bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments on Mixing During Miscible Displacement in Porous Media
Authors: Brigham William E. , Reed Philip W. , Dew John N.
Published: December 2007

The paper describes experiments on miscible displacement in various porous media and the results of these experiments. Both glass bead packs and natural cores were used. Bead diameters varied from 0.044 to 0.47 mm, and pack lengths varied from 83 to 678 cm. Natural cores used were Berea and Torpedo sandstone.

By taking samples as small as 0.5 cc and using refractive index for analysis, the data on break through curves could be plotted to within ± 0.5 per cent. To plot the data correctly on error function paper, a parameter (Vp - v)/vV was used which allowed for the predicted growth of the front as it moved past the observer.

The change in the amount of mixing (length of mixed zone) was studied by varying velocity, length of travel, bead size, viscosity ratio and pack diameter. When the displaced material was less viscous than the displacing material (favorable viscosity ratio), these changes were adequately predicted by theory. When natural cores were used, rather than glass beads, the amount of mixing was greatly increased - also qualitatively predicted by theory.

In experiments with favorable viscosity ratios in which the ratio was varied from 0. 175 to 0. 998, it was found that the rate of mixing was changed by a factor of 5. 7. Thus, the rate of mixing is strongly affected by viscosity ratio, even when the theoretical error function relationship for mixing is valid.

Experiments using fluids with viscosity ratios near 1.0 showed that the instability effects of even a slightly unfavorable viscosity ratio (1.002) caused disproportionately more elongated breakthrough curves than found with a favorable viscosity ratio (.998). When the viscosity ratio was as high as 5.71 these instability effects were much more pronounced, as evidenced by the shape of the breakthrough curve. The displacements at viscosity ratios above 1.0 no longer followed the theoretical error function curve.
Predicting Pressure Distribution in Irregularly Shaped Bounded Reservoirs
Authors: Kuo M. C. T.
Published: December 2007

Many methods use radial and rectangular systems to interpret unsteady-state reservoir flow problems, but very little information is currently available for irregular drainage shapes. For many practical cases, however, the reservoir drainage shape is too complicated to be approximated by a circular or rectangular shape. This paper develops a means of predicting pressure-transient behavior in an irregularly shaped reservoir.

To generate a dimensionless-pressure-drop function, it is difficult to superpose the line-source solution of image wells in space for irregular drainage shapes. In this paper, the dimensionless-pressure-drop function is obtained by superposing the line-source solutions of image wells in time. The flow rates of image wells at each timestep are determined through solving a set of simultaneous linear algebraic equations that describe the conditions at the drainage boundary. The validity of this approach is proved by comparison of the calculated dimensionless-pressure-drop functions with literature values for various rectangular drainage shapes.
Maureen Oil Field—First Year of Production
Authors: Wootton D.
Published: December 2007

This paper presents the first year of development of the Maureen field in the British sector of the North Sea. A steel platform gravity structure was used for development. The crude oil is tanker-loaded at an articulated loading column (ALC). Production, seawater injection, and gas lifting are discussed.

Production covers well completions, wellhead tiebacks, process-plant performance, and downtime. In particular, the performance of the ALC is detailed. At the column, successful modifications to the hawser system for tanker mooring were made, to reduce excessive hawser replacements. Seawater injection experiences are described, and details of the perforating techniques and stimulation treatments are given. Gas lifting of a well to test the surface and downhole facilities is described.
Operational Experience of Running Multicasing Gas Compression Trains on a North Sea Platform
Authors: Hancock W. P.
Published: December 2007

This paper describes the difficulties of operating multicasing compression trains in parallel and the special problems associated with a very-high-pressure centrifugal gas-injection compressor. The Statfjord B platform features one of the most complex gas-compression systems in the world for an offshore platform and uses some of the most advanced centrifugal gas compressors and aeroderivative gas turbines currently available. Four different gases flashing from the crude in flash drums of cascading pressures are recompressed and injected into the producing reservoir at pressures as high as 45 000 MPa [450 bar gauge].

Conservation of valuable associated gas from offshore oil-production facilities demands high gas-compression efficiencies. Therefore, timely resolution of operational problems is paramount.

This paper details the operational problems and their resolutions, which helped the Statfjord B platform attain and exceed its design output.
Steamflood Strategies for a Steeply Dipping Reservoir
Authors: Hong K. C.
Published: December 2007

A computer simulation study was conducted to determine the best steamflood strategy for a steeply dipping (20° [0.35-rad]) reservoir. A compositional steamflood simulator was used with both two-dimensional (2D cross section) and three-dimensional (3D) models of the reservoir.

The study showed that gravity drainage of the heated oil is the main production mechanism in steamflooding steeply dipping reservoirs. Consequently, oil production is strongly affected by injector and producer locations. The best steamflood strategy for this type of reservoir, therefore, involves judicious selection of injector and producer locations, reducing steam injection rate and shutting in wells selectively at appropriate times, and injecting a noncondensable gas to prevent steam cycling in the depleted updip portion of the reservoir.

This paper compares oil production performances and steamflood efficiencies for nine different operating strategies and recommends the best strategy for a steeply dipping reservoir.
Effect of WAG Injection and Rock Wettability on Oil Recovery During CO2 Flooding
Authors: Huang E. T. S. , Holm L. W.
Published: December 2007

Previous studies to determine the extent of oil trapping by water during CO2 water-alternating-gas (WAG) flooding have shown that rock wettability strongly affects this trapping. A significant trapping occurs in water-wet rock, and less trapping occurs in oil-wet rock. This paper presents laboratory results of Devonian crude oil displacement from watered-out Berea and reservoir cores by use of continuous CO2 injection, single-slug CO2 injection (followed by water), and CO2 WAG injection at miscible reservoir conditions of 120°F and 2,500 psig [49°C arid 17.2 MPa]. The reservoir cores used in this study were mixed- wet (Devonian and Muddy formations) and oil-wet (Tensleep formation). The Berea cores used had their wettability artificially altered to simulate these natural wettabilities. The X-ray photoelectron spectroscopic (XPS) method for measuring carbon content of rock surface was used to provide a qualitative measurement of wettability of the rock samples.

The results of the study indicated that the experimental wettability-altering technique came close to duplicating reservoir rock wettability. The oil recovery data at the end of 1 PV fluid injection (continuous CO2 or WAG CO2) indicated that (1) in preferentially water-wet Berea cores, more than 45% of the waterfiood residual oil trapped by CO2 WAG; (2) in mixed-wettability Berea cores, 15 to 20% of the waterfiood residual oil was trapped; and (3) in oil-wet Berea cores, less than 5% residual oil was trapped.
Gladfelter Deconvolution
Authors: Kuchuk Flkrl J.
Published: December 2007

In this paper, I present the general characteristics of the Gladfelter deconvolution method, which has been used for determining the constant-rate behavior of a system from measured flow rate and pressure. The validity of the method is established for different rate variations and flow geometries (radial, linear, and spherical). The method works well for linear and exponential flow variations and fails for the general flow case. The commonly assumed first semilog straight line resulting from the Gladfelter deconvolution is instead a tangential line parallel to the final semilog straight line owing to a constant-flow-rate period. New solutions are presented for cylindrical, linear (fractured), and spherical wellbore flow geometries with exponential-flow and constant-storage cases. In addition, useful asymptotic solutions are given for the determination of reservoir parameters from the Gladfelter method.
Correlation of Drag Reduction With Modified Deborah Number For Dilute Polymer Solutions
Authors: Rodriguez J.M. , Zakin J.L. , Patterson G.K.
Published: December 2007

Correlation has been obtained between drag-reducing characteristics forturbulent flow in a pipe and measurable properties of several polymersolutions. Several concentrations of high molecular weight polymethylmethacrylate in toluene, high molecular weight polyisobutylene in both tolueneand cyclohexane, medium molecular weight polyisobutylene in cyclohexane andbenzene and low molecular weight polystyrene in toluene were studied. Dataobtained in these nonpolar solvents and literature data for more polar solventswere successfully correlated as the ratio of measured friction factor to purelyviscous friction factor vs the modified Deborah numbervr1/D0.2, where r1 is the first-moderelaxation time of the solution estimated by the Zimm theory. A shift factorwhich is a function of intrinsic viscosity 1/(4[?] - 1) allowed all the dataobtained with nonpolar solvents to be correlated as a single function. Forthese systems, most of the data fit a single curve to within ±5 percent of theaverage friction factor ratio. The shift factor did not give a unique functionof the data for the more polar systems.

INTRODUCTION

The phenomenon of drag reduction in polymer solutions was first studied byToms1 in dilute solutions of polymethyl methacrylate inmonochlorobenzene. The drag ratio for flow through circular tubes has beendefined2 as the ratio of the pressure - drop of the solution to thepressure drop of the solvent at the same flow rate. The drag ratio is less than1.0 for a drag-reducing fluid. Practical use of drag reduction is being made infracturing operations in the petroleum industry.3

A more fundamental quantity is the friction factor ratio, defined as theratio of the observed pressure drop to that predicted for a solution of thesame viscosity characteristics and density at equal flow rates using theDodge-Metzner friction factor equation.4Equation 1

Viscous solutions with drag ratios greater than 1.0 can have friction factorratios less than 1.0. For practical applications, it is drag reduction which isof interest. However, for correlation the fundamental ratio is the frictionfactor ratio.

In recent years, drag reduction has been studied extensively. Recent studieshave shown that reasonable predictions of the incipience of drag reduction inpolymer solutions can be made from the properties of the solutions and the flowvariables.5 However, it has not been possible to predict accuratelythe amount of drag reduction to be expected for a given polymer solutionwithout any drag-reducing turbulent flow data on the samesolution.6
Analysis of the Pressure Response of a Single-Probe Formation Tester
Authors: Dussan V. E. B. , Sharma Yogeshwar
Published: December 2007

The single-probe formation tester is a logging tool used for measuring the vertical pressure profile of formation fluids and retrieving fluid samples. We propose using the pressure measurements taken during this tool's normal operation to determine local values of both the horizontal and vertical permeability (i.e., permeability parallel and perpendicular to the formation bedding planes, respectively) in an anisotropic formation.
Diamond-Bit Hydraulics Model
Authors: Warren T. M. , Behr Suzanne M.
Published: December 2007

This paper describes an analytical technique that calculates the fluid velocities and pressures under a surface-set diamond bit. The technique is based on solving the continuity and energy equations for a series of flow cells that covers the bit face. Each cell is described with geometrical dimensions and an integrated property model to account for flow around the cutters. Experimental data from simulated diamond-bit segments provide friction-factor data and model validation. The results of analyzing a commercial diamond bit are also presented. The model is being developed to improve the hydraulic design of diamond bits.
Field Correlation Between Internal Taper Length and Tube Failures in 4.5-in., 16.60E, IEU Drillpipe
Authors: Gensmer Richard P.
Published: December 2007

Noble Drilling Corp. has become increasingly concerned with premature failures in 4.5-in. [11.4-cm], 16.60 Grade E, IEU drillpipe tubes that meet industry requirements for metal structure, hardness, strength, and chemical composition and that show no signs of physical abuse. Our study of the pipe structure showed that a high percentage of tube failures were in tubes with short internal taper lengths. We examined a string of drillpipe with 18 tube cracks in the first 2, 800 rotating hours in an area where 13, 000 to 18, 000 hours is a common life expectancy and studied drillstrings produced by three other manufacturers. We found that 80% of our failures occur within 10 to 12 in. [25 to 30 cm] of the internal taper, that the taper lengths are shorter among the failed joints than among a general population of drillpipe, and that these short taper lengths are not common to just one manufacturer or nation. We did not prove a causal relationship, but we did establish a correlation strong enough to warrant further investigation of the phenomenon and the establishment of a method that uses internal taper length as a criterion to inspect and purchase drillpipe.
Inspection Interval Guidelines To Reduce Drillstring Failures
Authors: Dale B. A.
Published: December 2007

Inspection interval guidelines were developed to reduce the occurrence of costly drillstring fatigue failures. The guidelines are based on a state-of-the-art fracture mechanics model and incorporate reliability data of commercial inspection services using conventional nondestructive testing techniques. On the basis of extensive full-scale testing, the model was found to predict fatigue-crack-growth behavior reliably. By establishing inspection intervals on the basis of fatigue-crack growth, inspection services are systematically and cost-effectively specified to achieve acceptable reliability (or risk). Simple equations and charts are presented in terms of practical drilling parameters to reduce typical downhole fatigue failures.
Polymer/Bentonite/Soil Admixtures as Hydraulic Barriers
Authors: Liao W. A.
Published: December 2007

Preventing waste fluids retained in on-site earthen pits from leaching into the surrounding environment has become a growing concern in the oil and gas industry. One possible solution is to incorporate a pit liner that acts as an impervious barrier between the contained fluids and adjacent soil or groundwater outside the pit. Such materials as flexible membranes, recompacted native soils, and polymeric/soil admixtures are commercially available for pit-lining applications. This paper briefly discusses the relative merits of each type of liner for oilfield waste. Among these liner materials, polymer/bentonite/soil admixtures, which consist of a blend of high-molecular-weight linear and crosslinked polymers, have many advantages, including self-sealing capability, inertness to degradation, and easy installation at low cost.

The objective of the study was to compare the permeability and the susceptibility to chemical degradation of a variety of modified clay liners designed for oilfield waste pits. The ideal liner should be resistant to brines and hydrocarbons, with permeability <0.4 × l0−7 in./sec [<1 × 10−7 cm/s]. A number of such admixtures were investigated to study sealing effectiveness. The results of this study indicate that certain modified clay liners are highly impermeable to brines and water-immiscible hydrocarbons and can significantly reduce hydraulic conductivity to <0.4 × l0−7 in./sec [< 1 × 10−7 cm/s] when incorporated into native soil. The resultant improved sealing capabilities offer a low-cost, reliable, long-term solution for impervious hydraulic barriers (pit liners). This paper also discusses applications of the selected polymer/bentonite/soil admixtures.
Statistical Assessment and Sampling of Drilling-Fluid Reserve Pits
Authors: Wojtanowlcz Andrew K. , Field Stephen D. , Krllov Zoran , Spencer Fritz L.
Published: December 2007

A field survey of four drilling-mud reserve pits associated with 14,000-ft [4267-m] exploratory wells onshore U.S. gulf coast is presented. Each pit was sampled with a three-dimensional grid base with 80 to 100 samples per pit. The samples were analyzed for solids, liquids, rheological properties, and such contaminants as oil, chlorides, and metals (Cr, Pb, Ba, and Zn). The statistical data were used to develop the recommended pit sampling procedure, which included the best sampling depth and the optimum number of samples to assess the metal toxicity within a given accuracy. Two example calculations are also presented.
Improved Detectability of Blowing Wells
Authors: de Lange John I. , Darling Toby J.
Published: December 2007

Relief wells to kill a blowing well can be drilled more efficiently if the casing joints of a blowing well are magnetized to improve the detection range of magnetostatic homing-in tools. This method was proved in field tests, and a considerable increase in the detection range of such magnetostatic tools as the Magrange™ and measurement-while-drilling (MWD) tools (from 50 to 100 ft [15 to 30 m]) was established.
Pressure Behavior of Layered and Dual-Porosity Reservoirs in the Presence of Wellbore Effects
Authors: Olarewaju J. S. , Lee W. J.
Published: December 2007

This paper presents a new analytical solution for pressure-transient tests from layered reservoirs with or without crossflow. The analytical solution is for modeling layered-reservoir systems with unsteady-state or pseudosteady interlayer crossflow, commingled or stratified flow, and even dual-porosity systems with pseudosteady matrix-to-fracture transfer in the presence of skin, wellbore storage, and phase segregation.
Microbial-Enhanced Waterflooding: Mink Unit Project
Authors: Bryant Rebecca S. , Burchfield Thomas E. , Dennis D. M. , Hitzman D. O.
Published: December 2007

A microbial-enhanced waterflooding field project is being conducted in the Mink Unit of the Delaware-Childers field in Nowata County, OK. A microbial formulation was injected into four injection wells and has been followed by periodic injections of molasses as nutrient. Laboratory and field procedures that were used to design the test are described. Improvements in both oil production rate and WOR's have been observed.
A New Method for Estimating the Dykstra-Parsons Coefficient To Characterize Reservoir Heterogeneity
Authors: Jensen Jerry L. , Currie Iain D.
Published: December 2007

We propose a new method to estimate the Dykstra-Parsons coefficient that leads to a more statistically reliable indication of the true heterogeneity level. The new method extracts more information from the data to produce an estimate that gives half the error of the traditional approach. Several cases are considered to demonstrate the effects of more reliable Dykstra-Parsons coefficients on predicted reservoir performance.
Tracer- and Pressure-Test Analysis for Characterization of Areally Heterogeneous Reservoirs
Authors: Mishra Srikanta , Brigham William E. , Orr Franklin M.
Published: December 2007

This study compares simulated well-to-well tracer and transient pressure tests in a quadrant of a repeated five-spot with spatial variations in permeability. Single-layer heterogeneous media with an autocorrelated and log-normal permeability distribution are generated with a stochastic moving-average method. Finite-difference simulation of pressure behavior in these systems indicates that the geometric mean of effective permeabilities around injection and production wells is a good approximation for the steady-state interwell permeability. A dimensionless permeability difference, defined in terms of these quantities, correlates with a heterogeneity index, defined as the product of permeability variance and a dimensionless correlation length scale.

Tracer flow is simulated with a particle-tracking procedure. Simulations show that when the heterogeneity index is small, tracer response can be matched with solutions of the convection-dispersion equation with a constant dispersivity that is proportional to the heterogeneity index. For larger values of this index, preferential flow paths are created that cause tracer-breakthrough curves to behave as though they result from flow in a layered system. A method is proposed to estimate the heterogeneity index from pressure-test data and thus to predict the nature of the tracer response qualitatively.
Displacement Mechanism and Water Shielding Phenomena for a Rich-Gas/Crude-Oil System
Authors: Tiffin D. L. , Sebastian H. M. , Bergman D. F.
Published: December 2007

This paper presents an experimental study involving a series of hydrocarbon miscible displacements of a crude oil. Compositional analyses of both flowing effluent phases show that most of the oil was recovered by the condensing-drive mechanism. High mobile water saturations in the highly water-wet Berea cores used led to the same oil-trapping phenomena as noted for CO2 displacements.
Appraisal of the Use of Polymer Injection To Suppress Aquifer Influx and To Improve Volumetric Sweep in a Viscous Oil Reservoir
Authors: Hughes D. S. , Teeuw D. , Cottrell C. W. , Tollas J. M.
Published: December 2007

A novel way to use polymer injection to suppress the influx of a strong edge aquifer in a shallow, dipping reservoir containing a 15-cp [15-mPa·s] oil and thereby to improve volumetric sweep has been investigated. Experimental studies were undertaken to determine the appropriate polymer properties, which were then used in simulation studies to establish oil-recovery profiles.
Imaging Fluid Saturation Development in Long-Core Flood Displacements
Authors: Graue Arne , Kolltveit Kristofer , Lien Jan. R. , Skauge Arne
Published: December 2007

Fluid saturation development in long-core flood experiments is investigated. Information on 1D fluid saturation distributions is obtained by labeling the fluid phases with nuclear tracers and detecting radiation with a movable detector. Various flood experiments were done on 2.5-ft [76-cm] -long sandstone cores. In miscible displacements where radioactive brine is displacing inactive brine, dispersion and ion adsorption are evaluated. Imaging saturation profiles during drainages and waterfloods gives information on saturation-front velocity and time development of local saturation variations. Experimental results are compared with numerical results from a 1D front-tracking black-oil simulator that incorporated inhomogeneities and capillary effects. Surfactant floods were investigated to test the applicability for EOR studies further.
Batch-Mix Fracturing: An Effective Method of Stimulating Moderate-Permeability Reservoirs
Authors: Cramer David D. , Songer Mark A.
Published: December 2007

This paper evaluates batch-mix-fracturing (BMF) applications in moderate-permeability reservoirs. Specialized BMF equipment provides a reliable means of creating short, highly conductive fractures. BMF efforts have been improved by effective treatment design and the use of a computer-driven fracture simulator. A case study of fracture treatments in a Wyoming oil reservoir indicates that the BMF technique can provide results superior to conventional methods with continuous-mix equipment.
Borehole Instability in the Western Canadian Overthrust Belt
Authors: Woodland David C.
Published: December 2007

Borehole instability is primarily a rock mechanics problem. Regional earth stresses and typical rock strengths are used to explain the widespread nature of irregularly shaped, fragile boreholes in the western Canadian Overthrust Belt (foothills). Drilling fluids and practices are investigated with a rock mechanics model of borehole failure. Although drilling practices can significantly affect problems associated with borehole wall failure, they are not the primary cause.
Forecasting the Life of Rock-Bit Journal Bearings
Authors: Kelly Joseph L.
Published: December 2007

This paper describes an analytical procedure for forecasting the life expectancy of rock-bit journal bearings. Actual performance data and reliability analyses are used to establish empirical relationships and a graphic procedure that relates the risk of bearing failure to operating parameters and drilling cost.
One-Trip, Multizone Gravel-Packing Technique for Low-Pressure, Shallow Wells
Authors: Welrich John B. , Zaleski Theodore E. , Tyler Steve L.
Published: December 2007

This paper describes a one-trip, multizone gravel-packing technique designed for use in short-zoned, shallow, low-pressure wells. The system, which allows several zones to be completed with a single gravel-pack assembly, has been adapted for use in both standard and thermal applications.
Formation Damage From Acid Treatments
Authors: Bryant Steven L. , Buller David C.
Published: December 2007

Well treatments with only HCl are potentially damaging in formations that contain aluminosilicate minerals (clays, feldspars, and micas) because HCl reacts significantly with aluminosilicates, leaching aluminum and forming hydrated silica. Fluid flow past leached mineral particles liberates mineral fragments and amorphous silica within the pore network. These fines can block pore throats, reducing the rock permeability. Both field data and reservoir-condition coreflood test results are consistent with this chemical reaction and permeability impairment mechanism. The average permeability reduction in our corefloods was 35%.
An Innovative Single-Completion Design With Y-Block and ESP for Multiple Reservoirs
Authors: Moradl Shirall C.
Published: December 2007

This paper describes an effective well-completion program initiated in five recently developed fields in the northwest Java Sea. Because these fields contain multiple reservoirs, an innovative downhole completion system was implemented to obtain optimum production and operational flexibility at minimal cost.

Depending on the number of reservoirs, as many as five sealbore-retrievable packers were set in a well and then individually tested to ensure isolation. This system allows us to (1) perforate different reservoirs selectively; (2) isolate, acidize, test, and monitor separate zones; (3) produce a well by natural flow initially or by electric submersible pump (ESP); (4) commingle zones; (5) run pressure surveys and production logs; (6) manipulate and eliminate water/gas producing zone(s); (7) service the ESP as required without fluid loss to the formation; and (8) protect the downhole equipment from corrosive gases by continuous inhibition. Major downhole work is performed inexpensively by wireline and/or snubbing units.

After completion, three different reservoir lithologies (sandstone, limestone, and metamorphic) were isolated, stimulated, tested, monitored, and selectively produced. To date, more than 90 oil wells with as many as three different lithologies and 20 separate formations have been completed successfully. Since this paper was presented, about 20 more platforms have been completed (nine wells per platform) with this system. This innovative completion system allows optimal production of multiple-reservoir fields at minimal cost.
The Effect of Carboxylic Acid Anions on the Stability of Framework Mineral Grains in Petroleum Reservoirs
Authors: MacGowan Donald B. , Surdam Ronald C. , Ewing Richard E.
Published: December 2007

This paper presents experimental and empirical evidence to show that carboxylic acid anions (CAA's) are a major diagenetic control on first-cycle basins in Jurassic-to-Pleistocene reservoirs in the 80-to-120°C thermal window.
Acid-Soluble Magnesia Cement: New Applications in Completion and Workover Operations
Authors: Sweatman Ronald E. , Scogglns W. Chrys
Published: December 2007

Acid-soluble magnesia cement (MC) was used in production zones to plug perforations temporarily to reduce brine losses during completion and workover operations. This has resulted in substantial savings for operators. The cement has also been used to reduce potential formation damage. This paper describes some of the characteristics of the cement, field applications, and results.
Interpretation of ADEPT Logs in the Presence of Mudcakes
Authors: Freedman Robert , Grove Gregory P.
Published: December 2007

Results of a theoretical investigation of mudcake effects on the high-frequency, dielectric, adaptable electromagnetic propagation tool (ADEPTSM) are presented. Charts are presented that correct log data for mudcake effects, thus giving true formation travel times and attenuations. Mudcake effects on the ADEPT interpretation are illustrated with data from a shaly sand well.
Dynamic Measurements of Beam-Pump Parameters
Authors: Lea J. F. , Bowen J. F.
Published: December 2007

Measurements of nine electrical and mechanical parameters were made on conventional and special-geometry units during operation. All quantities were measured simultaneously and computer-recorded for a variety of pumping conditions. Using this data, we compared measured dynamic gearbox torques with calculated values, illustrating how calculation techniques model dynamically measured data. Calculated efficiencies indicating losses through the units from polished rod to the gearbox are shown to be necessary for adjusting gearbox torque calculations to measured values. Also, torque/speed curves are shown at the motor sheave. These data are corrected for inertial effects and plotted vs. motor manufacturers’ published curves. Possibilities for future work incorporating these measurement techniques while the unit is in operation were discussed. In general, the data show how dynamically measured beam-pump data compare with conventional calculation techniques.
Efficiency and Pressure Recovery in Hydraulic Jet Pumping of Two-Phase Gas/Liquid Mixtures
Authors: Jiao Baohua , Blais Roger N. , Schmidt Zellmir
Published: December 2007

Hydraulic jet pumping of gas/liquid mixtures was studied experimentally, and a mathematical model is proposed to extend the standard single-phase model for predicting efficiency and pressure recovery to suction fluids with gas/liquid ratios up to 2, 200 scf/STB. The experimental program comprises 616 low-pressure tests in a plastic model pump designed for flow visualization and measurement of pressure profile along the throat and diffuser, and 373 high-pressure tests on a stock pump. For the high-pressure tests, power fluid was supplied at 200 to 3, 000 psi and at 200 to 860 B/D; air was supplied from 0 to 185 Mscf/D. Discharge pressures ranged from 800 to 2, 000 psi.

The mathematical model extends a previous model that describes single-phase performance from mass and energy conservation. The empirical loss coefficients for the nozzle and throat/diffuser are replaced by a nondimensional expression that varies as three dimensionless parameters: nozzle-to-throat area ratio, discharge-to-power-fluid pressure ratio, and air/water ratio (which usually is in conventional units of cubic feet per stock-tank barrel but is, of course, basically dimensionless). The loss coefficient for the nozzle is constant, but for the throat/diffuser it is a constant plus a product of a constant times the three parameters, each to a power.

Compared with the standard model, which always overpredicts pressure recovery and thus efficiency, the new model reduces the standard error of the estimate to 18% of its former value.
Dual Leakoff Behavior in Hydraulic Fracturing of Tight, Lenticular Gas Sands
Authors: Warpinski Norman R.
Published: December 2007

Stimulation experiments conducted in anisotropic, naturally fractured, tight, lenticular gas sandstones have shown the existence of a dual-leakoff phenomenon. Below a threshold pressure, the leakoff coefficient is very low and fluids are very efficient. Above the threshold, leakoff increases by a factor of 50, slurries dehydrate rapidly, and screenouts occur in minutes. The leakoff has been shown to be controllable to some extent with 100-mesh sand. Results of three stimulation experiments are presented, including a treatment that screened out, a minifracture experiment that showed the effectiveness of 100-mesh sand, and a final successful stimulation.
Experimental Study of Cocurrent and Countercurrent Flows in Natural Porous Media
Authors: Bourbiaux Bernard J. , Kalaydjian François J.
Published: December 2007

Flow experiments involving cocurrent and countercurrent spontaneous water/oil imbibition were performed on the same laterally coated sample of a natural porous medium with local saturation measurements and various boundary conditions. The experiments with countercurrent imbibition showed slower oil recovery, a smoother water/oil front, and slightly lower ultimate oil recovery than those with predominantly cocurrent imbibition. Numerical simulations revealed that the relative permeabilities that enabled good prediction of countercurrent oil recovery rate are about 30% less than the conventional cocurrent relative permeabilities at a given water saturation. Viscous coupling is assumed to be the origin of this difference. A new formulation of Darcy equations that uses a matrix of mobilities was found to be in qualitative agreement with experimental results.
A New Iterative Solution Technique for Reservoir Simulation Equations on Locally Refined Grids
Authors: Brand Clemens W. , Heinemann Zoltan E.
Published: December 2007

This paper presents an incomplete LU (ILU) factorization technique coupled with generalized conjugate-gradient acceleration especially designed for linear equations resulting from locally refined grids. The factorization is based on a special ordering scheme. This repeated red/black (RRB) ordering can cope naturally with grid irregularities introduced by local refinement. The scheme is also very effective on regular grids, where the condition number (a measure of the convergence rate) of the preconditioned linear system increases asymptotically with the number of gridblocks more slowly than it does for conventional ILU preconditionings. For large linear systems, fewer iterations are needed to reach convergence. This makes the method highly competitive compared with other techniques even on regular grids, although the new ordering scheme requires more data handling than standard orderings. Results for several idealized test cases [implicit-pressure, explicit-saturation (LMPES) equations] show the new method to be faster than standard iterative methods.
A Control-Volume, Finite-Element Method for Local Mesh Refinement in Thermal Reservoir Simulation
Authors: Forsyth Peter A.
Published: December 2007

This paper describes a control-volume, finite-element technique for coupling coarse grids with local fine meshes. The pressure is treated in a finite-element manner, while the mobility terms are upstream weighted in the usual way. This requires identification of the cell volumes and edges that are consistent with the linear finite-element discretization of the pressure. To ensure that the pressure equation yields an M matrix, various conditions are required for the type of triangulation allowed. Because the form of the equations is similar to the usual finite-difference discretization, standard techniques can be used to solve the Jacobian. The local mesh-refinement method is demonstrated on some thermal reservoir simulation problems, and computational results are presented. Significant savings in execution times are obtained while predictions similar to global fine-mesh runs are given.
Effect of Rheology on Gel Placement
Authors: Seright R. S.
Published: December 2007

This study investigates whether rheology can be exploited to eliminate the need for zone isolation during gel placement. Eight different Theological models were used to represent the properties of existing non-Newtonian gelling agents. Gel placement was examined in linear and radial parallel corefloods and in fractured and unfractured injection wells. The analysis indicates that, compared with water-like gelling agents, existing non-Newtonian gelling agents will not reduce the need for zone isolation during gel placement in radial-flow systems.
Re-Formation of Xanthan/Chromium Gels After Shear Degradation
Authors: Tsau J. -S. , Liang J. -T. , Hill A. D. , Sepehrnoori Kamy
Published: December 2007

Studies were conducted on the re-formability of xanthan-gum/chromium gels that have been degraded by shear. The re-gelation study of xanthan/chromium gels showed that gels that have been sheared take longer to re-form than to gel initially and that the original gel strength often was not recovered after shearing. The weaker the gel at the time of shearing, the more likely it is that it will obtain the ultimate strength of an unsheared gel of the same formulation.
Well-Conditioning Effects on Bubblepoint Pressure of Fluid Samples From Solution-Gas-Drive Reservoirs
Authors: Peres Alvaro M. M. , Macias-Chapa Luis , Serra Kelsen V. , Reynolds Albert C.
Published: December 2007

This work considers the determination of the initial or average reservoir bubblepoint pressure from a fluid sample obtained from a well producing a solution-gas-drive reservoir. It is shown that standard API recommended well-conditioning procedures (rate reductions) for obtaining a single-phase (liquid) bottomhole fluid sample do not always redissolve all free gas. Thus, it is not always possible to obtain a single-phase liquid (oil) bottomhole fluid sample that has a bubblepoint pressure equal to the initial or average reservoir bubblepoint pressure. Moreover, monitoring the producing GOR and bottomhole pressure does not always reliably indicate whether two-phase (oil and gas) or single-phase (oil) flow is prevalent in the near-wellbore region. Contrary to current opinion, it is shown that recombination of surface samples of oil and gas from the producing GOR usually yields reliable estimates of average reservoir bubblepoint pressure.
Uplifts and Tilts at Earth's Surface Induced by Pressure Transients From Hydraulic Fractures
Authors: Palmer Ian D.
Published: December 2007

The pressure transient that spreads through the formation during and after a hydraulic fracture treatment pressurizes the formation and induces a certain "swelling." This swelling and the accompanying uplift at the earth's surface can be estimated with poroelastic theory. The uplift may produce a significant signal in tiltmeter devices placed at the surface. Six fracturing treatments in liquid-saturated reservoirs, all with tiltmeters to diagnose the fractures, were analyzed. In five cases, routine tiltmeter analysis postulated a horizontal fracture component (in the remaining case, a near-vertical fracture of dip 70 to 85° probably could also be interpreted by a vertical fracture with a subsidiary horizontal component). In three treatments, however, theoretical tilts calculated from the pressure transient can account for the magnitude of the tiltmeter signals, which had previously been explained by a horizontal fracture component. This result is important because the formation swelling and surface uplift associated with the pressure transient from a hydraulic fracture treatment are not usually deconvolved from the raw tiltmeter signals before their interpretation in terms of hydraulic fracture geometry. In some cases, this may be necessary. Otherwise, the shape/size of inferred horizontal and vertical fracture components may be in error; i.e., neglect of the pressure-transient effect may cause overestimation of the size of the horizontal fracture component. At worst, neglecting the pressure-transient effect may result in an inferred horizontal fracture component where one does not actually exist.
Performance of Horizontal Wells Subject to Bottomwater Drive
Authors: Ozkan Erdal , Raghavan Rajagopal
Published: December 2007

This paper discusses the performance of a horizontal well subject to bottomwater drive and delineates conditions under which this completion mode is more appropriate. Information presented will enable the engineer to decide what productivity improvements may be expected from horizontal-well completions. The productivities of horizontal wells operating under bottomwater drive are discussed in terms of displacement efficiencies. Results and the discussions are also applicable to oil production by gas-cap drive.
Estimation of Multiphase Flow Functions From Displacement Experiments
Authors: Richmond P. C. , Watson A. T.
Published: December 2007

A recently developed implicit estimation procedure (or regression-based method) that uses parameter estimation with B-spline functional representations can determine essentially unbiased estimates of relative permeability functions from dynamic displacement data. In this paper, we extend this method to estimate relative permeability simultaneously with capillary pressure functions. Careful consideration is given to the functional representation of the relative permeability and capillary pressure functions so that the most accurate estimates of these properties can be obtained. These procedures are demonstrated with laboratory dynamic displacement data.
New Makeup Method for API Connections
Authors: Day James B. , Moyer Mark C. , Hirshberg Alan J.
Published: December 2007

A new method of connection makeup was developed to provide a leak-free seal up to rated working pressure and tension for API 8-round casing and tubing threads. For many years, industry has used various torque-only and torque-turn techniques to make up these threads. Current industry needs and regulatory test requirements are raising the pressure-sealing needs and tensile-load requirements for drilling and production tubulars. This new method, torque-position, accounts for variances in thread tolerances, coupling coating or plating, and thread compound. Advanced finite-element computer modeling helps to establish key makeup parameters. This paper discusses the problems with current makeup methods and evaluates the new method, including its field application for casing and tubing.
A New Method of Continuous Thermodynamics Applied in an Equation of State
Authors: Halpin T. P. J. , Quirke Nick
Published: December 2007

Continuous thermodynamics, in which a fluid's composition is regarded as a continuous function rather than as a set of discrete mole fractions, has been applied to petroleum fluids in a number of forms. The method provides a practical alternative to pseudocomponent methods in phase-equilibrium calculation with an equation of state (EOS). Current continuous-thermodynamic methods are limited by the functional form assumed for the composition; they are unable to retain a continuous description of all phases in the calculation while preserving material balance.

A new functional representation of continuous mixtures based on an orthonormal expansion is proposed that preserves material balance between phases and provides a versatile composition description. With such a representation, the conditions for phase equilibrium are shown to be of a simple form. Because these conditions are similar to those for a discrete composition, phase equilibrium can be calculated in much the same way. The method's accuracy approaches that of a calculation in which the composition is fully represented by a large number of discrete components. The computer time requirement, however, is far less because only a small number of terms must be retained in the expansion series. Use of this new method is demonstrated for petroleum mixtures with a modified Soave EOS.
Effects of C02 Addition to Steam on Recovery of West Sak Crude Oil
Authors: Hornbrook M. W. , Dehghani Kaveh , Qadeer Suhail , Ostermann R. D. , Ogbe D. O.
Published: December 2007

A high-pressure ID laboratory displacement study evaluated the effects of adding CO2 to steam on the recovery of West Sak crude oil. Results of the laboratory experiments indicate that the simultaneous injection of CO2 and steam increases recovery, reduces injection temperatures, and reduces the heat input required.
A Fully Implicit Thermal Wellbore Model for Multicomponent Fluid Flows
Authors: Siu A. L. , Rozon B. J. , Li Y.-K. , Nghiem L. X. , Acteson W. H. , McCormack M. E.
Published: December 2007

This paper describes a thermal wellbore model that simulates flow hydraulics in the wellbore and heat transfer between the wellbore fluid and the overburden. The thermal wellbore model includes the transient differential equations for multicomponent three-phase fluid flow in the wellbore and the transient heat conduction equation in the overburden. Phase behavior of the wellbore fluids is obtained from isenthalpic flash calculations, which compute the phase splits and compositions at a specified pressure and enthalpy. The wellbore and overburden equations in the entire discretization domain are solved simultaneously with a fully implicit Newton's method. The thermal wellbore model was validated with steam-injection and gas-condensate production field data. The calculated heat losses and pressure drops compared favorably with published models. The thermal wellbore model is also used to predict the critical production rate of methane above which hydrate will not form.
A Laboratory Investigation of Foam Flow in Sandstone at Elevated Pressure
Authors: Persoff Peter , Radke C. J. , Pruess Karsten , Benson S. M. , Witherspoon P. A.
Published: December 2007

This paper describes a study made of the flow of foam through sandstone at elevated backpressures. Gamma ray attenuation was used to measure local liquid saturations. Steady-state pressure gradients for foam were found to be essentially independent of gas velocity but nearly proportional to liquid velocity. This flow behavior of foam is explained in terms of changes in bubble texture.
Steam-Zone Electrical Characteristics for Geodiagnostic Evaluation of Steamflood Performance
Authors: Mansure A. J. , Meldau R. F.
Published: December 2007

An essential part of the development of electrical geodiagnostic techniques for mapping thermal recovery processes is understanding the relationship of formation resistivity to the thermal recovery process. As a result of laboratory measurements of a 1D steamflood, a preliminary understanding of some of the mechanisms of the electrical resistivity change has been gained. The theory of electrical resistivity of a steamflood is reviewed and used to evaluate the resistivity changes expected. A conceptual electrical model of a steamflooded porous reservoir, based on a qualitative description of the fluid zones of an ideal heavy-oil steamflood, is presented. The model assumes that salinity, temperature, and saturation are the important factors controlling resistivity changes and that Archie's law applies. We found that the characteristics of each individual reservoir must be considered before the in-situ resistivity changes are predicted and that in-situ resistivity can either increase or decrease as a result of steamflooding.