EP2906660A1

EP2906660A1 - Methods of preventing emulsification of crude oil in well bore treatment fluids

Info

Publication number: EP2906660A1
Application number: EP13844827.9A
Authority: EP
Inventors: Philip W. Livanec; Gregory P. Perez; Jay P. Deville
Original assignee: Halliburton Energy Services Inc
Current assignee: Halliburton Energy Services Inc
Priority date: 2012-10-11
Filing date: 2013-10-10
Publication date: 2015-08-19
Also published as: WO2014059167A1; BR112015007806A2; CA2886931A1; EP2906660A4; AU2013329180B2; MX369071B; EA031903B1; MX2015004318A; EA201590499A1; AU2013329180A1; AR092926A1

Abstract

Of the many compositions and methods provided herein, one method includes a method of preventing emulsification of crude oil into an aqueous-based treatment fluid, comprising: contacting crude oil in a well bore with the aqueous-based treatment fluid comprising a styrene-acrylate copolymer, wherein the crude oil has an API gravity of about 10 or greater; and allowing the styrene-acrylate copolymer to interact with the crude oil in the well bore.

Description

METHODS OF PREVENTING EMULSIFICATION OF CRUDE OIL IN WELL

BORE TREATMENT FLUIDS

BACKGROUND

5 [0001 ] The present invention relates to methods and compositions for use in subterranean operations. More particularly, the present invention relates to styrene-acrylate copolymers used to treat tar and/or crude oil resident in a well bore and associated methods of use.

[0002] Many subterranean operations involve the drilling of a well bore from the

S O surface through rock and/or .soil to penetrate a subterranean formation containing fluids that are desirable tor production. In the course of drilling operations and other subterranean operations, the dril lstring and/or other equipment may come into contact with zones of rock and/or soil containing tar and/or crude, oil, such as heavy and light (liquid) hydrocarbons, asphalt, and bitumens; in many such operations_* tt may be desirable to drill the well bore

15 through these zones containing tar and/or liquid crude. However, problems may be encountered when these zones are encountered. For example, erode oil present in the /one{s) ma enter the well bore and emulsify or otherwise disperse into the drilling fluid. This is problematic in that contamination of the drilling fluid with the crude oil can undesirably impact the fluid properties, as well as present complications with fluid disposal. If the 0 drilling fluid is contaminated, extra precautions may need to be used for removal of the. crude oil from the drilling fluid such that the .surrounding environment is not polluted. Various techniques have been used to remove crude oil from drilling fluid to prevent oil pollution. In one technique, deroulsifiers can be used to break the oil-i.n-water emulsion. In another technique, heat can he used to break the emulsion. However, both of these techniques can be 5 difficult to implement in the field, as emuisification of crude oil into the drilling fluid can often form very strong emulsions that are hard to break.

[0003] In addition to problems drilling through iiquid-emde-confaining zones, problems may also be encountered when a zone or zones containing tar are encountered. Tar is a relatively tacky substance thai may readily adhere to any surface that it contacts, 0 including the surfaces of the well bore and/or an equipment utilized during the drilling operation. Tar also may dissolve into many synthetic treatment fluids used in the course of drilling operations, increasing the tacky and adhesive properties of the tar. If a sufficient amount of tar adheres to surfaces in the well bore or drilling equipment, it may, among other problems, prevent the drillstr g from rotating, prevent, fluid circulation, or otherwise impede 5 the effectiveness of a drilling operation. In some cases, it may become necessar to remove and/or disassemble the dri.listri.ng in order to remove accretions of tar, a process which may

I create numerous cost and safety concerns. The accretion of tar on drilling equipment and/or in the well bor also can impede any subsequent operations downhole, including cementing, acidizing, fracturing, sand control, and remedial treatments. In addition, soft, tacky tar that manages to reach the surface may foul surface equipment, including solids screening equipment.

[0004] Existing methods of managing these problems that result from well bore tar incursion may be problematic. Some of these methods involve affecting an increase in hydrostatic pressure in the well bore so as to force the tar out of the well bore to the surface. However, this increased hydrostatic pressure may damage the well bore and/or a portion of the subterranean formation. Other conventional methods utilize treatment fluids that comprise dispersants, surfactants, and or solubilizers, which, allow the tar particles to dissolve in or homogenize with the treatment .fluids. However, the tar particles may not be .readily separated out. of the fluid once they have dissolved into or homogenized with the fluid. The presence of the tar particles in the treatment fluid may alter its rheologicai properties and/or suspension capacity, which may limit its use in subsequent operations. Moreover, the addition, of these dispersants, surfactants, and solubilizers may increase the complexity and. cost of the drilling operation.

SUMMARY

[0005] The present invention relates to methods and compositions for use in subterranean operations. Mor particularly, the present invention relates to styrene-aeryiate copolymers used to treat tar and/or crude oil resident in a well bore and associated methods of use.

0006] in one embodiment the present invention provides a method of method of preventing esmdsifleation of crude oil into an aqueous-based treatment fluid, comprising: contacting crude oil in a well bor with the aqueous-based treatment fluid comprising a styrene-aeryiate copolymer, wherein the crude oil has an API gravit of about 10 or greater; and allowing the styrene-aeryiate copolymer to interact with the crude oil in the well bore,

[0007] in another embodiment, the present invention provides a method of treating crude oil, comprising: using a drill bit to enlarge a well bore in a subterranean formation, wherein crude oil from the subterranean formation enters the well bore, wherein the crude oil has an API gravity of about H⁾ or greater; and circulating an aqueous-based drilling fluid past the drill bit, the aqueous-based drilling tluid comprising an aqueous fluid and a styrene- aeryiate copolymer, wherein the styrene-aeryiate copolymer interacts with the crude oil in the well bore such that the crude oil forms agglomerates in. the aqueous-based drilling fluid.

[0008] In another embodiment, the present invention provides a method of treating crude oil, comprising: using a drill, bit to enlarge a well bore in a subterranean formation, wherein crud oil from, the subterranean formation enters the well bore, wherein the crude oil has an API. gravity of about 10 or greater; circulating an aqueous-based drilling fluid past the drill bit, wherein the aqueous-based drillin fluid comprises an aqueous fluid and a cross! inked siyrene-melhacrylate copolymer emulsion in an amount sufficient to prevent eniulsifieatiofi of the crude oil into the aqueous-based drilling fluid; and screening the aqueous-based drilling fluid such that the crude oil is removed from the aqueous-based drilling fluid,

[0009] The features and ad vantages of the present invention will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit, of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS

[0010] The present invention relates to methods and compositions for use in subterranean operations. More particularly, the present invention relates to styreoe-acryiate copolymers used to treat tar and/or crude oil resident in a well bore and associated methods of use.

00 i 1 ] The treatment fluids of the present invention generally comprise an aqueous fluid and a styrene-acrylate copolymer. As used herein, the terra "treatment fluid" refers to any fluid that may be used in a subterranean application in conjunction with a desired function and/or for a desired purpose. The term "treatment fluid" does not imply any particular action by the fluid or any component thereof Treatment fluids may be used, for example, to drill, complete, work over, -fracture, repair, or in any way prepare a well bore for recovery of materials residing a subterranean formation penetrated by the well bore. Examples of treatment fluids include, but are not limited to, cement compositions, drillin fluids, spacer -fluids, and spotting fluids,

[0012] Generally, any siyrene-aerylate copolymer that can be emulsified in an aqueous fluid ma be used. The polymeric material may be ionic o noniomc in nature. In certain embodiments, the styrene-acrylate copolymers may interact with the tar resident in a well bore such that the properties of the lar are altered. In certain embodiments, the polymer may bind or coat the tar such that the tar becomes less sticky, in certain embodiments, the polymer may bind or coat the crude oil such that th crude does not emulsify into the treatment fluid. Thus, the polymer (or polymers when more than one styrene-acrylate copolymer is used) should be added to the well bore in a quantity sufficient to treat the tar and/or crude oil therein, in accordance with embodiments of the present invention.

[0013 J In certain embodiments, the concentration of the styrene-acrylate copolymer in the treatment fluid may be at least about .1 % by volume of the fluid, and up to an amount such that the styrene-acrylate copolymers will precipitate out of the fluid, hi certain embodiments, the concentration of styrene-acrylate copolymer in. the treatment fluid may be in the range of from about 1 % to about 70% by volume of the fluid, in certain embodiments, the concentration of styrene-acrylate copolymer in the treatment fluid may be in the .range for from, about 1 % to about .10% by volume of the fluid, in certain embodiments, the styrene- acrylate copolymer may be added to a treatment fluid, or introduced directly into the well bore, as latex-type emulsions or as dispersed particles, for example, styrene-acrylate copolymer emulsions may be used. In some embodiments, the latex-type emulsions may be crossHnked, One of ordinary skill in the art, with the benefit of this disclosure, will be able to determine the appropriate concentration of the styrene-acrylate copolymer in the fluid for a particular application.

[0014] Examples of styrene-acrylate copolymers that may be suitable for use in the treatment fluids of the present invention m include, but are not limited to, copolymers derived, from styrene and acrylate. In some embodiments, the styrene-acrylate copolymers may include styrene-acrylate copolymers and mixed copolymers which include at least one of styrene, a substituted styrene, and any derivative thereof; and at least one of -acrylate, - methacrylate, -ethyiacry!ate, -propy!acrytate, -butylaerylate, -&?r >utyi-acryia.te, ~n~ hydroxyethyl methacrylate, -potassium acrylate, -pentabromobenzy! acrylate, -methyl methacrylate, -ethyl methacrylate, -n-nitrophenyl acrylate, -methyl 2- (acyloxymethyl)acryiate, -cyciohexyS acrylate, -ti-ethyihexyi acrylate, or any derivative thereof. An example of a suitable styrene-acrylate copolymer comprises a styrene- methacrylate copolymer. Combinations of suitable styrene-acrylate copolymers may also be suitable, in certain embodiments.

[0015] The aqueous fluid utilised in the treatment fluids of the present invention may be fresh water, distilled water, or salt water (e.g., water containing one or more salts dissolved therein). For example, the styrene-acrylate copolymer or polymer emulsion may^¬ be dispersed in the aqueous fluid to form the treatment fluid, in certain embodiments, the treatment fluid may be an aqueous-based fluid. Generally, the water can be from any source, provided that, it docs not contain compounds that undesirably affect other components of the treatment fluid.

[00.16] Optionally* some embodiments may include a surfactant to aid the emulsification and/or suspension of the styrene-acrylate copolymers. Generally, any surfactant that will emulsify and/or suspend the styrene-acrylate copolymers may be used in the fluids of the present invention, in certain embodiments, it. may be desirable to select a surfactant that will not emulsify the tar sought to be treated. In. certain embodiments, the surfactants may be present in an amount sufficient to emulsify and/or suspend the styrene- acrylate copolymers. This amount may depend on, among other things, the type of surfactant used and the amount of polymer to be emulsified and/or suspended. A person of ordinary skill in the art will recognize, with the benefit of this disclosure, the type and amount of surfactant that should be added for a particular application.

[0017] in certain embodiments, the treatment fluids of the present invention may also compri se additional componen ts to enhance, among other things, the performance of the styrene-acrylate copolymers in specific applications. For example, some embodiments may comprise a viseosifier, among other purposes, to aid in suspending the siyrene-acrylate c cooppoollyymmeerrss i inn aa t trreeaattmmeenntt fl fluuiidd,, ssuucchh aass aa d dririlllliinngg f flluuiidd.. S Suuiittaabbllee vviissccoossiiffyyiinngg aaggeennttss mmaayy iinncclluuddee,, bbuutt aarree nnoott lliimmiitteedd ttoo.. ccoollllooiiddaall aaggeennttss ((ee..gg..,, ccllaayyss s suucchh aass b beenntotonniittee,, ppoollyymmeerrss,, gguuaarr gguumm)),, e emniuulissiioonn--lfoorrmmiinngg aaggeennttss,, ddiiaattooramaaeeeeoouuss eeaarrtthh,, b biiooppoollyymmeerrss,, s syynntthheettiicc ppoollyymmeerrss,, cchhii oossaannss,, ssttaarrcchheess,, ggeellaattiinnss,, oorr ..mmiixxttuurreess tthheerreeooff..

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[001 ] In some embodiment, the treatment fluids may be used for the treatment o tar resident in a well bore. One of the many advantages of the present invention, many of which, are not discussed or alluded to herein, is that tar treated by the compositions and methods disclosed herein may be substantially less tack and/or less able to adhere to a surface. As a result, tar treated in this manner ma be susceptible to screen separation from treatment fluids, drill, cuttings, tar sands, and the like,

[0020] Generally, the methods of the present invention comprise allowing a. fluid comprising a styrene-aerylate copolymer to interact with tar resident in a well bore, which may, among other things, reducing the adhesiveness of the tar to facilitate removal of th tar from a well bore or other surface. When the styrene-aerylate copolymer interacts with tar, the styrene may coat or encapsulate the tar such that the tar is less tacky. In applications where it is desirable to drill through tar encountered in the course of drilling a well bore, drilling through tar altered in this way may yield tar-cuttings that can be removed more effectively from the well bore. Additionally, tar that is drilled-through may be less likely to flow into the well bore or the subterranean formation as the plastic properties of the tar may be altered. Similarly, in applications where the styrene-aerylate copolymer is added to a drilling fluid, the treated tar that forms about the surface of the well bore may act to stabilize the well bore. In addition, tar treated with the compositions and methods of the present invention may be separated from a treatment fluid by passing the fluid through a screen or similar separation apparatus.

[0021 ] In one embodiment, ^'the present invention provides a method comprising contacting tar resident in a well bore with a treatment fluid comprising an aqueous fluid and a styrene-aerylate copolymer. In such embodiments, the styrene-aerylate copolymer may be provided in various forms, including, but not limited to* an emulsion, a suspension, a powder, and any combination thereof. In certain embodiments, the treatment fluid may be an aqueous-based fluid. Introducing the styrene-aerylate copolymer to the vicinity of a desired portion of the well bore may be accomplished by a variety of methods known by a person of ordinary skill. In the art with the benefit of this disclosure. One example of such, a method comprises pumping water into the well bore, wherein the styrene- aerylate copolymer is carried into the well bore on the leading edge of the water (e.g., a plug)- In other embodiments of the present invention, the polymer may be pumped into the well bore while suspended in a treatment fluid (e.g., a drilling fluid).

[0022] in certain embodiments, the styrene-aerylate copolymer may be provided as a "spot treatment" or "pill," wherein the polymer is pumped into the well bore to interact with tar in a specific portion of the well bore. In certain embodiments of this type, the styrene- aery fate copolymer may be allowed to interact with the tar resident in the well bore for at least a time sufficient to at least partially reduce the adhesiveness of the tar. ^'In some circumstances, this may be more than about one hour, in others, more time will be required to at least partially reduce the adhesiveness of the tar, depending upon, among other factors, the temperature inside the well bore and the amount of tar in the portion of the well bore being treated. One of ordinary skill in the art, with the benefit of this disclosure, will be able to determine the appropriate amount of time to allow the styrene-aerylate copolymer to interact with the tar. in certain embodiments, after the styrene-aerylate copolymer has been allowed to interact with the tar, the tar then, may be removed from the well bore by any means practicable for the give application. [0023] In some applications, embodiments of the present invention may be used in conjunction with non-aqueous treatment fluids. Embodiments such as a spot treatment or pill may be especially suited for use in conjunction with non-aqueous-based treatment fluids. Where the treatment fluid is non-aqueous based, the treatment fluid may comprise any number of organic liquids. Examples of suitable organic liquids include, but are not limited to. mineral oils, synthetic oils, esters, paraffin oils, diesei oil, and the like.

[0024] in another embodiment, the present invention provides a method, comprising contacting tar resident in a well bore with a treatment fluid comprising an aqueous fluid and a styrene-acrylate copolymer into a well bore and allowing the styrene-acrylate copolymer to interact with tar resident in the well bore to at least partially reduce the tendency of the tar to adhere to a surface. I.n certain embodiments of this type, the styrene-acrylate copolymer may be allowed to interact with the tar as long as the treatment fluid is present In the well bore. One of ordinary skill in the art, with the benefit of this disclosure, will be able to determine the appropriate amount of time to allow the styrene-acrylate copolymer io interact with the tar so as to at least partially reduce the adhesiveness of the tar. In certain embodiments, after the styrene-acrylate copolymer has been allowed to interact with the tar, the tar then may be removed from the well bore by any means racticable for the given application.

[0025] In another embodiment, th present invention provides a method comprising: placing a treatment fluid comprising an aqueous fluid and a styrene-acrylate copolymer into a well bore; and monitoring the amount of the styrene-acrylate copolymer present in the treatment fluid. For example, once a unit of styrene-acr late copolymer in a treatment fluid is allowed, to interact with a unit of tar in a well bore, that unit of styrene-acrylate copolymer may be depleted from the treatment fluid and thus unable to interact with additional tar. For this reason, it may be desirable to monitor the concentration of the styrene-acrylate copolymer in the treatment fluid to determine if more should be added. In some embodiments, the styrene-acrylate copolymer may be introduced into the treatment .fluid before the treatment fluid is introduced into the well bore, for example, a batch-mixing process. In some embodiments, it may be desirable to continue to add the styrene-acrylate copolymer to the treatment fluid (e.g., "on-the-fly" mixing) according to the monitored concentration of the styrene-acrylate copolymer in the treatment fluid. In some embodiments, the concentration of styrene-acrylate copolymer in the treatment fluid may be monitored by direct measurement, tn some embodiments, the concentration of styrene- acrylate copolymer in the treatment fluid may be monitored Indirectly by measuring the depletion of the styrene-acrylate copolymer from the treatment fluid. The concentration of the styrene-aerylate copolymer in the treatment fluid may be monitored, for example, by analytical polymer spectroscopy, chromatography, gravi etry, and quantitative precipitation.

[0026] Another embodiment provides a method of treating tar sands to separate the tar from the sand comprising: contacting the tar sand with a treatment fluid comprising an aqueous fluid and a styrene-aerylate copolymer, the tar sand comprising tar and sand; and allowing the styrene-aerylate copolymer to interact with the lar to at least partially separate the tar from the sand. The term "tar sand" does not require or imply that any specific amount of tar be present.

[0027] Another embodiment provides a method of drilling a well bore comprising: using a drill bit to enlarge a well bore; and circulating a drilling fluid past the drill bit to remove cuttings there from, the drilling fluid comprising an aqueous fluid and a styrene- aerylate copolymer, in certain embodiments, tar may be present within the well bore, and the styrene-aerylate copolymer may be allowed to interact with the lar to at least partially reduce the adhesiveness of the tar, in certain embodiments, after the styrene-aerylate copolymer has been allowed to interact with the tar, the tar then ma be removed from the well bore by any means practicable for the given application.

Example Crude-Oil-Treatment Methods

[0028] in some embodiment, the treatment fluids may be used for the treatment of crude oil in a well bore, it should be understood that the terms "crude oil" and "liquid crude" may be used interchangeably; Crude oil is generally a .naturally occurring liquid that can contain various quantities of paraffins, napthenenes, aroroatks, and/or asphaltenes. The crude oil should be differen.tia.ied from the preceding tar, as the crude oil has an API gravity greater of about 1.0 or greater while the tar has an API specific gravity of less than .10. In some instances, natural gas may be dissolved in the crude oil. Crude oil may be produced from well bores drilled into the Earth's surface. When encountered in the well bore by treatments fluids such as drilling fluids, the crude oil can emulsify into the fluid undesirably effecting fluid properties and causing problems with fluid disposal,

[0029] in accordance with present embodiments, crude oil encountered in a well bore may be treated with styrene-aerylate copolymer. One of the many advantages of the present invention, many of which are not discussed or alluded to herein, is that the crude oil treated by the compositions and methods disclosed herein may not emulsify in the treatment fluids, Rather, the erode oil ma agglomerate to form a tar-like substance thai is substantially less tack.v than tar. As a result, crude oil treated in this manner roav be susceptible to screen separation from treatment fluids, drill cuttings, tar sands, and the like. [0030] Generally, the methods of the present invention comprise allowing a fluid comprising a styrene-aerylate copolymer t interact with erode oil in a well bore, which may, among other things, cause the crude oil to agglomerate to facilitate removal of the crude oil from the fluid and prevent emulsification. When the styrene-acrylate copolymer interacts with crude oil, the styrene may cause the crude oil to agglomerate to form a tar-like substance. Because the styrene-acrylate copolymer should coat or encapsulate the crude oil this agglomerated substance is less tacky than tar. In applications where it is desirable to drill through crude oil encountered in the course of drilling a well bore, drilling through crude oil altered in ibis way may yield agglomerates of the crude oil that can be removed more effectively from the drilling fluid. Additionally, crude oil thai is drilled-through may be less likely to flow into the well bore or the siibteminean formation as the plastic properties of the crude oil may be altered. Similarly, in applications where the styrene-acrylate copolymer is added to a drill ing fluid, the treated crude oil that forms about the surface of the well bore may act to stabilize the well bore. In addition, crude oil treated with the compositions and methods of the present invention may be separated from a treatment fluid by passing the fluid through a screen or similar separation apparatus.

[0031] In one embodiment, the present invention provides, a method comprising contacting crude oil in. a well bore with a treatment fluid comprising an aqueous fluid and a styrene-acrylate copolymer. In such embodiments, the styrene-acrylate copolymer may be provided in various forms, including, but not limited to, an emulsion, a suspension, a powder, and any combination thereof. In certain embodiments, the treatment fluid ma be an aqueous-based fluid. Introducing the styrene-acrylate copoiymer to the vicinity of a desired portion of the well bore may be accomplished by a variety of methods known by a person of ordinary skill in the art with the benefit of this disclosure. One example of such a method comprises pumping water into the well bore, wherein the styrene-acrylate copolymer is carried into the well bore on the leading edge of the water (e.g., a plug). In other embodiments of the present invention, the polymer may be pumped into the well bore while suspended hi a treatment fluid (e.g., a drilling fluid).

[0032] in certain embodiments, the styrene-acrylate copolymer may e provided as a "spot treatment^"" or "pill" wherein the polymer is pumped into the well bore to interact with crude oil in a specific portion of the well bore. In certain embodiments of this type, the styrene-acrylate copolymer may be allowed to interact with the crude oil in the well bore tor at least a time sufficient to at least partially reduce the adhesiveness of the crude oil. in some circumstances, this may be more than about one hour. In others, more time will be required for treatment of the crude oil to reduce its tendency to emulsify in aqueous-based fluids. depending upon, among other factors, the temperature inside the well bore and the amount of crude oil in the portion of the well bore being treated. One of ordinary .skill in the art, with the benefit of this disclosure, will be able to determine the appropriate amount of time to allow the styrene-acrylate copolymer to interact with the crude oil, n certain embodiments, after the styrene-acrylate copolymer has been allowed to interact with the crude oil, the crude oil then may be removed from the well bore by any means practicable for the given application.

[0033] In some applications, embodiments of the present invention may be used in conjunction: with non-aqueous treatment fluids. Embodiments such as a spot treatment or pill may be especially suited for use in conjunction with non-aqueous-based treatment fluids, wherein the pill containing the styrene-acrylate copolymer may be used ahead of and/or behind a non-aqueous drilling fluid, which may comprise an number of organic liquids, including, but are not limited to, mineral oils, synthetic oils, esters, paraffin oils, diesel oil and the like

[0034] in another embodiment, the present invention provides a method comprising contacting crude oil in a well bore with a treatment fluid comprising an aqueous fluid and a styrene-acrylate copolymer into a well bore and allowing the styrene-acrylate copolymer to interact with crude oil in the well bore to cause the crude oil to agglomerate, in certain embodiments of this type, the siyrene-acrylate copolymer ma be allowed to interact with the crude oil as long as the treatment fluid is present in the well bore. One of ordinary skill in the art, with the benefit of this disclosure, will be able to determine the appropriate amount of time to allow the siyrene-acrylate copolymer to interact with the crude oil so as to at least partially reduce the tendency of the crude oil to emulsify. In certain embodiments, after the siyrene-acrylate copolymer has been allowed to interact, with the crude oil, the crude oil then may be removed from the well bore by any means practicable for the given application.

[0035] .In another embodiment, the present invention provides a method comprising; placing a treatment fluid comprising an aqueous fluid and a styrene-acrylate copolymer into a well bore; and monitoring the. amount of the styrene-acrylate copolymer present in the treatment fluid. For example, once a unit of styrene-acrylate copolymer in a treatment fluid is allowed to interact with a unit of crude oil in a well bore, that unit of styrene-acrylate copolymer may be depleted from the treatment fluid and thus unable to interact with additional crude oil. For this reason, it may be desirable to monitor the concentration of the styrene-acrylate copolymer in the treatment fluid to determine if more should be added, in some embodiments, the styrene-acrylate copolymer may be introduced into the treatment fluid before the treatment fluid is introduced into the well bore, .for example, a hatch-mixing process, in some embodiments, it may be desirable to continue to add the styrene-aerylate copolymer to the treatment fluid (e.g., ^won-the-fly" .mixing) according to the monitored concentration of the styrene-aerylate copolymer m the treatment fluid. In some embodiments, the concentration of styrene-aerylate copolymer in the treatment fluid may be monitored by direct measurement. In some embodiments, the concentration of styrene- aerylate copolymer in the treatment fluid may be monitored indirectly by measuring the depletion of the styrene-aerylate copolymer from the treatment fluid. The concentration of the styrene-aerylate copolymer in the treatment fluid may be monitored, for example, by analytical polymer spectroscopy, chromatography, gravimetry, and quantitative precipitation.

[003-6] Another embodiment provides a method of drilling a well bore- comprising: using a drill bit to enlarge- a well bore; and circulating a drilling fluid past the drill bit to remove cuttings there from, the drilling fluid comprising an aqueous fluid and a styrene- aerylate- copolymer. In some embodiments, the drilling fluid may be an aqueous-based drilling fluid, in certain embodiments, crude oil may be present within the well bore, and the styrene-aerylate copolymer may be allowed to interact with the- crude oil such that the such that the crude oil to agglomerates in the drilling fluid, in certain embodiments, after the styrene-aerylate copolymer has been allowed to interact with the crude oil, the crude oil then may be removed from the well bore by any means practicable for the given application. For example, the drilling fluid may be removed from the well bore and screened to remove the crude oil from, the drilling fluid.

[0037] To facilitate a better understanding of the present invention, the following examples of specific embodiments are given. In no way should the following examples be read to limit or define the entire scope of the invention.

EXAMPLE 1

[0038] Certain embodiments of the present invention were tested in an aqueous-base fluid formulated a shown, in Table 1,

Table i : Base Fluid 1

I Fresh Water (ib hbl) j 345.8

Xariihan Gum flb/bbl) 0.701

Starch (Ib/bbl | 4.206

Cellulose flb/bbl) 0.701

Caustic Soda (lb bbJ) 0.05 10039] A non-aqueous-base fluid was a so formulated as shown in Table 2,

[0040] A 50 g sample of tar sand (25% tar by mass) was placed in a first 1/2 lab barrel along with 133.1 g of Base Fluid 1 and a steel test rod. A 12.5 g sample of tar was placed in a second 1/2 lab barrel along with 216.9 g of Base Fluid 2 and a steel test rod. The barrels were then hot rolled for 16 hours at 150 *F (approx. 66.7° C) under 200 psi in a rolling cell, and the test rods were visually inspected for tar accretion. Base Fluid 3 was contaminated with tar sand, and tar was accreted on the test rod. Base Fluid 2 was contaminated w th far, and tar was accreted on the test rod.

.EXAMPLE 2

[0041 ] The two fluid samples were prepared as set forth in Table 3 using the Base Fluid I. described in Table 1. The fluid samples are designate Sample A and Sample B in the table below. The styrene-aerylate copolymers used, in this example were obtained as an emulsion and used as received. Baracor 700^{i> i} corrosion inhibitor is an anti-corrosion additive commercially available from Halliburton Energy Services, Houston, Texas. After ho rolling for 16 hours at 150 °F (approx. 66.7 °C) under 200 psi in a rolling ceil, the mass of the test rod was determined both with any accreted tar and after the accreted tar had been cleaned off. These masses and the mass of the accreted tar for each sample is -reported in Table 3.

contaminated, j not sticky.

EXAMPLE 3

j 0042 j In this example, far was screened from tar-containing fluids. Base fluid I was combined with tar sand and, in two cases, a treatment additive, as illustrated in Table 4 below. The tar-containing fluids were hot roiled then, poured across a vibrating screen material to assess potential screen clogging properties. A screen may be considered fouled if the tar is adhesive and begins to seal/clog the screen openings thereby preventing a fluid from effectively draining. Sample C was a baseline reference of oootreated, adhesive tar and yielded adhesive screen fouling. Sample ϋ was an unsuccessful treatment with a sodium salt that also yielded adhesive screen, fouling. Sample E was a chemical treatmen of tar with styrene-acrylate copolymers that yielded a non-adhesive tar and minimized screen fouling. The styrene-aerylate copolymers used in this example (E) were the same as in the previous tests. Table 4

Sample D E 1

Base Fluid 1(g) ] 149.8 149.8 149.8

Sodium Sa!i (g) 26.25 -

Styrene aerylate - emuiskm(g)

Baracor 700 ^iM Corrosion - 0.75 inhibitor (ml)

Tar Sand (g) 50 50 50

EXAMPLE 4

[0043] Certain embodiments of the present invention were tested in an aqueous-base ^■fluid formulated as shown in Tabie 5.

Table 5: Base Fluid 3 j

Fresh Water (bbl/bbl) 0.976 1

Xanthan Gum (Ib/bbl) 0.5 1

Starch (Ib/bbl) 2.5 !

Caustic Soda (Ib bbl) 0.035 1

Filtration Control Agent (Ib bbl) 1.0 !

Shale Stabilizer (ib bbl) 0.5 j

Corrosion Inhibitor (Ib/bbl) 6 i

[0044] The xanthan gum used was BARAZAN* D PLUS viscosifser, available from Halliburton Energy Services. Inc. The starch used was FILTER-CHECK™ filtration, control agent, available from .Halliburton Energy, inc. The filtration control agent used was PAC™- R nitration control agent available from Halliburton Energy Services, Inc. The shale stabilizer used was EZ-MUD* polymer emulsion available from Bariod Industrial Drilling Products. The corrosion inhibitor used was Baracor 70 ^lM corrosion inhibitor available from Halliburton Energy Services, inc.

[0045] Using Base Fluid 3, three fluid samples were prepared and tested for treatment of crude oil as set forth in Table 6. The fluid samples are designated Sample G, Sample B, and Sample 1 in the table below. Sample I did not include the corrosion inhibitor. The styrene-acrylate copolymer used in this example was obtained as latex emulsion (approx. 45 wi % active) and used as received,. For each test, the crude oil was placed in a lab barrel together with the respective fluid and a steel rod (to mimic drill-string interaction). The system was then, aged by hot rolling for 16 hours at 200 °F (approx. 93.3 °C) under 200 psi of pressure in a rolling cell. The fluid was then allowed cool for 30 minutes and analyzed for emulsifieation of the crude oil into the fluid as well as properties of the crude oil after treatment. A retort analysis was then performed on the fluid to determine the volume percent of crude oil, water, and solids m the fluid, thus giving an indication: of the amount of crude oil emulsified Into the fluid. The retort analysis was performed by pulling the sample from below the flowing crude to analyze the amount of crude oil that ma have been emulsified into the fluid.

[0046] As set forth in the table above, the crude oil treated with the siyrene-acrylate copolymer (Samples G and I I) did not emulsify into the fluid, but rather was found floating on the fluid's surface. However, the crude oil at least partially emulsified into the control (Sample 1) without the styrene-acryiate copolymer. EXAMPLE 5

[0047] Certain embodiments of the present invention were tested in an aqueous-base ^•fluid formulated as shown in Table 7.

[0048] The xanthan gum used was BARAZA *^' D PLUS viseosifier, available from Halliburton Energy Service*, inc. The stareh used was DEXTRID* I...T filtration control agent, available from Halliburton Energy, Inc. The bridging agent used was BARACARB* .25 bridging agent, available from Halliburton Energy Services, Inc. The simulated drill solids used were REV DUST^¾" solids, available from Milwhite, inc. The corrosion inhibitor used was Baracor 700 ** corrosion inhibitor available from Halliburton Energy Sen-ices. inc.

[0049] Using Base Fluid 4, three fluid samples were prepared and tested for treatment of crude oil as set forth in Table 8. The fluid samples are designated Sample J, Sample K. and Sample L in the {able below. Sample I..· did not include the corrosion inhibitor. Th styreoe-acrylate copolymer used in this example was obtained as latex emulsion (approx. 45 wt. % active) and used as received. For each test, the crude oil was placed in a lab barrel together with the respective fluid and a steel rod (to mimic drill-string interaction). The system was then aged by hoi roiling for 16 hours at 200 °F (approx. 93.3 X) under 200 psi of pressure in a rolling cell, The fluid was then allowed cool for 30 minutes and analyzed for emulsif cation of the crude oil into the fluid as well as properties of the crude oi l after treatment. A retort analysis was then performed on the fluid to determine the volume percent of crude oil, water, and solids in the fluid, thus giving an indication of the amount of crude oil emulsified into the fluid. The retort analysis was performed by pullin the sample from below the flowing crude to analyze the amount of erode oil t hat may have been emulsified into the fluid. Table 8

Sample J K L

Base Fluid 4 (ml) 120 120 120

Crude Oil, ih bbl 25 25 25

Styrene-Acrylate Copolymer 30 10 0

Eraukion(lb/bbI)

Hot Roll at 200 °P (Sir) 16 1 16

Mo crude oil was Some crude oil Some crude oil was stack to the bar. was stuck to the stuck to the bar. The The crude oil was bar. The crude crude oil was very found as a tar-like oil was very runny and sticky. substance floating runny and sticky. The crude oil was on the surface of The crude oil was found as a tar-like the fluid. The found as a tar- like substance floating fluid was not substance floating on the surface of the

Observations

contaminated and on the surface of fluid as a sticky looked very clean. the fluid as a layer. The fluid was sticky layer. The heavily

fluid was slightly contaminated.

more

contaminated, but

not badly

contaminated.

Retort Analysis 0% : 98%; 2 % 0% : 98% : 2% 1% : 96% : 3%

(oil% ; water% : solid )

[0050] As set forth in the table above, the crude oil treated with the styrene-aerySate copolymer (Samples J and K) did not emulsify into the fluid but was rather floating on the fluid's surface- However, the crude oil at least partially emulsified into the control (Sample L) without the styrene-acrylate copolymer.

[0051 ] For the sake of brevity, only certain ranges are explicitly disclosed herein, However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitl recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited- Additionally, whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, ever range of values (of the form, "from about a to about b," or, equivalenily, "from approximatel a to b,^*' or, eqinvaleutly, "from approximately a-b") disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited. Thus, every point or Individual value may serve as sis own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0052] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as. well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention, may be modified and practiced i different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Although individual embodiments are discussed, the invention covers all combinations of all those embodiments, Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. Also, the terms in the claims have their plain, ordinar meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles "a" or "an," as used in the claims, are defined herein to mean one or more than one of the element that it introduces. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.

Claims

What is claimed is:

1. A method of preventing emulsification of crude oil into an aqueous- based treatment fluid, comprising:

contacting crude oil in a well bore with the aqueous-based treatment fluid comprising a styrene-aerylate copolymer, wherein the crude oil has an API gravity of about 10 or greater; and

allowing the styrene-aerylate copolymer to interact with the crude oil in the well bore.

2. The method of claim 1 wherein interaction of the styrene-aerylate copolymer reduces and/or prevents emiilsification of the crude oil in the aqueous-based treatment Ouid, the method farther comprising screening the crude oil from the aqueous-based treatment fluid.

3. ^'The method of claim I further comprising monitoring the amount of the styrene-aerylate copolymer present in the aqueous-based treatment fluid; and adding additional styrene-aerylate copolymer to the aqueous-based treatment fluid in response to the step of monitoring.

4. The method of claim 1 wherein the aqueous-based treatment fluid is placed in the well bore to inieraci with crude oil present at a speeifie location therein,

5. The method of claim 1 wherein the aqueous-based treatment fluid, is placed into the well bore during drilling of the well bore,

6. The method of claim 1 wherein the styrene-aerylate copolyme comprises: at least one unit selected from the group consisting of a styrene, a substituted styrene, and an derivative thereof; and

at least one unit selected from the group consisting of -acrylate, - methaery!ate, -ethylacryiate, -propylacrylate, -bufy!acrylate, -tert-hutyl-aerylate, -n- hydroxyethyl- metlracrylate, -potassium acrylate, -pentabromobenzyl acrylate, -methyl methacrytate, -ethyl msthacrylate, -n-nitropheny! acrylate, -methyl 2- (aeyloxymethyl)acryiate, -cyelohexyl acrylate, ~n~ethylhexyi acrylate, and any derivative thereof.

7. The method of claim 1 wherein the styrene-aerylate copolymer comprises a styrene-methaerylate copolymer.

8. The method of claim 1 wherein the styrene-aerylate copolymer comprises a crossHnked styrene-aerylate copolymer emulsion.

9. The method of claim 1 wherein the styrene-aerylate copolymer is derived from monomers consisting of one or more styrene monomers and one or more acrylate monomers-

10. The method of claim 1 wherein the styrene-acrylate copolymer is present in an amount of about 1 % to about 10% by volume of the aqueous-based treatment fluid,

1 1. The method of claim 1 wherein the aqueous-based treatment fluid further comprises a surfactant.

12. A method of treating crude oil, comprising:

using a drill bit to enlarge a well bore in a subterranean formation, wherein crude oil from the subterranean formation enters the well bore, wherein the crude oil has an API gravity of about 10 or greater; and

circulating an aqueous-based drilling fluid past the drill bit, the aqueous- based drilling fluid comprising an aqueous fluid and a styrene-acrylate copolymer, wherein the styrene-acrylat copolymer interacts with the crude oil in the well bore such that the crude oil forms agglomerates in the aqueous-based drilling fluid.

13. ^'The method of claim 12 further comprising screening the agglomerates of crude oil from the aqueous- based drilling fluid.

14. The method of claim 2 wherein the styrene-acrylate copolymer comprises: at least one unit selected from the group consisting of a styrene, a substituted styrene, and an derivative thereof; and

at least one unit selected from the group consisting of -acrylate, - methaeryiate, -ethylacryiate, -propylacrylate, -butylaerylate, -tert-hutyl-aerylate, -n- hydr xyethyl methacrylate,, -potassium acrylate, -pentabroraobenzyl acrylate, -methyl methacrylate, -ethyl methacrylate, -n-nitrophenyl acrylate, -methyl 2~ (aeyioxymethyl)acryiate, -cyclohexyl aerylate, -n-efhylhexyi acrylate, and any derivative thereof.

15. The method of claim 12 wherein the styrene-acrylate copolymer comprises a styrene-methaerylate copolymer.

16. The method of claim 12 wherein the styrene-acrylate copolymer is derived from monomers consisting of one or more styrene monomers and one or more acrylate monomers.

17. The method of claim 12 wherein the styrene-acrylate copolymer is present in an amount of about 1% to about 10% by volume of the aqueous-based dri lling fluid.

18. A method of treating crude oil, comprising;

using a drill bit to enlarge a well bore in a subterranean formation, wherein crude oil from the subterranean formation enters the well bore., wherein the crude oil has an API gravity of about 10 or greater;

circulating an aqueous-based drilling fluid past the drill bit, wherein the aqueous-based drilling fluid comprises an aqueous fluid and a crossiinked styrene- methacryiiiie copolymer emulsion in an amount sufficient to prevent emuisiilcation of the crude oil into the aqueous-based drilling fluid; and

screening the aqueous-based drilling fluid such that the crude oil is removed from the aqueous-based drilling fluid.

19. The method of claim 18 wherein the crosslinked styrene-meihacrylate copolymer emulsion is derived from monomers consisting of one or more styrene monomers and one or more mefhacrylate monomers.

20. The method of claim 18 wherein the crosslinked styrene-meihacrylate copolymer emulsion is present in an amount of about 1% to about 10% by volum of the aqueous-based drilling fluid.

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