BR112019024043B1 - GELIZED COMPOSITION AND COMPOSITION - Google Patents

Abstract

Composition useful for underground gas or water shutoff applications includes organosilane-modified colloidal silica and an accelerator. The accelerator includes one or more organic or inorganic salts. Method of using the composition, which includes organosilane-modified colloidal silica and an accelerator, includes forming a fluid system that flows into a formation in an underground zone, such as through a wellbore, wherein the composition forms a gel to obstruct the formation and close off the flow of water to the wellbore.

Description

PRIORITY CLAIM

[001] The present application claims priority to North American Patent Application No. 62/506,193, filed on May 15, 2017, European Patent Application No. 17175344.5, filed on June 9, 2017, and European Patent Application No. ° 18166420.2, filed on April 9, 2018, the contents of which are fully incorporated herein by reference.

FIELD OF INVENTION

[002] The present invention relates to oil well operations, such as water control in oil well applications. Particularly, in some embodiments, the present invention relates to a composition that can block (or close) the entry of water or gas into an underground zone, such as a wellbore or oil or gas well. In some embodiments, the present invention relates to uses of the composition, for example, in gas or oil field applications, particularly to reduce or prevent the ingress of water or gas into an underground zone, such as an extraction well. The present invention is particularly suitable for use in underground areas under high temperature.

BACKGROUND OF THE INVENTION

[003] A common problem experienced during the extraction of mineral hydrocarbons (e.g., crude oil and natural gas) from underground reservoirs is the simultaneous extraction of water. Water occurs naturally in oil and gas wells and reservoirs, for example from underlying aquifers or injection wells, and can mix and be extracted with the hydrocarbons produced. Simultaneous extraction of water together with mineral hydrocarbons requires expensive separation, treatment and disposal, and in many cases involves reinjection back into the well. Water cut is the ratio between the amount of water extracted and the total amount of fluids extracted from the extraction well. It is desirable to minimize the amount of water that is brought to the surface, i.e. minimize water cut.

[004] Similar issues arise in oil wells/well holes with unwanted gas ingress, as the gas must be separated and burned before feeding the oil to relevant storage prior to shipment or fed into a connected distribution pipeline. In many operations, gas handling capabilities are not readily available, so simultaneous gas production is ideally minimized.

[005] There are many ways in which water and gas can enter an underground zone, such as a wellbore or reservoir, during the extraction of hydrocarbons, for example, through the formation of porous rocks such as sedimentary layers or by through networks of fissures or cracks that connect to a water or gas source. Various chemical and mechanical treatments can be used to prevent (e.g., close) or at least reduce the ingress of water or gas. Chemical treatments include the use of gels, such as gels based on colloidal silica or gels based on polyacrylide polymers. Examples of gels based on colloidal silica are described, for example, in US 4,732,213, US 7,458,424, US 7,954,549, US 9,045,965 and WO 2009/034287. Other chemical systems, based, for example, on polyacrylide polymers, include those described in US 5,125,456 and US 5,957,203. Other applications for colloidal silica-based gel systems include consolidation/bonding of particulates, for example, prior to hydraulic fracturing, as described in US 7,013,973.

[006] In gel-type systems, such as colloidal silica-based gel systems, it is important to ensure that the gel time is controlled in order to allow sufficient time for the colloidal silica to penetrate sufficiently deeply into the formation rock in order to provide sufficient barrier, while not allowing penetration too deep so that dilution renders the gel barrier ineffective. It is also necessary for these gel-forming systems to function effectively under the high pressure and temperature conditions associated with underground hydrocarbon extraction wells. Although colloidal silica systems have been described for other applications, such as for forming subsurface soil barriers to contain contaminants (US 5,836,390) or for sealing cracks or fissures in rocks, soil, highways, tunnels, bridges or buildings (WO 2004/018381), therefore, the conditions experienced in these systems, such as temperatures that are particularly lower, are very different from those experienced in oil or gas extraction wells.

[007] There is, therefore, a need for a composition for use in the underground zone, such as a composition that can form gel, and methods of using this composition that have controllable gel formation time, are stable over a wide range of temperatures and can be removed if necessary, for example by increasing the pH. Furthermore, there is a need for a composition for use in the underground zone, such as a composition that can form a gel, which is less harmful to the environment than the gels based on organic polymers that are frequently used.

BRIEF DESCRIPTION OF THE INVENTION

[008] The present invention provides a composition comprising modified colloidal silica and an accelerator. At least a portion of the silanol groups on the surface of an unmodified colloidal silica is replaced by an organosilane moiety. The accelerator is an organic or inorganic salt that includes one or more cations. The molar ratio between silica and cation (X) of the composition is defined by the equation:

[009] In this equation, Nsilica is the total number of moles of silica in the composition, Ncations is the total number of moles of cations in the composition and Z is the charge on the cation. X is in the range of 8 to 50.

[0010] The composition and other aspects may include one or more of the following characteristics.

[0011] The organosilane portion may include a silicon atom linked to one, two or three R1 groups by a direct Si-C bond. Each R1 can be independently selected from alkyl, epoxy alkyl, alkenyl, aryl, heteroaryl, C1-6 alkylaryl and C1-6 alkylheteroaryl, optionally substituted by one or more groups selected from ER2, isocyanate and isocyanurate. And it can be absent or a linking group selected from the group consisting of -O-, -S-, -OC(O)-, -C(O)-, -C(O)O-, -C(O )OC(O)-, -N(R3)-, -N(R3)C(O)-, -N(R3)C(O)N(R3)- and -C(O)N(R3)- . R2 is selected from the group consisting of hydrogen, F, Cl, Br, alkyl, alkenyl, aryl, heteroaryl, C1-3 alkylaryl and C1-3 alkylheteroaryl and may be optionally substituted by one or more groups selected from from the group consisting of hydroxyl, F, Cl, Br, epoxy, -OR3, and -N(R3)2. R3 is H or C1-6 alkyl.

[0012] R1 may be a hydrophilic moiety or becomes hydrophilic after hydrolysis.

[0013] R1 can be selected from the group consisting of hydroxyl, thiol, carboxyl, ester, epoxy, acyloxy, ketone, aldehyde, (meth)acryloxy, amino, starch, ureido, isocyanate and isocyanurate.

[0014] R1 may include an epoxy group or one or more hydroxyl groups.

[0015] R1 may include an ER2 E substituent may be -O- and R2 may be selected from optionally substituted C1-8 epoxyalkyl and hydroxyl-substituted alkyl.

[0016] R1 may be a hydrophilic group that includes at least one heteroatom selected from O and N and R1 may include no more than three consecutive alkylene (CH2) groups.

[0017] R1 can be selected from 3-glycidoxypropyl, 2,3-dihydroxypropoxypropyl, 2,3-dihydroxypropyl and 2,3-dihydroxypropoxypropyl.

[0018] Modified colloidal silica can be prepared by contacting unmodified colloidal silica with an organosilane reagent. The organosilane reagent can be selected from a compound having the formula T4-ySi— [R1]y, siloxane having the formula [R1]bT3-bSi{-O-SiT2- c [R1]c}a-O-SiT3 -b [R1]b is a disilazane that has the formula { [R1]bT3-bSi}2-NH, where: y is from 1 to 3; each a is independently from 0 to 5; each b is independently from 1 to 3; c is 1 or 2; and each T is independently selected from the group consisting of halide, hydroxyl, C1-6 alkoxy and C1-6 haloalkoxy.

[0019] The degree of surface modification (DM) of colloidal silica modified by organosilane can be defined by the equation: and the MD is about 0.8 to about 4 molecules per nm2, where: A is Avogadro's constant; Norganosilane is the number of moles of organosilane reagent used; Silica is the extent of silica in colloidal silica, in m2g-1; and Msilica is the mass of silica in colloidal silica, in g.

[0020] The DM can be from about 1 to about 4.

[0021] The DM can be from about 1 to about 2.

[0022] The value of

[0023] The accelerator can be selected from halides, silicates, sulfates, nitrates, carbonates, carboxylates, oxalates, sulfides, hydroxides and mixtures of any two or more of these.

[0024] The accelerator can be selected from hydroxides and silicates.

[0025] The accelerator cation can be selected from alkali metal ions, alkaline earth metal ions, hydrogen ions, ammonium ions and organoammonium ions selected from primary, secondary, tertiary and quaternary ammonium ions .

[0026] The accelerator cation can be monovalent.

[0027] The cation can be an alkali metal.

[0028] The cation can be sodium.

[0029] The cation can be potassium.

[0030] The accelerator can be selected from sodium silicate, potassium silicate, sodium chloride and sodium hydroxide.

[0031] The pH of the composition can be from about 6 to about 11.

[0032] The pH of the composition can be from about 9 to about 11.

[0033] The accelerator may be present in an amount of from about 1 to about 30% by weight of the composition.

[0034] The silica content of the composition can be from about 3 to about 55% by weight, expressed as % by weight of non-functionalized silica.

[0035] The accelerator can be present in an amount of about 1 to about 30% by weight of the composition and the silica content of the composition can be from about 3 to about 55% by weight, expressed as % by weight. weight of unfunctionalized silica.

[0036] The accelerator can cause or facilitate the reaction between the organosilane-modified colloidal silica particles in the composition, which results in gel formation in a wellbore.

[0037] The composition can form an impermeable well gel.

[0038] The present invention also relates to a first method, which can be combined with any of the previous aspects, to reduce or eliminate the permeation of water or gas in an underground zone using the composition.

[0039] The first method and other aspects may include one or more of the following features.

[0040] The underground zone can be an underground oil well or underground gas well.

[0041] The present invention also relates to a second method, which can be combined with any of the above aspects, of obstructing formations in underground areas. The second method comprises mixing modified colloidal silica with an accelerator which is an organic or inorganic salt that includes one or more cations to form a composition. The second method comprises flowing the composition up a wellbore to a location down the well and to the formation in the underground zone. The second method comprises closing the wellbore for a period of time sufficient for the composition to form a gel that is impervious to fluid flow.

[0042] The second method and other aspects may include one or more of the following features.

[0043] The gelation speed of the composition can be controlled by the amount of silica and the amount of accelerator in the composition.

[0044] In some embodiments, the composition does not form the gel until the composition reaches the location below in the well.

[0045] The composition can form the gel under desired temperature at the location below in the well.

[0046] The present invention further relates to a third method, which may be combined with any of the above aspects, of shutting off the flow of water to a location down the well in a wellbore, which comprises conducting the second method, in which the gel that is formed substantially occupies the entire internal volume of the formation.

[0047] The third method and other aspects may include one or more of the following features.

[0048] Parts of the underground zone surrounding the formation into which the composition is to flow can be sealed.

[0049] Parts of the underground zone can be sealed using at least one packer per extension.

[0050] The present invention also relates to a fourth method of closing the fluid flow of a formation in an underground zone, which comprises conducting the first method, in which the modified colloidal silica, the accelerator, the amount of modified colloidal silica and the amount of accelerator are selected so that the composition forms a gel when the composition is exposed to at least a certain temperature for at least a certain period, wherein the formation in the underground zone is at least at a certain temperature and the composition is retained in the formation at least for a certain period, which results in the formation of gel in the formation, so as to close the flow of formation fluid.

[0051] The fourth method and other aspects may include one or more of the following features.

[0052] The molar ratio between silica and cation (X) of the composition can be defined by the equation: and the value of X is from about 8 to about 50; where Nsilica is the total number of moles of silica in the composition, Ncations is the total number of moles of cations in the composition and Z is the charge on the cation.

[0053] The present invention further relates to a fifth method of reducing or eliminating gas or water permeation in an underground zone, which comprises flowing a composition including modified colloidal silica and an accelerator into a wellbore until a place down in the well and a formation in the underground zone. The fifth method involves closing the wellbore for a period of time sufficient for the composition to form a gel that is impermeable to fluid flow.

[0054] The fifth method and other aspects may include the following feature. The underground zone can be an underground oil or gas well.

[0055] The embodiments described in the present invention are conveniently used in closing water and/or gas in wells that have a high static temperature at the bottom of the well, particularly in conditions such that unmodified silica tends to form gel very quickly and modifiers Organic polymers tend to degrade.

BRIEF DESCRIPTION OF FIGURES

[0056] Figures 1A and 1B are schematic diagrams of well holes. Figure 1A shows a well that simultaneously produces water and hydrocarbons. Figure 1B is an illustration of the implementation of water control in a wellbore using a modified colloidal silica-based composition.

[0057] Figure 2 is a flowchart defining a method embodiment in accordance with the present invention.

[0058] Figure 3 is a plot that displays the change in viscosity over time for two gel formation systems using organosilane-modified colloidal silica and different amounts of a sodium silicate accelerator.

[0059] Figures 4A and 4B are plots showing results of core flooding tests performed using a modified colloidal silica composition.

DETAILED DESCRIPTION OF THE INVENTION

[0060] Compositions containing a colloidal silica and an accelerator are provided in the present invention. In some embodiments, the colloidal silica is modified. In some embodiments, the colloidal silica is modified by organosilane. In some embodiments, the composition containing colloidal silica and an accelerator forms a gel. In some embodiments, the gel is used for gas and/or water shutoff applications in underground areas. It has been discovered that compositions according to the present invention can improve performance in underground oil field and gas field applications to block the entry of unwanted fluid (typically water and/or gas) into an underground zone, such as an orifice. well or oil or gas well. In some embodiments, the compositions of the present invention form gels by allowing a colloidal silica to penetrate porous sediments or fissures, then gel and harden in the presence of an accelerator to create a barrier. Inorganic gels, such as the silica-based gels of the present invention, are generally more stable over a wider temperature range and can also be removed if necessary by increasing the pH, compared to polymers. organic compounds, such as polyacrylamides. In some embodiments, the compositions and methods according to the present invention have environmental benefits, as colloidal silica is generally less harmful to the environment than the organic polymers that are often used.

[0061] In the discussion below, “organosilane-modified colloidal silica” may be indicated as “organosilane-functionalized colloidal silica”. Furthermore, the term “accelerator” can be indicated as “activator”.

[0062] Without wishing to restrict any theory, it is believed that colloidal silica particles functionalized by organosilanes condense more slowly than non-functionalized colloidal silica, which allows better control of the speed of condensation/gel formation at higher temperatures, when faster gel formation occurs compared to milder conditions such as urban construction applications. Organosilane-functionalized colloidal silica particles are also less sensitive to the electrolyte content in surrounding rock formations, which reduces the chances of uncontrolled gel formation in unwanted parts of the well. By improving the control of gel formation, greater penetration capabilities can be achieved in permeable rock formations, whilst maintaining sufficient reactivity to ensure that the reaction is fast enough to ensure that it can still an effective barrier must be provided without penetrating too deeply, which causes too much dilution of the colloidal silica to reach the appropriate water block.

[0063] The compositions provided in the present invention contain colloidal silica. As used herein, the term “colloidal silica” indicates a dispersion of amorphous silica (SiO2) particles with diameters of about 1 nm to about 150 nm. Colloidal silica can be obtained as a dispersion in solvent. Solvents may include, but are not limited to, water, isopropyl alcohol (IPA), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC). In some embodiments, the dispersion is an aqueous dispersion. In solvents that can act as proton acceptors (i.e., Bronsted bases such as water, alcohols, DMF, and DMAC), the colloidal silica dispersion is charge stabilized. The colloidal silica surface is enclosed by silanol groups (i.e., Si-O-H groups). Due to the acidic nature of the proton at the end of the silanol group, a small fraction of the silanol groups ionize in a Bronsted-based solvent. Consequently, colloidal silica develops negative surface charge. This charge guarantees that, when two colloidal silica particles come close to each other, they will experience a repulsive force and, if this repulsive force is large enough, the particles will not agglomerate. Colloidal silica in Bronsted base solvent therefore produces a dispersion that is stable to agglomeration.

[0064] In some embodiments, the colloidal silica is modified on the surface. In some embodiments, the colloidal silica includes colloidal silica particles in which at least a portion of the surface silanol groups is replaced by one or more chemically bonded organosilane groups. In some embodiments, the chemically bonded organosilane groups include a silicon atom bonded to an —R1 group. In some embodiments, one to three —R1 groups are present on the silicon atom of the organosilane moiety. In some embodiments, there are three groups —R1. In some embodiments, there are two groups —R1. In some embodiments, there is a group —R1. When there is more than one group —R1, they can be identical or different from each other.

[0065] Colloidal silica functionalized by organosilane can be prepared using conventional processes, such as those described in WO 2004/035473 and WO 2004/035474. In some embodiments, the organosilane-functionalized colloidal silica is formed from a reaction between an organosilane reagent and one or more silanol groups on the silica surface of the colloidal silica, that is, [SiO2]—OH groups. In some embodiments, the organosilane reagent has the formula T4-ySi- [R1]y. In some embodiments, each T of the organosilane reagent is independently selected from C1-6 alkoxy, C1-6 haloalkoxy, hydroxy and halide. In some embodiments, each T is C1-6 alkoxy. In some embodiments, each T is methoxy. In some embodiments, each T is ethoxy. In some embodiments, there are 3 T groups and each group is ethoxy. In some embodiments, the organosilane reagent is a siloxane. In some embodiments, the siloxane is a compound of the formula [R1]bT3-bSi{-O-SiT2-c [R1]c}a-O- SiT3-b [R1]b, where a is 0 or an integer of 1 or more, such as 0 to 5, b is 1 to 3, and c is 1 to 2. In some embodiments, the organosilane reagent is disilazane. In some embodiments, disilazane is a compound of the formula { [R1]bT3-bSi}2-NH, where b is 1 to 3. In some embodiments, T is an alkoxy or halide group. In some embodiments, the halide is chloride. In some embodiments, T is a haloalkoxy group, wherein the halo group is fluoro or chloro. In some embodiments, T is an alkoxy group. In some embodiments, the alkoxy group is a C1-4 alkoxy group, such as methoxy, ethoxy, propoxy or isopropoxy.

[0066] In some embodiments of the organosilane reagent, R1 is an organic portion. In some embodiments, R1 is selected from alkyl, alkenyl, amino, ureido, epoxy alkyl, aryl, heteroaryl, C1-6 alkylaryl and C1-6 alkylheteroaryl groups, any of which is optionally substituted by one or more selected groups from ER2, isocyanate and isocyanurate. In some embodiments, R1 includes from 1 to about 16 carbon atoms, such as from 1 to about 12 carbon atoms or from 1 to about 8 carbon atoms. In some embodiments, R1 is linked to the silicon organosilane by a direct C-Si bond. When there is more than one R1 group (i.e., y is greater than 1), each R1 can be identical or different.

[0067] In some embodiments of ER2, E is not present and R2 is linked directly to R1. In some embodiments of ER2 in which E is present, E is a linking group selected from -O-, -S-, -OC(O)-, -C(O)-, -C(O)O-, - C(O)OC(O)-, -N(R3)-, -N(R3)C(O)-, -N(R3)C(O)N(R3)- and - C(O)N( R3)-, where R3 is H or C1-6 alkyl. In some embodiments, R2 is selected from halogen (e.g., F, Cl or Br), alkyl, alkenyl, aryl, heteroaryl, C1-3 alkylaryl and C1-3 alkylheteroaryl. In some embodiments, R2 is replaced by one or more groups selected from hydroxyl, halogen (e.g., F, Cl or Br), epoxy, -OR3 or -N(R3)2 wherein each R3 is as defined above. In some embodiments, E is present and R2 is hydrogen.

[0068] In some embodiments, R1 is selected from C1-8 alkyl, C1-8 haloalkyl, C1-8 alkenyl and C1-8 haloalkenyl. In some embodiments, R1 is C1-8 alkyl or C1-8 alkenyl, with an optional halide substituent. In some embodiments, the halide substituent is chloride. In some embodiments, R1 is selected from methyl, ethyl, chloropropyl, isobutyl, cyclohexyl, octyl and phenyl. In some embodiments, R1 is a C1-8 group, C1-6 group or C1-4 group.

[0069] In some embodiments, R1 is alkyl isocyanate, such as propyl isocyanate. In some embodiments, R1 is an isocyanurate moiety. In some embodiments, R1 is a propyl isocyanurate moiety.

[0070] In some embodiments, R1 is a hydrophilic moiety. In some embodiments, R1 is a hydrophilic moiety that contains at least one group selected from hydroxyl, thiol, carboxyl, ester, epoxy, acyloxy, ketone, aldehyde, (meth)acryloxy, amino, starch, ureido, isocyanate and isocyanurate. In some embodiments, the hydrophilic portion includes at least one heteroatom selected from O and N and includes no more than three consecutive alkylene groups (-CH2-) linked together.

[0071] In some embodiments, R1 is a group comprising 1 to 8 carbon atoms (C1-8 alkyl group) and additionally includes a substituent ER2 in which E is oxygen and R2 is selected from C1-8 epoxyalkyl and C1-hydroxyalkyl 8 replaced. In some embodiments, R2 is optionally substituted alkyl isocyanurate. Examples of such ER2 substituents include 3-glycidyloxypropyl and 2,3-dihydroxypropoxypropyl.

[0072] In some embodiments, R1 is a group comprising 1 to 8 carbon atoms (C1-8 alkyl group) and additionally includes a substituent ER2 in which E is not present and R2 is epoxyalkyl. In some embodiments, R2 is epoxycycloalkyl. An example of this R1 group is beta-(3,4-epoxycyclohexyl)ethyl. In some embodiments, the epoxy group contains two neighboring hydroxyl groups. In some embodiments, R2 is dihydroxyalkyl such as dihydroxycycloalkyl and R1 is (3,4-dihydroxycyclohexyl)ethyl.

[0073] In some embodiments, when there is more than one R1 group on the Si atom of the organosilane, at least one is a C1-8 alkyl or alkenyl group.

[0074] In some embodiments, R1 is a C1-C6 alkyl group. In some embodiments, R1 is methyl. In some embodiments, R1 is propyl. In some embodiments, R1 is a ureido group (-NH-C(O)-NH2). In some embodiments, R1 is glycidyloxypropyl.

[0075] In the above definitions, alkyl and alkenyl groups can be aliphatic, cyclic or can include aliphatic and cyclic moieties. Aliphatic groups or portions can be linear or branched. In some embodiments, when any group or substituent includes halogen, the halogen is selected from F, Cl and Br.

[0076] In some embodiments, some groups undergo hydrolysis reactions under conditions found in the colloidal silica medium. In some embodiments, therefore, groups containing moieties such as halide, acyloxy, (meth)acryloxy and epoxy groups hydrolyze to form the corresponding carboxyl, hydroxyl or glycol moieties.

[0077] Examples of organosilane reagents that can be used to prepare the functionalized colloidal silicas according to the present invention include, but are not limited to, octyl triethoxysilane, methyl triethoxysilane, methyl trimethoxysilane, tris-[3-(trimethoxysilyl)propyl]isocyanurate, 3-mercaptopropyl trimethoxysilane, beta-(3,4-epoxycyclohexyl)-ethyl trimethoxysilane, silanes containing an epoxy group (epoxy silane), glycidoxy and/or glycidoxypropyl, such as 3-(glycidoxypropyl)trimethoxy silane (which may be also known as trimethoxy [3-(oxyranylmethoxy)propyl]silane), 3-glycidoxypropyl methyldiethoxysilane, (3-glycidoxypropyl)triethoxy silane, (3-glycidoxypropyl)hexyltrimethoxy silane, beta-(3,4-epoxycyclohexyl)-ethyltriethoxysilane; 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl triisopropoxysilane, 3-methacryloxypropyl triethoxysilane, octyltrimethoxy silane, ethyltrimethoxy silane, propyltriethoxy silane, phenyltrimethoxy silane, 3-mercaptopropyltriethoxy silane, cyclohexyltrimethoxy silane, cyclohexyltriethoxy silane, dimethyldimethoxy silane, 3-chloropropyltriethoxy silane, 3-methacryloxypropyltrimethoxy silane, i-butyltriethoxy silane, trimethylethoxy silane, phenyldimethylethoxy silane, hexamethyldisiloxane, trimethylsilyl chloride, ureidomethyltriethoxy silane, ureidoethyltriethoxy silane, ureidopropyltriethoxy silane, hexamethyldisilizane and mixtures thereof. US 4,927,749 describes additional suitable silanes that can be used in the present invention.

[0078] In some embodiments, the organosilane includes one or more epoxy groups. In some embodiments, the organosilane is epoxyalkyl silane or epoxyalkyloxyalkyl silane. In some embodiments, the organosilane includes one or more hydroxyl-substituted groups. In some embodiments, the hydroxyl-substituted groups are hydroxyalkyl or hydroxyalkoxyalkyl groups that comprise one or more hydroxyl groups, such as 1 or 2 hydroxyl groups. Examples include, but are not limited to, organosilanes that contain a glycidoxy, glycidoxypropyl, dihydropropoxy or dihydropropoxypropyl group. In some embodiments, the organosilane is derived from organosilane reagents, such as (3-glycidoxypropyl)trimethoxysilane, (3-glycidoxypropyl)triethoxysilane and (3-glycidoxypropyl)methyldiethoxysilane. In some embodiments, the epoxy groups hydrolyze to form corresponding neighboring diol groups. In some embodiments, therefore, the compositions according to the present invention also encompass the diol equivalents of the above epoxy group-containing compounds.

[0079] In some embodiments, organosilane-functionalized colloidal silica is formed from a reaction between one or more organosilane reagents and one or more silanol groups on the silica surface of the colloidal silica. In some embodiments, the organosilane reagent is (3-glycidyloxypropyl)triethoxysilane. In some embodiments, the organosilane reagent is propyletriethoxysilane. In some embodiments, the organosilane reagent is methyltriethoxysilane. In some embodiments, the organosilane reagent is ureidopropyltriethoxysilane. In some embodiments, the organosilane reagent is a mixture of one or more organosilane reagents. In some embodiments, the organosilane reagent is a mixture of (3-glycidyloxypropyl)triethoxysilane and propyltriethoxysilane. In some embodiments, the organosilane reagent is a mixture of about 50 mole % to about 70 mole % (3-glycidyloxypropyl)triethoxysilane and about 30 mole % to about 50 mole % propyltriethoxysilane. In some embodiments, the organosilane reagent is a mixture of about 60 mole % (3-glycidyloxypropyl)triethoxysilane and about 40 mole % propyltriethoxysilane. In some embodiments, the organosilane reagent is a mixture of (3-glycidyloxypropyl)triethoxysilane and ureidopropyltriethoxysilane. In some embodiments, the organosilane reagent is a mixture of about 40 mole % to about 60 mole % (3-glycidyloxypropyl)triethoxysilane and about 40 mole % to about 60 mole % ureidopropyltriethoxysilane. In some embodiments, the organosilane reagent is a mixture of about 50 mol% (3-glycidyloxypropyl)triethoxysilane and about 50 mol% ureidopropyltriethoxysilane.

[0080] In some embodiments, the organosilane reagent undergoes a prior hydrolysis step, in which one or more T groups are converted to -OH, as described, for example, by Greenwood and Gevert, Pigment and Resin Technology, 2011, 40 ( 5), pp. 275-284.

[0081] In some embodiments, the reaction between an organosilane reagent and one or more silanol groups on the silica surface of the colloidal silica results in one or more organosilane groups chemically bonded to the surface of the colloidal silica. In some embodiments, all organosilane groups are identical. In some embodiments, the organosilane groups are different. In some embodiments, chemically bonded organosilane groups are represented by the formula [{SiO2}—O—]4-y-z [Z]z Si— [R1]y, where —O— of the {SiO2}—O— group represents a oxygen atom on the silica surface. In some embodiments, the organosilane silicon atom contains at least one and up to three such bonds to the silica surface, i.e., 4-y-z is at least 1 and not more than 3. In some embodiments, the Z group is present. In some embodiments, z is in the range 0 to 2. In some embodiments, the organosilane silicon atom contains 1 to 3 [R1] groups, that is, y is 1 to 3 or 1 to 2. When there are more of an R1 group, they can be identical or different.

[0082] In some embodiments, when z is not zero, the organosilane silicon contains unreacted T groups and/or contains hydroxyl groups in which the T group has been removed. In some embodiments, the T group is removed through a hydrolysis reaction. In some embodiments, a Si-O-Si link can be formed with the silicon atom of a neighboring organosilane group. In some embodiments, therefore, in the formula { [SiO2]—O—}4-y-z [Z]z Si— [R1]y, the group Z is, independently for each occurrence, selected from the groups defined for T above and also of hydroxy groups and —O— [SiR1]' groups in which the [SiR1]' group is a neighboring organosilane group.

[0083] In some embodiments, the organosilane reagent reacts with a surface silanol group to form one to three Si-O-Si bonds between the silica surface of the colloidal silica and a silicon atom of the organosilane reagent. In some embodiments, a compound is formed having the formula { [SiO2]—O—}4-y-z [T]z Si— [R1]y, where 4-y-z is from 1 to 3, such as 1 to 2 , and as a result, a corresponding number of T groups are removed from the organosilane. If T is an alkoxy unit, for example, an alcohol will be produced.

[0084] In some embodiments, at least part of the organosilane reagent is in dimeric or even oligomeric form before binding to the colloidal silica. In some embodiments, two or more organosilane reagent moieties are linked together via Si-O-Si bonds.

[0085] In some embodiments, the modified (or “functionalized”) colloidal silica contains more than one organosilane, which are different from each other; for example, wherein the organosilane-modified silica is produced by reacting a mixture of two or more organosilanes with colloidal silica or by mixing two or more separately prepared organosilane-modified colloidal silicas.

[0086] In some embodiments, organosilane compounds form stable covalent siloxane bonds (Si-O-Si) with the silanol groups of colloidal silica. In some embodiments, the organosilane compounds are linked to the silanol groups by hydrogen bonds on the surface of the colloidal silica particles. In some embodiments, not all silica particles of the colloidal silica are modified by the organosilane group. The proportion of colloidal silica particles that are functionalized with the organosilane group may depend on a number of factors, such as the silica particle size and extent available, the relative amounts of organosilane reagent to colloidal silica used to functionalize the colloidal silica , the type of organosilane reagents used and the reaction conditions.

[0087] In some embodiments, the degree of modification (MD) of the silica surface by the organosilane group is expressed according to the following calculation (Equation 2), in terms of the number of silane molecules per square nanometer of silica surface : where: - DM is the degree of surface modification in units per square nanometer (nm-2); - A is Avogadro's constant; - Norganosilane is the number of moles of organosilane reagent used; - Silica is the extent of silica in colloidal silica, in square meters per gram (m2g-1); e - Msilica is the mass of silica in colloidal silica, in grams (g).

[0088] In some embodiments, the extent of silica is conveniently measured by means of Sears titration.

[0089] In some embodiments, the MD may be at least 0.8 silane molecules per nm2, such as in the range of 0.8 to 4 molecules per nm2. In some embodiments, the DM is in the range of 1 to 3, such as 1 to 2 molecules per nm2.

[0090] The colloidal silica used in the composition of the present invention is a stable colloid. “Stable” indicates that the organosilane-functionalized colloidal silica particles dispersed in the medium substantially do not gel or precipitate within a period of at least two months, at least four months, or at least five months in normal storage at room temperature (20 °C).

[0091] In some embodiments, the relative increase in viscosity of the silane-functionalized colloidal silica dispersion between its preparation and up to two months after its preparation is less than 100%, such as less than 50 or less than 20%. In some embodiments, the relative increase in viscosity of the silane-functionalized colloidal silica between its preparation and up to four months after its preparation is less than 200%, such as less than 100% or less than 40%.

[0092] In some embodiments, silica particles within silica sols (colloidal silicas) are modified by one or more additional oxides in addition to the organosilane modification. In some embodiments, the additional oxide is an aluminum oxide or boron oxide. Boron-modified silica sols are described, for example, in US 2,630,410. In some embodiments, alumina-modified silica particles contain Al2O3 content of about 0.05 to about 3% by weight, such as about 0.1 to about 2% by weight. The procedure for preparing alumina-modified silica sol is described, for example, in The Chemistry of Silica, by Iler, K. Ralph, pp. 407-409, John Wiley & Sons (1979) and in US 5,368,833.

[0093] In some embodiments, the silica in colloidal silica does not contain additional added oxide. In some embodiments, the colloidal silica contains no more than trace amounts or impurities in each case, such as less than 1000 parts per million (ppm) by weight of additional oxides each. In some embodiments, the total amount of non-silica oxides present in sol is less than about 5000 ppm by weight, such as less than about 1000 ppm.

[0094] In some embodiments, the colloidal silica particles have an average particle diameter ranging from about 2 to about 150 nm, such as about 3 to about 50 nm or about 5 to about 25 nm. In some embodiments, the average particle diameter is in the range of about 6 to about 20 nm. In some embodiments, the colloidal silica particles have a specific extent of from about 20 to about 1500 m2g-1, such as about 50 to about 900 m2g-1, about 70 to about 600 m2g-1, or about 70 at around 400 m2g-1. Extensions according to the present invention are based on Sears titration measurements (GW Sears, Anal. Chem., 1956, 28 (12), pp. 1981-1983) of "basic" or "non-functionalized" colloidal silicas which are used for synthesis. This is because functionalization of silica surfaces can make Sears titration measurements difficult. In some embodiments, the particle diameter is calculated from the titrated length, using, for example, a method described in The Chemistry of Silica, by Iler, K. Ralph, p. 465, John Wiley & Sons (1979). In some embodiments, it is considered that the silica particles have a density of 2.2 grams per cubic centimeter (g/cm-3) and that all particles are the same size, have a smooth extension and are spherical, so that the particle diameter can be calculated using Equation 3:

[0095] In some embodiments, colloidal silica particles are dispersed in water in the presence of stabilizing cations. In some embodiments, the stabilizing cations are selected from K+, Na+, Li+, NH4+, organic cations, quaternary amines, tertiary amines, secondary amines and primary amines or mixtures thereof, so as to form aqueous silica sol. In some embodiments, the dispersions include organic solvents. In some embodiments, organic solvents are those that are miscible with water, such as lower alcohols, acetone or mixtures thereof. In some embodiments, the organic solvent is present at a volume to water ratio of 20% or less. In some embodiments, no solvent is added to the colloidal silica or functionalized colloidal silica. In some embodiments, organic solvents in the composition may arise during the synthesis of organosilane-functionalized colloidal silica due to the reaction of an organosilane reagent with the silica. If the organosilane reagent is alkoxide, for example, the corresponding alcohol will be produced. In some embodiments, the amount of any organic solvent is kept below about 20% by weight, such as less than about 10% by weight.

[0096] In some embodiments, the silica content of functionalized silica sol, prior to mixing with the accelerator, is in the range of about 5 to about 60% by weight, such as about 10 to about 50% by weight. % or about 15 to about 45%. It is expressed as % by weight of unfunctionalized silica and calculated from the % by weight of silica in the colloidal silica source before modification with organosilane. In some embodiments, in the presence of accelerator, the silica content in the final composition is in the range of about 3 to about 58% by weight, such as about 10 to about 55% by weight, for example about 15 to about 50% by weight, expressed as % by weight of non-functionalized silica (i.e. SiO2).

[0097] In some embodiments, the pH of functionalized silica sol is in the range of about 1 to about 13, such as about 2 to about 12, about 4 to about 12, about 6 to about about 12 or about 7.5 to about 11. In some embodiments, in which the silica is modified by aluminum, the pH is in the range of about 3.5 to about 11.

[0098] In some embodiments, the functionalized colloidal silica, prior to mixing with the accelerator, has an S value of about 20 to about 100, such as about 30 to about 90 or about 60 to about 90. S value characterizes the extent of aggregation of colloidal silica particles, such as the degree of aggregate or microgel formation. In some embodiments, the S value is measured and calculated in accordance with formulas given in Iler, R. K. and Dalton, R. L. in J. Phys. Chem., 60 (1956), 955-957. The S value depends on the silica content, viscosity and density of the colloidal silica. High S value indicates low microgel content. The S value indicates the amount of SiO2 in weight percentage present in the dispersed phase of silica sol. In some embodiments, the degree of microgel formation can be controlled during the production process, as described, for example, in US 5,368,833. The S value for colloidal silica with organosilane functionality is typically indicated as the S value of the “raw” or “unfunctionalized” colloidal silicas that are used for synthesis (similar to the extensions expressed herein).

[0099] In some embodiments, the weight ratio of organosilane to silica in functionalized silica sol is from about 0.003 to about 1.5, such as about 0.006 to about 0.5 or about 0.015 to about 0.25. In some embodiments, the weight of organosilane in the dispersion is calculated as the total amount of possible organosilane derivatives or free organosilane compounds or groups bound or attached to the silica particles, e.g., based on the total amount of organosilane reactant(s). initially added to colloidal silica to produce organosilane-modified silica, not necessarily based on a direct measurement of the amount of organosilane actually chemically bound to the silica.

[00100] The compositions according to the present invention contain an accelerator. In some embodiments, the accelerator is capable of causing or facilitating reactions that cause colloidal silica particles to react with each other, which results in gel formation. In some embodiments, the accelerator is capable of accelerating the gel formation of colloidal silica (modified by organosilanes). In some embodiments, the accelerator causes the colloidal silica particles to react with each other, which results in an increase in the viscosity of the composition. In some embodiments, more than one accelerator is used.

[00101] In some embodiments, the accelerator is a salt. In some embodiments, the accelerator is an organic salt. In some embodiments, the accelerator is an inorganic salt. In some embodiments, the salt is selected from halides, silicates, sulfates, nitrates, carbonates, carboxylates, oxalates, sulfides and hydroxides. In some embodiments, the salt is halide, hydroxide or silicate. In some embodiments, the halide is chloride.

[00102] In some embodiments, the accelerator includes an anion. In some embodiments, the anion is selected from halide (such as chloride, bromide or iodide), carbonate, hydroxide, sulfate, nitrate, silicate, aluminate, phosphate, hydrogen phosphate, carboxylate or oxalate. In some embodiments, the accelerator includes a cation. In some embodiments, the cation is selected from alkali metals, alkaline earth metals, hydrogen, main group metals (e.g., aluminum, gallium, indium, or tin), ammonium ions, including primary ammonium ions, secondary ammonium , tertiary ammonium and quaternary ammonium, and organic cations such as amino and organoamino ions. In some embodiments, the cation is a proton and, for example, an acid is used as the accelerator. In some embodiments, the cation is monovalent. In some embodiments, the alkali metal is selected from sodium or potassium.

[00103] In some embodiments, the accelerator is an inorganic salt. Examples of inorganic salts include, but are not limited to, aluminum chloride, aluminum nitrate, aluminum sulfate, potassium chloride, calcium chloride and other calcium donors such as cement, sodium chloride, magnesium chloride, magnesium sulfate , potassium iodide, sodium hydrogen phosphate, magnesium nitrate, sodium nitrate, potassium nitrate, calcium nitrate, potassium silicate, sodium silicate and mixtures thereof.

[00104] In some embodiments, the accelerator is a silicate. In some embodiments, the accelerator is sodium silicate or potassium silicate. In some embodiments, the accelerator is sodium chloride. In some embodiments, the accelerator is a hydroxide. In some embodiments, the accelerator is an alkali metal hydroxide, ammonium hydroxide, or organoammonium hydroxide.

[00105] In some embodiments, the accelerator cation is a monovalent cation. In some embodiments, the monovalent cation is an alkali metal cation, ammonium ion, or organoammonium ion. In some embodiments, the monovalent cation is an alkali metal cation. In some embodiments, the alkali metal cation is lithium, sodium or potassium.

[00106] In some embodiments, the accelerator includes an alkali metal silicate. In some embodiments, the alkali metal silicate contains one or more of potassium, sodium and lithium. In other embodiments, an organic silicate is used. In some embodiments, the organic silicate contains an amino or ammonium cation. In some embodiments, the molar ratio of SiO2/M2O, where M is sodium or potassium, is from about 1 to about 4. In some embodiments, the molar ratio of SiO2/M2O, where M is lithium or a component organic, is from about 1 to about 20.

[00107] In some embodiments, the accelerator is sodium silicate. In some embodiments, the sodium silicate accelerator is in an aqueous form having a SiO2 concentration of about 20% by weight to about 30% by weight and a sodium content (expressed as Na2O) of about 5% by weight. to about 10% by weight. In some embodiments, the sodium silicate accelerator is in an aqueous form that has a SiO2 concentration of about 24.2% by weight and a sodium content (expressed as Na2O) of about 7.3% by weight.

[00108] In some embodiments, the accelerator is potassium silicate. In some embodiments, the potassium silicate accelerator is in an aqueous form having a SiO2 concentration of about 20% by weight to about 30% by weight and a potassium content (expressed as K2O) of about 10% by weight. to about 15% by weight. In some embodiments, the potassium silicate accelerator is in an aqueous form that has a SiO2 concentration of about 23.8% by weight and a potassium content (expressed as K2O) of about 11% by weight.

[00109] In some embodiments, the accelerator is sodium chloride. In some embodiments, the sodium chloride accelerator is in aqueous form. In some embodiments, the sodium chloride accelerator is an aqueous solution of about 5% by weight to about 30% by weight sodium chloride. In some embodiments, the sodium chloride accelerator is a 10% by weight aqueous solution. In some embodiments, the sodium chloride accelerator is a 25% by weight aqueous solution.

[00110] In some embodiments, the accelerator is sodium hydroxide. In some embodiments, the sodium hydroxide accelerator is in aqueous form. In some embodiments, the sodium chloride accelerator is an aqueous solution of about 5% by weight to about 15% by weight sodium hydroxide. In some embodiments, the sodium hydroxide accelerator is a 10.3% by weight aqueous solution.

[00111] In some embodiments, the accelerator is soluble, or at least partially soluble, in the composition at room temperature (e.g., 15-25°C) and/or under underground well temperatures, e.g., in the range of about 90 to about 200 °C.

[00112] In some embodiments, the accelerator content in the composition is in an amount of about 1 to about 30% by weight, such as about 2 to about 15% by weight of the total dry weight of silicate and particles of silica.

[00113] In some embodiments, the molar ratio between silica and cation (X) of the composition according to the present invention is represented by Equation 1.

[00114] In this equation, Nsilica is the total number of moles of silica, Ncations is the total number of moles of cation and Z is the charge on the cation.

[00115] In some embodiments, X is in the range of about 8 to about 50. In some embodiments, the amount of accelerator in the composition is selected to achieve ratio In some embodiments, X is in the range of about 8 to about 25, such as about 8 to about 20. In other embodiments, X is about 10 to about 50, such as about 10 to about from 25 or about 10 to about 20. The number of moles of silica in this calculation includes not only silica from the colloidal silica source, but also any silica present in the accelerator. If the accelerator is silicate, such as sodium or potassium silicate, for example, the silica content includes the silicate of the accelerator. Therefore, the number of moles of silica is based on the silica or silicate present in the colloidal silica source and any silica or silicate present in the accelerator. In some embodiments, this ensures that the gel formed is not too thick for groundwater closure requirements, also ensuring that gel formation takes place in sufficient quantity to ensure sufficiently rapid gel formation characteristics and good gel strength. in order to maintain an efficient barrier.

[00116] In some embodiments, aqueous colloidal silica is made with salts present in the aqueous medium, such as sodium or potassium silicate. These cations are also included in the number of moles of cations in the above equation. Thus, in some embodiments, the number of moles of cations includes any cations present in the accelerator and also any cations present in the colloidal silica source. In some embodiments, the cations in the silica source are determined using methods such as X-ray fluorescence.

[00117] When there is more than one type of different cation in the composition, the above can be expressed as the sum of all types of different cations, as follows: where each “i” indicates a different cation and n is the total number of different cations.

[00118] In some embodiments, Z is 1 in all cases, that is, all cations are monovalent.

[00119] In some embodiments, the compositions according to the present invention are aqueous and liquid under standard pressure and temperature. In some embodiments, organic solvents such as lower alcohols, acetone or mixtures thereof are present, although in smaller amounts compared to water.

[00120] The compositions according to the present invention contain colloidal silica, such as modified colloidal silica according to the present invention, and an accelerator. The compositions are fluid compositions that can form gel. In some embodiments, the compositions form gels in underground oil or gas wells. In some embodiments, compositions according to the present invention have gel formation times that are suitable for use in underground oil or gas wells where temperatures are 90°C or more, often more than 100°C, such such as 110°C or more. Examples of temperature ranges in which the compositions are suitable for use include about 90 to about 200 °C, more than about 100 °C to about 200 °C and about 110 °C to about 180 °C. In some embodiments, gel formation times are greater than would otherwise be achieved using non-functionalized colloidal silica, but are still effective for use in gas and water shutoff applications in underground geological formations, such as wells. of crude oil and natural gas.

[00121] In some embodiments, the compositions have gel formation times of about one hour or more at a temperature of 120 °C. In some embodiments, the compositions have gel formation times of no more than 48 hours at a temperature of 120 ° C. In some embodiments, the compositions have gel formation times of about 1 hour to about 48 hours, about 1 hour to about 24 hours, such as about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 10 hours, about 12 hours, about 16 hours, about 20 hours, about 24 hours, about 30 hours, about 36 hours, about 42 hours or about 48 hours.

[00122] In some embodiments, the gel formation time of the composition can be controlled. In systems using non-functionalized colloidal silica, low amounts of accelerator are typically required and the gel formation time is very sensitive to changes in the amounts of accelerator salt, especially under high temperature conditions typically found in oil and gas wells. underground. If the quantities used are not precisely controlled, therefore, the gel formation time can easily find itself outside the desired time window. Furthermore, there is also the risk of premature or uncontrolled gel formation if contact is made with electrolytes in underground rock formations. On the other hand, in some embodiments, the compositions according to the present invention are less sensitive to variations in the amount of accelerator under these conditions. In some embodiments, there is greater tolerance for variations in the quantities used and there is the presence of electrolytes below the well.

[00123] In some embodiments, control of gel formation times can be achieved by customizing the ratio between colloidal silica and accelerator in the composition. In some embodiments, the ideal ratio depends on the nature of the organosilane group(s) and the conditions and nature of the porous rock formations involved.

[00124] In some embodiments, the composition includes colloidal silica modified by organosilanes and a salt accelerator. These compositions represent an environmentally friendly and non-toxic approach to achieving water and/or gas closure compared to certain known chemical systems.

[00125] Also provided in the present invention are methods of reducing or eliminating permeation of water or gas in underground areas, for example, in underground oil or gas wells. Methods according to the present invention include using the compositions according to the present invention to form gel in underground zones. In some embodiments, the gel is impervious to fluid flow. Because it can be challenging to obtain a perfectly impermeable barrier, the term “impermeable” according to the present invention includes systems in which small and insignificant levels of fluid permeation may occur.

[00126] A method of closing the flow of formations in underground zones is provided in the present invention. In some embodiments, the method includes forming a composition comprising modified colloidal silica and accelerator; flow of the composition from a wellbore to a location below the wellbore and to the formation in the underground zone; and closing the wellbore for a period sufficient for the composition to form a gel impervious to fluid flow. In some embodiments, the rate of gel formation of the composition is controlled by the amount of modified colloidal silica and the amount of accelerator in the composition. In some embodiments, the composition does not form a gel until the composition reaches the location below in the well. In some embodiments, the composition does not form a gel until the composition reaches a location downstream that has a certain temperature.

[00127] Also provided in the present invention is a method of closing the flow of water to a location downstream in a wellbore. In some embodiments, the method includes forming a composition comprising modified colloidal silica and accelerator; flow of the composition from a wellbore to a location below the wellbore and to the formation in the underground zone; and closing the wellbore for a period sufficient for the composition to form a gel impervious to fluid flow. In some embodiments, the gel occupies substantially the entire internal volume of the formation. In some embodiments, the method includes sealing portions of the underground zone around the formation into which the composition is to flow. In some embodiments, portions of the underground zone are sealed using at least one packer per span.

[00128] Also provided in the present invention is a method of closing fluid flow from formations in underground zones. In some embodiments, the method includes forming a composition comprising modified colloidal silica and an accelerator; flow of the composition from a wellbore to a location below the wellbore and to the formation in the underground zone; and closing the wellbore for a period sufficient for the composition to form a gel impervious to fluid flow. In some embodiments, the composition forms a gel upon exposure of the composition to a certain temperature for a certain period of time. In some embodiments, the underground zone is at a temperature sufficient to allow the composition to form gel.

[00129] In some embodiments of the methods according to the present invention, the amount of modified colloidal silica and the amount of accelerator are selected so that the gel formation rate of compositions according to the present invention is controlled. In some embodiments, the modified colloidal silica and accelerator do not form gel until the composition reaches the location down the well. In some embodiments, quantities are selected based on Equations 1 and 4 above. In some embodiments, amounts are selected so that the composition forms the gel under the temperature of the location downstream.

[00130] In some embodiments, the method is implemented in the form of a method of closing the flow of water to a location down the well in a wellbore. In some embodiments, the composition according to the present invention flows up a wellbore to a location down the wellbore within a formation in an underground zone in which the wellbore is formed. In some embodiments, the wellbore is closed long enough for the modified colloidal silica and the accelerator (the composition) to form a gel that is impervious to water flow. In some embodiments, the gel occupies substantially the entire internal volume of the formation.

[00131] In some embodiments, parts of the underground zone surrounding the formation into which the composition is to flow are sealed. In some embodiments, the parts are sealed using at least one packer per extension.

[00132] In some embodiments, the method is implemented as a method of closing the flow of fluid from a formation in an underground zone. In this method, various aspects of the composition (e.g., the modified colloidal silica, the accelerator and amounts thereof) are selected for gel formation when the composition is exposed to at least a given temperature for at least a certain period. In some embodiments, the composition according to the present invention flows into an underground formation, wherein the formation is at least a certain temperature. In some embodiments, the composition is retained in the formation for at least a certain period, which results in gel formation in the formation. In some embodiments, the gel closes the flow of formation fluid.

[00133] In some embodiments of the present invention, a well hole is formed in the underground zone. In some embodiments, the wellbore extends at least into the formation. In some embodiments, the composition flows into the formation through the wellbore.

[00134] In some embodiments, the composition is an environmentally friendly, non-toxic formulation that includes organosilane-modified silica and an accelerator that causes gel formation, of which the composition according to the present invention is an example. In some embodiments, the composition is placed within the wellbore, for example in desired formation zones, in the form of a single phase low viscosity solution. At these depths, the wellbore temperature can be high. In some embodiments, the use of modified colloidal silica allows the composition to operate at these elevated temperatures (temperatures can reach, for example, up to 177 ° C), allowing better control of gel formation time.

[00135] In some embodiments, the gel formation process is activated by the formation temperature. In some embodiments, the formation temperature is the temperature within the desired location in the underground zone. In some embodiments, in situ gel formation occurs to close (totally or partially) pore spaces so as to limit the production of unwanted water. In some embodiments, the internal volume of the formation into which the composition flows is substantially closed by the gel formed within the formation. In some embodiments, as a result of substantial closure, formation fluid (such as water, gas or other fluid) is not able to escape into the wellbore. In some embodiments, the concentration of substances or the amount of accelerator (or both) can be used to control gel formation time to allow predictable and controllable pumping times ranging from a few minutes to several hours under temperature. defined.

[00136] The composition will now be described with reference to water closure, although the same principles apply to the closure of other fluids, such as gas closure.

[00137] Figure 1A is a schematic diagram of a wellbore (100) that simultaneously extracts water (104) and hydrocarbons, such as gas (102a), oil (102b) or both. In some embodiments, the wellbore (100) is formed by implementing wellbore drilling operations in underground zones (108) that contain hydrocarbons. In some embodiments, the underground zone (108) includes a formation, part of a formation or several formations. The underground zone (108) in which the wellbore (100) is formed includes, for example, a formation bearing hydrocarbons, such as gas (102a) and oil (102b), and a water-bearing formation (104).

[00138] The example wellbore (100) is displayed in the form of a vertical wellbore. The wellbore (100) may be or include horizontal, vertical, inclined, curved or other geometries and orientations. The wellbore (100) may include a casing that is cemented or otherwise secured to the wall of the wellbore. In some embodiments, the wellbore may be uncased or may include uncased sections. When casing, perforations may be formed in the casing to allow flow of fluids from the formations to the wellbore (100) and to the surface of the wellbore (100).

[00139] In some cases, fracture treatments may be used, for example, to form or propagate fractures in the underground zone (108), in order to create fluid flow paths in the zone through which fluid can flow to the orifice of well (100). In some cases, injection treatment may be used to inject water into injection well holes formed adjacent to the well hole (100). The injected water can force the hydrocarbons around the wellbore (100) to flow into the wellbore (100) when the pressure in the underground zone (108) is insufficient to do so.

[00140] Drilling through various formations in the underground zone, whether alone or in combination with fracture treatment or injection treatment, can result in the flow of hydrocarbons (102a, 102b) and water (104) into the wellbore (100) . The simultaneously extracted fluids can flow to the surface, where the water can be separated from the fluids and discarded or re-injected into the underground zone. Water shutoff is the process of reducing or eliminating the flow of water (104) into the wellbore (100).

[00141] Gel treatment is a method of implementing water and/or gas shutoff. For known compositions, gel formation may occur at temperatures lower than the temperature at which the closing operation must be implemented. Water shutoff may, for example, need to be implemented deep inside the wellbore, where the formation temperature is high. The composition may, on the other hand, trigger gel formation at temperatures below the formation temperature. In these cases, premature gel formation may result in clogging of the pipe through which the composition is pumped down the well. Premature gel formation can, in turn, result in pressure buildup during water pumping.

[00142] On the other hand, the compositions according to the present invention, which comprise colloidal silica modified by organosilane and a salt as an accelerator, allow delay in gel formation until higher temperatures are reached. Consequently, compositions according to the present invention can flow into forming areas with elevated temperatures before gel formation occurs. Similarly, in other high temperature applications, gel formation can be delayed until high temperatures are reached. By doing so, sufficient time can be provided for the composition to penetrate deeper into the formation where the gel needs to be disposed.

[00143] In some embodiments, a gel for high temperature gas and/or water closure or other high temperature application can be formed using a composition comprising colloidal silica modified by organosilane (e.g., as described above) and an accelerator, which is a salt (e.g. as described above). In one embodiment, the organosilane is trialkoxy [3-(oxiranylmethoxy)propyl]silane. In some embodiments, the trialkoxy [3-(oxiranylmethoxy)propyl]silane is trimethoxy [3-(oxiranylmethoxy)propyl]silane or triethoxy [3-(oxiranylmethoxy)propyl]silane. In another embodiment, the accelerator is sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium silicate, potassium silicate or other accelerator. Other chemical components may be added, based on the environment in which the composition is implemented. To expand the injection capacity of water closure treatment in water-sensitive limestone formations, for example, a clay control agent can be added to the composition.

[00144] Figure 1B is a schematic diagram of implementing water control in the wellbore (100). The composition according to the present invention can flow into the wellbore (100), for example, through a tubular frame or rod (152). The chemistry of the composition results in delay of gel formation until penetration of the composition deeper into the formation from which water (104) flows to the wellbore (100). As described previously, the composition may flow into the formation from which the gas (102a) flows into the wellbore (100) to close the gas flow. The gel produced by gelling of the composition (e.g., gel 154) can cover the invasive parts of the formation through which water (104) flows into the wellbore (100) so as to close water extraction. Generally, the gel (154) formed by the composition can be used to close pores in any part of the formation into which the composition is injected.

[00145] Figure 2 is a flowchart of an example of a process (200) for carrying out the water shutoff operation using the composition according to the present invention. In (202), modified colloidal silica is mixed with an accelerator to form a composition. In some embodiments, a carrier fluid, such as water or another carrier fluid, is used to flow the composition from the surface to the location below in the wellbore. In some embodiments, the amount of carrier fluid varies from about 1242 liters per meter (l/m) to about 12,420 l/m. In some embodiments, the ratio of the composition to the carrier fluid varies from about 0 to about 60% by weight. In some embodiments, the concentration of modified colloidal silica is about 40% in water. In some embodiments, the composition is prepared by mixing 85% colloidal silica (40%) and 15% accelerator (see, for example, the first sample shown in Table 9). The quantity can be scaled for larger compounding volumes.

[00146] At (204), the composition flows into a wellbore, such as wellbore (100). Before or at the time of flow of the composition into the wellbore (100), operations may be implemented to ensure that the composition flows into the formation that needs to be closed (e.g., the water-bearing or water-bearing formation). gas) and not for other formations (for example, the oil-bearing formation). Operations may include appropriate placement methods, such as a stretch wrapper operation that utilizes coiled tubing to force-pump chemicals without coiled tubing. After injecting the composition into the desired formation, the operations can be reversed and, for example, the extension packer can be removed.

[00147] In some embodiments, the speed at which the composition flows through the wellbore (100) depends on factors including, for example, the target depth at which water or gas flow occurs and the injection capacity into the formation . Deeper target area with lower injection capacity may, for example, have a lower flow velocity (e.g. from 0.5 barrels/minute to 6 barrels/minute, i.e. from 79.5 liters per minute (l/ min) at 954 l/min) compared to shallow target areas with superior injection capacity. In some embodiments, the components of the composition are mixed into the surface. In some embodiments, the components of the composition flow into the wellbore (100) and are mixed during flow to the target depth. In these embodiments, the flow rate can be modified to allow mixing of the components. As the formation temperature increases with depth, the composition may gel as it flows toward the target depth. In these cases, the flow velocity may increase periodically to overcome the pressure buildup associated with gel formation and increased viscosity.

[00148] In (206), the well hole is closed for a period sufficient for the composition to gel. In some embodiments, the wellbore is closed for a sufficient period of time necessary for the composition to form the gel that is impermeable to water at the location below in the wellbore.

[00149] In (208), the flow of water into the well hole is closed using the gel. Because the gel is impermeable to water, the flow of water into the wellbore at the location below in the well is closed. In some embodiments, as the gel closes the formation, flow through the formation where the gel is located is closed.

EXAMPLES

[00150] The following examples demonstrate the gel-forming properties of various compositions that contained sol (colloidal silica) and accelerator. The compositions were prepared by mixing colloidal silica or silanized colloidal silica and an accelerator at room temperature using a magnetic stirrer. Each composition was then transferred to a glass ampoule for testing at 90°C or to sealed tubes for testing at 120-150°C. The compositions were then placed in an oven at the desired temperature and checked regularly. Gel formation time was the time at which the composition could be turned upside down without evidence of flow.

[00151] Separate rheological measurements were carried out on samples at 150 °C using a Grace M5600 Rheometer. A constant cutting rate of 10 reciprocal seconds (s-1) was applied during the experiment.

[00152] Colloidal silicas 1-13 and accelerators 1-4 used in gel-forming compositions are described below.

[00153] Colloidal silicas: - Colloidal Silica 1: non-functionalized colloidal silica with an extension of 170 square meters per gram (m2g-1), particle diameter of 16 nm, containing 40% by weight of silica, which contains sodium content ( expressed as Na2O) of 0.25% by weight and had pH 9-10; - Colloidal Silica 2: non-functionalized colloidal silica with an extension of 130 m2g-1, particle diameter of 21 nm, which contains 40% by weight of silica and contains a sodium content (expressed as Na2O) of 0.2% by weight and had pH 9-10; - Colloidal Silica 3: colloidal silica modified by aluminate based on a colloidal silica sol that has (before modification) an extension of 250 m2g-1 and a particle diameter of 11 nm. Aluminate-modified silica sol contained 30 wt% silica and 0.3 wt% Al2O3, sodium content (expressed as Na2O) of less than 0.2 wt% and had pH 6-7; - Colloidal Silica 4: colloidal silica modified by aluminate, based on a colloidal silica sol that has (before modification) an extension of 80 m2g-1 and a particle diameter of 34 nm. Aluminate modified silica sol contained 41 wt% silica, 0.3 wt% Al2O3, sodium content (expressed as Na2O) of 0.34 wt% and had pH 9-10; - Colloidal Silica 5: organosilane modified grade of colloidal silica based on colloidal silica 10 (see below). Modified colloidal silica sol contained 28 wt% silica, sodium content (expressed as Na2O) of less than 0.2 wt% and had pH 8. The degree of modification (MD) was 1.4 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify the silica was (3-glycidyloxypropyl)triethoxysilane; - Colloidal Silica 6: colloidal silica modified by organosilane based on colloidal silica 10 (see below). The modified colloidal silica contained 28 wt% silica, a sodium content (expressed as Na2O) of 0.71 wt% and had a pH of 10-11. The degree of modification (MD) was 1.05 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify the silica was (3-glycidyloxypropyl)triethoxysilane; - Colloidal Silica 7: colloidal silica modified by organosilane based on colloidal silica 10 (see below). The modified colloidal silica contained 28 wt% silica, a sodium content (expressed as Na2O) of 0.5 wt% and had a pH of 10-11. The degree of modification was 0.7 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify the silica was (3-glycidyloxypropyl)triethoxysilane; - Colloidal Silica 8: colloidal silica modified by organosilane based on colloidal silica that has (before modification) an extension of 220 m2g-1 and a particle diameter of 12 nm. Modified silica sol contained 38 wt% silica, sodium content (expressed as Na2O) of less than 0.2 wt% and had pH 8. The degree of modification was 1.7 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify the silica was (3-glycidyloxypropyl)triethoxysilane; - Colloidal Silica 9: colloidal silica modified by organosilane based on colloidal silica that has (before modification) an extension of 220 m2g-1 and a particle diameter of 12 nm. The modified colloidal silica contained 38 wt% silica, a sodium content (expressed as Na2O) of 0.51 wt% and had a pH of 10-11. The degree of modification was 1.7 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify the silica was (3-glycidyloxypropyl)triethoxysilane; - Colloidal Silica 10: non-functionalized colloidal silica with an extension of 360 m2g-1, particle size of 7 nm, which contains 30% by weight of silica, sodium content (expressed as Na2O) of 0.6% by weight and had pH 10-11; - Colloidal Silica 11: colloidal silica modified by organosilane based on colloidal silica 10 (see above). The modified colloidal silica contained 30% by weight silica, sodium content (expressed as Na2O) of 0.7% by weight and had a pH of 10-11. The degree of modification (MD) was 1.4 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify silica was (3-glycidyloxypropyl)triethoxysilane (60% mole) and propyltriethoxysilane (40% mole); - Colloidal Silica 12: colloidal silica modified by organosilane based on colloidal silica 1 (see above). The modified colloidal silica contained 40% by weight silica, sodium content (expressed as Na2O) of 0.3% by weight and had a pH of 10-11. The degree of modification (MD) was 1.7 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify the silica was methyltriethoxysilane; - Colloidal Silica 13: colloidal silica modified by organosilane based on colloidal silica 10 (see above). The modified colloidal silica contained 30% by weight silica, sodium content (expressed as Na2O) of 0.7% by weight and had a pH of 10-11. The degree of modification (MD) was 1.4 molecules per nm2 of silica surface, measured using Sears titration. The organosilane compound used to modify silica was (3-glycidyloxypropyl)triethoxysilane (50% mole) and ureidopropyltriethoxysilane (50% mole).

[00154] Accelerators: - Accelerator 1: sodium silicate, supplied in aqueous form that has a SiO2 concentration of 24.2% by weight and a sodium content (expressed as Na2O) of 7.3% by weight; - Accelerator 2: potassium silicate, supplied in aqueous form with a SiO2 concentration of 23.8% by weight and a potassium content (expressed as K2O) of 11% by weight; - Accelerator 3: sodium chloride, supplied in the form of an aqueous solution at 10% by weight or 25% by weight; - Accelerator 4: sodium hydroxide, supplied as an aqueous solution at 10.3% by weight.

EXAMPLE 1

[00155] In the Examples below, X = Si/cation molar ratio. In the calculations of

[00156] Table 1 displays the results of experiments on the formation of Colloidal Silica gels 1 to 4 that used different amounts of potassium silicate accelerator (Accelerator 2) at 90 °C. The temperature was typically lower than that seen in underground oil or gas wells. TABLE 1

[00157] Non-organosilanized colloidal silica gel formation times at 90 °C: 1 Based on the weight of aqueous potassium silicate. 2 Total weight of colloidal silica and accelerator silica. 3 Potassium content of aqueous potassium silicate expressed as % by weight of K2O. 4 No gel after several days.

[00158] These experiments demonstrated that the amount of accelerator affected gel formation times, in the same way as the silica source. The colloidal silicas modified by alumina (Colloidal Silicas 3 and 4) exhibited the shortest gel formation times among those used.

EXAMPLE 2

[00159] Table 2 displays the gel formation times for two non-organosilanized colloidal silicas (Colloidal Silicas 1 and 4) under higher temperature conditions, at 120 ° C in the presence of Accelerator 2.

[00160] These results demonstrated high sensitivity to gel formation times with only small changes in the amounts of potassium silicate accelerator used.

TABLE 2

[00161] Non-organosilanized colloidal silica gel formation times at 120 °C: 1 Based on the weight of aqueous potassium silicate. 2 Total weight of colloidal silica and accelerator silica. 3 Potassium content of aqueous potassium silicate expressed as % by weight of K2O. 4 No gel after seven days. 5 No gel after 24 hours.

EXAMPLE 3

[00162] Example 2 was repeated, except for the use of colloidal silicas with different extents of organosilanization (Colloidal Silicas 57 and 10-13) and a different accelerator (Accelerator 3) that contained sodium chloride. The results are displayed in Table 3.

[00163] This experiment demonstrated that gel formation times were affected by the extent of organosilane modification of colloidal silica. Low organosilane coverage still caused rapid gel formation to occur. Increasing the extent of silanization allowed achieving longer gel formation times. The results also demonstrated that varying the amount of accelerator contributed to achieving control over gel formation times and was less sensitive than the use of unmodified colloidal silica.

[00164] These results also indicated that a halide salt, such as sodium chloride, could be used as an accelerator. Furthermore, the results demonstrated that greater control of gel formation rates can be obtained using silanized silica.

[00165] The experiments further indicated that modification with hydrophilic groups tended to provide lower gel formation rates than modification with hydrophobic groups.

TABLE 3

[00166] Gel formation times of organosilanized colloidal silicas at 120 °C: 1 Soft gel 2 10% by weight of NaCl solution used. 3 Formed gel at room temperature after just 20 minutes. 4 It formed gel quickly when heated. 5 Weight of silica or sodium chloride, not including water.

EXAMPLE 4

[00167] Table 4 displays gel formation results at 120 ° C for different organosilanized colloidal silica (colloidal silica 8) in the presence of sodium silicate (Accelerator 1).

[00168] These results demonstrated that gel formation times at 120 °C can be controlled over a wide range using relatively high concentrations of the sodium silicate accelerator.

TABLE 4

[00169] Organosilanized colloidal silica gel formation times at 120 °C: 1 Based on the weight of aqueous sodium silicate. 2 Total weight of colloidal silica and accelerator silica. 3 Sodium content of aqueous sodium silicate expressed as % by weight of Na2O.

EXAMPLE 5

[00170] The gel formation times of organosilanized colloidal silicas with different particle sizes were evaluated at 150 °C in the presence of two silicate accelerators, Accelerator 1 and Accelerator 2. The results are displayed in Table 5.

[00171] These results demonstrated that gel formation times can be controlled using different silicate accelerators and organosilanized colloidal silicas with different particle sizes. Colloidal silica functionalized by organosilane with larger particle size (Colloidal Silica 8) showed a higher degree of modification and tended to require more accelerator to achieve gel formation.

TABLE 5

[00172] Gel formation times of organosilanized colloidal silicas at 150 °C: 1 Based on the weight of aqueous sodium or potassium silicate. 2 Total weight of colloidal silica and accelerator silica. 3 M is Na (Accelerator 1) or K (Accelerator 2). 4 Alkali metal content of aqueous alkali metal silicate expressed as % by weight of M2O.

EXAMPLE 6

[00173] Rheological studies at 150 °C were conducted on two different compositions based on Colloidal Silica 8, with 15 or 17% by weight sodium silicate (Accelerator 1) as the accelerator. A constant cutting rate of 10 s-1 was applied during the experiment. Measurements were taken using a Grace M5600 Rheometer. Time-dependent viscosity measurements were taken during gel formation of the two compositions and the results are illustrated in Figure 3. In Figure 3, the reference numeral 1 indicates the results for the composition comprising 17% by weight Accelerator 1 (with data points marked as crosses), while the reference numeral 2 indicates the results for the composition comprising 15% by weight of Accelerator 1 (with data points marked as diamonds).

[00174] For each composition, there was a period of time between the beginning of gel formation and, at that moment, there was a rapid increase in viscosity. This is a desirable profile for downhole applications as the composition can be selected to gel at the correct time based on the depth of the porous underground formation. Due to the steep profile, the composition remains relatively mobile before this point, causing less possibility of premature gel formation and potential problems when pumping the composition down the well.

[00175] The results also demonstrated that, by varying the amount of accelerator, the onset of rapid gel formation can be controlled.

EXAMPLE 7

[00176] Table 6 displays the results of compositions that included Accelerator 1 and Colloidal Silica 9, which is similar to Colloidal Silica 8, but contained a higher level of alkali metal and higher pH. Gel formation was evaluated at 150 °C.

TABLE 6

[00177] Effects of cation content on organosilanized colloidal silica gel formation times at 150 °C: 1 Based on the weight of aqueous sodium or potassium silicate. 2 Total weight of colloidal silica and accelerator silica. 3 Sodium content of aqueous sodium silicate expressed as % by weight of Na2O.

[00178] The results demonstrated that the compositions worked effectively, even when the initial pH of the silica sol was different, as compared to the results shown in Tables 4 and 5.

EXAMPLE 8

[00179] These experiments were based on compositions containing Colloidal Silica 8 or 9 and sodium hydroxide as the accelerator (Accelerator 4) at 150 °C. The results are displayed in Table 7 below.

TABLE 7

[00180] Effects of hydroxide as an accelerator at 150 °C: 1 Based on the weight of aqueous sodium or potassium silicate. 2 Total weight of colloidal silica and accelerator silica. 3 Sodium content of aqueous sodium silicate expressed as % by weight of Na2O.

[00181] These results demonstrated that a hydroxide, such as sodium hydroxide, could also function as an efficient accelerator, even at the highest temperature of 150 °C.

EXAMPLE 9 STATIC GEL FORMATION TEST:

[00182] Static gel formation tests were performed in glass test tubes and gel formation was estimated through visual observation. In typical static gel formation tests, glass test tubes were filled with a mixture of modified colloidal silica and a sodium silicate solution to about half of the total volume available inside the glass test tube. The glass tube was kept at room temperature or placed in an oven previously heated to the test temperature (e.g., 93 °C or 149 °C). When placed in a previously heated oven, the tubes were periodically removed for observation. Gel formation time was estimated as the time elapsed for the mixture to reach a point at which the formed gel did not move when the glass tube was turned upside down (which could be interpreted as the gel losing its strength). flow capacity). Table 8 displays the observed gel formation times for organosilane-modified colloidal silica and standard (unmodified) colloidal silica. The modified colloidal silica was Colloidal Silica 8 described above. A sodium silicate solution was used as an accelerator in these systems. Typical sodium silicate solutions used in the static gel formation test showed the following characteristics: hydrogen potential (pH) of 11.27, specific gravity of 1.359, 26.1 wt% silicon dioxide (SiO2), 8.40% by weight of sodium oxide (Na2O), molar ratio between silicon dioxide and sodium oxide (SiO2/Na2O) of 3.21 and 36 ppm iron (Fe).

TABLE 8

[00183] Gel formation time under different temperatures: 1 Unmodified colloidal silica. 2 Colloidal silica modified by organosilane.

[00184] As shown in Table 8, the gel formation time at 148 ° C was about four hours for the organosilane-functionalized colloidal silica composition compared to the composition containing the non-functionalized colloidal silica, which formed gel almost immediately. The gel formation time at 93 °C for unmodified colloidal silica was about six hours.

EXAMPLE 10 VISCOSITY TEST:

[00185] Viscosity testing was another method used to obtain information about gel formation times and the gel formation behavior of colloidal silica-based fluids under high pressure and high temperature (HPHT) conditions. The compositions were prepared by mixing 85% by weight or 87% by weight of Colloidal Silica 8 described above with liquid sodium silicate by stirring. The typical sodium silicate solution used in the viscosity test was identical to the sodium silicate used in the static gel formation test. Mixing was carried out at room temperature and the composition was then heated in a pressurized rheometer sample cup to the defined temperature under a cutting rate of 10 s-1. Map rheometer tests were conducted with colloidal silica-based fluids under defined temperatures of 134 °C, 148 °C and 156 °C. Temperatures were similar to downhole temperatures in wellbores such as gas wells. Viscosity was measured during viscosity tests using a viscometer/rheometer and viscosity was monitored as a function of time. Gel formation time was estimated as the time elapsed for a significant increase in the viscosity of the mixture, such as an increase in viscosity of at least 10%, at least 15%, at least 20%, at least 25%, at least 30 %, at least 40%, at least 50% or more than 50% compared to the viscosity of the mixture at the beginning of the test. For plots that display viscosity measurements compared to the mixing time of colloidal silica and sodium silicate, the gel formation time can be estimated as the time elapsed to reach the inflection point of the time-viscosity curve. Gel formation times for the different formulations used at these temperatures are shown in Table 9.

TABLE 9

[00186] Gel formation time under various test temperatures:

[00187] As shown in Table 9, the gel formation time varied with the temperature and concentrations of the modified colloidal silica and sodium silicate accelerator.

EXAMPLE 11 CORE FLOOD TEST:

[00188] The injection capacity and long-term stability of the gel systems inside the pores were analyzed. Core flooding tests were carried out using limestone core plugs with porosity of 24% and brine permeability of 400 milliDarcy (mD) and the composition containing Colloidal Silica 8. An initial stable state was reached by pumping ca. 50 pore volumes as pre-flow before chemical treatment using the composition. The initial pressure drop was about 1 psi (0.07 bar) under constant flow velocity of 1 cm3/min. This was followed by the main water shut-off treatment stage.

[00189] To measure the injection capacity of the composition prior to field application, two core flow tests were conducted. In the first core test, no clay stabilizer (chloride salt) was used with the composition. Figure 4A displays the pressure drop and number of pore volumes during preflow injection and water shut-off treatment. During chemical injection, a significant pressure increase of 340 psi (23.4 bar) was observed after injecting five pore volumes. The increase can be attributed to the swelling of the clay.

[00190] In the second core test, clay stabilizer and surfactant (mixture of alcohols and quaternary ammonium compounds) were added to prevent clay swelling and increase the injection capacity of the composition. The results of the second core test exhibited a significant increase in injection capacity during chemical treatment when clay stabilizer and surfactant were added to the main treatment stage. In total, seven pore volumes were injected with little increase in injection pressure (7 psi/0.5 bar) compared to the first core test. After core stage injection, the flow was closed for curing.

EXAMPLE 12 RESISTANCE TEST (LONG-TERM CONSTANT PRESSURE EXPERIMENT):

[00191] After a curing time of 72 hours, the formation brine was injected into a post-injection process to determine the closing efficiency of the chemical treatment, measuring the differential pressure across the core as shown in Figure 4B. In a typical long-term constant pressure experiment, a formation brine was injected through a core cap using a pump at a constant flow rate of 1 millimeter per minute (ml/min) and the pressure differential was measured. along the core cap throughout the entire injection process. When the pressure on the core cap reached the desired pressure, the pump was set to constant pressure mode and the differential pressure and flow velocity were measured. The pump was kept in operation for several days to determine shutoff efficiency. Absence of pressure reduction and absence of effluents indicated that the porous medium (the core cover after chemical treatment) was completely closed. The formation brine contained the following composition: 50,500 milligrams per liter (mg/l) sodium ions, 24,300 mg/l calcium ions, 891 mg/l magnesium ions, 732 mg/l sulfate ions , 123,000 mg/l of chloride ions and 22 mg/l of bicarbonate ions. Following post-injection, a stress test began and the differential pressure was maintained at 800 psi (55.2 bar) for 3.5 hours and then maintained at 300 psi (20.7 bar) for three hours. The differential pressure was then maintained at about 500 psid (34.5 bar-d) for about 380 hours with minimal leakage through the treated core cap. The average leak velocity measured during this period was 0.0018 cm3/min. After fifteen days at 148 °C, a second high pressure stability test was conducted to determine the maintenance pressure of the chemical cap. For the second high pressure stability test, the pump used to supply pressure was switched from constant pressure mode to constant flow mode and the pressure applied to the core cover reached 2400 psi (166 bar). The pump was switched back to constant pressure mode and the pressure drop averaged about 2300 psid (159 bar-d) with no evidence of flow through the cap sample.

[00192] Specific realizations of the object were therefore described. Other embodiments are within the scope of the claims.

Claims (43)

1. GELLIFIED COMPOSITION, characterized by comprising: - modified colloidal silica, in which at least part of the silanol groups on the surface of an unmodified colloidal silica is replaced by an organosilane portion; and - an accelerator which is an organic or inorganic salt comprising one or more cations; where the molar ratio between silica and cation (X) of the gelled composition is defined by the equation: where the value of and wherein the gelled composition is present in an underground zone. 2. COMPOSITION, according to claim 1, characterized in that the organosilane portion comprises a silicon atom linked to one, two or three R1 groups by a direct Si-C bond, and in which: - each R1 is independently selected from the group that consists of i) alkyl, ii) epoxy alkyl, iii) alkenyl, iv) aryl, v) heteroaryl, vi) C1-6 alkylaryl, and vii) C1-6 alkylheteroaryl, any of which is optionally substituted by one or more groups selected from ER2, isocyanate and isocyanurate; - E is absent or a linking group selected from the group consisting of -O-, -S-, -OC(O)-, -C(O)-, -C(O)O-, -C(O )OC(O)-, -N(R3)-, -N(R3)C(O)-, -N(R3)C(O)N(R3)-, and -C(O)N(R3) -; - R2 is selected from the group consisting of hydrogen, F, Cl, Br, alkyl, alkenyl, aryl, heteroaryl, C1-3 alkylaryl and C1-3 alkyl heteroaryl, and is optionally substituted by one or more groups selected from from the group consisting of hydroxyl, F, Cl, Br, epoxy, -OR3 and -N(R3)2; and - R3 is H or C1-6 alkyl. 3. COMPOSITION, according to claim 2, characterized in that R1 is a hydrophilic moiety or that becomes hydrophilic after hydrolysis. 4. COMPOSITION, according to claim 3, characterized in that R1 comprises a member selected from the group consisting of carboxyl, ester, epoxy, acyloxy, ketone, aldehyde, (meth)acryloxy, starch, hydroxyl, thiol, amino, ureido , isocyanate and isocyanurate. 5. COMPOSITION, according to claim 2, characterized in that R1 comprises an epoxy group or one or more hydroxyl groups. 6. COMPOSITION, according to claim 5, characterized in that R1 comprises a substituent ER2, wherein E is -O- and R2 is selected from the group consisting of epoxy C1-8 alkyl, substituted epoxy C1-8 alkyl and a alkyl substituted by hydroxyl. 7. COMPOSITION, according to claim 2, characterized in that R1 is a hydrophilic group comprising at least one heteroatom selected from O and N, and comprising no more than three consecutive alkylene groups (CH2). 8. COMPOSITION, according to claim 7, characterized in that R1 is selected from the group consisting of 3-glycidoxypropyl, 2,3-dihydroxypropoxypropyl, 2,3-dihydroxypropyl and 2,3-dihydroxypropoxypropyl. 9. COMPOSITION, according to claim 2, characterized in that modified colloidal silica is prepared by contacting unmodified colloidal silica with an organosilane reagent, wherein the organosilane reagent is selected from the group consisting of a compound having the formula T4-ySi— [R1]y, a siloxane that has the formula [R1]bT3-bSi{-O-SiT2-c [R1]c}a-O-SiT3-b [R1]b, and a disilazane that has the formula { [R1]bT3-bSi}2-NH, where: - y is from 1 to 3; - each a is independently from 0 to 5; - each b is independently from 1 to 3; - c is 1 or 2; and - each T is independently selected from the group consisting of halide, hydroxyl, C1-6 alkoxy, and C1-6 haloalkoxy. 10. COMPOSITION, according to claim 1, characterized in that the degree of modification on the surface (DM) of the colloidal silica modified by organosilane is defined by the equation: where DM is 0.8 to 4 molecules per nm2, A is Avogadro's constant, Norganosilane is the number of moles of organosilane reagent used, Silica is the extent of silica in colloidal silica, in m2g-1, and Msilica is the mass of silica in colloidal silica, in grams. 11. COMPOSITION, according to claim 10, characterized in that the DM is from 1 to 4. 12. COMPOSITION, according to claim 10, characterized in that the DM is 1 to 2. 13. COMPOSITION according to claim 1, characterized in that X is within a range selected from the group consisting of 8 to 25, 8 to 20, 10 to 50, 10 to 25 or 10 to 20. 14. COMPOSITION, according to claim 1, characterized in that the accelerator comprises one or more members selected from the group consisting of halides, silicates, sulfates, nitrates, carbonates, carboxylates, oxalates, sulfides and hydroxides. 15. COMPOSITION, according to claim 14, characterized in that the accelerator comprises at least one hydroxide and at least one silicate. 16. COMPOSITION according to claim 1, characterized in that a cation of the one or more cations of the accelerator is selected from the group consisting of alkali metal ions, alkaline earth metal ions, hydrogen ions, ammonium ions , primary organoammonium ions, secondary organoammonium ions, tertiary organoammonium ions and quaternary organoammonium ions. 17. COMPOSITION, according to claim 1, characterized in that a cation of the one or more cations of the accelerator is monovalent. 18. COMPOSITION, according to claim 17, characterized in that the monovalent cation is an alkali metal cation. 19. COMPOSITION, according to claim 18, characterized in that the monovalent cation is a sodium cation. 20. COMPOSITION, according to claim 18, characterized in that the monovalent cation is a potassium cation. 21. COMPOSITION, according to claim 1, characterized in that the accelerator is selected from the group consisting of sodium silicate, potassium silicate, sodium chloride, and sodium hydroxide. 22. COMPOSITION, according to claim 1, characterized in that the pH of the composition is 6 to 11. 23. COMPOSITION, according to claim 22, characterized in that the pH is 9 to 11. 24. COMPOSITION, according to claim 1, characterized in that the accelerator is present in an amount of 1 to 30% by weight of the composition. 25. COMPOSITION, according to claim 1, characterized in that the silica content of the composition is 3 to 55% by weight of unmodified silica. 26. COMPOSITION, according to claim 1, characterized in that the accelerator is present in an amount of 1 to 30% by weight of the composition and the silica content of the composition is 3 to 55% by weight of unmodified silica. 27. COMPOSITION, according to claim 1, characterized in that the accelerator causes or facilitates a reaction between the colloidal silica particles modified in the composition, which results in the formation of the gelled composition. 28. COMPOSITION, as defined in claim 1, characterized by comprising: - modified colloidal silica, in which at least part of the silanol groups on the surface of an unmodified colloidal silica is replaced by an organosilane portion; and - an accelerator which is an organic or inorganic salt comprising one or more cations; where the molar ratio between silica and cation (X) of the composition is defined by the equation: where the value of and wherein the composition is present in an underground zone and has a gel formation time of 1 to 48 hours at a temperature of 90 °C to 200 °C. 29. COMPOSITION, according to claim 28, characterized in that the organosilane portion comprises a silicon atom linked to one, two or three R1 groups by a direct Si-C bond; wherein - each R1 is independently selected from the group consisting of i) alkyl, ii) epoxy alkyl, iii) alkenyl, iv) aryl, v) heteroaryl, vi) C1-6 alkylaryl, and vii) C1-alkylheteroaryl 6, any of which is optionally substituted by one or more groups selected from ER2, isocyanate and isocyanurate; - E is absent or a linking group selected from the group consisting of -O-, -S-, -OC(O)-, -C(O)-, -C(O)O-, -C(O )OC(O)-, -N(R3)-, -N(R3)C(O)-, -N(R3)C(O)N(R3)-, and -C(O)N(R3) -; - R2 is selected from the group consisting of hydrogen, F, Cl, Br, alkyl, alkenyl, aryl, heteroaryl, C1-3 alkylaryl and C1-3 alkyl heteroaryl, and is optionally substituted by one or more groups selected from from the group consisting of hydroxyl, F, Cl, Br, epoxy, -OR3 and -N(R3)2; and - R3 is H or C1-6 alkyl. 30. COMPOSITION, according to claim 29, characterized in that R1 is a hydrophilic moiety or that becomes hydrophilic after hydrolysis. 31. COMPOSITION, according to claim 30, characterized in that R1 comprises a member selected from the group consisting of carboxyl, ester, epoxy, acyloxy, ketone, aldehyde, (meth)acryloxy, starch, hydroxyl, thiol, amino, ureido , isocyanate and isocyanurate. 32. COMPOSITION, according to claim 29, characterized in that R1 comprises an epoxy group or one or more hydroxyl groups. 33. COMPOSITION, according to claim 32, characterized in that R1 comprises a substituent ER2, wherein E is -O- and R2 is selected from the group consisting of epoxy C1-8 alkyl, substituted epoxy C1-8 alkyl and an alkyl substituted by hydroxyl. 34. COMPOSITION, according to claim 29, characterized in that R1 is a hydrophilic group comprising at least one heteroatom selected from O and N, and comprising no more than three consecutive alkylene groups (CH2). 35. COMPOSITION, according to claim 34, characterized in that R1 is selected from the group consisting of 3-glycidoxypropyl, 2,3-dihydroxypropoxypropyl, 2,3-dihydroxypropyl and 2,3-dihydroxypropoxypropyl. 36. COMPOSITION, according to claim 29, characterized in that the modified colloidal silica is prepared by contacting the unmodified colloidal silica with an organosilane reagent, wherein the organosilane reagent is selected from the group consisting of a compound having the formula T4-ySi— [R1]y, a siloxane that has the formula [R1]bT3-bSi{-O-SiT2-c [R1]c}a-O-SiT3-b [R1]b, and a disilazane that has the formula { [R1]bT3-bSi}2-NH, where: - y is from 1 to 3; - each a is independently from 0 to 5; - each b is independently from 1 to 3; - c is 1 or 2; and - each T is independently selected from the group consisting of halide, hydroxyl, C1-6 alkoxy, and C1-6 haloalkoxy. 37. COMPOSITION, according to claim 28, characterized in that the accelerator comprises one or more members selected from the group consisting of halides, silicates, sulfates, nitrates, carbonates, carboxylates, oxalates, sulfides and hydroxides. 38. COMPOSITION according to claim 28, characterized in that a cation of the one or more cations of the accelerator is selected from the group consisting of alkali metal ions, alkaline earth metal ions, hydrogen ions, ammonium ions , primary organoammonium ions, secondary organoammonium ions, tertiary organoammonium ions and quaternary organoammonium ions. 39. COMPOSITION, according to claim 28, characterized in that a cation of the one or more accelerator cations is monovalent. 40. COMPOSITION, according to claim 28, characterized in that the accelerator is selected from the group consisting of sodium silicate, potassium silicate, sodium chloride, and sodium hydroxide. 41. COMPOSITION, according to claim 28, characterized in that the accelerator is present in an amount of 1 to 30% by weight of the composition. 42. COMPOSITION, according to claim 28, characterized in that the silica content of the composition is 3 to 55% by weight of unmodified silica. 43. COMPOSITION, according to claim 28, characterized in that the accelerator is present in an amount of 1 to 30% by weight of the composition and the silica content of the composition is 3 to 55% by weight of unmodified silica.