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By Roscoe C. Clark

In October 1945. R. F. Farris. in an AIME paper entitled Method For Drtermining Minimum Waiting OIL Cenzent Time, presented a method for caiculating the minimum WOC* time required in oil well cementing operations. Briefly. this method consisted of shutting in a well. after the cement had been placed and noting the time required fur the wellhead pressure to reach a. maximum. This time was then multiplied by a factor of 1.5 to determine when the cement had reached sufficient strength to support the weight of the casing. As a result of this work, a number of areas have reduced their WOC time ~Wuirements with the subsequent saving of considerable rig time. The tests conducted by Farris were, for the most part, conducted under cementing temperatures in excess of 70°F. This was done because in the overwhelming majority of cases. cementing temperatures are in excess of 70°F (only in tile northern part of the country. primarily in the Rocky Mountain ares. in cementing surface casing are temperatures below 70° F. encountered, and such temperatures occur only during the winter months). The Stano-lind Research Laboratory since that time has performed a number of tests both in the laboratory and in the field to evaluate this WOC factor when cemeriting temperatures are lower than 70°F. The results of these tests indicated the need for greater WOC time in areas affeaed by abnormally low cementing temperatures. These tests indi.cated that a woc factor of 2 (Time from start to mix cement to maximum wellhead pressure x 2 = Time to drill plug) will allow sufficient time for the cement to develop adequate strength. A field test under abnormally low cementing temperatures (surface temyerature 35°F., mud discharge temperature <70°F. and cementing depth 500 ft.) in the Rangely Field, "* using the WOC factor of 2, indicated the time to drill the plug as 45 hours. Well conditions preventing getting back into the well until a 48-hour WOC time had elapsed. At this time, the plug drilled firm to hard indicating that the cement had reached its final set. It is contemplated that during next winter additional field tests will be performed to further check the results of the laboratory and field tests conducted to date,

Jan 1, 1949

By Roscoe C. Clark

In October 1945. R. F. Farris. in an AIME paper entitled Method For Drtermining Minimum Waiting OIL Cenzent Time, presented a method for caiculating the minimum WOC* time required in oil well cementing operations. Briefly. this method consisted of shutting in a well. after the cement had been placed and noting the time required fur the wellhead pressure to reach a. maximum. This time was then multiplied by a factor of 1.5 to determine when the cement had reached sufficient strength to support the weight of the casing. As a result of this work, a number of areas have reduced their WOC time ~Wuirements with the subsequent saving of considerable rig time. The tests conducted by Farris were, for the most part, conducted under cementing temperatures in excess of 70°F. This was done because in the overwhelming majority of cases. cementing temperatures are in excess of 70°F (only in tile northern part of the country. primarily in the Rocky Mountain ares. in cementing surface casing are temperatures below 70° F. encountered, and such temperatures occur only during the winter months). The Stano-lind Research Laboratory since that time has performed a number of tests both in the laboratory and in the field to evaluate this WOC factor when cemeriting temperatures are lower than 70°F. The results of these tests indicated the need for greater WOC time in areas affeaed by abnormally low cementing temperatures. These tests indi.cated that a woc factor of 2 (Time from start to mix cement to maximum wellhead pressure x 2 = Time to drill plug) will allow sufficient time for the cement to develop adequate strength. A field test under abnormally low cementing temperatures (surface temyerature 35°F., mud discharge temperature <70°F. and cementing depth 500 ft.) in the Rangely Field, "* using the WOC factor of 2, indicated the time to drill the plug as 45 hours. Well conditions preventing getting back into the well until a 48-hour WOC time had elapsed. At this time, the plug drilled firm to hard indicating that the cement had reached its final set. It is contemplated that during next winter additional field tests will be performed to further check the results of the laboratory and field tests conducted to date,

Jan 1, 1949

By J. Gordon Parr, D. H. Polonis

RYSTALLOGRAPHIC relationships between martensitic a&apos; (close-packed-hexagonal) and retained fi (body-centered-cubic) have been studied in binary alloys of titanium with manganese, molyb- denum, chromium, and iron.&apos;" In these investigations, the habit planes of the martensitic phase were determined, as well as the orientation relationships between martensitic and parent phases. In each alloy

Jan 1, 1957

By J. E. Burke

THE origin of recrystallization textures continues to be a matter of controversy. One explanation is that a recrystallization texture occurs because only grains having a limited range of orientations ever appear in the deformed matrix—the oriented nuclea-tion* hypothesis. Another explanation is that grains essentially having all orientations are nucleated but that those having certain orientations grow much more rapidly than any others in the deformation texture, and thus only the rapidly growing grains survive when recrystallization is complete. There has recently appeared a great deal of evidence&apos;- indicate that recrystallized grains of face-centered cubic metals are frequently related to their parent grains by rotations of 20" to 40" about a common [lll] direction. Furthermore, it has been observed that the growth rate of the new grains depends upon their orientations with respect to the matrix, and that the most rapidly growing grains lie within the stated range of orientations. In a recent note, Beck7 has concluded from observations of this type that oriented growth alone is responsible for the appearance of preferred orientations in re-crystallized metals. It should be pointed out. however, that many of the available data indicate that oriented nucleation operates in addition to oriented growth. Thus, while oriented growth may permit a selection to be made among nuclei of several orientations, only a limited number of orientations are available in the first place for such selection.

Jan 1, 1953

By Paul A. Beck

THE occurrence of the (100) [lOO] or "cube" texture upon annealing of cold-rolled copper has been much investigated.&apos; The conditions favorable for its formation were found to be a high final annealing temperaturez or long annealing time," a high reduction of area in cold rolling prior to the final anneal,&apos; and a small penultimate grain size." The effects of penultimate grain size and of rolling reduction were found by Cook and Richards4 to be interrelated in such a way that any combination of them giving lower than a certain value of the final average thickness of the grains in the rolled material leads to a fairly complete cube texture with a given final annealing time and temperature. Also, according to the same authors, at a higher final annealing temperature a larger average rolled grain thickness, i.e., a lower final rolling reduction, is sufficient than at a lower temperature. These somewhat involved conditions can be understood readily on the basis of recent results obtained at this laboratory. Hsun Hu was able to show recently by means of quantitative pole figure determinations that the rolling texture of tough pitch copper, which is almost identical with that of 2s aluminum: may be described roughly as a scatter around four symmetrical "ideal" orientations not very far from (123) [112]. In the case of aluminum, annealing leads to retain-ment of the rolling texture with some decrease of the scatter around the four "ideal" orientations, and to the appearance of a new texture component, namely the cube texture." A microscopic technique, revealing grain orientations by means of oxide film and polarized light, showed that the retainment of the rolling texture is achieved through two different mechanisms operating simultaneously, namely "re-crystallization in situ," and the formation of strain-free grains in orientations different from their local surroundings, but identical with that of another component of the rolling texture. Thus, a local area in the rolled material, having approximately the orientation of one of the four "ideal" components of the texture, partly retains its orientation during annealing, while recovering from its cold-worked condition, and it is partially absorbed at the same time by invading strain-free grains of an orientation approximately corresponding to that of another "ideal" texture component. The reorientation here, as well as in the formation of the strain-free grains of "cube" orientation, may be described as a [Ill] rotation of about 40°, see Fig. 1 of ref. 6. The preferential growth of grains in such orientations is a result of the high mobility of grain boundaries corresponding to this relative orientation.&apos; " It appears very likely that in copper the mechanism of the structural changes during annealing is similar to that observed in aluminum (except for the much greater frequency of formation of annealing twins in copper). In both metals the new grains of cube orientation have a great advantage over the new grains with orientations close to one of the four components of the rolling texture. This advantage stems from their symmetrical orientation with respect to all four retained rolling texture components of the matrix; they are oriented favorably for growth at the expense of all of these four orientations. As a result, the growth of the "cube grains" is favored over the growth of the others, as soon as the new grains have grown large enough to be in contact with portions of the matrix containing elements of more than one, and preferably of all four component textures. It is clear that this critical size is smaller and, therefore, attained earlier in the annealing process if the structural units, such as grains and kink bands, representing the four matrix orientations are smaller, i. e., if the average thickness of the rolled grains is smaller. Hence, for a given annealing time and temperature, a smaller penultimate grain size and a higher rolling reduction both tend to increase that fraction of the annealing period during which the above condition is satisfied. Consequently, the percentage volume of material assuming the cube orientation increases. The same is true also for increasing time and temperature of annealing when the penultimate grain size and the final rolling reduction are constant, since the average size attained by the new grains during annealing increases with the annealing time and temperature. For the same reason, at higher annealing temperatures a given volume percentage of cube texture can be obtained with larger rolled grain thickness (larger penultimate grain size, or smaller rolling reduction) than at lower annealing temperatures. The well-known conspicuous sharpness of the cube texture may be interpreted as a result of the fact that selective growth of only those grains is favored that have an orientation closely symmetrical with respect to all four components of the deformation texture and exhibit, therefore, a high boundary mobility in contact with each. The effect of alloying elements in suppressing the cube texture, as described by Dahl and Pawlek,&apos; appears to be associated with a change in the rolling texture. For face-centered cubic metals, such as copper, which do exhibit the cube texture upon annealing, the rolling texture is always of the type described above, i. e., scattered around four "ideal orientations" of approximately (123) [112]. The addition of certain alloying elements, such as about 5 pct Zn or 0.05 pct P in copper, has the as yet unexplained effect of changing the rolling texture into the (110) 11121 type. This texture consists of two fairly sharply developed, twin related components. In such cases, as in 70-30 brass and in silver, the annealing texture again is related to the rolling texture by a [lll] rotation of about 30°, however, because of the different rolling texture to start from, it has no cube texture component. At higher temperatures, both in brassm and in silver," grain growth leads to a further change in texture: A [lll] rotation of the same amount, but in reversed direction, back to the original rolling texture.

Jan 1, 1952

By O. Katz, A. Spilners, M. Simnad

THE oxidation of titanium has been studied in recent years by a number of investigators.&apos;-W ne of the most important aspects of the reaction of titanium with oxygen, which has been observed by several of the investigators, is the extremely high solubility of oxygen in the metal. A detailed study of the Ti-0 systeml% as shown that the solubility limit of oxygen in a-titanium is approximately 14.5 wt pct 0 from 800" to 1700°C. The unusual oxidation behavior of titanium may be ascribed to this phenomenon, since part of the oxygen uptake enters into solid solution in the metal and only a part is available for scale formation. A more complete study of the kinetics of oxidation of titanium would require information on the influence of oxygen in solution in the metal upon the oxidation rate. Such information would also be of interest in regard to the theory of oxidation of metals. The authors have measured the oxidation rates of oxygen-saturated and oxygen-free titanium between 800" and 1200°C and have found appreciable differences in their rates of oxygen uptake and in the activation energies. The experimental set-up was similar to that described in a previous paper.u The course of oxida-dation was followed continously by attaching the specimen to a sensitive spring balance and observing the extension of the spring with time of oxidation. High purity electrolytic oxygen was used and precautions were taken to purify the gases employed. The specimens were prepared from iodide titanium and were ground on metallographic polishing papers to a fineness of 4/0. The furnace was first evacuated and filled with argon; the specimen was lowered into the furnace, which was then evacuated and filled with oxygen, after the specimen had reached the oxidation temperature in argon. The samples were presaturated with oxygen by means of the following procedure: Each specimen was first heated in oxygen at 1200°C until its increase in weight indicated 13.8 pct by weight uptake of oxygen. The furnace was then immediately evacuated and filled with purified argon five times. The specimen was heated in the argon atmosphere for a period of 72 hr at 1200°C in order to saturate the metal with oxygen by complete absorption of the scale. The temperature was lowered to the oxidation temperature, the furnace was evacuated and filled with oxygen, and the oxidation rate was followed by noting the extension of the spring balance. No oxide film was visible on these specimens at the start of the oxidation experiments. Titanium samples in the oxygen-free as-received condition were also oxidized and their oxidation rates measured. The results are shown in Figs. 1, 2, and 3, which indicate that the initial rates of uptake of oxygen by both the oxygen-saturated and oxygen-free specimens are parabolic at these temperatures. The rate of uptake of oxygen is, however, appreciably lower

Jan 1, 1956

By L. D. Wooddy, Robert Moscrip

The simultaneous solution of the volumerric balance and the unsteady-state equation has been used for several years to make performance calculations for combination drive reservoirs. This method makes possible the calculation of volumetric changes of fluids in the gas cap, oil zone, and aquifer which occur as a result of withdrawals and reservoir pressure changes. It does not provide a means for the determination of reservoir fluid distribution changes corresponding to these vollrmetric changes. A knowledge of the fluid saturation distribution in the reservoir at various stages of depletion is important for the determination of the efficiency of gas and water as oil-displacement media and, therefore, for the reliable predicrion of ultimate oil recovery. To provide this knowledge, the displacement equations are solved simultaneously with the volumetric balance and unsteady-state equations. The described calculation procedure has been used satisfactorily to analyze the past performance and to predict the future behavior of combination drive reservoirs under both primary and pressure-maintenance operations. INTRODUCTION The three basic mechanisms by which oil is displaced from a reservoir are: (1) dissolved gas drive—the displacement of oil by the expansion of liberated solution gas, (2) water drive—the displacement of oil by water which enters the oil zone from the aquifer, and (3) gas cap drive—the displacement of oil by gas which ex- pands into the oil zone from the gas cap. The action of gravitational forces may be effective in increasing the efficiency of the basic drive mechanisms. Gravitational forces favor the segregation both of gas and oil and of oil and water, thus tending to shorten the transition zone between oil and displacing fluids. Most reservoirs produce under the influence of a combination of these drives and are designated "combination drive reservoirs". Fig. 1 is a cross section of a typical combination drive reservoir. A calculation procedure for analyzing the performance of combination drive reservoirs has been developed by combining the displacement equations&apos; with the volumetric balance equation&apos; and the unsteady-state equations. The pressure-production performance and the positions of the gas-oil and oil-water contacts are calculated for several stages of reservoir depletion by solving these equations simultaneously, thus affording a basis for: 1. Determining instantaneous and ultimate oil, gas, and water production under various operating conditions. 2. &apos;Establishing a maximum efficient rate of production, 3. Determining the advantages of pressure maintenance and unitization, and 4. Designing surface installations necessary for primarv and pressure-maintenance operations. DEFINITIONS The calculation procedure for combination drive res-

Jan 1, 1957

By C. W. Spencer, F. N. Rhines, R. J. Knight

Ametallographic study has been made of the peritectoid transformation as it occurs in two Ag-A1 alloys, containing 6.0 and 6.9 wt pct Al, respectively. After equilibrating at 475°C, these alloys were transformed isothermally just below the peritectoid temperature which lies at about 450°C.1-3 Peritectoid transformation in this alloy system consists in the reaction of a and 5 to form µ. The crystal structures of the a, µ, and 5 phases have been determined as face-centered-cubic, 6 manganese, and hexagonal-close-packed, respectively. At the peritectoid temperature their equilibrium compositions are approximately 5.85, 7.02, and 7.24 wt pct (19.92, 23.2, and 23.8 atomic pct) aluminum."" The transformation might be expected to occur principally at the interface between the a and 5, but such is not the case. Instead, the major part of the transformation occurs by the direct (and perhaps initially diffusionless) conversion of 5 to µ. The composition range of the forming µ nearly overlaps that of the parent at the temperature of transformation" so that little, if any, composition change is required. Transformation proceeds by the nucleation of µ at points upon the external surface of the sample and sweeps through the 5 phase, leaving the a initially almost undisturbed. Subsequently, the a phase participates in the transformation by being partly or totally converted to µ. Specimens approximately 1/4 x 1/4 x 1/16 in. were cut from cast ingots, previously equilibrated 68 hr at 588°C. The specimens were held for 3 hr at

Jan 1, 1958

By B. F. Peters, J. Gordon Parr, E. R. Macgregor

A SERIES of seven hypoeutectoid alloys, up to 18.2 atomic pct Mn, was made by the levitation melting technique. The loss of weight on melting was considered to be entirely due to volatilization of manganese, and compositions were computed on this basis. Filed samples (—200 Tyler mesh) were helium quenched from 1000°C after soaking for 5 min by a technique already described.&apos; Quenched Alloys -Assessments of the amounts of a phase produced and the hardness of the quenched alloys are summarized in Fig. 1. The experimental techniques and calculations involved have been described previously. The amount of a decreases as manganese content increases, until at 10.6 pct Mn only a trace of a&apos; is observed. Previous

Jan 1, 1957

By Stephen Krickovic

AS it is commonly understood in the bituminous coal mining industry, pillaring means removal, as completely as is practical, of all pillars formed in the development of headings and rooms on first mining. The degree to which this can be accomplished, termed percent of recovery, is of course dependent generally upon the physical conditions of the bottom and the overburden, the system of min-

Jan 1, 1956

By F. D. Wright, H. D. Fara

The solution to the plastic and elastic stresses around a circular shaft in a hydrostatic stress field that has appeared in two editions of a widely used book on rock mechanics1 is in error. Although this is a relatively minor matter, the correct solution was not found by a literature survey, so it appears worthwhile to present it. For a homogeneous, isotropic, rigid plastic-elastic body in plane strain which obeys Tresca&apos;s yield criterion the following equations must be satisfied:&apos;," In the plastic zone,

Jan 1, 1963

By B. L. Averbach, M. Cohen, G. P. Conard

IT has been frequently observed that, when metal crystals are bent and annealed or when they are bent at elevated temperatures, the asterism of the Laue spots is split discontinuously into tiny intensity maxima. This finding indicates that segmented crystallites or subgrains are produced, which are relatively undistorted within themselves but which differ slightly in orientation from their neighbors. The following viewpoints have been put forward concerning the nature of this segmentation process: 1—Crussard&apos; has described the phenomenon as "re-crystallization in situ." According to this mechanism, the deformed lattice recrystallizes on heating into an aggregate of comparatively strain-free subgrains separated from one another by low-angle boundaries and having nearly the same orientation as the original crystal. This process differs from the classical type of recrystallization in that the latter involves the formation of grains having quite different orientations from that of the mother crystal. 2—A similar but more detailed picture has been advanced by Cahn&apos; who adopted the term "polygonization." In this interpretation, the plastic bending of lattice planes results in an excess of dislocations of one sign, but at suitable temperatures these dislocations migrate along slip planes and collect in localized regions to form an array of low-angle boundaries. Concurrently, the lattice segments between the boundaries lose their curvature and elastic strain. 3—The "cell formation" concept of Wood and co-workers: unlike the two hypotheses cited, postulates that the segmentation of the lattice is basically a mode of deformation and is not an annealing phenomenon. Cell formation appears to compete more effectively with respect to the normal slip process as the deformation temperature is increased and as the strain rate is decreased. The present work was performed on 3.2 mm diameter 99.99&apos; pct Zn single crystals, grown from the melt in a gradient furnace. The major impurity was 0.003 pct Fe. The crystal orientations ranged from those with basal plane parallel to the rod axis to those with the basal plane almost perpendicular to the rod axis. The specimens were bent on templates to effective radii varying from 14.2 to 1.3 cm at the temperatures from —196" to 100°C. In each case, the axis of bending was parallel to the basal plane. Subsequent annealing was carried out at temperatures from —196" to 400°C. Back-reflection Laue pictures were taken on the convex surface of the bent specimens, before and after annealing. This procedure was found to yield better resolution of the detail in the diffraction spots than did the previously used Laue transmission technique. Some X-ray pictures of rods bent at —196" and —78°C were taken at these respective temperatures without intermediate warming to room temperature. In addition, bent crystals were acid cut" parallel to the basal plane, and double-crystal spectrometer rocking-curves were obtained from the etched (0001) face before and after increment an-

Jan 1, 1954

By L. J. Klinkenberg

It is pointed out that the current concept of pore size distribution is not unequivocally defined and that different methods aiming at a determination of such a distribution therefore do not lead to the same results. A pore size distribution should not be based on the idea that a core should, under all circumstances, behave as a bundle of straight non-interconnected capillaries of the same pore size distribution. This is illustrated by calculations and experiments on the displacement of miscible liquids. INTRODUCTION The introduction of the concept of pore size distribution has been an attempt to characterize the intricate geometry of the flow channels in porous media. As pores in a porous medium are interconnected it is impossible to describe exactly what is meant by a "pore" and, therefore, the term pore size distribution requires further amplification. In the visual method for the determination of pore size distribution "the pore" is considered to be the hole between the grains as observed on thin sections or on a polished surface of the rock under a microscope. In all other presently known methods,1,2 a displacement process is studied and it is ascertained what as- semblaae of straight cylindrical capillaries would show the same behavior. The distribution of the capillary diameters of this assemblage is said to represent the size distribution of the pores of the actual porous medium. From the foregoing it is already apparent that it is useless to try to decide which process or which method of investigation leads to a "correct" pore size distribution. To illustrate this further a displacement process in which a fluid is displaced by another miscible with it will be discussed and the results will be interpreted in terms of a pore size distribution. DISPLACEMENT EXPERIMENTS WITH MISCIBLE LIQUIDS OF NEARLY IDENTICAL VISCOSITY AND DENSITY Interpretation in the Form of a Pore Size Distribution If distilled water is displaced from a homogeneous unconsolidated sand pack by, for instance, a dilute solution of NaCI, the breakthrough recovery i.e., the amount of distilled water produced at the moment the first trace of NaCl can be detected in the effluent water, is between 95 and 100 per cent of the pore volume of the pack. This result can be understood by following in imagination the course of one particle of the liquid. Imagine a length, ?l, at the end of which a liquid particle has an independent chance of a renewed choice of pores of different diameters. In other words, the particle has a choice of traveling time, at, for any length ?l; instead

Jan 1, 1958

By Jack L. Lytton, Oleg D. Sherby

RESULTS of recent investigations1 on the creep of metals at high temperatures have revealed that the activation energies for creep of pure metals, AH,., about equals the respective activation energies for self-diffusion, hHD. This fact strongly suggests that the rate-controlling process in creep at high temperatures might be that of dislocation climb, as first postulated by Mott.&apos; It would be desirable, however, to relate the creep rate of a metal at a given temperature and stress with actual diffusivity data, rather than with a comparison of the tempera-

Jan 1, 1957

By L. D. Mullins, H. B. Bradley

Numerous articles have appeared in the literature citing the application of the potentiometric analyzer to cycling operations. Specific information obtainable by a potentiometric analysis, as noted by various investigators, includes: 1. Pattern sweep efficiency for various injection and production rate programs. 2. Injected fluid breakthrough time at production wells. 3. Optimum production and injection rates. 4. Prediction of injection and/or production well locations. 5. History of advance of the in-jected-produced fluid interface. 6. Ultimate life of the reservoir. 7. Ultimate reservoir production. This note describes a procedure for predicting pressure distribution in a gas-condensate reservoir by using the potentiometric analyzer to obtain potential distribution data on an analog model of the reservoir and then applying Muskat&apos;s&apos; equations. The method relates the volumetric weighted average datum pressure to the mean potential in the model.

Jan 1, 1958

By F. E. Steigert, A. H. Geisler

THE permanent magnet alloy comol, which contains 17 pct Mo, 12 pct Co, balance Fe, exhibits a precipitation reaction analogous to that at the iron end of the binary Fe-Mo system. The equilibrium precipitate, (P,), has a structure isomorphous with Fe,Mo, which is rhombohedra1 with parameters a = 8.97A and a = 3038.6&apos; according to the work of Arnfelt and Westgren.&apos; In the ternary alloy the parameters are a = 8.87A and a = 31°0.5&apos;. Oscillating crystal patterns of a single matrix crystal, M, in which P, was precipitated by slow cooling from 1300°C, showed that the orientation relationship of the two lattices is as follows: (110)P3 // (110)* (111)p3 // (110)m There are crystallites of P, in 12 different orientations in a single crystal of the parent solid solution. Microscopic examination shows that the crystallites are generally plate-like with their lateral dimensions parallel to (110) matrix planes. When precipitation in a supersaturated alloy quenched from 1300°C progressed isothermally at temperatures between 600" to 800°C, the evolution of the P, structure could be traced. Diffuse diffraction effects in Laue patterns provided early evidence of the precipitation process. Analyses of these by a previously described technique2 showed that they corresponded to rod-like elements parallel to <110> matrix directions in reciprocal space. With further aging to promote growth of the precipitate, the rod-like elements contracted to points in reciprocal space for normal Bragg reflection from the precipitate as shown by the left diagram in Fig. 1. Thus the diffuse scattering was attributed to the small thickness of the plate-like particles which was inadequate for sharp diffraction. When the precipitate particles were first thick enough to give normal diffraction their structure was different from that of the equilibrium precipitate, P,. The first structure, P1, presumably is a coherent transition struc-

Jan 1, 1952

By L. M. Howe, J. Gordon Parr, E. Saarema

THE decreasing solid solubility limit at the titanium-rich end of the Ti-Cu constitutional diagram,&apos; Fig. 1, suggests the possibility that titanium-rich alloys may be age-hardenable. However, results obtained by Holden et al. reproduced in Fig. 2 show that after quenching from 790°C the age-hardening of an alloy containing 1.7 pet Cu is very slight, while a 0.8 pet alloy decreases in hardness, during heat treatment at 400°C. It was believed possible that powder samples of alloys might show different results from the lump samples used by Holden et al., since small particles are often more sensitive to diffusion processes than larger samples. Consequently, a 1.9 pet (by weight) Cu alloy was made by the technique of levitation melting," checked for homogeneity, and filings of 48-65 Tyler screen size were cut from it for aging experiments. The filings were helium-quenched (by a technique described previously)&apos; from 790°C, sealed in vacuo in silica tubes and aged at temperatures of 400°, 450°, and 500°C. Microscopic and X-ray examinations failed to reveal any structural changes during the aging process. This is not too surprising since early stages of precipitation do not usually manifest themselves in ways that are readily detectable by metallographic methods, and the extent of precipitation on overaging a 1.9 pet alloy is very small. However, hardness readings (taken on a Bergs-man micro hardness tester, using a 25 g load applied to a diamond indenter) do show a hardness peak at each aging temperature, Fig. 3. About a dozen readings were taken on each heat treated sample; the highest reading and the lowest reading were ignored and an average taken of the remaining values. In

Jan 1, 1957

By Carl E. Johnson

INTRODUCTION A method for predicting water-flood oil recovery was reported by H. Dykstra and R. L. Parsons&apos; in 1950. It is now generally known as the Dykstra-Parsons method and is widely used by petroleum engineers. The method is semiempirical and consists of a correlation of four fundamental variables. These are: V, vertical permeability variation;&apos; a, mobility ratio; Sw initial water saturation; and R, fractional recovery of oil in place at a given producing water-oil ratio. The correlation extends over a wide range in each of these variables, and may be applied to all formations with initial oil saturations of 45 per cent or greater. The method of calculation originally outlined by Dyhtra and Parsons closely follows their derivation. And this is a convenient way of illustrating the development of some rather complicated ideas. However, in actual use it is more cumbersome than necessary. The purpose of this note, therefore, is to provide a simplified method for making Dykstra-Parsons predictions. A SIMPLIFIED GRAPHICAL SOLUTION The correlation between V, a, Sw and R, corresponding to a given producing water-oil ratio, can be shown on a single graph. This is best done by plotting V against a to show lines of constant R(1 - S, . WOR-0.2). Figs. 1, 2, 3, and 4 show these plots

Jan 1, 1957

By C. Goldberg, R. H. Wynne

WHEN using an optical goniometer to determine crystal orientation&apos; it is advantageous to use a preferential etchant so that the etch pits have plane faces which are parallel to crystallographic planes, all of which are of the same "form." "Westinghouse Silver Etch" (WAg), a preferential etch for germanium, is made up as follows: 40 ml of 49.7 pct hydrofluoric acid, 20 ml of 70.7 pct nitric acid, and 40 ml of distilled water containing 2.0 g of silver nitrate. Examination of metallographs of WAg etched surfaces (Fig. 1, for example) indicates that, regardless of crystal orientation, the faces of the etch pits are (111) surfaces. Optical goniometer examination of these WAg etched surfaces also indicates that the faces of the etch pits are (111) surfaces, i.e., all bright reflections are from (111) planes. When using an optical goniometer of the type described by Barrett,&apos; not only (111) reflections from a WAg etched germanium surface but also other reflections of lower intensity will be observed. These latter reflections can cause confusion. We have used an optical goniometer made from a war surplus astrocompass and a galvanometer lamp. The reflections are observed by using the goniometer in a darkened room and letting the reflected light be in- cident upon a piece of white paper. The resulting decrease of goniometer sensitivity enables (111) reflections only to be observed. This in turn permits the crystal orientation to be determined in a matter of minutes, since only two measurements are necessary. The authors wish to acknowledge the help received from R. E. Davis who assisted in making the metallographs and aided the authors in the interpretation of the metallographs.

Jan 1, 1954

By W. D. Roberts

INTERGRANULAR corrosion of metals and alloys has been extensively investigated and the current conclusions are summarized in the Symposium on Stress-Corrosion Cracking of Metals.&apos; It appears, however, that the relative importance of the various factors involved in the mechanism is still obscure. Several recent, independent studies, in combination with available X ray data op preferred orientation, indicate that there may be a direct correlation between relative orientation of contiguous grains and susceptibility to intergranular corrosion. The object of the present note is to show the nature

Jan 1, 1951