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By G. T. Jackson

The Alaska Gastineau Mining Co.'s mine is located at Perseverance, about 4 mi. east of Juheau, Alaska. Its property consists of a group of claims, the lode system traversing these claims for a distance of 11,000 ft. (3352 m.). It is shown in Fig. 1. The ore deposits occur in what is known as the Juneau gold belt. This gold belt can be traced for about 50 mi. northwest of Juneau and 40 mi. southeast. It consists of a single band, several hundred feet wide, in which stringers and veins of quartz, carrying gold, occur in a slate formation near its contact with some altered volcanic rock known as greenstone. The Perseverance orebody consists of stringer lodes, having a strike northwest and southeast, dipping about 60° to the northeast. These

Jan 1, 1920

Executive JOHN R. SUMAN, Chairman PAUL D. MERICA, Vice-Chairman CHESTER A. FULTON W. M. PEIRCE H. Y. WALKER Finance H. T. HAMIL'T'ON, Chairman ERLE V. DAVELER HENRY KRUMB Admissions FELIX E. WORMSER, Chairman GEORGE D. BARRON, Vice-Chairman PHILIP KRAFT EDWARD MEAGHER CLYDE E. WILLIAMS

Jan 1, 1941

By H. Foster Bain

(San Francisco Meeting, October, 1911.) [SECRETARY'S NOTE.-This paper, presented in oral abstract, at the San Francisco meeting, was not at first supposed by Mr. Bain to be required for publication in the Transactions; and the excursion to Japan, in which he took part, immediately after the San Francisco meeting, delayed his presentation of the manuscript. After his return to San Francisco, Mr. Bain, in view of the importance of his paper and its discussion, kindly furnished it in full. The delay in its publication (since it was received in April last) has been due, partly to the circumstance that other contributions had meanwhile acquired the "right of way," and partly to the consideration that, the situation contemplated in Mr. Bain's paper having remained practically unchanged, the paper and its discussion would not lose force or timeliness by this lapse of time.-J. S.] No acute observer of public affairs can have failed to observe a growing disposition on the part of the public to change emphasis in government from political equality to social justice. When our own government was founded it was felt to be sufficient to secure to each individual the fullest possible freedom of opportunity, and such a scheme was excellently adapted to the rapid development of a large territory having a small population. As the number of people in a given area increases, there are more points of contact and conflict; each must move in a smaller orbit, and there must be more regulation. Germany is making faster progress in industry than is any other country. The principal reason is the insistence there on team-play. In Germany there are fewer multimillionaires and more socialists (spelled with either a big or little " S ") than in any other of the leading countries; but Germany wins trade and is steadily improving the conditions of life for her citizens. To some, the change from the freest individualism is welcome; to others it is intensely unacceptable. To this fundamental difference in view-point may be imputed much of the vigor with which the controversy regarding coal-lands has been waged. That present conditions in Alaskan coal-fields are extremely unsatisfactory is generally recognized, but there are wide dif-

Aug 1, 1912

STANDING COMMITTEES Executive-SIDNEY J. JENNINGS, chairman. Membership-KARL EILERS; chairman. Finance-GEORGE D. BARRON, chairman. Library-E. GYBBON SPILSBURY, chairman. Papers and Publications-BRADLEY STOUGHTON, chairman. Nominations-R. V. NORRIS, chairman. Institute of Metals Division-WILLIAM M. CORSE, chairman; FRED L. WOLF, secretary, Ohio Brass Co. Mansfield, Ohio.

Jan 12, 1918

In the Philippines, where distances are spoken of in terms off fight time, the Sipalay copper mines are two flight hours southeast of Manila on the island of Negros. After landing at the airport in Bacolod, it is then 170 km (106 milers) by surface transportation to Marinduque Mining and Industrial Corp.'s expanding copper operation. While copper deposits were discovered in the area in 1936-and one mine, the Binulig, began operations soon after-it wasn't until 1956 that stripping at Sipalay and construction of a 4000-t/d (4400-stpd) mill began. The mill went into operation in May 1957, and the first shipment of copper concentrate was made three months later.

Jan 8, 1978

By C. W. Dunham

FOR discharging and diffusing the gases from the reverberatory furnaces and converters the Morenci Reduction Works has been provided with one of the largest reinforced concrete chimneys ever built. It is 612 ft. high from the bottom of the foundation to the cap at the top, and has a minimum diameter of 24 ft. inside the lining near the top and 38 ft. 10 in. at the bottom. Its estimated capacity, at the elevation of 4338 ft. above sea level, is about 1,000,000 cu.ft. of gas per minute at a temperature of 500° F. and an atmospheric temperature of 90°. Under these conditions the draft will be at least 3 in. of water at the flue inlet. The gases enter the chimney through a steel balloon flue 33 ft. high and 15 ft. wide, the bottom of which is 19 ft. above the ground.

Jan 1, 1942

C. N. FEnner, New York City (communication to the Secretary) : A possible explanation of some of the' phenomena of amalgamation cited by Mr. Bayliss and others has occurred to me. We know that if, to a quantity of mercury, gold and silver are added until a putty-like paste is formed, and if this mass is spread on a flat surface and pressure is applied, a more fluid portion of the mercury will be squeezed out from the rest, carrying gold and silver with it. The proportion of gold to silver will depend, I think, upon various causes and conditions—the relative chemical affinity which gold and silver have for mercury; the amount of pressure used; the presence of other metals:

Jan 1, 1898

By Clyde E. Williams

THROUGHOUT its history the American iron and steel industry has constantly striven to improve the quality and reduce the cost of its products. No one needs to be told how well it has succeeded. Its success in making steel products at such a low cost has been achieved mainly through large-scale production. While costs have gone down as the rate of production and the degree of mechanization increased, quality of product has been actually improved. Thus high-tonnage records are important only in the light of high quality of the steel. Quality is the watchword! Continual improvement in quality has come as a result of research, not only in the laboratory but in the large commercial units in the plant. In fact, so many operations of the industry are on such a huge scale that experimental work must be done under commercial operating conditions so every progressive steel plant is a research laboratory.

Jan 1, 1938

By AIME AIME

Award of a Gold Medal : to the Institute. The Jury of Awards of the Jamestown Ter-Centennial Exposition has conferred a gold medal, the highest distinction within its power,. on the American Institute of Mining Engineers for the excellence of its publications during the past decade. ; A half-tone photographic reproduction of both sides of the medal is given in the accompanying illustration.

Jan 7, 1908

By Waldemar Lindgren

Introduction To the miner, as well as to the geologist, the eastern part of Cuba is a most interesting region. Here we find, in contrast to the moderate relief predominating elsewhere in the island, an imposing mountain range, the Sierra Maestra, extending east and west parallel to the coast, its precipitous front facing the blue Caribbean Sea.. In a geological sense this range is largely an unknown land, the only well-explored region being that in the vicinity of Santiago. The range also contains the most important mineral deposits of the island. They comprise, first, a series of iron deposits yielding a partly hematitized magnetite with low content of phosphorus; second, a remarkable copper-bearing vein at El Cobre; and third, various manganese deposits. Probably more deposits will be found, for the larger and western part of the range is as yet little explored and its slopes are covered by a thick tropical jungle. The following notes are based on a short visit by the senior author in January and February of 1914 to the mines at Daiquiri, El Cobre, and Mayari. For many courtesies and great assistance he is deeply obliged to Charles F. Rand, President of the Spanish-American Iron Co.; to George W. Pfeiffer, General Manager, and to the several members of his staff.

Jan 10, 1915

Executive R. C. ALLEN, Chairman ERLE V. DAVELER, Vice-chairman WILDER JUDSON R. M. ROOSEVELT G. B. WATERHOUSE Finance H. G. MOULTON, Chairman HENRY KRUMB PAUL D. MERICA H. T. HAMILTON, Consultant Admissions W. B. HEROY, Chairman GEORGE D. BARRON, Vice-chairman H. T. HAMILTON PHILIP KRAFT W. A. SINSHEIMER

Jan 1, 1937

Executive DEGOLYER, Chairman SIDNEY H BALL RICHARD PETERS, JR WILLIAM H BASSETT J V W REYNDERS Finance GEORGE D BARRON, Chairman H A GUESS GEORGE OTIS SMITH Membership J M CALLOW, Chiarman FRANK L ESTEP WILBER JUDSON GEORGE D BARRON H N SPICER Alternates P A MOSMAN EDWARD B STURGIS

Jan 1, 1923

By Dell P. Williams, Howard G. Nelson

The tensile behavior of magnesium single crystals at a temperature of 26º ± 2ºC was investigated at varying pressure levels from 760 to 8 X 10-8 tow. For crystals deformed at a constant linear strain rate of 0.061 min-1. there was no apparent effect of the vacuum environment down to 10-8 torr. However, from a vacuum of 10-5 torr down to the lowest pressure attained (8 x 10-8 tor,), the effect of the vacuum environment was to increase the strain at the end of the first linear (or easy-glide) stage and to decrease the slope of this stage; the magnitude of this effect was found to be dependent on pressure. The slope of the second linear stage was also decreased at the lower pressure levels; however, this effect appears to be caused primarity by the vacuum effect on the first linear stage. The magnitude of the vacuum-environmrnt effect was also found to be dependent upon strain rate. The reduction in flow stress at 5 x 10-8 torr, as compared to the stress in air, was obserced to be about 10 pct for a strain rate of 0.0250 min-' and 70 pct for a strain rate of 0.67 min-1. No systematic effect of pressure on the critical resolvled shear stress was observed. The data interpreted in terms of a modified form of Mott's work-hardening mechanism for hexagonal metals. It has long been known that surface conditions influence the mechanical behavior of materials. Roscoe 1 demonstrated the importance of surface conditions on mechanical behavior by testing cadmium crystals with oxide layers. He found that the "apparent" critical resolved shear stress for cadmium was increased approximately 2.5 times by the presence of an oxide layer 1000 atoms thick. The magnitude of this effect was dependent on film thickness with crystals having films less than 20 atoms thick still showing a definite increase. This observed strengthening could not be attributed to any strength of the oxide film because of 1) the thinness of the films and 2) an observed increase in the flow stress as deformation proceeded. Harper and cottrel12 obtained similar results on zinc crystals which had been etched and steamed to give artificially thick oxide films. However, in the course of this study, they also carefully examined the very early stages of plastic flow for zinc crystals which in one case had been electrolytically polished and in the other had been lightly etched to produce a thin film. They then found that the critical resolved shear stress for both surface treatments of the crystals was actually identical but that the etched crystal exhibited a much more rapid initial hardening rate. This had not been noted previously. This result indicated that, in fact, the film caused an increase in the stress for continuation of slip, rather than for the initiation of slip. Lipsett and King3 investigated the effect of evaporated gold films on the plastic behavior of cadmium single crystals. For large angles (=75 deg) between the specimen axis and the normal to the slip plane, they found that the stress-strain curve of the coated specimen always lies above that for a clean specimen. The shear strain at the end of the first linear stage was greater in clean specimens than in coated specimens and the slope of the second linear stage was

Jan 1, 1965

John Duer Irving, who left his post as Professor of Economic Geology at the Sheffield Scientific School, New Haven, Conn., to join the Eleventh Regiment of Engineers shortly after the declaration of war, died in France, July 26, 1918, from an attack of pneumonia. Through the initiative of Mr. Benjamin B. Lawrence, a memorial service to Captain Irving was held at St. Paul's Chapel, Columbia University, on Sunday afternoon, August 4, which was' attended by members of Captain Irving's family, and about four hundred of his friends from Columbia, Yale, the American Institute of Mining Engineers and the Association of the 11th Regiment of Engineers. Professor James F. Kemp delivered the memorial address, and has prepared for the Institute the following account of Captain Irving's life, Professor Kemp and Captain Irving having been associated on the most intimate terms for a number of years. , The war has brought home to friends and kin in the western shores of thc Atlantic many losses whose suddenness has the shock of a blow. Many more will follow, but none can leave a sharper sense of regret than the news that the keen and productive mind; the inspiring teacher; the successful and considerate editor, the fine, true man and friend had all passed away when John Duer Irving made the final great gift to the service of his country, in the cause of decency and right. In the closing days of July, the cable brought the tidings that toward midnight on the twentieth of the month pneumonia had proved too great a tax upon one already worn by excessive labors. John Duer Irving was born in Madison, Wis., August 18, 1874. His father, Roland Duer Irving, was at the time professor of geology, mineralogy and metallurgy in the State University of Wisconsin.' Roland . Irving, the father, had entered Columbia College in 1863, but trouble with his eyes compelled him to suspend his studies in the classical course in his sophomore year, and to replace study with some months of life and travel in England. Ultimately his eyes became stronger, and he entered the School of Mincs, completing the course for the degree of Engineer of Mines in 1869, with the third class graduated. The class of eleven contained other future geologists. It numbered on its roll Henry Newton and Walter P. Jenney of the early survey of the Black Hills, where John, future son of Roland, was in the course of years to make his doctor's dissertation, and with its publication his really serious entrance into the profession. Roland Irving was a favorite student of Professor J. S. Newberry, affectionately known to all of his students as "Uncle John," and after some experience in mining and smelting in Pennsylvania and New Jersey, joined the Ohio Survey under Dr. Newberry. The work in Ohio was largely performed during the vacations of the University of Wisconsin, to whose chair Roland Irving was called in 1870. Later, his residence in Wisconsin led to two events of prime importance in the history of American geology. He began the study of the Gogebic iron range and caught the clue to the origin and stratigraphy of the iron ores of all the Lake Superior ranges; and he later undertook the mapping and description of the copper-bearing rocks of the Lake Superior basin. The formative years of the son, John, were passed in a home where the father.

Jan 1, 1920

By M. J. Pool, with Appendix by Larry Kaufman, R. W. Krenzer

Thermodynmic properties of the Cu-Mn system have been deterrrzined in the temperature range 973" to 1273°K by measuring the vapor pressure of manganese in equilibrium with alloys of compositions varying from 0.13 to 0.91 rnole fraction manganese using the Knudsen effusion technique. Activities of manganese calculated from the measured vapor pressures show large positive deviations. Calculated heats and entropies of mixing are positive with a maximum occurring at approximately 0. 7 mole fraction manganese. ThE investigation of thermodynamic properties of binary systems involving transition metals is of considerable interest at the present time. The incomplete subvalency electron levels of transition metals lead to unusual behavior in some alloys, and considerable information can be obtained by determining the thermodynamic characteristics of these systems and relating the thermodynamic behavior to observed physical properties. The Cu-Mn system, shown in Fig. 1,' provides an example of an alloy system in which the determination of the equilibrium phase diagram and various physical properties has received considerable attention, but very little work has been done on measurement of the thermodynamic properties. Elemental copper and manganese have comparable electronegatives, atomic sizes, and cohesive energies, but differ in crystal structure. They form a continuous series of solid solutions only at high temperatures and the structure varies in a continuous manner from fcc at the copper-rich end to fct at the manganese-rich end.' The purpose of this investigation was to measure the vapor pressure of manganese over a series of Cu-Mn alloys and from these values determine the thermodynamic properties of the binary system. Vapor pressure measurements were made in the temperature range 973" to 1273"K, remaining within the solid-solution region for each alloy studied. EXPERIMENTAL PROCEDURE The relative thermodynamic properties of solid Cu-Mn alloys were determined from vapor pressure measurements by means of the Knudsen effusion tech- nique. Several discussions of the theory can be found in the literature. In the case of copper and manganese, it is assumed that manganese is the only component subliming, so the vapor pressure of manganese over the various alloys can be determined directly by measuring the weight loss of the effusion cell. This is a valid assumption since the vapor pressure of manganese is about four orders of magnitude higher than the vapor pressure of copper in the temperature region of interest. The vapor pressure of manganese over the alloys at any given temperature is then related to the weight loss of the effusion cell per unit area per unit time. An upper limit of 1.5 x 10"s has been measured for the ratio of polyatomic to monoatomic molecules for manganese vapor in equilibrium with solid manganese at 1180°K, so it was assumed that manganese vapor is monoatomic. The effusion cells, fabricated from high-purity alumina, are 26 mm high, 18 mm OD, and have a wall thickness of 1 mm. Three different sized holes of 2.03, 2.54, and 3.18 mm diam were drilled in the lids from the inside face to minimize chipping, and the lids were then slip-cast onto the cells to provide a gas-tight seal. Alumina was selected for this particular application both because of its resistance to thermal shock and reaction with manganese vapor. In the ideal case, the orifice of the effusion cell should have a knife edge so that effusion through the orifice

Jan 1, 1970

By C. E. Shoenfelt

There was a notable decrease in drilling operations in 1940 in all of the Rocky Mountain states except Montana, where the two large fields on the Canadian border, Cut Bank and Kevin-Sunburst, were espe-cially active. The expanding markets for Montana natural gas made necessary the more intensive development of such fields as Rowdoin, Cedar Creek and Devon. While there were no important oil and gas discoveries in 1940 in any of the Rocky Mountain states, a few small pools were opened, which may constitute separate areas but may prove with later development to be extensions of old fields. Some of the old fields were extended and deeper pay zones were discovered in others. These have given the areas greatly increased oil reserves and therefore are just as important as the discovery of new fields. The more important of the developments in 1940 are given, by states, in the following paragraphs. Colorado Hiawatha Field, Moffat County.—The Mountain Fuel Supply Co. began the development at Hiawatha of its oil reserves, which were discovered in about 1929, and late in the summer oil began moving from the field by truck to the shipping point at Rock Springs, Wyoming. The Hiawatha field of northwestern Moffat County was discovered in 1927 by the Sormir Petroleum Co., with the completion of No. r Florence Wilson for 4,5,000,000 cu. ft. of gas a day from a Wasatch sand lens at 2200 it. In later development of the field, oil showings were reported in several wells but no development of this resource was undertaken until 1940, when a test of the oil possibilities was started with the release in April of a location for No. 5-A Wilson on the S\W. SW. NW. of sec. 23-1zN-1ooW., on the east side of the field. The Well had an initial production of 327 bbl. of oil a day pumping from three Wasatch (Tertiary) sands between 2005 and 2540 ft. It was drilled to 2562 ft., where the 65/8-in. casing was cemented and gun-perforated at 2005 to 2125 ft., 2260 to 2335 ft. and 2513 to 2540 ft. At the end of the year, this well was averaging zoo bbl. of oil per day, pumping. Two other wells were drilled for oil on Hiawatha during the summer—one a small well of 60 bbl. per day and the other a small gas well. Powder Wash Field, Moffat County.—The development of the Powder Wash field in northwestern Colorado was resumed in 1940 by the Mountain Fuel Supply Co., with the release of a location for No. 2-A Musser in the CWL.NW.SE. of sec. 4-1rN-97W. The Powder Wash field was discovered in 1931 by the Mountain Fuel Supply Co. and the discovery well, No. I Musser, on C.NW. of sec. 5-IIN-97W., was completed at 2152 ft. in the Hiawatha member of the nonmarine Wasatch for-mation for an open flow of 34,000,000 cu. ft. of gas per day under a natural pressure of 685 lb. per sq. inch. Oil was discovered in the Powder Wash field on Nov. 26, 1936, in the company's No. I Carl Allen on the NE.SW.SE. of sec. 32-12N-97W. The oil production was

Jan 1, 1941

By C. E. Shoenfelt

There was a notable decrease in drilling operations in 1940 in all of the Rocky Mountain states except Montana, where the two large fields on the Canadian border, Cut Bank and Kevin-Sunburst, were espe-cially active. The expanding markets for Montana natural gas made necessary the more intensive development of such fields as Rowdoin, Cedar Creek and Devon. While there were no important oil and gas discoveries in 1940 in any of the Rocky Mountain states, a few small pools were opened, which may constitute separate areas but may prove with later development to be extensions of old fields. Some of the old fields were extended and deeper pay zones were discovered in others. These have given the areas greatly increased oil reserves and therefore are just as important as the discovery of new fields. The more important of the developments in 1940 are given, by states, in the following paragraphs. Colorado Hiawatha Field, Moffat County.—The Mountain Fuel Supply Co. began the development at Hiawatha of its oil reserves, which were discovered in about 1929, and late in the summer oil began moving from the field by truck to the shipping point at Rock Springs, Wyoming. The Hiawatha field of northwestern Moffat County was discovered in 1927 by the Sormir Petroleum Co., with the completion of No. r Florence Wilson for 4,5,000,000 cu. ft. of gas a day from a Wasatch sand lens at 2200 it. In later development of the field, oil showings were reported in several wells but no development of this resource was undertaken until 1940, when a test of the oil possibilities was started with the release in April of a location for No. 5-A Wilson on the S\W. SW. NW. of sec. 23-1zN-1ooW., on the east side of the field. The Well had an initial production of 327 bbl. of oil a day pumping from three Wasatch (Tertiary) sands between 2005 and 2540 ft. It was drilled to 2562 ft., where the 65/8-in. casing was cemented and gun-perforated at 2005 to 2125 ft., 2260 to 2335 ft. and 2513 to 2540 ft. At the end of the year, this well was averaging zoo bbl. of oil per day, pumping. Two other wells were drilled for oil on Hiawatha during the summer—one a small well of 60 bbl. per day and the other a small gas well. Powder Wash Field, Moffat County.—The development of the Powder Wash field in northwestern Colorado was resumed in 1940 by the Mountain Fuel Supply Co., with the release of a location for No. 2-A Musser in the CWL.NW.SE. of sec. 4-1rN-97W. The Powder Wash field was discovered in 1931 by the Mountain Fuel Supply Co. and the discovery well, No. I Musser, on C.NW. of sec. 5-IIN-97W., was completed at 2152 ft. in the Hiawatha member of the nonmarine Wasatch for-mation for an open flow of 34,000,000 cu. ft. of gas per day under a natural pressure of 685 lb. per sq. inch. Oil was discovered in the Powder Wash field on Nov. 26, 1936, in the company's No. I Carl Allen on the NE.SW.SE. of sec. 32-12N-97W. The oil production was

Jan 1, 1941

By Robert T. MacMillan

Of all the mineral substances utilized by man, salt or sodium chloride has one of the longest and most varied histories. Because all animal life is descended from marine organisms, sodium and chlorine became necessary to life, and as sodium chloride meets requirements most readily, common salt has been essential to human and animal diets from earliest times. As civilization progressed, man learned to evaporate sea water and brines of saline lakes and springs to obtain salt, and gradually ceased to depend on the flesh of animals and the occasional salt outcrops or "salt licks" they frequented. He also learned that salt had a multitude of uses, particularly as a preservative of meat and other foods. The importance of salt in the minds of early men may be readily seen from many allusions in the Bible and other ancient writings. Expressions such as "not worth his salt," and "the salt of the earth" are deeply embedded in the English language. Salt has symbolized friendship, fidelity, purity, and hospitality. It has been used as currency; had religious significance; caused wars; and has been a favorite commodity for taxation. The English word "salary" stems from the Latin word for salt, in which Roman soldiers received part of their pay. Although salt today retains its dietary importance, it has thousands of other uses. Of each 100 pounds produced in the United States less than three pounds is for table use. The other 97 pounds goes for agricultural, industrial, and chemical uses. Fortunately, reserves of salt are enormous and reasonably well distributed on the face of the earth. The sea is an inexhaustible source of salt which may be had at prices which vary with climate and other factors. In addition, large underground salt deposits and many salt lakes, springs and playas are scattered throughout the world. Most countries have access to a salt supply, although some are more favored than others. Properties Crystallized sodium chloride or common salt is known as halite. Its molecular weight is 58.454 and it contains, by weight, 39.34 pct sodium and 60.66 pct chlorine. Alternate positions in the cubic lattice are occupied, respectively, by negative chloride and positive sodium ions; the crystal form is isometric. Crystallization from water produces concentric shells, and when broken, a crystal shows conchoidal fracture. Salt has a hardness of 2.5; its specific gravity ranges from 2.1 to 2.6 for rock salt and is 2.165 for the pure crystal. The refractive index is 1.554; it melts at 800.8 ± 0.5°C and boils at 1413°C. Its heat of fusion is 123.59 cal/ gram. Salt is transparent or translucent and highly diathermous. It is colorless when pure and has a vitreous luster. Salt containing traces of iron oxides has varying shades of yellow, orange, brown, pink, or red. The peculiar shade of red sometimes found in that produced by solar evaporation of sea water has been attributed to tiny organisms. Blue mottlings sometimes seen in halite crystals have been attributed to colloidal sodium. Salt is soluble in water to the extent of 35.7 parts per 100 parts of water at 0°C and 39.8 parts per 100 of water at 100°C. The small difference in solubility with increasing temperature is important in the economics of producing salt by evaporating brine. Salt has a negative heat of solution which is 1.281 kg-cal/ mole at 18°C in 200 moles of water.

Jan 1, 1960

By W. J. Joslin

The frontal-advance equation can determine how the fluid withdrawal rate and subsurface operating pressure influence oil recovery from pressure-maintained reservoirs having characteristics favorable for efficient vertical segregation. For effective vertical segregation in formations having low dip angles, the requirements are: thick, massive sands, low viscosity oil and high vertical permeability with few discontinuous shale members. This approach has been successfully applied to the LL-370, which is a massive Eocene sandstone reservoir containing crude with an average gravity of 26" APT, a dip of only 3" and vertical permeability of ½ darcy. The average gas cap saturation was calculated for various rates of vertical gas-oil contact movement corresponding to a wide range of reservoir producing rates. This method also evaluated the effect of different pressure maintenance levels on oil recovery. Applicability of this procedure for calculating the present oil saturation in the LL-370 gas cap has been substantiated from field performance, where the oil saturation was computed by comparing oil recovery with the gas cap volume vacated. INTRODUCTION During the natural depletion history of the LL-370 reservoir, located in Lake Maracaibo, Venezuela, excellent vertical segregation resulted in the formation of a thin gas zone over a substantial portion of the oil-productive area. Subsequently, gas injection forced this thin gas-saturated zone slowly downward, reducing the oil saturation in the gas cap to a low value. The oil recovery has been raised considerably above earlier predictions where vertical segregation effects were under-estimated. In order to determine the maximum efficient producing rate and optimum operating pressure for this reservoir, a vertical gas frontal-advance analysis has been made through application of the fractional flow equation. LL-370 RESERVOIR CHARACTERISTICS The reservoir consists of a truncated monocline of massive. highly-permeable Eocene sandstone, called the B-b formation, covering an area of more than 13,500 acres. The original oil in place was 2.17 billion STB. Internal non-sealing faults subdivide the structure into four blocks called the B-6-x.6, 10, 11 and 13, which are effectively bounded by major faulting on the flanks, an unconformity updip to the west, and an immobile aquifer to the southeast. The producing formation occurs at an average depth of 5,250 ft subsea and has a closure of more than 1,500 ft. A typical producing section has a net oil sand thickness of 170 ft. Scattered throughout the section are a few randomly-positioned shale lenses which increase in thickness and areal extent downdip. The reservoir rock and fluid properties vary with depth. The permeability and produced oil gravity are 1600 md and 28" API at the top, compared to 300 md and 18° API at the water-oil contact. The productivity of updip wells is, therefore, much higher than the reservoir average. The reservoir oil was originally saturated at the crest, grading to a slight degree of undersaturation at the water-oil contact. There was no original gas cap; and material balance and the field performance indicate no water influx. Except for the northern B-6-x.6 block, the fluid and rock properties have already been published.' Average LL-370 reservoir properties are shown in Table 1. RESERVOIR PERFORMANCE UNDER NATURAL DEPLETION Fig. 1 shows production performance from 1939 to date. Early development was gradual, with 30 wells pro-

Jan 1, 1965

By I. R. Kramer

The delay time for single crystals of iron, zinc, and pre-strained aluminum was measured under conditions of high-speed deformation. The delay time of aluminum was found to be affected by the orientation of the crystal. Under the dynamic conditions employed, tile calculated "activated volume" term appears to be very small for the three metals studied. IN a previous paper,1 it was shown that under dynamic testing conditions at 78° K, there was a delayed yield in single crystals of aluminum and copper which had been cold-worked prior to testing. The experimental results also indicated that the delay-time effect was not due to the interaction of dislocations with impurity atoms or vacancies, but rather to a dislocation-dislocation interaction since aluminum which has not been prestrained shows no delay-time phenomenon. In this paper, some data are reported on the effects of orientation on the delay time of aluminum single crystals; the delay time of zinc single crystals saturated with nitrogen and the delay time of iron single crystals also were measured. EXPERIMENTAL PROCEDURE Aluminum (99.997 pct) and zinc (99.999 pct) crystals, 1/2 in. in diam and 8 in. long were grown by the Bridgman technique. The iron single crystal was supplied by Dr. R. Maddin. The zinc crystals containing nitrogen were prepared by melting high-purity zinc in a graphite crucible and the nitrogen was introduced by additions of ammonium chloride. The liquid zinc was then drawn up into glass tubes of 1/2 in. diam and allowed to solidify. The rods were cooled to room temperature before the transfer to the mold for conversion into single crystals. The orientation of all specimens was determined by the Laue' back-reflection technique, Fig. 2 and Table I. To prepare for the delay-time measurements, the crystals were cut with a fine jewelers saw and the ends carefully machined. The specimens then were electrolytic ally polished to remove the cold-worked metal, mounted in a special fixture and hand-lapped. As a final step, the crystals were annealed in evacuated tubes. Specimens of aluminum crystals, Nos. 24 and 26, were compressed 0.5 and 2 pct, respectively, in the direction of the later impact. The zinc specimens were aged at 50°C for 15 min, In the case of iron, only two specimens could be obtained. To obtain sufficient data, it was necessary to resort to a reaging treatment. After each delay-time test, the specimens were aged at 65° C for 100 min. This treatment, according to Clark,2 is sufficient to restore the original delay time. It is believed that although the specimens were plastically deformed approximately 10-4 pct, after each test the delay-time values are reliable. The delay-time measurements were made in an apparatus similar to that described previously.' Single crystals approximately 1 in. long and having a diameter of 1/2 in. were placed in a pendulum which consisted of a bar 1/2 in. in diam and 8 ft long, designed with a crystal holder to accommodate the specimen at low temperatures. The crystal was held at a position 2 ft from the front part of the pendulum. This portion of the apparatus was supported on a fine molybdenum wire. A projectile bar of the same diameter and length comprised the other portion of the apparatus. This bar was supported on

Jan 1, 1962