CA1064058A - Cementing in low temperature environments - Google Patents

Abstract

ABSTRACT
A dry cement composition for use in preparing a pumpable slurry capable of setting and developing good compressive strength at low temperatures. The composition includes Portland cement, gypsum cement, calcium chloride as a freezing point depressant, and a setting time retarding agent. Also, a pumpable slurry including components of the foregoing dry composition and water for cementing pipe, such as well casing, in well drilled through low temperature earth formations. Further, a process for cementing such pipe in a well which penetrates a low temperature earth formation involving depositing such slurry in the space between the pipe and the formation, and thereafter allowing the slurry to set. Still further, a process of preparing the foregoing slurry wherein the freezing point depressant and the setting time retarding agent are dissolved in at least a portion of the water for the slurry prior go mixing the water with Portland cement and gypsum cement to form the slurry.

Description

:L~

This invention relates to cementing in low temperature envirOnments More partic~larly the inven-tion is concerned with a dry cement compositi.on Eor use in prepari.ng a pumpable slurry capable of setting and developing good compressive strength at low temperatures. ~he invention is also concerned ~.
with such a pumpable slurry for cementing pipe, such as well casing, in wells drilled through low temperature earth formations, and with a process of cementing pipe in a ~ell that penetxates a low temperature earth formation. Th~ invention further relates to a process of preparing such slurries.

Description of the Prior Art ., ` ' U. S. Patent No. 3,891,454, issued June 24, 1975, entitled "Composition and Method for Cementing Wells in Low Temperature Formations", Cunningham et al, discloses a cement composition for cementing p.ipe in wells drilled in formations existing.at low temperatures, e.g. below 80 F. and as low as 15F.

The cement aomposition of the Cunningham et al ~atent contains Portland cement, sypsum, a monovalent chloride salt, particularly sodium chloride, as a ~reezing point depressant t and a setting ~ime retarding agent.

In one of its aspects, the present invention ` :provides a dry cement composition or use in preparing a ~ pumpable slurry capable of setting and developing good compressive strength at lo~ temperatures consisting ~ essen-tially of:

.'~ .

. ~ .
', ~ ~' ' . .. . : . .... .. . .

(a) Portland cement;
(b) about 100 ~o 400 parts by weight of gypsum cement per 100 parts by weight of Portland cement;
(c) about 5 to 20 parts by weight of calcium chlorlde per 100 parts by weigh~ of Portland cement; and (d) about 0.1 to 1.0 parts by weight of a set~ing tiMe retarding agent per 100 parts by weight of Portland cement;
(e) the cement composition being a palpabl.y dry~ powdery mixture.
In another of its aspects~ the invention provldes a cement slurry composition for cementing pipe in wells drilled through low temperature earth formations consisting essentially : o (a~ Portland cement; (b? about 100 to 400 parts by weight of gypsum cement per 100 parts by weight of said Portland cement; (c) about 5 to 20 parts by weight of calcium chloride per 100 parts by weight of said Portland cemen~; (d) about 0.1 to 1.0 parts by weight of a setting time retarding agent per 100 parts by weight ~ -`~ of said Portland cement; and (e) water in an amount to form a ~ ~ , .~. pumpable slurry capable oE setting and developing good compressi~e strength at low temperatures.
In still another of it5 aspects the present invention :. provides a process for cementing pipe in a well which penetrates .. a low temperature earth formation comprising depositing in the space between sald pipe and ~aid formation a~ aqueous slurry of a hydraulic cement composltlon and thereafter allowing said slurry to set9 wherein said slurry consists essentially of ~a) Portland cement; (b) about 100 to 400 parts by weight of gypsum cement per ~;, ~-~ 100 parts by weight of said Portland cement, (e) about 5 to 20 .
parts by weight of ealcium chloride per 100 parts by weight of aid Portland cement; (d) about 0.1 to 1.0 parts by weigh~ of a settin~ time retarding agent per 100 parts by weight of said Por~land cement; and (e) water in an amount to form a pumpable : slurry capable of setting and developing good compressive strength at low temperatures.
: ,, ~.~
'` ~/r~r~

~`

In yet another of its aspects, -the invention provides a process of preparing a cement slurry composition : for cementing pipe in wells drilled through low tempera-ture ear-th formations which includes:

(a) providing a blend of a PortlancL cement and a gypsum cement ranging from about 100 to 400 parts by weight of gypsum cement to 100 parts by weight of Port:Land cement~

(b~ mixing said blend with water; and ~c~ prior to mixing said blend with water, dissolving in at least a portion of said water about 5 to 20 parts by weight of calcium chloride per 100 parts by weight ., .
of Portland cement and about 0.1 to 1.0 parts by weight of a setting time re-.~ tarding agent per 100 parts by weight of Portland cement;
.
. ,;
~d) the water being in an amount to form a pumpable ~ slurry consisting essentially of the forego.ing - . ~ substances and capable of setting and developing good compressive strength at low temperatures.

,.,: ~ The practice of the last-mentioned process of pre-~ paring a cement slurry composition allows the sacking and ¢.1~ storage of one or a few different standard dry blends of i~ Por-tland cement and gypsum cement. Then, when the slurry ~ -3-~, . , 'i' . ~
' . ' ~` ` " .: ` . " .' ' ' :' ; '. . . . . ' ,: ' , ' ' ' : .`' , ' : ` ' ~

::~a3~

composition is prepared at the well site, the required quantities of calcium chloride and retarder can be added to the mix water to achieve the desired free~ing poin-t and thickening time, as required by conditions in the particular well being cemented.
~oreover, if -the slurry is mixed in a continuous manner as it is pumped into -the casing, substan-tially uniform distribution of the additives is achieved throughout all port:ions of the slurry Such uniformity of distribution of the additives is more di~icult to obtain when the additives are dry-blended with the Portland cement and gyp5um cement before the dry blend is mixed with the water.
: . .
It is advantageous to use calcium chloride in place of sodium chloride as the freezing point depressant.
The compressive strength of the set cement using calcium chloride is oftentimes greater than the compressive strength o a s.et cement using sodium chloride in the slurry, where : the amounts of the respective freezing point depressants are present in proportions that are effective to lower the freezing point of the water to the same temp.erature, and the slurry compositions are otherwise the same.
.. .
;~ The compositions of the present invention include .
~ Portland cement, gypsum cement, calcium chloride, a set-ting :~ time retarder, and water.

.~ The Portland cement employed in the p~actice o : this invention may be one of the Portland cements commonly used in cementing pipe or casing in oil or gas wells. Use-ful, commercially available Portland cements include Class .
A, B, C, G or H, as designated in accordance with the classi-. ication o~ the American Petroleum Institute. See "API

: Specification for Oil-Well Cements and Cement Additives", : .
:

,, , .: : ~ - , - -3~

issued by American Petrolcum Ins-titute, Division of Procluction, 300 Corrigan Tower suilding~ Dallas, Texas 75201, API Spec lOA, 18th ED. January 1974. Other usable Portland cements are Type I, II, III, IV or V of the classification established by The American Society Eor Testing Ma-terials~

The gypsum cement used is the finely ground calcined material, also known as Plaster of Paris or calcined gypsum It approxima-tes in composition the hemihydrate oE
calcium sulphate, CaSO4 . 1/2 ~I2O.

Any good grade of calcium chloride may be employed as the freezing poin-t depressant. Finely ground anhydrous calcium chloride is preferably used in -the dry blended com-positions of the invention. Where the calcium chloride is dissolved in the rnix water prior to mixing the water wi-th the dr~ substances, the equivalent in crys~als of calciu~
chloride may be used.
.
A variety of setting time retarders ar~ available for use in carrying out the invention. Sodium citrate is the preferred setting time retarder. Either the anhydrous sal-t or t~e dihydrate, Na3C~H5O7 . 2H2O, is satisfactory, with t~e former being especially suitable in the dry powder compositions.
The dihydrate, because of its lower cost, is advantageously used in solution in the mix water. Citric acid is also effective as a setting -time retarder, as are also certain sulfonates, such as those referred to in the fore~oing United States patent -5~
, .

-- -.. . - , ~ .

~3~ 9(;1 Water suitable for use :in the invention may be fresh water, such as occurs in rivers, lakes ana ponds. Preferably, the wa-ter should be as pure as possible, and substantially :Eree from suspended or entrained materials The relative quantities oE inyredients that are incorporated in the dry composltions of the inven-tion are based, for convenience of description on lO0 lbs. of Portland cementO
It will be understood that, in practice, these ~uantities will be scaled up or down in accordance with the weight of Portland cement actually employed. From lO0 lbs. to 400 lbs of calcined gypsum are used with each lO0 lbs~ of Portland Cement Calcium chloride in amounts rom about 5 to 20 lbs. is used with each lO0 lbs. of Portland cement About O.l to l.0 lbs~ o~ the set-ting time retarding ayent are employed per lO0 lbs. o Por-tland cement.

In preparing the dry composition, the powdered ingre-dient~ are thoroughly mixed together in a dry materials blender or other suitable dry mixing equipment The resulting mixture may be sacked for delivery to the well site, or may be delivered to the well site in bwlk quantities.

~ t the well site, the cement slurry i5 made up in a conventional cement mixerr either batch or continuous, by mixing the required amount of water with the dry cem~nt composition. The amount of water needed will depend, to a large extent r upon the combined quantities o Portland cement and calcined gypsum in the dry mix. For each lO0 lbs~ combined weight o Portland cement and calcin-ed gypsum, about 5.5 gals .:
:....................................... -6~ ~
.', .

-,~

: . ~

of water are employcd. Over the useful range of Portland cement and calcined gypsum (1:1 to 1:4), the amount of water reguired will vary from about 11 gals. for the 1:1 ra-tio to 28 gals. for the 1:4 ratio Eor each 100 lbs of Por-tl~nd cement in the dry mix-ture.

Alternatively, the cement slurry may be made up by mixing the Portland cement and the gypsum cement, preferably in the form of a dry blend of the two cements, with the re-quired amount of water tha-t contains, in solution, the necessaxy quantities of calcium chloride and setting time retarding agent.
In this way, the dry blend of ingredients may be prepared in advance at a blending plant and transported to the well site.
There, depending upon the temperature and other conditions in the ~ell, the needed amounts of calcium chloride and setting time retarding agent are added to the water for the slurry, and the solution is then mixed with the dry blend to foxm the slurry, In accordance with this method of making the slurry, one or a small number of dry blends containing predetermined propoxtions of cement and calcined gypsum can ~e premixed and held in readiness for use. Then, at the well location, a water solution containing the calculated guantities of water~
calcium chloride and setting time retarding agent is mixed with the required ~uantity of a selected dry blend of Portland and gypsum cements to foxm the cement slurry, which is then pumped into the annulus between the casing and the well bore and allo~ed to set.
' ;~, .

.'. ' ~

;, .. .

Other additives may be incorporated in the cement slurries oE this inven-tion, such, for example, as thickening agents, lost circulation materials, densi:Eiers and -the like, without substantially afEecting the low temperature handling and setting qualities of the slurries.

The .invention finds particular application in cementing casing in permafrost, where the temperatures in the permafros-t may fall as low as about 15F. The slurries of the invention are also employable at higher -temperatures on up to about 60 to 80F. Above these latter temperatures, conventional oil well cements will perform satisfactorily.

The following examples illustrate some of the desirable properties of the cement slurries oE the inven-tion and of the set cemen-t produced therefrom, The basic slurry mixture used in all of the herein~
after-reported runs contains the ingredien-ts in the propor-tions indicated in Table 1.

Ingredient Weight (lbs.) %
Class G Cement 100 38.0 Plaster of Paris 162.9 62.0 Mixing Water: 14.4 gal. (120% by weigh-t of Class G Cemen-tl The densities and yields of the foregoing basic slurry mixture, as affected by variations in the content of calcium chloride, are shown in Table 2.

. , .
, . ~ , ~3~ `3 TABI,F. 2 Anhydrous Calcium Chloride Slurry Yield Tes-t% by weight % by weigh-t of Density Cu Ft, per Noof wa-ter Clo G Cemen-t pcf ppg 100 lb. cement _~

1 0,0 0,0 - 112.6 15~1 3.~0 ~ ~,0 9,6 11~,2 15~3 3.4~
: 3 12,0 14,~ 115,0 15.4 3,~6 ,~
~rom Table 2 it is seen that both the slurry density .:and the yield increase as the percentage of calcium chloride is increased.

The manner in which the consistency of the basic slurry mixture changes with changes in percent of calcium chloride and percent of retarder ~sodium citrate dihydrate) is shown in Table 3.
:~ .
',"
TABL~ 3 ~.
.,' . . "
Anhydrous Calcium Chloride Retarder*
% by % by 50 hy wt. Consistency, Uc, TestWeight of Weiyht of Cl. of Cl, G~
NoO Wa-ter G. Cement Ce~ent 0 min. 5 min, 10 mir 4 0 0 0,3 8 9 10 0 0 0.8 7 7 8 6 8,0 9,6 0.15 8 8 11 . ~ .
``~ i 8 0 0 g,6 0.45 ~ 8 9 . 8 12,0 14.4 0015 9 11 12 ~-` 9 12.0 1~.4 0045 9 9 10 * Sodium citrate dihydrate _9_ '' ' ' ' , The consistency, Uc, report~cl in Table 3, is de-termined in an atmospheric pressure consis-tometer as described in ~ppendix A, API Recommended Practice lOB, 'Nineteen-th Edition.

From Table 3, .it is concluded -that, within the per-centage ranges of anhydrous calcium chloride ancl retarder used, -the consistency of the basic slurry mixture :remains within acceptable limits.

Variations in thickening time of the basic slurry mixture with changes in the percentages of anhydrous calcium 'chloride and retarder are presented in Table 4.

CaC12 Anhydrate Retarder* ~hickening Time Test % by Weigh-t of ~ by''Weight ' (hr:min to 100 Uc~
No. ClG.Cement of Cl, G Cement -20F. 40F. 60 F. 80F.
0 0,3 1:07 0:44 11 0 0.45 1:54 1~12 ~ :
12 0 0.6 3:23 1~41 13 0 : 0.8 3-45 3:03 14 9.6 0.15 1:12 0:~9 0:33 9.6 0.30 2:14 2:30 1:51 , .~.
' ~ i6 9.6 0.45 3~26 4:47 3:40 ~' 17 14.4 0.15 1:20 1:17 1:11 0:47 ~" ~ 18 14.4 0,30' 3:00 2:~7 1:4~ :

~ . 19 14,~ ~ 0,45 5:50 ~:~0 5:10 6:17 '': ~ . ' :
';~' * Sodium citrate dihydrate ~ :
,' ` ' ' 10- `
:1, ;.' ' :

.

~ .

.. ~, . . . .

The thickening times set Eorth in Table 4 were determined accorcling to the l'Arctic Cement.irlCJ Tes-ting Procedure : (~entative)l- as given in Section 11, paye 47, API Recon~ended Practice lOB, Nineteenth Edition. This procedure mentions : th.ickening time tests only at 40F. However, tests can be made at the other temperatures reported in Table 4 (20F, 60F, and 80F~ by maintaining these temperatures in the consistometer in which the tests are made.

From Table 4 it appears that slurry mixtures can be selected that have adequate thickening time for cementing wells : having temperatures from 20F to 800F.

.~ Variations in compressive strength o~ set cements ~, yielded by the basic slurry mixture when cured for 8, 16 ~` and 24 hours at different temperatures, and with variations in the percentages of anhydrous calcium chloride and sodium . citrate dihydrate, are tabulated in Table 5.
,~`' ' ' ' .. . ..
.

'' , ~ .. . . .

: .
.,~ :
:,':: , :
`;1 . - ' :
.;i :
:! :
'~:

', , :

:j .
, .
: :
- , . . .

.,' . : , T~BLE 5 CaC12 ~nhyd. Retarder* Cure Compressive Strength Test % by Weight % by Wëight Time PSi No. of Cl. G Cement of Cl. G Cement Hrs, 20F 30~F 40F 80F
0 0.30 8 940 87~
21 0 0.30 16 968 12~3 22 0 0.30 24 793 1435 23 0 0.45 8 906 695 24 0 0,45 16 ~90 955 Q 0.45 24 97~ 1235 26 0 0,60 8 823 6~0 27 0 0.60 16 975 935 28 0 0.60 24 1001 1184 29 9.6 0.15 8 843 835 9.6 0.15 16 779 856 31 9.6 0~15 24 933 984 :
32 ~.6 0.30 8 590 505 33 9.6 0.30 16 566 588 34 9.6 0.30 24 860 619 9.6 0.45 8 ~ 553 ~38 36 9.6 0~45 16 54~ ~50 37 9~6 0.45 2~ 680 ~ 525 ,:
~ 38 14.4 0~15 8 681 863 860 : ~ .
39 14~4 0.15 161010 12151338 ; 40 14.4 0.15 2~1328 13501428 . .
14.40.30 8 496 6Q5 483 4274.4 - 0.30 16 680 805 763 4314.4 0~3Q 24 934 990 1041 : :
44 14.4 0.45 8 4~1 345 363 ~5 1~.4 0.45 16 638 500 478 46 1~4 0.45 24 70~ 635 78Q

* Sodium citrate dihydrate -12-.
. . : - . , - : - - .
. . : : :: -The compressive strength values given in Table 5 were determined according to the "~rctic Cementing Testing Procedure (Tentative~" previously mentioned, except that the compositions were not s-tirred ("pumped") for 1 1/2 hou:rs be~ore they were pou,red into molds for curing. This procedure mentions curing temperatures o:E 20F and ~0F only but a similar procedure can be used for the other temperatures reported in Table 5.

Compressive strengths oE about 500 psi or higher are acceptable. These strengths are reached after eiyht hours of curing in all tests but No. 49. The latter is up -to minimu:m desired strength af-ter 16 hours curing time.

From Table 5, it appears that increasing the calcium chloride content of the slurry either increases compressive strength or does not substantially change it when the same percentage of retarder is used. It also appears that increasing the retarder content tends to decrease compressive strength.
In general r the lower the curing temperature the lower is the compressive strength of the cured cement. Compressive strength is also seen to increase with increased curing times up to t~enty-four hours.

From the :Eoregoing description it is seen that the invention provides cement compositions and slurries suitable for use in low temperature environments, such as in permafrost, as well as an improved me-thod oE preparing the cement slurries.

. .

.
' :~

.

Claims (17)

1. A cement composition for use in preparing a pumpable slurry capable of setting and developing good compressive strength at low temperatures consisting essentially of:

(a) Portland cement;

(b) about 100 to 400 parts by weight of gypsum cement per 100 parts by weight of Portland cement;

(c) about 5 to 20 parts by weight of calcium chloride per 100 parts by weight of said Portland cement; and (d) about 0.1 to 1.0 parts by weight of a setting time retarding agent per 100 parts by weight of said Portland cement;
(e) the cement composition being a palpably dry, powdery mixture.

2, A composition as defined in Claim 1, wherein 9.6 to 14.4 parts by weight of calcium chloride are present per 100 parts by weight of said Portland cement.

3. A composition as defined in Claim 1, wherein 0.3 to 0.45 parts by weight of a setting time retarding agent are present per 100 parts by weight of said Portland cement.

4. A composition as defined in Claim 1, wherein said setting time retarding agent is sodium citrate,

5. A cement slurry composition for cementing pipe in wells drilled through low temperature earth formations consisting essentially of:

(a) Portland cement;

(b) about 100 to 400 parts by weight of gypsum cement per 100 parts by weight of said Portland cement;

(c) about 5 to 20 parts by weight of calcium chloride per 100 parts by weight of said Portland cement;

(d) about 0.1 to 1.0 parts by weight of a setting time retarding agent per 100 parts by weight of said Portland cement; and (e) water in an amount to form a pumpable slurry capable of setting and developing good compressive strength at low temperatures,

6. A composition as defined in Claim 5, wherein 9.6 to 14.4 parts by weight of calcium chloride are present per 100 parts by weight of said Portland cement.

7. A composition as defined in Claim 5, wherein 0.3 to 0.45 parts by weight of a setting time retarding agent are present per 100 parts by weight of said Portland cement.

8. A composition as defined in Claim 5, wherein said setting time retarding agent is sodium citrate.

9. A process for cementing pipe in a well which penetrates a low temperature earth formation comprising de-positing in the space between said pipe and said formation an aqueous slurry of a hydraulic cement composition and there-after allowing said slurry to set, wherein said slurry con-sists essentially of:

(a) Portland cement;

(b) about 100 to 400 parts by weight of gypsum cement per 100 parts by weight of said Portland cement;

(c) about 5 to 20 parts by weight of calcium chloride per 100 parts by weight of said Portland cement;

(d) about 0.1 to 100 parts by weight of a setting time retarding agent per 100 parts by weight of said Portland cement; and (e) water in an amount to form a pumpable slurry capable of setting and developing good compressive strength at low temperatures.

10, A process as defined in Claim 9, wherein 9.6 to 14.4 parts by weight of calcium chloride are present per 100 parts by weight of said Portland cement.

11. A process as defined in Claim 9, wherein 0.3 to 0.45 parts by weight of a setting time retarding agent are present per 100 parts of said Portland cement.

12. A process as defined in Claim 9, wherein said setting time retarding agent is sodium citrate,

13. A process of preparing a cement slurry composition for cementing pipe in wells drilled through low temperature earth formations which comprises:

(a) providing a blend of a Portland cement and a gypsum cement ranging from about 100 to 400 parts by weight of gypsum cement to 100 parts by weight of Portland cement;

(b) mixing said blend of cements with water;
and (c) prior to mixing said blend of cements with water, dissolving in at least a portion of said water about 5 to 20 parts by weight of calcium chloride per 100 parts by weight of said Portland cement and about 0.1 to 1.0 parts by weight of a setting time retarding agent per 100 parts by weight of said Portland cement;

(d) said water being in an amount to form a pumpable slurry consisting essentially of the foregoing substances and capable of setting and developing good compressive strength at low temperatures.

14. A process as defined in Claim 13, wherein 9.6 to 14.4 parts by weight of calcium chloride are present per 100 parts by weight of said Portland cement.

15. A process as defined in Claim 13, wherein 0.3 to 0.45 parts by weight of a setting time retarding agent are present per 100 parts by weight of said Portland cement.

16. A process as defined in Claim 13, wherein said setting time retarding agent is sodium citrate,

17. A process as defined in Claim 13, wherein said blend of a Portland cement and a gypsum cement is in the form of a dry blend.