near the wellbore under high pressure gradients may lead to non-Darcy flow in the reservoir. The wellbore and the reservoir are modeled by the scalar-conservation laws of momentum and continuity that describe the physical processes—variable celerity, physical dissipation, and momentum. Rate and pressure are obtained simultaneously for the entire reservoir/wellbore system. The Lagrangean formulation permits use of the appropriate equation of state (EOS) in a given wellbore cell. Solution is by a versatile implicit numerical scheme that allows control of numerical dissipation. The automatic regridding is based on the physics of the problem. The reservoir model shows excellent agreement with the finite radial-source solution in porous media. Attributes of the model include the effects of an initial fluid column, sand failure, and a time-dependent skin. The results are in good agreement with two actual field tests from offshore Gulf of Mexico, and the deduction of transmissibility is straightforward.
Field Performance of a Hydrodynamically Lubricated Bearing Seal for Rock Bits
Authors: Langford J. W. , Kalsi M. S.
Published: December 2007

This paper presents field performance results for a new type of bearing seal for rock bits. The new seal design is found to be effective in significantly reducing abrasive wear at the sealing interface by virtue of its unique geometry that simultaneously introduces a hydrodynamic lubricant film and prevents the ingress of abrasives at the sealing interface. This has resulted in longer seal life and overall improvements in the rock-bit performances by a significant reduction in early seal failures.
Application of Bicenter Bits in Well-Deepening Operations
Authors: Myhre Kent
Published: December 2007

This paper describes the design and operational evolution of bicenter fixed cutter bits used to drill and to underream below existing casing for a well-deepening program in south Texas. These bits were required to pass through the casing ID and to drill a hole diameter large enough to allow adequate annular clearance for cementing a liner. The traditional method for deepening these wells required several roller-cone bits and hole openers. Use of bicenter bits decreased the cost of the well deepening by eliminating bit and underreamer trips and increasing rate of penetration (ROP).
Field Application of the All-Oil Drilling-Fluid Concept
Authors: Fraser L. J.
Published: December 2007

Until recently, a lack of suitable technology limited application of the all-oil or water-free drilling-fluid concept to coring operations. Stable rheological and filtration properties have been difficult to achieve. High levels of solid additives have been used, and this has stifled the rheological performance. The design, development, and field application of a unique, low-solids, oil-based fluid, which is prepared without a water or brine phase, is described.
A New Automated Tool-Joint Inspection System To Reduce Drillstring Failures
Authors: McPherson Bruce , Dutton Paul , Dale B. A. , Chilton T. S.
Published: December 2007

Drillstring connection failures continue to be a costly problem for the oil industry. To reduce the occurrence of these failures, operators and drilling contractors typically specify periodic nondestructive inspections to remove damaged tubulars from service. Conventional inspections generally involve the use of magnetic particles, and performance is highly dependent on human factors, which can result in errors by inspectors. This paper describes the development of a new automated tool-joint inspection system (ATIS) based on electromagnetic-flux-leakage principles to detect common service-induced flaws reliably, such as fatigue cracks, stretched threads, and mechanical damage. ATIS is capable of inspecting common connections on drillpipe and drill collars in the pipeyard and at the drillsite. Laboratory testing and field experience show that ATIS limits the probability of human error and thus reduces the occur rence of costly drillstring failures.
Distinct Applications of MWD, Weight on Bit, and Torque
Authors: Belaskie J. P. , Dunn M. D. , Choo D. K.
Published: December 2007

Recent enhancements to measurement-while-drilling (MWD) tools have increased drilling efficiency in directional wells on the North Slope of Alaska. With information provided by downhole weight on bit (WOB) and torque sensors, more timely and accurate decisions have been made, resulting in lower costs per foot. Specific applications of this technology include bit optimization, directional feedback, and drillstring-friction analysis. This paper discusses actual cases where the use of data from these downhole sensors has improved drilling performance. This information will benefit those interested in optimizing polycrystalline-diamond-compact (PDC) and rollercone bit runs, improving directional-drilling assembly predictability and performance, minimizing surface torques, and planning high-departure wells.
In-Situ Saturation Measurements Improve Analysis and Interpretation of Laboratory Miscible and Immiscible Displacement Processes
Authors: Berry J. F. , Little A. J. H. , Salt H. J.
Published: December 2007

A laboratory evaluation of miscible and immiscible oil recovery processes was performed on a sandstone core composite containing viscous crude oil. Because conventional effluent data cannot clearly identify the evolution of transient saturation distributions, in-situ saturation monitoring was used to provide distributed saturation histories. The data obtained suggest that phase behavior is a major factor determining the amount and distribution of residual oil.
Network Analysis of Capillary and Trapping Behavior of Foams in Porous Media
Authors: Flumerfelt R. W. , Chen H-L. , Ruengphrathuengsuka Wlrogana , Hsu W-F. , Priedltis John
Published: December 2007

A 1D network model is used to describe capillary pressure and flow-fraction pressure behavior of dispersed phase systems (foams) in porous media. The presence of internal liquid lamellae between bubbles in displaced trains gives rise to significantly higher capillary and flow-fraction pressures compared to nondispersed phase systems (i.e., conventional gas/liquid systems, no surfactant). Low mobilities of foam systems are attributed to reductions in the mobilized gas fraction.
In-Situ Stress Evaluation in the McElroy Field, West Texas
Authors: Avasthi J. M. , Nolen-Hoeksema R. C. , El Rabaa A. W. M.
Published: December 2007

This paper discusses an in-situ-stress evaluation program conducted in the McElroy field in preparation for waterflood realignment. Microfracturing and borehole logging results indicated that the maximum horizontal stress orientation was north-northwest, west-northwest, and north-northwest in the upper, middle, and lower payzone intervals, respectively. Microfracturing proved to be the most reliable and cost-effective technique for in-situ stress evaluation in this heterogeneous reservoir.
Impact of Dispersion on Gel Placement for Profile Control
Authors: Seright R. S.
Published: December 2007

A key issue in gel technology is how to place gels in thief zones without damaging oil-productive zones. This study explores the influence of diffusion, dispersion, and viscous fingering during placement of gels to modify injection profiles. These phenomena usually will not eliminate the need for zone isolation during gel placement in unfractured injection wells. During gel placement in parallel laboratory corefloods, diffusion and dispersion can cause one to conclude erroneously that zone isolation is not needed in field applications. Gel treatments are more likely to improve sweep efficiency in wells where fractures are the source of the channeling problem.
Application of Fiberglass Sucker Rods
Authors: Gibbs S. G.
Published: December 2007

Fiberglass sucker rods are assuming a place in artificial-lift technology. This paper briefly describes the manufacturing process and gives some design and operational hints for practical applications. It also describes some mathematical modeling modifications needed for fiberglass wave-equation design programs.
Displacement Characteristics of Nitrogen vs. Methane Flooding in Volatile-Oil Reservoirs
Authors: Boersma D. M. , Hagoort Jacques
Published: December 2007

This paper presents a comparative study, based on analysis of phase behavior, compositional reservoir simulations, and slim-tube experiments, of displacement characteristics of nitrogen and methane flooding into a volatile-oil reservoir. Results show that nitrogen has the same minimum multiple-contact-miscibility (MCM) pressure as methane, provided the oil contains enough methane. When dispersion occurs, the recovery efficiency for methane is better than that for nitrogen injection. The difference between nitrogen and methane injection above the minimum miscibility pressure (MMP) decreases with increasing Peclet number values.
Gel Placement in Production Wells
Authors: Liang Jenn-Tai , Lee R. L. , Seright R. S.
Published: December 2007

Straightforward applications of fractional-flow theory and material-balance calculations demonstrate that, if zones are not isolated during gel placement in production wells, gelant can penetrate significantly into all open zones, not just those with high water saturations. Unless oil saturations in the oil-productive zones are extremely high, oil productivity will be damaged even if the gel reduces water permeability without affecting oil permeability. Also, in field applications, capillary pressure will not prevent gelant penetration into oil-productive zones. An explanation is provided for the occurrence of successful applications of gels in fractured wells produced by bottomwater drive. With the right properties, gels could significantly increase the critical rate for water influx in fractured wells.
Application of the Du-Guo and SRK Equations of State To Predict the Phase Behavior of Chinese Reservoir Fluids
Authors: Guo Tian-Min , Du Lian-Gui , Pedersen K. S. , Fredenslund Aage
Published: December 2007

The Du-Guo three-parameter cubic and the Soave-Redlich-Kwong (SRK) equations of state (EOS) modified as suggested by Peneloux and Freze were used to predict the phase behavior of nine Chinese reservoir fluids. The C7+ fractions were characterized as suggested by Pedersen et al. or by use of a characterization procedure suggested by Du and Guo. This paper also presents experimental and calculated results for the enthalpy of crude oil fractions. It is found that both EOS can accurately predict the phase behavior and phase properties of the Chinese reservoir fluids.
Horizontal Core Acquisition and Orientation for Formation Evaluation
Authors: Skopec R. A. , Mann M. M. , Jeffers Doug , Grier S. P.
Published: December 2007

The increase in horizontal drilling activity has produced a need for improved coring technology. The development of a reliable horizontal (medium-radius) coring and orientation system has greatly improved the acquisition of information necessary for formation evaluation and reservoir engineering. This paper describes newly developed hardware and methods for obtaining horizontal core sections.
Solubility and Displacement Behavior of a Viscous Crude With CO2 and Hydrocarbon Gases
Authors: DeRuiter R. A. , Nash L. J. , Singletary M. S.
Published: December 2007

The West Sak reservoir on the Alaskan North Slope contains an estimated 15 to 25 billion bbl of low-temperature, viscous crude. The reservoir has promising development potential by means of a gas injection process. An experimental study of the solubility and displacement behavior of West Sak oil with CO2 and hydrocarbon gases shows simple black-oil to complex, multiphase equilibrium behaviors.
Pressure-Transient Model for a Vertically Fractured Well in a Fractal Reservoir
Authors: Beier Richard A.
Published: December 2007

In many cases, field pressure-transient data are matched with a homogeneous reservoir model to obtain effective reservoir properties for a heterogeneous reservoir. This paper presents field data and a model that demonstrate that this approach does not always work. As an alternative, a model is developed for a well with a vertical fracture in a reservoir with a fractal structure.
Improved Oxygen-Activation Method for Determining Water Flow Behind Casing
Authors: McKeon D. C. , Scott H. D. , Olesen J-R. , Patton G. L. , Mitchell R. J.
Published: December 2007

Impulse activation is a new oxygen-activation technique developed to detect vertical water flow and to provide a quantitative measure of water flow velocity and flow rate. Row-loop measurements made over a wide range of water velocities are in good agreement with theoretical predictions. Measurements of up- and downward channel flow were made at the U.S. Environmental Protection Agency (EPA) leak test well in Ada, OK, to demonstrate the technique in a controlled environment and to confirm that EPA requirements have been met. A major advantage of this method over previous procedures is that a measurement in a known zero-flow zone is not required.

The impulse-activation technique has improved sensitivity to both low and high flow rates. In the EPA leak test well, the technique successfully discriminated between 0- and 1.4-ft/min flow conditions. The lowest quantified velocity was 1.8 ft/min or 10 BWPD, significantly below the EPA requirement of 3 ft/min. The upper limit of detection has not been determined but exceeds 137 ft/min.

The water flow log (WFLSM) measurement uses the impulse-activation technique and a Dual-Burst^M, thermal-decay-time (TDTSM) tool to detect water flow behind casing. An important application for this measurement is testing for fluid migration in the wellbore as part of the mechanical integrity testing process for Class I and Π disposal wells. The new oxygen-activation measurement was used in numerous production wells to identify the presence of water flow behind casing. Additional applications include the identification of open fractures in horizontal wells and the quantification of water flow in the tubing/casing annulus in injection and production wells.
A Field Comparison of Static and Dynamic Hydrocyclones
Authors: Jones P. S.
Published: December 2007

Three commercially available liquid/liquid hydrocyclones (LLHC's) are evaluated in an operating oil field. The oil-removal capabilities of two staticunits and one dynamic or rotating unit are determined across a full range of operating conditions. Such variables as driving pressure, flow rate, rejectrate. and rotational speed are investigated to optimize oil-removal efficiency. The key parameter of oil droplet-size distribution also is evaluated and itseffects on performance are determined.
Injection Schedules and Production Strategies for Optimizing Steamflood Performance
Authors: Kumar Mridul , Ziegler V. M.
Published: December 2007

Methods to optimize steamflood performance of a California heavy-oil reservoir were evaluated numerically. Simulation and field results show that a reduction in steam (heat) injection rate after steam breakthrough is beneficial. A linear heat-reduction schedule resulted in the highest discounted net or salable oil production with less steam injection compared with the constant injection schedule. For unconfmed patterns, steam migrates and drains oil from outside the pattern boundaries; therefore, rate reduction may not be beneficial in such cases. For mature steamfloods, conversion to hot waterflood or injector shut-in results in somewhat higher net oil production than for continued steam injection. Recompleting the producer after steam breakthrough resulted in increased recovery.
Prediction of the Risks of CO2 Corrosion in Oil and Gas Wells
Authors: Crolet Jean-Louis , Bonis M. R.
Published: December 2007

This paper discusses the various effects of CO2 on corrosion in general, a policy for fighting corrosion in offshore wells, the mechanisms of local CO2 attack, and a method of predicting the risks of CO2 corrosion in wells.
Offshore Platform Reliability Acceptance Criteria
Authors: Bea R. G.
Published: December 2007

Development of assessment, inspection, and maintenance (AIM) programs for requalification of existing offshore platforms requires definition of criteria to evaluate the adequacy and acceptability of the programs. This paper proposes an approach to judge fitness-for-purpose of existing platforms and their proposed AIM programs.
Fire Testing of Valve and Wellhead Equipment to API Specifications
Authors: Guice W. L. , Shinn T. L.
Published: December 2007

Mathematical modeling and test data were used to predict the temperatures of equipment in API fire testing. The thermal response of these systems is used to select critical parts for fire-resistant equipment. Conditions of internal components were found to be calculable on the basis of defined test criteria.
Advanced Casing Design Against Stress Corrosion Cracking of Grade P-110 Casing in Lignosulfonate Mud
Authors: Ikeda Shoichi
Published: December 2007

Stress corrosion cracking (SCC) of Grade P-110 casing couplings occurred in the hot, deep Minami-Nagaoka gas field. Detailed stress analyses revealed that the dynamic stress changes resulting from temperature caused by operation played a significant role in those failures. From this information, a new casing design was developed.
Model Diagnosis for Layered Reservoirs
Authors: Ehlig-Economides Christine A.
Published: December 2007

Interpretation models for layered reservoirs cannot be used effectively until a model has been identified for each reservoir layer. This paper introduces a new deconvolution form for presentation of multilayer transient (MLT) test measurements that is analogous to the log-log diagnostic plot used for model diagnosis of conventional transient test data.
Well-Control Operations in Horizontal Wells
Authors: Santos O. L. A.
Published: December 2007

This paper analyzes well control for horizontal wells. It presents a computer model for predicting the pressure behavior in a horizontal well during gas-kick removal and analyzes the simulation results for several field conditions. The paper also analyzes the drillpipe-pressure schedule, the kick-tolerance concept, and the swabbing effect during tripping out of the hole.
Class G Cement in Brazil— A Statistical Approach
Authors: Rosa F. C. , Coelho Osmond , Parente F. J.
Published: December 2007

Since 1975, Petrobras has worked with Brazilian Portland cement manufacturers to develop high-quality Class G cements. The Petrobras R&D Center has analyzed each batch of Class G cement manufactured by prequalified producers to API Spec. 10 standards and to Brazilian Assoc. of Technical Standards (ABNT) NBR 9831 standards. As a consequence, the Drilling Dept. at Petrobras now is supplied by three approved Class G cement factories strategically located in Brazil. This paper statistically analyzes test results on the basis of physical parameters of these Class G cements over 3 years. Statistical indices are reported to evaluate dispersion of the physical properties to obtain a reliability index for each Class G cement.
Linear Model Studies of the Immiscible CO2 WAG Process for Heavy-Oil Recovery
Authors: Dyer S. B. , Farouq Ali S. M.
Published: December 2007

This paper presents experimental work that quantifies the effect of water-alternating-gas (WAG) variables on the immiscible CO2 flooding process for moderately viscous heavy oils. The results may be used to determine such parameters as total CO2-slug size, WAG ratio, and number of WAG slugs. Analysis of the relative efficiency of each WAG slug is discussed.
Aquifer-Protection Considerations of Coalbed Methane Development in the San Juan Basin
Authors: Beckstrom James A. , Boyer David G.
Published: December 2007

Coalbed methane development in the San Juan basin has caused concern about several environmentally related health, safety, and remediation issues. This paper presents the findings of four groundwater-sampling programs and aquifer-protection work on producing wells and deep cathodic-protection groundbeds. The study concludes that Fruitland coal gas can migrate vertically behind uncemented wellbores that offset Fruitland coal gas wells, that remedial cementing of offsetting producing wells is feasible but costly, and that methane detected in domestic water wells near Fruitland coal development cannot be correlated directly to Fruitland coal gas development.
Subsurface Fracture Spacing: Comparison of Inferences From Slant/Horizontal and Vertical Cores
Authors: Lorenz John C. , Hill Robin E.
Published: December 2007

Comparison of cores from a slant/horizontal and three vertical wells at the same site shows that fracture spacing is irregular, significantly less than bed thickness, and cannot be derived from vertical-well data. Fracture spacing measurements must be filtered properly to be useful in reservoir models.
Optimum Application of Environmentally Safe Compound Greases for Casing and Tubing
Authors: Ogasawara Masao , Khoyama Fujimasa
Published: December 2007

It is now expected to prevent the contamination of the environment from the use of pipe dope or compound grease in oilfield drilling operations. Recently, some environmentally safe compound greases have been commercially developed and are available, but it is not generally known what effect they will have on the connection performance. This paper will discuss a detailed experimental study of the performance of these greases to investigate the galling tendency and sealing capability of American Petroleum Inst. (API) buttressthread connections (BTC) and metal/metal seal premium connections. It is already known that greases without both lead and zinc can be used for a single makeup of these connections, but some improvements were expected in the antigalling performance for multiple makeups. Greases without lead or without both lead and zinc are not satisfactory for preventing hydrostatic leakage in buttress connections because of the lack of buildup of powders for thread clearance, and the addition of graphite in substituting for these metal powders tends to produce galling. Thus, the ratio of solid/liquid elements and the roughness of the graphite grain will be important in the improvement of existing greases.
Safety of Casing-Shoe Test and Casing-Shoe Integrity After Testing
Authors: Morita Nobuo , Fuh Giin-Fa , Boyd P. A.
Published: December 2007

Increased injection volume during a casing-shoe test is needed to gather data, but it increases the possibility of lost circulation or reduced casing-shoe strength after testing. These hazards often encourage drilling engineers to halt casing-shoe tests prematurely just to confirm the casing-shoe strength. This paper addresses drilling-engineering concerns regarding lost circulation during a casing-shoe test, the extent of fracture propagation, the amount of data obtainable as a function of the drilling-fluid volume injected, and the casing-shoe integrity expected after testing. Laboratory data and a numerical model are used to illustrate phenomena that occur during casing-shoe tests. Analysis of the data yields guidelines for safe casing-shoe tests.
Matrix Acidizing: A Novel Approach to Foam Diversion
Authors: Zerhboub Mohammed , Ben-Naceur Kamel , Touboul Eric , Thomas Ron
Published: December 2007

This paper investigates the use of the foam diversion technique experimentally to understand the mechanisms governing diversion in sandstones. The effect of the main parameters is presented and discussed, and a process is proposed. Field test results have shown the efficiency of foam as a diverter. Acidizing of water-cut wells is highlighted.
Analysis of Shear-Wave Polarization in VSP Data: A Tool for Reservoir Development
Authors: Winterstein D. F. , Meadows M. A.
Published: December 2007

This paper presents results of a new method of using vertical seismic profile (VSP) data to deduce information on certain rock properties that are important for reservoir development. These properties are the direction of maximum horizontal stress or the orientation of aligned fractures and the variation of these quantities with depth. Such information can be important for secondary recovery, horizontal drilling, and infill drilling. The VSP method involves a shear-wave (S-wave) source at the surface and a downhole three-component (3-C) geophone to record first-arrival S waves along predominantly vertical ray paths. The data are analyzed to determine particle motion directions (polarizations) and relative travel time of the two S waves. In simple cases, the polarization of the faster S wave is oriented parallel to the direction of maximum horizontal compressive stress orthe predominantfracture alignment.The travel-time differences between the S waves contain information on the effects of unequal horizontal stresses.

We recorded a number of VSP's for S-wave analysis in California and Texas oil fields. Results from three VSP's are presented here. In nearly every case, we found measurable travel-time differences and also significant variation of the S-wave polarization azimuths with depth. Polarization azimuths, although typically consistent over depth intervals of several hundred feet, tended to change abruptly at various depths. A simple layer-stripping technique made it possible to follow the polarization changes and determine travel-time differences over successive depth intervals. The variations with depth are particularly interesting because they indicate changes of principal stress direction or fracture orientation.
Application of Fluorescence Techniques for Mud-Logging Analysis of Oil Drilled With Oil-Based Muds
Authors: Reyes Marilyn V.
Published: December 2007

The Texaco E&P Technology Div. has developed two fluorescence techniques to enhance the detection of crude oil extracted from formation samples and to improve mud logging as a formation evaluation tool. The quantitative fluorescence technique (QFT) is a portable field method that uses a single excitation wavelength and measures fluorescence at a narrow emission range. When plotted vs. depth, the intensity measurements generate an oil concentration profile of the well. The QFT has successfully located oil-bearing zones that were difficult to identify with conventional mud-logging techniques. The total scanning fluorescence (TSF) technique uses a more sophisticated ultraviolet (UV) spectroscopic instrument and generates a 3D fluorescence spectrum or "fingerprint." This spectrum results from the total fluorescence contribution of the fluorescing species present in the oil. The unique chemical makeups of different crude oils have spectral characteristics that can be used to predict oil composition or type. The TSF method gives more information than conventional fluorescence techniques. This paper discusses the effectiveness of the QFT and the TSF method for identifying crude oil in the presence of fluorescing drilling-mud additives (such as base oils or diesel) and includes a feasibility study that demonstrates the application of these methods in a North Sea well drilled with an oil-based mud. Examples in wells offshore the Mediterranean Sea and Gulf of Mexico are also cited.
On The Efficiency Of Electrical Submersible Pumps Equipped With Variable Frequency Drives: A Field Study
Authors: Patterson M. M.
Published: December 2007

A field study was conducted on 18 electrical-submersible-pump-(ESP-) equipped wells operating in the Williston basin. Fifteen of these wells were run with variable frequency drives (VFD's). The purpose of the study was to determine the efficiency and operating characteristics of ESP's operating with VFD's and compare them to those without. Voltage, current, power, and frequency were measured at the drive input, the drive output, and ESP input. Production data were recorded and power and efficiency were calculated at all measurement locations and compared to published data.