The effects of bedding plane orientation on the elastic constants and the yield strengths of three laminated rocks (one sandstone and two shales) and one isotropic rock (a limestone) were studied. The directional dependence of the elastic properties of these rocks was experimentally evaluated using a triaxial compression cell and auxiliary stress - strain measuring equipment. Symmetry of Poisson's ratios within the bedding plane suggested that horizontal isotropy exists, but the bedding planes do give rise to an appreciable difference between properties in the horizontal and vertical directions. For the three bedded rocks studied, Young's modulus was lower normal to bedding than along bedding. Yield strengths were determined at confining pressures from 0 to 12,000 psi in a triaxial compression cell. The rocks studied showed strength reductions as high as 40 per cent when the test specimen was oriented at 20 degrees 30 degrees to the bedding planes. The mechanical behavior of these rocks suggested that the rock properties of shear strength and/or coefficient of internal friction can vary with direction, depending on the particular rock tested. Tensile strengths were also measured and found to be lowest when failure occurred along bedding. This work shows that bedded formations exhibit sizable directional variations in both their elastic constants and yield strengths. It is suggested that these variations may be accounted for by using the "elastic laminate" model and the "variable coefficients" failure model. Introduction The nature of rock deformation at elevated pressures has been studied by many workers; papers by Handin, and Robinson illustrate the present state of knowledge. Most investigators have either chosen rocks which were as isotropic as possible (in order to avoid complications of data interpretation and analysis) or they have oriented their samples so that the effects of anisotropies (such as bedding planes) have been avoided. Of the studies performed, few were concerned specifically with mechanical anisotropies. Griggs has presented limited data for specimens cut parallel, normal, and 45 to the bedding plane; he relates the strength anisotropy observed to the fabric (bedding) anisotropy. His tests were primarily concerned with large deformations (20 per cent strain); thus, no directional values of the elastic constants were reported. Handin has reported the results of similar experiments. Bott has discussed rock strength anisotropies due to faults, cleavage, or bedding. He was concerned primarily with determining the shear stress on such planes and did not mention the effect of friction. Jaeger later generalized Bott's work by taking friction into account and presented a limited theory for the failure of rocks having a "single plane of weakness", and also for rocks having a constant coefficient of friction, and a shear strength which varies with bedding plane orientation. Donath and Cohen, and Donath have evaluated rock strengths from shale and slate specimens cut normal and parallel to bedding. A dependence of cohesive strength (ro) on the specimen orientation was also shown. Adler has also studied this problem and lists similar results. He assumes that all bedded rocks behave according to Jaeger's single - plane - of - weakness theory. Kalinin and Belorussov list results for strength tests parallel and perpendicular to bedding and use this information as a basis for hole deviation analysis. From the literature it is apparent that sedimentary rocks have been tested under widely varying conditions of stress; however, the assumption of isotropy is generally, but not always, made. Since geologic sedimentation often deposits sediments in very definite layers, it seems that more systematic attention should be given to the possible effects of this natural bedding. Bedding, as used here, refers to visible regularities of grain size or orientation resulting from depositional processes. SPEJ P. 67ˆ
The primary purpose of this investigation was to define the basic mechanism of the miscible displacement of oil and water from porous media by various water-driven alcohol slugs. The first portion of this investigation deaIt with use of a single alcohol (isopropyl) as the slug material. In later studies two distinct process variations were developed, wherein the total alcohol slug consisted of two or more slugs of different alcohols. The first of these utilized methyl alcohol and isopropyl alcohol, while the second variation used normal butyl alcohol and methyl alcohol as the composite slug. These techniques were shown to have distinct advantages over the simple, onealcohol process and represent an important extension of the original process. The porous medium used in this study was I-in. diameter, 100-ft long, unconsolidated core. The porosity of this system was 35 per cent, and the permeability was approximately 4 darcies. Total pore volume of the core was 5,700 cc. All displacements were conducted at an injection rate of 5 to 6 cc/min, which corresponded to a frontal advance of 5 to 6 ft/hr. Most of the alcohol slug runs were initiated in a previously waterflooded system; however, several were conducted at irreducible water saturation. The oils used were naphtha, SoItrol-C and Kendex 0837, having viscosities of 0.52, 1.5 and 16 cp at 20°C, respectively. Kendex 0837 was used in only one run. Individual displacements were conducted by injecting the desired size and type of alcohol slug, which was then driven or displaced in turn by water. The basic data obtained from each run were the composition-time histories of the effluents. From these data it was possible to study the displacement mechanism and to determine the oil recovery. Data from 30 such runs were obtained. In the first series of runs, isopropyl alcohol (IP A) was used as the alcohol slug. This alcohol is completely miscible with either oil or water; however, miscibility of the three-component system (oil-water- IP A) requires a relatively high concentration of IP A. Hence, the displacement is not of the miscible type unless the IP A content is maintained above some critical value. Slug volumes ranging from 8 to 16 per cent of total core pore volume were used in several runs in both the naphtha and Soltrol-C systems. Complete (100 per cent) naphtha recovery from a previously waterflooded core required a 13.5 per cent IP A slug. Complete SoItrol recovery required a 17 per cent slug under the same conditions.
Published in Petroleum Transactions, AIME, Volume 219, 1960, pages 46–53. Abstract This study defines the basic mechanism of the miscible displacement of oil and water from porous media by various water-driven alcohol slugs. Three distinct alcohol slug processes were studied. Considerable data concerning the quantity of alcohol required for oil recovery were also obtained. All data were obtained in a 1-in. diameter, 100-ft long, unconsolidated core. The porosity of this system was 35 per cent, and the permeability was approximately 4 darcies. Total core pore volume was 5,716 cc. All displacements were conducted at a constant injection rate of 5 to 6 cc/min, which correspond to a frontal advance of 5 to 6 ft/hr. The first portion of this paper is concerned with the use of one alcohol-isopropyl-as the slug material. Isopropyl alcohol (IPA) is completely miscible with both oil and water; however, miscibility of the three-component systems, oil-water-IPA, requires a relatively high concentration of IPA. Hence, the displacement is not of the miscible type unless the IPA concentration is maintained above some critical value. A slug of IPA equal to only 13.5 per cent of the pore volume was found to be sufficient to obtain complete recovery of residual naphtha. In later studies two distinct process variations were developed. The first of these utilized methyl alcohol (MA) and IPA as slug materials. It was shown that methyl alcohol may be substituted for IPA at the front and rear of the slug with no loss of oil recovery. A slug of 4 per cent MA–4 per cent IPA–4 per cent MA was sufficient for complete oil recovery. Because MA is considerably cheaper than IPA, this represents an important step toward economic application. A second process variation used normal butyl alcohol (nBA) and MA as the composite slug, the nBA segment being injected first. This technique requires the smallest total slug size (approximately 10 per cent) of all processes studied. The high cost of nBA, however, precludes commercial application. It is possible that this basic process, subject to changes of alcohol type, may lead to a commercial process.
This paper presents some preliminary results of twodimensional cutting tests of dry limestone samples at atmospheric pressure. Cutting tips having rake angles of + 30°, + 15°, 0°, -15° and -30° were used to make cuts on Leuders limestone samples at six depths of cut ranging from .005 to .060 in. at cutting speeds of 15, 50, 109 and 150 ft/min. The vertical and horizontal force components on the cutting tips were recorded with an oscilloscope equipped with a polaroid camera. Motion pictures of the cutting process at camera speeds of 5,000 to 8,000 frames/sec were taken at strategic points in the variable ranges.The movies provide considerable insight into the brittle failure mechanism in rocks. It appears that chipgenerating cracks usually have an initial orientation which is related to the resultant of the externally applied forces. The latter part of the crack curves upward toward the free surface being cut, this part being governed by some type of cantilever bending or prying. The linear and angular motion of the loosened chips also indicate the tensile nature of brittle failure. Analyses of the forces on the cutting tips indicate that: (1) relatively small increases in vertical loading result in large cut-depth increases for sharp tips (rake angles > 0°); (2) tool forces increase at an increasing rate as t~ rake angle decreases, particularly for rake angles < 0°; and (3), for the range of this study, rate of loading had little effect on the maximum forces. Both the movies and visual inspection of the cuttings indicated that the volume of rock removed by chipping was much larger than that by any grinding mechanism, even for tips having negative rake angles. Cutting size increases with increased cut depth and rake angles, and decreases slightly at high cutting speeds, the depth of cut having by far the most influence. The amount of contact between the rock and the cutting tip was always less than the depth of cut and rarely exceeded 0.010 in. even for cuts of 0.060 in.
Introduction In the past few years the hydraulic aspects of rotary drilling have received considerable attention. It is generally recognized that accurate prediction of circulating pressures is desirable, particularly in those areas where a delicate pressure balance is necessary to prevent both blowouts and lost circulation. For calculation purposes the standard hydraulic equations for the pipeline flow of Newtonian fluids have been altered to facilitate similar calculations for non-Newtonian or plastic fluids. This latter classification includes most colloidal types of drilling muds. Two properties: plastic viscosity, and Bingham yield value, are commonly used to define the flow characteristics of a plastic fluid. These are commonly obtained with multispeed viscosimeters such as the Fann V-G meter: Normally these measurements are obtained at some surface temperature, and are not corrected to circulating temperatures for calculation purposes. This may result in considerable error, particularly in the laminar flow calculations which commonly apply to the drill pipe-borehole annulus. The purpose of this study was to investigate the effect of temperature on the flow properties of some water-base muds. Experimental Procedure A laboratory model Fann V-G meter was used for measurement of viscosities, yield values and gel strengths. An aluminum water jacket with O-ring seals was machined to fit around the mud cup of the Fann meter. All mud samples were prepared by thorough mixing in a Hobart mixer. Viscosity and gel strength measurements were made with the Fann meter using standard procedures. Flow properties of muds were studied at 80, 120, 160 and 180°F. The compositions of the test samples are given in Table 1. Results Effect of Temperature on Flow Properties The typical effect of temperature on the flow properties of these drilling muds is illustrated by Fig. 1. It was found that plastic viscosity and apparent viscosity decreased with an increase of temperature. However, the curves were not linear, and did not appear to follow any definite trends or patterns. Yield point data showed much more scattering. Since a usable method for predicting drilling mud flow behavior with temperature was desired, an attempt was made to find a simple relationship between these variables.
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