bluuebunny/crossref_metadata_2025 huggingface dataset:
Casing Wear During Drilling: Simulation, Prediction, and Control
Authors: Schoenmakers J. M.
Published: December 2007

Four case studies show that laboratory simulations of casing wear caused by rotating tooljoint hardfacings correspond very well to field-measured casing wear. Moreover, the work reveals concentrations of casing wear at the kickoff point of a deviated well and near casing collars. Drillpipe/casing protectors do not always appear effective in avoiding casing wear. It is concluded that prediction of casing wear is possible with laboratory simulations, and that casing wear can be controlled by sufficiently smooth hardfacings, weighted mud, and moderate tooljoint/casing contact forces. An inspection technique can be used to qualify hardfacings for use in casing. Hardfacings that are machined to meet the smoothness requirement are commercially available.
Predicting Bottomhole Assembly Performance
Authors: Williamson J. S. , Lubinski A.
Published: December 2007

A computer program for prediction of bottomhole assembly (BHA) performance has been developed. Input parameters include formation dip angle, hole and collar size, and stabilizer spacing. The predictions are in drilling terms: hole curvature, hole angle, weight on bit (WOB), etc. Results of extensive parametric studies and field use are presented.
Downhole Control of Deviation With Steerable Straight-Hole Turbodrills
Authors: Gaynor T. M.
Published: December 2007

Advances in directional drilling have until recently been confined to issues that are peripheral to the central problem of controlling assembly behavior downhole. Examples of these advances are measurement while drilling (MWD) and the increasing use of computer assistance in well planning. These were significant steps forward, but the major problem remained. Changes in formation deviation tendencies led to trips to change bottomhole assemblies (BHA's) to cope with the new conditions. There is almost no direct control of deviation behavior.

The steerable straight-hole turbodrill (SST) addresses this problem directly, allowing alteration of the well course without the need to trip. The availability of such a system radically changes the way in which directional well planning may be approached. This paper describes the equipment used and the equipment's construction and operational requirements. It discusses the capabilities and current limitation of the systems. Field results are presented for some 300,000 ft [91 500 m] of deviated drilling carried out over 2 years in Alaska and the North Sea. A series of four highly deviated wells totaling 35,000 ft [10 700 m] with only three deviation trips is included.

The SST is the first deviation drilling system to achieve deviation control over long sections without tripping to change BHA's. Bits and downhole equipment are now more reliable and long-lived than ever; therefore, deviation trips are becoming a major target for well cost saving.
Computer Processing Improves Hydraulics Optimization with New Methods
Authors: Gavignet A. A. , Wick C. J.
Published: December 2007

In current practice, pressure drops in the mud circulating system and the settling velocity of cuttings are calculated with simple rheological models and simple equations. Wellsite computers now allow more sophistication in drilling computations. In this paper, experimental results on the settling velocity of spheres in drilling fluids are reported, along with rheograms done over a wide range of shear rates. The flow curves are fitted to polynomials and general methods are developed to predict friction losses and settling velocities as functions of the polynomial coefficients. These methods were incorporated in a software package that can handle any rig configuration system, including riser booster. Graphic displays show the effect of each parameter on the performance of the circulating system.
A Drilling Model for Young Offshore Louisiana and Texas Trends
Authors: Smalling D. A. , Myers R. L.
Published: December 2007

A new type of model specifically designed to aid in the planning and drilling of young offshore Louisiana and Texas wells is presented. The model is composed of functions to represent changing drilling mechanics, as well as changing drillabilities with respect to depth, area, and formation type.
Unique Marine Craft Moves Rigs with Speed and Economy at Lake Maracaibo
Authors: Kunzi Robert E.
Published: December 2007

During the past three years, Creole Petroleum Corp. has used a highly specialized marine craft to move unitized drilling rigs in its Lake Maracaibo, Venezuela, oilfield operations. This paper describes the development, construction, operation and economics of Creole's "floating fork-lift". The marine rigmover has proven to be a practical and economical device, and it could be used in any large-scale oilfield development program in deep inland or sheltered ocean waters.

Introduction

The great majority of Creole Petroleum's concessions in Western Venezuela lie beneath the waters of the northeast quadrant of Lake Maracaibo. Lake Maracaibo is a large, pear-shaped, fresh-water lake about 100-miles long and 60-mile wide with a maximum water depth of 125 ft and an over-all average depth of about 40 ft. All of the company's lake wells have been drilled from permanent, concrete-pile platforms. These platforms support the rig substructure, a standard-type derrick, the draw-works and the drill string. Lateral-sway bracing is the only connection between the casing strings and the well platform. Mud pumps, pipe racks, auxiliary equipment and materials storage are located on an anchored barge-tender. Almost all of Creole's earlier wells in the lake were equipped with a standard derrick which was left in place on completion of the well in order to be utilized in future repair jobs. It was felt that the capital outlay for many derricks was less than the expense required to erect and dismantle a derrick for each repair job during the life of a well. In 1955, Creole's management authorized a study of the derrick and rig-moving problem to determine if there was a faster, more economical method of handling the job. Creole's goal was to replace the old method of rig moving-that is, piece-meal movement of the rig-with a more efficient unitized method. This goal was attained in the development of a "U"- shaped, self-propelled craft which can maneuver around the well platform, pick up the rig-derrick package, move to the next location, and then place the unit on the new foundation (see Figs. 1 and 1A). Even though over one and three-quarter million dollars have been invested in the rigmover and its associated substructures, the savings realized through the use of this equipment paid out the investment in Nov., 1961.

Development History

As early as 1951, Creole was making over-water rig moves similar in principle to those made by the rigmover. The original "straddle barges" unit was designed for use in the Pedernales field, located in the tidal channel area of the Orinoco river delta in Eastern Venezuela. It consisted of two barges supporting a one-piece substructure complete with draw-works, engines and derrick. The drilling unit was placed by straddling the new pile foundation with the two barges and then lowering the rig by controlled flooding of the barges. The moves were also timed to take advantage of the tidal differences in water level. Mud pumps and pipe racks were aboard a barge tender.

JPT

P. 228^
Soluble Fluid-Loss Additives Can Reduce Well Productivities and Prevent Complete Gravel Placement
Authors: Sparlin D. D. , Hagen R. W.
Published: December 2007

Fluid-loss additives are frequently used in completion fluids and pills to reduce fluid costs and formation damage, but many of these additives create more damage than they prevent. Common recommendations are to use fluid-loss additives that will be dissolved by the produced fluids, acid, or water so that they may be readily removed after a job. Typical additives are oil-soluble resins, calcium carbonate particles, and salt suspensions.

It is particularly important that soluble additives be used for wells that are to be gravel packed because the gravel will trap insoluble solids in the well. Evidence indicates, however, that even these soluble products remain in perforation tunnels and impair productivities of wells. Examples of wells indicating this effect during post-gravel-pack acid treatments are discussed. The theory of why this occurs and calculations of pressure drops through perforations filled with fluid-loss additives are presented.

It has also been found that excess fluid-loss additives prevent complete coverage of a zone with gravel, because of either inadequate leakoff to the formation or partial plugging of the screen. Therefore, it is imperative that these additives be removed by acid, water, or solvents preceding the gravel slurry; however, if their removal causes loss of circulation, the results may be equally bad.

The most practical solution to this problem is to use a combination of gravel and viscous fluids as a diverting system for the fluids that will remove the additives without creating additional formation damage. When this system is used just ahead of a gravel slurry, it not only helps remove the fluid-loss additives, but also helps prevent excessive fluid losses and partially prepacks the formation with gravel.
Core Cleaning for Restoration of Native Wettability
Authors: Gant Preston L. , Anderson William G.
Published: December 2007

Certain additives used in drilling and completion fluids may alter the wettability of core. For example, the surfactants in invert-oil-emulsion drilling muds are known to alter the wettability of core. Because routine cleaning methods do not remove these surfactants, core that is to be used for special laboratory analyses, such as relative permeability, capillary pressure, and saturation exponent, is left with an altered wettability. Experiments with such core will obviously produce erroneous data. To obtain reliable results, cleaning methods must be developed to remove these surfactants, allowing restoration of plugs to their natural wettability. Once the core is cleaned, the wettability of the cleaned core can be restored by saturating with synthetic formation brine and uncontaminated reservoir crude, then aging at the reservoir temperature.

This report ranks the efficiency of solvents in removing surfactants from plugs contaminated with invert-oil-emulsion drillingmud filtrate. Eight solvents for Berea sandstone and seven solvents for Guelph dolomite have been ranked after Dean-Stark extraction of mud surfactants using the U.S. Bureau of Mines (USBM) wettability index. The best solvent for both rock types was a 50/50 mixture of toluene/methanol, or the equivalent, containing 1% ammonium hydroxide. Toluene, the most commonly used solvent for core cleaning, was one of the poorest solvents tested. The solvents that are effective in removing surfactants can be used to clean contaminated core.
The Concept of Relative Ganglion Velocity and Generalization to Oil-Bank Movements in Porous Media
Authors: Egbogah Emmanuel O.
Published: December 2007

This paper discusses a simple computational technique for determining relative ganglion velocity in a pore and its implication to the formation and propagation of an oil bank. The approach is based on a simple theory of the movement of a discontinuous oil droplet (ganglion) through a model pore. The analysis, based on a simplified conical geometric model, permits the development of expressions for relative ganglion velocity (velocity of the oil ganglion relative to the bulk liquid velocity) under various flow conditions. This parameter is essential for modeling waterflooding and/or EOR processes and facilitates the prediction of oil-bank movements. An example calculation illustrates the application of the concept. Results of the calculations indicate that faster oil-bank movements are attained when interfacial tensions (IFT's) are low and pressure gradients are high.
A Correction for the Effect of Comminution on the Cation Exchange Capacity of Clay-Poor Sandstones
Authors: Huff G. F.
Published: December 2007

It is well known that comminution (decrease of particle size by grinding) can increase the cation exchange capacity (CEC) of geologic materials. Because comminution is often a "first step" in sample preparation, it is desirable to be able to correct for comminution-induced effects.

The relative increase in CEC of poorly lithified clay-poor sandstones and better-lithified shaly sandstones from Caño Limon Well 3 and La Yuca Well 6, Llanos basin, Colombia, correlated well (r≥0.97) with the square root of the duration of sample comminution. A method based on this correlation has been developed to correct for comminution-induced increases in the CEC of poorly lithified clay-poor sandstones. The method was also applied to the better-lithified shaly sandstones with good results.

The rate of relative increase of the CEC with comminution showed an inverse correlation with the total weight percent clay in a specimen. This suggested that much of the increase of the CEC of the specimen was caused by an increase in the CEC of quartz, which was the dominant mineral in these rocks.
Resolving Pore-Space Characteristics by Rate-Controlled Porosimetry
Authors: Yuan H. H. , Swanson B. F.
Published: December 2007

By monitoring the mercury capillary pressure in rate-controlled porosimetry (intrusion) experiments, new information regarding the pore space of a rock sample has been obtained. With this technique, called an apparatus for pore examination (APEX), it is now possible to resolve the pore space of a rock sample into two interconnected parts. One part identifies the individual pore systems (pore bodies), which are low-energy sumps or regions of low capillarity. The other part corresponds to the pore throats that interconnect with pore systems.

New capillary-pressure curves have been obtained by partitioning the total capillary-pressure curve (normal capillary-pressure curve) into two subcurves: the subison capillary-pressure curve, which details the distribution of pore bodies, and the rison capillary-pressure curve, which details the distribution of pore throats. We present APEX data on Berea sandstone and San Andres dolomite that show the volume distribution of low-capillarity regions within the pore space of these rocks. These regions of low capillarity are the principal pore-space regions that trap the residual nonwetting phase upon imbibition of a strongly wetting fluid, as measured by toluene/air systems. The residual nonwetting-phase saturations as determined by the APEX method and by the toluene/air method are in excellent agreement. Thus, the detailed volume distribution of pore systems responsible for trapped nonwetting-phase saturation is determined from APEX measurements, which can have important implications for EOR.
Mechanistic Study of Gravity-Assisted CO2 Flooding
Authors: Tiffin D. L. , Kremesec V. J.
Published: December 2007

A series of gravity-assisted vertical core displacements of contact-miscible and multiple-contact-miscible CO2/recombined-crude-oil systems was conducted and simulated. Gravity-assisted displacements offer the advantages of eliminating gravity tongues and stabilizing viscous fingers. Although the process has been used successfully in the field, a mechanistic laboratory and modeling study of gravity-assisted multiple-contact-miscible CO2 flooding has not been described previously.

The results from this experimental and computer modeling study elucidate the complex mechanisms acting in gravity-assisted CO2 flooding. Component transfer, as occurs in multiple-contact-miscible processes, can strongly affect flood-front stability. In general, better performance is obtained from vertically downward displacements than from comparable displacements in horizontal cores. Miscibility develops at the same pressure in vertical floods and in a much shorter core length. It was further demonstrated that displacement efficiency increases at conditions where mixing of CO2 and oil is minimized. Excellent simulation of experimental recoveries and rates were obtained with a compositional simulator in a one-dimensional (1D) mode.
Diffusion of CO2 at Reservoir Conditions: Models and Measurements
Authors: Grogan A. T. , Pinczewski V. W. , Ruskauff Gregory J. , Orr F. M.
Published: December 2007

Mathematical models are developed to describe the transport of dissolved CO2 in a liquid phase, and results of measurements of the diffusivity of CO2 in hydrocarbons and water at reservoir conditions are reported. The measurements were made with novel techniques based on the direct observation of the motion of an interface caused by the diffusion of CO2 through oil or oil shielded by water. Diffusion coefficients were determined by fitting the mathematical models to the observed motion of the interfaces. This method allows the measurement of diffusion coefficients without the need to determine phase compositions and is therefore suited to measurements at elevated pressures (reservoir conditions). Measured diffusion coefficients are reported for CO2 in pentane, decane, and hexadecane at 25°C [77°F] and pressures up to 6000 kPa [870 psia]). Limited measurements of CO2 diffusion in Maljamar crude oil are also described. In addition, results of measurements for the diffusion of CO2 in water are presented. These are the first such measurements at high pressures (up to 6000 kPa [870 psia]). Correlations of diffusion coefficients in liquids at atmospheric pressure are shown to give reasonable estimates of diffusion coefficients for CO2 in fluids at reservoir conditions. Finally, the measured diffusion coefficients and mathematical models are used to assess the impact of diffusive mixing on CO2 floods at various length scales to examine the relationship between laboratory-scale corefloods and field-scale displacements.
Hydrolytic Stability of Alkylethoxy Sulfates
Authors: Talley Larry D.
Published: December 2007

Sulfate surfactants are being proposed by industry for use in moderate-temperature surfactant floods. Sulfates are also being considered by some groups for use in CO2 mobility control and surfactant/alkaline floods. Data from this study show that the maximum applicable temperatures for sulfates under these pH conditions are much lower than for neutral pH conditions. Rate equations are derived from Arrhenius data on the basis of observed decomposition mechanisms. The equations are used to calculate surfactant lifetimes and maximum temperature limits at various reservoir conditions. The maximum temperatures and lifetimes are functions of pH and brine composition.
The Use of Semicontinuous Description To Model the C7+ Fraction in Equation of State Calculations
Authors: Behrens R. A. , Sandler S. I.
Published: December 2007

A semicontinuous thermodynamic description has been used to model the C7+ fraction for equation of state (EOS) calculations. This semicontinuous description may be used in existing discrete-component EOS programs by picking pseudocomponents in a rigorous a priori fashion dependent only on the properties of the C7+ fraction. Excellent representation of experimental PVT data considered here is obtained with only two C7+ pseudocomponents, although the theory and procedure extend to three or more components.
The New Frontier
Authors: Pyle Howard C.
Published: December 2007

Americans were born of a revolution. We are the custodians of a tradition and a practice of liberation and of freedom. We have never lost our proud independence and individuality, and we never will. We can take care of ourselves and our families and we know it. Traditionally, when we felt confined and became restless, we moved farther west. There had always been a frontier out there and a new way of life. Where do the young men of today go with their strong independence and eager self-reliance? Their interest and ours must become the whole world. Our frontier is broadened; it is everywhere.

U. S. Leads Free World in Peace

Two world wars and the constant threat of a third one makes us ever conscious of our neighbors. World-circling satellites draw all countries closer together. The wealth and industrial might of the United States has resolutely placed us in the position of world leadership. This is the new frontier; leadership in a free world at peace.

America has become great because on one basic philosophic idea - the idea that we can improve the lot of our people without interfering with their civil liberties. We recognize the essential dignity of man. Needless to say, there are opposing ideas in the world today, ideas that the individual exists for the sake of society and the state alone. We know that our awareness of the individual importance of man is right, and we must demonstrate to others that this is true. To accomplish this, we must all increase our social obligations. This is a practical reaction to the now basic fact, which becomes more insistent every day, that no public or private purpose can be sensibly considered apart from world affairs.

The world is faced with enormous possibilities of growth. Man is at last breaking with the past. Our problems are not only greater, they are new. The limitations and safeguards our forefathers counted on are gone. We can not hide. We can no more ignore the threat posed by atomic or thermonuclear warfare than we can a recession or inflation. These threats are not simply scientific or government problems, they are our problems, yours and mine. They will not disappear by just being ignored, and they will not be resolved by using old rules of thumb.

We should all help form world opinion, both as individuals and as a free and enterprising nation. As engineers and professional men we should be particularly active, and we must be heard from. With our new United Engineering Center we are becoming a neighbor to United Nations. What better reason could we have for becoming more conscious of world activities, followed by becoming participants in world affairs?
Flow Visualization of the Effects of Interfacial Tension on Displacement
Authors: Hornof V. , Morrow N. R.
Published: December 2007

The effects of interfacial tension (IFT) on displacement behavior have been investigated through flow visualization experiments in porous media formed by thin layers of sintered glass beads. Fluid densities and viscosities were matched to avoid viscous and gravitational instabilities. Displacements were carried out with aqueous/oleic liquid pairs, which gave IFT’s of 17.0, 1.2, 0.029, and 0.002 dynes/cm [17.0, 1.2, 0.029, and 0.002 mN/m]. Results show how IFT, wettability, and model heterogeneity interact to determine the shape and stability of the displacement front.
Surfactants for EOR: Olefin Sulfonate Behavior at High Temperature and Hardness
Authors: Bavière Marc , Bazin Bridgltte , Noïk Christine
Published: December 2007

The surfactant properties usually required for EOR are investigated with alpha-olefin sulfonates (AOS’s), particularly at high temperature, salinity, and hardness, together with their solubility in brine, chemical stability, phase behavior, and adsorption.

The use of a cosolvent enables aqueous solutions to be prepared with concentrated brine, even at high divalent cation levels. But the chemical stability of some solutions can be affected by their sensitivity to the oxidation of unsaturated components, resulting in a decrease of the pH. Precautionary measures to stabilize the solutions are stressed–i.e., anaerobic environment, maintenance of an alkaline pH, or addition of alcohol. As already shown, these surfactants provide low interfacial tensions (IFT’s) and high solubilization parameters at high salinity and divalent cation content. Properties of optimal formulations have been investigated as a function of surfactant and cosolvent molecular weight and brine composition.

Adsorption data on Na− and Ca− kaolinite are presented. In NaCl solutions, the amount of sulfonate adsorbed increases slightly with salinity. Preliminary measurements in hard water are shown to bring out the specific effect of calcium ions. According to the results concerning properties validly considered as screening criteria, we conclude that this family of sulfonates appears to be a potential candidate for EOR.
Fractional-Flow Model for High-pH Flooding
Authors: Ramakrishnan T. S. , Wasan D. T.
Published: December 2007

A model based on the fractional-flow theory is developed for the enhanced recovery of acidic crude oil with caustic as the alkaline agent. The model incorporates earlier work on fluid/fluid interactions of acidic-crude-oil/caustic systems, which provides not only the chemical reaction equilibria but also the interfacial tension (IFT) as a function of composition. The lowering of IFT as a result of in-situ-generated surface-active agent enhances the viscous-to-capillary-force ratio, which is presumed to be the cause of the alteration in relative mobilities of oleic and aqueous phases. The complete set of species-conservation equations forms a system of three quasilinear partial-differential equations that is reducible in the generalized sense. The system is solved by the method of generalized Riemann invariants. The effect of such parameters as viscosity ratio, reference capillary number, injected fluid pH, and salinity is computed with properties of Long Beach crude. New features that arise from the influence of the optimum region when an overoptimum composition is injected are identified. On the basis of composition paths, it is shown that the optimum regions play a dominant role in the process and that the IFT between the injected solution and the crude has no direct bearing on ultimate oil recovery. Simple graphic procedures that afford quick construction of solutions are shown to be possible.
An Update of the Polymer-Augmented Alkaline Flood at the Isenhour Unit, Sublette County, Wyoming
Authors: Doll Thomas E.
Published: December 2007

An Almy sand polymer-augmented alkaline flood at the Isenhour Unit, Sublette County, WY, is reviewed. This paper updates process technology, including the use of clay stabilization, sweep improvement, soda ash alkaline agent [to reduce interfacial tension (IFT) and mobilize residual oil], and anionic-polymer-blend mobility buffer. Oil production has been increasing at 20%/yr since the process start.
Drilling With a One-Step Solids-Control Technique
Authors: Hayatdavoudi A.
Published: December 2007

The objectives of this paper are to report a new philosophy in solids control and field practice, referred to as fluid conditioning, to make a comparative evaluation of surface solids-control equipment, and to show details of a comprehensive mineralogical and physicochemical analysis of removed solids.

For brevity, only a few field results are emphasized. For example, in a weighted mud system of 15.2 lbm/gal [18.2 × 102 kg/cm3], the adjustable concentric device of fluid conditioner rejects a greater percentage of 0.5- to 1.0-μm solids than a centrifuge. In an unweighted mud system of 9.5 lbm/gal [11.4 × 102 kg/m3], fluid contaminants such as calcite, dolomite, and salt are rejected through underflow. Another field example based on microscopic and scanning electron microscopic (SEM) size analysis showed that in a 12-lbm/gal [14.4 × 102-kg/m3] mud system, it is necessary to increase the operating pressure by a few psi to reduce the amount of 6-μm material.

Our research in the area of particle size analysis of small, oilfield particles—e.g., smectite, sepiolite, Wyoming bentonite, and barite from bags of dust collectors—reveals that a quick-fix Fraunhofer diffraction analysis in the range of 10 μm and less is totally invalid in quantitative works.

Finally, through the analysis of fluid rejects, we concluded that after the rig shaker (assuming that the rig shaker performs well), the one-step solids-control fluid conditioning can deliver desirable rheological properties and a reasonable size range for the suspended material.
Ultra-High-Pressure Tubing-Retrievable Annular Safety Valve
Authors: Morris A. J. , Pringle R. E.
Published: December 2007

Ultra-high-pressure (15,000- to 20,000-psi [103.4- to 137.9-MPa] working pressure), deep, hot gas well completion techniques currently have limited capabilities. Environments encountered at these pressures normally have H2S concentrations of 5% or more at temperatures higher than 400°F [204°C] with CO2 also present.

Using new metal sealing technology recently developed for tubing-retrievable safety valves for ultra-high-pressure production service1 combined with a casing polished-bore-receptacle (PBR) concept provides a simple solution in total well control. This annular-control safety valve is placed in the PBR as an integral part of the production string, complemented by a tubing-mounted safety valve for tubing-production control. Both valves are operated by hydraulic control lines to the surface as in standard safety-valve operations.
Reverse Combustion - A New Oil Recovery Technique
Authors: Perry Robert H. , Green Don W. , Campbell John M.
Published: December 2007

Although the broad recovery method known as underground combustion embodies many related techniques, principle attention has been focused on alternatives known as "forward" and "reverse" combustion. Summaries follow in this issue for three Technical Publications on reverse combustion, and it is the purpose of this article to briefly review in situ combustion and to introduce the subject of reverse combustion.

Secondary recovery by underground combustion is a most intriguing method which provides energy and material transport through porous media. The "heat wave" effectively reduces the viscosity of the driven oil and thus, for many crudes, dramatically increases its fluidity. The material transport ahead of the heat wave acts as a miscible fluid drive. The result is a very efficient sweep of residual oil from the area.

Our fundamental knowledge about the process is limited, however, except in a general way; thus, detailed engineering recommendations are difficult. It must be remembered that exceedingly complex cases of multiphase fluid flow, multi-dimensional and multi-mechanistic heat transfer, heterogeneously catalyzed reaction kinetics, and multi-component phase equilibria are all combined in this process in a mutually dependent manner. It is no wonder that our scientists have barely scratched the surface in understanding the in situ combustion process.

Both forward and reverse combustions utilize as fuel the residual coke from the in-place oil. The difference between the techniques is whether the flame front and material flow are in the same direction (forward combustion) or in opposite directions (reverse combustion). A simple analogy may be used to clarify the difference.

Picture yourself smoking a cigarette in the conventional manner. The flame front and the products of combustion both travel toward your mouth (forward combustion). If you blow into the cigarette, however, the products of combustion travel outward while the flame front still moves toward your mouth (reverse combustion). Thus, in forward combustion both oil and the heated zone are moving toward the producing well and away from the injection well, while in reverse combustion the flame front moves away from the producing well.
Unsteady-State Distributions of Fluid Compositions in Two-Phase Oil Reservoirs Undergoing Gas Injection
Authors: McFarlane Robert C. , Mueller T.D. , Miller F.G.
Published: December 2007

During the process of gas storage in pressure-depleted oil reservoirs, it has been observed that in some instances additional liquid oil is recovered and that the composition of the storage gas is materially altered. A mathematical study was made of the dynamic behavior of such a depleted oil reservoir undergoing gas injection. The important variable considered in this study, not included in previously published work, was that of compositional effects on the phase behavior of two-phase flow. Pressure, saturation and component composition profiles were developed for a linear, horizontal and homogeneous porous medium containing oil and gas but undergoing dry gas injection. Special new techniques were developed to overcome the problems of numerical smoothing which arise in the solution of the equations representing such systems.

The method of solution includes the development of partial differential equations describing the behavior of the system, representing these equations by finite difference approximations, making certain simplifying assumptions and, finally, applying methods of numerical analysis with the aid of a high-speed digital computer.

In an example calculation, results using the mathematical model are compared with field observations made on a gas storage project in Clay County, Tex. This field project involved a depleted oil reservoir used' for gas storage and gas cycling purposes. As a result of these processes, the reservoir yielded substantial amounts of secondary oil, both in the form of stock tank oil and as vaporized products in the produced gas. The methods derived in this study may be applied to a variety of oil reservoir problems which are dependent on compositional effects.

INTRODUCTION

In recent years the number of oil reservoirs being used for gas storage purposes has increased greatly, and there has been at least one published account of additional oil recovery resulting from gas cycling a depleted oil reservoir after repressuring with dry gas for storage purposes. Additional oil recovery from oil reservoirs resulting from gas storage operations could become an important secondary recovery process. This is especially true since the use of natural gas in large metropolitan areas continues to increase and more gas storage volume near these areas is needed.

These facts provided the motivation for the work reported here. This paper reports on a study of the inter-relations of composition, saturation and pressure changes which occur when hydrocarbon gas is injected into an oil reservoir system. From an understanding of the process, prediction methods may be developed for use in forecasting the secondary recovery products from gas storage operations in oil reservoirs and, consequently, .the economics of such projects can be developed.
Completion Design for Waterfloods and CO2 Floods
Authors: Stone P. C. , Steinberg B. G. , Goodson J. E.
Published: December 2007

A completion design is used to complete a well for production or injection operations. It comprises the planned wellhead, tubing and casing, downhole equipment, and treatment (chemical or stimulation). This paper examines the criteria for selection of tubing and downhole equipment used in waterflood and CO2-flood completions. This paper reviews corrosion problems, material options, commonly used packers/accessories, and the influence of CO2 injection on the selection process.
Borehole Televiewer Improves Completion Results in a Permian Basin San Andres Reservoir
Authors: Clerke E. A. , Van Akkeren T. J.
Published: December 2007

The borehole televiewer (BHTV) is an acoustic logging tool that has a fine vertical resolution (⅓ in. [8.5 mm]) that is extremely useful for detecting bedding orientation, thin high-permeability zones, lithology changes, and zones of secondary or vuggy porosity. BHTV logs were acquired from 10 wells during the recent infill drilling of the North Hobbs (Grayburg/San Andres) Unit. These logs, when correlated with conventional logs and core data, have improved completion strategies, resulting in higher oil and lower water production in new infill wells.
Applications of Nuclear Science in Petroleum Production
Authors: Williams Milton
Published: December 2007

Introduction

To aid in solving the many problems with which it is faced, the petroleum industry long has been accustomed to rely on the research which it conducts at its own expense and to adapt to its particular needs the results of research which originates in other fields. Just as it has been able to put to its own uses many other scientific advances, so the petroleum industry has drawn freely on developments in nuclear science to provide new tools, methods and knowledge designed to aid in the search for petroleum and in the production of oil and gas.

At the outset, it must be understood that, to date, there has been no application of nuclear science which may be said to have revolutionized the petroleum industry's operations. It is true, however, that nuclear science has made numerous, distinct contributions to the industry in a number of ways and that this multiplicity of applications represents, in the aggregate, a very real advance.

Geochronology

Illustrative of the way in which developments in nuclear science can be of benefit in petroleum exploration is the application of age-dating to the sediments drilled in the search for petroleum.

Since the early days of radioactivity, there has been an interest on the part of the geologist in dating strata in an absolute chronology by use of various radioactivity decay schemes. Joly, Rutherford, and their contemporaries laid the ground-work many years ago by use of uranium-lead, thorium-lead and uranium-helium methods in which the relative amounts of "parent" and of "daughter" were determined by chemical analysis alone. As the years have passed, more decay systems have been exploited, and more highly sophisticated methods have been brought to bear on the accurate determinations of parent and daughter which are required for precise dating. Today, there is a wealth of literature on the subject, and additional research is being carried out in many places which is designed to make more accurate the determination of age.
Prediction of the Minimum Miscibility Pressure of a Vaporizing Gas Drive
Authors: Nouar A. , Flock D. L.
Published: December 2007

A method is proposed to estimate the minimum miscibility pressure (MMP), pmm, of a vaporizing gas drive with a lean hydrocarbon gas on the basis of the thermodynamic properties of the displacing and displaced fluids. The determination of pmm is based on the phase behavior of the system of fluids considered. Thermodynamic criteria have been set forth for the case of ternary systems. The method is very easy to use and is intended for the case of a vaporizing gas drive by a very lean hydrocarbon gas—i.e., composed principally of methane.
Measurements and Correlations of the Physical Properties of CO2-Heavy Crude Oil Mixtures
Authors: Chung Frank T.H. , Jones Ray A. , Nguyen Hai T.
Published: December 2007

Viscosity reduction and swelling are the principal mechanisms contributed to the improvement of heavy-oil recovery by immiscible CO2 displacement. This paper presents the results of experimental measurements for the physical properties of heavy oils before and after CO2 saturation. Based on measured data, correlations were developed for the predictions of CO2 solubility, oil swelling factor, and viscosity change for CO2-saturated heavy oils.
Interpretation of Radioactive Tracer Results in a Steamdrive Project
Authors: Heisler Robert P.
Published: December 2007

Reservoir radioactive tracer programs have historically been viewed as obtaining speculative reservoir information because of the low recovery efficiencies of the injected isotopes. This case study presents the results of a steamdrive, multi-isotope program that recovers as much as 50% of the injected radioactivity. The ability to trace both the steam and liquid water phases simultaneously, at high concentrations, enables a material balance to be performed on the isotopes. The resultant interpretation quantifies the developed interwell communication and steam zone sizes while qualitatively providing an appreciation of the control that well operations have on reservoir fluid movements.
Prediction of Slug Length in Horizontal, Large-Diameter Pipes
Authors: Scott Stuart L. , Shoham Ovadia , Brill James P.
Published: December 2007

The prediction of slug characteristics for large-diameter pipes is studied with data collected from flowlines in the Prudhoe Bay field in Alaska. A 3-mile [5-km] -long pipeline was fully instrumented with nuclear densitometers, insert turbine meters, flowmeters, pressure and temperature sensors, and separator level indicators. During these tests, more than 19 million data points were collected on 12-, 16-, 20-, and 24-in. [30-, 41-, 51-, and 61-cm] -diameter pipes. These data were used to construct a data base that can be accessed interactively or by FORTRAN applications programs. The data show such slug characteristics as slug length, bubble length, and holdups. Data analysis revealed that the liquid slugs do not maintain a constant length and that the slugs tend to grow as they flow through the pipeline. An existing slug-length correlation was modified with these new data, and a term was added to account for the observed slug growth.
An Improved Streamline-Generating Technique That Uses the Boundary (Integral) Element Method
Authors: Numbere D. T. , Tlab D.
Published: December 2007

The boundary element method (BEM) has been used to generate streamlines for homogeneous and sectionally homogeneous reservoirs having irregular boundaries. This technique is superior to earlier methods that use "image wells" to simulate the reservoir boundary, especially for cases where the reservoir boundary is irregularly shaped. It has wider applicability to different kinds of reservoirs and eliminates the need for trial-and-error solutions. The errors caused by discretization and numerical approximation arise on and adjacent to the boundaries only, therefore the pressures and pressure gradients on which the streamlines are derived can be calculated with very high accuracy in the interior of the reservoir. Thus, the streamlines generated with this method are expected to be more realistic and representative of the actual physical system.
Study of Multiphase Critical Flow Through Wellhead Chokes
Authors: Surbey D. W. , Kelkar B. G. , Brill J. P.
Published: December 2007

Use of wellhead chokes to monitor and control well flow rates and to protect the reservoir from surface pressure fluctuations is quite common. This study investigates the use of multiple-orifice-valve (MOV) chokes in the critical-flow region.

Experimental data collected for a high-pressure air/water system show that conventional relationships are not successful in analyzing the experimental data for MOV chokes. A new relationship based on the sonic velocity of two-phase homogeneous mixtures is developed for the prediction of the critical-flow transition. The procedure uses choking, rather than liquid sonic velocity, as the criterion for critical flow in the liquid phase. The procedure is iterative but compensates for its complexity with high reliability and generality. The new relationship is validated by experimental data.
Fines Migration, Blocking, and Clay Swelling of Potential Geothermal Sandstone Reservoirs, Denmark
Authors: Priisholm S. , Nielsen B. L. , Haslund O.
Published: December 2007

Medium-grained, moderately well-sorted sandstones of fluvio-deltaic to shallow marine origin have been investigated for fines production and for variations in porosity/permeability. Porosity and permeability change within small horizontal and vertical changes in sampling points. Also, air permeability depends on flow direction, Klinkenberg correction, and cleaning procedure. Kinkenberg-corrected permeability and brine permeability were found not to be comparable.

Brine flow caused fines of kaolinite and quartz to be produced from the compacted sandstones, while uncompacted sandstones produced kaolinite, illite, and detrital minerals. Chlorites and mixed-layer clays were not produced as fines, although they were present in some samples. Reservoir damage occurred when formation brine was replaced by KCl-brine, at increase in flow velocity, and at pauses in flow. Changes in flow direction caused severe fines production, renewed bridging, and blocking by fines. Severe damage occurred when the samples were flushed with deionized water. Compared to field experiments, the laboratory experiments give the worst case of damage. An inverse relation was noted between porosity and the amount of fines produced.
Microbit Studies of the Effect of Fluid Properties and Hydraulics on Drilling Rate
Authors: Eckel John R.
Published: December 2007

It has long been known that mud properties affect drilling rate and that drilling with water is as much as six to seven times faster than with mud. However, it is not known why drilling rates with mud are lower. Recent studies show what fluid properties govern microbit drilling rate and also provide a quantitative correlation of these fluid properties and hydraulics with microbit drilling rate. All the microbit tests reported in this paper were made with a low permeability (about 10 md) limestone. They were conducted at constant bit weight and rotary speed with varying fluid properties, flow rate Q and nozzle diameter d. The tests showed that

- drilling rate in a given system with constant circulating rate and nozzle velocity is a function of the kinematic viscosity [viscosity/density, (cp)/ p (density)] of the drilling fluid measured at near bit nozzle shear rates;

- the combined effect of fluid properties and hydraulics on microbit drilling rate is defined by a Reynolds number function (kQp/D );

- for the same kinematic viscosity, drilling rate is independent of solids content; and

- for the same kinematic viscosity, drilling rate is independent of fluid loss.

Introduction

The fact that mudding up reduces rate of penetration is well known, but the reduction varies from well to well. The rate with mud may be 80 percent of the water rate or it may be as low as 15 percent Since this reduction of up to seven-fold takes place under conditions of constant bit weight, rotary speed and mud circulating rate in a uniform formation, it can only be a result of the change in fluid properties. Previous work (both in field tests and in laboratory microbit tests) showed that drilling rate with mud is lower than with water (Figs. 1 and 2). Microbit tests also confirm, at least qualitatively, the field observation that drilling rate slows with increased pressure differential from borehole to formation (Fig. 3). The qualitative effect of drilling rate of bit weight, rotary speed and rate of mud circulation are also the same for the field and microbit rig. For these reasons, the industry generally accepts microbit results as being qualitatively meaningful in terms of field application.
An Analytical Study of Pseudotime for Pressure Drawdown in a Gas Reservoir
Authors: Finjord Jan
Published: December 2007

The pseudotime transformation in the diffusion equation for pseudopressure is studied analytically for drawdown in a gas reservoir. The equation is not effectively linearized for early drawdown in the infinite-acting period because correction terms in the transformed equation cannot generally be neglected compared with terms interpreted as giving rise to liquid-type behavior. The remaining possibility of approximately logarithmic solutions in pseudotime is considered with slope differing from the liquid-type value. Analytical estimates for the magnitude of correction terms and for deviation of approximate slope are given.
A Numerical Study of the Pseudotime Transformation for Drawdown in the Infinite-Acting Period
Authors: Yue-lu You , Finjord Jan
Published: December 2007

Drawdown with a constant-surface-conditions gas rate into a single well, starting at homogeneous pressure conditions in a cylindrical gas reservoir, is simulated numerically. For radii much larger than the wellbore radius, the pseudopressure solution in the infinite-acting period can be plotted uniquely as a function of a Boltzmann variable s=rD2/4tpD, where rD and tpD are dimensionless radius and pseudotime. The nonlinear correction terms in the pseudotime diffusion equation, far from being negligible for drawdown, can become dominant in the infinite-acting period. This confirms an analytical result obtained previously. The correction terms are shown by simulation to be functions of s only for radii much larger than the wellbore radius. Plotted vs. In s, the pseudopressure shows an approximately linear behavior with a slope slightly larger than the usual constant-diffusivity slope. This was predicted by an explicit analytical solution.