Ft In Depth Research Articles

Principal Stress Ratios in Cretaceous Limestones from Texas Gulf Coast

Study of calcite twin lamellae abundance in cores of low-porosity limestones indicates that the average number of lamellae per millimeter increases by 10 for every 5,500 ft of depth through the 20,800-ft interval sampled. The conditions of lamellae formation have been determined by creep tests on a representative limestone at several differential stress levels and loading durations at appropriate confining pressures and temperatures. Results show that (1) twin lamellae do not form when the specimens are subjected to a uniform confining pressure alone, (2) the lamellae increase in abundance with increasing differential stress, and (3) the abundance of lamellae increases with the duration of loading. Creep tests at differential stresses of 1,450-5,800 psi over durations of ,000 minutes indicate that the average number of lamellae per millimeter increases by 10/510 psi differential stress. From these results, we infer that the differential stress gradient in situ could not have exceeded about 510 psi/5,500 ft of burial and, because of the much longer time intervals in nature, this gradient probably was much less. Assuming a total vertical stress gradient of 1 psi/ft and a pore-pressure gradient of 0.5 psi/ft, we conclude that the probable maximum ratio of vertical-to-horizontal effective stresses (^sgrv/^sgrh = ^sgr1/^sgr3) in the Texas Gulf Coast is about 1.2.

Pressure Prediction with Flowline Temperature Gradients

The procedure described here is applicable anywhere in the world, from the Louisiana Gulf Coast to the South China Sea. However, in using this method to predict the existence of overpressured shale and the first overpressured sand below a shale interval, one must carefully consider many factors affecting flowline temperature response to changes in geotemperature. Introduction Abnormal pore pressure is found at very shallow depths in several areas of the world and very short pressure transition zones are often encountered. At pressure transition zones are often encountered. At one time, all methods of determining the presence of abnormal pressure depended upon drilling data accumulated after the bit had reached the transition zone or upon after-the-fact analysis of wireline logs. All methods have inherent limitations that create additional difficulties in detecting higher pressure either as the depth of abnormal pressure decreases, or as the length of the transition zone decreases, or both. A complementary procedure was needed that would not be dependent upon the amount of mud weight overbalance, upon penetration far into the transition zone, upon the nature of the rock matrix, or upon correlations of log parameters with pressure values. A method satisfying these requirements was suggested by variations observed in surface mud temperature. Detailed studies resulted in the development of a pressure prediction and detection procedure that pressure prediction and detection procedure that utilizes relationships between pore pressure and mud flowline temperature. This paper reviews theory presently associated with the flowline temperature presently associated with the flowline temperature method, discusses data collection and interpretation, and suggests further exploitation. Theory The geothermal gradient or the rate at which subsurface temperature increases with depth can be defined by ...........(1) where the gradient is expressed in F per 100 ft of depth. For any given area, the geotemperature gradient is usually assumed to be constant. While the average gradient across normal pressured horizons may be constant, higher-than-normal geothermal gradients have been found to be associated with pore-pressure gradients greater than normal. Lewis and Rose presented a theory to explain how high-pressure zones presented a theory to explain how high-pressure zones relate to departures of the geothermal gradient from the normal value. Practically all heat flowing within the earth moves outward from the molten core and is radiated into space. The total heat flowing across all depth increments is constant, but the temperature differential across any increment depends upon the ability of materials in the increment to conduct beat. Below a formation whose conductivity is relatively low, heat builds up until the temperature differential across the formation allows heat flow through the insulator to equal the flow of incoming heat. Accordingly, higher geothermal gradients must exist across insulating formations and relatively lower temperature gradients are present in formations with relatively higher conductivities. JPT P. 135

Artificial Recharge of Treated Waste Waters and Rainfall Runoff into Deep Saline Aquifers of Peninsula of Florida: ABSTRACT

Fast-growing population centers of the state of Florida, mainly in coastal beaches, have imposed large demands on the sources of fresh water. They also threaten to deteriorate the esthetic and recreational value of the area with their waste waters. The largest of these population centers is on the southeastern end of the peninsula of Florida, commonly referred to as the Miami area. The second largest is on the central west coast of the peninsula in the Tampa-St. Petersburg area. The Florida peninsula is underlain by several thousand feet of carbonate rock, with only minor amounts of clastic sediments. Cavernous limestone and dolomite aquifers at relatively shallow depths constitute the principal source of fresh water in the area. Deeper cavernous zones, separated from the freshwater zones by practically impermeable limestone and dolomite, are uniquely suited to receiving injected fluids. Deep-well disposal of waste waters into deep saline aquifers, after secondary biologic treatment and disinfection, is feasible if (1) an aquifer exists that can accept treated waste waters without significant changes in its hydraulic and structural characteristics, and (2) if use of the water in that aquifer, adjacent ones, or from surficial sources is not impaired. Two large disposal wells have been constructed for a private utility in the Miami area of southeast Florida. They are approximately 3,000 ft in depth and recharge an artesian aquifer having chloride concentrations near that of seawater (19,000 mg/l). The receiving aquifer is overlain by a thick aquiclude, by another aquifer (saline but of lower chloride concentration), and then by a thick, impervious section separating the highly mineralized waters from the shallow and fresh groundwater. Three concentric steel casings, cemented at the proper depths, permit injection into the deeper aquifer with protection of the upper strata. Monitoring of the upper saline water-bearing stratum, where any possible leak from the deeper aquifer would normally be first detected, is performed through the annulus between the 2 inner well casings. An integrated water-quality aquisition system continuously monitors the injected waste and provides an alarm and pump shut down if established limitations are exceeded. Operation of the first well for over a year has proved fully reliable, and economically advantageous. Eight similar disposal wells are being considered in the area. On the basis of this experience, a new research program is being implemented to inject, store, and recover when needed, rainfall runoff into the deep saline aquifers of southern Florida. A test-prototype well is presently being constructed within the city of St. Petersburg to determine (1) the characteristics of the deep underground formations; (2) the quality of the deep groundwaters; (3) the injection rate capacity and associated increase in pressure; (4) the ratio of the amount of fresh water that could be subsequently recovered to that injected; and (5) the quality of the recovered water. End_of_Article - Last_Page 1595------------

Comparative Biology and Ecology of Tropical and Antarctic Foraminifera: ABSTRACT

End_Page 790------------------------------Studies of shallow-water benthonic Foraminifera are under way currently at Eniwetok Atoll in the equatorial Pacific and on the Antarctic Peninsula utilizing scuba gear for direct observation of natural situations and laboratory experimentation. On the atoll, species are distributed by microhabitat without regard for depth (to at least 150 ft), whereas in Antarctica, the benthic Foraminifera do not select specific microhabitats. Instead they are zoned according to depth, mostly in association with changing macrofaunal and floral changes. Because of ice abrasion in the Antarctic, few or no Foraminifera live between the intertidal zone and 18 ft in depth. Below that, a zone characterized by large kelps, sponges, tunicates, and brachiopods contains many Foraminifera, and at 120 ft the ass ciation is dominated by large glass sponges with about 25 species of Foraminifera. Heavy predation on Foraminifera takes place on the atoll by fish and grazing invertebrates; in Antarctica, Foraminifera are fed on mostly by invertebrates. There are at least 3 nutritive strategies in reef Foraminifera, although they seem to feed largely on bacteria in Antarctica. Like some tropical species, some Antarctic ones seem to live a long time (years) before reproducing. End_of_Article - Last_Page 791------------

A Practical Approach to Removing Gas Well Liquids

This paper reviews various methods used in the past for removing liquids from gas wells, discusses some of the latest approaches and results obtained with them, and presents a practical way of evaluating gas wells as candidates for liquid removal. Introduction In the past few years the burden of fulfilling a larger and larger proportion of our energy requirements has been given to natural gas. At the same time, as a result of depletion, many wells are declining to low deliverabilities. The combination of these two factors has turned attention as never before to means of increasing gas well deliverabilities. One of the numerous factors that can decrease the deliverability of a gas well is the accumulation of liquids in the wellbore. Liquid accumulation and associated decreased deliverability can occur in wells that have never made large quantities of liquids. This paper will discuss various means of removing liquids and of recognizing and evaluating liquid-removal candidates. History of Gas Well Liquid Removal The history of efforts to remove liquid from gas wells can be illustrated by tracing the various devices used in the Hugoton field in Kansas. These gas wells, averaging approximately 2,500 ft in depth, were completed with 5 1/2- or 7-in. production casing. Initially, rates were adequate to develop the velocities needed to carry liquids to the surface, but as bottom-hole pressures declined and, in some cases. as more water pressures declined and, in some cases. as more water was being produced, it became necessary to blow the wells periodically at atmospheric pressure to unload the water. When it became impossible to unload the wells by blowing them, 1 1/4-in. siphon strings were run. The normal procedure was for the pumper to unload the well from time to time by opening the siphon strings to atmospheric pressure. Sometimes small holes were drilled in the siphon strings to aid in lifting the water; these "weep holes" enabled gas to enter the tubing at intervals uphole, providing additional lift toward the surface. The installation of time-clock intermitters to open the siphon string automatically at predetermined time intervals was the next step in the history of liquid removal. The equipment consisted of a clock and a motor valve installed on the tubing at the surface. Weep holes were also used in these installations. This method was less time-consuming and more efficient than manually blowing the well. However, the optimum interval between blows and the length of each blow had to be arrived at by trial and error. Also, the method left much to be desired in that the gas was not used efficiently and maintaining liquid levels below the producing intervals was difficult. The next step was the differential-pressure intermitter. This more sophisticated device measures the difference between tubing (siphon string) and casing pressure, determines the amount of water in the pressure, determines the amount of water in the siphon string, and blows the well when an adequate load of water is detected. After liquid is unloaded, the siphon string, is shut in (gas is being produced up the tubing-casing, annulus). Then gas is slowly bled from the siphon string to lower the pressure and cause the water in the wellbore to move into the tubing. The gas is bled by notching the seat of the motor valve mounted on top of the tubing. JPT P. 916

Depths to Which Frozen Gas Fields May Be Expected - Footnotes

Four items related to my article, "Depths to Which Frozen Gas Fields (Gas Hydrates) May Be Expected," (April, 1971, JPT, Pages 419-423) are worthy of further discussion. First, gases in shallow horizons in the permafrost country, if present when the earth cooled, might well have transformed into hydrates before the reservoir reached 32 degrees F, and so could now be partially or wholly in hydrate form within the present permafrost layer. Hydrates in Liquid-Liquid Systems The second note is that gas hydrates can form from gases dissolved in liquids and do not require a gas phase as such. Gaseous constituents from either a phase as such. Gaseous constituents from either a gas phase or a liquid phase dissolve in water, and it is the dissolved gas that forms the solid hydrate. Early work with the methane-propane-water system had four phases in equilibrium, including a hydrocarbon liquid in contact with water. Removal of the gas phase at equilibrium would have left a hydrocarbon liquid, water liquid, and hydrate. Liquid propane at pressures above those reflected by the propane at pressures above those reflected by the three-phase vapor pressure curves forms hydrate. So one would expect that gaseous constituents dissolved in crude oil would dissolve also in connate water, and that at the appropriate temperature and pressure would solidify as hydrates. Vapor-solid equilibrium constants, y/x8 - Kv8, were devised to predict hydrate points in much the same way that dew point is calculated. The hydrate point corresponds to the temperature and pressure where the following relationship holds: .........................(1) where y is the gas-phase hydrocarbon mol fractions and xs is the hydrate phase (water free) mol fractions. Should one have a liquid phase composition and wish to make a similar prediction, he can use the vapor-liquid equilibrium constant to relate the vapor and hydrocarbon liquid compositions: y = KvLxL. Thus, the point at which hydrate forms from the hydrocarbon liquid phase becomes: .................(2) It would follow that crude oils containing dissolved gas when present in the earth during the cooling process could have that dissolved gas leave the crude process could have that dissolved gas leave the crude oil to form hydrates. Then the vapor-liquid bubble point of the crude oil would be lowered, and Eq. 2 point of the crude oil would be lowered, and Eq. 2 would be satisfiedScauzillo, in measuring hydrate formation conditions with crude oil-natural gas systems, derived results that do not appear to coincide with this analysis. Hydrates in Ocean Sediments Recently it was discovered that methane hydrates are present in the sediments at the bottom of the oceans. present in the sediments at the bottom of the oceans. Because pressure increases with depth in the ocean at some 44 lb per 100 ft of depth, and because the temperature is in the neighborhood of 43 degrees F at depths of 3,000 ft or more, it is clear that methane is in the pressure-temperature range for hydrate formation. Accordingly, it is not unexpected that any methane, as well as heavier hydrocarbon gases, generated in the ocean sediments should be in hydrate form in such sediments. P. 557

Summary Results of the Lewisburg Fog Clearing Program

Abstract Results of helicopter clearing experiments conducted at the Greenbrier Valley Airport, Lewisburg, W. Va., during the period 7–29 September 1969, are presented and discussed. Thirty-five hover experiments and 18 runway-clearing experiments were performed on 10 separate days with fog layers from 125 to 525 ft in depth. The hover experiments, which were successful in virtually all cases, yielded clearings that varied from 400 to 2800 ft in length. The largest clearings occurred with the shallowest fog during tests conducted within ∼1 hr of the natural dissipation time of the fog. The runway-clearing experiments were successful in clearing the full 6000 ft extent of the runway on two occasions, were partially successful on four occasions, and were unsuccessful on 12 occasions. Six helicopter landings were accomplished through artificially created clearings. Particular, quantitative results of the hover experiments are described. The wake penetration distance of the helicopters ranged from ∼700–1000 f...

Deep-Ocean Exploitation Technology

The paper discusses the latest techniques proposed for mining minerals from the deep ocean. Deep ocean is defined as the sea beyond the continental shelf, particularly areas of the sea floor exceeding 1200 ft in depth. The three principal deep-ocean minerals having economic potential in the immediate future are identified. Four recently proposed advanced deep-ocean mining concepts are presented. Use of the air-lift pump as a viable mining method is discussed and a large-scale air-lift pump experiment conducted in an abandoned mine shaft at Galax, Virginia is described. The principal features of the conversion of a small C1-M-AV1 type cargo ship to a deep-ocean mining prototype vessel, RV Deepsea Miner, is outlined.

Story of Big Wells: ABSTRACT

Big Wells field is a rapidly developing oil field in northeastern Dimmit and southeastern Zavala Counties, Texas, approximately 75 mi southwest of San Antonio. Big Wells is a large and significant stratigraphic trap. Production is from a San Miguel sandstone of the upper Taylor Formation (Upper Cretaceous), a section noted for tight sandstone conditions and small--5-10 well--oil fields in anticlinal structures generally associated with small volcanic extrusives. This trend has been considered high risk for economical fields and therefore ignored by most operators, both large and small. Big Wells has instigated the expected flurry of activity when a dead trend suddenly springs back to life. Ranging from 5,300 to 5,700 ft in depth, with a minimum of 200 ft or possibly 400 ft of oil column, the field was found by Sun Oil in January 1969. Development drilling began in the north part of the field where low-permeability sandstone was encountered casting doubt on the economics involved. Southward of the early drilling, much better sandstone reservoirs were found, resulting in full allowable flowing wells (142 BOPD in March 1971). The sandstone reservoir is very fine grained, with an average porosity of 18-20% and permeability ranging from less than 1 md to 100 md, generally less than 5 md. The San Miguel sandstone in the Big Wells field area is a linear sandstone body interpreted to have been deposited as an offshore bar. Today the field is 12 mi long and 3 mi wide. Nine rigs were operating in the field in March 1971. With 160 wells completed by the end of May 1971, the limits of the field are fairly well defined. Drilled on 80-acre spacing, approximately 200-250 wells are anticipated. Production in March 1971 was between 15,000-16,000 b/d of oil. End_of_Article - Last_Page 1696------------

Bedrock Weathering and Residual Soil Formation in Central Virginia

The diversity and complexity of the geology in central Virginia are accompanied by an equally diverse and complex mantle of residual soils which characteristically show strong profile development. It was suspected that these soils would also show significant genetic relationships to the underlying bedrock. In order to substantiate this hypothesis three distinctly different profiles were chosen for textural, mineralogical, and geochemical investigations. The soils, in pedological terms, are from: (1) the Frederick series developed over the Chepultepec limestone; (2) the Iredell series developed over an unnamed hornblende metagabbro; and (3) the Lloyd series developed over the Robertson River granitic gneiss. These residual soils, developed in a temperate nonglaciated area, are quite old in a time sense, and normally show classical A, B, C, and D profile development. The studies reported here indicate that where factors, such as climate, slope, and organisms are not radically different, the bedrock plays a very important role in determining the characteristic properties of the overlying soil profile. Texturally, the limestone-derived Frederick profile is the most uniform and is very fine grained, containing approximately 40 percent clay-sized materials. The Iredell profile is relatively shallow at less than 6 ft in depth, but displays a well-developed eluvial or A horizon and a very fine, clay-rich illuvial or B horizon overlying a sandy gabbroic saprolite. The Lloyd soil, like the Iredell, exhibits a significant grain size variation down the profile, but surprisingly has no A horizon. This absence of an A horizon is attributed to improper farming methods existing over much of the Virginia Piedmont during past decades. The clay fraction of each soil contains significant amounts of quartz as well as several species of clay minerals. Both the Frederick and the Lloyd series are characterized by a single major clay species, but the Iredell mineralogy shows significant vertical changes. Illite is the major clay mineral in the Frederick series; kaolinite, in the Lloyd series; and vermiculite, illite, and montmorillonite characterized different genetic layers of the Iredell series. Variations in major element geochemistry are also reflected in the various horizons. Somewhat surprising were the relative mobilities of iron (high) and magnesium (low) in the C horizon of the Iredell soil. Weathering Potential Index values also reflect (a) the homogeneous nature of the Frederick soil, and (b) the progressive increase in weathering and soil stability up the Iredell and Lloyd profiles. The W.P.I, values for the Iredell soil show that the saprolite developed in the C horizon is chemically similar to the unaltered bedrock. The W.P.I, values of the Lloyd soil indicate a high level of maturity and stability approaching laterite in character. It is concluded that significant genetic relationships do exist between the residual soils and underlying bedrock in each of the three cases studied, and these relationships exist in a rational and predictable manner.

Possible Future Petroleum Provinces of Gulf Coast--Upper Miocene-Pliocene: ABSTRACT

During the Miocene and continuing through the Pliocene, great volumes of sediment were delivered rapidly to an eastward-shifting depocenter in southernmost Louisiana. Sediments were introduced to the basin by rivers and were distributed farther by marine currents gulfward and laterally across persistently broad shelf areas; the amount and grain size of the End_Page 1790------------------------------ sediments decreased with distance from the deltas. At any depositional moment, three gradational facies (sand, sand-shale, and shale) were being developed in bands mainly parallel with the shoreline. This depositional pattern persisted through the late Miocene and Pliocene so that in the total geometry of this net-regressive sedimentary wedge, the facies may be grossly viewed as having developed a sand, a sand-shale, and a shale magnafacies. The sand magnafacies has been productive. However, the majority of hydrocarbons have been found in the inner- and middle-neritic zones of the sand-shale magnafacies in structural traps formed by salt diapirs and growth faulting. The gulfward limits of their exploitation can be determined reasonably from present data and should be confined largely to water depths up to 600 ft. Any significant discoveries are likely to be in the offshore. Louisiana is approaching maturity in its development of these facies but there is room for limited extension. Offshore Texas is largely unexplored but results of drilling through 1969 appear to have been disappointing. The volumes of sediments in the sand and sand-shale magnafacies remaining to be exploited are estimated as follows: Table A possible future source exists in the shale magnafacies, where turbidite sands can reasonably be expected on the updip flanks of salt structures and in the lows between them. The search for reservoirs of this type, particularly in the younger sections, will involve operations beyond the edge of the continental shelf in water exceeding 600 ft in depth. Exploration in the older sections can be accomplished in shallower waters, but will require increasingly deeper drilling. Turbidite exploration demands a considerable sophistication of seismic techniques and the best efforts of geologists, paleontologists, and geophysicists. No reasonable estimate of favorable sediment volume in the shale magnafacies can be made at this time. Present economics barely have justified the oil industry's endeavor in the prime sand and sand-shale magnafacies in water less than 600 ft deep. The same economics hardly can be expected to support operations beyond the edge of the continental shelf, particularly in the face of deteriorating or conjectural objectives. Increased incentives are necessary to encourage the costly risk-taking that will be required to find and develop any future trends in the upper Miocene and Pliocene shale magnafacies. Instead, it appears that current political attacks on existing incentives will be successful to some degree, and incentives will be lessened. Without substantial compensating factors, economic considerations may jeopardize all future explorations in the Gulf. End_of_Article - Last_Page 1791------------

Subsurface Temperatures in South Louisiana: ABSTRACT

Subsurface-temperature observations, made by gas-producing companies in south Louisiana during the course of bottom-hole pressure determinations, were compiled on a magnetic tape by the Federal Power Commission. The measurements were taken long after the wells were completed, and they are therefore more nearly true than those taken during electric-logging operations. Reliable temperature versus depth plots could be made for 132 gas fields. The temperature End_Page 724------------------------------ gradients range from 1 to 2°F and most are between 1.2 and 1.3°F per 100 ft of depth. At a depth of 10,000 ft the temperature ranges between 190 and 230°F. The most prominent features of the temperature distribution at 10,000 ft is a of high temperature about 30 mi wide close to the present coastline. The location of this hot belt is puzzling because it is located approximately where the greatest thickness of Cenozoic sediments is believed to occur. Extrapolating the temperature and pressure downward, it seems possible that conditions necessary for regional metamorphism are present in the lower part of the sedimentary column at depths below 40,000 ft. Possibly the recrystallization of the sediments accounts for the high temperature values. End_of_Article - Last_Page 725------------

Geology and Development of Lusk Strawn Field, Eddy and Lea Counties, New Mexico

The Lusk Strawn field straddles the Lea and Eddy county line, approximately 30 mi northeast of Carlsbad, New Mexico. It is a northwest-southeast-trending anticline with more than 650 ft of structural relief. The productive unit is primarily a biostrome at approximately 11,300 ft in depth. This biostrome is in the Middle Pennsylvanian Strawn Group. Bioherms grew on the west and north flanks of the feature. Porosity of the pay unit is intercrystalline and vuggy. The pay unit is extremely fractured, and these fractures have been important in the creation of porosity and permeability. To August 1, 1966, the field had produced 12,449,426 bbl of oil and 31,585,786 Mcf of gas from 61 wells draining approximately 10,400 surface acres. Because Lusk was developed on 160-acre spacin , allowables are high and payout is rapid. The discovery of this major field has stimulated deep drilling in the province in search of more Lusk-type production.

Comparative Energy Requirements of Oilfield Pumping Units--Conventional vs Front-Mounted

Abstract Conventional front-mounted, rotary crank-balanced pumping units were compared with front-mounted pumps to determine the comparative electric energy requirements. The wells studied were divided into groups of identical make, API ratings, strokes per minute and stroke length. Monthly production and power consumption were averaged for a six-month period and kilowatt- hours per barrel of fluid per 1,000 ft of depth were calculated and plotted against fluid production per day. The front-mounted units consumed an average of 36.8 per cent less electric power than did the conventional units when the strokes per minute were scaled evenly. Design modifications of the front-mounted units are discussed and dynagraph cards are used to illustrate the work loads. Introduction A number of major oil companies have made comparative field tests of the front-mounted, rotary crank- balanced pumping unit (Fig. 1) and various conventional beam-type pumping units (Fig. 2). These tests were generally made using one type of unit on a given well for several days then replacing it with the other type unit for the same length of time. The daily production, electric energy used and inch-pounds of torque required were all noted during these exacting tests. Obviously a study of this type requires more time and money than are generally available to most companies. Another method of comparing the conventional beam- type pumping unit with the front-mounted, rotary crank- balanced pumping unit, based on electric energy consumed per barrel of fluid pumped, is discussed in this paper. The wells under study were divided into groups of identical make, API ratings, strokes per minute and stroke length: conventional 160D units operating at 16.5 X 64 in. strokes/min; conventional 160D units operating at 16.3 X 64 in. strokes/min; and front- mounted 114D units operating at 16.7 X 64 in. strokes/ min. JPT P. 26ˆ

Cementing Geothermal Steam Wells

Cementing Geothermal Steam Wells

Preliminary Observations on the Vertical Distribution of Pacific Salmon (Genus Oncorhynchus) in the Gulf of Alaska

The vertical distribution of Pacific salmon in the high-seas areas of the Gulf of Alaska was investigated from mid May through July in 1959 and 1960 by fishing with gillnets (constructed from 41/2–inch nylon web and measuring 40 ft in depth and initially 400 fathoms in length) at five depth intervals from the surface with the deepest between 160 and 200 ft.Sockeye salmon exhibited diurnal and seasonal differences in their vertical distribution while chum salmon showed diurnal differences. The downward movement of sockeye salmon appeared limited by the thermocline, especially during late June and July. This relationship was observed for chum salmon during hours of darkness only in late June and July. Other factors must also influence seasonal and diurnal vertical movements of sockeye and chum salmon. Within the conditions of the experiment, no consistent differences in the vertical migrations between fish of different age were apparent. Catches showed pink and coho salmon were nearer the surface than either sockeye or chum salmon.

Effects of an Absorbing Bottom on Shallow-Water Normal-Mode Propagation

Recordings have been made of the arrival of sound produced by explosives in shallow water of from 100–160 ft in depth and at ranges up to 80 kyd. Vibrational analysis of these recordings clearly indicates that the sound travels as normal modes. The dispersion of the first 3 modes can be determined in most cases and 5 modes appear in several records. This paper presents some of these experimental mode-dispersion curves and outlines a theory that explains the experimental results. The theory utilizes the ray approach to the normal-mode problem, with the effects of an absorbing bottom introduced into the theory as a consequence of the phase shift of the ray on bottom reflection. Since the recorded sound can be resolved into normal modes, the energy that arrives at a certain time with a particular frequency can be identified as the arrival of a ray with a definite angle. With this method of identification, the reflection coefficient of the bottom can be determined as a function of frequency and angle for small grazing angles and low frequencies.

Cementing Compositions for Thermal Recovery Wells

Abstract This paper presents the results of firing a number of different cementing compositions to the high temperatures which are expected to be encountered in thermal recovery wells. These compositions can be handled by ordinary cementing equipment and have sufficient thickening time to permit placement in wells to at least 6,000 ft in depth. Tests were conducted at temperatures of 700, 1,000 and 1,500F for periods of one, three and seven days, and at 2,000F for one day in dry heat at atmospheric pressure. Physical appearance, weight loss, shrinkage, change of permeability and compressive strength were the properties recorded or calculated. These tests showed that a cementing compositioncan be designed for the most severe temperature conditions expected in the thermal recovery process. These compositions will set hydraulically at low temperatures in one to two days and will retain most of their original physical properties after being heated to these extreme temperatures. Introduction Neither the concept of using heat in the wellbore to stimulate oil production nor its actual use is new. Even the idea of using heat for this purpose in the producing formation itself was put forth in 1917, but the first recorded engineered use of thermal recovery (in situ combustion) in the United States was not until 1952. Since that time more than two dozen such projects have been undertaken to recover oil by this process. According to one major oil company, thermal recovery has been proved as an excellent secondary recovery method. Another states, "a high percentage of oil in a short time gives an attractive economic payout". A three-year experiment at South Belridge field, Kern County, Calif., shows that approximately 50 per cent of oil in place had been produced in 18 months, and 80 per cent of original oil was reported to have been recovered in tests in Illinois. The potential use of this method of recovery and the optimistic outlook of the participants point toward its increasing use as a method of secondary recovery, especially since the cost of exploration and production of oil increases year after year. Many of the papers and articles published to date on thermal recovery processes have dealt with the mechanics, engineering, economics and feasibility of the process, and very little has been mentioned about the problems of cementing the casing, either in the injection or producing wells. Most wells have been completed open-hole with the casing set at the top of the zone to be fired. Engineering personnel of some of the oil companies engaged in thermal recovery projects suggest that it would be better if the pipe could be cemented through the zone with a suitable material and then perforated. Some believe the cementing composition is not a problem, while others believe the type of material used is very important and take all precautions possible. The isolation of zones seems to be a stringent requirement in this process, especially in the injection wells. For these reasons a study of cementing materials was made to provide necessary recommendations for the most suitable compositions to use in wells where extremely high temperatures are encountered. This paper presents the results of tests on different cementing materials under various temperature conditions likely to be found in the thermal recovery processes, with emphasis on the advantages and disadvantages of the various blends tested. Testing Procedures and Materials Evaluated In initiating our laboratory tests for this project we found it difficult to duplicate actual field conditions. Some of the major problems were to ascertain well temperatures, how to duplicate them and what pertinent data to extract from the experiments. The range of temperatures that occur in a well when it is fired is governed somewhat by specific local conditions, the type of igniter used and the length of time the igniter is in use. Temperatures have been reported to range from 320 to 1,400F in field tests where electrical igniters were used, and they would he even higher if a gas igniter were used. Temperatures even higher than those experienced in field tests have been encountered in laboratory model experiments. For these reasons a wide range of temperatures was covered during testing. The average expected temperature probably will be in the range of 600 to 1,200F. The time the cement will be subjected to these temperatures will vary according to how long the igniter is used, how fast it is desired for the front to move away from the borehole and the temperature of the injected air. JPT P. 139^

Seeding of Clouds in Tropical Climates

Warm-cloud seeding with spray or hygroscopic particles often dissipates small clouds but often initiates or increases rainfall from clouds that exceed 4000 ft in depth; seeding with dry ice or silver iodide in supercooled clouds; results of warm-cloud seedings in tropical clouds; new model of convective cloud fields to determine approach of individual clouds to rainstage; effects of warm and of supercooled cloud seeding on this model.

Signal Amplitude and Phase Fluctuations Induced by Surface Waves in Ducted Sound Propagation

The effect of surface waves on sound propagated from a continuous wave source over a range of 300 ft in water 10 ft in depth has been examined. It is found that the surface waves induce regular amplitude and phase fluctuations in the received signal. The dependence of the amount of amplitude and phase fluctuation on crest to trough height of the surface waves has been obtained for acoustic frequencies in the range 1 to 10 kc. Frequency spectra of the fluctuations, for values of the ratio of sound wavelength (λ) to wave height (A) above 18, are the same as the surface wave spectra. For values of λ/A less than 18, the fluctuation spectra are broader and show well-defined second and sometimes third harmonic components. Wave packet experiments in which the bow wave of a small boat is propagated across the length of the otherwise calm duct surface show that in the case of the uniformly rough surface the fluctuations are produced only by surface waves near the source and near the receiver.