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By Jasper Johnson

Taken in all its bearings there is, perhaps, no more interesting coal-field than that locally known and designated as " Wilmington," both on account of the superior qualities of its product as a household and steam fuel, when compared with other Illinois coal, and its geological position. The territory underlaid with coal, to which this name was originally given, embraced a very small area, including only the south half of sections 31 and 32 (township 33 north, range 9 east) in Wilmington township, and sections 5, 6, 7, 8, 17, 18, 19, 30, and 31, with occasional outliers in sections 3, 4, and 9, and, possibly, in sections 20, 28, 29, 30, and 32 (township 32 north, range 9 east) of Reed township, in Will County, comprising eleven square miles of workable coal within the known basin. Borings indicate the presence of coal on sections 30 and 33 in Wilmington

By John A. Church

In the year 1874, when the price of pig-iron was still high, that staple product became the subject of discussion in the newspapers and among those philosophers who are determined to know the "reason why" for all things. The object of the inquiry was to find out Why iron did not fall in price as much as some other things had fallen. Indeed, there seemed to be an impression that iron and gold ought to move on nearly parallel lines, for the fact was constantly brought forward that iron then cost twice as much as it did before the war, though gold had returned to within twelve or fifteen per cent. of its former value. After some time the papers, by what seemed to be nearly unanimous consent, reached the conclusion that the maintenance of high prices was the work of the furnace proprietors, who, as the result of their shrewdness, were pocketing enormous profits. No proof was given to support this opinion, and the figures of cost and sale that were produced were of the most general kind, and used in the most vague manner. Visiting the president of the Thomas Iron Company, whose great works at Hokendaqua and Catasauqua, in Pennsylvania, are so well known as the largest and among the best conducted in America, I found him quite willing to meet the vague suspicions of the newspaper wiseacres, by a publication of the figures contained in the furnace-books of his company. These were accordingly given to the world through the Engineering and Mining Journal, and attracted the general attention they so well deserve. Though my own name became connected with these statistics, from the fact that I used them as the basis for the first attempt ever made to calcalate the furnace economy of an American works, I can, without the suspicion of egotism, say that the statistics referred to are the most valuable contribution the literature of American blast-furnace work has yet received, for their interest is independent of personal considerations, and due entirely to the fact that they represent faithfully the details of practice in one of the most prominent American works. They are an exact transcript of the furnace-books, and form a body of accurate information of the greatest value to the metullurgical student. Their importance is shown by the fact that though the theoretical conclusions which I based upon them have been several times attacked, not one of my critics has made the slightest contribution to

The Institute assembled in the library of the Sheffield Scientific School at 8 o'clock, Tuesday evening, February 23d. Prof. G. J. Brush greeted the members present on behalf of the Government of the Sheffield School in a few words of cordial welcome, to which President Raymond responded. Dr. Raymond then delivered an address on the History of the Relative Values of Gold and Silver. The Council presented, through the President, a list of names of persons duly proposed for members and associates, with recommendation for election. The following gentlemen were unanimously elected: *Prof. George J. Brush,. .. New Haven, Conn. *Prof. Oscar D. Allen,. .. New Haven, Conn. *C. Constable,.....New York City. *Leven S Goodrich,.... Oxmoor, Jefferson Co., Ala. *Charles J. Nourse,.... Columbia, Lancaster Co., Pa. *J. W. Mickley,.....Hockendauqua, Pa. *Hugh Alex. Crawford,. ..St. Louis, No. *General Ario Pardee,. .. Hazleton, Luzerne Co., Pa. N. W. Lord,.....New Pork City. J. Holme Maghee,.... New York City. *George E. B. Jackson,. .. Portland, Me. *Charles W. Watkis,.... Salt Lake City, Utah. *Charles E. Hall,....Philadelphia. *Charles J. Duval,.... San Francisco, Cal. Joseph Gorlinski,.... Salt Lake City, Utah. * Alfred Wartenweiler,. .. Salt Lake City, Utah. Wilmot J. Bowen,.... Salt Lake City, Utah. *Joseph Stokes,..... Trenton, N. J. Jason P. Brown,.... Boston, Mass. *William Davis Hartshorne,. . Bethlehem, Hunterdon Co., N. J. *Henry Williams,.... Spanish Bar, Clear Creek Co., Cot. *Robert Forsyth ,....Chicago, Ill. *S. T. Wellman,.....Cleveland, Ohio. *H. C. Walton,.....Chicago, 111. *Andrew Roy,.....Columbus, Ohio. *James H. Rittenhonse,. .. Providence, Pa.

By A. J. Teplitz, R. J. Goodwin

A new type water shut-off for use in air drilling has been developed. The method has been 99 to 100 per rent effective in several different formations of inter-ranular-type porosity. Since costs for materials, time and equipment used are relatively small, the process should extend economies of air drilling to many new areas. The treatment involves a new technique for forming a water-inroluble precipitate within the pores of a rock. Advantage it taken of the difference in mobility of a liquid and a gas in porous media to achieve the greatest volume of precipitate in a given pore. Reactants selected for the laboratory (2nd field tests were aluminum sulfate solution and gaseous ammonia. This process has been tested in both intergranular and fractured-type porosities. It has consistently shut-of between 99 and 100 per cent of the water flowing from formations having intergranular-type porosity and perrlreuhilities ranging from a few millidarcise to over a darcy The treatment is not particularly suitable for shutting-off water from fractured formations although plugging of the order of 50 per cent or greater has been achieved in all such applications. Among advantages of the treatment are: (I) no reaction waiting rime after a relatively short placement time, (2) a low mate-rials cost of about $3/f1 of hole treated, (3) use of common service-type equipment for treatment, and (4) no unusual requirements for mixing and placement. INTRODUCTION In rotary drilling with air or gas it has been possible to increase bit life by tenfold and more than double rate of penetration over corresponding performance when drilling with mud. These factors have amounted to as much as 22 per cent savings on total cost of drilling a well. However, these advantages are rapidly lost when water is encountered in an air- or gas-drilled well because water interferes with the removal of cuttings from the hole and also gives rise to other difficulties. In attempting to combat water troubles, operators have commonly resorted to such measures as mist drilling, treatment with cement or chemicals, converting to conventional mud drilling, or setting casing. In many cases these measures have either been costly or ineffective. In an effort to overcome this problem, studies were undertaken to develop an effective and economical water shut-off technique for use in formations possessing inter-granular-type porosity. Extensive laboratory experimentation finally led to a unique method for producing a water-insoluble precipitate within the pores of a sandstone. The unique part of the treatment is use of a liquid and a gas to form the precipitate, and in this case the reactants used were aluminum sulfate solution and gaseous ammonia. The reaction between these two materials is shown in the following equation. Al2 (SO1)3 - 18 H20 6NH2? saturated Water- Solution Cat 2A1(OH)3 . n H20 3(NH4)2SO • n H20 Solid Solid That is, a solid precipitate consisting of aluminum hydroxide and ammonium sulfate is formed when ammonia reacts with aqueous aluminum sulfate. The aluminum hydroxide is insoluble in water and the ammonium sulfate, though soluble, can only be removed from the formation pores by diffusion—an extremely slow process. Although the precipitate formed by the reaction is not particularly firm, great strength is not needed for a precipitate to bridge and plug intergran-ular-type porosity. A flow path in such a system is extremely tortuous and involves a great variety of pore

By F. J. Fayers, J. W. Sheldon

A theoretical discussion is presented of the behavior of the interface between two fluids of different physical properties when displacement is occurring along a thin tilted bed. An approximate equation of motion is deduced for the motion of the interface, suitable boundary conditions are derived and the conditions necessary for the approximation to be valid are determined. Steady-state behavior and the circumstances under which a steady-state interface can develop are discussed. Finite-difference solutions of the equation of motion for two characteristic water-drive problems are presenled. The theory of displacement in a thin bed may be regarded as being the porous-medium-equivalent of the classical "shallow-water wave" theory of hydrodynamics. INTRODUCTION The solution of moving interface problems are important in predicting the behavior of oil reservoirs under various conditions of production. Kidder4,5 has obtained analytic solutions for the fingering problem and for another particular case of the motion of the interface between two immiscible fluids of unequal density in a porous medium. In the present analysis, we analyze the problem of the motion of an interface along a slightly dipping bed whose length is long compared with its thickness. The requirement of a thin bed is necessary in order to give a simple differential equation for the motion. The two fluids are of unequal density and mobility. In the derivation of the equation of motion, it is assumed that the lighter fluid is being injected at constant rate at the high end of the porous layer, while heavy fluid is produced at the low end of the layer. The analysis applies equally well, however, to the reverse procedure in which the heavier fluid is injected at the low end of the tilted layer. It will be shown that the behavior of the system is critically dependent on which fluid has the higher mobility and that the interface can in certain circumstances achieve a simple progressive steady-state shape. The fluids may be considered to be immiscible or miscible. It is assumed, however, that the thickness of the interface region is negligible in comparison with other dimensions of the system, and that the strength of the saturation or concentration discontinuity remains constant during the motion. In conjunction with Buckley-Leverett theory and areal sweep-out calculations, the tilted interface problem is one of the fundamental problems of reservoir engineering; it defines the very important underpassing and overpassing phenomena associated with water-drives, gas-drives and secondary recovery operations. The tilted interface problem has been dealt with previously by Dietz.2 In the present paper, we endeavor to derive the pertinent mathematical results more rigorously, and in doing so we obtain modifications in both the differential equation and boundary conditions for those given by Dietz. We also attempt to show the connection between these results and some of the recent work on the stability of interfaces. Finally, we attempt to demonstrate the practical importance of the thin bed theory by showing the difference in behavior of two characteristic waterflood problems. In the favorable mobility case recovery is improved by increasing production rate, while in the unfavorable case undercutting or overcutting is minimized by reducing the displacement rate. PROPERTIES OF THE EQUATION OF MOTION Fig. 1 illustrates a porous layer of constant thickness H and tilt 8 with Fluid 1 of mobility ?l and density pl below Fluid 2 of mobility ?2 and density p2. The fluids are incompressible and flowing with volumetric flux q along the layer. Both the slope a of the interface with respect to the bed and the curvature of the interface are assumed to be small. What is meant by "small" is indicated in the derivation given in Appendix A of an approximate equation of motion for the interface. Other symbols are defined in the "Nomen-

By E. B. Hunt

Paraffin deposition has been studied in the laboratory under conditions simulating deposition in well tubing. A theoretical analysis has been made of the cooling of the oil and the precipitation of paraffin from the oil as it flows up the well tubing and through surface flowlines. It is proposed that paraffin deposits are initiated by the precipitation of paraffin directly on or adjacent to the pipe wall and grow by diffusion of paraffin from solution to the deposit. This mechanism is consistent with laboratory and field observations, and has proved useful in the design and interpretation of laboratory paraffin-deposition tests. Tests have been made of the effect of plastic pipe coatings and chemical additives on paraffin deposition. INTRODUCTION Paraffin deposits which form in well tubing and surface flowlines interfere with production and must be removed. Over the years much progress has been made in developing and improving methods of removing these deposits after they form. Much less progress has been made in developing methods of preventing or inhibiting the formation of paraffin deposits. This is due, it is believed, to the lack of knowledge of the mechanism of paraffin deposition, the absence of satisfactory laboratory testing methods and the difficulties in evaluating the results of field tests of preventive treatments. The present investigation was undertaken to elucidate the mechanism of paraffin deposition and to develop suitable laboratory tests for studying the inhibition of paraffin deposition in well tubing and surface flowlines. Current theories on the mechanism of paraffin deposition have been evolved from field observations, from laboratory studies of various factors which might be involved in paraffin deposition, and from laboratory paraffin-deposition tests.1-9 Paraffin deposits have been formed in the laboratory by immersing a cold finger into a hot wax-oil solution and by flowing hot wax-oil solutions through cooled pipe or over cooled plates. These laboratory conditions differ in important features from field conditions, and the observed deposition behavior is not entirely field-like." Thus, there is reason to question the field applicability of the results of these tests. The present investigation was undertaken to determine how to perform and interpret laboratory paraffin-deposition tests to obtain information on the inhibition of deposition in the field. The paraffin problem in the broadest sense encompasses the formation of any predominantly organic deposit in well tubing, surface flowlines and other equipment in contact with crude oil or gas. The present investigation was limited to paraffin deposition involving the precipitation of paraffin wax from solution by cooling and its concentration in a deposit on a cooled surface. This probably excludes its applicability to those problems arising from asphaltic-base crudes, but not those arising from paraffin-or mixed-base crudes. This also excludes its applicability to emulsion and congealing oil problems which are often included as part of the paraffin problem. The phenomenon of cooling appears to be the controlling factor in paraffin deposition involving the precipitation of paraffin wax and its concentration in the deposit. Deposits of this type are usually found in the field only where cooling occurs. Early in this laboratory investigation, it was not found possible to form deposits under constant temperature conditions from a wax-oil slurry, either by steady flow through pipe or by gas-lift up a pipe. Thus, the investigation was limited to situations involving cooling. THEORY The relationships involved in establishing the temperature profiles in an oil stream as it flows up well tubing with a linear (geothermal) pipe-wall temperature distribution or through surface flowlines with essentially constant pipe-wall temperature are presented in the Appendix. The relationship between radial distance in the pipe and the rate of cooling of the oil is then combined with a relationship between cloud point and rate of cooling to develop the pattern of formation of a wax cloud in the oil. The following discussion of paraffin deposition under various laboratory and field conditions is based upon this development which is presented in the Appendix. PARAFFIN DEPOSITION IN SURFACE FLOWLINES The average temperature of the oil coming out of a well is somewhat higher than the ground temperature. Thus, the oil continues to cool on its trip through the surface flowline, and wax deposition can occur. The temperature distributions calculated from Eq. A-4 are given in Fig. 1. As can be seen, almost all the cooling occurs in the first 500 ft from the wellhead. In addition, the radial temperature gradient near the wall decreases rapidly with distance and becomes very small after a few hundred feet. Thus, growth of a paraffin deposit would be expected to decrease rapidly with distance from the wellhead and become negligible after a few hundred feet, since growth is dependent on concentration gradient. Wax precipitation and diffusion of wax to the already

By J. C. Savins

The practical analysis of the hydrodynamics of the wellbore has long been a subject of interest to engineers. This paper presents a simplified solution to the problem of computing the pressure drop for the flow of drilling mud in the annulus of the wellbore. This solution is, however, an exact and rigorous solution under the assumptions which have been imposed. These assumptions are that the drilling fluid is a Bingham plastic fluid* and that the annulus is formed by two concentric, stationary, cylindrical pipes. It is further assumed that the fluid is incompressible and that its motion is isothermal and in a steady state. This problem under the same assumptions has been attacked by previous authors. Beck, Nuss and Dunn' proposed that the equation for the flow of a Bingham plastic fluid in a cylindrical pipe could be applied to an annulus if the pipe radius were replaced in the equation by the hydraulic radius. This equation, known as the Buckingham-Reiner equation' (see Appendix 1), was also used in an approximate form. Van Olphen pointed out that even for a simple or Newtonian- fluid the pipe equation (Poiseuille's law) could not be converted to the Lamb equation escriptive of flow in an annulus (see Appendix 1) by using the hydraulic radius. Van Olphen further attempted to give a solution for the annular flow of a Bingham plastic fluid by introducing approximations similar to those which have been used in the case of the Buckingham-Reiner equation. Other attempts to provide approximate or exact solutions have been made by Grodde' and by Mori and Ototakeq. The present authors some years ago in unpublished work derived the correct expressions relating the pressure drop and flow rate for this problem. It was found that the solution consisted of two simultaneous equations, one of which contained a logarithmic term. Thus, obtaining numerical results for any particular case of interest involves very tedious trial-and-error computations. Very recently Laird presented the correct derivation of the two equations which are given in full detail in Appendix 1. In order to reduce the amount of calculation time which would be involved in providing a complete tabular or graphical solution to the problem, a high-speed electronic digital computer has been utilized. For this purpose the two simultaneous equations were transformed into more compact expressions by introducing reduced variables. These expressions are given in the following theoretical section. A similar procedure in this problem has been developed by Fredrickson and Bird1" Their tabular results, however, are very incomplete in the range of practical interest for problems of wellbore hydrodynamics. We have furthermore been able to express our graphical results in terms of convenient and familiar dimensionless groups. THEORETICAL DEVELOPMENT Use of Reduced Variables In terms of reduced variables the two simultaneous equations just discussed take the following form, The reduced variables q, x, a and z are defined in terms of the various measured quantities, where Q is volumetric flow rate, AP/L is pressure gradient, Dl is OD of inner pipe, D, is ID of outer pipe, is plastic viscosity, and is yield point. Thus, we have a dimensionless volume flux, a dimensionless reciprocal pressure gradient, and the ratio of the pipe diameters Before introducing the fourth reduced variable, z, it is of interest to consider the physical significance of the parameter x. As may 'be seen from the velocity profile of Fig. 1 the Bingham plastic fluid has the interesting property that a portion of the stream flows at a uniform velocity without shearing action. This section of the stream is situated approximately in the center of the conduit and is known as the "plug flow" region. Its existence is due to the fact that the shearing stresses within the region do not exceed the yield point, which is one of the two flow properties characterizing the fluid. The parameter x then turns out to be the ratio of the

By Andrew Roy

The Mahoning Valley coal region lies on the extreme northern outcrop of the Ohio coal-field, and all the mines, with one exception, are opened on the lower coal of the series, No. 1 of the Ohio Geological Survey. The coal ranges from an inch to five, six, and sometimes seven feet thickness, the workable height being between two and a half and six feet. There are two varieties of coal, known in market as "Briar Hill coal " and " Mineral Ridge coal;" both varieties are drawn from the same seam. The Briar Hill coal is generally called block coal, and is the kind so largely used in a raw state in smelting iron. It possesses a laminated structure, easily splitting into horizontal sheets, but is very difficult to break in the opposite direction. The faces of the layers are often covered with a soft, dead, carbonaceous material, like charcoal, and the whole seam throughout is marked by alternate layers of dead and bright-looking coal. In the act of combustion the coal neither swells nor changes form, the masses retaining their shapes until they fall to ashes in the furnace. The Mineral Ridge variety is much softer, and is also shorter in the grain than the Briar Hill kind, and it contains a good deal of

By R. J. Blackwell, J. R. Rayne, J. R. Henderson, W. M. Terry, D. C. Lindley

This paper presents the results of a laboratory investigation of the efficiency of water-solvent mixtures in recovery of oil. These mixtures may have the high displacement efficiencies characteristic of solvent floods and the high sweep efficiencies characteristic of water floods. Thus, the water-solvent process may increase the number of reservoirs in which a miscible-type displacement can be used profitably. The experiments on the use of water-solvent mixtures for recovery of oil were conducted to find the general applicability of the process. These studies demonstrated that, in flowing through sands, water and solvent segregated into a solvent layer on the top and a water layer on the bottom rather than flowing through the sands as a uniform mixture. Calculations based on the simultaneous flow of the water and solvent in layers were used to predict the effective mobility of the mixtures and the optimum operation of the process in steeply dipping, homogeneous reservoirs. As most reservoirs are not suited for the operation of the process under ideal conditions, experimental studies were conducted with sand-packed models scaled to represent more realistic reservoirs. These studies included the effects on recovery of oil of rate of injection, viscosity of oil, variations of permeablity within a formation and variations in water-solvent ratio. For the range of con-ditions studied, higher recoveries of oil were obtained with water-solvent mixtures than with water or practical volumes of solvent alone. INTRODUCTION A group of intriguing—because of their great possibilities—new oil recovery methods at the disposal of the petroleum engineer are the miscible displacement processes. These processes (high-pressure gas drive, en-riched-gas drive and LPG bank driven by methane) displace all of the oil from the portions of the reservoir swept by the injection fluid. The key question confronting the engineer applying one of these techniques to a particular reservoir is, "What fraction of the reservoir can be swept by injection of a practical volume of solvent?"." Intensive laboratory studies have been made during the past several years in seeking answers to the question of the sweep efficiencies which can be expected in solvent floods.' - These studies provided the answer that low-viscosity, low-density solvents channel and by-pass oil in sands with no dip. In horizontal sands, solvent flooding becomes less efficient as the viscosity of the oil increases, the recovery of oil at solvent breakthrough decreases and larger volumes of solvent are required to achieve a given recovery. More efficient displacement of oil by solvent is observed under certain conditions in sands with dip.".' If the permeability and dip of the sand are sufficiently high, gravity segregation of low-density solvent injected updip can prevent channeling. At rates of depletion below a critical rate,"." no channeling occurs. Unfortunately, in many reservoirs, the critical rate is so low that production of oil at rates below this rate is not economically attractive. And at rates over four times the critical rate, channeling is almost as severe in sands with dip as in horizontal sands. These findings pointed out that, for solvent floods to be generally applicable in recovering oil from all types of reservoirs, new methods of improving their sweep efficiencies are needed. Simultaneous injection of water with the miscible fluid was suggested by Caudle and Dyes7 as a method for improving sweep efficiencies. They theorize that water flowing with the solvent would decrease the effective mobility of the solvent and cause it to contact more oil sand. If, indeed, the water and solvent flowed as a uniform mixture, the process should have the advantages of the high displacement efficiencies characteristic of miscible floods and the high sweep efficiencies of water floods. Thus, the method (at least in theory) would greatly increase the number of reservoirs in which miscible-type displacements would be feasible. A research program was conducted to probe the technical feasibility of the water-solvent process. It

By J. C. Bartlett

As American students of mining, philosophy, philology, music, history, or art have found it necessary or highly advantageous to supplement their course of study at home by a residence of some years at a foreign university, so, ever since mining has been practiced in this country in any other than a rude and wasteful manner, many American students of mining have sought in London or Paris, but chiefly in the Academy of Freiberg, Clausthal, or Berlin, such infor-

By R. P. Rothwell

AT this our first meeting I beg to call the attention of the members of our Institute to what is certainly a question of the greatest possible importance to the industries we represent; and more particularly to the welfare of the coal and iron trades: I refer to the enormous waste of coal in mining and in its preparation for market, as now practised in our anthracite coal-fields. I t is a fact which many of you can certify to, that we are wasting fully me-half of all the coal in the veins we are now working, and there are cases, which might be mentioned where this proportion, immense as it is, has been greatly exceeded. The popular belief that our deposits of anthracite coal are "practically inexhaustible," is very far from being founded on facts. On the contrary, supposing the present rate of increase in the production to be maintained, it is probable that a maximum yield for our coal-fields would be attained in about fifteen years ; there are in fact some of our smaller basins where the principal veins are nearly exhausted and the production has already attained its maximum. There are others, again, where the depth attained-and it must be borne in mind that we commenced working at the surface outcrop moderate though it is (scarcely ever reaching eight hundred feet), has so increased the cost of mining as to imperil the capital invested, and though it requires but little foresight to predict the time when the difficulties of mining will be very considerably increased by reason of the greater depth, greater quantity of water, fire-damp, and other fruitful sources of cost, yet, ignoring these recognized facts, we continue to waste more than one-half of the coal where it is obtained with the least danger, expense, and trouble, that is, near the surface-either above water-level or at a moderate depth . below it. The inspection of almost any accurate mine map will satisfy you that, on an average, we leave fully one-third. of the coal in the ground as pillars to support the roof; in some places more than one-third thus remains, while it is very rare that less than one quarter is left. In almost every case this coal is absolutely lost, for it will very rarely pay to reopen gangways and lay roads to it after that portion of the mine has been abandoned. Is it necessary in all cases to support the roof, and where it is, may not some artificial

By W. W. Whitaker, C. W. Manry, R. H. McLean

In an eccentric annulus, cement may favor the widest side and bypass slower-moving mud in the narrowest side. Tendency of the cement to bypass mud is a function of the geometry of the annulus, the density and flow properties of the mud and cement and the rate of flow. Bypassing can be prevented if the pressure gradient protluced from circulation of the cement and buoyant forces exceeds the pressure gradient necessary to drive the mud through the narrowest side of the annulus at the same velocity as the cement. In the absence of buoyant forces, one requirement for this balance is maintenance of the yield strength of the cement greater than the yield strength of the mud multiplied by the maximum distance from the casing to the wall of the borehole and divided by the minimum distance. If the yield strength of the cement is below this value, bypassing of mud cannot be prevented unless buoyant forces or motion of the casing significantly aid the displacement. INTRODUCTION Successful primary cementing leaves no continuous channels of mud capable of flow during well treatment and production. Prevention of channels requires care. Tep-litz and Hassebroek provide evidence of channels of mud after primary cementing in the field.' Channeling of cement through mud in laboratory experiments has also been reported.'-' Recommendations for improving the displacement of mud include (1) centralizing the casing in the borehole,'-" 2) attaching centralizers and scratchers to the casing and moving it during displacement,18 "3) thinning the isolating the cement by plugs while it is circulated down the casing,%( (5 establishing turbulence in the cement," and (6) holding the cement slurry at least 2 lb/gal heavier than the mud and circulating the cement slurry at a very low rate of flow.' Although much has been written about the above parameters, the relative importance of each has not been well defined. In this investigation, the mechanics of mud displacement are described through results from analytical models and experiments. The model chosen — a single string of casing eccentric in a round, smooth-walled, impermeable borehole — is analagous to casing centralized in a borehole which is not round and to placing more than one string of casing in a borehole. In each, some paths for flow are more restricted than others. A fluid flowing in the borehole may seek the least restricted, or most open, path. This tendency for uneven flow can lead to channeling of cement through mud unless preventive measures are taken. The analytical models describe channeling and give means of balancing the flow. Experimental data test the analytical models and illustrate effects of motion of the casing, differences in density and mud's tendency to gel. Results are encouraging. Piston-like displacement of mud by an equal density cement slurry is possible through proper balance of the flow properties of the mud and cement slurries to the eccentricity of the annulus. The more eccentric the annulus, the thicker must be the cement relative to the mud. If proper balance is not achieved. bypassing of mud by cement cannot be prevented without assistance from motion of the casing or buoyant forces. Increasing the rate of flow can help to start all mud flowing but cannot prevent channeling of cement through slower moving mud in an eccentric annulus. Thinning the cement slurry tends to increase channeling although the extent of turbulence in the annulus may be increased. Description of flow in an eccentric annulus begins in the next section. It is assumed that (1) the casing is eccentric and is stationary, (2) the mud and cement slurries have the same density and (3) the gel structure of the mud has been broken and the mud and cement follow the Bingham flow model. Effects related to these restrictions will be discussed. FLOW PATTERNS SlNGLE FLUID IN ANNULUS Flow of a single fluid through an eccentric annulus is illustrated in Fig. 1. Part A shows laminar flow of a Newtonian fluid. This distribution of flow was calculated by Piercy, Hooper and Winney.' In fully developed turbulent flow, the velocity distribution around the annulus is less distorted, but the flow still favors the widest part of the annulus Parts B, C and D of Fig. 1 are a qualitative representation of the flow of a Bingham fluid. The yield strength of the fluid increases the severity of bypassing compared to Newtonian flow. At a very low rate of flow, all flow is confined to that portion of the annulus which has the minimum perimeter-to-area ratio. The fluid shears on the perimeter of that area when the pressure gradient multiplied by the area just exceeds the yield stress of the fluid multiplied by the perimeter. Whether or not the minimum perimeter-to-area region encompasses all of the annulus or only a part (as shown in Part B) depends on the geometry of the annulus. If only a part begins to flow, increasing the rate of flow increases the area flowing until finally there is flow throughout the annulus.

By C. E. Kemp, A. B. Dyes

Results of a field research project on the thermal recovery of oil by movement of a combustion front are presented. This field test was conducted in the South Belridge field, This The war paitern was a Southsing1e 2.5-acre five-spot pattern in the 700-ft deep Tulare sand. Results of this project indicate the technical feasibility of producing high viscosity, low-grallity crude oils by thermal means. It was demonstrated that heavy oils could be moved rapidly over considerable distances by thermal drive, and that high percentage recoveries of oil could be effected. The bulk of the oil recovery came after arrival of the burning front at a production well. However, rapid corrosion and high-temperature failure of conventional pipe and equipment both below and above surface occurred. Stainless steels gave more satisfectory performance under these conditions than did conventional steels. Oxygen was seldom observed in gas from wells ahead of the burning front, and it appears that the front was continuous throughout the life of the experiment. INTRODUCTION During late 1953 and early 1954, industry-wide attention was focused on the thermal recovery of oil by movement of a combustion front through an oil zone. Two separate Oklahoma field tests were described in publications by Kuhn and Koch, and Grant and Szasz. To obtain basic information needed for making engineering and economic appraisals of commercial recovery of heavy oil by this thermal recovery method, a new field research projecta3,4 was started May 31, 1955. Twelve oil companies contributed to this project with General Petroleum Corp. as operator. Since combustion recovery experiments* with heavy oils in other areas had been conducted in small patterns,"' an important purpose of this test was to determine whether the process could be operated in a pattern of near-commercial well spacing. The south Belridge field, located 30 miles north of Taft, Calif., was chosen because its oil sands are similar to many heavy oil sands which typically have low primary recovery and leave a large amount of oil in place. such fields are not particularly suited for common secondary recovery methods. DESCRIPTION OF TEST SITE The test interval was a Tulare sand at a depth of about 700 ft. Nine test wells were drilled, cored and completed from Oct., 1955, through Jan., 1956. The initial pattern shown on the map, Fig. 1, consisted of an injection well (II)', four producing wells (1P-4P), and four observation wells (IT-4T). An old well (81) was also recompleted for use as an observation well. The area enclosed by the original four production wells was 2.5 acres; the distance from the injection well to each production well was 233 ft. During the combustion period, Well 5P was drilled to replace Well 2P, and Well 6P was drilled to replace Well 3P. The new wells were 25 ft beyond the old production wells along a diagonal from the injection well, and resulted in an increase in pattern area to 2.75 acres. Isopachs are shown in Fig. 1. The average thickness of the oil sand in the test pattern was 30 ft. Fig. 2 presents two cross sections through the test pattern. Oil sand is represented by white and claystone by gray. The dashed lines indicate layers of conglomerate grading to claystone. The sand thickness was fairly uniform throughout the test pattern except in the 1P area. The sand body dips gently from the northwest to southeast, about 3 degrees from horizontal. The sand is unconsoli-dated, and grades from very fine material to pebbles as large as 2 in. in diameter. Table 1 presents the average initial properties of the formation. The in-place porosity of 37 per cent was estimated from the porosity of coke-consolidated cores taken after combustion. Original core analyses data were adjusted to 37 per cent, giving pore volume saturations of 60 per cent oil, 37 per cent water, and 3 per

By Lewis A. Riley

I desire to submit, for the consideration and information of the members of the Institute, the following data, drawings, and tables, showing what I believe will be interesting information with regard to the diamond drill, and its uses in developing mineral lands. I would first say that the results given have been obtained during the past two years by means of two drilling machines belonging to the Lehigh Valley Coal Company, operating on their coal lands in the Mahanoy, Lehigh, and Wyoming regions. 1st. A tabulated statement, giving location of borings, date, progress, total cost, itemized cost per foot, etc. 2d. Section showing strata bored in Nos. 5 and 10 holes at Mt. Carmel, see Plate VI. 3d. Section showing strata bored in No. 19 hole at Hazleton, see Plate VI. 4th. Photograph and description of drill No. 2. From the first it will be seen that the total number of test-holes bored up to May 1st of this year is 24; 9 of these are in the Mahanoy region, 6 in the Lehigh region, and 10 in the Wyoming region, in all of which cores have been taken for the whole distance. The total distance bored is 9902 feet. The majority of the holes have been put down for the purpose of proving the lower veins of the coal series, and have had to encounter the harder rocks of the coal formation. Much of the distance has been through the lower conglomerates, going in some cases through the coarse egg conglomerate, the foundation of the coal deposit, and to the green sandstone and red shale which underlie it. These lower sandrocks and conglomerates are among the hardest known to geologists, and present a formidable resistance to the exploring drill. This fact must be taken into consideratiotl in comparisons of cost of drilling, and when considered will still further improve the very favorable results I am able to show in my statement of costs. In illustration, I will cite the work of one bit when boring in the upper or softer rocks of the Wyoming region, where 280 feet were obtained without resetting, while in the Lehigh and Mahanoy regions, in the lower and harder rocks, bits set with the same quality of diamonds would only bore from 3 to 20 feet before being worn out. In this connection it may

By A. Eilers

Although the process to which I refer in this paper has been in successful operation for nearly five years, during which time it has been introduced, superseding all other processes having in view the same end, in almost every lead refinery in the country, no description of it, giving economical data, has ever appeared in print, nor has the process been known in its details to any considerable number of engineers beside those conducting it at their works. A discussion of this subject at the present time becomes especially interesting in view of a late publication in the Prussian ministerial organ for Mining and Metallurgy, by Dr. Wedding, in which the method of treating the zinc-silver-lead alloy by distillation, as finally settled upon at Tarnowitz, is very minutely and fully described. It is the more interesting, because in that article reference is made to the American method in an unfavorable light, while, at the same time, it is clear from the article itself, that the most important details of the process, besides the one that it is conducted in black-lead retorts, mere not at all understood. In publishing herewith the details of our American method, one of my objects is to invite comparisons between our simple and direct process and the elaborate one at Tarnowitz. In extracting the silver from work-lead by means of zinc, it is always the intention, in this country, to obtain a zinc-crust so rich in silver that the rich lead resulting from subsequent distillation

By Fred H. Poettmann, A. L. Benham

correlation of waters and identification of mixtures of two and three waters is important in secondary recovery evaluation studies and studies involving underground movement of waters. The importance of such studies suggests the need for a method to correlate a great number of water analyses to accurately identify and improve the understanding of mixtures of waters. Geochemical analyses of waters furnish a quantitative measure of each of the ions present in a water. Table L shows a portion of the data on many oilfield water analysis report forms in use today. Under "parts per million" are listed the quantitative amounts of each ion in milligrams per liter. Following the work of Stabler' and Palmer", some laboratories have reported additional data to indicate the reaction capacity, or reacting value of each ion. Table I lists data under two subheads for the "reacting value". Under the first subhead, the reacting value is reported in gram equivalents per million, hereinafter called equivalents per million. This value is determined by multiplying milligrams per liter of the ion by a factor equal to the reciprocal of the equivalent weight of the ion. Under the second subhead (per cent) is listed the percentage of each ion based on the total equivalents per million. Sodium is not usually an analyzed value in routine analyses, but is determined by the difference between total negative equivalent per million values and the sum of all of positive ion values for which analyses were made. This difference is reported as sodium, hereafter labelled "sodium". On this basis, the subtotals of the equivalent per million and per cent reacting values of the positive and negative ions are equal. CORRELATION OF WATER ANALYSES DATA Previously reported methods for correlating oilfield waters have used part of the data in Table 1, and can be classified into two categories. Correlation by Chemical Character Correlation methods using the chemical character of waters, as represented by the per cent reacting values of the ionic constituents, have been used by Palmer2 and Tickell. These methods have the limitation of neglecting the ionic concentration of the waters. This limitation can be serious in areas where waters have the same chemical character, but differ in concentration. Correlation by Concentration of the Ionic Constituents The Reistle' and the Stiff methods use the ionic concentration in parts per million and equivalents per million. These methods are effective in differentiating waters of similar chemical character and varying concentration, as in the highly saline waters of the Mid-Continent area. These methods have the disadvantage that they correlate waters by comparing many graphs of individual water analyses to determine the similarity to, or the variance from "type" waters. PROPOSED METHOD OF CORRELATING WATER ANALYSES DATA Correlation graphs presented in Fig. 1 represent water analyses data as points to facilitate the correlation of waters. The graph on the left of Fig. 1 is a plot of per cent reacting value of magnesium vs calcium. The right

By J. D. Alexander, W. L. Martin, J. N. Dew

This paper presents data obtained using a flood-pot technique to determine the fuel available and the corresponding theoretical air requirements for in situ combustion of crude oils. Since the technique is relatively quick and easy, it is a practical and convenient tool for evaluating reservoirs as fireflood prospects. It is also a research tool which facilitates systematic study of the variables affecting fuel availability and corresponding air requirements. The understanding of these variables is of prime importance to those concerned with the technical and economic development of in situ combustion as an oil-recovery process. The experimental results show conclusively that the fuel available for in situ combustion is not a constant but, rather, varies with crude-oil characteristics, porous-medium type, oil saturation, air flux and time-temperature relationships. Thus, the fuel availability for specified field applications should be determined using actual reservoir crude and core material and the process conditions expected during in situ combustion in the reservoir. INTRODUCTION In situ combustion is a thermal process for recovering crude oil from reservoirs. The thermal energy released during the combustion of a small amount of the oil in place aids in the displacement of the remaining oil. Numerous articles have been published describing the in situ combustion process giving detailed results of laboratory and field experiments.10 In order to engineer an in situ combustion project, a number of important factors must be considered and determined. These factors include: (1) the amount of fuel consumed per unit of reservoir volume swept by the combustion zone, (2) the composition of the fuel consumed, (3) the amount of air required to consume this fuel, (4) the portion of the reservoir swept by the combustion zone, (5) the appropriate air-injection rates and pressures, (6) the amount of oil that will be recovered, (7) the rate of oil production and (8) the operating costs. Nelson and McNiell1 recently have described a procedure which utilizes laboratory combustion-tube data as a basis for the calculation of some of these design factors. Various authors have attempted to describe the in situ combustion process mathematically, and considerable progress has been made. Analytical solutions to the problem of heat transfer from a moving combustion front have been obtained for linear and radial systems."-' All of the published results involve the assumptions that: (1) fuel concentration is constant throughout the reservoir, or that fuel concentration is inversely proportional to the velocity of the front for a given rate of oxygen consumption; and (2) the fuel reacts instantaneously with injected oxygen, while liberating a constant amount of heat per unit weight of fuel at all temperatures. It seems both desirable and reasonable to test the validity of these assumptions experimentally. This paper presents laboratory data which were obtained by means of a "fire flood-pot" method for determining fuel availability and composition, and the corresponding theoretical air requirements for in situ combustion of crude oils under variable conditions. The mechanics of the method are similar to a conventional tube-run experiment.' The important differences involve the size of the reservoir model used and the method for providing the experimental environment. The new method subjects conventionally-sized core samples or unconsolidated sands to a programmed environmental sequence similar to that experienced by a similar volume of rock during the approach and passage of a combustion front in a long tube or in an oil reservoir undergoing in situ combustion. Restored-state samples can also be used. The small samples and relatively simple techniques involved allow an experiment to be set up, run and calculated in about three 8-hour days. This is a considerable improvement over long-combustion-tube techniques which can require several days to run and several more work days to set up and calculate. All the runs presented were run at 40-psig injection pressure. Pressure was not considered as a variable for these experiments, since we previously had found that it had only a small effect on fuel availability up to 600 psig.APPARATUS AND MATERIALS APPARATUS The fire flood-pot apparatus consists of a consolidated