bluuebunny/crossref_metadata_2025 huggingface dataset:
Principles of Engineering Design Applied to Writing on the Job
Authors: Hay-Roe Hugh
Published: December 2007

It's no secret that plenty of engineers dislike having to communicate in writing and feel that they don't do a very good job. They may blame deficient language skills, when in fact the biggest problem is something else entirely. The unrecognized No. 1 problem is this: the writing techniques we learned in college were never meant to satisfy the needs of readers in industry.1,2

A practical solution to this problem was developed by Melba Jerry Murray, an industrial editor. She worked with the engineers of a major oil company to create a systematic procedure for writing to management and professional colleagues.3 Murray noticed that most engineers communicated effectively in conversation but dropped the ball when they started to write because they went back to the approach they learned in college. She solved that problem by using the conversational transfer of information as a guide for designing memos, letters, and reports of any length. It works like this:Get to the point. Tell your readers what you want from them, or to offer them, in plain business language.Answer, in sequence, any questions that your readers would ask in response to your main point. (See the left side of Table 1 for an idea of how this works.) Now you have a reader-oriented summary of your message. To use it as is, skip ahead to Step 7. But for long reports, articles, or proposals, proceed with the next step.Use the summary (Step 2) to develop a reader-oriented topic outline. This will ensure that you get away from the old outline shown on the right side of Table 1.Develop a main-point outline. In the outline, every heading you wrote for your reader-oriented outline is followed by a sentence containing the main point for that section of the document.Assemble illustrations that will support and explain your text. Send a set of the illustrations, attached to a copy of your main-point outline, to everyone who will have to approve your document.Arrange a prewriting conference to get approval of the proposed content.Compose the complete text. (For several reasons, the worst way to do this is to write it out in longhand.)Edit and polish the completed draft.

This approach appeals to engineers because it is logical and systematic. Managers receive the full impact of your ideas without having to search around with a highlighting marking pen for essential points buried in the text. Any engineer-writer who has the habit of sandbagging readers with big words can relax and write simply. Plain language reduces the chance of making embarrassing errors.

References

Barabas, C.: "Technical Writing in a Corporate Culture: A Study of the Nature of Information," Writing Research Series, Ablex Publishers (1990) 18. Medawar, P.: The Threat and the Glory: Reflections on Science and Scientists," Oxford U. Press, Oxford, U.K. (1991) 233. Murray, M.J. and Hay-Roe, H.: Engineered Writing: A Manual for Scientific, Technical, and Business Writers, PennWell Books, Tulsa (1986) 292.

P. 493
Application of Stability Approach to Torsional and Lateral Bit Dynamics
Authors: Abbassian Fereidoun , Dunayevsky V. A.
Published: December 2007

This paper addresses the dynamic stability of polycrystalline diamond compact (PDC) bits under induced torsional and lateral vibrations. Dynamic stability is investigated by considering three simple mechanical systems representing string-torsional vibration, bit-lateral dynamics, and coupled torsional-lateral vibration of the bit-string assembly. For each system, the rotary-speed (rev/min)/ weight-on-bit (WOB) domain within which the system is dynamically stable is determined. The influence of various drillstring and bit parameters on the stability of bit motion is studied through their effect on the size of the stability zone on (rev/min)/WOB plots. These illustrate the power of the stability approach in providing valuable qualitative information on the main parameters influencing bit stability.
Early Evaluation of Uncertainties in the Incremental Condensate Recovery Through a Gas Cycling Process
Authors: Massonnat Gérard , Bachtanik Claire , Tutenuit Emmanuelle , Gouel Patrick , Carles Nicolas
Published: December 2007

The process of evaluating and assessing a reservoir early in its development is rather difficult and uncertain although the results of the evaluation may have far-reaching consequences for the reservoir. This paper proposes and describes a methodology for enhancing this assessment. The method involves several basic steps including: identification of key heterogeneities, their quantification, the development of models representing the full breadth of variations in heterogeneity, the detailed modeling of limited areas of the reservoir to assess the effects of the model and geologic uncertainties, and the use of these results for calibrating up-scaled full-field models. The methodology is applied for a gas condensate reservoir appraised by only two wells in which the choice of recovery process (primary depletion or gas-cycling) has not yet been made.

Given that the key heterogeneity is unknown at this early stage, stochastic modeling is then undertaken on a grid emphasizing vertical discretization.

In order to provide contrasted models clearly showing the uncertainty associated with the geological model, two "end-member hypotheses" are used, based on the uncertainty as to the frequency and range of the heterogeneities.

Simulations carried out on only part of the reservoir show how sensitive the results are to the range of the heterogeneities. This is illustrated particularly clearly in the gas-cycling option in which gas injection is much more effective in the case of low range heterogeneities than for long range heterogeneities.

After optimizing the clustering of fine grid cells into coarse grid cells, it is demonstrated that simulation results obtained on a fine grid model can be reproduced with a significantly smaller number of layers.
The Differentiation Method in Rheology: III. Couette Flow
Authors: Savins J.G. , Wallick G.C. , Foster W.R.
Published: December 2007

The theory of the differentiation method for the Couette flow experiment is reviewed. Particular attention is given to the requirements on data analyses in the case of the class of non-Newtonian materials described as viscoplastics, i. e., materials characterized by a yield point or yield stress. Here, changes in boundary conditions arise when the shearing stress attains a critical value with the result that the form of the basic integral equation for Couette flow is determined by the flow conditions existing during the measurement.

Introduction

In the preceding papers in this series, the salient features of the differentiation method of rheological analysis in Poiseuille-type flow were discussed. It was shown that a dual differentiation- integration method analysis of the Poiseuille flow of idealized generalized Newtonian and visco-plastic models could be used to develop a spectrum of highly sensitive response patterns in terms of certain characteristic derivative functions. These functions were shown to optimize the selection of the most appropriate functional relationship between f(p) and p from the Poiseuille flow experiment. The present paper reviews the theory of the differentiation method as applied to the equally important Couette flow experiment. We will also discuss the range of variables over which the basic integral equation for Couette flow is applicable when the non-Newtonian material is of the viscoplastic type, i.e., characterized by a yield point or yield stress.

THEORY

Having described the application of the differentiation method to Poiseuille-type flow in the preceding papers, we now proceed to the case where the test liquid is confined to the annular space between coaxial cylinders of length L, one of which is in motion, i.e., Couette flow, formulating the basic integral equation after the method of Mooney. The observed kinematical and dynamical quantities are the angular velocityand the torque T. Here, the one nonvanishing component of the shear-rate tensor is

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

and the corresponding component of the shearing-stress tensor at any point r is given by

..........................(2)

The shearing stresses at the inner surface of radius R(1) and the outer surface of radius R(2) are related by

.................(3)

Combining Eqs. 1, 2 and 3, letting = 0 at p = p1 and = at p = p2 and integrating yield

.........................(4)

Note that the definite integral has a finite lower limit. Differentiating Eq. 4 with respect to p1, following the rule of Leibnitz (i.e., in Eq. 11 of Ref. 1), gives a difference equation in the desired function

..................(5)

This result was initially obtained by Mooney who used it as a starting point for an approximate solution. Several other approximate solutions of the difference equation have been described, the principal results of which are described in the succeeding sections. The interested reader is referred to the original papers for the details.

SPEJ

P. 14^
The Effect of Temperature and Pressure on the Interfacial Tension of Water Against Methane-Normal Decane Mixtures
Authors: Jennings Harley Y. , Newman George H.
Published: December 2007

The interfacial tension of water against mixtures of methane and normal decane bas been measured in the interval 74 to 350 degrees F and 14.7 to 12,000 psia. These measurements show the range of interfacial-tension values obtained with water against an ideal "live-oil" system under reservoir conditions of temperature and pressure. The interfacial-tension data were obtained by the pendent drop method. The density data used for pendent drop method. The density data used for the pendent drop calculations were based on visual cell pressure volume measurements of the mutually saturated phases. Seven systems covering the methane-decane composition range from 100 percent decane to 100 percent methane were studied at three temperatures and 11 pressure intervals in the single-phase, hydrocarbon region.

A minimum in the interfacial-tension vs methane-decane composition curve was observed. The minimum occurred at about the same composition in each isotherm, namely, with a mixture containing nearly equal weights of methane and decane. Both temperature and pressure affected the interfacial tension. For some compositions at constant pressure the interfacial tension increased with increased temperature.

Introduction

Although crude oil usually occurs in the formation saturated to some degree with methane, interfacial-tension data for methane-oil mixtures against water have not been published. These data are fundamental to an understanding of the role of interfacial forces in oil recovery and provide a basis for interpreting the interfacial tensions against water obtained with "live" crude-oil systems.

We obtained interfacial tensions against water for an ideal "live-oil" composed of mixtures of methane and normal decane. Portions of this three-component (water, methane, normal decane) system have been studied and reported and these data serve as limits for our results. Hough et al. presented data for the methane-water system at presented data for the methane-water system at temperatures to 280 degrees F and pressures to 15,000 psia. Stegemeier studied the two-phase methane-decane system to 183 degrees F and 5,100 psia, and Jennings published results for the normal psia, and Jennings published results for the normal decane-water system to 350 degrees F and 12,000 psia.

In this study we have obtained data for water-oil interfacial tension as a function of temperature to 350 degrees F. and pressure to 12,000 psia, using a series of live oils of known composition. The interfacial-tension data were obtained by the pendent drop method.
A Generalized 3D Well Model for Reservoir Simulation
Authors: Ding Y.
Published: December 2007

Well modelling plays an important role in reservoir simulation. Commonly used well models are based on the 2D analytical pressure solution (radial flow) and on an "adequate" numerical productivity index calculation. These models applied to 3D simulations may give erroneous results, especially while modelling undulating wells (slanted wells), multi-lateral wells, finite-length horizontal wells or partially penetrating vertical wells. The main reasons are the lack of 3D pressure solution and the inaccurate flow calculation near the well.

In this paper, the layer potential is introduced for representing the 3D pressure distribution of the steady-state flow in the vicinity of wells. The flow approximation is improved by modifying the near well transmissibilities, taking into account this 3D pressure solution. This new well model is valid for any well configuration and allows to describe accurately 3D well behaviour.
Theory of Multicontact Miscible Displacement with Nitrogen
Authors: Dindoruk Birol , Orr Franklin M. , Johns Russell T.
Published: December 2007

Solutions obtained by the method of characteristics (MOC) for displacement of mixtures of methane, butane and decane by nitrogen or nitrogen/methane mixtures are used to explain conflicting experimental observations concerning the sensitivity of minimum miscibility pressures to changes in the compositions of an initial oil or the injection gas. The solutions presented show why some investigators have reported weak dependence of the minimum miscibility pressure (MMP) on methane concentrations while others have reported significant sensitivity. The analysis of displacement composition routes indicates that either observation can be correct for some ranges of initial and injection fluid compositions, and shows that the sensitivity behavior depends on the relative positions in composition space of three key tie lines (the initial, injection, and crossover tie lines) with respect to the critical locus.
Determining Flow Equations from Stochastic Properties of a Permeability Field: the MHD Model
Authors: Lenormand R.
Published: December 2007

Numerical reservoir simulations can be improved by using "homogenized" transport equations which account for real flow mechanisms: instability, fingering, channeling, etc. In this paper, the homogenized transport equations and relative permeabilities are derived by using a standard stochastic representation of the permeability field and an original stochastic calculation for the flow equations which uses the concept of streamtubes. An approximate equation, called "MHD", is proposed for displacements in reservoirs for various types of permeability fields. The equation contains a dispersive term (dispersion coefficient D) and a nonlinear convective term with the product H (heterogeneity factor) multiplied by viscosity ratio M. The main advantage of the method is that the D and H parameters that characterize the permeability field are determined from a one-phase numerical simulation, a simulation that is not time consuming.
A Novel Technology To Control Proppant Backproduction
Authors: Card R. J. , Howard P. R. , Féraud J-P.
Published: December 2007

Backproduction of proppant from hydraulically fractured wells continues to create operational problems for oil and gas producers. As much as 20% of the proppant placed in the fracture can be returned to the surface, necessitating costly and labor-intensive surface-handling procedures. The development of unmanned platform operations remains impossible in some areas because of proppant backproduction. Flexibility in well turnaround and production strategies also can be very limited. Curable resin-coated proppant (RCP) has provided the most cost-effective and widely used method to control proppant backproduction. While this is a valuable technique that has served the industry well for many years, it is not universally successful.

A new technology has been developed to control proppant back-production and to increase flexibility in well turnaround and production strategies. The technology has been used successfully on several hundred hydraulic fracturing treatments. In this technology, a mixture of fibers and proppant is pumped into the fracture to form a pack that is resistant to proppant backproduction under typical oil/gas production conditions. The proppant/fiber mixture depends on a physical mechanism rather than chemical bonding to increase pack resistance to flowback. There are no minimum closure stress, temperature, or shut-in time requirements associated with the use of this technology, which increases the flexibility available to the operator to optimize well turnaround and production strategy.

This paper reviews the laboratory data relevant to the understanding and application of this technology. Studies include proppant pack resistance to flowback in one- and two-phase flow, the effect of cyclic loading, aging phenomena, permeability/conductivity studies, and fluid/breaker interactions. The benefits of the technology are illustrated with field studies.
Estimating Permeability by Use of Neural Networks in Thinly Bedded Shaly Gas Sands
Authors: Malki H. A. , Baldwin J. L. , Kwari M. A.
Published: December 2007

In this paper, we develop methods of estimating permeability that use conventional log and nuclear magnetic relaxation (NMR) log data to estimate both computed permeability (by NUMAR Inc.) and Klinkenberg core-permeability measurements. The permeability estimation methods we use in this work are based on multilayer neural networks. We compare the proposed methods of estimating permeability to traditional methods in a thinly bedded siliciclastic gas reservoir in the U.S. The results of this comparison demonstrate that neural networks can be used successfully to transform conventional or NMR logs into desired permeability. The three different permeabilities predicted by use of appropriate neural networks operate by transforming (1) conventional log data into NUMAR-derived permeability, (2) conventional log data into Klinkenberg permeability, and (3) NMR echoes into Klinkenberg permeability.
Extrapolation of Historical Storm Data for Estimating Design-Wave Heights
Authors: Petrauskas C. , Aagaard P.M.
Published: December 2007

An improved method is presented for selecting offshore structure design waves by extrapolating historical storm data to obtain extreme value statistics. The method permits flexibility in choice of distribution functions through use of computerized procedures, estimates extrapolated wave-height procedures, estimates extrapolated wave-height uncertainty due to small sample size, and includes criteria for judging whether or not given wave-height values can be represented by one or more of the distributions implemented in the method. The relevance of uncertainty to selection of design-wave heights is discussed and illustrated.

Introduction

The problem of selecting design-wave heights for offshore platforms has many facets, ranging from the development of oceanographic data to the selection of the prudent level of engineering risk for a particular installation. This paper deals only with part of the problem; it describes an improved method for using the small available amount of wave-height information to estimate the extreme value statistics and associated uncertainties for the large storm waves that have a very low probability of occurrence. probability of occurrence. Hindcast wave-height information for design-wave studies usually covers a period of historical record that is shorter than the return period selected for acceptable engineering risk. Return periods commonly used for selection design waves are 100 years or more, but good meteorological data, on Which the calculated wave heights are based, can rarely be obtained for periods covering more than 50 to 60 years. As a consequence, extrapolations to longer return periods are necessary.

Present methods for making the extrapolation employ probablistic models through the use of special probability graph papers on which a family of distribution functions plot as straight lines. The wave heights are plotted vs their "plotting-position" return period, and a straight line fitted to the plotted data is extended beyond the data to estimate extreme wave heights for return periods of interest. The methods are described in periods of interest. The methods are described in numerous technical papers and books; Refs. 1 through 5 are examples.
The Case for More-Restrictive Oil Imports
Authors: Jameson Minor S.
Published: December 2007

Introduction

From the titles of this paper bind the paper by Lichtblau dealing with oil imports policy, it is apparent that the two discussions involve questions of degree, in contrast to the "pro" and "con" arguments usually presented on controversial subjects. This, in itself. is a matter of considerable significance when it is appreciated that as recently as five years ago discussions, with few exceptions, revolved around the issue of whether or not national policy as to oil imports should be restrictive or nonrestrictive.

The point of reference as to what constitutes "more" and "less" restrictive is the existing program of Government import controls under the Presidential Proclamation of March 10, 1959, as amended. A brief description of the degree of restriction under the present Government import program, therefore, will place in perspective the discussions to follow.

Standards for restrictions imposed under existing import policy may be summarized as follows:Imports (excluding residual fuel-oil) into Districts I, II, III and IV, the area east of the Rocky Mountains, are limited to 9 per cent of total petroleum demand in these districts.

JPT

P. 703^
The Effect of Surface and Interfacial Tensions on the Recovery of Oil by Water Flooding
Authors: Kennedy Harvey T. , Guerrero Erasmo T.
Published: December 2007

In this investigation, the effects of the surface tension of brine and the interfacial. tension between oil and brine on the recovery of oil by water flooding of Woodbine sand were studied. Variation of the surface forces was. obtained by the addition of small amounts of commercially available chemicals, which did not appreciably change the surface tension of the oil.

Fourteen surface-active agents, which were found to be effective in lowering the surface and interfacial tensions, were further investigated to determine the extent of their adsorption by the Woodbine Sand cores. It was found that adsorption was sufficient in all cases to prevent any substantial concentration of chemical at the flood front. The flow system was, therefore, brought to equilibrium with definite concentrations in the flood water by circulation before each test. The data thus have no relation to the results obtainable by using the chemicals in full-scale water floods, but should be helpful in predicting the performance of surface-active chemicals which are not lost by adsorption, if such can be found.

Flow tests were made on various concentrations of six chemicals selected from the 14 investigated for surface activity and adsorption, with and without the presence of gas in the core. It was found that lowering the interfacial tension had a tendency toward reducing the recovery of oil and that the reduction of the surface tension of the brine had little or no effect. A substantial beneficial effect, however, resulted from the presence of gas in the cores.

Introduction

The movement and distribution of crude oil in a porous medium are governed by such factors as surface and interfacial tensions, viscosity of the oil, pore size configuration, and wetting characteristics of the medium. The knowledge of the part played by each of these factors is limited.
Oil Recovery by a Water-Driven Steam Slug
Authors: El-Saleh M.M. , Ali S.M. Farouq
Published: December 2007

Results of an experimental study of oil recovery by a steam slug driven by a cold waterflood in a linear porous medium are described. The model included simulation of heat losses to the adjacent formations. Steam displacements were conducted, using a number of hydrocarbons and various steam-slug sizes, with the core initially containing a residual oil or irreducible water saturation.

It was found that the steam-slug displacement is more efficient in the case of light oils than for the heavier ones. The injection of cold water following steam resulted in almost total condensation of the steam present in the porous medium, with the process degenerating into a hot waterflood. The oil process degenerating into a hot waterflood. The oil recovery efficiency of the process depends on whether an oil bank is formed during the steam-injection phase and whether the oil responds favorably to a hot phase and whether the oil responds favorably to a hot waterflood.

Introduction

Steam injection has been shown to be an effective oil recovery method both by field and laboratory tests. However, the method has the inherent disadvantages of a high cost of operation and excessive heat losses. The modification discussed here consists in the injection of cold water after a slug of steam, which helps to offset the above disadvantages partly at the expense of oil recovery. The injected water serves to propel the oil bank formed ahead of the steam-invaded zone and transports the heat contained in the steam-swept zone farther downstream, thus leading to more complete utilization of the heat injected.
Reservoir Fracturing - A Method of Oil Recovery From Extremely Low Permeability Formations
Authors: Wilsey L.E. , Bearden W.G.
Published: December 2007

This paper presents results of analysis of the effect of fracturing on initial flow rates and on ultimate recoveries from low capacity oil formations. This analysis shows that even in formations of permeability as low as 0.1 md, large fracture treatments can yield oil recoveries and production rates approaching those of high permeability formations. Field production information is shown which supports the analytical work.

Introduction

Often hydrocarbon bearing formations are discovered which, while they are known to contain large quantities of oil, will not produce at commercially attractive rates without special well stimulation. Attempts to solve this problem led to the development of such techniques as underreaming, shooting, acidizing, and recently hydraulic fracturing. These methods of stimulation have been highly successful in many fields. All of these treatments, however, affect only the pay section near the well bore and therefore owe their success to circumventing and overcoming local permeability reduction about the well bore.

It has been the belief that in treating wells to stimulate production in which there is no permeability reduction near the well, the maximum possible production rate increase would be of the order of two or fourfold. Hence, it has been concluded that fracture treatment of uniformly low capacity (permeability times thickness) formations could meet with but limited success.

It is the purpose of this paper to show that the use of fracture treatments much larger than usually used can yield commercially attractive producing rates and high recoveries even in formations of permeability less than 0.1 of a md.

Procedure

In order to illustrate the effects of fracturing, an analytical study of some hypothetical systems was made in which one factor at a time was varied to show what is important in recovering oil from fractured wells.
Clarifying Oilfield and Refinery Waste Waters by Gas Flotation
Authors: Ellis M.M. , Fischer P.W.
Published: December 2007

Gas flotation is a method of removing residual oil and suspended solids from oilfield and refinery waste waters. Because the system has a history of generally effective performance and because the equipment involved requires little space, it appears that flotation could be a desirable way of handling some very big problems.

Introduction

For more than 20 years the Union Oil Co. of California has used gas flotation as an effective means of removing residual oil and solids from many waste waters before disposing of them. Proper selection of equipment, flotation gas, demulsifiers, coagulants, and other factors makes it possible to tailor the flotation process for optimum treatment of most waste waters. Relatively small space requirements and minimum retention times are important - sometimes essential - features of gas flotation equipment.

Increasingly stringent waste-disposal requirements dictate a new look at the advantages and practical limitations of this method.

Waste waters can be clarified in many ways, each method having its own advantages and limitations. Surge vessels, skim ponds, API separators, and lagoons are adequate if the oil is not emulsified, if few entrained solids are present, and if there is adequate space or retention time. Coalescing filters can often improve the performance of these simple systems by helping to break emulsions and by trapping oily solids and slimes. Often, chemical demulsifiers or coagulants are also effective. Combinations of these systems have been used for many years with varying degrees of success. For example, a random sampling of coalescing tanks produced the varying results shown in Table 1. The quality of treated waters depends less on coalescer capacity and throughput than upon the presence of emulsions and the type of solids in the water.

However, there are many locations where adequate space is not available for conventional equipment, and others where clarification must exceed the levels obtainable by the older methods. In these locations, gas flotation should be considered.

Principle of Flotation Principle of Flotation Gas flotation speeds tip the gravity separation of oil droplets and dispersed solids from waste water. According to Stokes' law, the vertical movement of a particle through a fluid is expressed as particle through a fluid is expressed as

where

V = rate of rise or fall of the particleg = gravity constantpf = density of the fluidpp = density of the particleD = deiameter of the particlemu = viscosity of the fluid

Gas flotation modifies two of the variables listed above: particle density and particle diameter.

JPT

P. 426
The Role of Gravity in Capillary Pressure Measurements
Authors: Szabo Miklos T.
Published: December 2007

This paper shows on a theoretical basis how saturation profiles are influenced by gravity during the measurement of profiles are influenced by gravity during the measurement of capillary pressures in porous samples. A precise method is suggested for calculating the realistic capillary pressure curves from the data obtained in either the "diaphragm" or the "gravity drainage of long vertical core" method. A capillary pressure curve, free of the influence of gravity, can be determined by the equations developed in this paper from measurement of the pressures applied in the nonwetting phase and from the average saturations corresponding to capillary equilibria. The same equations may also be used for the evaluation of centrifuge data, provided the increase in capillary pressures is achieved by gradual lengthening of end-effect absorbers set up under the test sample, using the same constant speed of rotation at each run.

Introduction

The disc method is usually referred to in the technical literature as a standard method for determining capillary pressure curves. This study shows that using this method a certain pressure curves. This study shows that using this method a certain saturation distribution can be observed in the samples when the viscous fluid flow has ceased. The description of this phenomenon led to equations that offer a more precise formulation of the results obtained by the disc method. In addition, this formulation simplifies the "gravity drainage of long vertical cores" method because it is now sufficient merely to determine average saturations. Thus, it is unnecessary to determine saturations by electric methods or by the weighing of sectors of the drainage column.
Solubility of Sulfur in Hydrogen Sulfide and in Carbon Disulfide at Elevated Temperature and Pressure
Authors: Roof Jack G.
Published: December 2007

The solubility of sulfur in hydrogen sulfide has been determined by an absolute method at 21 combinations of pressure and temperature within the range of 1,020 to 4,520 psia and 110 deg. to 230 deg. F. respectively. Results, which appear to be consistent within about 2 percent, show the solubility to increase with pressure along an isotherm but to pass through maxima along isobars. Where direct comparison can be made, our values differ drastically from published results at lower pressures and are in serious disagreement at higher pressures.

The solubility of sulfur in carbon disulfide is reported for pressures from 1,020 to 5,020 psia at 150 deg. F. No published data were found for direct comparison. Both the solubility of sulfur and the density of saturated solutions decrease with increasing pressure at this temperature.

Introduction

Difficulties in production arise when a fluid containing a high content of hydrogen sulfide occurs in a reservoir in which elemental sulfur is present Changes in pressure and temperature present Changes in pressure and temperature can cause deposition of dissolved sulfur from hydrogen sulfide-rich fluids in both the formation and the production tubing. The first step in a study of this problem is to determine the solubility of sulfur in pure hydrogen sulfide under conditions of interest in production. This report presents results of one such study. Values published in the literature generally appear to be grossly in error.

In some approaches to repairing the damage caused by sulfur plugging of formation and tubing, carbon disulfide is used as a solvent. Experiments were run at a typical temperature of 150 deg. F and elevated pressure to obtain basic data on the solubility of sulfur in carbon disulfide.
Conditioning of Water by Removal of Corrosive Gases
Authors: Weeter R.F.
Published: December 2007

The general conclusion is that the removal of oxygen from injection water is usually worthwhile, but the removal of hydrogen sulfide is much more expensive and more difficult to justify. Only in isolated instances has it been found necessary to remove carbon dioxide where there is no hydrogen sulfide.

Introduction

During the past 15 years the oil industry has become more and more aware of the importance of corrosive gases in injection water in the economics of secondary recovery of oil.

Experience indicates that removal of hydrogen sulfide to a level of 1 to 2 ppm in the absence of oxygen reduces corrosion to acceptable rates at a neutral pH and that reduction below 1 ppm is possible with existing equipment. If oxygen is reduced to 0.1 ppm in sweet water or brine at a neutral pH, corrosion will be reduced to a negligible rate, but the oxygen must be reduced still more in a system containing small amounts of sulfide. The principal effect of carbon dioxide in water is the reduction in pH, with resultant solubilization of iron. Until recently, however, removal of such gases has not gained the interest of the industry at large. Several successful operations followed by published papers have aroused interest to the extent that a review of the means available appears to be in order.

Discussion

Oxygen Removal

For many years corrosion due to oxygen in water has been accepted as a necessary evil. It was thought that the water itself was the corrosive medium; therefore, subsurface water was permitted to come in contact with air as it was pumped to the surface and stored in open tanks.

With present knowledge, the prudent operator cements his water-supply well to the surface, seals the wellhead and tests to determine whether dissolved oxygen is native to the water. If it is not, and if oxygen-free natural gas is available, a gas blanket is placed on supply wells and tanks. Often this is the only action necessary.

If there is dissolved oxygen native to the water, however, some other action must be taken for the following reasons.Pitting-type corrosion, typical of an aerated system, can cause failures even in a fresh-water system and much more rapidly in a brine system.Iron oxides and hydroxides are serious plugging agents that will increase injection pressures and decrease injection rates. These compounds may result from corrosion or from a mixing of one water containing oxygen with another containing dissolved iron.Aerobic bacteria, algae, and slime form in the system, create plugging, and enhance pitting.If an oxygen-bearing water is mixed with a hydrogen-sulfide-bearing produced water, free sulfur will be precipitated.
Study of Undersaturation During Repressuring and Supersaturation During Flow of Oil to Wells
Authors: Higgins Ralph V.
Published: December 2007

This paper concerns the magnitude of the amount of supersaturation that occurs in an underground reservoir during the flow of oil and gas to wells and to the amount of undersaturation that occurs during repressuring of an oil reservoir where some effective permeability to gas exists.

The study is based on earlier laboratory findings of other investigators on the rate of diffusion of gas in oil as a function of the depth of oil. Utilizing these relationships and the principles of reservoir mechanics, a quantitative estimate of undersaturation and supersaturation was calculated. The results showed that the diffusion of the gas is rapid enough that for all practical purposes no supersaturation exists during the flow of oil to wells or undersaturation during repressuring in reservoir sands having some effective permeability to gas.

The reason diffusion of the gas virtually keeps the oil saturated is the long time required in radial flow for oil to reach the well and the slow rate at which pressure in reservoirs is increased during repressuring.

Introduction

Knowledge of the phase relationships during flow of gas and oil in an underground reservoir is essential to operating the reservoir in the most efficient manner. In material-balance calculations and in fluid-flow studies, the oil is assumed to contain all the gas that it will dissolve at given temperature and pressure. Pressure-volume-temperature relationships are normally obtained in the laboratory using "bottom-hole" or combined samples of the reservoir fluids. In such laboratory determinations equilibrium is obtained between the oil and gas in the pressure cells by mechanical agitation. During the flow of oil and gas in reservoirs, however, no comparable agitation occurs to mix thoroughly these fluids to aid in effecting equilibrium between the two phases.
Chemical Enhancement of the Biodegradation of Crude-Oil Pollutants
Authors: Robichaux T.J. , Myrick Nugent H.
Published: December 2007

These test results establish two important processes for dealing with oil in an aquatic environment. First, the rate of biological destruction of hydrocarbon can be increased by emulsifying the oil with a suitable chemical agent. Secondly, biological destruction can be further accelerated by seeding the emulsion with microorganisms that can use hydrocarbon as a food source.

Introduction

This study was conducted to determine the effects of chemical dispersants on the microbial decomposition of crude oil in aquatic environments. Lin and Townsley reported that lignosulfates increase the rate of fermentation of hydrocarbons in water. They attributed the increased rate to the large surface area and to the efficiency of cell-to-oil contact provided by the emulsifier. Not all dispersing agents promote bacterial growth. Some agents are quite toxic and will retard the rate of oil decomposition. Other agents form loose, unstable emulsions and have little effect on the reaction.

Biological oxidation of any organic matter is basically the utilization of the substance as a food source. The organic matter is synthesized by bacterial oxidation to new cells and converted to energy and metabolism end products such as CO2 and water. The growth of the microorganism is dependent upon the individual metabolic requirements of the organism, the chemical nature of the organic matter and the physicochemical environment. The growth process is physicochemical environment. The growth process is related to surface area, as the interfacial area increases, the growth rate increases. Thus dispersing oil through a water phase increases both the availability of the organic matter and the surface area. The rate of microbial utilization should also increase.

The response of microorganisms to dosage with anionic or nonionic surfactants is highly variable. The structure of the surfactant molecule, its concentration, and the type of solvent used as a carrier influence the toxicity to microorganisms. The surfactants, by their effects on cell membranes, have a marked influence on the uptake of other chemical substances.

Experimental Data

In the laboratory work for this study, a preliminary evaluation was made to select a suitable method for observing the effects of several chemical formulations on microbial activity in a water-and-oil environment Methods for following oxygen uptake were compared and the Warburg technique was chosen. This technique, using 125-ml reaction flasks and aqueous manometers, provided the required sensitivity and allowed the samples to be large enough to he prepared accurately. prepared accurately. A sample of crude petroleum was used as a "standard" oil throughout the work. The standard was a sweet, paraffin-base oil, weathered to approximate oil stored for several days at atmospheric pressure and ambient temperature. The sample was stored for the duration of the investigation under conditions that prevented further change in composition.

Both fresh- and sea-water conditions were studied.

JPT

P. 16
Development of a Sea-Ice Penetrometer
Authors: McIntosh J.A. , Young Wayne C. , Welsh J.P.
Published: December 2007

Introduction

For the past several years the U. S. Coast Guard has pursued a research and development program intended pursued a research and development program intended to lead to the ability to reconnoiter large expanses of sea ice by fixed-wing aircraft without hindrance by weather or darkness. This capability is necessary if our country is to exploit the natural resources of our northern regions. A key requirement for our reconnaissance capability is the ability to measure the thickness of the sea ice from the air, since the thickness is a major determinant of its trafficability.

Sea ice is a complex medium that is virtually impossible to duplicate in the laboratory. In addition, its properties conspire to frustrate most techniques for the remote measurement of its thickness. Numerous techniques have been investigated for remotely measuring sea-ice thickness, most without success. Sonic sounding has been tried by numerous investigators, but the high signal attenuation, poor signal-to-noise ratio, and indistinct ice-water boundary has defeated almost all experiments of which we are aware. Likewise, most methods involving electromagnetic radiation have been unsuccessful, although one or two ideas have begun to show some promise. (It should be pointed out that fresh ice, such as forms on the Great Lakes, while possessing certain complexities of its own, is more amenable to remote measurement than sea ice.)

Considering the above, the Coast Guard's Office of Research and Development decided to fund the development of some approach radically different from the sonic and electromagnetic techniques we have mentioned.

Since drilling is the only technique for measuring the thickness of sea ice that is accepted without reservation by the community, the first thought was "lets drop something on the ice, have it drill a hole, measure the thickness, and radio it up to us in the aircraft."

JPT

P. 249
Gas Well Stimulation with a Viscous Water-Base Fracturing Fluid
Authors: Seidel W.R. , Stahl E.J.
Published: December 2007

Field experience with high-viscosity fracturing fluids shows that they are highly effective, particularly in stimulating wells with bottom-hole temperatures of 200 degrees to 400 degrees F. The propped-fracture length and fracture conductivity are greater than with low-viscosity fluids; consequently, productivity is greater. Also, abandonment pressures can be lowered, which means additional reserves.

Introduction

A viscous, water-base, non-Newtonian fracturing fluid has been used successfully to stimulate seven Wilcox (Upper Eocene) and two Vicksburg (Lower Oligocene) gas wells. The bottom-hole temperatures of the completions ranged from 240 degrees to 330 degrees F. The average gas production increase was 2.8 MMcf/D, compared with 0.7 MMcf/D for treatments performed on similar wells treated with low-viscosity performed on similar wells treated with low-viscosity fluids.

The principal application of this high-viscosity fluid is in the stimulation of reservoirs with bottom-hole temperatures ranging from 200 degrees to 400 degrees F. Use of the fluid results in wider fractures, placement of proppant at higher concentrations, and better proppant distribution than is achieved with low-viscosity fluids. The improvement in response has been attributed to greater fracture conductivity and greater propped-fracture length.

Treatment Results

The total daily production of nine wells treated with the viscous fluid was increased from 16.6 to 40.6 MMcf, with the average Q/Qo being 3.2. (Q/Qo is the ratio of production rates after fracturing to production rates before treating.) In determining Q/Qo, increased tubing pressure and tubular friction were neglected. Depths of the completion intervals ranged from 8,000 to 12,000 ft. All of the treatments were performed on wells that were greater than 50 percent pressure depleted. Calculated closure stresses on the propped fractures ranged from 5,000 to 9,000 psi. Other pertinent well and treatment data are given in Table 1. pertinent well and treatment data are given in Table 1. Stimulation results previously obtained on comparable completions using low-viscosity fluids had been discouraging. Data on five such treatments performed on Wilcox gas wells are presented in Table 2. In the table below the average well data and results of these stimulations are compared with results of seven treatments on Wilcox completions using the viscous fluid.

High-Viscosity Low-ViscosityFluid (7 wells) Fluids (5 wells) Net pay, ft 49 38 Bottom-holePressure, psi 1,390 1,550 Original bottom-holepressure, psi 3,900 3,900 Average productionincrease, MMcf/D 2.8 0.7 Average Q/Qo 3.6 2.2 Profitable operations 7 2 Profitable operations 7 2 Uneconomicaloperations 0 3

Stimulation treatments using the high-viscosity fluid have yielded greater response under similar well conditions than have treatments with low-viscosity fluids. Improved stimulation response is attributed to longer propped fractures and higher fracture conductivity than could be obtained with low-viscosity fluids.

JPT

P. 1385
Measuring the Quality of a Reservoir Management Program
Authors: Holstein E. D. , Berger A. R.
Published: December 2007

Good reservoir management is key to successful exploitation of hydrocarbon resources. Sustaining quality reservoir management programs can be a challenge in view of cross functional, cross group requirements plus personnel and priority changes. Reservoir management processes have been defined and a set of questionnaires has been designed to comprehensively review reservoir management practices, assess its strengths, identify areas for improvement, and provide a method to measure improvements over time.
SACROC Unit CO2 Flood: Multidisciplinary Team Improves Reservoir Management and Decreases Operating Costs
Authors: Hawkins J. T. , Benvegnu A. J. , Wingate T. P. , McKamie J. D. , Pickard C. D. , Altum J. T.
Published: December 2007

In 1992, the economic viability of the SACROC Unit was somewhat uncertain. At that time, a multidisciplinary team was formed to improve operational efficiencies and reservoir performance. Better understanding of reservoir geology from detailed biostratigraphic analysis provided the framework to make effective changes. This paper discusses operational efficiency and reservoir exploitation projects implemented by the team.