Titanium dioxide nanofluid composition and method of preparation thereof for enhanced thermal and rheological stability

Abstract

ABSTRACT TITANIUM DIOXIDE NANOFLUID COMPOSITION AND METHOD OF PREPARATION THEREOF FOR ENHANCED THERMAL AND RHEOLOGICAL STABILITY The present invention relates to a titanium dioxide (TiO₂) nanofluid composition and a method for its preparation, offering enhanced dispersion stability, thermal resistance, and rheological behavior. The nanofluid comprises an aqueous base fluid containing at least one oilfield polymer selected from xanthan gum and partially hydrolyzed polyacrylamide (HPAM), a cationic surfactant such as cetyltrimethylammonium bromide (CTAB) at a concentration of 0.3645 gm / L, and uniformly dispersed TiO₂ nanoparticles having a particle size in the range of 20 to 200 nanometers and a zeta potential greater than –30 millivolts. The method involves in situ synthesis of TiO₂ nanoparticles by hydrolysis of tetrabutyl orthotitanate (TBOT) in the polymer-surfactant matrix under alkaline conditions. The composition demonstrates high colloidal stability, viscosity retention at elevated temperatures, and is

Description

FIELD OF INVENTION

[0001] Embodiment of the present invention relates to titanium dioxide (TiO2)nanofluid composition and method of preparation thereof for enhanced thermal andrheological stability. More particularly, the present invention pertains to a stablecolloidal dispersion of TiO2 nanoparticles synthesized in situ by a direct methodwithin an aqueous base fluid comprising oilfield-compatible polymers and acationic surfactant, intended for use in drilling fluid systems to improve thermalconductivity, lubricity, and viscosity, while reducing reliance on environmentallyhazardous additives.BACKGROUND

[0002] In oil and gas production, drilling fluid plays a pivotal role in cooling andlubricating the drill bit, carrying drill cuttings to the surface, maintaininghydrostatic pressure, and stabilizing the wellbore. However, conventional drillingfluids face several limitations in high-temperature, high-pressure (HTHP)environments, including poor thermal conductivity, reduced viscosity, andinsufficient lubricity. To address these challenges, nanotechnology has emerged asa promising avenue to enhance the performance of drilling fluids through theincorporation of nanomaterials such as metal oxides, including titanium dioxide(TiO2).

[0003] Nanofluids are engineered colloidal dispersions consisting of nanoparticlessuspended in a base fluid, such as water, oil, or polymer solutions. These fluidsexhibit superior thermal conductivity, tunable viscosity, and improved stability dueto their large surface area-to-volume ratio and unique quantum effects at thenanoscale (Chakraborty et. al., 2020). Among various nanomaterials, titaniumdioxide (TiO2) nanoparticles are particularly attractive due to their high thermalconductivity, chemical stability, and biocompatibility. Their integration intodrilling fluids can lead to enhanced heat dissipation, better lubricity, and improvedcuttings suspension, thereby significantly reducing equipment wear and operationalcosts.

[0004] Despite the known advantages of nanofluids in drilling operations, thereremains a need for a robust, scalable, and cost-efficient method to synthesize stableTiO2 nanofluids with controlled particle size and enhanced performancecharacteristics.

[0005] Therefore, there is a need to address the challenges of the existing nanofluidsby providing a direct method for preparing TiO2 nanofluids in environmentallyfriendly polymeric base fluids, offering improved stability, thermal conductivity,and rheological control for use in oilfield applications.SUMMARY

[0006] The present invention relates to a titanium dioxide (TiO2) nanofluidcomposition and a method for its preparation, particularly suitable for applicationin drilling fluids used in oil and gas production. The present invention addresses thetechnical limitations associated with conventional drilling fluid additives, such aspoor thermal conductivity, instability, and inadequate lubricity, by providing astable, size-controlled nanofluid synthesized via a direct method.

[0007] In accordance with an embodiment of the present invention, a titaniumdioxide (TiO2) nanofluid composition is provided. The titanium dioxide (TiO2)nanofluid composition comprises an aqueous base fluid comprising an aqueoussolution of at least one oilfield polymer, a pH-adjusting agent, a colloidal dispersionof titanium dioxide (TiO2) nanoparticles in the aqueous base fluid, and a cationicsurfactant (Cetyltrimethylammonium bromide (CTAB)) at critical micelleconcentration (CMC) of 0.3645 gm / L. The titanium dioxide (TiO2) nanofluids havea particle size in a range of 20 to nanometers (nm) and a zeta potential greater than-30 millivolts (mV) which went upto - 65 mV, and are uniformly dispersed in theaqueous base fluid.

[0008] In another embodiment of the present invention, a method for preparing atitanium dioxide (TiO2) nanofluid composition is provided. The method comprisessteps of preparing an aqueous base fluid by dissolving at least one oilfield polymerselected from xanthan gum and partially hydrolyzed polyacrylamide (HPAM) indeionized water at a concentration of 500 ppm to 2000 ppm. The aqueous base fluidpH is adjusted to a value in a range of 9 to 10 using ammonium hydroxide.Tetrabutyl orthotitanate (TBOT) is mixed with ethanol to obtain a precursor mixturefollowed by adding the precursor mixture dropwise into the aqueous base fluidunder continuous stirring to induce hydrolysis to obtain titanium dioxidenanoparticles in situ. A cationic surfactant comprising cetyltrimethylammoniumbromide (CTAB) is added to the mixture at a concentration of 0.3645 gm / L.Continuously stirring the mixture for a duration sufficient to obtain a uniformcolloidal dispersion of the titanium dioxide nanoparticles providing the titaniumdioxide (TiO2) nanofluid composition having a particle size in the range of 20 to200 nm and a zeta potential greater than - 30 mV.

[0009] The present invention provides the TiO2 nanofluid that exhibits enhancedthermal stability, rheological behavior, and lubricity under elevated temperatureconditions, making it highly suitable for use in drilling and completion operations.The present invention further contributes to environmental sustainability byutilizing biodegradable and non-toxic polymeric base fluids in place of traditionalhazardous additives.

[0010] To further clarify the advantages and features of the present invention, amore particular description of the invention will follow by reference to specificembodiments thereof, which are illustrated in the appended figures. It is to beappreciated that these figures depict only typical embodiments of the invention andare therefore not to be considered limiting in scope. The invention will be describedand explained with additional specificity and detail with the appended figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The disclosure will be described and explained with additional specificityand detail with the accompanying figures in which:

[0012] FIG. 1 depicts a flow chart representation of a method for preparing atitanium dioxide (TiO2) nanofluid composition, in accordance with an embodimentof the present disclosure;

[0013] FIG. 2 depicts: 2a) conventional method of preparing nanofluid by mixingand sonicating commercially purchased nanoparticles in the base fluid, 2b)preparation of nanofluid by Direct method in the base fluid, in accordance with anembodiment of the present disclosure;

[0014] FIG. 3 depicts schematic to exhibit agglomeration in conventional nanofluid(Prior Art) and uniform dispersion in nanofluid of the present invention preparedby direct method, in accordance with an embodiment of the present disclosure;

[0015] FIG. 4 depicts drill cuttings around drill bit and settled at the bottom of thehole leading to increase in friction and wear of drill bit, thick mud cake formed dueto inadequate removal of cuttings and debris, drill bit damaged due to hightemperature and friction generated because of lack of lubricity in the drilling fluid,in accordance with an embodiment of the present disclosure.

[0016] FIG. 5 depicts schematic to show synthesis of TiO2 nanofluid, in accordancewith an embodiment of the present disclosure;

[0017] FIG. 6 depicts schematic to exhibit steric stabilization in nanofluid wherethe polymer chains and CTAB interact to keep the nanoparticles without anyagglomeration, in accordance with an embodiment of the present disclosure;

[0018] FIG. 7 depicts drilling fluid with modified viscosity efficiently removing thecuttings from which in turn reduces the drag on drill stem, in accordance with anembodiment of the present disclosure; and

[0019] FIG. 8 depicts drilling fluid with proper lubrication increases drill bitperformance and life, in accordance with an embodiment of the present disclosure.

[0020] Further, those skilled in the art will appreciate that elements in the figuresare illustrated for simplicity and may not have necessarily been drawn to scale.Furthermore, in terms of the construction of the device, one or more components ofthe device may have been represented in the figures by conventional symbols, andthe figures may show only those specific details that are pertinent to understandingthe embodiments of the present disclosure so as not to obscure the figures withdetails that will be readily apparent to those skilled in the art having the benefit ofthe description herein.DETAILED DESCRIPTION

[0021] For the purpose of promoting an understanding of the principles of thedisclosure, reference will now be made to the embodiment illustrated in the figures,and specific language will be used to describe them. It will nevertheless beunderstood that no limitation of the scope of the disclosure is thereby intended.Such alterations, further modifications in the illustrated online platform, and furtherapplications of the principles of the disclosure as would normally occur to thoseskilled in the art are to be construed as being within the scope of the presentdisclosure.

[0022] The terms "comprises", "comprising", or any other variations thereof, areintended to cover a non-exclusive inclusion, such that a process or method thatcomprises a list of steps does not include only those steps but may include othersteps not expressly listed or inherent to such a process or method. Similarly, one ormore devices or subsystems or elements or structures or components preceded by"comprises... a" does not, without more constraints, preclude the existence of otherdevices, subsystems, elements, structures, components, additional devices,additional subsystems, additional elements, additional structures or additionalcomponents. Appearances of the phrase "in an embodiment", "in anotherembodiment" and similar language throughout this specification may, but notnecessarily do, all refer to the same embodiment.

[0023] Unless otherwise defined, all technical and scientific terms used herein havethe same meaning as commonly understood by those skilled in the art to which thisdisclosure belongs. The system, methods, and examples provided herein are onlyillustrative and not intended to be limiting.

[0024] In the following specification and the claims, reference will be made to anumber of terms, which shall be defined to have the following meanings. Thesingular forms "a", "an", and "the" include plural references unless the contextclearly dictates otherwise.

[0025] FIG. 1 depicts a flow chart representation of a method for preparing atitanium dioxide (TiO2) nanofluid composition, in accordance with an embodimentof the present disclosure.

[0026] Embodiments of the present invention relates to a titanium dioxide (TiO2)nanofluid composition and a method for its preparation. More specifically, theinvention discloses a stable colloidal dispersion of TiO2 nanoparticles in an aqueousoilfield polymer-surfactant matrix with enhanced thermal stability and rheologicalproperties, and a direct in-situ synthesis method for the same.

[0027] In accordance with an embodiment of the present invention, a titaniumdioxide (TiO2) nanofluid composition is provided. The titanium dioxide (TiO2)nanofluid composition comprises an aqueous base fluid comprising an aqueoussolution of at least one oilfield polymer, a pH-adjusting agent, a colloidal dispersionof titanium dioxide (TiO2) nanoparticles in the aqueous base fluid, and a cationicsurfactant at a critical micelle concentration (CMC) of 0.3645 g / L. The titaniumdioxide (TiO2) nanofluids have a particle size in a range of 20 to 200 nm and havezeta potential values greater than - 30 millivolts (mV) which went up to - 65 mV,and are uniformly dispersed in the aqueous base fluid.

[0028] In an exemplary embodiment of the present invention, the oilfield polymeris selected from xanthan gum, partially hydrolyzed polyacrylamide (HPAM), guargum and polyacrylamide (PAM). The cationic surfactant iscetyltrimethylammonium bromide (CTAB). The concentration of the titaniumdioxide nanoparticles is in the range of 0.5 wt.% to 2 wt.%. The concentration ofthe oilfield polymer in the aqueous base fluid is in the range of 500 ppm to 2000ppm. The pH-adjusting agent comprises ammonium hydroxide in a concentrationsufficient to maintain pH between 9 and 10. The TiO2 nanofluid composition retainsdispersion stability and viscosity at a temperature of 80 °C to 100 °C. The TiO2nanofluid composition exhibits a viscosity of 3 to 100 cP at varying shear rate from1000 to 1 s-1 at 25 °C. TiO2 nanofluids exhibit shear thinning behaviour, which isdecrease in viscosity with increase in shear rate.

[0029] In another embodiment of the present invention, a method for preparing atitanium dioxide (TiO2) nanofluid composition is provided. The method comprisessteps of preparing an aqueous base fluid by dissolving at least one oilfield polymerselected from xanthan gum and partially hydrolyzed polyacrylamide (HPAM) indeionized water at a concentration of 500 ppm to 2000 ppm, at step 102. Theaqueous base fluid pH is adjusted to a value in a range of 9 to 10 using ammoniumhydroxide, at step 104. Tetrabutyl orthotitanate (TBOT) is mixed with ethanol toobtain a precursor mixture followed by adding the precursor mixture dropwise intothe aqueous base fluid under continuous stirring to induce hydrolysis to obtaintitanium dioxide nanoparticles in situ, at step 106. A cationic surfactant comprisingcetyltrimethylammonium bromide (CTAB) is added to the mixture at CMC, whichis 0.3645 gm / L, at step 108. Continuously stirring the mixture for a durationsufficient to obtain a uniform colloidal dispersion of the titanium dioxidenanoparticles providing the titanium dioxide (TiO2) nanofluid composition havinga particle size in the range of 20 to 200 nanometers and zeta potential varied from -30 millivolts to -65 millivolts, at step 110.

[0030] In another exemplary embodiment of the present invention, the concentrationof the TBOT is selected to yield a titanium dioxide nanoparticle concentration inthe range of 0.5 wt.% to 2 wt.% in the titanium dioxide (TiO2) nanofluidcomposition. The ethanol is added at a volume ratio of 3:1 to 4.35:1 of TBOT. Thecationic surfactant comprising cetyltrimethylammonium bromide (CTAB) is addedat critical micelle concentration (CMC). The titanium dioxide (TiO2) nanofluidcomposition is characterized by a stable colloidal dispersion with no visiblesedimentation after 30 days of storage at room temperature.

[0031] The present invention is explained further in the following specific examples,which are only by way of illustration and are not to be construed as limiting thescope of the invention.Examples

[0032] FIG. 2 depicts: 2a) conventional method of preparing nanofluid by mixingand sonicating commercially purchased nanoparticles in the base fluid, 2b)preparation of nanofluid by Direct method in the base fluid, in accordance with anembodiment of the present disclosure.

[0033] Synthesis of cost efficient TiO2 nanofluid by Direct method.Nanofluids are stable colloidal suspensions in which nanoparticles (titaniumdioxide) are dispersed in a base fluid. Any fluid, including water, oil, polymersolution, etc., can serve as the base fluid. Nanofluids can be prepared by eitherdispersing commercially available nanoparticles in the base fluid (conventionalnanofluid) as shown in FIG. 2a or synthesizing and simultaneously dispersing themin the base fluid (Direct method) (FIG. 2b). Nanofluids prepared by direct methodhave better stability and better control over size and shape as compared toconventional nanofluid. There is no agglomeration in these nanofluids and any sizeof nanofluids can be prepared by direct method. These nanofluids are customizablein terms of shape, size and concentration to meet the demands of highlyunpredictable downhole conditions. Due to their improved mechanical, rheological,and thermal characteristics, they provide special advantages over conventionalnanofluids when added to drilling and spacer fluids. Here TiO2 nanofluid ofdifferent sizes and concentrations were synthesized and its efficacy on drilling fluidwere explored. TiO2 nanofluid was synthesized by direct method wherenanoparticles were in-situ synthesized and dispersed in the base fluid. The basefluid chosen was oil field polymers, which are already being used in oilfieldoperations, such as xanthan gum and partially hydrolyzed polyacrylamide. Thesepolymers are environment friendly and biodegradable. The sizes of nanofluid werevaried from 20 - 200 nm, and concentration was 0.5 - 2 wt.%. The additives whichare being used in drilling and completion operations are not as efficient and arecostly. The purpose of synthesizing the nanofluids was to make efficient as well ascost effective nanomaterials for different oilfield applications.

[0034] FIG. 3 depicts schematic to exhibit agglomeration in conventional nanofluidand uniform dispersion in nanofluid of the present invention prepared by directmethod, in accordance with an embodiment of the present disclosure.

[0035] Nanofluids can be prepared by either one step or two step method.Nanofluids are conventionally prepared by incorporating and dispersingcommercially available nanoparticles in a base fluid through various mechanicaltechniques (two step method), including sonication, vigorous stirring, and mixing(Chakraborty et. al., 2020). The drawback of the conventional nanofluids is thatthey agglomerate and form large clusters as depicted in FIG. 3 (Chakraborty et.al., 2017). Also, the size of nanofluids cannot be controlled in two step nanofluids.Direct method (DM) of synthesis is similar to synthesis by one step method wherenanoparticles are in-situ synthesized and simultaneously dispersed in the base fluid.Direct method of synthesis of TiO2 nanofluid does not require vigorous mechanicalagitation such as mixing, sonication, etc., only stirring is needed to synthesizenanofluid. The advantage of synthesis by DM is that nanoparticles size andconcentration can be controlled. The size of the synthesized nanofluid was 20 - 50nm, 70 - 100 nm, 120 - 200 nm, and concentrations were 0.5, 1 and 2 wt.%. Thestability of these nanofluids were also greater as compared to two step nanofluid,which is reflected by higher zeta potential values (greater than -30 mV). Moreover,TiO2 nanofluids improve lubricity by acting as nano-sized ball bearings that reducefriction between the drill bit and cuttings, thereby enhancing the rate of penetration(ROP) and extending the operational lifespan of drilling tools.

[0036] FIG. 4 depicts drill cuttings around drill bit and settled at the bottom of thehole leading to increase in friction and wear of drill bit, thick mud cake formed dueto inadequate removal of cuttings and debris, drill bit damaged due to hightemperature and friction generated because of lack of lubricity in the drilling fluid,in accordance with an embodiment of the present disclosure.

[0037] During drilling operations, intense friction and mechanical activity generatesubstantial heat at the drill bit, often leading to degradation of the bit and thesurrounding drilling fluid (FIG. 4). The integration of TiO2 nanoparticles, owing totheir superior thermal conductivity, facilitates rapid heat dissipation and reducesthermal damage to drilling equipment (Farahbod et. al., 2021). Due to hightemperature the drill bit gets damaged (FIG. 4), and lack of proper lubricity furtherintensifies the damage on drill bit. The wearing of drill bit slows the rate ofpenetration (ROP), which further increases the overall cost of the drillingoperations. Nanofluids contain nanoparticles which adhere to the surface of the drillbit and act as small bearing which minimizes the friction between drill bit andcuttings. Thus, nanofluid treated drilling fluid prevents drill bit wear by dissipatingheat and by reducing friction. The lubricity of the drilling fluid is also increasedwith the addition of the nanofluids as also reported by (Ismail et. al., 2016).Therefore, nanofluid treated drilling fluid have better lubricity capacity.

[0038] The addition of nanoparticles modifies the viscosity and flow characteristicsof drilling fluids. This helps in efficiently transporting drill cuttings to the surface,ensuring the fluid remains stable under varying shear conditions, and preventingissues like pipe sticking or inefficient cuttings removal (FIG. 4). Optimal viscosityis required for the transportation of the cuttings to the surface as less viscous drillingfluid is unable to suspend and transport the cuttings (Al-Shargabi et. al., 2022;Ismail et. al., 2016). This leads to filter cake formation, fluid loss, loss of circulationand pipe sticking problems. Therefore, viscosity is one of the important parametersthat is to be addressed for proper disposal of cuttings and prevent pipe stuckproblems. With addition of nanofluid in the drilling fluid it increases the viscositywhich provides suspension of cuttings for a longer time, which helps in completeremoval of cuttings from the borehole. Higher viscosity also reduces fluid loss andforms optimal filter cake, this in turn reduce the formation damage from the drillingfluids (Gokdemir et. al., 2017). Therefore, with optimal viscosity the drillingoperations cost is minimized as it addresses other problems. This optimization ofviscosity not only reduces the risk of operational failure but also contributes to cost effective drilling by minimizing non-productive time (NPT).

[0039] FIG. 5 depicts schematic to show synthesis of TiO2 nanofluid, in accordancewith an embodiment of the present disclosure.

[0040] Size controlled synthesis of TiO2 nanofluid by Direct methodTiO2 nanofluid was synthesized by direct method with oil field polymers (xanthangum and HPAM) as base fluid. The concentration of polymer (xanthan gum andHPAM) was varied from 500 - 2000 ppm for nanofluid. The size of nanofluidswere varied as 20 - 50 nm, 70 - 100 nm, 120 - 200 nm and concentration were 0.5,1 and 2 wt. %. The schematic for synthesis of TiO2 is depicted in FIG. 5. Forsynthesis of 100 ml of 1wt.% TiO2 nanofluid firstly, polymer solution was preparedby mixing 1 gm polymer (HPAM / XG) in 1000 ml DI water, which takes around5 - 6 hours. Then 70 ml PAM was taken in a beaker and 5 ml of 25% ammoniumhydroxide (NH4OH) was added dropwise to raise the pH upto 9 - 10. In separatebeaker 20 ml ethanol was taken and stirred at 1000 rpm, then 4.6 ml of tetrabutylorthotitanate (TBOT) was added dropwise in ethanol which was stirred for 20minutes. This mixture of TBOT and ethanol was added dropwise into the polymerat a stirring rate of 1000 rpm. Within 30 minutes a milky white appearance isobserved which indicate formation of TiO2 nanoparticles. Then 36.45 mgCetyltrimethylammonium bromide (CTAB) was added in the suspension whichprovides steric stabilization (see Figure 5) to the nanofluid. The concentration ofCTAB was kept at its CMC which is 0.3645 gm / L. The stirring was continued foranother 2 hours, then its size and zeta potential values were recorded. The zetapotential of all the nanofluids were greater than - 30 mV, which indicates thatnanofluid is stable.

[0041] Environmentally friendly and biodegradable base fluidOil well drilling is a complex operation which involves drilling a well (hole) in theEarth's subsurface to extract oil and gas. Drilling fluid serves as coolant andlubricant to drill bit, carries the cuttings to surface, maintains wellbore pressure andstabilizes the wellbore. Drilling fluid can be water based as well as oil based, andthey contain various additives to achieve the required parameter. These additivessuch as lignosulfonates, surfactants, polymers and synthetic additives etc., can havesignificant environmental hazards. Therefore, to mitigate environmentaldegradation organic and biodegradable polymers are used such as, xanthan gum andHPAM as base fluid to synthesize and disperse TiO2 nanofluids. However, guargum and PAM which are readily used in oilfield can also be used as base fluid.These polymers offer wide range of operations and can be used based on thedifferent zones. In water bearing zones xanthan gum and guar gum can be used asbase fluid as these are biodegradable and non-toxic. PAM and HPAM are non-toxicin polymer form but may contain residual acrylamide monomer.

[0042] FIG. 6 depicts schematic to exhibit steric stabilization in nanofluid wherethe polymer chains and CTAB interact to keep the nanoparticles without anyagglomeration, in accordance with an embodiment of the present disclosure.

[0043] Steric stabilization by combining polymer (xanthan gum) and surfactant(CTAB)CTAB surfactant tend to stabilize nanofluid by providing electrostatic and stericstabilization (Chakraborty et. al., 2020; Kusrini et. al., 2019), while alsocontrolling the particle morphology (FIG. 6). Steric stabilization occurs whenpolymer chains, surfactant, or other stabilizing molecules adsorb onto the surfaceof nanoparticles, creating a physical barrier that prevents them from coming tooclose which is a sign of higher dispersion stability. Polymer chain alone cannotprovide steric stabilization as exhibited in FIG. 6 indicating agglomeration. CTAB(at lower concentrations) with xanthan gum was found to be the most stable systemwhich reflected in higher zeta potential values.

[0044] FIG. 7 depicts drilling fluid with modified viscosity efficiently removing thecuttings from which in turn reduces the drag on drill stem, in accordance with anembodiment of the present disclosure.

[0045] Viscosity alteration by incorporation of TiO2 nanofluid in Drilling fluidViscosity of drilling fluid is one of the most important parameters which affects itsperformance. TiO2 nanofluid can modify the viscosity of drilling fluid as nanosizedparticles interact with polymer which in turn provides stability. Due to modifiedviscosity suspension of cuttings is improved. TiO2 nanofluid enhances heat transferand stabilizes drilling fluid properties at high temperatures (FIG. 7). Nanoparticlesin nanofluid reduce friction between drill string and wellbore which reduces torqueand drag on the drill stem.

[0046] FIG. 8 depicts drilling fluid with proper lubrication increases drill bitperformance and life, in accordance with an embodiment of the present disclosure.

[0047] Heat dissipation and lubricityDuring drilling wellbore huge amount of heat is generated because of friction whichmay impair the drilling fluid's viscosity. Drill bits also tend to get damaged due tocontinues heat generation and friction. Nanofluids can reduce the friction betweenthe drill bit and the wellbore wall. This is important when drilling in challengingconditions, as it helps maintain optimal circulation and reduces fluid loss.Nanofluids can also improve heat dissipation and cooling during drilling operations,which can indirectly help to maintain the integrity of the formation, reducing thechance of formation damage or excessive fluid loss due to temperature effects.Nanoparticles act as tiny ball bearings that reduce friction between the drill bit andcuttings. This improved lubrication minimizes wear on drilling equipment and canreduce the overall energy required to rotate and advance the drill bit. The rate ofpenetration (ROP) of the drill bit is also increased by improved lubricity betweendrill bit and drilling fluid. Thus, by incorporating nanofluid in the drilling fluid willimprove the lubricity and heat dissipation capacity of the drilling fluid. TiO2nanofluid possess high heat conductivity, which will efficiently cool the drill bitand protect it from wear. Thus, nanofluid treated drilling fluid improves thelubricity and increase the heat dissipation of the drilling fluid, which will reducethe overall time and cost of drilling operations (FIG. 8).

[0048] The titanium dioxide (TiO2) nanofluid prepared by the direct, in-situsynthesis method described in the present invention offers several distinctadvantages over conventional nanofluids including the direct method results in ahighly stable colloidal dispersion with uniform particle size distribution and higherzeta potential, leading to enhanced performance and long-term stability withoutagglomeration. The TiO2 nanofluid eliminates the need for several toxic orhazardous chemical additives typically used in traditional drilling fluids, therebymaking the formulation more environmentally benign and safer for oilfieldoperations. Additionally, TiO2 nanofluid exhibits excellent thermal stability andretains its rheological properties under high-temperature conditions commonlyencountered in deep well drilling. This thermal resilience ensures consistentperformance, minimizes fluid loss, and helps protect drilling equipment, ultimatelycontributing to improved efficiency and reduced operational costs.

[0049] The present invention successfully demonstrates the synthesis of a cost effective, thermally stable, and rheologically optimized titanium dioxide (TiO2)nanofluid using a direct in-situ method. Unlike conventional two-step nanofluidformulations that rely on pre-synthesized nanoparticles and mechanical dispersiontechniques, the method disclosed herein allows for simultaneous synthesis andstabilization of TiO2 nanoparticles directly within the aqueous polymeric base fluid.This approach eliminates the common issues of agglomeration and sedimentationand provides precise control over nanoparticle size (ranging from 20 to 200 nm)and concentration (0.5-2 wt.%). The resulting nanofluid displays high zeta potentialvalues (greater than -30 mV), indicating excellent colloidal stability without theneed for harsh dispersive processing.

[0050] Furthermore, the combination of biodegradable oilfield polymers-such asxanthan gum and partially hydrolyzed polyacrylamide-with a cationic surfactantlike cetyltrimethylammonium bromide (CTAB) contributes to enhanced stericstabilization of the nanoparticle dispersion. The nanofluid exhibits controllableviscosity, enabling efficient suspension and transport of drill cuttings during oilfieldoperations. The tunability of viscosity further mitigates problems such as fluid loss,pipe sticking, and formation damage, all while promoting optimal filter cakeformation. This leads to more efficient drilling performance and reduced risk ofwellbore instability.

[0051] Notably, the nanofluid formulation improves thermal conductivity andlubricity, both of which are critical for high-temperature downhole environments.The TiO2 nanoparticles enhance heat dissipation near the drill bit, preventingthermal degradation of both the drilling fluid and the bit itself. Simultaneously, thenanofluid acts as a lubricant, reducing torque and drag on the drill string. Theseproperties collectively lead to improved rate of penetration (ROP), reduced wear onthe drill bit, and extended tool life-all of which translate to a substantial reductionin operational time and costs.

[0052] Therefore, the disclosed titanium dioxide nanofluid composition of thepresent invention and its preparation method offer a technically superior andenvironmentally responsible alternative to conventional drilling fluid additives. Theformulation is not only compatible with existing oilfield practices but alsocustomizable to adapt to diverse reservoir conditions. By integrating enhancedthermal stability, lubrication, and colloidal stability within a single additive system,the invention addresses longstanding challenges in drilling fluid technology andcontributes to more sustainable and efficient hydrocarbon extraction.

[0053] While specific language has been used to describe the invention, anylimitations arising on account of the same are not intended. As would be apparentto a person skilled in the art, various working modifications may be made to themethod in order to implement the inventive concept as taught herein.

[0054] The figures and the foregoing description give examples of embodiments.Those skilled in the art will appreciate that one or more of the described elementsmay well be combined into a single functional element. Alternatively, certainelements may be split into multiple functional elements. Elements from oneembodiment may be added to another embodiment. For example, order of processesdescribed herein may be changed and are not limited to the manner describedherein. Moreover, the actions of any flow diagram need not be implemented in theorder shown; nor do all of the acts need to be necessarily performed. Also, thoseacts that are not dependent on other acts may be performed in parallel with the otheracts. The scope of embodiments is by no means limited by these specific examples.

Claims

1. A titanium dioxide (TiO2) nanofluid composition comprising: an aqueous base fluid comprising an aqueous solution of at least one oilfield polymer; a pH-adjusting agent; a colloidal dispersion of titanium dioxide (TiO2) nanoparticles in the aqueous base fluid; and a cationic surfactant at critical micelle concentration 0.3645 g / L, wherein the titanium dioxide (TiO2) nanoparticles have a particle size in a range of 20 to 200 nanometers and a zeta potential between -30 millivolts (mV) up to - 65 mV, and are uniformly dispersed in the aqueous base fluid.

2. The titanium dioxide (TiO2) nanofluid composition as claimed in claim 1, wherein the oilfield polymer is selected from xanthan gum, partially hydrolyzed polyacrylamide (HPAM), guar gum and polyacrylamide (PAM).

3. The titanium dioxide (TiO2) nanofluid composition as claimed in claim 1, wherein the cationic surfactant is cetyltrimethylammonium bromide (CTAB).

4. The titanium dioxide (TiO2) nanofluid composition as claimed in claim 1, wherein the concentration of the titanium dioxide nanoparticles is in the range of 0.5 wt.% to 2 wt.%.

5. The titanium dioxide (TiO2) nanofluid composition as claimed in claim 1, wherein the concentration of the oilfield polymer in the aqueous base fluid is in the range of 500 ppm to 2000 ppm.

6. The titanium dioxide (TiO2) nanofluid composition as claimed in claim 1, wherein the pH-adjusting agent comprises ammonium hydroxide in a concentration sufficient to maintain pH between 9 and 10.

7. The titanium dioxide (TiO2) nanofluid composition as claimed in claim 1, wherein the TiO2 nanofluid composition retains dispersion stability and viscosity at a temperature of 80 °C to 100 °C.

8. The titanium dioxide (TiO2) nanofluid composition as claimed in claim 1, wherein the TiO2 nanofluid composition exhibits a viscosity of 3 to 100 cP at a shear rate of 1000 to 1 s-1 at 25 °C.

9. A method for preparing a titanium dioxide (TiO2) nanofluid composition, the method comprising: preparing an aqueous base fluid by dissolving at least one oilfield polymer selected from xanthan gum and partially hydrolyzed polyacrylamide (HPAM) in deionized water at a concentration of 500 ppm to 2000 ppm; adjusting pH of the aqueous base fluid to a value in a range of 9 to 10 using ammonium hydroxide; mixing tetrabutyl orthotitanate (TBOT) with ethanol to obtain a precursor mixture followed by adding the precursor mixture dropwise into the aqueous base fluid under continuous stirring to induce hydrolysis to obtain titanium dioxide nanoparticles in situ; adding a cationic surfactant comprising cetyltrimethylammonium bromide (CTAB) to the mixture at a concentration of 0.3645 gm / L; and continuing stirring the mixture for a duration sufficient to obtain a uniform colloidal dispersion of the titanium dioxide nanoparticles providing the titanium dioxide (TiO2) nanofluid composition having a particle size in the range of 20 to 200 nanometers and a zeta potential greater than -30 millivolts.

10. The method as claimed in claim 9, wherein the concentration of the TBOT is selected to yield a titanium dioxide nanoparticle concentration in the range of 0.5 wt.% to 2 wt.% in the titanium dioxide (TiO2) nanofluid composition.

11. The method as claimed in claim 9, wherein the ethanol is added at a volume ratio of 3:1 to 4.35:1 of TBOT.

12. The method as claimed in claim 9, wherein the cationic surfactant comprising cetyltrimethylammonium bromide (CTAB) is added at critical micelle concentration (CMC).

13. The method as claimed in claim 9, wherein the titanium dioxide (TiO2) nanofluid composition is characterized by a stable colloidal dispersion with no visible sedimentation after 30 days of storage at room temperature.