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By Horrocks KRS, Smitham JB, Ellison JF

This paper describes the development and installation of equipment for continuously measuring separating density in the dense medium cyclone circuits of the four million tpa Port Kembla B/C plant coal washeries. Monitoring equipment consisting of magnetic coils and differential pressure cells were installed in U-tubes taking the full flow of magnetite from the drain sections of the product drain and rinse screens. The monitoring equipment measures overflow magnetics concentration and overflow density continuously and has operated since 1989. From these measurements and calibration trials, the separating density of operating cyclone modules can be inferred reliably. Variographic analyses of the data show that medium density control to +/- 0.002 RD units and separation density control to +/- 0.007 RD units are achievable. Either method for measuring separation density can be used with approximately the same accuracy, although the overflow density measurement technique suffers from the need to have regular flushing of the Dp cells which complicates the signal analysis. Data from the plant shows that separation density can be controlled by regulating medium density, but the assumption of a constant offset between medium density and separation density is erroneous.

Jan 1, 1993

By D Thornton, B Smith, S Demey

Mine to Mill (MTM) optimisation, a total systems approach to the reduction of energy and cost in mining and mineral processing operations, is well-established technology. However, successful applications of MTM optimisation have been largely confined to gold, copper and lead/zinc semi autogenous grinding (SAG) operations, where the goals of tweaking the blast design to increase fines and hence throughput through the mill have been relatively easy to meet. The application of MTM optimisation in a more demanding environment, like that of a multi-stage crushing and screening aggregate operation, was conceived as part of a Department of Energy (DOE) initiative in 2004, aiming to reduce the energy consumption in the US aggregates industry. Two quarries operated by the Luck Stone Corporation of Richmond, Virginia, were selected for the demonstration sites. Dealing with ore variability and a requirement to maintain a fixed feed size distribution to the tertiary plant, whilst still aiming to increase yields of saleable products, presented some unique challenges. Despite these variables, the implementation of the MTM approach at Luck StoneÆs aggregate plant in Pittsboro, North Carolina, has led to a tangible improvement in productivity, particularly in the primary and secondary plants. The successful outcome was dependent upon several key factors, including reliable blasting and processing models, careful analysis of the rock conditions and plant configuration, understanding and buy-in from the Luck Stone operations staff, excellent collaboration with Virginia Tech staff and students, and long-term monitoring made possible through comprehensive PLC logging. This paper presents a review of the work conducted at the Pittsboro quarry and highlights the key reasons behind the successful implementation of the MTM approach in a complex plant environment.

Jan 1, 2007

By C. W. Hamilton

In the production of crude petroleum for the year 1930 Venezuela again maintained its world rank of second only to the United States. During the latter months of the year Russia forged ahead of Venezuela in daily rate of production, and from the present outlook will probably rank second among the oil-producing countries of the world in 1931. It is now believed Venezuelan production has passed its peak. The producing fields of the Bolivar coastal district, along the east side of Lake Maracaibo, continue to be the principal source of supply. Such fields as Lagunillas, Mene Grande and La Pas were not produced to capacity throughout 1930. During the year, three new fields entered into commercial development: The Rio Tarra field in the District of Colon, State of Zulia; the El Mene de Salto field in the District of Acosta, State of Falcon and the Quiriquire field, District of Piar, State of Monagas. For 1930 the total crude production of Venezuela was approximately 137,424,000 bbl. as compared to 137,739,000 bbl. during 1929, or a decrease of 315,000 bbl. During the past year exports of crude from Venezuela amounted to 137,8.50,000 bbl. as against 130,044,000 bbl. exported during 1929. Crude oil in field storage decreased from 14,138,-000 bbl. at the beginning of 1930 to 9,600,000 bbl. as of Jan. 1, 1931— present crude stocks fill about one half the field tankage available. Drilling operations in the producing fields declined sharply but throughout the year there was maintained a satisfactory potential reserve in the shape of proven territory and closed-in producers. Of the 2555 wells which have been completed in Venezuela, 1571 wells were in production on Jan. 1, 1931. The status of these present producing wells may be classified as follows: flowing 652, pumping 170, gas-air lift 193 and closed-in 556. The ratio of closed-in wells to producing wells declined in 1930, while the number of wells produced by artificial means increased materially. In the Bolivar coastal fields there is now observed a marked decline in gas volume and well-head pressure. Lago Petroleum Corpn. and Venezuela Gulf Oil Co. each have under construction electric plants designed to generate power for pumping wells by electricity. The first units of these plants will be placed in conlmission in the early spring of 1931. Venezuela Oil Concessions, Ltd. has installed a number of stenrn-

Jan 1, 1931

By Wm. B. Price

The work of Leon Guillet concerning the effect of nickel on the structural properties of brass is checked. The best value for the coefficient of equivalence t, that is, the amount of zinc replaced by 1 per cent. of nickel, is shown to be-1.1 per cent. The best hot- and cold-working nickel silvers, varying in nickel content between the limits of 4 and 18 per cent., are tabulated and plotted diagrammatically. Also, some data are given showing a comparison between the physical properties of a hot- and cold-working low copper-nickel silver, and a commercial cold-working nickel silver containing approximately 8 per cent. more copper. THIS investigation of low copper-nickel silvers was undertaken to check the work of Leon Guillet on special brasses and to determine, more accurately, the effect of the addition of nickel on the microstructure of the binary alloys of copper and zinc. It was hoped that the results could be successfully applied to the practical production of low copper-nickel silvers. To explain the results of his investigations on special brasses, Leon Guillet evolved his conception of "fictitious compositions." He states,1 in his general conclusions, that on the introduction of a small amount of a third metal to a copper-zinc alloy, it enters into solid solution with the normal constituents up to saturation, but by so doing it brings the ternary alloy into a state microscopically equivalent to a binary copper-zinc alloy of fictitious composition, and physically more nearly like the latter than the brass containing copper-zinc in the ratio actually present. The physical properties of the ternary alloy, when compared to the same properties of an actual brass of the fictitious composition, are modified by the natural properties of the third element. Beyond the point of saturation, a special constituent appears and the above generalization no longer holds.

Jan 2, 1924

By James P. Hambleton, Sam A. Stanier

A perceived advantage of screw-type foundations is the ability infer aspects of foundation performance from quantities measured or observed during installation, especially the installation torque. A particular concept widely used in practice is to correlate installation torque to ultimate capacity. This notion has proven useful as a field verification technique despite the absence of validated models that relate key variables of interest, such as installation torque, axial (crowd) force, geometrical parameters, and soil strength. This paper considers previous work by the co-authors and collaborators on analytical, numerical, and physical modelling of screw piles to relate the quantities measured or controlled during installation (e.g., installation torque) to the ultimate capacity and soil strength. Attention is given to saturated clay as a particular soil type amenable to simplified analysis. An analytical model for a single-helix pile is considered as a means of directly relating the ultimate capacity and undrained shear strength to the installation torque, crowd force, plate pitch, plate diameter, shaft diameter, installation depth, and surface roughness. The connection between the installation variables and ultimate capacity—and the sensitivity to crowd force in particular, a quantity that is typically not measured during field installations—is also discussed. The theoretical predictions are compared against data obtained from small-scale laboratory experiments that suggest the installation torque relates to the remolded strength of the soil. INTRODUCTION Screw piles are deep foundations that are twisted into the ground through an applied torque. Advantages over driven piles or drilled foundations include the relative silence of the installation, with low ground vibrations, and the possibility of being easily decommissioned by reversing the direction of twisting. Screw piles are now routinely encountered as a flexible, low-cost solution for numerous applications (Figs. 1 and 2), and they are also being considered for applications in offshore energy production due to limitations being imposed with respect to decommissioning and underwater noise. Also known as “screw anchors,” “helical piles”, or “helical anchors,” screw piles consist of helices or helical plate elements attached to a central shaft. Figure 3a shows the components of a single-helix pile and key variables. The diameters of the shaft and helix are denoted by d and D, respectively, and p is the pitch of the helix. Variable H denotes depth of the helical plate, and T and N denote the torque and axial (crowd) force applied during installation. In typical applications, the pile includes multiple helical plates, and the shaft is composed of segments that allow for it to extend to large depths into the soil.

Jan 1, 2019

By J. S. Gardner, J. J. Zaluski

I. INTRODUCTION West Virginia has a long history of coal production.1 The state at one time led the nation in total coal production, while at the same time coal from West Virginia constituted one quarter of total U.S. coal production.2 In more recent years, however, West Virginia’s level of coal production has been reduced in comparison to that of other states due to the high relative cost of producing coal in the state.3 Another blow to the producers of coal in West Virginia is the action known as Bragg v. Robertson.4 In 1998 various individual plaintiffs, as well as a conservation group known as the West Virginia Highlands Conservancy, filed a civil action under a provision of the Surface Mining Control and Reclamation Act of 1977, Pub. L. No. 95-87, §522, 91 Stat. 445 (codified at 30 U.S.C. §§1201-1328) ("SMCRA" or the "Act") that allows declaratory and injunctive relief against state and federal officials for non-compliance with the Act.5 The plaintiffs generally claimed that the Director of the West Virginia Department of Environmental Protection ("WVDEP") had exhibited a pattern of violating mandatory non-discretionary duties under SMCRA and the West Virginia state regulatory program.6 These non-discretionary duties involved many areas of regulation, including water quality standards, disturbance of wetlands, hydrologic reclamation plans, Approximate Original Contour ("AOC") requirements and AOC variances, post-mining land uses, contemporaneous reclamation, and as explained later, the "buffer zone rule."7 In addition to these claims against WVDEP, the plaintiffs also alleged that certain individual members of the Army Corps of Engineers (the "Corps") had failed to carry out statutory duties under the Clean Water Act (the "CWA") and the National Environmental Policy Act ("NEPA").8 Generally, the complaint stated that the Corps did not have statutory authority under the CWA to regulate valley fills created for the purpose of the disposal of waste material, i.e., the overburden associated with mountain top mining.9 Alternatively, the plaintiffs claimed that even if the Corps could regulate valley fills, the Corps violated NEPA by issuing nationwide permits without required analysis. Finally, the plaintiffs asserted that the issuance of a nationwide permit for surface mining valley fills is unlawful.10

Jan 1, 2001

By G. Jalkanen

Parameter estimation of the inverse distance estimation algorithm is presented. The objective function to be minimized is a sum of squared cross validation errors. The unknowns to be estimated are the exponent of the inverse distance estimator and anisotropic angles and ratios that are used in determining the distances in the algorithm. Examples are presented for both two and three dimensions data sets.

Jan 1, 2009

The mining industry has a well deserved reputation earned over the years for innovation, engineering, management and the quick application to mining of emerging technology. The cumulative result is the economic exploitation of lower grade resources. The developments during the last decade have done nothing to tarnish the reputation. There are many that come easily to mind: the use of contractors for both surface and underground operations, a trend toward mine management contracts, the increasing recognition of the economic potential of ground support, and the development of physical measures to achieve it, - sophisticated measures to analyse blasting , and thus improve fragmentation, - instrumentation to assist geotechnical appraisal, - the development and application of the powerful and flexible, excavator, - the evolution of measures to improve grade control, - massive improvements in equipment productivity and reliability built largely around the application of hydraulics, - the development of powerful computer packages for orebody modelling, mine design and extraction, - simple "dense" fill systems, - maintenance management techniques including the greater use of off-site maintenance of exchange components, - the utilisation of communication systems for data transfer.

Jan 1, 1989

IN A broad sense, the subject of slag control includes not only the adjustment of the composition of the slag but also of its relative weight in terms of percentage of the metal-bath weight. The slag is made up essentially of (1) oxides formed by oxidation of silicon, manganese, phosphorus, and iron in the charge, (2) SiO2, MnO, and other oxides charged as such, and (3) lime charged or fed to the heat to neutralize the “acidic”: oxides present (Si02 and P2O5). Obviously, if practically perfect control were possible over the composition of the charge as well as over the oxidation process during the melting period, both slag weight and composition would be very nearly predetermined, and the control problem would be solved. Unfortunately, we have only a somewhat. imperfect control over these factors, so that beginning at about the lime-boil period in the heat, and later in the early refining period, it becomes necessary for the first helper, as the heat progresses, to make quick estimates of the composition and physical state of development of the slag (as well as of the amounts of phosphorus, sulphur, and carbon in the metal) from which he can judge how much extra lime, roll scale, fluorspar, and other additions will be needed not only to give the desired final slag composition, but also to hasten the complete fusion or shaping to a desired viscosity in the liquid state. The discussion in this chapter is limited essentially to those more or less practical rapid methods of slag estimation that have been used, or at least tried, for these purposes under actual open-hearth shop conditions. Another aspect of importance here is the extent to which the freedom of choice to the operator is limited by available charge materials, product specifications, and the oxidation and other chemical- reaction effects which inevitably occur under the conditions of this furnace process. For a better understanding of these control limitations and of the chemical and physical background of the subject, the reader is urged to read at least part of the discussion in Chapters XVII and XIX. Charge materials are discussed in Chapter IV, and many of the details of charging, melting, and refining practice closely related to slag control are given in Chapters VI and VII.

Jan 1, 1944

By L. Nahai

Iran's petroleum industry is nearly 50 years old and the oldest in the Near East. According to published figures, Iran ranks third in production and reserves in the Near East. These reserves (including probable reserves) are estimated at 35 billion barrels and constitute about 11 percent of the world's total. Iran is the sixth largest producer of crude petroleum in the world. The 1961 output of more than 430 million barrels was 5 percent of total world out-put for the year. In the same year, Iran ranked fourth among world petroleum exporters, providing 8.4 percent of total world exports.

Jan 1, 1963

By J. Trojacek

A large-scale development in exploration and production of uranium ores in the Czech Republic was done in the 2nd half of the 20th century. Many uranium deposits were discovered in the territory of the Czech Republic. Over a period of 50 years approximately, 110 000 tons of uranium in concentrate were produced. Different mining methods were developed and used. One of the most considerable deposits in the Czech Republic is the site Hamr na Jezere ? Straz pod Ralskem where both mining methods ? the underground mining and the acidic in-situ leaching ? were used. The extensive production of uranium led to widespread environmental impacts and contamination of groundwaters. Over the period of ?chemical? leaching of uranium (ca. 32 years), a total of more than 4 million tons of sulphuric acid and other chemicals have been injected into the ground. Most of the products (approximately 99.5 %) of the acids reactions with the rocks are located in the Cenomanian aquifer. The contamination of Cenomanian aquifer covers an area larger than 27 km2. The influenced volume of groundwater is more than 380 million m3. The total amount of dissolved SO4 2- is about 3.6 million tons. Approximately 0.5 % of the contamination is located in the Turonian aquifer. After 1990, a large-scale environmental program was established and the Czech government decided to liquidate the ISL Mine and start the remediation in 1996. The remediation consists of contaminated groundwater pumping, removing of the contaminants and discharging or reinjection of treated water. The objectives of the remedial activities are the followings : to restore the aquifer to a condition guaranteeing continuing usability of Turonian water of Northern Bohemia Cretaceous, to decommission boreholes and surface installations and to incorporate the surface of leaching fields into the ecosystems taking into account regional systems of ecological stability and urban plans. Nowadays four main remedial technological installations for reaching of these aims are used - the ?Station for Acid Solutions Liquidation No. One?, the ?Mother liquor reprocessing? station, the ?Neutralization and Decontamination Station NDS 6? and the ?Neutralization and Decontamination Station NDS 10?. Total capacity of this complex is sufficient to reach the target values of remedial parameters in 2037. The remediation action consists of: pumping of residual solution to the surface, separating uranium from the solution and reprocessing contaminants into commercially usable or ecologically storable products. It is expected that the amount of withdrawn contaminants will vary from 80 000 to 120 000 tons per year. Total costs of all remediation activities are expected to be in excess of 1.5 billion EUR.

Aug 1, 2013

By C. A. Hansen

INTRODUCTION It has been the experience of the writer, during some. five years' work with electrolytic zinc, that the zinc cell is perhaps more- sensitive to impurities in the electrolyte than the analytical methods as yet developed for the chemical identification and determination of these impurities; but that, when proper purification methods have been applied to a given solution, the behavior of the cell is quite independent of the original sources from which the zinc sulphate has been derived. It has also appeared that the behavior of the zinc cell is the best and surest check on the correctness and thoroughness of the purification methods used, because it indicates the presence of both current impurities. and cumulative impurities derived from the leaching of the ore; it also in

Jan 3, 1918

By B. McFadzean, K. Moller

"The mechanism whereby thiol collectors adsorb onto a mineral surface has been widely studied. Most of these studies examine the mineral surface at equilibrium state and, often, well above monolayer coverage. However, the formation of species at the mineral surface is a complex process that is both kinetically and thermodynamically controlled. In a typical industrial application, the dosage of collector will be around monolayer level. This study uses isothermal titration microcalorimetry to measure the heat evolved during the reaction of sodium ethyl xanthate (SEX) and sodium isobutyl dithiocarbamate (SIBDTC) and their mixtures with galena and chalcopyrite. The sensitivity of the instrument allows heats of reaction of sub-monolayer quantities of thiol collector to be measured.The study found that both the magnitude and kinetics of the reaction between a collector and a mineral surface was dependent on the type of mineral and the type of collector. Proposals are made for the reactions based on literature and the evidence from this investigation. It was found that when collectors were reacted with mixtures of galena and chalcopyrite, that the magnitude of the reaction was lower compared to that measured for the pure minerals alone. This may be due to galvanic interactions between the minerals, resulting in a passivating effect on one or both of the minerals."

Jan 1, 2014

By Jim Breedlove, Stephen P. Case, Mike Fabio

To meet salt production needs over the remaining life of the Cayuga Mine at Lansing, New York, the Salt Division of Cargill, Inc. decided to build a new underground screening plant. The new plant required a chamber 50 feet wide by 250 feet long and nearly 70 feet high. On advice of their mining contractor, Dynatec Mining Company, the company chose an ingenious excavation method similar to sublevel stoping. This method eliminated the need for an access ramp, reduced equipment needs and excavation time substantially.

Jan 1, 1996

By V. F. Petrov, O. D. Khmelnitskaya, V. M. Lodeischikov

"The processing of copper gold ores is one of the major issues of gold-mining industry in the beginning of 21st century. In this case, application of ammoniacal cyanidation process for this type of mineral raw materials deserves special attention. Irgiredmet Institute has carried out a wide range of studies on ammoniacal cyanidation process and evaluated the possible commercial use of this process for Russian operating plants. Copper gold-bearing ore from a current Russian deposit was studied. The content of gold and copper in the ore is 9.4 g/t and 0.4%, respectively. Based on the results of preliminary test work, a flow sheet was developed. It included gravity concentration followed by cyanidation of the gravity tailings using CIP. The flow sheet provides sufficient total gold recovery (91.5%). However, this technology has disadvantages, such as high specific consumption of reagents: 4.5 kg/t NaCN and 13.5 kg/t Ca(OCl)2 the ore and the increased gold grade in the liquid phase of the tails slurry (0.2 g/t). In order to improve cyanidation process parameters, test work on gravity tails processing using ammoniacal cyanidation was carried out. After the test work was completed, ammoniacal cyanidation flow sheet for copper gold-bearing ores was developed. Leaching conditions were optimized using recycled process solutions. Recommendations on gold recovery from the solutions and tails detoxification are given. The proposed flow sheet provides 91.5% gold recovery. In this case, compared to the conventional option, the consumption of cyanide decreases by 3-4 times.INTRODUCTION The technology of precious metals recovery from gold-bearing ores is based on cyanidation. This accounts for up to 90% gold recovery and the significant portion of silver (Lodeischikov, 1999). However, there exists the category of so called refractory ores. They are not amenable to direct cyanidation (without using additional expensive processes), or they are characterized by low indices of metals recovery and high consumption of reagents. The latter also include copper gold ores. Their deposits can be found extensively both worldwide and in Russian Federation. A feature of these ores is that they contain not only gold but also copper. It is considered not only as a valuable component but also as a harmful mineral impurity that hinders gold cyanidation, gold precipitation from the solutions by cementation onto zinc dust and adsorption onto activated carbon (CIL, CIP-processes), detoxification of cyanide bearing effluents."

Jan 1, 2018

By P. W. Hunter

The construction of a major sewerage scheme requiring 15.3 km of 5.5m excavated diameter tunnel in basalt, mixed and soft ground has been undertaken by the Melbourne and Metropolitan Board of Works. A double shielded Tunnel Boring Machine was selected to excavate 13.7 km of basalt and mixed ground. Advanced methods for recording operational data on the TBM were introduced. Progress to date has shown that the TBM can excavate rock very effectively with a best weekly production of 178.8m; soft ground has been encountered and successfully handled.

Jan 1, 1987

By Wilfred A. Lyons

El departamento geológico de una mina describe ilustraciones de mapas y y secciones transversales del yacimiento, como sus secciones longitudinales. En este sentido, el objetivo del texto señala el uso de las secciones longitudinales contorneadas donde se localizan los valores deseados, para luego unirse mediante isogradas, produciendo un gráfico simi lar al de un plano topográfico. Las principales secciones contorneadas son: las secciones longitudinales contorneadas de valores metalíferos, secciones longitudinales contorneadas de espesores de vetas, secciones longitudinales contorneadas mineralógicas, secciones longitudinales contorneadas de estructura de vetas, secciones longitudinales contorneadas de pares metalíferas, secciones longitudinales contorneadas combinadas, secciones longitudinales contorneadas de contenido metálico, así como se describen las inferencias de las secciones longitudinales contorneadas.

Aug 20, 1965

By Kirk H. P. E. McDaniel, Mark T. Strever, Keith G. Jr. Wallace

This paper presents the design and installation of an underground ventilation remote monitoring and control system at the Waste Isolation Pilot Plant. This facility is designed to demonstrate safe underground disposal of U.S. defense generated transuranic nuclear waste. To improve the operability of the ventilation system, an underground remote monitoring and control system was designed and installed. The system consists of 15 air velocity sensors and 8 differential pressure sensors strategically located throughout the underground facility providing real-time data regarding the status of the ventilation system. In addition, a control system was installed on the main underground air regulators. The regulator control system gives indication of the regulator position and can be controlled either locally or remotely. The sensor output is displayed locally and at a central surface location through the site-wide Central Monitoring System (CMS). The CMS operator can review all sensor data and can remotely operate the main underground regulators. Furthermore, the Virtual Address Extension (VAX) network allows the ventilation engineer to retrieve real-time ventilation data on his personal computer located in his workstation. This paper describes the types of sensors selected, the installation of the instrumentation, and the initial operation of the remote monitoring system.

Jan 1, 1995

By D. R. Conlon, E. R. Brownscombe

Errors in measurement of reservoir pressure include: (I) gauge errors, and (a) interpretation errors. Gauge errors may be reduced by: (a) reading charts with a comparator microscope, (b) use of hard metal stylus points to give clear lines, (6) insuring temperature equilibrium, and (d) making multiple tests. Check calibrations are equally as important as check well tests. A statistical analysis of such check runs shows quantitatively the advantages of a standardized "zero pressure line'' and of the use of field calibrations made at bottom-hole temperature on the same chart run in the well. Interpretation errors include: (a) fluid heads, which should be corrected to the top of the perforations on the basis of well-fluid gravity and from the top of the perforation to the datum level on the basis of reservoir-fluid gravity, and (b) gradients around the well. Conventional shut-in periods may be entirely inadequate to overcome these, necessitating a reservoir study based on build-up curve data, reservoir history, core analysis and any other available information. Interest in engineering studies of the pressure changes in oil and gas reservoirs is increasing. This type of work yields important information and doubtless will be greatly extended in the future. One of the factors limiting the work, however, is the accuracy with which the reservoir pressures can be determined; for if the inaccuracies in the pressure measurements represent an appreciable percentage of the pressure changes, the engineer is seriously handicapped, and must delay the reservoir study until the reservoir pressure has changed a relatively large amount. This delay can greatly reduce the benefits of such studies, at least from the point of view of aiding the leasing, drilling and completion programs. Thus, from the point of view of reservoir analysis, it is frequently important to obtain the most accurate pressure data possible early in the history of any field—particularly for the gas-distillate fields now being developed. This paper deals with improvements in the measurement of bottom-hole pressures that permit pressures even as high as 4000 or 5000 lb. per sq. in. to be determined with gauge errors of only+ ±I to 2 lb. per sq. in. Since pressures out in the reservoir rather than in the bottom of the hole concern the reservoir analyst, differences between bottom-hole pressures and actual reservoir pressures are also considered. In general, errors in pressure measurement may be divided into: 1. Gauge errors: a. Errors due to inaccuracies in reading the pressure charts. b. Errors due to irreproducibility of the pressure element and recording system. c. Errors caused by failure to allow the gauge to reach temperature equilibrium. 2. Internretation errors: a. Errors caused by a fluid head between the gauge position in tubing and the pressure at the datum level in the reservoir. b. Pressure gradients in the reservoir.

Jan 1, 1946

By D. R. Conlon, E. R. Brownscombe

Errors in measurement of reservoir pressure include: (I) gauge errors, and (a) interpretation errors. Gauge errors may be reduced by: (a) reading charts with a comparator microscope, (b) use of hard metal stylus points to give clear lines, (6) insuring temperature equilibrium, and (d) making multiple tests. Check calibrations are equally as important as check well tests. A statistical analysis of such check runs shows quantitatively the advantages of a standardized "zero pressure line'' and of the use of field calibrations made at bottom-hole temperature on the same chart run in the well. Interpretation errors include: (a) fluid heads, which should be corrected to the top of the perforations on the basis of well-fluid gravity and from the top of the perforation to the datum level on the basis of reservoir-fluid gravity, and (b) gradients around the well. Conventional shut-in periods may be entirely inadequate to overcome these, necessitating a reservoir study based on build-up curve data, reservoir history, core analysis and any other available information. Interest in engineering studies of the pressure changes in oil and gas reservoirs is increasing. This type of work yields important information and doubtless will be greatly extended in the future. One of the factors limiting the work, however, is the accuracy with which the reservoir pressures can be determined; for if the inaccuracies in the pressure measurements represent an appreciable percentage of the pressure changes, the engineer is seriously handicapped, and must delay the reservoir study until the reservoir pressure has changed a relatively large amount. This delay can greatly reduce the benefits of such studies, at least from the point of view of aiding the leasing, drilling and completion programs. Thus, from the point of view of reservoir analysis, it is frequently important to obtain the most accurate pressure data possible early in the history of any field—particularly for the gas-distillate fields now being developed. This paper deals with improvements in the measurement of bottom-hole pressures that permit pressures even as high as 4000 or 5000 lb. per sq. in. to be determined with gauge errors of only+ ±I to 2 lb. per sq. in. Since pressures out in the reservoir rather than in the bottom of the hole concern the reservoir analyst, differences between bottom-hole pressures and actual reservoir pressures are also considered. In general, errors in pressure measurement may be divided into: 1. Gauge errors: a. Errors due to inaccuracies in reading the pressure charts. b. Errors due to irreproducibility of the pressure element and recording system. c. Errors caused by failure to allow the gauge to reach temperature equilibrium. 2. Internretation errors: a. Errors caused by a fluid head between the gauge position in tubing and the pressure at the datum level in the reservoir. b. Pressure gradients in the reservoir.

Jan 1, 1946