USRE23873E - Retarded cement - Google Patents

Description

Reissued Sept. 21, 1954 UNITED STATES PATENT OFFICE RETARDED CEMENT Norman C. Ludwig, Chicago, 111., assignor to Universal Atlas Cement Company, a corporation of Indiana.

No Drawing. Original No. 2,427,683, dated September 23, 1947, Serial No. 664,985, April 25,

1948, Serial No. 48,750

Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

7 Claims.

This invention relates to cements having retarded rates of hydration or set, to slurries of such cement, and to the method of making these slurries. The cement with which the invention is concerned is a Portland or Portland-type cement.

Among the objects of the invention is the provision of a cement having a retarded rate of hydration, or a retarded set as it will be hereinafter termed, particularly at elevated temperatures such as are encountered in the cementing of deep wells.

Further objects of the invention reside in the provision of a slurry of the above cement, and in a method of making such slurry.

These and further objects of the invention will be more readily apparent in the following description.

In the cementing of oil wells it is customary to mix a hydraulic cement, for example a Portland or Portland-type cement, with the requisite amount of water to form a pumpable neat slurry, and to pump the mixture into the well and down the hole into the place where it is desired to have it harden. In present oil Well drilling practice, with wells commonly ranging from 6,000 to 12,000 feet or more in depth, high temperatures are encountered at the locations which are to be cemented, and relatively long periods of time are often required to pump the slurry into place. Furthermore, in the customary practice of pumping the cement slurry down through the casing and either forcing it upward around the outer surface of the casing or through perforations in the lower end of the casing into the formation sought to be sealed, the slurry is required to pass through narrow channels and small openings. Successful placement of the slurry, therefore, requires that the slurry shall remain fluid and pumpable at high temeratures for several hours before it begins to harden. However, after the slurry has been pumped into place, it is desirable to have the hydration or set proceed at a rate at which the slurry will attain its final set and develop considerable strength within about 24 hours.

It has been found that Portland and Portlandtype cement slurries can be retarded so that they meet all the above requirements for the satisfactory cementing of deep wells and like operations by the addition of carboxymethylcellulose (CMC) and salts of carboxymethylcellulose within certain definite limitations. More specifically, the cement and slurry of the present invention contain at least one of the group consisting of car- Application for reissue September 10,

boxymethylcellulose and salts of carboxymethylcellulose within the range of from .05 to 35% by weight of the dry cement. Ordinarily, it is preferred to use carboxymethylcellulose and salts of carboxymethylcellulose, either alone or in combination, so that the total of such additive lies within the range of from .05 to .64% by weight of the dry cement. It has been found that when used in hydraulic cement slurries in the above indicated amounts, carboxymethylcellulose and salts of carboxymethylcellulose act as retarders at elevated temperaures, the retarding effects becoming marked at F. and continuing 11p to 220 F. and above. It has been found that carboxymethylcellulose and its salts are most effective as retarders in the higher temperature range of from 180 to 220 F. and above.

Carboxymethylcellulose, which is sold commercially in powder form, is a glycolic acid ether of cellulose. Carboxymethylcellulose is sometimes also termed celluloseglycolic acid. It may be made by the reaction of monochloracetic acid upon alkali cellulose, the reaction yielding the alkali chloride and carboxymethylcellulose, which is representable by the formula:

Carboxymethylcellulose lends itself readily to salt formation with alkali metals as well as with various other metals. The sodium salt of carboxymethylcellulose, which is readily available commercially and for this reason ordinarily to be preferred in the practice of this invention, is a white, granular, colorless powder readily soluble or dispersible in water or alkaline solutions. It is to be understood, however, that other salts of carboxymethylcellulose may be employed in the practice of this invention, such salts including the alkali metal salts and the ammonium salt of carboxymethylcellulose, all of which are soluble in water, and other metal salts of carboxymethylcellulose such as the aluminum, iron, copper, lead, silver, mercury, nickel, and zinc salts, all of which are insoluble in water but which hydrolyze in alkaline solutions. The salts of carboxymethylcellulose may be prepared by either treating carboxymethylcellulose with a base containing the desired metal or by treating the sodium salt of carboxymethylcellulose in solution with a salt, such as the chloride of the desired metal, so that replacement occurs.

The cement employed may be any Portland or Portland-type hydraulic cement, the particular type used depending upon the particular application to be made of the cement or of the slurry,

and of the properties demanded by such application, such .asL-Bettingtime, strength of the: set slurry, and so forth. In making the test specimens of the cements within the invention, the results of tests on which are set forth below, cements of both the A. S. T. M. Type I and Type II, Portland type, were employed as indicated. The oxide composition of such cements and the specific surface as determined by the Wagner turbidimetric method are given below:

OXIDE COMPOSITIONPER CENT into the cylinder entirely surrounding the cell. At 220F'. it was necessary to subject the slurry to but from two to five pounds per square inch by means of the oil acting through the medium of the neoprene diaphragm interposed between the slurry and the oil. The apparatus works on the same principle as does the Halliburton Consistometer', but the standard method for operation of the pressure consistometer, which method was employed in the present tests, specifies a Loss on .Spec. Sur. Cement S102 A1203 F9203 OaO MgO MnO S05 Ignition SWagner, q. cm./g.

TypeII..- 22. 1 4. 8 4. 3 64. 2 0.88 0; 1. 70 l. 20 l, 175 Type I 21.8 G. 0 2. 6 65. 0 1. 1, 0. l6 1. 70 1. 20 1,800

Inthe-tests of cements in accordance with the invention neat slurries containing the indicated type; of cement, water, and the indicated additive were made up, there being used in each case 100 parts by weightof the cement and 40 parts by weight of water. This gave a slurry which was typical of those employed in oil well cementing operations. The tests included the determination ofthe stiffening time of slurries at temperatures of 140, 180, 200 and 220 F., the determination of the consistency of the slurries at intervalswhile stirring, and the determination of compressive strengths of the set and cured cement structure resulting from such slurries.

The stiffening times and the consistencies of the slurries when at temperatures of 140, 180, and 200 F. were determined by use of an apparatus such as shown in Weller Patent No. 2,122,765, dated July 5, 1938, which is known as the "Halliburton Consistometer, and is designed to test stirring or pumpability time of cement slurries at high temperatures. Such device consists essentially of a rotating cylindrical container with an internal paddle assembly fixed to a head whose movementis independent of the container. With the container filled with cement slurry, the force against the paddle due to rotation of the container and the viscosity of the slurry is transferredfrom' the head of the apparatusto a pendulum lever arm by a suitable connection, The pendulum. range is graduated from 01 to 10 divisions, represnting slurry viscosities of 0 to 100 poises, a. pull of 10 divisions on the pendulum is considered to represent the limit of pumpability of the slurry in an oil well. The temperature of the slurry during the test was maintained at the degree indicated by a thermostatically controlled bath surrounding the container. In the following tables stiffening time was taken as the time from initiation of the test in the consistometer until the indicator on the pendulum showed a slurry viscosity of 100 poises.

The determination of the stiffening time of slurries at a temperature of 220 F. was carried out by use ofv a pressure consistometer such as described in Technical Publication No. 1207 of the American Institute of Mining and Metallurgical Engineers. Such tests were conducted under pressure small enough so that they had little effect on the stiffening times and were sufficient only to prohibit the evaporation of water from the slurry at the constant temperature of 220 F., which, of course, is above the boiling point of water. In such pressure consistometer the cell which contains the slurry is placed in a heated pressure; cylinder and petroleum oil is pumped shearing rate of 47 R. P. M. and viscosity of poises for termination of the test, such shearing rate being about twice that employed in the l-Ialliburton Consistometer which as above pointed out, employs a viscosity of poises for termination of the tests therein. At temperatures of 200 F. and lower, final stiffening times on the same slurries in the Halliburton Consistometer and the pressure consistometer check very closely.

The compressive strengths reported in the tables below were determined by making two-inch cubes which were molded from portions of the various cement slurries. When the molds were filled they were covered with metal plates and placed in the water or temperature baths operating at and 200 F, as indicated. At approximately 20 hours the specimens were removed from the molds and returned to. the temperature baths. Three cubes of each slurry were broken at 24 hours and three days by subjecting them to compression to destruction in a standard compression testing machine.

Carboxymethylcellulose and its salts can be added to the dry cement in powder form and intermixed therewith before the addition of water to form the slurry, or they can be added to the cement slurry in solution. The more practical method, from a commercial standpoint, is to employ carboxymethylcellulose or its water soluble salts and to add the material to the dry cement. In the tests reported in the tables below this was the method of addition employed, except where otherwise noted.

In cement slurries, especially when the slurries are mixed rapidly and consequently with high agitation, carboxymethylcellulose and its salts act as foam stabilizing agents and cause the entrainment of a considerable amount of air. In the usual methods of preparing slurries for use in oil wells, therefore, the addition of carboxymethylcellulose and its salts may cause foaming and frothing of the slurry, which is generally considered undesirable in oil well cementing operations. Such foaming and frothing of the slurry containing carboxymethylcellulose and its salts can be nullified by the use of defoaming agents, such as tributyl phosphate and pine oil. Such defoaming agents, when used, are added in small amounts, from .02 to 05% tributyl phosphate being typical, sufficient to suppress the foaming and frothing tendencies of carbo'xymethylcellulose and its salts on the slurry in the particular slurry mixing and pumping conditions employed. In each of the slurries tested which contained carboxymethylcellulose and its salts, .02% tributyl phosphate was added.

In the tables below carboxymethylcellulose is abbreviated CMC and the salts of carboxymethylcellulose are abbreviated with the symbol of the metal, or of the ammonium radical, as

, 6 cement, respectively, with no carboxymethylcellulose or salt of carboxymethylcellulose added hydrated at such rates that slurry 1 had stiffened sufiiciently so that it had a consistency of 100 the case may be, prefixed to CMC. 5 poises at 1 hour and 29 minutes, and that slurry TABLE I stiffening time at constant temperature Stlflening Times at Temperatures Indicated Cement Additive, percent 140 F. 180 F. 200 F. 220 F.

Hr Min Hr. Min. Hr. Min. Hr. Min.

1 a 46 1 47 1 2e 1 11 2 3 33 2 5s 5 37 a9 3 2 9 1 12 o 42 o 32 4 2 53 3 3s 5 21 6 5s The stiffening time results given in Table I show that the sodium salt of carboxymethylcellulose, which, as will appear, is typical of carboxymethylcellulose and its other salts, is considerably more elfective as a retarder at temperatures of 200 and 220 F. than at temperatures of 140 and 180 F. For some purposes, the relatively short stiffening times of slurries 2 and 4 at temperatures of 140 and 180 F., which are in general not markedly longer than those of slurries 1 and 3 at such temperatures, would not be particularly useful. Consequently, when the slurry is to be used at such lower temperatures, and particularly when carboxymethylcellulose and its salts form the sole retarding additive, it is necessary to use larger amounts of carboxymethylcellulose and its salts, if the stifiening time is to besubstantially prolonged. Examples of slurries containing sufiicient sodium salt of carboxymethylcellulose to retard it to a marked degree are given in the As pointed out above, it is desirable in oil well cementing and like operations that the slurry remain easily pumpable over extended periods of time, even though it is subjected to high temperatures. The following Table 111 gives the results of slurry consistency tests run in the Halliburton Consistometer at a temperature of 200 F.

TABLE III 3 had stiffened sufficiently so that it had a slurry consistency of poises at 42 minutes, thus showing that they were unfit for deep well cementing operations at 200 F. With both slurries 2 and 4, however, a consistency far below 100 poises was maintained throughout the entire period from the time of mixing to four hours after mixing, showing that such slurries remained pumpable for times which were adequate for cementing even the deepest wells.

The presence of carboxymethylcellul ose and of the salts of carboxymethylcellulose in the slurries in amounts taught by the invention does not in the main adversely afiect the strength of the cured cement structure resulting from the slurry when such cement structures are cured for three days either at or 200 F. Furthermore, when cured for only 24 hours the strengths of the cement structures containing the additives are not markedly below those not containing the additives, showing that the structures resulting from the cements of the present invention develop an early strength fully adequate for the purpose in hand. The compressive strengths given in Table IV are the average values for three 2-inch cubes cured and tested as set out above.

Slurry consistency at 200 F.

Consistency in Poises at Times Indicated Stifiening Time Cement Additive, percent 3 1 hr. 2 hr. 3 hr. 4 hr. Hr. Min.

1 None 14 19 20 1 29 2 NaCMC 0.16. 14 ll 10 9 9 l0 5 37 3 None 20 33 0 42 4 Na-CMO 0.24 l4 l2 l1 l3 l3 l4 5 21 It may be seen from the above table that slurries 1 and 3 made with Type II and Type I In order to illustrate the use of various other salts of carboxymethylcellulose as set forth in the invention, as well as carboxymethylcellulose. itself, and to show the various manners in which theadditions may be made to the cement or slurry, there were made additional tests of stifiening: times of 200 F. employing as additives,

sodium, potassium, ammonium, aluminum, copper, and iron salts of carboxymethylcellulose, and

carboxymethylcellulose itself. As before, the cement and water employed were in the ratio of 100 to 40 by weight. Under Additive, percent, in Table V below, the additives denoted (powder) were added to the dry cement whereas those denoted (solution) were added to the slurries in the manner indicated by the notes below the table.

TABLE V stiffening Time Cement Additive, Percent Hr. Min.

. None N a(JMO-0.l6 (powder) OMC-0.15 (powder) CMO-0.30 (powder) K-CMC-0.075 (solution) KOMC0.15 (solution) NH4-GMC0.15 (solution) N Hi-CMC-OBO (solution) 1 Al-CMO0.15 (powder).-.. A1CMO-0.30 (powder).... Ou-CMO0.50 (powder). CuGMC0.75 (powder)- Fe-CMO0.50 (powder). FeCMG-0.75 (powder)..-.

200 g. water+1.29 g, KOH+4 g. CMO. 200 g; water+3 ml. 28% NH4OH+4 g. OMO.

The stiffening times at 200 IF. given in Table V show that the water soluble salts of carboxymethylcellulose, that is, sodium, potassium, and ammonium salts, as Well as carboxymethylcellulose 8*. to by weight of the dry cement, is an 'effective retarder for hydraulic cement slurries, particularly within the temperature range 140 to 180 F. It has been found that hydroxyethylcellulose and carboxymethylcellulose and. its salts do not adversely aifect each other when both are present in a slurry but, on the contrary, that each supplements the action of the other. As a consequence, a cement slurry containing carboxy--- methylcellulose and salts of carboxymethylcellulose in amounts within the present invention and hydroxyethylcellulose from 05m .60%, preferably .05 to 50%, by weight of the dry cement, will be effectively retarded in its setting time over a temperature range from 140 to- 220 F. and above.

It will be obvious that for each chosen percentage within the invention of the additiveconsisting of at least one of the group consisting ofv carboxymethylcellulose and salts of carboxymethylcellulose there will be .a corresponding percentage of hydroxyethylcellulose which when added to the slurry will produce a slurry having a substantially constant stiffening time over the entire temperature range of 140 to 220 F. and above. As specific examples of such slurry having substantially constant stiffening times over such temperature range, there are set out in Table VI below two slurries, Nos. 2 and 3, containing both hydroxyethylcellulose and, a sodium. salt of carboxymethylcellulose, the quantities of the two additives being so adjusted as to give the slurry a substantially constant stiffening time. It is to be understood that such examples are illustrative only, and that numerous variations are possible. In each of the slurries set out in Tables VI and VII 100 parts by weight of the cement and 40 parts by weight of Water were employed.

TABLE VI Stifiening time at constant temperature itself, which is also water soluble, are considerably more effective retarders than are the water insoluble salts. The mechanism of retarding the hydration of cements is not fully understood, and so it is not desired that the invention be confined to a particular theory of operation. It is believed, however, that the water insoluble salts of carboxymethylcellulose hydrolyze in alkaline solutions such as are formed when the cement is mixed with water. Such hydrolysis is believed to proceed to such an extent that a portion of the water insoluble metal salt of carboxymethylcellulose is free to produce the same retardation in the cement as, but to a. somewhat more limited degree than, that of the water soluble salts.

As set out in application Serial No. 664,984 filed of even date, it has been found that hydroxyethylcellulose as an additive within the range .05 to .60%, and preferably within the range .05

It will be seen that slurries 2 and 3 have stifiening times particularly from to 200 F; which: are substantially constant. The temperature range over which the slurry has a substantially constant stiffening time may be extended to 220 F. and above. This is illustrated by slurry 3, in which the ratio of the weights of hydro-xyethylcellulose and sodium salt of carboxymethylcellulose are somewhat different from that employed in slurry 2.

The presence in the slurry of both hydroxyethylcellulose and carboxymethylcellulose or its salts displays an additional advantage in that the strength of the cement structure resulting from. the slurry containing both. additives is markedly increased. Such increased strength is obtained both when such structure is cured at 140 and when it is cured at 200 F., as illustrated by the following table.

[2. A cement capable of forming a fluid slurry when mixed with water, said cement having a. retarded set at temperatures above atmospheric, said cement comprising Portland cement mixed with a minor proportion of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellul'ose.]

[3. A cement capable of forming a fluid slurry when mixed with water, said cement having a retarded set at temperatures above atmospheric, said cement comprising a hydraulic cement mixed with from .05 to 375% by weight of the dry cement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose] [4. A cement capable of forming a fluid slurry when mixed with. water, said cement having a retarded set at temperatures above atmospheric,

' said cement comprising Portland cement mixed with from .05 to 375% by weight of the dry cement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcelluloseji [5. A cement capable of forming a fluid slurry when mixed with water, said cement having a retarded set at temperatures above atmospheric, said cement comprising Portland cement mixed with from .05 to 54% by weight of the dry cement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose] [6. A hydraulic cement slurry having a retarded setting time at temperatures above atmospheric, comprising a hydraulic cement, water, and a minor proportion of at least one of the group consisting of carboxymethylcellulose and salts oi carboxymethylcellulose] [7. A hydraulic cement slurry having a retarded setting time at temperatures above atmospheric, comprising Portland cement, water, and a minor proportion of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose] [8. A hydraulic cement slurry having a retarded setting time at temperatures above atmospheric, comprising Portland cement, water, and from .05 to 75% by weight of the dry cement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose] [9. A hydraulic cement slurry having a retarded setting time at temperatures above atmospheric, comprising Portland cement, water, and from .05 to .64% by weight of the dry cement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose] [10. A hydraulic cement slurry adapted to be used in well cementing operations and having a retarded setting time at temperatures above atmospheric, consisting essentially of Portland cement, water in a quantity sufiicient to render the slurry pumpable, and from .05 to 1 4% by weight of the dry cement of the sodium salt of carboxymethylcellulose] [11. A method of forming fluid hydraulic cement slurries adapted to be used in well cementing operations and having a retarded setting time at temperatures above atmospheric, which comprises the steps of forming a hydraulic cement slurry containing a minor proportion of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, the remainder of said slurry consisting essentially of hydraulic cement and water.]

[12. A method of forming fluid hydraulic cement slurries adapted to be used in well cementing operations and having a retarded setting time at temperatures above atmospheric, which comprises the steps of forming a hydraulic cement slurry containing from .05 to by weight of the dry cement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, the remainder of said slurry consisting essentially of Portland cement and water.]

[13. A method of forming fluid hydraulic cement slurries adapted to be used in well cementing operations and having a retarded setting time at temperatures above atmospheric, which comprises the steps of forming a hydraulic cement slurry containing from .05 to 54% by weight of the dry cement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, the remainder of said slurry consisting essentially of Portland cement and water.]

14. A cement capable of forming a fluid slurry when mixed with water. said cement having a retarded set at temperatures above atmospheric, said cement comprising a hydraulic cement mixed with a minor proportion of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, and with a minor proportion of hydroxyethylcellulose.

15. A cement capable of forming a fluid slurry when mixed with water, said cement having a retarded set of temperatures above atmospheric, said cement comprising a Portland cement mixed "1:1 with a minor proportion of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, and with a minor proportion of hydroxyethylcellulose.

16. A cement capable of forming a fiuid'slurry when mixed with water, said cement having a retarded set at temperatures above atmospheric, said cement comprising Portland cement mixed with from .05 to .75% by weight of thedr-ycement of at least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, and with from .05 to 5 hydroxyethylcellulose by weight of the drycement.

17. A cement capable of forming a fluid-slurry when mixed with Water, said cement having a retarded set at temperatures above atmospheric, said cement comprising Portland cement mixed with from to 54% of the sodium salt of carboxymethylcellulose by weight of the dry cement, and with from .05 to 50% hydroxyethylcellulose by weight of the dry cement.

18. A hydraulic cement slurry adapted to be used in well cementing operations and having a retarded setting time'at temperatures above atmospheric, consisting essentially of Portland cement, water in a quantity sufiicient to render the slurry pumpable, and from .05 to .75% by weight of the dry cement ofat least one of the group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, and from .05 to 50% hydroxyethylcellulose by weight of the dry cement.

19. A hydraulic cement slurry adapted to be used in well cementing operations and having a retarded setting time at temperatures above atmospheric, consisting essentially ofPortland cement, water mvar q uantity sufilcient to render the slurrytpumpable, and from .05 to 154% by weight of the 'dry' cementof at leastone of-"thagroup consisting of carboxymethylcellulose and-saltsof carboxymethvlcellulose, and from .05 to .50%

hydroxyethylcellulose by Weight of the dry :ce-

.ment.

20.A hydraulic cement slurry adapted to be usedin well cementing operationsaand having a retarded setting time at temperatures above;at-

-mospheric, consisting essentially of -Portland :ce-

ment, water in a quantity sufficient to render the slurr pumpable, and from '.05 to 4% -by weight of the-drycementof atleast one-of the'group consisting of carboxymethylcellulose and salts of carboxymethylcellulose, and from .05 to hydroxyethylcellulose by weightof the dry cement, the hydroxyethylcellulose content being ;.so aidjusted relative to the content of the group con- References-Cited in the fileof this patent or theioriginal patent UNITED STATES PATENTS Number Name Date 2290;956 Gruenwald .July.'28, 1942 2,476,306 :King vJuly 19, 1 9,49 v2,655,004 Wertz i v .Oct. 13, 1953