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By Dong-Hyeun Koh, Yun-Soo Lee, Min-Seok Kim, Hyoung-Wook Kim

High strength AA7068 (Al - 7.88 wt.% Zn - 2.68 wt.% Mg - 2.07 wt.% Cu) aluminum alloy strip was successfully fabricated by horizontal-type twin roll casting. A simulation technique was used to obtain the range of casting conditions for fabricating strip without defects. The cast strip with thickness of about 5 mm was hot rolled, intermediate annealed, cold rolled to final thickness and subsequently annealed at various temperatures. Tensile properties of annealed and the aged specimens were evaluated at ambient temperature. Tensile strength and elongation of the annealed sheet are about 365 MPa and 28%, respectively. Also, the tensile and yield strength after the aging at paint baking condition (180 °C x 0.5 h) are 586 MPa and 551 MPa, respectively. Therefore, it is expected to show good formability prior to press or stamping and also provide high dent resistance after paint baking treatment.

Jan 1, 2015

By L. Tejeda, J. R. Donald, R. Parra, J. Duran, P. H. Lauzon

"Crucible slag tests were employed to evaluate different refractory brick classes for the Cerro Matoso electric furnace. Comprehensive analysis was conducted to evaluate the crucible erosion and characterize any slag/refractory reaction products.The classes of refractories investigated were:•,tar-impregnated magnesia;•,rebonded fused grain magnesia-chrome;•,direct bonded magnesia-chrome;•,alumina-chrome;•,picrochromite; and•,magnesia-alumina (spinel).It was concluded that tar-impregnated MgO bricks were the most suitable for the slag chemistry and furnace environment according to corrosion and infiltration resistance. A picrochromite (MgCr2O4) brick performed exceptionally well with regards to erosion resistance, however, the slag infiltrated extensively through the brick pores. Alumina-chrome, direct bonded magnesia-chromite, and spinel (magnesia-alumina) bricks were evaluated as not suitable for use in the furnace."

Jan 1, 1999

By E. Faria

"The Santa Rita mine is located in north eastern part of Bahia in Brazil and is owned and operated by Mirabela Mineração do Brasil Ltda. Typical SABC circuit was designed as the preferred option for the 4.0 mtpa (500tph) to produce a P80 of 125um for flotation. Although the SAG was originally designed to operate with conventional radial pulp lifters, later it was fitted with Outotec’s Turbo Pulp Lifters – TPL (Latchireddi, 2005). The milling circuit commenced commissioning on the 24th of October 2009 and the milling circuit achieved the nameplate capacity within days. with small and relatively simple measures to rectify. Since commissioning, the SAG mill has been working in fully autogenous grinding (FAG) mode with no balls (in contrast to the estimated 10% ball charge) and has been consistently treated up to 650tph.This paper examines the comminution design process, the operating philosophies, start-up experiences, post commissioning optimization and future development works. An evaluation of mill performance relative to the design criteria for the project life to date is also included."

Jan 1, 2012

By B. N. Nandi

This paper is a study of the application of the science of coal petrology to the use of coal in the iron and steel industry. The petrography of coal is given the most attention, with some mention of coal palynology. The history of the petrographical analysis of coal is first out-lined, with a description of the various coal entities, and then the apparatus and experimental techniques employed for coal evaluation are discussed. The coke stability factor and the relation of coke strength to petrographical data are also covered, and some space is given to the new science of coke microscopy, in particular its use in following the oxidation of coals.

Jan 1, 1966

By V. S. Sastri, G. R. Doey, R. W. Revie

"Different forms of corrosion, the various corrosive environments encountered, the mining equipment subject to corrosion and the methods to control corrosion in the mining industry are briefly reviewed along with the savings that could be achieved by corrosion control. IntroductionCorrosive conditions in mines and metallurgical plants, lead to deterioration and wastage of equipment and of materials. The cost of corrosion in the mining industry can be significant, and measures to minimize corrosion must be taken to reduce this cost(l-3). Although the data in Table I are twenty years old they indicate the significance of corrosion costs in four industrialized countries. The costs of corrosion in the U.S. metallic ores sector and in the Canadian mining industry are presented in Tables 2 and 3, respectively. Significant savings in the mining industry can be achieved by using corrosion control methods. For example, corrosion in the Canadian mining industry in 1991 cost $1460 million of which $97 million was avoidable. Indirect costs of corrosion associated with plant shutdown, lowered efficiency of equipment and overdesign are additional to the direct costs cited here."

Jan 1, 1994

By Kosei Ishida

To achieve renovation work without noise, the authors developed techniques of manufacturing pre-cut interior finishing components for renovation work. In this paper, to achieve the system of pre-cut interior finishing components, the authors describe a measuring method of reinforced-concrete structure by 3D laser scanner and then describe a method of making a design of pre-cut interior finishing components with the polygon model. Using these two methods, the steps of manufacturing pre-cut interior finishing components consist of the following four steps: First, measure the building shape using a 3D laser scanner. Secondly, integrate a point cloud data and retrieve the markings on the floor. Then, create a polygon model of the building based on the point cloud data. Lastly, make a drywall design using a polygon model. To evaluate the technique feasibility of manufacturing pre-cut interior finishing components, the authors have conducted an experiment of the finishing interior work of the drywall. Using pre-cut interior finishing components, the authors have been able to achieve interior finishing work without noise.

Aug 1, 2013

By John Shirokoff, Ladan Khaksar

"Cyclic polarization technique and also potentiodynamic measurements were applied to study corrosion behavior of 13% chromium steels in chloride containing environment. Potentiodynamic measurements were performed at 25 and 75 °C with 0, 10 and 20 g/l NaCl in 0.01 M hydrochloric acid solution. At the same time, the significant pitting parameters such as corrosion potential (Ecorr), pitting potential (Epit), protection potential (Epro) and passive current (Ipass) of cyclic polarization curves with various NaCl concentration were analyzed and compared to describe the corrosion behavior of 13% chromium stainless steel. Surface measurement techniques such as SEM and EDS were used for morphology and analysis of corrosion products. The results showed that both temperature and Cl- concentration had significant effects on corrosion behavior of 13% chromium stainless steel in acidic solution.INTRODUCTION Of all the corrosion resistant alloys (CRA) used in oil and gas developments, martensitic stainless steels (MSS) are some of the most common ones these days. These steels not only have the advantages of normal steels: high strength, cost-effective, easy to manufacture, available in a wide variety of product forms, but they also have good CO2 corrosion resistance at higher temperatures as a result of their 11% minimum chromium content. One of the most common types of MSS used in the oil and gas industry is 13% chromium steel. NACE and API standards both reference several different varieties of 13% chromium steels for use in oil and gas projects(“Corrosion Resistant High Cr Steel for Oil and Gas Wells,” 2013). All types of 13% chromium steels have about 12 to 14% chromium and other minor alloying additions, and can be placed into two general groups: conventional and modified. Conventional 13% Cr steels (13Cr) are those most common in oil and gas, some of which are CA6NM (UNS J91150), AISI 410(UNS S41000), and AISI 420 (UNS S42000). These alloys have excellent corrosion resistance when compared to carbon steels up to about 300°F (150°C) and are used for a variety of wellhead, tubular, and downhole components however they have very limited resistance to cracking in H2S (Vallourec Group, 2015). Modified 13% Cr (M13Cr) steels came from the need for increased corrosion resistance at higher temperatures, increased H2S cracking resistance, and increased yield strength above 85 ksi (586 Mpa) primarily for tubular goods and other downhole equipment. These features were developed by taking a conventional 13Cr steel and adding nickel (Ni), molybdenum (Mo), copper (Cu), and other alloying elements. M13Cr provides better corrosion resistance than 13Cr up to about 350°F (177°C), yield strengths up to 110 ksi (758 Mpa), and also improved H2S cracking resistance(“Corrosion Resistant High Cr Steel for Oil and Gas Wells,” 2013)."

Jan 1, 2017

By A. R. Sheik, A. A. Baba, M. K. Ghosh, K. Sanjay, R. B. Bale, A. G. F. Alabi, F. A. Adekola, L. Ibrahim

"This paper studies the characterization and dissolution of a Nigerian pyrolusite ore, reporting the results of ore physicochemical analyses and detailed ore characterization before and after leaching at optimal conditions. Ore dissolution rate increased proportional to acid concentration and temperature, but decreased with ore particle size. In a 4 M H2SO4 solution at 80°C with a particle size of –90+75 µm and moderate agitation, ore dissolution rate reached 78.7%. Unleached residue produced under optimal leaching conditions consisted of silica with admixtures of cristobalite and stishovite. The calculated activation energy supported the proposed diffusion control mechanism for the process.RÉSUMÉ Le présent article étudie la caractérisation et la dissolution d’un minerai de pyrolusite du Nigeria, il donne les résultats des analyses physicochimiques du minerai et de la caractérisation détaillée du minerai avant et après la lixiviation sous des conditions optimales. Le taux de dissolution du minerai augmentait proportionnellement à la concentration de l’acide mais décroissait avec la taille des particules. Dans une solution 4 M H2SO4 à 80 °C, avec une granulométrie de –90+75 µm et une agitation modérée, le taux de dissolution du minerai a atteint 78,7 %. Les résidus produits sous des conditions optimales de lixiviation étaient constitués de silice avec un mélange de cristobalite et de stishovite. L’énergie calculée d’activation supportait le mécanisme de contrôle de la diffusion proposé pour le procédé."

Jan 1, 2016

By H. Somekawa

The fracture toughness and deformation structures an AZ31 magnesium alloy processed by equal-channel-angular extrusion (ECAE) were investigated. The average grain sizes of as-ECAE and annealed-ECAE alloys were 4.0 and 16.3 µm, respectively. The plane-strain fracture toughness, Kip, in as-ECAE and annealed-ECAE were estimated to be 27.3 and 23.5 MPam1/2, respectively, by stretched zone analysis. The fracture toughness indicated higher value with grain refinement. From optical microstructural observations in samples after fracture toughness tests, although deformation twins were observed in annealed-ECAE, no deformation twins were observed in as-ECAE. From TEM observations, the dislocations on basal and non-basal planes were activated in as-ECAE. With grain refinement, the activations of dislocations on both basal and non-basal planes were possibly related to the reduction in formation of deformation twins in as-ECAE. In addition, in comparison with direct extruded process, ECAE process was more effective method to improve the fracture toughness in magnesium alloys.

Jan 1, 2006

By K. D. A. Whaley

The Captain North Extension deposit consists of five sulfide lenses hosted in cherty and chloritic metasediment that is bounded by quartz-eye rhyolite and laminated rhyolite. Lens 2 consists of sphalerite and galena with silver-rich tetrahedrite in chert. Lens 3 contains massive pyrite, with chalcopyrite and minor gold, gradational to minor pyrite in a chloritic metasediment. The other lenses are unexplored. The sulfides occur as beds, fracture infills, and disseminated grains. Reserves are estimated at 207 555 tonnes grading 7.380/0 Zn, 2.76% Pb, and 91.81 g/t Ag. The deposit is isoclinally folded, dips steeply west, plunges 50 degrees south, and is faulted out to the north, where drag folding has reversed the plunge. Minor cross-faults contain talc and sericite. High sphalerite but low pyrite abundances result in poor responses to standard electromagnetic techniques. Lens 3, which contains more pyrite than Lens 2, responds better to induced polarization and allows detection. Geochemical anomalies are found in a nearby swamp and stream, but an impervious till cover inhibits the development of soil anomalies.

Jan 1, 1992

By S. Koppalkar

ABSTRACT: The development and evolution of the gravity recoverable gold (GRG) test procedure at McGill University is reviewed in this paper. Since the late 1980s, the research group led by the late Professor André Robert Laplante at McGill University has undertaken fundamental studies and applied research of the Knelson concentrator to develop a sustainable method of estimating GRG. Historically, a concept of “free gold” was used, and it was de?ned as the gold that could be separated and recovered from gold ore by amalgamation. Due to health and safety hazards, the practical use of amalgamation has declined. Around 1994, a methodology using a 3-in Knelson concentrator to measure gravity recoverable gold was established at McGill University. As a result of more than 10 years of improvement and optimization, this technique has become a standard method of evaluating GRG for gold ores, gold plant streams and platinum group metals. By 2006, about 200 GRG tests were carried out at McGill University on ores from all over the world. Recently, a modi?ed version of the GRG test (a simpli?ed test) was developed to provide a quick and rough estimate of the GRG in a sample; this simpli?ed test has the advantage of reduced mass, processing time and cost. To recognize and honour the contributions made by the late Professor Laplante towards the establishment of a standard test procedure for assessing gravity recovery potential, the authors propose that the GRG test be named after Laplante.

Jan 1, 2010

By I. Paredes, R. Díaz, H. Henao

Smelting of copper concentrate generates a significant amount of dusts which are collected in electrostatic precipitators. This material, which is a complex oxide of Cu, Fe, S, As, Sb, Bi and others, is difficult to recirculate into the smelting process due to the reported high concentration of arsenic. However, the dust also has concentration of copper above 10wt %, aside from reported contents of silver corresponding as much as 25wt% of the total inventories of this element in the smelters. Thus, it is of economic and environmental interest the development of a process able to reduce the concentration of arsenic in the dust and produce a material suitable to be recirculated into the smelting process. The present experimental work shows the results of a process of dust sulfidization-oxidition able to remove more than 65wt% of the arsenic present. INTRODUCTION Copper sulfide deposits worldwide exhibit increasing concentrations of arsenic. One case of interest would be the copper ores from the northern zone of Chile, which report high concentrations of enargite (Cu3AsS4) (Revista química, 2015) (Latinominería, 2014). The obtained concentrate from this ore is treated in a Fluidized Bed Roaster, producing calcines with low concentration of arsenic (<0.5 wt% As). This material is suitable to be treated in a Flash Furnace. At the roasting process, the arsenic is volatilized and then precipitated as fine particles of complex oxides. Most of this particulate material is removed from the gas stream through a device called Electrostatic Precipitator (Minería chilena, 2014). The experimental results reported in the literature indicate that arsenic present in these particulate materials (or dusts) cannot be eliminated in oxidizing atmospheres (air) or with inert gases (N2) in a Fluidized Bed Roaster even at temperatures as high as 700°C. There is also information that even the recovery of valuable metals from the dust is difficult through hydrometallurgical processes (private communication). This is how in some foundries these dusts are considered environmental liabilities. Regarding the decomposition of enargite (Cu3AsS4) in neutral atmosphere, it is reported in the literature (Padilla, 2001) that the main chemical reactions are:

Jan 1, 2019

By E. C. Roper

THE Britannia Mining & Smelting Company, Limited, have been operating their property at Britannia Beach, B.C., continuously for nearly forty years and have mined over 33,000,000 tons of ore from orebodies within a belt of highly sheared rocks, five miles long by 2,000 feet wide. The property is in the Coast Range mountains, about twenty miles due north of Vancouver. The mountains rise abruptly from sea level to elevations of 4, 500 feet within a horizontal distance of 7,000 feet. The topography has enabled the orebodies to be developed by adit tunnels. The active mining levels are connected to the adits by incline and vertical service shafts. The main service adits are the 2200, 2700, and 4100 levels (see Figure 1). The mine surface shops, three bunk-houses, and over one hundred dwellings form the townsite camp at the portal of the 2200 level adit. A small camp of one bunk-house and a few dwellings is situated at the 2700 level portal. The beach surface shops and camp, adjacent to the 4100 level adit, service the mill, foundry, and other beach installations as well as the mining from the 4100 level. The ore mined from the various orebodies is delivered to the 4100 main haulage level through a system of rock raises and intermediate tramming levels and is hauled on the 4100 level to the mill.

Jan 1, 1945

By A. Hynes, T. Skulski, D. Francis

The Archean volcano-sedimentary succession in the LG-3 area has undergone two phases of deformation and has been metamorphosed to upper greenschist and amphibolite facies. Marine, fine-grained sediments and mafic pyroclastics comprise the lowest observed stratigraphic unit. These sediments are overlain by a thick sequence of submarine basalts and minor basaltic andesite. The lavas are characterized by high Al/Al+Si, Ti values, low Mg numbers and flat REE profiles (lOx chondrite). A sedimentary prism of coarse elastics which was deposited close to an exposed plutonic highland, overlie the volcanics. Massive lavas of basaltic andesi te and associated volcano-sediments comprise the uppermost stratigraphic unit. These lavas are characterized by high Mg numbers, Ni, Cr, LREE (lOOx chondrite) but low Ti, Al/Al+Si and HRee. The supracrustal rocks were intruded by tonalites and tonalitic gneisses.

Jan 1, 1984

By T. Patching

"COAL MINING at Canmore, Alberta, began in 1886 and continued there until July 1979. A comprehensive review of the Canmore operations is not available, but the following notes have been prepared to accompany references where more complete information about the operations and problems encountered may be found. The coal measures at Canmore occur in the Kootenay formation of Lower Cretaceous age, and at least twelve seams of varying thickness and horizontal extent have been recognized. The coal, of high quality, ranges from semi-anthracite in the lower seams to low-volatile bituminous in the upper seams. The strata of the Canmore area form an asymmetric syncline, the western limb being overturned to vertical by the Palaeozoic strata of the Mount Rundle Range. The eastern limb is more gently sloping, its dip ranging from IO to about 40 degrees. Tectonic movements have created a troubled and complex coal field. The seams were initially not regularly or uniformly deposited, and mountain-building activity folded and faulted the strata and in many places sheared and crushed the original structures of the coal(l,2,3,4,5). The lack of continuity of the seams, and changes in thickness and inclination, made longrange mine planning difficult and necessitated flexible methods of work, and the local disturbances sometimes created problems in roof support and contributed to the occurrence of sudden outbursts of coal and gas. Almost all of the coal was produced from underground operations but a few relatively small V-cut mines were worked along surface outcrops. These have all been filled in and revegetated. The basic method of underground work was by room-and-pillar, but many variations in layout and sequences were employed. Gangways were driven along the strike and pillars were formed by raises or slopes and crosscuts. Pillars were recovered to the extent that ground conditions permitted by splitting or taking 'skips' from the sides of the raises or splits or crosscuts. Because of the variety of conditions that existed in the field a considerable range of cutting, loading and support methods were employed, including hand-loading, slushers and scrapers, duckbills and shaker conveyors, mobile loaders and continuous miners. Except for the coal obtained by continuous miners most of the coal was broken out by blasting when driving narrow working places or by air picks when cutting from a face. In the early years hand loading onto cars or conveyors predominated. A continuous miner was introduced into Canmore in 1959 on a trial basis, and another was subsequently acquired, in order to minimize blasting and hand loading, but problems in operating these machines in inclining seams and difficulties in providing safe roof support for the machines and workers restricted their efficient use. Another major difficulty with the use of continuous miners was the problem of ventilating development headings in the very gassy conditions. In the early 1970s they were replaced by electric and compressed air slushers and scrapers, resulting in a general increase in productivity, roof control, safety, and flexibility of operations(1.6,7,8.9)."

Jan 1, 1985

By J. Koponen, K. S. Stadler, A. Fuerst, S. Gaulocher, Th. von Hoff, R. Veldsman

"Gearless mill drives (GMDs) are the workhorse in the mineral processing industries, more specifically when it comes to grinding crushed ore and cement (in various production stages) in semiautogenous (SAG) mills and large ball mills. They are renowned for their excellent reliability and robustness, long lifespan, and little need for maintenance, and thus yield a low total cost of ownership (TCO).A GMD represents a major investment for a mineral processing plant, and its availability is pivotal for the grinding process. As a basic rule, shut-down periods are to be minimized, but even much more important is that unscheduled shut-downs be avoided. In this contribution, we will present a portfolio of innovative remote diagnostic that consist of the following three key components:1. Trouble shooting is a form of corrective maintenance and is based on state-of-the art remote access technology, thus enabling highly skilled engineers to access the current sensor readings anytime and from anywhere in order to resolve urgent problems together with the GMD user.2. Periodic maintenance reports are a form of preventive and predictive maintenance and aim at continuous improvement based on long-term historical records and analyses of multiple measured signals. These detailed reports highlight the health and operational status of the GMD and are periodically (e.g. 3 months) submitted to the customer.3. Remote condition monitoring spans across preventive and predictive maintenance and is based on continuous recording and automatic analyses of relevant signals using advanced algorithms. The main issue is how to handle the enormous flood of data in an intelligent manner. The results of these analyses are made available to both the GMD user and supplier in real time in order to increase the availability and reliability of the GMD.In this paper, we consider various parts of the GMD, e.g. the cycloconverter, the ring motor, the auxiliary devices (e.g. cooling and lubrication systems), and also phenomena related to the mill itself (e.g. state and quantity of charge). The signal analysis techniques range from simple threshold-based analyses to complex time and frequency domain analyses. We will illustrate the benefits of the proposed approaches with some selected examples."

Jan 1, 2012

By J. Zhang, T. Oleniuk

It is well-known that Saskatchewan has the world’s richest uranium deposits and advanced processing technologies. Unlike the Saskatchewan deposits, complicated mineralogy is common for other places in the world. Mineralogy dictates the process. Mineral Processing at the Saskatchewan Research Council has been working with the uranium industry worldwide since its inception to develop effective processing technologies to suit the unique mineralogy of each deposit. This paper reviews the research and development of uranium processing technologies in the current major uranium production areas such as Canada, as well as the potential development regions like Argentina and Sweden. Acidic and alkaline leaching processes, as well as by-product recovery technologies are discussed based on mineralogy.

Jan 1, 2020

By K. Harris, J. B. Wahl

Ni-base superalloy cast materials provide an outstanding balance of high temperature strength, fatigue resistance, oxidation resistance and coating performance and can be produced to very tight tolerances in extremely complex configurations, such as axial and centrifugal integral cast turbine wheels. As a result, cast superalloys are used in the most demanding applications of aero and industrial gas turbine engines. Use of these materials is expanding to smaller microturbine, turbojet, turbocharger and missile engine applications due to this unique combination of desirable properties. This paper will present an overview of the application of investment cast Ni-base superalloys and process capability to small turbine and missile engines.

Jan 1, 2010

By E. Poiate, P. A. L. P. Firme, D. Roehl, M. A. Carrion, A. M. Costa

Drilling high-pressure/high-temperature wells in salt rock formations is still a challenge for the energy industry. Creep and solubility is part of the salt rock physical-chemical behaviour, which must be considered in the design of the wells. The stress redistribution caused by drilling, in addition to thermallyactivated processes, triggers creep deformation, leading to borehole closure and the imposition of loads on the casing. The drilling fluid is designed by computer modeling in order to control the creep strain rate to a limit which allows the drilling operations and the casing setting. Depending upon the composition of the drilling fluid, chemical reactions on the salt wall may occur, especially in case of water-based fluids in highly soluble salt rocks. In those cases, cavities by dissolution (washouts) can be generated and the casing column remains uncovered by the cementation and laterally unconfined along the cavity length. This scenario is propitious to the loss of integrity of the casing due to phenomena such as plastic collapse, buckling and non-uniform loading on the casing provoked by the closure of salt formation around it. The casing should remain intact during the wellbore life-time. In this work, a section of a typical well crossing salt formation composed by halite and carnallite is considered. An idealized-cylindrical washout cavity inside a highly soluble salt layer is assumed. The purpose here is to evaluate the effect of the dimensions of the cavity on the integrity of the casing. Several typical diameters and lengths of the cavity are adopted. Numerical analyses are carried out with an in-house finite-element system composed by the pre-processor MTOOL 3D®, the simulator ANVEC 3D® and the post-processor POS 3D®. Salt rocks are modeled as visco-elastic materials. Creep is simulated by the Double Mechanism Creep Law, widely employed in Brazilian salt rock mechanics research. Cement and casing (steel) are modeled as elasto-plastic materials described by the Mohr-Coulomb and the von Mises criteria, respectively. Casing integrity is evaluated with respect to vertical and horizontal displacements. Vertical displacements imposed to the casing can provoke the failure of the column by plastic collapse or by buckling. Besides that, horizontal displacements of salt due to creep closure shall lead to the undesirable contact with the casing. Failure envelopes based on displacements are generated. The results of the simulations have shown that the casing failure by plastic collapse occurs preferentially in short columns, as well as buckling occurs in long and slender columns. The occurrence of both failure modes is more frequent in large-diameter cavities. Additionally, failure caused by contact between salt and casing occurs preferentially in short-diameter cavities.

Jan 1, 2015

By D. T. A. Symons, M. M. Kapnistos

"Gravity profiles were established over five known Middle Silurian pinnacle reef s in Lambton County, southwestern Ontario. The profiles were approximately 3 km long, with stations every 60 m. Four fairly recent technological developments were used which now make the gravity method relatively efficient and inexpensive compared to the techniques available two decades ago. These are: (1) a La Coste-Romberg model G gravimeter to measure the gravitational attraction with a sensitivity of 0.01 mgal; (2) a Sokkisha model B-2 semiautomatic engineers level to measure the station elevations with an accuracy of 0.5 cm; (3) a Huntec FS-3 hammer reflection seismograph to determine the overburden thickness to an accuracy of ± 7%; and (4) a modern microcomputer to process the data sets and mathematically filter the gravity values. Thus, two men can measure and analyze approximately 1 km of profile per day and obtain the residual gravity profile to an accuracy of ± 0. 05 mgal. Positive gravity anomalies of 0.17 to 0.72 mgal were observed along all five profiles that approximately delineate the dimensions of the known pinnacle reefs, which have an average height of 120 m, diameter of 1500 m and depth to top of 575 m. The relative ease of the gravity survey method makes it a cost-effective technique for hydrocarbon exploration in southwestern Ontario. IntroductionPinnacle reefs are important sources of oil and gas. Although the pinnacle reefs in southwestern Ontario are small, they may contain commercial pools of oil and gas because of their proximity to refineries. They are also useful for subsurface storage of gas to meet the winter surge in gas demand.At present, geophysical exploration for new pinnacle reefs is done primarily by relatively expensive seismic methods, which are also limited in southwestern Ontario by prohibitions on blasting. Gravity methods of exploration were attempted more than two decades ago in this region. (Pohly, 1954); however, the level of technology at that time made the method marginal in sensitivity and quite expensive. Several subsequent developments- gravimeters with greater sensitivity and operating ease, ""self-levelling"" levels for elevation control, hammer seismic reflection units for determining overburden thickness and portable microcomputers for efficient data analysis-have significantly improved the precision and cost effectiveness of the gravity method. Five known pinnacle reefs were selected in Lambton County, southwestern Ontario (Fig. 1), to test the effectiveness of integrating these developments to locate and define additional reefs. Isolated reefs were chosen to avoid the problem of the gravity effect s of one reef interfering with those of a neighbouring reef. The surveys were facilitated by choosing reefs with a concession road passing directly over them ."

Jan 1, 1980