CA1077970A - Hydrothermal cement - Google Patents
Hydrothermal cementInfo
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- CA1077970A CA1077970A CA259,372A CA259372A CA1077970A CA 1077970 A CA1077970 A CA 1077970A CA 259372 A CA259372 A CA 259372A CA 1077970 A CA1077970 A CA 1077970A
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Abstract
ABSTRACT
A hydrothermal cement composition consisting essentially of (a) a polyvalent metal ion source, (b) water, and (c) a hydratable silica source wherein the silica becomes available for chemical combination with the polyvalent metal salt upon application of heat. A method of cementing a string of pipe in a bore hole including the steps of preparing such a cement composition, pumping the cement composition into the annular space between the string of pipe and the walls of the bore hole, and allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
A hydrothermal cement composition consisting essentially of (a) a polyvalent metal ion source, (b) water, and (c) a hydratable silica source wherein the silica becomes available for chemical combination with the polyvalent metal salt upon application of heat. A method of cementing a string of pipe in a bore hole including the steps of preparing such a cement composition, pumping the cement composition into the annular space between the string of pipe and the walls of the bore hole, and allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
Description
1~77970 Portland cement is prepared conventionally by ~rinding limes~one and cla~ and/or other materials to a :Fine powder, mixing thorou~hly, and burning the mixture .in a long rotary ~iln. At the hot zone of the kiln, where the temperature approaches 3000 F~, the mixture is sintered and fused together into nodules called "clin~er' which i6 ground to a fine powder. Substant~al ~uel is required to serve the energy demand for this low cost~
h~gh volume conventional cement material, and, as in all energy consuming industr~es, ~uel shortages curtail cement production. Hence~ a need exists for low energy consuming cements in building materials~
The possibility of fossil fuel shortages and accompany-ing demand for high energy fuels has spurred efforts to recover geothermal energy as well as petroleum gas deposits trapped in Yery deep cavities and to liberate these reserves.
Nuclear devices have been proposed as fracturing methods to stimulate product~o~ of high yields. However, the comb~nation of inherently high Gubterranean tempera~ure and the added thermal in~lux ~rom nuclear stimulation poses a serious threat to the stability of cements used to reinforce the casing and wall~ of the wells an~ to secure the caslng~
to wells in desired configurations ~or attachment to above-ground piping and valve assemblies. The high temperature qradients that define the thermal profile of these wells constitute a source of variable stre6s between cement and steel casing. The high coefficient of thermal expansion of metal compared to concrete (in the range of 5-50 to 1) can induce adhesive failure if the cement bond is not satisfactory. Conventional Portland cements rapidly lose
h~gh volume conventional cement material, and, as in all energy consuming industr~es, ~uel shortages curtail cement production. Hence~ a need exists for low energy consuming cements in building materials~
The possibility of fossil fuel shortages and accompany-ing demand for high energy fuels has spurred efforts to recover geothermal energy as well as petroleum gas deposits trapped in Yery deep cavities and to liberate these reserves.
Nuclear devices have been proposed as fracturing methods to stimulate product~o~ of high yields. However, the comb~nation of inherently high Gubterranean tempera~ure and the added thermal in~lux ~rom nuclear stimulation poses a serious threat to the stability of cements used to reinforce the casing and wall~ of the wells an~ to secure the caslng~
to wells in desired configurations ~or attachment to above-ground piping and valve assemblies. The high temperature qradients that define the thermal profile of these wells constitute a source of variable stre6s between cement and steel casing. The high coefficient of thermal expansion of metal compared to concrete (in the range of 5-50 to 1) can induce adhesive failure if the cement bond is not satisfactory. Conventional Portland cements rapidly lose
- 2 -` ~
1~77!~70 adhesive strength at elevated temperatures ti.e., 300 F.
and higher) and possess only mar~inal strength under optimum temperature conditions. For example, the shear boAd of Portland cement to "Re Bar~ (conventional steel reinforcing rods) averages 50Q psi while the shear bond of Portland cements to conventional polished steel is only 50 psi. The added stress of thermal degradation would render a Portland cement useless in regard to adhesion in wells of the nature described above. Consequently, the need exists for a high strength cement exh~biting high shear bond and adhesion properties for the uses described.
In the drilling of conventional oil and gas wells, casing is cemented not only to secure the casing in the ; bore hole but also to prevent communication between water, oil and ~as-producing zones within the well. The typical procedure for cementing wells o this nature involves mixin~
Portland cement compositions at the well site and pumping the cement downwardly through casing and then outwardly and upward through a well between the casing and the wall of the bore hole. Ordinarily, a plurality of high pressure pumps and piping systems are required to guard against pump fallure. In the event o~ pump failure, the cement sets almost immediately and hardens, thereafter requiring expensi~e drillin~ operations to sal~age the well. Thus, it would be advantageous to provide a method of cementing a string o~ pipe in a bore hole ~hereby the cement will not set, harden or cure except by passage of time or ~y exposure of the cement to given temperature conditions that exist within the well or both. The present invention is directed to such method which eliminates the necessity of equipping
1~77!~70 adhesive strength at elevated temperatures ti.e., 300 F.
and higher) and possess only mar~inal strength under optimum temperature conditions. For example, the shear boAd of Portland cement to "Re Bar~ (conventional steel reinforcing rods) averages 50Q psi while the shear bond of Portland cements to conventional polished steel is only 50 psi. The added stress of thermal degradation would render a Portland cement useless in regard to adhesion in wells of the nature described above. Consequently, the need exists for a high strength cement exh~biting high shear bond and adhesion properties for the uses described.
In the drilling of conventional oil and gas wells, casing is cemented not only to secure the casing in the ; bore hole but also to prevent communication between water, oil and ~as-producing zones within the well. The typical procedure for cementing wells o this nature involves mixin~
Portland cement compositions at the well site and pumping the cement downwardly through casing and then outwardly and upward through a well between the casing and the wall of the bore hole. Ordinarily, a plurality of high pressure pumps and piping systems are required to guard against pump fallure. In the event o~ pump failure, the cement sets almost immediately and hardens, thereafter requiring expensi~e drillin~ operations to sal~age the well. Thus, it would be advantageous to provide a method of cementing a string o~ pipe in a bore hole ~hereby the cement will not set, harden or cure except by passage of time or ~y exposure of the cement to given temperature conditions that exist within the well or both. The present invention is directed to such method which eliminates the necessity of equipping
- 3 -: ' ' 1077~37~) cementing systems with duplicate pumps and related apparatus and which virtually eliminates the hazard of the cement setting before the desired time which might lead to loss of the well.
Applicant is aware of prior art in the field including U.S. Patents Nos. 1,318,076; 1,852,672; 2,042,011;
2,238,930; 2,279,262; 2,302,913; 2,502,418; 2,586,814;
2,665,996; 2,682,092; 2,701,209; 2,805,719; 2,B83~723;
2,895,838; 3,146,828; 3,180,748; 3,208,523; 3,244,230;
~0 3,253,664; 3,317,643; 3,326,269; 3~736~63; 3,374,834;
3,435,899 and 3,581,825, and an article entitled "~fect of Jet Perforating on Bond Strength of Cement" by W.~. Godrey, Journal of Petroleum Technology, pages ~301-14, November ~968. Of the fore~oing, Applicant deems the most pertinent to be Patents Nos. 1,852,672; 2,665,996; 3,146,828;
3,326,269 and 3,736,163.
The No. 1,852,672 patent is directed to pozzolanic activity of active clay minerals with alkaline earth oxides such as calcium and magne~ium. The No. 3,326,269 patent teaches the fixation o~ free silica by the high temperature firing of mixtures o colloidal silica and the hydroxide of various colloidal polyvalent metals. Neither patent is concerned with reactions or products sub~ect of the present invent~.on.
The No. 3,146,828 patent teaches the use of heat to generate a rigidized mineral mass of highly porous sillcate and silica of moderately low strength ~546 psi ~n the highest case). It teaches the use of the material to form a consolidating barrier o~ a permeable structure within - 30 the format~on surrounding the well bore, the purpose of which is to aid the fracturing or formations and assure a continuous recovery of 1uids. The bonding or cement-$tious material is defined as being sodium silicate to which is added a zinc oxide stabilizing agent in the amount of 0.5 to 2.0 parts by weight to ~educe the water sensiti-vity. The patent disclaims any bene~it~ of greater amounts of zinc oxide (column 6, lines 54 to 59) and describes a process wherein sodium silicate solutions are dehydrated thermally at such a rate (indicated by the minimum temper-0 ature shown as 175 ~) that a porous film results which 6erves as a binder. ~t has been found in practice that the cement of the ~828 patent is a water-vapor sensitlve product, one which is stable at low humi~ity but softens and degrades at 175 at 100% relative humidity within 24 hours o~ exposure. When formulations such as those described in column 5, lines 6 through 75, and column 6, lines ~ through 60, are prepared and cured under closed autoclave conditions at 175F. and lOOX relative humidity for ~ive days, a plastic non-rigid product results unless the sample is allowed to dehydrate~ Where evaporation ; is permitted or induced, the cement does harden. I~ such a ~ormulatlon is charged into a wall whose ~ormat~on permits water vapor transfer from the cement, a hardening will result. I~ the ~ormation is tight or if the cement is cast between non-porous stee~ casings as i~ often done, the cement may fail to set ~irmly and may not achieYe the porosity claimed by the inventor as cri~ical to the învention ~column 5, lines 6-16). Thus, the '828 patent formulations have defi nite llmitations.
The No~ 2~665~996 patent describes a hydrated _ S _ calcium silicate-cL~ystalline product that is unstable ~t temperatures above 450 F. and reacts at room temperature ilS well as elevated temperatures. Furthermore, the '966 patent product does not have the property of adhesion to steel~ By comparison~ the composition of the present invention is a ~ydrothermally reacted product, inert or unreacti~e at room tempera~ure while reacti~e at higher temperatures with the consequent bene~its of remaining mobile or pumpable for long periods of time at less than ~0 the threshold of activation temperatures. Furthermore, the product o~ the present lnvention cu~es to a heat-reslstant solid with ~reat adhesi~e strength to steel and resistance to acids and is an amorphous, pol~meric, non-crystall~.ne and non-hydrous solid as compared with that of the '996 patent.
Patent No. 3,736,163 dlscloses a lightweight insulatlve product consisting of mineral wool type fibers bonded together with calcium silicate moieties which become partially mineralized dur~ng use. The product of the '163 patent is cured in any autoclave at 200 psi steam ~400P.) for three hours, then drled and has negligible adhesion to metal and is a crystalline hydrate of d~calcium s~licates that are initially partially dehydrated before released for use.
The product of the '163 patent process survi~es temperatures o~ not greater than 1200 F. because of stress relief by way o~ microfractures and microstrain dissipated by the fi~er fillers~ When the same compositlons (875 pounds lime and 750 pounds of uncalcined diatomaceous earth, lS0 pounds of ; anhydrous ~odium silicate, 7 pounds of sugar, 60 pounds of nodulated mineral wool~ 60 pounds o~ sulfite pulp flbers and .. . .
.
10~7970 50 pounds o~ clay in 720 gallons of water) is autoclaved as described in the '163 patent, a product which is a mixture of crystallîne calcium silicates is obtained as confirmed by x-ray analysis.
By comparison, the vastly dif~eren~ composition of the present invention contains, ~or example, minimal amounts of water as compared with the ~163 patent.
Minimal watee in the product of the present ~nv~ntion allows reaction to form polymers of non-crystalline and non-hydrous solids ~hat provide reslstance to high temper-ature thereby dispensing with the necessity of fibers as in the '163 patent ~or the purpose of dissipating stres~es.
The present invention relates to a ~amily o~ cements characterized by hydrothermally initiated curing, the cement mixture retaining mobility or pumpability at less than the threshold activation temperature that initiates the cure. Ob~ectives of the invention are to provide such a cement of high strength and curable by a substantially greàter than conventional passage o~ time or by exposure to elevated temperature or both; a method for cementlng a strip o~ pipe in a bore hole through use of such hydro-thermal cement composition; a cement composition eminently ~uitabl~ and stable when cured for use in high temperature wells drilled into the earth; and to minimize energy or uel requirements in preparation of cement compo~tions.
A hydrothermal cement is defined herein as one that achieves a high degree o~ mechanical strength under some-what higher than standard atmospher~c temperature and pressure cond~tions, by in situ ~ormation of polyvalent sil~cate salts from reacting silica and metal oxides, -` 1077~70 hydroxides or sal~s o~ low solubility~ The reaction o~
silica and metal oxldes or hydroxides and orma~ion of polyvalent silicate salts involves a mechanism requiring heat and moisture to promote chemical combination of the basic constituents. Polyvalent metal oxides, hydroxides or salts that are capable of comblnation with sllica gel or silicates in an aqueous medium are lnduced to form the respective silicates by application of heat to aqueous slurries of th~se materials with silica ~lour and alkali metal silicates. The latter serve as reagents which react with the metal oxides to ~orm silicates and alkali metal oxide or hydroxide. The caustic by-product is free to react with silica from the sand and silica flour of tha formulation, and the resultant materials generate a reactive sodium silicate which rapeats the cycle until either the polyvalent metal is exhausted, the water evaporates or all of the silica is depleted or otherwise unavailable.
As used herein, the terms "initiation temperatu~e"
and "activation temperature~ both refer to the minimum temperature at which the foregoing described reactions begin and below which the materials simply are in physical mixture. Advantageously, the initiation temperatures of the amily o~ hydrothermal cements o the present invention vary according to the type of pol~valent metal ions and the ratio o~ SiO2/Na20 in the sodium silicate used. Consequently, setting o the cements o the present invention does not ,! .
occur wlth normal passage of time until the cement is - exposed to a temperature high enough to cause activation of the reactlons. This eature o the fo~mulation according to the present invention uniquely adapts the cement composi~-.
ions for use in cementing casing in well bores and the like. The cement has high strength and is also well suited for many other uses.
It is, thereore, an object of the present invention to provide a family of cements characterized as susceptible of hydrothermally initiated cure, the cementitious mixture remaining mobile or pu~pable ~or long periods of time at less than the threshold of activation temperatures.
A further ob~ect o~ the presenk invention is the provision of a ~amily o~ cements comprising high molecular weight~ inorganic polymers from the reaction of polyvalent metals with silica under conditions o~ moisture and elevated temperatures.
A further ob~ect of the present in~ention is the provision of hydrothermal cements, each comprising a mixture of a polyvalent metal salt, water and a silica source that can be hydrated by time or temperature such that the silica is available for combination with the polyvalent metal salt upon application of heat.
A still fur~her ob~ect of the present invention is the provision of a method of cementing pipe or casing within a well bore wherein a hydrothermal cement of the ~oregoin~
compo~ition is prepared and pumped into the annular space between the pipe and walls of the bore hole and then allowed to set due to temperature conditions in the bore hole or by passage o~ t~me or both.
Yet a further ob~ect of the present invention is the pro~ision of such a method that reduces the necessity of dupllcative pumping and circulating equipment inasmuch as ailure o~ such equipment does not in and of itsalf result in setting of the cements in a bore hole.
A still further object of the present invention is the provision of such a method whereby the ce~ent may be mixed offsite, is transported to the site and may be held for long periods of time relative to Portland cement before use and before setting occurs.
A further object of this invention is the provision of a water-reducing reagent which minimizes the water required to obtain work-ability of a slurry containing cement forming reactants according to the present invention and hence optimizes the physical, mechanical and chemical properties of the cured cement.
A still further object of this invention is the provision of a coating, binder or building product of high mechanical strength, chemical resistance, abrasion resistance and resistance to intense and prolonged heating and heat cycling.
Other and further objects, features and advantages will be apparent in the follawing description of presently preferred embodiments of the invention, given for the purpose of disclosure.
Thus, in summary, the invention provides a cement c~n~osition consisting essentially of one of a poly~alent metal oxide, hydroxide, salt of low solubility or mixture thereof, water, a silica source h~ratable under time and temperature conditions through reactions wherein the silica becomes available for chemical combination with the polyvalent metal ion source upon application of heat, and a water reducing reagent ccmprising a spray dried s~dium silicate hydrate powder.
In a further general embodiment the invention provides a method of cementing a string of pipe in a bore hole, comprising the steps of preparing a cement cc~position consisting essentially of one of a polyvalent metal oxide hydroxide, salt or mixture thereof, water, a silica source hydratable under time and temperature conditions through r, .
..
.
--``` 1077970 reactions wherein the silica is available for chemical comb i tion with the polyvalent metal ion source upon application of heat, and a water reducing reagent comprising a spray dried sodium silicate hydrate powder, pumping the cement composition into an annular space between the string of pipe and the walls of the bore holes, and allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
The cement composition of the present invention is formNlated by blending dry components including the polyvalent metal ion source such as one of a polyvalent metal oxide, hydroxide, salts of low solubility, or mixtures thereof together with a silica source such as clay, silica, flour, silica sand and sodium silicates or equivalent .
substitutes. A water-reducing reagent comprising a spray-dried ; hydrated sodium silicate powder is used to reduce the amount of water needed to fluidize the system. Preferably, - lOa -~`;
the blending a~d mixlng step is co~ducted in a closed container substantially free o~ air and water to prevent lumping because of moisture a~d to prevent carbonation of silicates by carbon dioxide in the air. The blend of dry materials is then slurried with the required (as will be explained~ minimum amounts of water. Prolonged delay in adding water, especially in a humid environment, allows the powdered ~ixture to cake and subsequently makes it more difficult to disperse and hydrateL The consistency o the water/solid mixture undergoes a dramatic transition withln ten minutes following the addition of water where~y a marked drop in viscosity converts an otherwise damp cake to a thin, pumpable slurry. This occurs as a consequence of the dissolution of the hydrated sodium silicate. The slurry ~iscosity can be varied drastically by adding relatively small ~1 to 2~ by weight) increments of water.
The polyvalent ~etal ion which is a reactant and ingredient o~ the cement composition according to the present invention is a polyvalent metal oxide, hydroxide, low solubility salt or mixture thereof. The polyvalent metal oxides, hydroxides, and salts that may be used include the oxides o~ zinc, magnesium, iron~ aluminum, manganese, titanium, zirconium, vanadium and hafnium; the hydroxide of aluminum; the carbonates of zinc and magnesium; and the phosphates o~ calcium, magnesium and aluminum.
Examples o~ ~ormulations making use of various o~
the poly~alent metal ion sources are as follows wherein particle size is less than the stated mesh, standard ASTM
Ell analysis, unless otherwise indicated.
~077970 ExamPle Parts by Weight Ranqe Preferred Sand ~20-60 mesh) 40~60 50 Silica flour (325 mesh) 20-40 25 2.4/1 ratio SiO2/Na20 Hydrated Sodium Silica~e Powder (325 meshS 5-15 ~0 3.22/1 ratio SiO2/Na20 Anhydrous Sodium Silicate Powder (325 mesh) 5-15 10 Flyash 0-25 0 Zinc oxide (<1 micron) 5-15 7 Water 15-20~ 17-~Per hundred parts by weight of total solids ~phpts~').
Using the preferred formulation, the cement begins to act at an acti~ation temperature of 150F. and sets firmly in 24 hours at this temperature. At 200F., a hard cure is achieved in less than 24 hours. In about one week, the cement attains a compressive strength of 4000 psi at 200~. and a shear bond o~ 1300 psi. The cured cement resists temperature to 2000~. without adversely affecting its physical strength. In this example as in all subsequent examples, the procedure fol~owed or determining compres-si~e stren~th is ASTM C109-54T while the test ~or determing shear bond or adhesive strength is one used conventionally in the petroleum industry. It consists of measuring the force per unit area required to displace or disrupt the 30 bond between a metal cylinder and a concrete cylinder.
10'77~70 Parts by Weiqht Ranqe Preferred Sand 40-60 50 Silica flour 20-40 25 2.4/1 ratio Si02/Na20 Hydrated Sodium Silicate Powder 5-~5 10 3.22/1 ratio Si02/Na20 ~0 Anhydrous Sodium Silicate Powder 5-lS ~0 Aluminum Hydroxide ~reagent grade preferred from HaA123 ~ Nh4)H) 5-20 7 Wa~er ~5-20 phpts 17 phpts This ~ormulation is indefinitely stable below 145F.
but rapidly begins to thicken at 200 F. No true setting is observed below 165 F. and the preferred activation temperature for finite rates o observable change in setting characteristics is 200 F. A cure of two weeks at 200 F.
results in a compressive strength of over 2000 psi. Over 3000 ps~, compressive strength is obtained at 200 F. in four weeks. Approximatel~ 4000 psi is obtainable in five to six weeks at this temperature. At 300 ~., strengths " on the order of 4700 psi are obtainable in two weeks. The cement has a shear bond strength o~ 1300 ps~ and withstands temperatures o~ up to 1000 F. without adversely a~fecting its phys~cal strength.
~ ' ., .
~077970 Example 3 Parts bv Weiqht Ranqe Preferred Sand 40-60 50 Silica flour 20-40 25 3.22/1 ratio SiO2/Na20 Anhydro~s Sodium Silicate Powder 5-15 10 2.4/1 ratio SiO2~Na20 ~ydr~ted Sodium Silicate Powder S-15 10 Aluminum Hydroxide (commer-cial grade ~rom NaA1203 +
steam) 5-15 7 Water 15-20 phpts ~7 phpts Activation temperatures on the order o~ 225F. result in a strength of 3700 psi in about 72 hours.
Example 4 Parts by Wei~ht Range Preferred Sand 40-60 50 Silica flour 20-40 25 3.22/1 ratio SiO2/Na20 Anhydrous Sodium Silicate Powder 5-15 10 2.4/1 ratio SiO2/Na20 Hydrated Sodium Silicate Powder 5~~5 ~
Al203 Calcined or Rehydrat-ed 5-15 7 Water , 15-20 phpts 17 phpts - 14 _ 1077~7~
The lowest observed practical activation temperature ~or this for~ulation is 225 F. A temperature of 300 F.
is preferred since this results in curing being substant-ially completed in a period of less than two weeks A
strength of 3700 psi is obtainable in about 72 hours with an acti~ation temperature o~ 300 F.
ExamPle 5 Parts b~ Weight Ranqe Preferred Sand 40-60 50 Silica flour 20-40 25 7.5/1 ratio SiO2/Na20 Anhydrous Sodium Silicate Powder 5-15 10 2.4/1 ratio SiO2/Na20 Hydrated Sodium Silicate Powder 5-15 S
zinc ox~de 5-15 7 Water 15 20 phpts 17 phpts The substitution of 7.5/1 ratio ~SiO2/Na20~ sodium silicate for 3.22/1 ratio reduces the activation temperature from 150 F. to ~35 F. The compressive strength of this recipe after seven days at 135 ~. is 3600 psi. If the more alkaline sodium silicates are used (ratio o~ 3/1 and less, i.e~, 2/1 or 2.4/1 al~ne), no setting ~s observed in ~ive days at 150 ~. The 2.4/1 ratio silicate serves as a ~luidizer or viscosity-improving additive during the handling of the cement mixture. The more alkaline silicates require higher temperatures and/or longer times to react and rigidize, .
-- 15 _ The formulations of Examples 1-5 may be used excluding or replacing the sodium silicates ~hydrous and anhydrous) with sod~um hydroxide in parts by weight of 1 to 10, 5 parts by weight being preferred. This substitution may be used without appreciable effect on the chemical or physical properties as indicated in each example. The kinetics of each formulat~on will be affected to some degree by the substitution.
~0 As previously stated, formulations of the cement composition according to the present invention may be made usi~g still other polyvalent metal oxides, hydroxides or salts. For e~ample, the oxides of magnesium iron, aluminum, man~anese, titanium, zirconium, vanadium and hanium, the carbonates of zinc and magnesium and the phos-phates of magnesium and aluminum may be used. Concentrat-ions of any of these substitutes for the polyvalent metal compounds of Examples 1-6 should be proportioned to the relative equivalent weights of these compounds compared to the equivalent weights of the polyvalent metal compounds cited in these examples~
The inclusion of sodium silicates in these formulations is not a mandatory requirement but is preferred. Sodium silicate is produced by high energy-consuming processes, and in order to minimize inclusio~ of materials of this nature, the silicate may be generated in the cement system by the reaction of sodium hydroxide with available silica.
Various clays~ sands and ground sand are suitable sources of silica for this purpose~
Any washed sand used conventionally in Portland cement, ~0'77~70 concrete and mortar formulations may be used in the cement iFormulations o~ the present inven~ion. The sand has little effect on strength of the resultant cement products but affects cost, fluidity and bulking factor of the cement mixture.
Silica flour likewise should be of low clay content and the proportions used dictate fluidity and strength of the set mater~al ~ersus time. That is, the more silica flour used, the less fluid is the cement mixture before setting but the greater strength after setting in given periods of time.
With regard to silicates used, anhydrous s~licate is used partly as a matter of convenience to tie up free water that results after all reactions are concluded. The more silicate of this nature used~ the faster the cure. The ratio of Si~2/Na20 in the sodium silicate is a reaction rate controlling factor. The more siliceous grades (higher SiO2 ra~ios) react more rapidly and at lower temperatures than the more alkaline grades.
With respect to the alkali metal silicate hydrate powders, which preferably are produced by conventional spray drying of alkali metal silicate solutions of a narrow range of SiO2/~a20 ratios, the powders surprisin~ly have been found to produce a high degree o~ fluidity in slurries with ~ery small quantities of water. This latter feature constitutes one source o~ the unique physical, chemical and mechanical properties described herein. Water, essential to the chemical curing of most inorganic cement systems is quantitatively critical to the final p~od~ct properties.
Any excess or residual water in a cured~product evaporates 1~779~0 leaving pores and sites of vulnerability to free-~haw damage, infusion of ~oreign matterl reduced stre~gth, etc.
Trapped water or waters of hydration common to all hydraul-ic cements like Portland limit the heat resistance of the products. Since the novel cement of the present invention employs only 15 to 20X moisture, a higher degree of imperm-eability and greater mechanical strength may be achieved than is possible otherwise. The addition of water induces a partial solution of the alkali metal hydrate powders which upon dissolution fluidizes the system by release of a colloided electrolyte that imposes a partial charge on the slurry inducinq a high degree of lubricity where equivalent slurries without the electrolyte would appear as slightly dampened powders. This liquification does not occur immediately upon addition of water and its blending with the dry powders. After about two minutes with little or no agitation, the dampened mass suddenly liquifies to a highly fluid state which can be readily poured, pumped and ~xtruded.
This slurry can subseque~tly be rendered thixotropic by addition of any suitable bentonite product.
With respect to the polyvalent metal compounds used in each ~ormulation, the concentration of the particular metal compound should be proportional to all others according to equlvalent wei~hts. Without the polyvalent metal compounds, all other constituents would remain relatively inactive.
With respect to water used ln the formulations of the present invention, any clear water may be used as is uaed in conventional concrete and mortar ~ormulations. The amount of water affects fluidity and~final strength. That is, the more water used, the greater the fluldity of the _ 18 -~ 077970 mixture before setting but the lower the strength a~ter set. Water is essential to promote reaction of silicate polymers and salts of the polyvalent metals.
Flyash and other pozzolanic materials may be used as fillers to perform the same function that sand performs as outlined above.
Concretes may be prepared by adding gravel and rock to mortar formulations of the present invention. Concretes prepared accordingly exhibit very low water absorption when cured, even a~ter exposure to several hundred degree temperature. Consequently, the formulations of the present invention are uniquely suited for use in formulation build-ing materials that are or may all be "low energy produced"
in that no calcining or kiln processing is required to prepare the raw materials for the concrete, espec~ally when the aforementioned sodium hydroxide-silica reaction is employed to generate sodium silicate.
As may be seen from the examples, formulation of cement compositions according to the present invention by using diferent polyvalent metal compounds results in different formulations having varying activation temperatures. For example, the formulation o Example 1 has an activation o 150 F. and the ~ormulation of Example 3 has an activation temperature o~ 225 F. As a result, it will now be appar~nt that a formulation may be selected having a specific activation temperature such that the formulation is uniquely adaptable for use in temperature environments wherein the cement remains mobile until subjec~ed to a temperature high enough to activate setting and curing reactions. For example~ various ~ormulations of cement according to the present invention may be used in cementing pipe or casing within bore holes of wells drilled in the earth. Since temperature at a given point within a bore hole depends on depth of the well~ the formulation used to cement the casing may be selected by determining temperature of the bore hole and compar~ng that temperature to the activated temperature of the various ~ormulations of the present in~ention. For example, ~f the downhole temperature is approximately 150 F~, the formulation o~ Example 1 may be used whereby the bore hole temperature o~ 150 ~. causes the cement to set when ~inally placed in the well. How-ever, below ~uch temperature the cement remains mobile or pumpable ~or long periods o~ time relative to conventional Portland cements. In the same way, other cements from among formulations of the present invention may be selected for use in bore holes having different temperatures, necessitating use of formulations having corresponding activation temper-atures.
In using cement formulations of the present invention for cementing casing in wells, the cement is prepared as explained elsewhere herein. The cement may be prepared at the well site although, advantageously, it may be prepared at points remote from the well site and shipped to the site w~thout setting. ~inimal agitation is required while holding the cement prior to use, the agitation serving merely to prevent stratification of the material. This feature of formulations according to the present invention is extremely significant when considering the mixing and trans-portation problems of con~entional P~rtla~d cements.
The cement i5 then pumped into the annular space ~etween - 20 _ ~
the string of pipe or casln~ and the walls of the bore hole as in conventional processes. However, the need for standby pumping equipment is not as critical since the cement of the present invention will not set for several hours after being subjected to the ac~ivation te~perature, thereby allowing adequate time for repair or replacement of the pumping equipment. Once in place in the well, pumping stops and the cement is allowed to set due to temperature of the bore hole or by passage of time or both. In thi~ connection, cement formulations of the present invention having activation temperatures substantially lower than temperature of the bore hole may be used although shorter periods of time than those described in the examples will be experienced for setting and curing to take place. In any event, the ultimate strengths obtainable by the present cement are at least as great as those obtained by conventional Portland cements while the shear bond strength exceed those of Portland , cement as indicated in the examples. Conse~uently, the ; 20 cement formulations of the present invention provide adhesive strengths that greatly exceed those of conventional Portland cements and thereby uniquely adapt formulatlons of the present invention for use in high temperature bore holes such as geothermal wells and the like.
Still other uses of formulations according to the present invention may ~e made depending on temperature requirements and length of time available for setting and curing. It will now be apparent to those s~lled in the art that formulations of the in~ention may be used for a variety o~ applications~
:`
1~77970 The present invention, therefore~ is well adapted to --carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While presently preferred embodiments of the invention have been given for the purpose o disclosure, numerous changes in the details of formulations and operation of the methods involved can be made which will readily suggest themselves to those skilled in the art and which are encompassed within the scope of the invention and the scope o~ the appended claims.
_ ~2 -
Applicant is aware of prior art in the field including U.S. Patents Nos. 1,318,076; 1,852,672; 2,042,011;
2,238,930; 2,279,262; 2,302,913; 2,502,418; 2,586,814;
2,665,996; 2,682,092; 2,701,209; 2,805,719; 2,B83~723;
2,895,838; 3,146,828; 3,180,748; 3,208,523; 3,244,230;
~0 3,253,664; 3,317,643; 3,326,269; 3~736~63; 3,374,834;
3,435,899 and 3,581,825, and an article entitled "~fect of Jet Perforating on Bond Strength of Cement" by W.~. Godrey, Journal of Petroleum Technology, pages ~301-14, November ~968. Of the fore~oing, Applicant deems the most pertinent to be Patents Nos. 1,852,672; 2,665,996; 3,146,828;
3,326,269 and 3,736,163.
The No. 1,852,672 patent is directed to pozzolanic activity of active clay minerals with alkaline earth oxides such as calcium and magne~ium. The No. 3,326,269 patent teaches the fixation o~ free silica by the high temperature firing of mixtures o colloidal silica and the hydroxide of various colloidal polyvalent metals. Neither patent is concerned with reactions or products sub~ect of the present invent~.on.
The No. 3,146,828 patent teaches the use of heat to generate a rigidized mineral mass of highly porous sillcate and silica of moderately low strength ~546 psi ~n the highest case). It teaches the use of the material to form a consolidating barrier o~ a permeable structure within - 30 the format~on surrounding the well bore, the purpose of which is to aid the fracturing or formations and assure a continuous recovery of 1uids. The bonding or cement-$tious material is defined as being sodium silicate to which is added a zinc oxide stabilizing agent in the amount of 0.5 to 2.0 parts by weight to ~educe the water sensiti-vity. The patent disclaims any bene~it~ of greater amounts of zinc oxide (column 6, lines 54 to 59) and describes a process wherein sodium silicate solutions are dehydrated thermally at such a rate (indicated by the minimum temper-0 ature shown as 175 ~) that a porous film results which 6erves as a binder. ~t has been found in practice that the cement of the ~828 patent is a water-vapor sensitlve product, one which is stable at low humi~ity but softens and degrades at 175 at 100% relative humidity within 24 hours o~ exposure. When formulations such as those described in column 5, lines 6 through 75, and column 6, lines ~ through 60, are prepared and cured under closed autoclave conditions at 175F. and lOOX relative humidity for ~ive days, a plastic non-rigid product results unless the sample is allowed to dehydrate~ Where evaporation ; is permitted or induced, the cement does harden. I~ such a ~ormulatlon is charged into a wall whose ~ormat~on permits water vapor transfer from the cement, a hardening will result. I~ the ~ormation is tight or if the cement is cast between non-porous stee~ casings as i~ often done, the cement may fail to set ~irmly and may not achieYe the porosity claimed by the inventor as cri~ical to the învention ~column 5, lines 6-16). Thus, the '828 patent formulations have defi nite llmitations.
The No~ 2~665~996 patent describes a hydrated _ S _ calcium silicate-cL~ystalline product that is unstable ~t temperatures above 450 F. and reacts at room temperature ilS well as elevated temperatures. Furthermore, the '966 patent product does not have the property of adhesion to steel~ By comparison~ the composition of the present invention is a ~ydrothermally reacted product, inert or unreacti~e at room tempera~ure while reacti~e at higher temperatures with the consequent bene~its of remaining mobile or pumpable for long periods of time at less than ~0 the threshold of activation temperatures. Furthermore, the product o~ the present lnvention cu~es to a heat-reslstant solid with ~reat adhesi~e strength to steel and resistance to acids and is an amorphous, pol~meric, non-crystall~.ne and non-hydrous solid as compared with that of the '996 patent.
Patent No. 3,736,163 dlscloses a lightweight insulatlve product consisting of mineral wool type fibers bonded together with calcium silicate moieties which become partially mineralized dur~ng use. The product of the '163 patent is cured in any autoclave at 200 psi steam ~400P.) for three hours, then drled and has negligible adhesion to metal and is a crystalline hydrate of d~calcium s~licates that are initially partially dehydrated before released for use.
The product of the '163 patent process survi~es temperatures o~ not greater than 1200 F. because of stress relief by way o~ microfractures and microstrain dissipated by the fi~er fillers~ When the same compositlons (875 pounds lime and 750 pounds of uncalcined diatomaceous earth, lS0 pounds of ; anhydrous ~odium silicate, 7 pounds of sugar, 60 pounds of nodulated mineral wool~ 60 pounds o~ sulfite pulp flbers and .. . .
.
10~7970 50 pounds o~ clay in 720 gallons of water) is autoclaved as described in the '163 patent, a product which is a mixture of crystallîne calcium silicates is obtained as confirmed by x-ray analysis.
By comparison, the vastly dif~eren~ composition of the present invention contains, ~or example, minimal amounts of water as compared with the ~163 patent.
Minimal watee in the product of the present ~nv~ntion allows reaction to form polymers of non-crystalline and non-hydrous solids ~hat provide reslstance to high temper-ature thereby dispensing with the necessity of fibers as in the '163 patent ~or the purpose of dissipating stres~es.
The present invention relates to a ~amily o~ cements characterized by hydrothermally initiated curing, the cement mixture retaining mobility or pumpability at less than the threshold activation temperature that initiates the cure. Ob~ectives of the invention are to provide such a cement of high strength and curable by a substantially greàter than conventional passage o~ time or by exposure to elevated temperature or both; a method for cementlng a strip o~ pipe in a bore hole through use of such hydro-thermal cement composition; a cement composition eminently ~uitabl~ and stable when cured for use in high temperature wells drilled into the earth; and to minimize energy or uel requirements in preparation of cement compo~tions.
A hydrothermal cement is defined herein as one that achieves a high degree o~ mechanical strength under some-what higher than standard atmospher~c temperature and pressure cond~tions, by in situ ~ormation of polyvalent sil~cate salts from reacting silica and metal oxides, -` 1077~70 hydroxides or sal~s o~ low solubility~ The reaction o~
silica and metal oxldes or hydroxides and orma~ion of polyvalent silicate salts involves a mechanism requiring heat and moisture to promote chemical combination of the basic constituents. Polyvalent metal oxides, hydroxides or salts that are capable of comblnation with sllica gel or silicates in an aqueous medium are lnduced to form the respective silicates by application of heat to aqueous slurries of th~se materials with silica ~lour and alkali metal silicates. The latter serve as reagents which react with the metal oxides to ~orm silicates and alkali metal oxide or hydroxide. The caustic by-product is free to react with silica from the sand and silica flour of tha formulation, and the resultant materials generate a reactive sodium silicate which rapeats the cycle until either the polyvalent metal is exhausted, the water evaporates or all of the silica is depleted or otherwise unavailable.
As used herein, the terms "initiation temperatu~e"
and "activation temperature~ both refer to the minimum temperature at which the foregoing described reactions begin and below which the materials simply are in physical mixture. Advantageously, the initiation temperatures of the amily o~ hydrothermal cements o the present invention vary according to the type of pol~valent metal ions and the ratio o~ SiO2/Na20 in the sodium silicate used. Consequently, setting o the cements o the present invention does not ,! .
occur wlth normal passage of time until the cement is - exposed to a temperature high enough to cause activation of the reactlons. This eature o the fo~mulation according to the present invention uniquely adapts the cement composi~-.
ions for use in cementing casing in well bores and the like. The cement has high strength and is also well suited for many other uses.
It is, thereore, an object of the present invention to provide a family of cements characterized as susceptible of hydrothermally initiated cure, the cementitious mixture remaining mobile or pu~pable ~or long periods of time at less than the threshold of activation temperatures.
A further ob~ect o~ the presenk invention is the provision of a ~amily o~ cements comprising high molecular weight~ inorganic polymers from the reaction of polyvalent metals with silica under conditions o~ moisture and elevated temperatures.
A further ob~ect of the present in~ention is the provision of hydrothermal cements, each comprising a mixture of a polyvalent metal salt, water and a silica source that can be hydrated by time or temperature such that the silica is available for combination with the polyvalent metal salt upon application of heat.
A still fur~her ob~ect of the present invention is the provision of a method of cementing pipe or casing within a well bore wherein a hydrothermal cement of the ~oregoin~
compo~ition is prepared and pumped into the annular space between the pipe and walls of the bore hole and then allowed to set due to temperature conditions in the bore hole or by passage o~ t~me or both.
Yet a further ob~ect of the present invention is the pro~ision of such a method that reduces the necessity of dupllcative pumping and circulating equipment inasmuch as ailure o~ such equipment does not in and of itsalf result in setting of the cements in a bore hole.
A still further object of the present invention is the provision of such a method whereby the ce~ent may be mixed offsite, is transported to the site and may be held for long periods of time relative to Portland cement before use and before setting occurs.
A further object of this invention is the provision of a water-reducing reagent which minimizes the water required to obtain work-ability of a slurry containing cement forming reactants according to the present invention and hence optimizes the physical, mechanical and chemical properties of the cured cement.
A still further object of this invention is the provision of a coating, binder or building product of high mechanical strength, chemical resistance, abrasion resistance and resistance to intense and prolonged heating and heat cycling.
Other and further objects, features and advantages will be apparent in the follawing description of presently preferred embodiments of the invention, given for the purpose of disclosure.
Thus, in summary, the invention provides a cement c~n~osition consisting essentially of one of a poly~alent metal oxide, hydroxide, salt of low solubility or mixture thereof, water, a silica source h~ratable under time and temperature conditions through reactions wherein the silica becomes available for chemical combination with the polyvalent metal ion source upon application of heat, and a water reducing reagent ccmprising a spray dried s~dium silicate hydrate powder.
In a further general embodiment the invention provides a method of cementing a string of pipe in a bore hole, comprising the steps of preparing a cement cc~position consisting essentially of one of a polyvalent metal oxide hydroxide, salt or mixture thereof, water, a silica source hydratable under time and temperature conditions through r, .
..
.
--``` 1077970 reactions wherein the silica is available for chemical comb i tion with the polyvalent metal ion source upon application of heat, and a water reducing reagent comprising a spray dried sodium silicate hydrate powder, pumping the cement composition into an annular space between the string of pipe and the walls of the bore holes, and allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
The cement composition of the present invention is formNlated by blending dry components including the polyvalent metal ion source such as one of a polyvalent metal oxide, hydroxide, salts of low solubility, or mixtures thereof together with a silica source such as clay, silica, flour, silica sand and sodium silicates or equivalent .
substitutes. A water-reducing reagent comprising a spray-dried ; hydrated sodium silicate powder is used to reduce the amount of water needed to fluidize the system. Preferably, - lOa -~`;
the blending a~d mixlng step is co~ducted in a closed container substantially free o~ air and water to prevent lumping because of moisture a~d to prevent carbonation of silicates by carbon dioxide in the air. The blend of dry materials is then slurried with the required (as will be explained~ minimum amounts of water. Prolonged delay in adding water, especially in a humid environment, allows the powdered ~ixture to cake and subsequently makes it more difficult to disperse and hydrateL The consistency o the water/solid mixture undergoes a dramatic transition withln ten minutes following the addition of water where~y a marked drop in viscosity converts an otherwise damp cake to a thin, pumpable slurry. This occurs as a consequence of the dissolution of the hydrated sodium silicate. The slurry ~iscosity can be varied drastically by adding relatively small ~1 to 2~ by weight) increments of water.
The polyvalent ~etal ion which is a reactant and ingredient o~ the cement composition according to the present invention is a polyvalent metal oxide, hydroxide, low solubility salt or mixture thereof. The polyvalent metal oxides, hydroxides, and salts that may be used include the oxides o~ zinc, magnesium, iron~ aluminum, manganese, titanium, zirconium, vanadium and hafnium; the hydroxide of aluminum; the carbonates of zinc and magnesium; and the phosphates o~ calcium, magnesium and aluminum.
Examples o~ ~ormulations making use of various o~
the poly~alent metal ion sources are as follows wherein particle size is less than the stated mesh, standard ASTM
Ell analysis, unless otherwise indicated.
~077970 ExamPle Parts by Weight Ranqe Preferred Sand ~20-60 mesh) 40~60 50 Silica flour (325 mesh) 20-40 25 2.4/1 ratio SiO2/Na20 Hydrated Sodium Silica~e Powder (325 meshS 5-15 ~0 3.22/1 ratio SiO2/Na20 Anhydrous Sodium Silicate Powder (325 mesh) 5-15 10 Flyash 0-25 0 Zinc oxide (<1 micron) 5-15 7 Water 15-20~ 17-~Per hundred parts by weight of total solids ~phpts~').
Using the preferred formulation, the cement begins to act at an acti~ation temperature of 150F. and sets firmly in 24 hours at this temperature. At 200F., a hard cure is achieved in less than 24 hours. In about one week, the cement attains a compressive strength of 4000 psi at 200~. and a shear bond o~ 1300 psi. The cured cement resists temperature to 2000~. without adversely affecting its physical strength. In this example as in all subsequent examples, the procedure fol~owed or determining compres-si~e stren~th is ASTM C109-54T while the test ~or determing shear bond or adhesive strength is one used conventionally in the petroleum industry. It consists of measuring the force per unit area required to displace or disrupt the 30 bond between a metal cylinder and a concrete cylinder.
10'77~70 Parts by Weiqht Ranqe Preferred Sand 40-60 50 Silica flour 20-40 25 2.4/1 ratio Si02/Na20 Hydrated Sodium Silicate Powder 5-~5 10 3.22/1 ratio Si02/Na20 ~0 Anhydrous Sodium Silicate Powder 5-lS ~0 Aluminum Hydroxide ~reagent grade preferred from HaA123 ~ Nh4)H) 5-20 7 Wa~er ~5-20 phpts 17 phpts This ~ormulation is indefinitely stable below 145F.
but rapidly begins to thicken at 200 F. No true setting is observed below 165 F. and the preferred activation temperature for finite rates o observable change in setting characteristics is 200 F. A cure of two weeks at 200 F.
results in a compressive strength of over 2000 psi. Over 3000 ps~, compressive strength is obtained at 200 F. in four weeks. Approximatel~ 4000 psi is obtainable in five to six weeks at this temperature. At 300 ~., strengths " on the order of 4700 psi are obtainable in two weeks. The cement has a shear bond strength o~ 1300 ps~ and withstands temperatures o~ up to 1000 F. without adversely a~fecting its phys~cal strength.
~ ' ., .
~077970 Example 3 Parts bv Weiqht Ranqe Preferred Sand 40-60 50 Silica flour 20-40 25 3.22/1 ratio SiO2/Na20 Anhydro~s Sodium Silicate Powder 5-15 10 2.4/1 ratio SiO2~Na20 ~ydr~ted Sodium Silicate Powder S-15 10 Aluminum Hydroxide (commer-cial grade ~rom NaA1203 +
steam) 5-15 7 Water 15-20 phpts ~7 phpts Activation temperatures on the order o~ 225F. result in a strength of 3700 psi in about 72 hours.
Example 4 Parts by Wei~ht Range Preferred Sand 40-60 50 Silica flour 20-40 25 3.22/1 ratio SiO2/Na20 Anhydrous Sodium Silicate Powder 5-15 10 2.4/1 ratio SiO2/Na20 Hydrated Sodium Silicate Powder 5~~5 ~
Al203 Calcined or Rehydrat-ed 5-15 7 Water , 15-20 phpts 17 phpts - 14 _ 1077~7~
The lowest observed practical activation temperature ~or this for~ulation is 225 F. A temperature of 300 F.
is preferred since this results in curing being substant-ially completed in a period of less than two weeks A
strength of 3700 psi is obtainable in about 72 hours with an acti~ation temperature o~ 300 F.
ExamPle 5 Parts b~ Weight Ranqe Preferred Sand 40-60 50 Silica flour 20-40 25 7.5/1 ratio SiO2/Na20 Anhydrous Sodium Silicate Powder 5-15 10 2.4/1 ratio SiO2/Na20 Hydrated Sodium Silicate Powder 5-15 S
zinc ox~de 5-15 7 Water 15 20 phpts 17 phpts The substitution of 7.5/1 ratio ~SiO2/Na20~ sodium silicate for 3.22/1 ratio reduces the activation temperature from 150 F. to ~35 F. The compressive strength of this recipe after seven days at 135 ~. is 3600 psi. If the more alkaline sodium silicates are used (ratio o~ 3/1 and less, i.e~, 2/1 or 2.4/1 al~ne), no setting ~s observed in ~ive days at 150 ~. The 2.4/1 ratio silicate serves as a ~luidizer or viscosity-improving additive during the handling of the cement mixture. The more alkaline silicates require higher temperatures and/or longer times to react and rigidize, .
-- 15 _ The formulations of Examples 1-5 may be used excluding or replacing the sodium silicates ~hydrous and anhydrous) with sod~um hydroxide in parts by weight of 1 to 10, 5 parts by weight being preferred. This substitution may be used without appreciable effect on the chemical or physical properties as indicated in each example. The kinetics of each formulat~on will be affected to some degree by the substitution.
~0 As previously stated, formulations of the cement composition according to the present invention may be made usi~g still other polyvalent metal oxides, hydroxides or salts. For e~ample, the oxides of magnesium iron, aluminum, man~anese, titanium, zirconium, vanadium and hanium, the carbonates of zinc and magnesium and the phos-phates of magnesium and aluminum may be used. Concentrat-ions of any of these substitutes for the polyvalent metal compounds of Examples 1-6 should be proportioned to the relative equivalent weights of these compounds compared to the equivalent weights of the polyvalent metal compounds cited in these examples~
The inclusion of sodium silicates in these formulations is not a mandatory requirement but is preferred. Sodium silicate is produced by high energy-consuming processes, and in order to minimize inclusio~ of materials of this nature, the silicate may be generated in the cement system by the reaction of sodium hydroxide with available silica.
Various clays~ sands and ground sand are suitable sources of silica for this purpose~
Any washed sand used conventionally in Portland cement, ~0'77~70 concrete and mortar formulations may be used in the cement iFormulations o~ the present inven~ion. The sand has little effect on strength of the resultant cement products but affects cost, fluidity and bulking factor of the cement mixture.
Silica flour likewise should be of low clay content and the proportions used dictate fluidity and strength of the set mater~al ~ersus time. That is, the more silica flour used, the less fluid is the cement mixture before setting but the greater strength after setting in given periods of time.
With regard to silicates used, anhydrous s~licate is used partly as a matter of convenience to tie up free water that results after all reactions are concluded. The more silicate of this nature used~ the faster the cure. The ratio of Si~2/Na20 in the sodium silicate is a reaction rate controlling factor. The more siliceous grades (higher SiO2 ra~ios) react more rapidly and at lower temperatures than the more alkaline grades.
With respect to the alkali metal silicate hydrate powders, which preferably are produced by conventional spray drying of alkali metal silicate solutions of a narrow range of SiO2/~a20 ratios, the powders surprisin~ly have been found to produce a high degree o~ fluidity in slurries with ~ery small quantities of water. This latter feature constitutes one source o~ the unique physical, chemical and mechanical properties described herein. Water, essential to the chemical curing of most inorganic cement systems is quantitatively critical to the final p~od~ct properties.
Any excess or residual water in a cured~product evaporates 1~779~0 leaving pores and sites of vulnerability to free-~haw damage, infusion of ~oreign matterl reduced stre~gth, etc.
Trapped water or waters of hydration common to all hydraul-ic cements like Portland limit the heat resistance of the products. Since the novel cement of the present invention employs only 15 to 20X moisture, a higher degree of imperm-eability and greater mechanical strength may be achieved than is possible otherwise. The addition of water induces a partial solution of the alkali metal hydrate powders which upon dissolution fluidizes the system by release of a colloided electrolyte that imposes a partial charge on the slurry inducinq a high degree of lubricity where equivalent slurries without the electrolyte would appear as slightly dampened powders. This liquification does not occur immediately upon addition of water and its blending with the dry powders. After about two minutes with little or no agitation, the dampened mass suddenly liquifies to a highly fluid state which can be readily poured, pumped and ~xtruded.
This slurry can subseque~tly be rendered thixotropic by addition of any suitable bentonite product.
With respect to the polyvalent metal compounds used in each ~ormulation, the concentration of the particular metal compound should be proportional to all others according to equlvalent wei~hts. Without the polyvalent metal compounds, all other constituents would remain relatively inactive.
With respect to water used ln the formulations of the present invention, any clear water may be used as is uaed in conventional concrete and mortar ~ormulations. The amount of water affects fluidity and~final strength. That is, the more water used, the greater the fluldity of the _ 18 -~ 077970 mixture before setting but the lower the strength a~ter set. Water is essential to promote reaction of silicate polymers and salts of the polyvalent metals.
Flyash and other pozzolanic materials may be used as fillers to perform the same function that sand performs as outlined above.
Concretes may be prepared by adding gravel and rock to mortar formulations of the present invention. Concretes prepared accordingly exhibit very low water absorption when cured, even a~ter exposure to several hundred degree temperature. Consequently, the formulations of the present invention are uniquely suited for use in formulation build-ing materials that are or may all be "low energy produced"
in that no calcining or kiln processing is required to prepare the raw materials for the concrete, espec~ally when the aforementioned sodium hydroxide-silica reaction is employed to generate sodium silicate.
As may be seen from the examples, formulation of cement compositions according to the present invention by using diferent polyvalent metal compounds results in different formulations having varying activation temperatures. For example, the formulation o Example 1 has an activation o 150 F. and the ~ormulation of Example 3 has an activation temperature o~ 225 F. As a result, it will now be appar~nt that a formulation may be selected having a specific activation temperature such that the formulation is uniquely adaptable for use in temperature environments wherein the cement remains mobile until subjec~ed to a temperature high enough to activate setting and curing reactions. For example~ various ~ormulations of cement according to the present invention may be used in cementing pipe or casing within bore holes of wells drilled in the earth. Since temperature at a given point within a bore hole depends on depth of the well~ the formulation used to cement the casing may be selected by determining temperature of the bore hole and compar~ng that temperature to the activated temperature of the various ~ormulations of the present in~ention. For example, ~f the downhole temperature is approximately 150 F~, the formulation o~ Example 1 may be used whereby the bore hole temperature o~ 150 ~. causes the cement to set when ~inally placed in the well. How-ever, below ~uch temperature the cement remains mobile or pumpable ~or long periods o~ time relative to conventional Portland cements. In the same way, other cements from among formulations of the present invention may be selected for use in bore holes having different temperatures, necessitating use of formulations having corresponding activation temper-atures.
In using cement formulations of the present invention for cementing casing in wells, the cement is prepared as explained elsewhere herein. The cement may be prepared at the well site although, advantageously, it may be prepared at points remote from the well site and shipped to the site w~thout setting. ~inimal agitation is required while holding the cement prior to use, the agitation serving merely to prevent stratification of the material. This feature of formulations according to the present invention is extremely significant when considering the mixing and trans-portation problems of con~entional P~rtla~d cements.
The cement i5 then pumped into the annular space ~etween - 20 _ ~
the string of pipe or casln~ and the walls of the bore hole as in conventional processes. However, the need for standby pumping equipment is not as critical since the cement of the present invention will not set for several hours after being subjected to the ac~ivation te~perature, thereby allowing adequate time for repair or replacement of the pumping equipment. Once in place in the well, pumping stops and the cement is allowed to set due to temperature of the bore hole or by passage of time or both. In thi~ connection, cement formulations of the present invention having activation temperatures substantially lower than temperature of the bore hole may be used although shorter periods of time than those described in the examples will be experienced for setting and curing to take place. In any event, the ultimate strengths obtainable by the present cement are at least as great as those obtained by conventional Portland cements while the shear bond strength exceed those of Portland , cement as indicated in the examples. Conse~uently, the ; 20 cement formulations of the present invention provide adhesive strengths that greatly exceed those of conventional Portland cements and thereby uniquely adapt formulatlons of the present invention for use in high temperature bore holes such as geothermal wells and the like.
Still other uses of formulations according to the present invention may ~e made depending on temperature requirements and length of time available for setting and curing. It will now be apparent to those s~lled in the art that formulations of the in~ention may be used for a variety o~ applications~
:`
1~77970 The present invention, therefore~ is well adapted to --carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While presently preferred embodiments of the invention have been given for the purpose o disclosure, numerous changes in the details of formulations and operation of the methods involved can be made which will readily suggest themselves to those skilled in the art and which are encompassed within the scope of the invention and the scope o~ the appended claims.
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Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A cement composition consisting essentially of (a) one of a polyvalent metal oxide, hydroxide, salt of low solubility or mixture thereof, (b) water, (c) a silica source hydratable under time and temperature conditions through reactions wherein the silica becomes available for chemical combination with the polyvalent metal ion source (a) upon application of heat, and (d) a water reducing reagent comprising a spray dried sodium silicate hydrate powder.
2. The cement composition of claim 1 wherein the polyvalent metal ion source (a) is selected from the group consisting of the oxides of zinc, magnesium iron, aluminum, manganese, titanium, zirconium, vanadium and hafnium, the hydroxide of aluminum, the carbonates of zinc and magnesium and the phosphates of magnesium and aluminum and combinations thereof.
3. The cement composition of claim 1 wherein the silica source is one selected from the group consisting of a clay, silica flour, silica sand and the combinations thereof.
4. A cement composition characterized as a pumpable slurry susceptible to a hydrothermally initiated cure, consisting essentially of (a) from about 50 to about 15 parts by weight of a polyvalent metal ion source, (b) from about 15 to about 20 parts by weight of water per hundred parts by weight of total solids, (c) from about 60 to about 100 parts by weight of a silica source hydratable under time and temperature conditions through reactions wherein the silica becomes available for chemical combination with the polyvalent metal ion source (a) upon application of heat, and (d) from about 5 to 15 parts by weight of a water reducing reagent comprising a spray dried sodium silicate hydrate powder.
5. The cement composition of claim 4 wherein, more specifically, (a) the polyvalent metal ion source consists of about 7 parts by weight of zinc oxide, (b) water is present in the amount of about 17 parts by weight per hundred parts by weight of total solids, (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour, (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
6. The cement composition of claim 4 including additionally up to about 25 parts by weight flyash.
7. The cement composition of claim 4 wherein, more specifically, (a) the polyvalent metal ion source consists of about 7 parts by weight of reagent grade aluminum hydroxide, (b) water is present in the amount of about 17 parts by weight per hundred parts by weight of total solids, and (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour, (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
8. The cement composition of claim 4 wherein, more specifically, (a) the polyvalent metal ion source consists of about 7 parts by weight of commercial grade aluminum hydroxide, (b) water is present in the amount of about 20 parts by weight, and (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
9. The cement composition of claim 4 wherein, more specifically, (a) the polyvalent metal ion source consists of about 7 parts by weight aluminum oxide, (b) water is present in the amount of about 17 parts by weight per hundred parts by weight of total solids, (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour, (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
10. A method of cementing a string of pipe in a bore hole, comprising the steps of (1) preparing a cement composition consisting essentially of (a) one of a polyvalent metal oxide hydrox-ide, salt or mixture thereof, (b) water, (c) a silica source hydratable under time and temperature conditions through reactions wherein the silica is available for chemical combination with the poly-valent metal ion source (a) upon appli-cation of heat, and (d) a water reducing reagent comprising a spray dried sodium silicate hydrate powder.
(2) pumping the cement composition into an annular space between the string of pipe and the walls of the bore hole, and (3) allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
(2) pumping the cement composition into an annular space between the string of pipe and the walls of the bore hole, and (3) allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
11. The method of claim 10 wherein the cement composition prepared in step (1) the polyvalent metal oxide, hydroxide, salt or mixture thereof is selected from the group consisting of the oxides of zinc, magnesium, iron, aluminum, manganese, titanium, zirconium, vanadium and hafnium, the hydrozide of aluminum, the carbonates of zinc and magnesium and the phosphates of magnesium and aluminum, and combinations thereof.
12. The method of claim 10 wherein in the cement composition prepared in step (1) the silica source is one selected from the group consisting of a clay, silica flour and silica sand or combinations thereof.
13. The method of cementing a string of pipe in a bore hole, comprising the steps of, (1) preparing a cement composition as a pumpable slurry susceptible of a hydrothermally initiated cure, consisting essentially of (a) from about 5 to about 15 parts by weight of a polyvalent metal ion source, (b) from about 15 to about 20 parts by weight of water per hundred parts by weight of total solids, (c) from about 60 to about 100 parts by weight of a silica source hydratable under time and temperature conditions through reactions wherein the silica becomes available for chemical combin-ation with the polyvalent metal ion source (a) upon application of heat, and (d) from about 5 to about 15 parts by weight of a water reducing reagent comprising a spray dried sodium silicate hydrate powder.
(2) pumping the cement composition into an annular space between the string of pipe and the walls of the bore hole, and (3) allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
(2) pumping the cement composition into an annular space between the string of pipe and the walls of the bore hole, and (3) allowing the cement to set due to the temperature of the bore hole or by passage of time or both.
14. The method of claim 13 wherein, more specifically, (a) the polyvalent metal ion source consists of about 7 parts by weight of zinc oxide, (b) water is present in the amount of about 17 parts by weight per hundred parts by weight of total solids, (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour, (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
15. The method of claim 13 including, additionally, up to about 25 parts by weight flyash.
16. The method of claim 13 wherein, more specifically, (a) the polyvalent metal ion source consists of about 7 parts by weight of reagent grade aluminum hydroxide, (b) water is present in the amount of about 17 parts by weight per hundred parts by weight of total solids, (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour, (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
17. The method of claim 13 wherein, more specifically, (a) the polyvalent metal ion source consists of about 10 parts by weight of commercial grade aluminum hydroxide, (b) water is present in the amount of about 17 parts by weight per hundred parts by weight of total solids, (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour, (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
18. The method of claim 13 wherein, more specifically, (a) the polyvalent metal ion source consists of about 7 parts by weight aluminum oxide, (b) water is present in the amount of about 17 parts by weight per hundred parts by weight of total solids, (c) the silica source includes, (i) about 50 parts by weight sand, (ii) about 25 parts by weight silica flour, (iii) about 10 parts by weight anhydrous sodium silicate powder, and (d) the water reducing reagent consists of about 10 parts by weight of spray dried hydrated sodium silicate powder.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA259,372A CA1077970A (en) | 1976-08-18 | 1976-08-18 | Hydrothermal cement |
| CA340,526A CA1086782A (en) | 1976-08-18 | 1979-11-23 | Hydrothermal cement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA259,372A CA1077970A (en) | 1976-08-18 | 1976-08-18 | Hydrothermal cement |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1077970A true CA1077970A (en) | 1980-05-20 |
Family
ID=4106683
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA259,372A Expired CA1077970A (en) | 1976-08-18 | 1976-08-18 | Hydrothermal cement |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1077970A (en) |
-
1976
- 1976-08-18 CA CA259,372A patent/CA1077970A/en not_active Expired
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