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US 3126950 A
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March 31, 1964 'B. CARLBERG ETAL 3,126,950
METHOD EMPLOYING COMBINATION WELL COMPLETION-PACKER FLUIDS Filed Dc. 4, 1959 s Sheets-Sheet 1 BOBBIE L. CARLBERG CHARLES M. HUDGINS, JR.
JAMES E. LANDERS INV EN TOR-S.
THEIR AGENT March 31, 1964 Filed B. 1.. CARLBERG ETAL "3,126,958
METHOD EMPLOYING COMBINATION WELL COMPLETION-PACKER FLUIDS Dec. 4, 1959 3 Sheets-Sheet 2 2Q CORROSION RATES OF I020 STEEL COUPONS IN CoC| ZnCl H O SOLUTIONS; I6
CORROSION RATE (MPY) CORROSION RATE (MPY) IO ll l2 l5 l4 DENSITY #IGAL.
CORROSION RATES OF I020 STEEL COUPONS IN cl zncl H2O SOLUTIONS 5 INiTIAL p H (BECKMAN) FIG. 3
BOBBIE CARLBERG CHARLES M. HUDGINS JR.
JAMES E. LANDERS THEIR AGENT B. L. CARLBERG ETAL 3,126,950
' March 31, 1964 METHOD EMPLOYING COMBINATION WELL. COMPLETION-PACKER FLUIDS 3 Sheets-Sheet 3 Filed Dec. 4, 1959 BOBBIE L. CARLBERG CHARLES M; HUDGINS, JR. JAMES E. LANDERS mmvron s. BW%Q k wmmxxxm F IG. 4
' THEIR AGENT United States Patent C) METHUD EMPLQYING COMBINATION WELL COMPLETIQN-PACKER FLUIDS Bobbie L. Carlberg, Charles M. Hudgins, .ln, and James E. Landers, Ponca City, 01th., assignors to Continental Oil Company, Ponca City, Okla, a corporation of Delaware Filed Dec. 4, 1959, Ser. No. 857,354 8 Claims. (Cl. 166-1) The present invention is directed to an improved well completion fluid and techniques in the practical application of same for controlling a well during completion and While the well is in production and varying modifications of an article embodying structure for producing fluids from subterranean stratum. More particularly, the invention is directed to a method of controlling wells and an article employing a low-cost well completion fluid having a controllable density, heat stability, one which Will not separate into phases or permit the precipitation or settling out of solids, and the property of being noncorrosive to ferrous metals to which it is in contact with in well completion operations. Other and still more particular objects are a completion-packer fluid and an article incorporating same which is satisfactory for controlling multiple completion wells and thus obviates the peculiar problems associated therewith.
Current practice when completing wells, such as oil and gas wells, through perforated casings is to have drilling fluids, such as mud, salt water, water, or oil, in the well casing and to perforate the casing with bullet, shaped charge, chemical or punch-type perforators. When the pressure of a formation traversed by the well exceeds the hydrostatic pressure of a column of oil or water at the completion depth, it is customary to use local native salt water which has a limited density for short durations when they are not excessively corrosive at least, or normal drilling mud having a density great enough to exceed formation pressure in order to control the well while perforating the casing and performing other routine completion operations. When the casing is perforated, under drilling mud, the drilling mud flows into the perforations because of the positive pressure differential existing between the interior of the casing and the formation. The perforations are thereby partially or completely plugged with mud, and this plugging is aggravated by the heat and instantaneous pressure evolved by the propellant powder in the case of bullet perforators and the high explosive in the case of the jet or shaped charge perforators. Where chemical or punch-type perforators are employed, it is not uncommon for the drilling mud to lose water rapidly to the formation resulting in the drilling mud becoming dehydrated and forming plugs. The loss of water need not be great, as these muds are usually very viscous. Such plugs whether formed by dehydration of the drilling mud by heat, and/ or pressure or by loss of water to the formation are difiicult to remove by subsequent flow from the formation into the well bore and by that the productivity of a perforated interval in a producing formation is significantly reduced. Field completion attempts of wells indicate that such plugging of the perforations may cause formations tested being termed nonproductive and thereby condemned when actually the formation may contain economically producible oil or gas. Solids such as in muds can and often do interfere with operations directed to consolidation of loose sands. Thus, it is clear that the problem of plugging of perforations is serious and is a source of expense in well completions and of erroneous conclusions in exploratory work which may cause major hydrocarbon reserves to remain undiscovered with consequential mineral and economic losses.
Another problem which exists in perforating wells is that it is necessary to provide control of the Well during perforations. This is accordingly accomplished by maintaining a hydrostatic column which exerts a pressure greater than the formation pressure exposed when the casing is perforated. However, to provide a column having a sufiicient hydrostatic pressure, it is necessary to add weighting agents such as barites, or other heavy solid materials to the fluid column maintained in the well.
For various reasons, it has become the practice in the petroleum industry to drill deeper and deeper wells and very often also to complete said wells at a plurality of Zones. This, of course, has presented additional new and unique problems in the art of completing and producing wells. Also the closely related problems of work-over of Wells has been greatly magnified by the advent of and specifically in multiple completion wells which is at least in part due to prior completion factors. For example, after completing operations on an oil well to place it into production, a completion fluid again is employed to fill the annular space between the casing and tubing above packers and left there throughout the life of the well or until reworking is called for.
The purpose of using such annulus or fill-up fluids to fill the annular space between tubing and casing above a packer after a well is completed and producing is to maintain a hydrostatic pressure at the top or up-bore side of the packer. A pressure desired at such points is one slightly greater than the highest pressure of all the producing formations. In this way, the hydrocarbons being produced exert only a slightly lesser pressure on the bottom side of the packer than the completion fluid exerts on the top side of the packer. Thus by reducing the differential pressure between top and bottom of a packer, the crude oil and other fluids exiting from the formation will not leak or bleed around the packer and/or control of the well will not be lost. The disadvantages and deleterious consequences of bleeding around packers by such fluids are well known to those skilled in the art. The consequences of losing control of a well are still better known. Similarly and especially with regard to multiple completion wells, the consequences of a completion fluid which separates into phases, is corrosive to ferrous metals and/ or which precipitates out of solids with subsequent sedimentary build-up on packers and the like is well known and appreciated by those versed in the art.
In drilling deeper and deeper wells in search for pctroleum-producing formations, the temperatures encountered have increased to an extent that difficulties nonexistent theretofore have been encountered. Temperatures of the order of 200 to 250 F. or even higher may be encountered in oil and gas wells. At these temperatures, certain emulsions which may be used as completion fiuids will become unstable and resolve into their component parts over a period of years. Also, where the emulsions contain certain halogenated hydrocarbons, such as carbon tetrachloride, at the high temperatures to which the fluids are exposed, the particular halogenated hydrocarbons may break down to form corrosive fluids which will damage ferrous metal tubing and pipe with which it may come into contact. It is, therefore, desirable to provide a heat stable fluid which will maintain and preserve its characteristics at high temperatures encountered in deep wells and will also be noncorrosive to the ferrous metal conduits with which it comes in contact and which will not separate into phases or precipitate solids with resulting various disadvantages.
Temperature as a rule increases linearly with depth. Many factors affecting temperature may vary in subterranean locations and the subterranean temperatures even in comparatively close locations may vary considerably. The occurrence of such and the reasons therefore are well known in the art. Thus, despite the general rule that temperature increases with depth, comparately high temperatures are sometimes encountered at relatively shallow depths, for example, at 3,000 feet. At depths beginning at about 15,000 feet, high temperatures are encountered without exception regardless of location. High temperatures, then, may be encountered at any depth below about 3,000 feet. These high temperatures when encountered regardless of depth accentuate or accelerate the disadvantages of prior art completion and packer fluids.
High temperatures at deeper zones are not the only temperatures which can be seriously disadvantageously encountered in wells. Cool temperatures can also present a serious problem. Consequently, another advantage of the present completion packer fluids is the low freezing point of the solution. Water, as is well known, freezes at 32 F. and 760 mm. pressure. However, the freezing point is lowered by the addition of applicants weighting agents CaCl and ZnCl The freezing point of solutions having densities in the range contemplated is below 40 F. Many of the prior art fluids will separate into phases or freeze completely to a solid mass at temperatures higher than 40 F. This makes prior art fluids unsuitable at least as packer fluids in some geographical areas where temperatures in the upper zone at least part of the time are too low.
Illustrative examples of our fluid having a freezing point below 4-0 F. are:
CaClz, weight ZnClz, weight Approximate percent percent Density An especial problem encountered with prior art completion fluids has been their inability to serve satisfactorily for periods on the order of 10 to 30 years or even longer, particularly in view of the previously mentioned conditions which are experienced. Inasmuch as workover operations are of great importance and performed after the expiration of times as mentioned hereinabove, any truly effective completion-packer fluid must be capabio of serving over long periods of time without increasing or causing difficulties, expense, and hazards in such operations or worse yet prohibiting their performance entirely.
in accordance with the present invention, these several problems in well completion and subsequent reworking operations are materially reduced by providing an improved well completion-packer fluid according to hereinafter which has a controllable density, which is stable in the wells over a period of years, which is noncorrosive to the ferrous metal conduits and will not contaminate the formation as to be detrimental to subsequent desirable operations. For the many servicing operations on a well, this solution may be employed in the wellbore except as a satisfactory fracturing fluid.
We have found that a very effective and satisfactory completion-packer fluid is obtained by dissolving CaCl and ZnCl in varying quantities of each, in water. A solution thus formed obviates the many disadvantages of prior art not the least of which are the properties of being stable over exceptionally long periods of time and being noncorrosive to ferrous metals in contact therewith.
FIGURE 1 is a density-phase nomograph of the threecomponent system of this invention to be more fully explained subsequently.
FIGURE 2 is a graphic self-explanatory illustrative comparison of corrosion and density of this system.
FIGURE 3 is a graphic illustrative comparison of corrosion and the pH of a solution containing the components of this invention.
FIGURE 4 is an illustrative schematic drawing of one l embodiment of our article invention as it would appear in finished form for employment of producing fluids from subterranean locations.
The article illustratively shown in FIGURE 4 in more detail comprises a tubular ferrous metal member or casting 1 having a suitable oil well valved production manifold or well completion means '7 commonly referred to as a Christmas tree of the conventional types well known in the art, rigidly secured in conventional manner to the top of said casing. At least one typical production packer and as particularly shown here four typical production packers 2, 3, 4, and 5 are axially spaced and secured substantially fluid tight with respect to and within the casing. In the lower end of the casing below the packers is a mechanically set plug 6 or sealing material such as, for example, cement forming a plug. The article may have more or less than four packers, but there is always at least one fixed therein. Also within said casing 11 is at least one and as particularly shown here are a plurality of four axially aligned concentrically disposed tubular members 8, 9, lltl, and 11 which are secured at the top of the well in normal fashion by tubing hanging means commonly called tubing hangers (not shown). In practice, the number 'of tubes corresponds to the number of packers in the casing. The outer or larger tubing 8 within the casing passes through packer 2, terminating below packer 2 but above packer 3, is secured with the outer wall substantially fluid tight to the first packer 2. T ubings 9, 1b, and ll. are secured to packers 3, 4, and 5, respectively, in like fashion; and said tubings terminate between packers 3 and 4, 4 and 5, and 5 and plug 6, respectively, as shown. The casing below packer 2 and between each pair of packers or plug, beginning with 2, has a series of spaced perforations as indicated by numbers 12, 13, 14, and 15. In practice, the number of series of perforations, packers, and tubing are the same. Tubiugs 8, 9, 10, and 11 are of such comparative diameters that, when arranged as shown, an annular space for fluid flow is provided to the Christmas tree as indicated by their annuli 17, 18, and 19.
The annulus 16 above packer 2, formed by easing 1 and tubing 3, contains a solution comprising CaCl ZnCl and water having a density between about 11.0 and about 17 pounds per gallon. It is usual and preferred that the above-mentioned annulus be fluid filled; however this is not essential or required. The solution is discussed more fully in the later occurring discussion.
As illustrative of the modifications of FIGURE 4 that are possible, it is pointed out that the tubings 8, 9, 10, and 11 could all be of smaller size and individually disposed within the casing not in axially aligned concentric fashion but in a longitudinally aligned relation. The length of the tubes would be the same; however packer 2 would, naturally, have to be a quadruple packer; that is, it would be adapted to provide four separate passages for four tubes. Packer 3 would be a triple packer adapted to provide for the separate passage of three separate tubes therethrough. Packer 4 would be a dual or double packer adapted to provide for the passage of two tubes therethrough, and packer 5 would be a conventional single packer such as the packers employed in FIGURE 4. It follows that a compromise between the embodiment of FIGURE 4 and the above-described embodiment may be readily achieved.
As indicated, the structure can be that employed in a well producing a single zone; thus only one packer, one tubing, and one set of perforations are required in such an embodiment.
Of course, casing 1 and each of tubes 8, 9, 10, and 11 can be made up of jointed sections of pipe and need not be a single continuous section of pipe throughout their entire length.
In practice, the article is employed in producing fluids from subterranean stratum and thus is caused to be vertically disposed in a hole drilled in the earth; and the perforations in the casing are spaced from the Christmas tree to be opposite a formation containing a fluid desired to be produced. A packer would be spaced in the casing to be above said perforations. The particular tubing to produce that Zone would terminate below the corresponding packer but above any packers in a lower spaced relationship as the figure indicates.
The above description with the drawing is merely illustrative and is subject to many modifications and variations as will readily occur to those skilled in the art, as each of the parts, their substitutes, and appropriate equivalents are all individually known in the art. The solution in the upper annulus, however, has no known satisfactory equivalent in the combination.
Although the corrosivity of solutions according to this invention are within the range of permissibility when the salts are employed within certain limits, we nonetheless prefer to use a corrosion inhibitor as an extra-precautionary measure. The types and quantities of inhibitors we contemplate using do not make such extra-precautionary measures economically disadvantageous. The results obtained with inhibitors in fact justify their use, as even corrosion in the permissible range is reduced; and such is always desirable.
The compositions of this invention provide a solution having a density in the range of about 11.0 to about 17 pounds per gallon. It is especially superior for providing a solution having a density in the range of about 11.0 to about 14 pounds per gallon. We have found that solutions containing suflicient ZnCl to obtain densities above about 14 pounds per gallon cause significantly greater corrosion on the ferrous metals in the well. This can best be demonstrated by reference to FIGURES 2 and 3 which show the relationship of density and pH to corrosion rate. The significance of the graph is self-explanatory. Corrosion at these densities can be reduced within safe limits, but in this case the inclusion of a corrosion inhibitor is an exacted requirement.
While densities of fluids in the above specified ranges may be obtained within the wellbore without difliculty, it is better when obtained by the practice of preferred mixing techniques. This simple technique is not a requirement, and the components may be mixed in any order. It consists of first adding and dissolving all the inhibitor and then all the CaCl and finally all the ZnCl Dissolution of the various components will present no problems when used in correct quantities not exceeding the respective solubilities at the existing temperature and thus needs no further comments. It should be pointed out here that there are advantages in using the maximum of CaCl in obtaining the desired density. Less ZnCl is needed whereby corrosivity is less regardless of the actual final permissible rate because ZnCl is the more corrosive (see FIG- URE 2) and economies are achieved due to the fact that CaCl is much cheaper than ZnCl The particular ratios by weight which we have found will give a desired density can be found in the phase nomograph of FIGURE 1. Any combination of ingredients which fall on or above line AA' will produce a single phase solution. Those below line AA' at about 70 F. (i.e., 7015" F.) are never to be used, as this exceeds the solubility of the salts in water and will produce a twophase composition, that is, some solids will be present. The preferred combinations, at about 70 F., are those found approximating the values along line AA', which employs the maximum of CaCl in obtaining a particular desired density. Care should be taken in obtaining desired densities when employing quantities of salts approximating the lines shown on the graph as well as when approaching saturation at any temperature. The special numbered drawn-in lines beginning above AA' which are nearly horizontal beginning at the top and are increasingly inclined moving down are isodensity lines.
As those skilled in the art can appreciate, solubility varies with temperature. The salts of this invention are more soluble at the higher temperatures. Illustratively, line B-B which corresponds to a portion of line AA' indicates how solubility is increased, and the curve correspondingly is shifted downward by an increase in temperature to about 77 F. (i.e., 77.0:.1 F.). Thus line AA' can be shifted downward by an increase in temperature; or it is shifted upwards by a decrease in temperature.
Illustrative but not limiting examples of corrosion inhibitors which may be satisfactorily employed in the practice of this invention are Cronox 840, 1100, and 1110; Rodine 213, 310, and 330; and sodium chromate. Cronox 1100 is a polyoxyethylene glycol ether of Rosin Amine D with 11 moles of ethylene oxide per mole of amine. Rosin Amine D has the formula:
monmo Cronox 1110 has a 10 percent excess of unreacted amine. The Cronox series of inhibitors is available from the Aquaness Department of Atlas Powder. The Rodine series of inhibitors is available from Amchem Products, Inc. Of these illustrated, the preferred is Cronox 1110. There is one restriction on the inhibitor, in addition to being effective against corrosion and inert with regard to the salts, and that is that it must be soluble in the concentrated solution. The inhibitors are used in small but effective amounts which can be as low as 25 parts per million; however we prefer to use and recommend using about 1,000 parts per million, since even at this concentration the quantity is small and constitutes a negligible economic factor. This does not mean that the inhibitor may not be employed in even greater quantities, for indeed it can (e.g., 1.0 percent); however we have observed that the maximum effect, at least for the duration of a short period of time, is had at a concentration below even 1,000 parts per million, namely, at about 500 parts per million. Since we naturally have not had the opportunity to actually test the life of the corrosion inhibitors in these solutions over a period of time of thirty years or longer and although we anticipate no problem with respect thereto, we contemplate testing the solutions actually employed in wells periodically after the lapse of a few years (e. g., two years) and to make any adjustment with regard to the inhibitor as may be deemed appropriate in each particular case. We anticipate that others will also find this convenient, satisfactory, and desirable. We also contemplate a more frequent check to see if the fluid is being lost through bleeding around packers and flowing out with the oil being produced as potentially could happen by reason of the pressure differential previously mentioned. In the case of our fluids, it may be exchanged entirely, if desired, after a period of years with fresh fluid without disadvantages attributable to the fluid.
Of course, those in the art will recognize as with any other completion or packer fluid, the solution in all zones below the first packer in a multiple completion well will be eventually displaced by the formation fluids being produced. This is of no consequence, however. The condition obtained is then as shown in FIGURE 4 of the article with a formation fluid flow through the perforations up through the tubings and the Christmas tree.
Example In the West Delta Area, offshore of Louisiana, a quadruple well was completed using the completion fluid of this invention; and upon completion, the fluid of this invention was employed as a packer or fill-up fluid and remains in that well today.
The operations were performed in conventional manner except as for the use of the fluids of this invention. The pertinent facts relative thereto are as follows: The drilling mud was displaced in the cased well by sea water, and sea water was circulated therethrough for a time to clean the wellbore. The sea water was then displaced with a CaCl -ZnCl l-I O solution prepared by mixing 1,645 sacks of CaCl (100 pounds per sack of 95 percent purity, the 5 percent impurity being water) and H until a density of 11.5 pounds per gallon was obtained (that is, the CaCl was mixed with about 30,000 gallons), then 155 cans (approximately 600-650 pounds/ can of 95 percent purity, the percent impurity being substantially all water) of ZnCl was mixed in whereupon the density was increased to 12.2 pounds/ gallon. The well was perforated a little below 9,300 feet in the presence of the above solution. To consolidate surrounding formation, a squeeze operation was performed using conventional techniques such as displacing the completion fluid in the vicinity of the perforations with diesel oil prior to injecsting the plastic squeeze material. The casing and tubing were then filled with CaCl ZnCl H O solution of 12.2 density until full again. Substantially the same pr cedure was repeated at three more zones between the above level and about 10,000 feet. At one of the intermediate zones, the formation contained water; and this caused the fluid to be diluted, whereupon CaCl and ZnCl were added in a slightly higher CaCl to ZnCl ratio than above until the density was increased back to 12.2 pounds/ gallons. Preceding the final cycle of operations, the density was voluntarily increased by addition of more ZnCl until the density was 12.4 pounds per gallon. Upon completing these operations, the well was filled with CaCl -ZnCl H O solution (12.4 pounds per gallon) and in a manner to displace any residue materials such as diesel oil. The well was put into production by setting packers at appropriate depths, setting the tubing, installing a producing Christmas tree, swabbing and other necessary operations and techniques conventional in the art.
All percent figures employed in this disclosure are percent by weight. In calculating the necessary quantities of salt to obtain a desired density, any addition of salts is best obtained when the quantity of water added as an impurity of the salt is taken into consideration. This is due to the fact that, even though the water in the salt may be only 5 percent or less, its quantity is significant when such large quantities of salt are employed. Of course, it follows that commercial CaCl and ZnCl salts containing more than 5 percent water require a consideration of the water thus added for any desired final density.
While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto, since many modifications may be made; and it is therefore contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.
The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:
1. An article for use in a completion operation on a potentially hydrocarbon producing well comprising a tubular casing member disposed in a well traversing a formation, said casing member having perforations therein opposite said formation, said casing member being sealed at the bottom thereof, said casing member containing a solution consisting essentially of CaCl ZnCl and water having a density of about 11 to about 17 pounds per gallon in contact with the inner wall of said casing member, said solution being retained in said casing member by said formation.
2. An article according to claim 1 being further characterized in that said solution in said casing member additionally contains a small but effective amount of a corrosion inhibitor.
3. An article according to claim 2 wherein said corrosion inhibitor is a polyoxyethylene glycol ether of rosin amine D with 11 moles of ethylene oxide per mole of amine plus a 10% excess of unreacted amine.
4. An article for producing an oil well comprising in combination a first vertical ferrous metal tubular member having a plurality of axially spaced sets of perforations in the lower portion thereof, a valved manifold means, said manifold means secured to the top of said first tubular member, a plurality of annular production packers, said production packers circumferentially secured to the inner wall of said first tubular member in spaced relationship to said manifold means and each other, said first tubular member having said perforations therein axially spaced such that one set of perforations is below each of said production packers, a plurality of smaller tubular members of different lengths disposed within the first tubular member and secured at the top to said manifold means and passing through and also secured at at least one intermediate point to at least one of said production packers, the space within the first tubular member above the first production packer being filled by a solution consisting essentially of calcium chloride, zinc chloride, and water having a density of about 11 to about 17 pounds per gallon.
5. An article according to claim 4 wherein said solution consists esentially of CaCl ZnCI water, and a small but effective amount of a corrosion inhibitor.
6. An article according to claim 5 wherein the small but effective amount of corrosion inhibitor employed is a polyoxyethylene glycol ether of rosin amine D with 11 moles of ethylene oxide per mole of amine plus a 10 percent excess of unreacted amine.
7. An article comprising in combination a first vertical ferrous metal tubular member having perforations in the lower portion thereof, valved manifold means secured to the top of said tubular member, annular production packer means secured to the inner wall of said first tubular member above said perforations, a second substantially axially aligned vertical ferrous metal tubular member of smaller diameter than said first tubular member disposed within said first tubular member, said second tubular member being secured at the top to said manifold means and passing through and secured at an intermediate point by said packer, said article being further characterized in that the annulus above said packer formed by said axially aligned tubular members contains a solution consisting essentially of calcium chloride, zinc chloride, water, and a small but effective amount of corrosion inhibitor, said solution having a density in the range of about 11 to about 17 pounds per gallon.
8. An article according to claim 7 wherein said corrosion inhibitor is a polyoxyethylene glycol ether of rosin amine D with 11 moles of ethylene oxide per mole of amine plus a 10% excess of unreaeted amine.
References Cited in the file of this patent UNITED STATES PATENTS 2,044,758 Cross et a1 June 16, 1936 2,073,413 Cross et al. Mar. 9, 1937 2,649,915 Miller Aug. 25, 1953 2,785,754 True Mar. 19, 1957 2,805,722 Morgan et al. Sept. 10, 1957 2,894,584 Birdwell et a1. July 14, 1959 2,898,294 Priest et al. Aug. 4, 1959 2,905,099 Turner Sept. 22, 1959 3,012,606 Brooke Dec. 12, 1961 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3, 126,950 March 31 1964 Bobbie L, Carlberg et alla It is hereby certifiedv that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 3, line 1, for "c0mparate1y read comparatively column 7, line 20, for "injecstread injectline 25 for "10,000" read 10 100 Signed and sealed this 9th day of February 1965,
EDWARD J. BRENNER Commissioner of Patents ERNEST-T W. SWIDER- Attesting. Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nos 3,126,950 March 31, 19641 Bobbie L, Carlberg et a1,
ror appears in the above numbered pat- It is hereby certified. that er he said Letters Patent should read as ent requiring correctionv and that t corrected below.
Column 3, line 1, for "comparately read comparatively column 7, line 20, for "injecstread injectline 25, for "10,000" read 10, 100
Signed and sealed this 9th day of February 1965.
EDWARD J BRENNER ERNEST W. SWIDER' Attesting Officer Commissioner of Patents