Patent Application
20110073311
The present invention broadly relates to well cementing. More particularly the invention relates to the use of geopolymers, to pumpable geopolymer formulations and the related methods of placing the geopolymer formulations in a well using conventional or unconventional cementing techniques.
Geopolymers are a novel class of materials that are formed by chemical dissolution and subsequent recondensation of various aluminosilicate oxides and silicates to form an amorphous three-dimensional framework structure. Therefore, a geopolymer is a three-dimensional aluminosilicate mineral polymer. The term geopolymer was proposed and first used by J. Davidovits (Synthesis of new high-temperature geopolymers for reinforced plastics/composites, SPE PACTEC' 79, Society of Plastics Engineers) in 1976 at the IUPAC International Symposium on Macromolecules held in Stockholm.
Geopolymers based on alumino-silicates are designated as poly(sialate), which is an abbreviation for poly(silicon-oxo-aluminate) or (—Si—O—Al—O—)n (with n being the degree of polymerization). The sialate network consists of SiO4 and AlO4 tetrahedra linked alternately by sharing all the oxygens, with Al3+ and Si4+ in IV-fold coordination with oxygen. Positive ions (Na+, K+, Li+, Ca2+ . . . ) must be present in the framework cavities to balance the negative charge of Al3+ in IV-fold coordination.
The empirical formula of polysialates is: Mn {—(SiO2)z—AlO2}n, w H2O, wherein M is a cation such as potassium, sodium or calcium, n is a degree of polymerization and z is the atomic ratio Si/Al which may be 1, 2, 3 or more, until 35 as known today.
The three-dimensional network (3D) geopolymers are summarized in the table 1 below.
The properties and application fields of geopolymers will depend principally on their chemical structure, and more particularly on the atomic ratio of silicon versus aluminum. Geopolymers have been investigated for use in a number of applications, including as cementing systems within the construction industry, as refractory materials and as encapsulants for hazardous and radioactive waste streams. Geopolymers are also referenced as rapid setting and hardening materials. They exhibit superior hardness and chemical stability.
Various prior art disclose the use of geopolymer compositions in the construction industry. In particular U.S. Pat. No. 4,509,985 discloses a mineral polymer composition employed for the making of cast or molded products at room temperatures, or temperatures generally up to 120° C.; U.S. Pat. No. 4,859,367, U.S. Pat. No. 5,349,118 and U.S. Pat. No. 5,539,140 disclose a geopolymer for solidifying and storing waste material in order to provide the waste material with a high stability over a very long time, comparable to certain archeological materials, those waste materials can be dangerous or potentially toxic for human beings and the natural environment; or U.S. Pat. No. 5,356,579, U.S. Pat. No. 5,788,762, U.S. Pat. No. 5,626,665, U.S. Pat. No. 5,635,292 U.S. Pat. No. 5,637,412 and U.S. Pat. No. 5,788,762 disclose cementitious systems with enhanced compressive strengths or low density for construction applications. Patent application WO2005019130 is the first to highlight the problem of controlling the setting time of the geopolymer system in the construction industry. Effectively, as the geopolymers have a rapid set time, a retarder could be used to lengthen this set time.
However none of the prior art has discussed geopolymers for application in the oilfield industry. And if WO2005019130 has the merit to disclose a specific type of novel family of geopolymers with some retarding effects on the set time for the construction industry, no real control of the set time is proposed for all the other geopolymer systems. In addition further major technical challenges affect potential cementing systems to be used in the oilfield industry. These problems are, for example the control of the thickening and setting times for large temperature and density ranges for the geopolymer slurry, the mixability and also the pumpability of such slurry. Other properties have also to be considered, such as the compressive strength and permeability of the set geopolymer material. Therefore, it would be desirable to produce geopolymers solving those problems and having still good properties for oilfield applications.
In one embodiment the invention discloses a suspension comprising an aluminosilicate source, a carrier fluid, an activator taken from the list constituted by: a metal silicate, a metal aluminate, an alkali activator or a combination thereof, and wherein the suspension is a pumpable composition in the oilfield industry and the suspension is able to set under well downhole conditions. All the three components do not need necessarily to be added separately: for example the activator can be already within a carrier fluid. So, the aluminosilicate source can be in the form of a solid component; the metal silicate can be in the form of a solid or of a mix of metal silicate within a carrier fluid; the activator can be in the form of a solid or of a mix of activator within a carrier fluid. Importance is to have a carrier fluid to make suspension if aluminosilicate source, metal silicate and activator are all in solid state. If aluminosilicate source, metal silicates are in solid state and activator is in liquid state, activator is considered to already have a carrier fluid within. Further, as it is understood, unicity of the carrier fluid is not required, two or more carrier fluids can be used. The geopolymeric composition has such rheological properties that the suspension of said geopolymeric composition has a good pumpability and stability. A pumpable composition in the oilfield industry has a rheology lesser than or equal to 300 cP, preferably in other embodiment lesser than or equal to 250 cP, more preferably in another embodiment lesser than or equal to 200 cP. Further, the suspension made is a stable suspension. The geopolymeric composition is mixable and pumpable; therefore applications in the oilfield industry are possible.
To control the setting time of the geopolymeric composition the alkali activator is chosen with a given pH, and/or a retarder is added and/or an accelerator is added to the suspension of said geopolymeric composition. The alkali activator can be generally an alkali metal hydroxide, more preferably a sodium or potassium hydroxide; it can be also a carbonate material. The retarder is selected from the group constituted of boron containing compound, lignosulfate, sodium gluconate, sodium glucoheptonate, tartaric acid and phosphorus containing compounds. Preferably, the retarder is an anhydrous or hydrated alkali metal borate or a pure oxide of boron. More preferably, the retarder is a sodium pentaborate decahydrate, boric acid, or borax. The accelerator is an alkali metal preferably: a lithium or potassium containing compound. Preferably the accelerator is a salt of lithium. More preferably, the accelerator is lithium chloride. The control of the setting time is here efficient from 20° C. to 200° C. Sodium pentaborate decahydrate and borax are able to control setting time from 20° C., preferably from 25° C. to 150° C.
To control the setting time of the geopolymer composition, the type of alumino silicate is specifically chosen depending of the temperature application.
To improve the rheology of the suspension, aluminum containing compounds as bauxite, aluminum oxide, aluminum salts and magnesium silicate are added.
To improve the set material strength, reinforcing agent or agents are added as fibers (wollastonite), earth alkali compounds as calcium hydroxide, magnesium silicate.
To control the density of the geopolymeric composition, a lightweight particle and/or a heavyweight material can be added. The lightweight particles also called fillers are selected from the group constituted of: cenospheres, sodium-calcium-borosilicate glass, and silica-alumina microspheres. The heavy particles also called the weighting agents are typically selected from the group constituted of: manganese tetraoxide, iron oxide (hematite), barium sulfate (barite), silica and iron/titanium oxide (ilmenite). The geopolymeric compositions can also be foamed by foaming the suspension of said geopolymeric composition with a gas as for example air, nitrogen or carbon dioxide. The geopolymeric composition can further comprise a gas generating additive which will introduce the gas phase in the suspension. Preferably, the density of the suspension of said geopolymeric slurry compositions varies between 1 gram per cubic centimeter and 2.5 grams per cubic centimeter, more preferably between 1.2 grams per cubic centimeter and 1.8 grams per cubic centimeter.
In a second embodiment, the suspension of said geopolymeric composition can further comprise a mixture of two or more aluminosilicate source. In a further other embodiment, the suspension of said the geopolymeric composition can comprise a second binder component which may be a conventional cementing material such as Portland cement, micro-cement or silica fume.
In a third embodiment, the suspension of said geopolymeric composition can comprise a gas phase so the gas phase or part of the gas phase remains in the geopolymeric composition. For example, the gas phase can be a water-immiscible dispersed nitrogen phase.
In a fourth embodiment, the suspension of said geopolymeric composition can comprise a water-immiscible phase. For example, this can be a water-immiscible dispersed oil-based phase.
In a fifth embodiment, the geopolymeric composition further comprises an additive selected from the group constituted of: an activator, an antifoam, a defoamer, silica, a fluid loss control additive, a flow enhancing agent, a dispersant, a rheology modifier, a foaming agent, a surfactant and an anti-settling additive.
The geopolymeric composition according to the invention are preferably poly(sialate), poly(sialate-siloxo) or poly(sialate-disiloxo). More preferably, the geopolymeric composition are poly(sialate-siloxo) components and therefore the silicon to aluminum atomic ratio is substantially equal to two, between 1.8 and 2.8.
In another aspect of the invention is a suspension comprising an aluminosilicate source, a carrier fluid, an activator taken from the list constituted by: a metal silicate, a metal aluminate, an alkali activator, or a combination thereof, and a retarder able to retard the thickening and/or the setting times of the suspension and/or an accelerator able to accelerate the thickening and/or the setting times of the suspension, wherein the metal is an alkali metal and the oxide molar ratio M2O/SiO2 is greater than 0.20 wherein M is the metal.
When the retarder is used, it is preferably a boron containing compound and the suspension of said geopolymeric composition has preferably an oxide molar ratio B2O3/H2O of less than 0.03.
When the accelerator is used, it is preferably a lithium or potassium containing compound. The suspension of said geopolymeric composition has preferably an oxide molar ratio Li2O/H2O of less than 0.2. More preferably, the geopolymeric slurry composition has an oxide molar ratio Li2O/H2O of less than or equal to 0.1.
The geopolymeric composition according to the invention uses aluminosilicate source which is selected from the group constituted of ASTM type C fly ash, ASTM type F fly ash, ground blast furnace slag, calcined clays, partially calcined clays (such as metakaolin), aluminium-containing silica fume, natural aluminosilicate, synthetic aluminosilicate glass powder, zeolite, scoria, allophone, bentonite and pumice. Preferably, the geopolymeric composition is made with metakaolin, kaolin, ground granulated blast furnace slag and/or fly ash.
The geopolymeric composition according to the invention uses a metal silicate, with the metal selected from the group constituted of lithium, sodium, potassium, rubidium and cesium. Preferably, the metal is sodium or potassium. In another embodiment, the metal silicates can be replaced by ammonium silicates. The metal silicate in another embodiment can be encapsulated.
The geopolymeric composition according to the invention uses for the alkali activator, for example an alkali metal hydroxide. Preferably, the alkali metal hydroxide is sodium or potassium hydroxide. The alkali activator and/or the metal silicate may be encapsulated. Alkali carbonates can also be used as alkali activator. Also, the alkali activator in another embodiment can be encapsulated.
The geopolymeric composition according to the invention uses for the carrier fluid preferably an aqueous solution such as fresh water.
In another aspect of the invention a method to control the setting time of a geopolymeric suspension for oilfield applications is disclosed. The method comprises the step of providing said suspension within a carrier fluid by adding: (i) a retarder and/or an accelerator; (ii) an aluminosilicate source; (iii) an activator taken in the list constituted by: a metal silicate, a metal aluminate, an alkali activator, or a combination thereof. The previous steps can be realized in another order. The geopolymer compositions of the invention prepared according to the method have controllable setting times at temperatures ranging from 20° C. to at least 200° C. The geopolymeric composition used is the same as disclosed above. And, the alkali activator is selected from the group constituted of: sodium hydroxide and potassium hydroxide; the retarder is selected from the group constituted of boron containing compound, lignosulfate, sodium gluconate, sodium glucoheptonate, tartaric acid and phosphorus containing compounds.
To control the thickening and/or the setting times of the geopolymeric composition, the nature and/or the pH and/or the concentration of the activator and/or the concentration of the metal silicate is changed. By increasing the concentration of the activator, the setting time is shortened and by changing the nature and/or pH, different setting times are obtained. To control the thickening time of the geopolymeric composition the nature and/or the concentration of the retarder is changed. By increasing the concentration of the retarder, the setting time is lengthened and by changing the nature, different setting times are obtained. In the same way, to control the setting time of the geopolymeric composition the nature and/or the concentration of the accelerator is changed. By increasing the concentration, the setting time is shortened and by changing the nature, different setting times are obtained. As it can be seen, three solutions exist to control the setting time, use of a special activator, use of a retarder, or use of an accelerator. The three solutions can be used separately or in combination. Sometimes, the use of a special activator does not give sufficiently long setting time and the use of a retarder may be preferred. Similarly the use of a special activator may not give sufficiently short setting time and the use of an accelerator would be preferred.
In another aspect of the invention a method to control the density of a suspension for oilfield industry is disclosed. The method comprises the step of providing said suspension within a carrier fluid by adding: (i) lightweight particles and/or heavy particles; (ii) an aluminosilicate source; (iii) an alkali activator taken in the list constituted by: a metal silicate, a metal aluminate, an alkali activator, or a combination thereof. The previous steps can be realized in another order. Still, in another aspect of the invention the method further comprises the step of adding a retarder and/or an accelerator to the suspension. Still, in another aspect of the invention the method further comprises the step of foaming the suspension of said geopolymeric composition.
In another aspect of the invention a method to control the density of a suspension for oilfield industry is disclosed, the method comprises the step of: (i) providing said suspension within a carrier fluid by mixing an aluminosilicate source, a metal silicate and an activator taken in the list constituted by: a metal silicate, a metal aluminate, an alkali activator, or a combination thereof in a carrier fluid, (ii) foaming the suspension of said geopolymeric composition. Still, in another aspect of the invention the method further comprises the step of adding a retarder and/or an accelerator to the suspension.
The method to control the density of geopolymer compositions of the invention applies for density range varying between 1 gram per cubic centimeter and 2 grams per cubic centimeter, but could also be applied to density range varying between 0.8 gram per cubic centimeter and 2.5 grams per cubic centimeter.
In another aspect of the invention a method to place a geopolymeric composition in a borehole and isolate subterranean formations is disclosed, the method comprises the step of: (i) providing a suspension as described above (ii) pumping said suspension into the borehole, and (iii) allowing said suspension to set under wellbore downhole conditions and thereby form the geopolymeric composition.
In another embodiment, the step of providing a suspension of said geopolymeric composition further comprises adding a retarder and/or an accelerator and/or an activator. Effectively, it can be useful to lengthen the set of the geopolymeric composition by adding a retarder as seen above and/or it can be useful to accelerate the set of the geopolymeric composition by adding an accelerator as seen above.
Still, in another embodiment, the method comprises the step of activating in situ the suspension of said geopolymeric composition. Effectively, the method also applies if activation has to be realized downhole in the well, the activation does not necessarily refer to the alkali activator. Effectively, in a first embodiment the activation refers to activation via the alkali activator, the alkali activator is encapsulated as described previously or is released with a downhole device. In a second embodiment, the activation refers to any type of activation when various additives that need activation are used, as for example activation can be physical (by heat, UV radiation or other radiations); the activation can be made also with chemical components encapsulated and released at a predefined time or event. The capsule can be self destructed as previously explained or can be destroyed with help of stress and/or sonic perturbation.
In the first embodiment, the geopolymeric composition is retarded with a sufficiently long setting time so an activation has to be done to provoke the set of geopolymeric composition. The activation is made here by the release of an activator. This release is realized downhole, in situ, by adding the activator directly to the suspension of said geopolymeric composition and/or if the activator is encapsulated in the suspension of said geopolymeric composition by break of the capsules.
Still, in another embodiment, the method comprises the step of activating the suspension of said geopolymeric composition just before use. For example, an inactivated suspension of geopolymer composition is made so that said suspension is stable for a long time. Said composition is storable, transportable and accessorily perishable after a period varying between one day and some months, preferably some days and three months. The storable suspension is taken to rig site in liquid form and is activated before pumping or downhole in situ as explained previously.
Preferably, the step of pumping the suspension of said geopolymeric composition is made with conventional well cementing equipment, familiar to those skilled in the art. The method applies as a primary cementing technique for cementing wells where the geopolymeric composition is pumped down a pipe until the shoe where it then flows up the annular space between the casing/liner and the borehole. A reverse circulation cementing technique can also be used for placing the geopolymer suspension at the desired depth in the borehole.
Further, the pumping and placement of geopolymer suspension below surface encompasses several other conventional cementing techniques such as the grouting of platform piles, skirts or the like, the squeeze operation for repair or plugging of an undesired leak, perforation, formation or the like, and the setting of a geopolymer composition plug for any purpose of a cement plug.
The methods apply also to the placement of the geopolymeric composition to squeeze a zone of the borehole. The methods can apply for water well, geothermal well, steam injection well, Toe to Heel Air Injection well or acid gas well. As such the composition can withstand temperature above 250° C., even above 450° C. and 550° C.
Further embodiments of the present invention can be understood with the appended drawings:
According to the invention, the geopolymer formulations involve the use of an aluminosilicate source, a metal silicate and an alkali activator in a carrier fluid at near-ambient temperature. The carrier fluid is preferably a fresh water solution. As it has been said previously, all the four components do not need necessarily to be added separately: for example the alkali activator can be already within water. So, the aluminosilicate source can be in the form of a solid component; the metal silicate can be in the form of a solid or of an aqueous solution of metal silicate; the alkali activator can be in the form of a solid or of an aqueous solution of alkali activator.
Formation of the geopolymer concrete involves an aluminosilicate source. Examples of aluminosilicate source from which geopolymers may be formed include ASTM type C fly ash, ASTM type F fly ash, ground blast furnace slag, calcined clays, partially calcined clays (such as metakaolin), aluminium-containing silica fume, natural aluminosilicate, synthetic aluminosilicate glass powder, zeolite, scoria, allophone, bentonite and pumice. These materials contain a significant proportion of amorphous aluminosilicate phase, which reacts in strong alkali solutions. The preferred aluminosilicates are fly ash, metakaolin, kaolin and blast furnace slag. Mixtures of two or more aluminosilicate sources may also be used if desired. In another embodiment, the aluminosilicate component comprises a first aluminosilicate binder and optionally one or more secondary binder components which may be chosen in the list: ground granulated blast furnace slag, Portland cement, kaolin, metakaolin or silica fume.
Formation of the geopolymer material could involve also, an alkali activator. The alkali activator is generally an alkali metal hydroxide. Alkali metal hydroxides are generally preferred as sodium and potassium hydroxide. The metal hydroxide may be in the form of a solid or an aqueous mixture. Also, the alkali activator in another embodiment can be encapsulated. The alkali activator when in solid and/or liquid state can be trapped in a capsule that will break when subject for example, to stress on the capsule, to radiation on the capsule. Also, the alkali activator when in solid and/or liquid state can be trapped in a capsule that will naturally destroy due to the fact that for example, the capsule is made with biodegradable and/or self destructive material. Also, the alkali activator when in liquid state can be adsorbed onto a porous material and will be released after a certain time or due to a predefined event.
Formation of the geopolymer material could involve also, a metal silicate or aluminate or a combination of different metal silicates or aluminate. The metal silicate is generally an alkali metal silicate. Alkali metal silicates, particularly sodium silicate or potassium silicate, are preferred. Sodium silicates with a molar ratio of SiO2/Na2O equal to or less than 3.2 are preferred. Potassium silicates with a molar ratio of SiO2/K2O equal to or less than 3.2 are preferred. Also, the metal silicate in another embodiment can be encapsulated.
The method of the invention is applicable to the oilfield, preferably in completion of the well bore of oil or gas wells. To be used in oilfield application, a pumpable geopolymer formulation is formed where the components are mixed with a carrier fluid. Various additives can be added to the suspension and the suspension is then pumped into the well bore. The suspension is then allowed to set up in the well to provide zonal isolation in the well bore.
A typical property of geopolymer systems is their ability to set without delay after mixing. However for oilfield applications, mixable and pumpable geopolymer suspension is needed. For this reason, a way to retard the thickening of the geopolymer suspension or a way to control thickening times of the geopolymer is required.
A large family of retarders allowing delay in the set of the geopolymer has been found. In table 2, the results of thickening time tests performed as per ISO 10426-2 Recommended Practice in a High Pressure High Temperature (HPHT) consistometer are reported. Such tests are performed to simulate the placement from surface to downhole of cement suspensions, at a defined Bottom Hole Circulating Temperature (BHCT). To realize such tests, a temperature heatup schedule is followed in order to mimic placement in a real well. For the tests performed at 57° C., the temperature is reached in 41 minutes and the final pressure is 33.8 MPa (4900 psi). For the tests performed at 85° C., the temperature is reached in 58 minutes and the final pressure is 55.1 MPa (8000 psi). For the tests performed at 110° C., the temperature is reached in 74 minutes and the final pressure is 75.9 MPa (11000 psi).
The retardation of geopolymeric formulations can be and is controlled at different BHCT by using either boron containing compounds as for example sodium pentaborate decahydrate, boric acid, borax, or lignosulphonate, or phosphorus containing compounds, or a mixture of them. Retardation of geopolymeric formulations will be sensitive to boron valence for boron containing compounds or phosphate valence for phosphorus containing compounds and/or to retarder concentration.
In table 3, the results obtained with Vicat apparatus with two boron-based retarders are presented. Vicat apparatus allows to measure when the setting of the material starts (IST) and ends (FST). It is based on the measurements of the penetration of a needle in a soft material. This apparatus is often used to realize pre-study at ambient temperature and atmospheric pressure.
Retardation of geopolymeric formulations is sensitive to temperature. However, two boron-based retarders (sodium pentaborate decahydrate and borax) are able to strongly retard different types of geopolymer suspensions even at 25° C.
Control of the thickening time can also be realized by other means. As an example the nature of the alkali activator and its pH have an impact on the thickening time. Table 4 illustrates the influence of the alkali activator on the thickening time of geopolymeric suspensions. It demonstrates the ability to select the alkali activator source according to the downhole conditions.
Control of the thickening and setting times by these methods of retardation can also be efficiently done with geopolymer having different silicon versus aluminum ratio.
Furthermore, depending on properties of the geopolymer, it can be suitable to accelerate thickening of the suspension. Table 5 illustrates the accelerating effect of lithium compounds on the thickening time of geopolymeric suspensions at temperature of 85° C. It demonstrates the ability of using lithium salts to control the thickening time of geopolymer suspensions.
7% bwob
2% bwob
Depending on the properties of the geopolymer and on properties of the well, a real control of the thickening time of the suspension can be established. To increase the thickening time, nature of the retarder used can be changed, concentration of the retarder can be increased, nature of the alkali activator used can be changed, and nature of the aluminosilicate used can be changed.
Further, when use in oilfield application is sought, the geopolymer suspension has to be pumpable. Table 6 hereunder illustrates the rheological properties of geopolymer suspensions measured at a bottom hole circulating temperature (BHCT) of 60° C. Rheological values demonstrate the pumpability and the stability of geopolymeric suspensions for application in the oilfield industry.
Further, the addition of aluminum containing compounds as aluminum oxide with optimized particle size or magnesium silicate improve rheological properties of geopolymer suspensions. Table 7 hereunder illustrates the rheological properties of geopolymer suspensions measured at a bottom hole circulating temperature (BHCT) of 60° C. Rheological values demonstrate the improved mixability and pumpability of geopolymeric suspensions for application in the oilfield industry.
Sample A7 is made by adding the blend comprising 309 g of metakaolin and 270 g of sodium silicate and 7 g of sodium pentaborate and 31 g of potassium hydroxide in 295 mL of water under mixing. Sample A7 is then tested by measuring the rheological properties of the suspension after mixing and after conditioning at 60° C. according to the ISO 1026-2 standard procedure.
Sample B7 is made by adding the blend comprising 309 g of metakaolin and 270 g of sodium silicate and 7 g of sodium pentaborate and 31 g of aluminum oxide and 31 g of potassium hydroxide in 287 mL of water under mixing. Sample B7 is then tested by measuring the rheological properties of the suspension after mixing and after conditioning at 60° C. according to the ISO 1026-2 standard procedure.
Sample C7 is made by adding the blend comprising 309 g of metakaolin and 270 g of sodium silicate and 7 g of sodium pentaborate and 31 g of magnesium silicate and 31 g of potassium hydroxide in 274 mL of water under mixing. Sample C7 is then tested by measuring the rheological properties of the suspension after mixing and after conditioning at 60° C. according to the ISO 1026-2 standard procedure.
Table 8 shows the difference of setting time according to the conditions of setting. The geopolymer formulation will set more rapidly in static than in dynamic conditions. Also normally, the geopolymer suspension should set rapidly after placement.
Also, when use in oilfield application is sought, the geopolymer suspension has to have a large range of densities. As presented in table 9, the tested geopolymer formulations propose a density range between 1.45 g/cm3 [12.1 lbm/gal] up to 1.84 g/cm3 [15.4 lbm/gal] either in reducing the water content, or in adding fillers.
Further, to broaden the density range, either lightweight particles are added to reach lower densities or heavy particles to reach higher densities. The lightweight particles typically have density of less than 2 g/cm3, and generally less than 1.3 g/cm3. By way of example, it is possible to use hollow microspheres, in particular of silico-aluminate, known as cenospheres, a residue that is obtained from burning coal and having a mean diameter of about 150 micrometers. It is also possible to use synthetic materials such as hollow glass bubbles, and more particularly preferred are bubbles of sodium-calcium-borosilicate glass presenting high compression strength or indeed microspheres of a ceramic, e.g. of the silica-alumina type. The lightweight particles can also be particles of a plastics material such as beads of polypropylene. The heavy particles typically have density of more than 2 g/cm3, and generally more than 3 g/cm3. By way of example, it is possible to use hematite, barite, ilmenite, silica and also manganese tetroxide commercially available under the trade names of MicroMax and MicroMax FF.
Further, to broaden the density range, it is possible to foam the geopolymer composition. The gas utilized to foam the composition can be air or nitrogen, nitrogen being the most preferred. The amount of gas present in the cement composition is that amount which is sufficient to form a foam having a density in the range of from about 1 g.cm−3 to 1.7 g.cm−3 (9 to 14 lbm/gal).
In a further embodiment, other additives can be used with the geopolymer according to the present invention. Additives known to those of ordinary skill in the art may be included in the geopolymer compositions of the present embodiments. Additives are typically blended with a base mix or may be added to the geopolymer suspension. An additive may comprise an activator, an antifoam, a defoamer, silica, a fluid loss control additive, a flow enhancing agent, a dispersant, an anti-settling additive or a combination thereof, for example. Selection of the type and amount of additive largely depends on the nature and composition of the set composition, and those of ordinary skill in the art will understand how to select a suitable type and amount of additive for compositions herein.
In another embodiment, when various components are used with or within the geopolymer formulation, the particle size of the components is selected and the respective proportion of particles fractions is optimized in order to have at the same time the highest Packing Volume Fraction (PVF) of the solid, and obtaining a mixable and pumpable slurry with the minimum amount of water, i.e., at slurry Solid Volume Fraction (SVF) of 35-75% and preferably of 50-60%. More details can be found in European patent EP 0 621 247. The following examples do not constitute a limit of the invention but rather indicate to those skilled in the art possible combinations of the particle size of the various components of the geopolymer compositions of the invention to make a stable and pumpable suspension.
The geopolymeric composition can be a “trimodal” combination of particles: “large” for example sand or crushed wastes (average dimension 100-1000 micrometers), “medium” for example materials of the type of glass beads or fillers (average dimension 10-100 micrometers), “fines” like for example a micromaterial, or micro fly ashes or other micro slags (average dimension 0.2-10 micrometers). The geopolymeric composition can also be a “tetramodal” combination of particles type: with “large” (average dimension about 200-350 micrometers), “medium” glass beads, or fillers (average dimension about 10-20 micrometers), “fine” (average dimension about 1 micrometer), “very fine” (average dimension about 0.1-0.15 micrometer). The geopolymeric composition can also be a further combinations between the further categories: “very large”, for example glass maker sand, crushed wastes (average dimension superior to 1 millimeter) and/or “large”, for example sand or crushed wastes (average dimension about 100-1000 micrometers) and/or “medium” like glass beads, or fillers, or crushed wastes (average dimension 10-100 micrometers) and “fine” like, for example, micro fly ashes or other micro slags (average dimension 0.2-10 micrometer) and/or “very fine” like, for example, a latex or pigments or polymer microgels like a usual fluid loss control agent (average dimension 0.05-0.5 micrometer) and/or “ultra fine” like some colloidal silica or alumina (average dimension 7-50 nanometers).
The compressive mechanical properties of set geopolymer compositions was studied using systems after curing them for several days under high pressure and temperature in high pressure and high temperature chambers to simulate the conditions encountered in an oil or gas well.
Table 10 and 11 illustrate that geopolymer formulations proposed by this invention exhibit acceptable compressive strengths with low Young Modulus for oilfield applications with or without retarder.
Because, the compositions of the present invention exhibit good compressive strengths with low Young modulus, they would be very useful in oilfield applications.
Further, the addition of reinforcing agent or agents improve the set material strength. Table 12 illustrates that addition of calcium hydroxide improves the mechanical properties of the geopolymer suspension.
Sample A12 is made by adding the blend comprising 309 g of metakaolin and 270 g of sodium silicate and 7 g of sodium pentaborate and 31 g of aluminum oxide and 31 g of potassium hydroxide in 287 mL of water under mixing, following ISO 10426-2 mixing, pouring the suspension into moulds and placing the moulds in a curing chamber for 7 days at 60° C.—20.7 MPa [3000 psi], according to ISO 10426-2 procedure. Sample A12 is then tested by measuring the compressive strength and Young's modulus.
Sample B12 is made by adding 12 g of calcium hydroxide in the suspension A12, following ISO 10426-2 mixing, pouring the suspension into moulds and placing the moulds in a curing chamber for 7 days at 60° C.—20.7 MPa [3000 psi], according to ISO 10426-2 procedure. Sample B12 is then tested by measuring the compressive strength and Young's modulus.
The water permeability were measured for some prepared geopolymer compositions. The isolation properties of a set geopolymer was studied using systems which had passed several days under high pressure and temperature in high pressure and high temperature chambers to simulate the conditions encountered in an oil well.
Table 13 illustrates that geopolymer formulations proposed by this invention exhibit acceptable permeability for oilfield applications.
Because, the compositions of the present invention exhibit acceptable water permeability, oilfield applications are possible.
The methods of the present invention are useful in completing well, such as for example oil and/or gas well, water well, geothermal well, steam injection well, be to Heel Air Injection well, acid gas well, carbon dioxide injection or production well and ordinary well. Placement of the geopolymer composition in the portion of the wellbore to be completed is accomplished by means that are well known in the art of wellbore cementing. The geopolymer composition is typically placed in a wellbore surrounding a casing to prevent vertical communication through the annulus between the casing and the wellbore or the casing and a larger casing. The geopolymer suspension is typically placed in a wellbore by circulation of the suspension down the inside of the casing, followed by a wiper plug and a nonsetting displacement fluid. The wiper plug is usually displaced to a collar, located near the bottom of the casing. The collar catches the wiper plug to prevent overdisplacement of the geopolymer composition and also minimizes the amount of the geopolymer composition left in the casing. The geopolymer suspension is circulated up the annulus surrounding the casing, where it is allowed to harden. The annulus could be between the casing and a larger casing or could be between the casing and the borehole. As in regular well cementing operations, such cementing operation with a geopolymer suspension may cover only a portion of the open hole, or more typically up to inside the next larger casing or sometimes up to surface. This method has been described for completion between formation and a casing, but can be used in any type of completion, for example with a liner, a slotted liner, a perforated tubular, an expandable tubular, a permeable tube and/or tube or tubing.
In the same way, the methods of the present invention are useful in completing well, such as for example oil and/or gas well, water well, geothermal well, steam injection well, acid gas well, carbon dioxide well and ordinary well, wherein placement of the geopolymer composition in the portion of the wellbore to be completed is accomplished by means that are well known in the art of wellbore reverse circulation cementing.
The geopolymer composition can also be used in squeeze job and/or in remedial job. The geopolymer material is forced through perforations or openings in the casing, whether these perforations or openings are made intentionally or not, to the formation and wellbore surrounding the casing to be repaired. Geopolymer material is placed in this manner to repair and seal poorly isolated wells, for example, when either the original cement or geopolymer material fails, or was not initially placed acceptably, or when a producing interval has to be shut off.
The geopolymer composition can also be used in abandonment and/or plugging job. The geopolymer material is used as a plug to shut off partially or totally a zone of the well. Geopolymer material plug is placed inside the well by means that are well known in the art of wellbore plug cementing.
The geopolymer composition can also be used in grouting job to complete a part of the annulus as described in Well Cementing from Erik B. Nelson. The geopolymer material is used to complete down this annulus. Geopolymer material is placed inside the well by means that are well known in the art of wellbore cementing.
The geopolymer composition can also be used for fast-setting operation, in-situ operation. Effectively, the geopolymer composition can have a setting time perfectly controlled, allowing an instant setting when desired. For example, a retarder/accelerator combination can be added to the geopolymer composition to cause the system to be retarded for an extended period of time and then to set upon addition of an accelerator.
The geopolymer composition can also be a storable composition. As such, the suspension is over-retarder and is left intentionally in liquid phase. Said suspension is so, able to be stored and utilized in the well when needed.
According to other embodiments of the invention, the methods of completion described above can be used in combination with conventional cement completion.
The following examples will illustrate the practice of the present invention in its preferred embodiments.
Geopolymer composition is made in the amounts by weight of the total dry components as follows: 58.1% metakaolin and 41.9% sodium disilicate. Dry components are mixed with the appropriate amount of water, sodium hydroxide and additives. The specific gravity of the suspension is 1.53 g/cm3 [12.80 lbm/gal]. The geopolymer has the following oxide molar ratios:
SiO2/Al2O3=4.00
Na2O/SiO2=0.27
Na2O/Al2O3=1.07
H2O/Na2O=17.15
Geopolymer composition is made in the amounts by weight of the total dry components as follows: 28.5% metakaolin, 20.6% sodium disilicate and 50.9% of a blend of silica particles. Dry components are mixed with the appropriate amount of water, sodium hydroxide and additives. The specific gravity of the suspension is 1.84 g/cm3 [15.40 lbm/gal]. The geopolymer matrix has the following oxide molar ratios:
SiO2/Al2O3−4.00
Na2O/SiO2=0.27
Na2O/Al2O3=1.07
H2O/Na2O=17.15
Geopolymer composition is made in the amounts by weight of the total dry components as follows: 35.2% metakaolin and 64.2% potassium disilicate. Dry components are mixed with the appropriate amount of water, potassium hydroxide and additives. The specific gravity of the suspension is 1.78 g/cm3 [14.91 lbm/gal]. The geopolymer matrix has the following oxide molar ratios:
SiO2/Al2O3=4.00
K2O/SiO2=0.27
K2O/Al2O3=1.07
H2O/K2O=17.46
Geopolymer composition is made in the amounts by weight of the total dry components as follows: 83.3% standard fly ash type F and 16.7% sodium disilicate. Dry components are mixed with the appropriate amount of water, sodium hydroxide and additives. The specific gravity of the suspension is 1.66 g/cm3 [13.83 lbm/gal]. The geopolymer has the following oxide molar ratios:
SiO2/Al2O3=5.60
Na2O/SiO2=0.3
Na2O/Al2O3=1.08
H2O/Na2O=13.01
| Number | Date | Country | Kind |
|---|---|---|---|
| 08290157.0 | Feb 2008 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/001093 | 2/17/2009 | WO | 00 | 12/6/2010 |
