bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Carbon Dioxide and Methane as Additives at Steamflood Conditions
Authors: Freitag N. P. , Kristoff B. J.
Published: December 2007

Heavy-oil production from a steamdrive may be improved by adding gases to reduce the steam requirement, to swell the oil, and to reduce oil viscosity. To help compare carbon dioxide (CO2) and methane (CH4), two of the most reasonable choices of gaseous additives, we measured the viscosity and density of a Lloydminster- type heavy oil when saturated with each gas at a single pressure at 25°, 80°, and 150°C. Our measurements were repeated in the presence of a water phase to address the lingering questions about the effect of water on this equilibrium, especially at 150°C.

In addition to confirming trends identified by previous authors, the results showed that the benefit of dissolved CH4 diminishes much less rapidly with rising temperature than for CO2. By 150°C the differences in benefit are small, which indicates that CH4 could be a more economical choice than CO2 as a steam additive in many reservoirs. In addition, no effect of equilibrium water was detected.
Field Experiments on Hydraulic Fracturing
Authors: von Schonfeldt Hilmar , Fairhurst C.
Published: December 2007

Hydraulic fracturing experiments at two underground and one near-surface location in igneous and shale formations were described. The tests were designed to study the feasibility of hydraulic fracturing as a method of determining in-situ stresses. The tests were carried out in open holes of 2-3/8-in. diameter. Fracturing tests on two 5-ft diameter cores were also reported. The test results revealed an increase in the magnitude of the stress as the face of an opening was approached from inside a rock mass. Horizontal fractures also were observed in areas of reportedly high lateral stress, providing some evidence for the validity of the providing some evidence for the validity of the principle of least resistance. The results also principle of least resistance. The results also indicate that caution must be used in using the shut-in pressure as a measure of the least compressive stress.

Introduction

Hydraulic fracturing is best known as a well stimulation method. There are other important applications, however, for which the process shows great potential. One of these is in the area of in-situ stress determination as suggested by Scheidegger Kehle and Fairhurst. The mechanics of the fracturing process is the same in any application, and improvement of the method may therefore be expected through a mutual exchange of experience in each of these areas.

The theory of the hydraulic fracturing technique relates measurable quantities such as the breakdown pressure and the instantaneous shut-in pressure to pressure and the instantaneous shut-in pressure to the tectonic stresses and certain physical rock properties. properties. Assuming negligible pore pressure and fluid penetration, the break-down pressure (pC) at the penetration, the break-down pressure (pC) at the instant of fracture initiation is given by the following expressions....................(1)

when the fracture extends in a "radial" direction (in a plane parallel to the axis of the borehole). And...................(2)

when the fracture extends in a direction normal to the borehole axis.

Corresponding expressions that include the effect of pore pressure and fluid penetration are given in the literature Because our work was done in dry and impermeable formations, Eqs. 1 and 2 are considered adequate. These formulae are based on the assumption that the borehole is drilled parallel to 3 and that the rock behaves as a linearly elastic isotropic material; it also assumes that the fracture is initiated in a direction perpendicular to the least compressive stress, i.e., 2 or 3, respectively, in accordance with the principle of least resistance.

The terms "radial" and "normal" fractures are introduced in place of the commonly used terms "vertical" and "horizontal" fractures in order to avoid possible confusion in the event a borehole is drilled in a direction other than the vertical.
Design, Execution, and Evaluation of Acid Treatments of Naturally Fractured Carbonate, Oil Reservoirs of the North Sea
Authors: Lietard Olivier , Bellarby Jonathan , Holcomb David
Published: December 2007

This paper discusses damage removal in naturally fractured carbonate, oil reservoirs of the central North Sea, located in the vicinity of salt domes. The reservoir rock is the well-known Tor chalk, the mechanical properties of which have been greatly modified by the proximity of diapirs. The matrix rock is much harder (similar to a limestone) and extensively fissured. Wells drilled through these reservoirs suffer from very severe damage as a result of the invasion of the natural fractures by large amounts of drilling mud. Productivity is restored by high-rate damage-removal treatments alternating stages of crosslinked gel, customized acid formulations, and ball sealers. Pre- and postjob well performances demonstrate huge productivity-index increases as a result of the cleanup of the natural fissures. This paper emphasizes mud-loss survey during drilling and perforation strategies; candidate selection, i.e., pre- and postjob productivity based on both rock (matrix and fissures) and damage properties; treatment execution (as per actual North Sea jobs); and treatment evaluation and diversion efficiency.
Effect of Steepness of Regular and Irregular Waves on an Oil Containment Boom
Authors: Walker G.E.
Published: December 2007

As part of the study described here, a mathematical model was used in an effort to predict splashover. Although the general motion of the boom can be simulated, we have a long way to go before a model will be sophisticated enough to take into account the interaction between the wave and the boom and to predict mathematically what it takes to swamp it.

Introduction

Shell Oil Co.'s concern with environmental pollution and more specifically the prevention of pollution of our lakes, rivers, and oceans resulted in an investigation to evaluate the effectiveness of commercial oil containment and removal devices. One phase of this extensive investigation, conducted by the Shell Pipe Line Research and Development Laboratory in Houston, was the evaluation of oil containment booms in the presence of waves. The evaluation consisted of presence of waves. The evaluation consisted of experimentally testing the commercially available booms in a wave tank; offshore testing in the Gulf of Mexico; scale model testing, at the Davidson Laboratory, Stevens Institute of Technology, Hoboken, N. J.; and attempting to mathematically model the boom response in waves.

Laboratory Wave-Tank Tests

The initial test phase consisted of evaluating, the performance of commercially available prototype and performance of commercially available prototype and production oil containment booms in long-crested production oil containment booms in long-crested regular waves generated in a laboratory wave tank. The wave tank built specifically for this purpose was 50 ft wide× 120 ft long and 5 ft deep, with a flapper wave generator at one end and a beach (wave absorber) at the other. This facility made it possible to generate regular waves with heights up possible to generate regular waves with heights up to 20 in. and periods ranging from 0.98 to 2.1 seconds. The following data were recorded during the wave-tank testing: wave height, wave length, wave period, the conditions at failure, and the mode of boom failure. The term "failure," of course, is subject to interpretation. Here failure relates to the operational characteristics rather than to the structural characteristics or strength of the boom and is defined as the passage of any oil either over or under the boom. The initial mode of failure for all of the booms tested was the splashing of oil over the top of the boom, with the exception of those booms that were marginally stable and that capsized without righting themselves after the first wave. For wave conditions more severe than those causing the initial splashover, the booms were swamped by the waves as was expected. An examination of these test data showed that the relationship between the wave length and the wave period of the long-crested regular waves agreed well with the mathematical relationship obtained using Airy wave theory for both intermediate- and deep-water conditions."Deep water" is defined by

,.........................(1)

where

d = water depth, Ld = wave length for deep water.

JPT

P. 1007
Some Strategies to Apply the Stehfest Algorithm for a Tabulated Set of Numbers
Authors: Ozkan Erdal , Raghavan Rajagopal S.
Published: December 2007

A method to use a tabulated set of numbers to analyze pressure tests by the Laplace transformation is outlined. This method is consistent with the Stehfest algorithm, which is commonly used in the literature. Because the method is self-consistent with the Stehfest algorithm, issues concerning polynomial fits to approximate tabular information, methods to approximate the tail of the Laplace transformation, etc., are avoided.
Quantification of Reservoir Connectivity for Reservoir Description Applications
Authors: Hird K. B. , Dubrule Olivier
Published: December 2007

This study investigates means for efficiently estimating reservoir performance characteristics of heterogeneous reservoir descriptions with reservoir connectivity parameters. We use simulated primary and waterflood performance for two-dimensional (2D) vertical, two- and three-phase, black oil reservoir systems to identify and quantify spatial characteristics that control well performance. The reservoir connectivity parameters were found to correlate strongly with secondary recovery efficiency and drainable hydrocarbon pore volume. We developed methods for estimating primary recovery and water breakthrough time for a waterflood. We can achieve this estimation with three to five orders of magnitude less computational time than required for comparable flow simulations.
Experimental Determination of the Biot Elastic Constant: Applications in Formation Evaluation (Sonic Porosity, Rock Strength, Earth Stresses, and Sanding Predictions)
Authors: Klimentos Theodore , Harouaka Abdallah , Mtawaa Bechir , Saner Salih
Published: December 2007

We developed an experimental method to obtain the Biot elastic constant of rocks from laboratory dynamic and static measurements. The Biot constant often has been calculated with various empirical equations. The experimental determination of the Biot elastic constant is very important to engineering problems associated with sand control, hydraulic fracturing, wellbore stability, earth stresses, sonic porosity, and estimation of compressional-, P, and shear-, S, wave velocity. Both the dynamic and static moduli of actual reservoir sandstone core samples, jacketed and mounted in a triaxial cell under vacuum, were measured at various confining and overburden stresses. The results obtained show that the Biot constant is a complex function of porosity, permeability, pore-size distribution, and overburden and confining stress, which means that it is not really a constant. Also, the static Biot constant is greater than the dynamic one and their difference increases with increasing overburden stress according to the equation αstatic = [1 + 0.05*(σz)ef]*αdynamic (where σz is in Ksi). Moreover, both the experimental static and dynamic Biot constants may be significantly different from values calculated with empirical equations. This study suggests that quantifying the Biot constant in the laboratory may enhance the determination of rock-strength/fracturing, earth stresses, rock subsidence, sanding predictions, P- and S-wave velocities, porosity, and pore fluid from sonic and seismic data.
An Experimental Analysis of the Transport of Drilled Particles
Authors: Zeidler Udo H.
Published: December 2007

An experimental apparatus was developed to determine the settling velocity of drilled particles in a Newtonian fluid and also to study the transport of drilled particles in an annulus using both water and drilling mud.

Correlations were developed for the settling velocity of the drilled particles and for the recovery fraction of the drilled particles subjected to turbulent flow of water in an annulus. The introduction of pipe rotation and drilling muds produces changes pipe rotation and drilling muds produces changes in the recovery fractions compared to the recovery fractions observed in the case of water where no pipe rotation is performed. No correlations were pipe rotation is performed. No correlations were developed, and the data is treated only qualitatively in these cases.

Introduction

The ability of a drilling mud to remove drilled particles (cuttings) from a wellbore annulus has particles (cuttings) from a wellbore annulus has been discussed by various authors, Williams and Bruce, Pigott and Hall, Thompson and Nuss.

The extension of this work to predict the net upward velocities of irregular shaped particles from various settling velocity equations has yielded inconclusive results with large differences between expected and observed values. Some explanation for these differences has been given, but further attempts to predict rise times under actual or simulated conditions have not been made.

By simulating a wellbore annulus in the laboratory, I have attempted to extend the present knowledge and present empirical relationships, when possible w predict the recovery fractions for drilled particles in a wellbore simulated annulus.
Hydrodynamics of Two-Phase Flow in Gas-Liquid Cylindrical Cyclone Separators
Authors: Arpandi Inta A. , Joshi Ashutosh R. , Shoham Ovadia , Shirazi Siamack A. , Kouba Gene E.
Published: December 2007

This paper presents new experimental data and an improved mechanistic model for the Gas-Liquid Cylindrical Cyclone (GLCC) separator. The data were acquired utilizing a 3" ID laboratory-scale GLCC, and are presented along with a limited number of field data. The data include measurements of several parameters of the flow behavior and the operational envelope of the GLCC. The operational envelope defines the conditions for which there will be no liquid carry-over or gas carry-under. The developed model enables the prediction of the hydrodynamic flow behavior in the GLCC, including the operational envelope, equilibrium liquid level, vortex shape, velocity and holdup distributions and pressure drop across the GLCC. The predictions of the model are compared with the experimental data. These provide the state-of-the-art for the design of GLCC's for the industry.
Measurement and Correlation of Gas Condensate Relative Permeability by the Steady-State Method
Authors: Henderson G. D. , Danesh Ali , Tehrani D. H. , Al-Shaidi Salman , Peden J. M.
Published: December 2007

High-pressure core flood experiments using gas condensate fluids in long sandstone cores have been conducted. Steady-state relative permeability points were measured over a wide range of condensate-to-gas ratios (CGR; volume of condensate per unit volume of gas, both at test pressure and temperature), and the velocity and interfacial tension (IFT) were varied between tests to observe the effect on relative permeability. The experimental procedures ensured that the fluid distribution in the cores was representative of gas condensate reservoirs. Hysteresis between drainage and imbibition during the steady-state measurements also was investigated, as was the repeatability of the data.

A relative permeability rate effect for both gas and condensate phases was observed, with the relative permeability of both phases increasing with an increase in flow rate. The relative-permeability-rate effect was still evident as the IFT increased by an order of magnitude. The influence of end effects was shown to be negligible under the IFT conditions used in the tests, with the Reynolds number indicating that flow was well within the so-called laminar regime under all test conditions. The observed rate effect was contrary to that of conventional non-Darcy flow, where the effective permeability should decrease with increasing flow rate. A generalized correlation between relative permeability, velocity, and IFT has been proposed.

The results highlight the need for appropriate experimental methods and relative permeability relations where the distribution of the phases are representative of those in gas condensate reservoirs.
The Effects of Heterogeneity and Wettability on Oil Recovery from Laminated Sedimentary Structures
Authors: Huang Y. , Ringrose P. S. , Sorbie K. S. , Larter S. R.
Published: December 2007

The sedimentary structure and wettability of clastic rocks at the laminaset scale may have an important influence on oil recovery by waterflooding. Previous work from this laboratory reported results for oil displacements in water-wet laminated systems. In this paper, results from a full cycle of drainage-imbibition floods in a cross-laminated rock slab are reported where the wettability of the slab was changed by ageing the system with a "synthetic crude oil". The distribution of fluid saturation was monitored using CT scanning techniques. The main purpose of this work is to investigate the effects of both the laminaset heterogeneity and wettability alteration on the displacement efficiency and oil trapping mechanisms for such systems. Results from from these floods are compared with previous findings for water-wet laminated system.

In these altered wettability experiments, the recovery efficiency significantly increased, due to the slab becoming more oil-wet. In contrast to the strongly water-wet case, an analysis of the remaining oil saturation shows that (a) no significant oil trapping occurred behind low permeability laminae in this flood, and (b) there was a higher remaining oil in the low permeability regions. Numerical simulations were performed to help our understanding and interpretation of the wettability changes. An excellent match of experiment with numerical simulation was obtained for a particular model case with the lower permeability laminae being more oil-wet than the higher permeability ones in general. We have termed this a heterogeneously-wet (or het-wet) system. To our knowledge, this is the first time that such behaviour has been demonstrated and analysed in detail.
Analysis of Rising-Bubble Experiments To Determine Minimum Miscibility Pressures
Authors: Zhou Dengen , Orr Franklin M.
Published: December 2007

We report an analysis of rising-bubble (RB) experiments for ternary systems. We present experimental evidence that observations of changes in bubble appearance are primarily controlled by changes in interfacial tension (IFT) that occur as components transfer from the surrounding liquid to the RB. We report experimental observations for an analog ternary system (brine/isopropanol/iso-octane) that confirm the influence of IFT on bubble appearance.

We describe also a simple diffusion model of composition changes during bubble rise. A combination of experimental results and model calculations indicates that RB experiments can be used to detect the minimum miscibility pressure (or enrichment) for ternary vaporizing drives. Similar analysis shows, however, that falling drop experiments are more appropriate for ternary condensing displacements. Questions that remain to be resolved for systems with more than three components also are outlined.
Oil Production After Breakthrough as Influenced by Mobility Ratio
Authors: Dyes A.B. , Caudle B.H. , Erickson R.A.
Published: December 2007

The study of the influence of fluid mobilities on the sweepout pattern resulting from the injection of gas or water has been extended to cover the production period which follows breakthrough of the injected material. Mobility ratios over the range common in field operations (0.1 to 17) were studied for several pattern floods (five-spot, staggered, and direct line drive). The experimental data required for these studies were obtained by the use of the x-ray shadow graph technique using miscible oil phases of different viscosities in porous plate models of a reservoir element. From the shadowgraph pictures obtained before and after breakthrough of the injected fluid, flowing ratios at the producing well and cumulative volumes injected were calculated.

The method for applying such data in predicting field behavior is illustrated for a water flood of a five-spot. For this case a range of mobility ratios of 0.5 to 5.0 results in:nearly complete (95 to 100 per cent) sweepout pattern efficiencies at abandonment conditions,production after breakthrough being responsible for as much as one-third of the total recovery at the lower mobility ratios, anda twofold variation in the operating life of the reservoir.
A Novel Liquid Permeameter for Measuring Very Low Permeability
Authors: Sanyal S.K. , Pirnie R.M. , Chen G.O. , Marsden S.S.
Published: December 2007

A liquid permeameter for very tight rocks is described. High upstream pressures are achieved by a "pump" based on the thermal expansion of liquid. Confining pressures to 10,000 psi may be maintained with a modified Hassler sleeve. Pressure is measured with a low displacement, diaphragm-type transducer. Permeability is measured indirectly through pressure decline over a time period.

Introduction

Permeability is an important property in petroleum engineering, as well as in several branches of science. Ground water hydrology studies and some geological problems are concerned with permeability. Permeability measurement often is very difficult. In Permeability measurement often is very difficult. In this paper we describe an instrument designed and developed to measure liquid permeabilities of very tight Precambrian rocks. These are currently of importance in the study of the origin of life. Permeabilities in the submillidarcy range are also Permeabilities in the submillidarcy range are also of importance to the petroleum industry in the study both of cap rocks of oil and gas reservoirs and fluid flow and migration through source rocks.

Design Considerations

From knowledge of these samples, we felt no other known permeameter would give reliable values. A liquid permeameter was necessary because gas might dehydrate the chert or other minerals, causing a shrinkage and an unnaturally high permeability. Thomas et al. reported air and water permeabilities of very tight rocks, with the air permeability value always being much higher than the water. Also, the expected low permeability would lead to low flow rates even at high pressure differentials. Ordinary pumps would seem to be unsuitable. Casual examination of the samples revealed fractures and without sign of a pore structure; hence, permeabilities would be strongly sensitive to external or overburden pressures. A method of varying this latter factor seemed desirable. Finally, since other physical measurements might be made on the sample, nonpermanent methods of sample mounting were desirable.

We decided on a novel approach to determine permeability. This involved a pump based on the permeability. This involved a pump based on the thermal expansion of liquid and the use of pressure decline to calculate permeability.
Vapor-Liquid Equilibrium Ratios (K-Values) of Light Hydrocarbons at Reservoir Conditions
Authors: Woertz Byron B.
Published: December 2007

A set of five methane K-charts has been developed for reservoir-type systems, for pressures above 1,000 psia and temperatures of 0 to 300 degrees F. Convergence psia and temperatures of 0 to 300 degrees F. Convergence pressures used in development of the charts ranged pressures used in development of the charts ranged from 3,800 to 15,200 psia. The highest experimental pressure used was 12,000 psia. pressure used was 12,000 psia. Seven references from the literature were used as data sources for the charts. Three other sources (one consisted of unpublished data) were used in checking K-values predicted from use of the charts. The charts predicted the data points used in their development to predicted the data points used in their development to an average deviation of 3.77 percent. However, the deviation of the charts from the three independent data sources was 11.88 percent for 13 points from one reference, 6.47 percent for two points from another and 4.16 percent from 10 points from the third reference. The form of the methane K-charts was selected to avoid crossover and to promote ease of reading at high pressures. However, some interpolation and use of Kp products is involved in obtaining the desired K-values. Use of the charts should be restricted initially to systems that are somewhat similar to those from which the charts were developed. Experience will indicate how much the range of usage can be extended. Data from six of the references have been used to develop a set of K-charts for ethane through mixed hexanes at pressures above 1,000 psia and at temperatures of 33 to 250 degrees F. No correlation with convergence pressure was observable. Therefore, the charts were plotted as log K vs log pressure with lines of constant temperature. pressure with lines of constant temperature. The original data were fitted to an average deviation of 8.46 percent with respect to K-values for ethane and heavier. In a comparison of these charts with unpublished Atlantic data, data of Kilgren and data of Evans and Harris, the average deviations between related values were found to be 18.05 percent, 7.23 percent and 18.44 percent, respectively. These were about as good as the Natural Gas Processors Assn. (NGPA) chart deviations for similar systems. The present charts for ethane through mixed hexanes may be useful in the high-pressure region where the NGPA charts are difficult to read. No restrictions have been placed on the present charts other than that they placed on the present charts other than that they should not be used on systems greatly different from those of the six original references.
Measurement and Correlation of Gas Condensate Relative Permeability by the Steady-State Method
Authors: Henderson G. D. , Danesh A. , Tehrani D. H. , Al-Shaidi S. , Peden J. M.
Published: December 2007

High pressure core flood experiments using gas condensate fluids in long sandstone cores have been conducted. Steady-state relative permeability points were measured over a wide range of condensate to gas ratio's (CGR), with the velocity and interfacial tension (IFT) being varied between tests in order to observe the effect on relative permeability. The experimental procedures ensured that the fluid distribution in the cores was representative of gas condensate reservoirs. Hysteresis between drainage and imbibition during the steady-state measurements was also investigated, as was the repeatability of the data.

A relative permeability rate effect for both gas and condensate phases was observed, with the relative permeability of both phases increasing with an increase in flow rate. The relative permeability rate effect was still evident as the IFT increased by an order of magnitude, with the relative permeability of the gas phase reducing more than the condensate phase. The influence of end effects was shown to be negligible at the IFT conditions used in the tests, with the Reynolds number indicating that flow was well within the so called laminar regime at all test conditions. The observed rate effect was contrary to that of the conventional non-Darcy flow where the effective permeability should decrease with increasing flow rate. A generalised correlation between relative permeability, velocity and IFT has been proposed, which should be more appropriate for condensing fluids than the conventional correlation.

The results highlight the need for appropriate experimental methods and relative permeability relations where the distribution of the phases are representative of those in gas condensate reservoirs. This study will be particularly applicable to the vicinity of producing wells, where the rate effect on gas relative permeability can significantly affect well productivity. The findings provide previously unreported data on relative permeability and recovery of gas condensate fluids at realistic conditions.
Twelve Years of Gas Injection in a Frio Sand
Authors: Millikin B.T.
Published: December 2007

Introduction

The purpose of this paper is to contribute to the existing knowledge of the economic recovery of oil by methods other than normal depletion. A case history is presented of a gas injection project in one zone of the multiple producing zone Frio sands of south Texas. Approximately 75 per cent of the produced gas has been returned to the formation for 12 of the 13 years of producing life. The study is an example of the performance which has been experienced by return of a large portion of the produced gas to the gas cap of a thin non-homogeneous sand.

Geology

The producing zone is the Frio sand of lower Oligocene age. The oil and gas accumulation is a combination of a structural and stratigraphic trap. The structure consists of a large asymmetrical nose plunging gently to the northeast. The reservoir is limited on the west flank by an oil-water contact, on the north and south by the sand lens grading into shale, and on the east by a steep fold or fault parallel to the axis of the structure. The dip of the west flank or oil producing flank is approximately 130 ft per mile, or only 1.5 degrees.

There are 11 separate Frio producing zones in the field but this paper is limited to only one of the zones. The sand lenses are separated vertically by 25 to 75 ft of shale and were correlated across the field by means of markers picked from the electric logs. A portion of a typical cross section is shown on Fig. 1 and the section is located with reference to the area on Fig. 2. The D-5 reservoir is the large sand lens which appears in the D zone on the cross sections. It covers an area of approximately 2,100 acres. The structural map of the D zone (Fig. 2) was contoured on the subsea correlation points on the top of the D zone.

The reservoir rock is predominately firm, medium to fine-grained gray, argillaceous sandstone but lenses of soft, loosely consolidated sandstone occur throughout the producing zone. An x-ray diffraction indicates the clay content to be chiefly of the montmorillonite group and solubility tests indicate a low carbonate content. The porosity ranges from 8 to 28 per cent with a weighted average of 23 per cent. The majority of the horizontal permeability ranges from 100 to 500 md and averages 194 md. The vertical permeability is approximately one-half of the horizontal permeability.
An Evaluation of Scale Inhibitors
Authors: Vetter O.J.
Published: December 2007

A rating of inhibitors in the order of their effectiveness is a relative matter and depends upon test conditions. The most important conditions are the degree of supersaturation and the temperature; the higher the supersaturation and the higher the temperature the less effective a scale inhibitor becomes.

Scale Inhibition Is Still an Art

Scale inhibition is still closer to being an art than a science. The literature deals only to a very small extent with the problems of scale inhibition. Most of the published data do not consider the basic facts of crystallization and inhibition. such as reaction mechanisms and kinetics. Because these fundamental considerations are often neglected, there are many recorded failures of scale treating procedures in oil and gas fields.

This neglect of fundamentals and lack of data is surprising because the formation of scale is a rather costly problem for some industries, above all the petroleum industry. We lose many millions of dollars petroleum industry. We lose many millions of dollars in revenue every year because scale creates flow restrictions in our fields.

Accurate evaluation of scale inhibitors is the first and most important step toward effective scale control.

How Are Scale Inhibitors Presently Tested? Presently Tested?

Test Machines

Several investigators have been concerned with the development of test machines designed to simulate the conditions of scale deposition in the field. The degree of scale buildup in these test devices is used to screen and rank commercial products and experimental chemicals.

Scale Coupons

The use of scale coupons in the field is a test somewhat related to the use of test machines in the laboratory. Steel coupons are inserted in flow lines, and the amount of scale they accumulate is used to evaluate an inhibitor that has been injected into the system upstream of the coupon.

Precipitation Test Precipitation Test In the "chelation test," which should be called the precipitation test, two chemically incompatible precipitation test, two chemically incompatible solutions are combined. The precipitation of scale-forming solids - for example, calcium carbonate (CaCO ), calcium sulfate (CaSO,) or barium sulfate (BaSO ) is measured in the presence of an inhibitor of varying concentrations by means of chemical analyses. The amounts of precipitate obtained are then compared with the amount of precipitate formed by mixing solutions containing no scale inhibitor. The more solids that are kept in solution by a given amount of inhibitor. or the less inhibitor that is needed to keep a given amount of solids in solution, the more effective and desirable the inhibitor is thought to be.

This test is widely used for laboratory evaluation of scale inhibitors. The test is very quick and convenient to run, gives fast results, does not require costly equipment, and can be run by relatively untrained personnel. Unfortunately, the reproducibility of the result is sometimes very poor, and data reported by different testers is often contradictory.

P. 997
On Fractures Produced by Low-Velocity Impact In Plexiglas Rods Simulating Drill Bits
Authors: Rinehart John S. , Prompsy Jean-Jacques
Published: December 2007

Introduction

The purpose of the present study was to arrive at a better understanding of the stress fields developed within drill bits under dynamic loading and the influence that these stress fields could have on the failure of the drill bits. Particular emphasis has been given to the influence that bit shape has on the establishment of highly localized, potentially destructive stress inhomogeneities within the bit. This paper covers one phase of a broad study involving three velocity regimes: impacts at very low velocities, 0 to 20 ft/sec, a velocity range in which dynamic effects are just beginning to be found; impacts at velocities ranging from 20 to several hundred ft/sec, a range commonly encountered in practical drilling operations; and impulsive loading through the detonation of explosives, a velocity range in which the dynamic effects are greatly exaggerated and made more identifiable. Specifically, fracturing which develops at the end of a cylindrical bar undergoing a shock produced by impact was experimentally investigated, the impacted area being the face of a truncated cone terminating the cylindrical bar. Fracture characteristics were looked at as a function of impact velocity, area of impacted face and cone angleparameters of considerable importance in the design of drill bit.

EXPERIMENTS

The specimens were made of Plexiglas, which enabled the fracture pattern to be easily observed. In Plexiglas, the velocity of a longitudinal wave is about 8,700 ft/sec, and the velocity of the transverse wave about 4,200 ft/sec. The specimens were impacted by a steel cylinder whose lower face was parallel to the terminal face of the experimental bit, as shown in Fig. 1. The impacting mass was shifted up and down on two steel rods, dropping from a maximum height of 11 ft, with the velocity varied between 0 and 6.5 m/sec. The initial mass of the cylinder was 4.1 kg, which could be increased by steps up to 8.8 kg by addition of steel plates. The velocity of the steel cylinder was determined by using an electric circuit; as the cylinder dropped, it contacted two steel wires, the first one starting and the second one stopping an electronic counter. Two similar counters connected in parallel were used to corroborate each other. The velocity was checked at each drop as it had been observed to vary somewhat from drop to drop. The two contact wires were located just above the top of the specimen so as to give a value of the instantaneous velocity of the steel cylinder at impact. The distance between the wires was 40 0.5 mm and the discrepancy between the counters was never more than 0.1 m/sec. Thus the velocity was known to within 3.25 per cent. This precision was sufficient with respect to the precision of the machining of the specimens. A very small lack of parallelism between the face of a specimen and that of the impacting hammer resulted in an oblique impact which required a much lower velocity to break the specimen.

SPEJ

P. 203^
Inflow Performance Relationships for Damaged Wells Producing by Solution-Gas Drive
Authors: Standing M.B.
Published: December 2007

The dimensionless inflow performance relationship (IPR) for solution-gas drive wells presented by Vogel* is very useful in well producibility calculations. Well rates at various pressure drawdowns can be predicted easily by use of either his chart or his equation (his Fig. 5 and Eq. 1). A second use of his relationship, to be illustrated later, is as a means of averaging results of several rate tests on a given well.

Vogel investigated effects of wellbore damage on the shape of IPR curves. He states that the effect of skin, or damage, is to cause a straightening of the IPR curve. The reference curve he presents, however, (his Fig. 5) essentially applies to wells without damage during their early life. My purpose here is to present a companion chart that can be used for calculations involving damaged wells. The chart is useful in predicting stimulation that might be accomplished, under predicting stimulation that might be accomplished, under given drawdowns, if the wellbore damage is changed from one value to some other value.

Consider the pressure-distance profile of the positively damaged well illustrated in Fig. 1. The flow positively damaged well illustrated in Fig. 1. The flow efficiency, FE, of the well-formation system is given by the relationship(1)

Graphically, this amounts to the distance (p - p' wf) divided by the distance (p - p wf). For a well draining a closed cylindrical volume, flow efficiency can also be expressed as

(2)

where s is the dimensionless skin factor. FE also expresses the ratio of the well's flow rate with damage to the flow rate without damage.

P. 1399
Estimated Effect of Vertical Fractures on Secondary Recovery
Authors: Crawford Paul B. , Collins R.E.
Published: December 2007

Potentiometric model studies have been made of vertically fractured reservoirs. All fractures originated at the well and extended into the reservoir for various distances. Studies were made to determine the areal sweep efficiencies for line-drive patterns. The areal sweep efficiency for the unfractured system studied was 70.6 per cent. It was found that if the vertical fracture was parallel with the direction of flood, the areal sweep efficiency may be considerably reduced, approaching zero in some instances. If the fracture was at right angles to the direction of flood, the areal sweep efficiency may be greater than that for the unfractured system. The sweep efficiency depends on the length and orientation of the fracture and direction of the flood. It is concluded that considerable effort should be made to determine the nature and direction of fractures before initiating a flooding program. Such information is required if the maximum sweep efficiency is to be obtained and channeling is to be reduced to a minimum.

Introduction

The recent development and application of fracturing techniques to petroleum reservoirs has served to focus considerable attention on the effect such fractures may have on secondary oil recoveries. The opinion has been expressed that fracturing may not alter appreciably the water flooding possibilities. Others have thought that channeling may occur and that the creation of fractures may serve to substantially reduce the possibilities of conducting a successful water flood in the reservoir.

The purpose of this study was to obtain quantitative estimates of the effect of vertical fractures on the areal sweep efficiencies of line-drive flooding patterns. In presenting this work on vertical fractures, it is not to be inferred that the present fracturing techniques result in producing a vertical fracture. The types of fracture which are created are not known with certainty in every case. Some are believed to be horizontal, others inclined along bedding planes, and some data indicate vertical fracturing. Each fracture will probably exert a different influence on the sweep efficiency of the secondary recovery program; consequently each fractured well should perhaps be considered as a separate problem, requiring a careful analysis.
Planning the Energy Years
Authors: Nedom H.A.
Published: December 2007

Future worldwide petroleum opportunities are equal to or better than any known in the past. However, the rules of the game are changing, and the opportunities will be seized by those who can adjust rapidly.

In a world of mushrooming energy needs, this country and its petroleum industry are in crucial times. The international balance of supply and demand and our country's energy shortage call for critical decisions on a national level that will in turn guide the future actions of companies and individuals. This paper examines the guideposts of long-range planning 20 years ahead, and in doing so, injects large elements of judgment and conclusion. The complex future is viewed from a worldwide perspective and from that of the U. S., the petroleum industry, and an average oil company.

Worldwide

Energy consumption is rapidly growing. The present rate will double by 1985, but fortunately the petroleum needed through that period and for years beyond petroleum needed through that period and for years beyond is either on hand or reasonably certain of discovery. Studies of geologically favorable areas around the world and their high potential confirm this conclusion. Those areas of greatest promise are Africa and the Far East, both unexplored relative to their onshore and offshore potential. Discoveries in Nigeria and Indonesia provide samplings of the larger areas that await exploration. Next in future importance is the Middle East, which already holds two-thirds of the known world oil reserve, and where the hydrocarbon potential remains high. Large concessions have yet to potential remains high. Large concessions have yet to be explored by new and improved seismic methods.

North and South America will also contribute significantly. In summary, the world petroleum future is one of large and rising consumption with adequate supply.

The world's large petroleum reserve areas are widely separated from the points of maximum consumption and this dislocation will increase as newer reserves are found in more and more remote places. The North Sea discoveries are welcome exceptions to this worldwide trend. In the future, countries that are large consumers and that are net importers will become even more dependent upon those with excess supply, and will increasingly rely upon large-volume, low-cost, long-distance transportation to bring the petroleum to market. Countries with excess supply, petroleum to market. Countries with excess supply, which even now have a political weapon against energy-short nations such as the U. S. and most countries of Europe, will find that their bargaining positions will improve. However, their influence will positions will improve. However, their influence will be limited by the over-all ample supply, since each country with petroleum to sell will be competing in a worldwide buyer's market. Of great interest on the international scene will be the strategies used by energy-short nations to insure that their future supplies are in friendly hands and available when needed.

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Optimization of a Cyclic Steam Injection Process Using Penalty Functions
Authors: Gottfried Byron S.
Published: December 2007

A penalty-function technique is described that can be used to solve constrained nonlinear optimization problems. The method is based upon the strategy of transforming the original constrained optimization problem into an equivalent unconstrained problem, and then solving a sequence of unconstrained optimization problems. This strategy is particularly attractive because unconstrained optimization problems are generally much easier to solve than constrained problems.

The method is applied to a cyclic steam injection process that has been studied previously using process that has been studied previously using other techniques. Detailed solutions are presented and the characteristics of the method are discussed The method works, and it exhibits several favorable characteristics, such as applicability to a wide variety of nonlinear problems and freedom from convergence difficulties or computer storage limitations. Moreover, the method can be understood and implemented on a digital computer with ease.

Introduction

It is difficult for the analyst to recognize the methods that are best suited to a particular problem. Recent texts on optimization theory have not aided the situation because little is presented about which techniques are most applicable to different problems. Thus, the difficulties of identifying particular optimization techniques for various specialized applications remain largely unresolved.

This paper presents a penalty-function optimization algorithm is suited to a variety of nonlinear engineering optimization problems. The method is applied to a problem that has been previously optimization of a cyclic steam injection previously optimization of a cyclic steam injection process. This example has a serial structure and may, process. This example has a serial structure and may, therefore, appear to be an unlikely application for a penalty-function optimizer. There are, however, several significant advantages to the use of a penalty-function algorithm rather than dynamic penalty-function algorithm rather than dynamic programming or the maximum principle. programming or the maximum principle.
Scaled Fluid-Flow Models with Geometry Differing from that of Prototype
Authors: van Daalen F. , van Domselaar H.R.
Published: December 2007

Experiments on oil displacement from homogeneous porous media have shown that the component porous media have shown that the component oil flow across the layer is often negligibly small compared with that parallel to it. This result is applied in the inspectional analysis of the equations governing the macroscopic displacement processes. It is shown that in rectangular homogeneous models the dimensionless groups l/h and a can usually be neglected. This finding has been proved experimentally in rectangular models of various dimensions, two extremes of which are described in this paper.

The work has been extended to curved models. An additional requirement is that the angles of dip must be small. Comparative experiments have been carried out in three-dimensional models of various geometrical configurations. The results of both studies indicate a greater flexibility in the use of models than has previously been assumed.

Introduction

The production behavior of petroleum reservoirs can to a large extent be investigated with the help of scaled models, although the great number of parameters to be scaled in such processes precludes parameters to be scaled in such processes precludes complete simulation. However, not all parameters have an equally important influence on the process; and it is therefore necessary to select the most important ones and investigate which parameters can possibly be neglected.

To date, oil reservoirs have almost always been represented by models of similar geometry. In other words, the characteristic length, width and height are scaled down by the same factor. For many reservoirs, however, the length-height ratio is extremely large, and laboratory models become inconveniently long or very thin. In such cases it would be desirable to make the model too thick relatively. It will be demonstrated that this is in a number of cases a justifiable solution.