|Title of Invention||
THERMAL INSULATION COMPOSITIONS CONTAINING ORGANIC SOLVENT AND GELLING AGENT AND METHODS OF USING THE SAME
|Abstract||ABSTRACT OF THE DISCLOSURE A thermal insulating packer fluid contains an organic solvent of low thermal conductivity and a gelling agent which is hydratable in the solvent. The composition is capable of inhibiting unwanted heat loss from production tubing or uncontrolled heat transfer to outer annuli. The viscosity of the composition is sufficient to reduce the convection flow velocity within the annulus.|
Field of the Invention
This invention relates to enhancement of the thermal insulation of production tubing or a transfer pipe by use of a novel thermal insulating composition which controls the heat transfer from the tubing or pipe to one or more surrounding annuli and the environment. The fluid viscosity of the composition is capable of reducing the convection (low velocity within the surrounding annulus of "he well or transfer pipe being treated.
Background of the Invention
Undesired heat loss from production tubing as well as uncontrolled heat transfer to outer annuli can be detrimental to the mechanical integrity of outer annuli. because productivity losses from the well due to deposition of paraffin and asphaltene materials, accelerate the formation of gas hydrates, and destabilize the permafrost in arctic type regions. The successful use of wellborc insulation fluids in the past several years has demonstrated that such fluids, added either into annulus or riser, can effectively reduce undesired heat loss.
For instance. U.S. Patent No. 6.489.270 discloses non-crosshnked insulating fluids which are easy to blend and pump into the annulus. Such fluids, when added either into an annulus or riser, effectively reduce undesired heal loss from the production tubing, or heat transfer to outer annuli.
Water-superabsorbent polymers are disclosed for use in gelled fluids as thermal insulating fluids in U.S. Patent Publication No. 20040059054. Such gelled fluids exhibited an inherently low thermal conductivity and the requisite viscosity. The fluid viscosity was generated by mixing the requisite amount, typically between from 0.1 to 10 weight percent, of polysaccharide into a brine system which may optionally contain a glycol, such as propylene glycol and a viscosifying polymer, such as carboxymelhyl hydroxypropyl guar. The resulting fluid, which r.rc easy to blend and pump at the rig site, reduces the heat loss from a hot annulus to a cold annulus h\ reducing the fluid thermal convection caused by the temperature differential between the high temperature environment of the inner annulus and low temperature environment of the outer annuli. Fluid thermal convection, which accounts for the
major portion of the heat transfer, is dependent on the fluid viscosity and mobility of the solvent, such as a water-polyol mixture.
Alternative materials which are more effective in the retention of heal have been sought. Such materials arc needed in order to improve the intrinsic thermal conductivity of the solvent system of insulation fluids.
Summary of the Invention
The invention relates to a thermal insulating composition capable of controlling the heat transfer from a production tubing or transfer pipe to one or more surrounding annuli and the environment. The composition, which exhibits enhanced thermal control and which is particularly effective for deepwatcr risers, contains an organic solvent of low thermal conductivity and a gelling agent hydratablc in the solvent. The composition is typically buffered to a pH above L) or 10. The fluid viscosity of the composition is capable of reducing the convection flow velocity within the surrounding annulus of the well or a transfer pipe.
The organic solvent is preferably isopropanol or a polyol selected from ethylene glycol, propylene glvcol. glycerol, butylene glycol, dteth; lene glycol and trimethylene glycol, polyethylene glycol. poly; 1.3-propa:iedio!;. po!yil.2-propancdiol). poly( 1.2-bulancdiol). polyt 1.3-bulancdiol). pn>i\( 1.4-butanediol). poly(2.3-butanediol). polyvinyl alcohol, copolymers and block polymers thereof. In a preferred embodiment, the organic solvent is ethylene glycol, prop)lene glycol, glycerol or diethylene glycol.
The gelling agent is preferably a synthetic polymer |such as polyacrylamide (like copolymers of acrylamide or (methlacrylamide and N-vinylformamide. N-vinylacetamde. N-vinylcaprolactam, N-vinylimidazole. N-vinylpyridine. vinyl phosphonalc. 2-acrylamido-2-methylpropancsulfonic acid. N-vinylpyrrolidone and/or acrylamidopropyltrimonium chloride] or a derivative thereof or a hydroxyalkylaled guar (such as hydroxypropyl guar or modified hydroxypropyl guar).or a polyacrylic acid, salt or copolymer thereof [such as a polymer containing acrylic acid, methyl acrylatc. ethyl acrylate. propyl acrylale. butyl acrylatc. octyl acrylate. dodccyl acrylate. (meth(acrylic acid, methyl (meth)acrylate. ethyl (mclh)acrylatc. propyl (meth (acrylate. isopropyl (meth (acrylate and butyl (meth (acrylate]] or a
In a preferred embodiment, the gelling agent is either a terpolymer of N-vinylformamide. 2-acrylamido-2-methypropanesulfonic acid and acryiamide or a copolymer of 2-acTyiamido-2-mcthy!propane sulfonic acid and acryiamide and. optionally. N-vmylpyrrolidonc or a terpolymer of acrylamidopropyl trimonium chloride, acryiamide and a nitrogen heterocyclic monomer such as N-vinyiformamide. N-vinylacetamide. N-vinylcaprolactam. N-vinylimidazole, N-vinyJpyricline or N-vinylpyrrolidone or a hydrophobically-modificd polyacrylic acid or acrylic acid/acrylatc copolymer.
The compositions of the invention provide high viscosity at low shear rate range to reduce convection flow velocity within the annulus. In addition, the compositions oi' the invention provide lower viscosity at high shear rate range to facilitate the fluid placement.
Brief Description of the Drawings
In order to more fully understand the drawings referred to in the detailed description of the present invention, a brief description of each drawing is presented, in 'which:
FIG. 1 illustrates the concentric tube dimensions for a heat tian>fcr apparatus used to determine the thermal insulation effectiveness of exemplified fluids.
FIG. 2 illustrates convection rateshcat retention ability exhibited by the thermal insulating fluid of the invention (Fluid II) versus an insulating fluid of the prior art (Fluid I), as discussed below in Example 5.
Detailed Description of the Preferred Embodiments
The thermal insulating composition of the invention is capable of reducing heat transfer from production tubing or a transfer pipe in a wellbore to the environment or surrounding annuli. The composition contains a solvent of low-thermal conductivity and a viscosifying polymer or gelling agent hydralable in the solvent.
The solvent imparts low thermal conductivity to the composition and thereby provides the desiredhighly desirable thermal insulation. Typically, the intrinsic
thermal conductivity of the solvent is (can a number or range be given
here?)below 0.38 BTU/(hr-ft-"F).
Preferred solvents include isopropanol. glycols such as ethylene glycol, propylene glycol, glycerol, butyiene glycol, diethylene glycol and trimethylene glycol and such polyglycols as polyethylene glycol. poiy( 1.3-propanediol). polytl.2-propanediol). poly( 1.2-butanediol). poly( 1.3-bulancdiol). poly( 1.4-bulancdiol). poly(2.3-butanedioli, copolymers, block polymers and mixtures of these polymers. The polyglycols typically have a molecular weight between from about 4.000 to about 6.000. In a preferred embodiment, the organic solvent is ethylene glycol, propylene glycol, glycerol and diethylene glycol.
Water is preferably not typically used in conjunction with the solvent though water may be used in trace amounts in the composition, such as a portion of a crosslinking system and/or buffer. Typically, the amount of water in the composition Any gelling agent capable of being hydraled in the low thermal conductivity solvent
is acceptable. The gelling agent is not greater than about weight percent. In
one embodiment of the present invention, the thermal insulating fluid is substantially free of water.
Any gelling agent capable of being hydrated in the low thermal conductivity
solvent is acceptable. The gelling agent should be capable of rendering a viscosity of
from about 100 to about 2000 cps '?' 25°C100 ^ec"' fo the composition.
In a preferred embodiment, the gelling agent is a polyacrylamide or derh alive thereof, preferably a copolymer of acryiamide or (meirOau'vlamide or a hydrophobically-modified polyacrylic acid/acrylate copolymer. Suitable comonomers include N-vinylformamide. N-vinylacetamde. N-vinylcaprolactam. N-vinylimidazole. N-vinylpyridinc. 2-acrylamido-2-methylpropanesulfonic acid. N-\ mylpyrrolidonc and acrylamidopropyltrimonium chloride. Typically, the copolymers are comprised of two distinct monomers in a 10:90 to 90:10 weight percent ratio of acryiamide to other comonomer.
Also preferred are polyacrylic acids, salts and copolymers thereof. Such polymers may be produced from ai least one monomer selected from the group consisting of acrylic acid, (meth)acrylic acid, aikyl acrylate and alkyl (meth (acrylate such as methyl acrylate. ethyl acrylate. propyl acrylate. butyl acrylate. octyl acrylate. dodecyl acrylate. (meth)acrylic acid, methyl (mcth)acrylatc. ethyl (meth)acrylatc. propyl tmclh(acrylate. isopropyl (meth(acrylate. butyl (meth (acrylate and the like. For instance, the polymers may be acrylate copolymers of C|-C:r,-alkyl (meth(acrylate anci (ineiniacrvjH' acHr as vveu as iinetulacrviic acici anci at teas; iv-.;- cUiieieu; ■_ ■_;;.
containing acrylamide or acrylonitnle. A particularly suitable acrylate copolymer dispersion is obtainable commercially under the designation Viscalex EM 15 iCiba Specially Chemicals).
Further preferred are hydrophobically-modified polyacrylic and acrylic/acrylate copolymers. Such polymers include Aculyn™ 28. a hydrophobically-modified alkali soluble emulsion (HASE). commercially available from Rohm and Haas Company. Such HASE products arc disclosed in U.S. Patent No. 6.063.857. herein incorporated by reference.
Such polymers may be lightly crosslinked with a crosslinking agent, preferably those which contain two or more terminal polymeri/.ablc ethylenic groups per molecule. Examples of such crosslinking agents are N.N'-melhylcne-bis-acrylamide, N.N'-methylene-bis-(meth)acrylamide, diallyl amine, diallyl acrylamide. diallyl (meth)acrylamide. diallyl ether, diallyl methyl ether, divinyl benzene, diethylene glycol divinyl ether, ethylene glycol diacrylale. ethylene glycol diunethiaerylale. propylene glycol diacrylale. propylene glycol di(meth)acrylale. diethylene glycol diacrylale. diethylene glycol didnethkicrylate. tetraethylene glycol diacrylale. fetraethyleae glycol ditrneth (acrylate. ally I acrylate. ally! dneth (acrylate. irimclhylolpropanc diallyl ether, polyethylene glycol diallyl ether. trimetlnlolpropanc Iriacrylatc. Irimclhylolpropanc lri(mclh)acrylalc. 1.6 hexanediol diacnlate. pentaerythritol triacrylate. glyceryl/propoxy triacrylate and the like. Preferred crosslinking agents are N.N'-metlwlene-bis-acrylamide. triinethyloipropandiaflylether and polyclliylcneglycol diallylethcr. The amount of crosslinking agent may be varied to suit specific requirements: the amount of crosslinking agent typically varying from about 0.03 to 5.0c/r (by weight based on monomer). The amount of crosslinking agent typically used is between from about 0.05 to 2.09r by weight of gelling agent.
Preferred copolymers are lerpolymcrs of the copolymers containing terpolymer of (i.) N-vinylformamide. (ii.) 2-acrylamido-2-mclhypropanesulfonic acid and (iii.) acrylamide. optionally crosslinked, as well as copolymers of 2-acrylamido-2-methylpropane sulfonic acid and acrylamide. and optionally. N-vinylpyrrolidone and lerpolymcrs of acrylamidopropyl trimonium chloride, acrylamide and a nitrogen heterocyclic monomer selected from the group consisting of N-vinylformamide. N-vinylacetamide. N-vinylcaprolactam. N-vinylimidazole. N-vinylpyridine and N-
vinylpyrrolidone. Typically, each of the monomers in the terpolymers is present in an amount from about 5 to about 90 weight percent.
In a most preferred embodiment, the copolymer contains about 30 weight percent of 2-acrylamido-2-methyIpropanesulfonic acid. 15 weight percent of N-vinylformamide and 54.5 weight percent aerylamide and has been crosslinked with about 0.5 weight percent of a crosslinking agent of triinethylolpropane diallylether or polyelhyleneglycol diallylether.
Further preferred arc hydroxyalkylatcd guars, such as hydroxypropyl guars, preferably those having a molecular weight of about 1.5 to about 3 million and wherein the molar substitution (defined as the number of moles c f hydroxypropyl groups per mole ofanhydrogluco.se) is between from about 0.95 to about 1.05. (This describes GM-60 of BJS. Any issue in disclosing the product in this fashion. Note that the examples refer to GM-60 without specifying the particulars recited in this paragraph).
Also preferred are polyacrylic acids, salts and copolymers thereof. Such polymers may be produced from at least one monomer selected from (he group consisting of ncrvlic acid, methyl acrykire. ethyl acrvlate. piMp\; acrvlate. hutvl acrylate. octyl acrvlate. dodecyl acrylate. (methiacrylic acid. rneth\ i (meth lacnlate. ethyl (meth(acrylate. propyl (meth (acrylate. isopropyl imeih lacrylaie. butyl (meth (acrylate and the like. For instance, the polymers may be acnlaic copolymers of CrC„-alkyl (meth(acrylate and (meth(acrylic acid as well as (methiacrylic acid and at least two different C\-C(] -alkyl (meth(acrylate monomers. Further, the polymers may be acrylate copolymers containing aerylamide or acrylonilrile. A particularly suitable acrylate copolymer dispersion is obtainable commercially under the designation Viscalex EM 15 (Ciba Specialty Chemicals).
The composition is preferably buffered, in order to improve thermal stability and prevent polymer degradation, to a pH above 9 or 10. Suitable buffering agents known in the art. such as potassium carbonate and potassium bicarbonate, are acceptable. Typically, the amount of buffer used in the composition is less than about 0.02 weight percent.
The composition of the invention may further contain a biocide and/or corrosion inhibitor. Further, the composition may contain a crosslinking agent and clay and clay-like materials to impart viscosity to the composition. Materials suitable
for use in the invention are those known in the art and are employed in amounts recognized in the art.
Thus, an insulating fluid with superior insulation properties can be formulated by using between from about 0.05 to about 20%. preferably aboui 1%. by weight of copolymer based on 100% by volume of solvent. A preferred formulation for use in the invention contains 100 volume percent of propylene glycol as solvent and 4 pound/barrel of gelling agent. The thermal insulating composition of the invention may further
contain a saturated or unsaturated brine in the amount of from about to about
weight percent. By saturated brine, it is understood that the brine is saturated
with at least one salt, such as sodium bromide.
Further preferred are guar derivatives, such as hydoxyalkylaied guars like hydroxypropyl guar, hydroxyethyl guar and hydroxybutyl guar and modified hydroxyalkylated guars like carboxymethylhydroxypropyl guar, preferably those having a molecular weight of about 1.0 to about 3 million and wherein the molar substitution (defined as the number of moles of hydroxyalkyl groups per mole of aiihvdroglueose) is between from about O.S0 to about ) .20.
The composition is preferably buffered, in order to improve thermal stability and prevent polymer degradation, to a pH above 10. Suitable buffering agents known in the art. such as potassium carbonate and potassium bicarbonate, primary amine compounds are acceptable. Typically, the amount of buffer used in the composition is less than about 0.02 weight percent.
The composition of the invention may further contain a biocide and/or corrosion inhibitor. Further, the composition may contain a cross linking agent and clay and clay-like materials to impart enhanced viscosity to the composition. Materials suitable for use in the invention are those known in the art and are employed in amounts recognized in the art.
In a preferred embodiment of the present invention, the thermal insulating fluid is substantially free of water. As such, the insulating fluid of the invention exhibits superior insulation properties and may be formulated by using between from about 0.05 to about 20%. preferably about 1%.. by weight of copolymer based on 100% by volume of solvent. A preferred formulation for use in the invention contains close to 100 volume percent of propylene glycol as sohent anci 4 pound/barrel of
While water is preferably not used in conjunction with the solvent, wate (including saturated or unsaturated brine) may be used in small amounts in the composition, such as a portion of a crosslinking system and/or buffer. The amount of water (brine) in the thermal insulating composition of the invention is typically no greater than about 25 volume percent. By saturated brine, it is understood that the brine is saturated with at least one salt, such as sodium bromide.
The thermal insulating compositions of the invention may further contain a crosslinking metal-releasing agent. As used herein, the term "crosslinking metal-releasing agent" is taken to designate those metal or metal containing materials which will provide a metal ion or metal containing species in the solution capable of crosslinking the viscosifying polymer.
The crosslinking agent preferably comprises a borate ion releasing compound, an organometallic or organic complexed metal ion comprising at least one transition metal or alkaline earth metal ion as well as mixtures thereof, such as Zr (IV) and Ti (IV). Typically, the crosslinking agent is employed in the composition in a concentration of from about 0.001 percent to about 2 percent, preferably from about 0.OO5 percent to abort 1.5 percent, and. movi preferabh. from abour O.Oi percent so about 1.0 percent.
Borate ion releasing compounds which can be employed include, for example, any boron compound which will supply borate ions in the composiiion. for example, boric acid, alkali metal borates such as sodium diborate. potassium tetraborate, sodium tetraborate (borax), penraborates and the like and alkaline and zinc metal borates. Such borate ion releasing compounds arc disclosed in U.S. Pal. 3.058.909 and U.S. Pal. No. 3.974.077 herein incorporated by reference. In addition, such borate ion releasing compounds include boric oxide (such as selected from hhBCh and B2O3) and polymeric borate compounds. An example of a suitable polymeric borate compound is a polymeric compound of boric acid and an alkali borate which is commercially available under the trademark POLYBOR® from U.S. Borax of Valencia. Calif.. Mixtures of any of the referenced borate ion releasing compounds may further be employed. Such borate-releasers typically require a basic pH (e.g.. 7.0 to 12) for crosslinking to occur.
Further preferred crosslinking agents are reagents, such as organometallic and organic complexed metal compounds, which can supply zirconium IV ions such as.
carbonate, zirconium aeetylacetonate and zirconium diisopropylamine lactate: as well as compounds that can supply titanium IV ions such as. for example, titanium ammonium lactate, titanium triclhanolamine. and titanium aeetylacetonate. Zr (IV) and Ti (IV) may further be added directly as ions or oxy ions into the composition.
Such organometallic and organic complexed metal crosslinking agents containing titanium or zirconium in a +4 valence state include those disclosed in British Pal. No. 2.108.122. herein incorporated herein by reference, which are prepared by reacting zirconium tctraalkoxides with alkanolamincs under essentially anhydrous conditions. Other zirconium and titanium crosslinking agents are described, for example, in U.S. Pat. No. 3.888.312: U.S. Pat. No. 3.301.723: U.S. Pat. No. 4.460.751: U.S. Pal. No. 4.477.360: Europe Pat. No. 92.755: and U.S. Patent No. 4.780.223. all of which arc herein incorporated by reference. Such organometallic and organic complexed metal crosslinking agents containing titanium or zirconium in a +4 oxidation valance state may contain one or more alkanoiamine ligands such as cthanolaminc (mono-, di- or triclhanolamine) ligands. such as bis(trielhanolamine)bis(isopropol)-lilanium (IV). Further, the compounds may be supplied as inorganic oxides, such as zirconium or titanium dioxide. Such crosslinking agents are typically used at a pH also in the range from about 6 to about 13.
Any suitable crosslinking metal ion. metal containing species, or mixture of such ions and species may further be employed. In a preferred embodiment, the crosslinking agent for use in the thermal insulating composition of die invention are reagents capable of providing Zn (II). calcium, magnesium, aluminum. Fe (II). and Fc (III) to the composition. These may be applied directly to the composition as ions or as polyvalent metallic compounds such as hydroxides and chlorides from which the ions may be released.
The crosslinking ions or species may be provided, as indicated, by dissolving into the solution compounds containing the appropriale metals or the metal ion per sc. The concentration of crosslinking agent is dependent on factors such as the temperature in the annuli and will normally range from about 5 ppm to about 2000 ppm. preferably from about 100 ppm to about 900 ppm. It is an important advantage of the invention that higher levels of ihe crosslinking metal ion or metal containing species may be employed, thereby insuring improved crosslinking. When desired.
crosslinking typically occurs after the thermal insulating composition is within the annul i.
Zirconium crosslinkers. such us those described in British Pat. No. 2.108.122. are a preferred class o[ crosslinkers for use herein. Such crosslinkers are preferred because of their "delayed" or "retarded" crosslinking reactivity. This delayed activity is useful because it lets the operator formulate and pump the uncrosslinked composition while it has a relatively lower viscosity which means easier pumping. The delayed systems arc usually designed to crosslink while the fluid is being pumped through the wellbore tubing and/or as the fluid enters into the annuii.
The thermal insulating composition of the invention is prepared on the surface and then pumped through tubing in the wellbore or in the annulus. In a preferred embodiment, the fluid is a packer or riser fluid and the packer'"fund is introduced above the packer in an annulus and the riser fluid is introduced into a riser annulus.
While high viscosity, thickened fluid is highly desirable after the fluid is positioned in the annulus, large amounts of energy are required to pump such fluids through tubing and annular spaces. Crosslinking. when desired, may be delayed, thereby reducing the amount of energy required to pump viscoth fluids through the tubing by permitting pumping of a relatively less viscous fluid having relatively low friction pressures within the well tubing. Crosslinking is typically affected when the fluid is placed in the annulus after which the advantageous properties of thickened crosslinked fluid are then available for thermal insulation.
The composition, when pumped into an annuii surrounding the production tubing or transfer piping, enhances the thermal insulating quality around the tubing or piping, thereby reducing heat loss from it. The composition further pan ides high viscosity at low shear rate so as to reduce the rate of fluid convection to near zero. Since convection is fluid motion caused by the variation of fluid density with temperature, increasing fluid viscosity decreases fluid motion, and correspondingly, decreases free annular convection. Thus, the desired rheological profile for the insulating fluid of the invention includes high viscosity at low shear rate in order to reduce the free fluid convection caused by temperature differential. Additionally, a low viscosity at high shear rate is desired to facilitate the placement of the insulating fluid at the desired location.
The thermal insulating compositions should be approached on a specific
normally dictated by the required hydrostatic pressure needed to control the well, and may be achieved by the amount and type of salt dissolved within the composition (resulting from the brine, etc). The densities of (he thermal insulating compositions of the invention are controlled by operational considerations such as additives to the fluids, hydration time of viscosifier. and requirements for low crystallization temperatures (both true crystallization temperature (TCT) and pressure crystallization temperature (PCT). Densities lo 13.0 pounds per gallon have been evidenced. It is important that the compositions are formulated lo have an appropriate low crystallization temperature for the adverse conditions of deep water. The crosslinked insulating compositions have low pressure crystallization temperatures significantly less than 30°F at 10.000 psi.
The thermal insulating composition of the invention may be produced in shore-based facilities, transported to. and pumped from marine well-servicing boats into riser annuli. This provides a convenient means to blend, temporarily store, and then pump large quantities of fluid into the wellborc and riser annuli. without using rig tanks.
The thermal insulating composition of the invention further offers environmental benefits since no oil sheen will be produced if (lit composition is spilled since the composition is oil-free. Further, while the fluid compositions vary according lo specific well conditions, the components of the composition are environmentally friendly especially since the composition is solids-free.
The composition of the invention may serve a dual purpose. First, they serve lo prevent heat transfer/buildup in the outer annuli. Second, they serve lo retain heal within the produced hydrocarbons. The compositions further provide lower viscosity at high shear rate to facilitate the fluid placement.
The following examples will illustrate the practice of the present invention in a preferred embodiment. Other embodiments within the scope of the claims herein will be apparent lo one skilled in the arl from consideration of the specification and practice of the invention as disclosed herein. It is intended that the specification, together with the example, be considered exemplary only, with the scope and spirit of the invention being indicated by the claims which follow.
Unless stated to the contrary, all percentages expressed herein., refer to weight percentage.
The following abbreviations are further used:
CMHPG refers to carboxymelhyl hydroxypropyl guar;
HE-100 refers to a copolymer of 2-acrylmideo-2-methylpropnesulfonic acid and acrylamide. a product of Drilling Specialty Company:
HE-300 refers to a tcrpolymers of 2-acrvlamido-2-methvlpropane sulfonic acid, acrylamide and N-vmylpyiTolidone. commercially available from Drilling Specialty Company;
GM-60 refers to a modified hydroxypropyl guar, a product of BJ Services Company;
Non-crosslinked insulating fluid or ABIFATTF. disclosed in II.S. Patent Application No. 20040059054. consists of 4 pound per barrel (ppb) of CMHPG. am) 2 ppb of superabsorbent polymer G-504 (a Water Lock product from Grain Processing Corp.. Muscatine. Iowa) respectively, lo 9.0 ppg brine, the brine consisting of water, propylene glycol (25 volume r>- ). and sodium bromide sail.
Our Examples do not recite the addition of pH buffering nor do they recite the pH of the fluids. Is this an important parameter? If so. the pH should be recited.
Example 1. Example 1 examines the rheology of insulating fluids of the invention.
4 g of HE-100 was added to 350 mis of propylene glycol while stirring. After hydraling the mixture by mechanical stirring for 30 minutes and adjusting die pH above 10.0 with K2CO,. a 50 ml sample of the hydrated fluid was placed into a Fann 50° C viscometer cup. The cup was then placed on a Fann 50' C viscometer and pressured to about 300 psi (14 kg/cm") with nitrogen. The s sample was then sheared at 100 sec"1 for 28 minutes at 120° F, followed by a rale sweep using 100. 75. 50. and 25 sec"1 for about 2 minutes. The oil bath temperature was pre-scl to 49" C and the bath was raised ro submerge the sample cup. The rate sweep was repeated ever}' 28 minutes, and the interim rate between sweeps was 100 sec" . The stresses associated to each rale used in the sweep together with the rales were used lo calculate the power law indices n and K; wherein n refers lo flow behavior indeN and K refers lo
Tables I and 11 show that the insulating fluids of the invention exhibit an acceptable viscosity profile while using pure organic solvent to hydrate the polymer.
The rheologicai properties of the insulating fluids may be adjusted by altering the concentration of polymer in order to provide a convenient means to blend, temporarily store, and then pump large quantities of fluid into the uellbore and riser annuli. without using rig tanks.
Example 2. Example 2 examines the thermal insulation effectiveness of certain fluids using a laboratory-sized heat transfer apparatus.
Two fluids were prepared in accordance with the procedure of Example 1 but using 4 lbs/barrel GM-60 and 4 lbs/barrel HE-100. The thermal insulating properties of thermal insulating fluids were evaluated in a laboratory-sized heat transfer apparatus to determine the thermal effectiveness of the fluids. These fluids were contrasted with pure solvent and ABIF. The heat transfer apparatus consisted of three concentric aluminum pipes connected and scaled by two flanges. The physical dimensions are shown in FIG. 1. Hot fluid at constant temperature was circulated in the inner pipe, while cold fluid at constant temperature was circulated in the outer annulus. The test insulating-fluid was contained in the annulus between the hot and cold reference fluids. The top and bottom of the apparatus were insulated to assure that heat flow was in the radial direction.
About 7000 ml of the fluid was placed into the annulus of a laboratory-sized heat transfer apparatus for the test on each fluid. Hot fluid was allowed to enter the inner pipe at the bottom and leave the pipe at the top at approximately 0.3-1 gallon/minute and thus provided a hot surface at the inner annulus wall. The cold water was fed to the outside pipe of the heat transfer apparatus with a flow rate of 3 gallon/minute to provide a cold wall annulus adjacent to the packer annulus. The test insulating-fluid remained static in the packer annulus. Thermocouples were positioned on the inner wall (hot surface) and outer wall (cold surface) of the annulus. and at the inlet and outlet ports for the hot and cold flowing water.
During the test, hot water and cold water temperatures were set at 1 bS0°F and 50°F. respectively. After thermal equilibrium was achieved (2 to 3 hours) for a given test, data was collected to calculate heat transfer coefficient and apparent thermal conductivity and summarized in Table II:I: III:
conductivity and summarized in Tabic III IV:
(020569/11480-NO) (BJS REF. NO. P205-1463-IN
1. A thermal insulating composition useful for controlling heat transfer from a production tubing or transfer pipe in a wellbore to one or more surrounding annuli and/or the environment, the composition comprising an organic solvent of low thermal conductivity and a gelling agent hydratable in the solvent, wherein the fluid viscosity of the composition is capable of reducing the convection flow velocity within the surrounding annulus of the well or the production rube and/or transfer pipe and further wherein the gelling agent is selected from the group consisting of hydrophobicaily-modified polyacrylic and acrylic/acrylate copolymers and guar derivatives having a molecular weight of 1.0 to 3 million and having a molar substitution between from 0.80 to 1.20.
2. The thermal insulating composition of Claim 1. wherein the organic solvent is isopropanol or a polyol. such as ethylene glycol, propylene glycol, glycerol, butylene glycol, diethylene glycol and trimethylene glycol, polyethylene- glvcol. polv(1.3-nropanedioli. polyi 1.2-propanediol). polyt 1.2-bulanedioIi. p'-iv? !.3-bulancdioli. polyf 1.4-butancdioi). poiy(2.3-butanedio!!. polyvinyl alcohol, copolymers, block polymers and mixtures thereof.
3. The thermal insulating composition of Claim 1 or 2. wherein the:
(a! gelling agent is capable of rendering a viscosity of from about 100 to about 2000 cps @- 100 sec"' at 25°C to the composition: and/or
(b) amount of gelling agent present in the composition is between from about 0.05 lo about 20 percent by weight based on 100 percent by volume of organic solvent: and/or
(c) composition is buffered to a pH above 10.
4. The thermal insulating composition of any of Claims 1 to 3, wherein the guar derivative is a hydroxyalkylated guar or modified hydroxyalkylated guar, such as hydroxypropyl guar. hydroxyethyl guar. hydroxybutyl guar and carboxymethylhydroxypropyl guar.
5. The thermally insulating composition of any of Claims i io 4. wherein the composition is substantially free of water.
6. The thermal insulating composition of any of Claims 1 to 5. wherein the gelling agent is a hydrophobically modified polyacrylic acid or acrylic acid/acrylate copolymer, optionally crosslinkcd with a crosslinking agent having al leasi two terminal polymerizable ethylenic groups.
7. The thermal insulating composition of any of Claims 1 to 6. further comprising a crosslinking metal-releasing agent, such as borate ion releasing compounds, organometallic titanium containing crosslinking agents or organometallic zirconium crosslinking agents or N.N'-methylene-bis-acrylamide. N.N'-methylene-bis-(methiacrylamide. diallyl amine, dialiyl acrylamide, diallyl (meth)acrylamide. diaIKi ether, diallyl methyl ether, divinyl benzene, dicthylenc glycol divinyl ether, ethylene glycol diacrylate. ethylene glycol diunethlacrylate. propylene glycol diacrylate. propylene glycol di(melh)acrylate. diethylene glycol diacrylate. dicthylenc glycol di(meth)acrylate. tetraethylene glycol diacrylate, tetraethylene glycol di(meth:acrylate, ally! acrylate. allyl (meth)acrylate. trimethylolpropane diallyl ether, polyethylene glycol diallyl ether, trimethylolpropane triacrylate. trimethylolpropane iriuncihiacrylaie. l.ti hexanediol diacrylate. peniacrythritol triacrviatc or civecrvi/pr, >po\\ triacetate.
8. A method for enhancing ihe thermal insuia'non of a produciion ui'ning ur
transfer pipe surrounded by al least one annuli. comprising:
adding the fluid composition of any of Claims 1 to 7 to the at least one annuli: and maintaining the fluid in contact with the at least one annuli to at least partially immobilize the fluid composition.
9. A method for reducing convection flow velocity in at least one annuli
surrounding a production tubing or transfer pipe, comprising:
introducing into the at least one annuli an insulating packer or riser fluid comprising the fluid composition of any of Claims 1 to 7: and
maintaining the fluid in the at least one annuli until the convection flow velocity is reduced.
10. The method of Claim 9. wherein the fluid composition is a packer or riser
fluid and further wherein the packer fluid is introduced above the packer in an annulus
|Indian Patent Application Number||6026/CHENP/2008|
|PG Journal Number||19/2014|
|Date of Filing||06-Nov-2008|
|Name of Patentee||BJ SERVICES COMPANY|
|Applicant Address||4601 WESTWAY PARK BOULEVARD, HOUSTON, TEXAS 77041|
|PCT International Classification Number||C09K8/592|
|PCT International Application Number||PCT/US07/10811|
|PCT International Filing date||2007-05-04|