Patent Publication Number: US-2022235257-A1

Title: Synthetic functionalized additives, methods of synthesizing, and methods of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of and claims priority to U.S. application Ser. No. 16/558,772 filed Sep. 3, 2019, and entitled “SYNTHETIC FUNCTIONALIZED ADDITIVES, METHODS OF SYNTHESIZING, AND METHODS OF USE” (attorney docket SA6329PA), which claims priority to U.S. Provisional Application 62/726,512, filed on Sep. 4, 2018, the contents of each of which are incorporated by reference herein in their respective entireties. 
    
    
     TECHNICAL FIELD 
     Embodiments described herein generally relate to compositions and methods for use as fluid additives and, more specifically, to compositions and methods for enhancing drilling fluids in a downhole environment. 
     BACKGROUND 
     Wellbore construction and production procedures may include drilling, completion, matrix stimulation, fracturing, or other wellbore construction and production enhancement procedures. Some wellbore construction and production procedures may utilize wellbore fluids. Drilling fluids include water-based muds (WBMs), oil-based muds (OBMs), and pneumatic fluids, which may be utilized in subterranean and oil well drilling and completion operations. 
     SUMMARY 
     WBMs have some inherent advantages when compared to other drilling fluids, such as, in some embodiments, being more economically viable, more environmentally benign, or both. However, WBMs may experience thinning while drilling under high temperature high pressure (HTHP) downhole conditions. HTHP conditions may be defined having an undisturbed bottomhole temperature of greater than 300° F. (149° C.) and a pore pressure of at least 0.8 psi/ft (˜15.3 lbm/gal). Due to this thinning, problems may include one or more of pipe sticking, low rates of penetration of the drill bit, and high torque requirements for drilling operations. 
     Bentonite clays, polymers, or combinations of these may be utilized in an attempt to maintain the rheological properties of WBMs. However, bentonite clays may lose their effectiveness at HTHP, even when added in large quantities. Polymers, either natural or synthetic, may undergo degradation or thinning of viscosity with respect to a rise in temperature. 
     As such, there are needs for additives that may improve the stability of WBMs&#39; rheological properties and filtration behaviors in HTHP wells. Embodiments of the present disclosure meet those needs by providing, according to one or more embodiments, synthetic functionalized additives. In some embodiments, the disclosed synthetic functionalized additives may be utilized in drilling fluids used for wellbore applications. In some embodiments, the synthetic functionalized additives may be utilized to at least partially reduce thinning of the drilling fluids while drilling under HTHP downhole conditions. In some embodiments, WBMs containing the synthetic functionalized additives described herein may demonstrate improved rheological properties while reducing the number of other additives (that is, bentonite clays, polymers, or combinations of these) in the WBMs. In additional embodiments, synthetic functionalized additives may be used in combination with viscosifiers such as, for example, partially-hydrolyzed polyacrylamide/polyacrylate (PHPA) 
     According to one embodiment, a synthetic functionalized additive may comprise a layered magnesium silicate. The layered magnesium silicate may comprise a first functionalized silicate layer comprising a first tetrahedral silicate layer covalently bonded to at least two different functional groups, an octahedral brucite layer, the octahedral brucite layer comprising magnesium, and a second functionalized silicate layer comprising a second tetrahedral silicate layer covalently bonded to at least two different functional groups. The octahedral brucite layer may be positioned between the first functionalized silicate layer and the second functionalized silicate layer. The at least two different functional groups covalently bonded to the first tetrahedral silicate layer may be the same or different than the at least two different functional groups covalently bonded to the second tetrahedral silicate layer. 
     According to another embodiment, a drilling fluid may comprise an aqueous base fluid and the synthetic functionalized additive described in the paragraph immediately above. 
     According to yet another embodiment, a drilling fluid may be produced by a method comprising mixing a magnesium salt with a fluid medium to produce a magnesium-containing fluid, adding a first silane and a second silane to the magnesium-containing fluid to produce a reactant mix, where the first silane and the second silane have different compositions, adding an aqueous hydroxide to the reactant mix to produce a reaction mixture, mixing the reaction mixture for a mix period, refluxing the reaction mixture for a reflux period to produce a product mix, treating the product mix to separate the synthetic functionalized additive, adding an aqueous base fluid and a viscosifier, and mixing the aqueous base fluid, the viscosifier, and the synthetic functionalized additive to produce the drilling fluid. 
     These and other embodiments are described in more detail in the following Detailed Description in conjunction with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG. 1  is a schematic depiction of a layered magnesium silicate, according to one or more embodiments of the present disclosure; 
         FIG. 2  is a schematic depiction of the gelation mechanism of a conventional water-based drilling fluid including sodium-monmorillonite-rich bentonite; 
         FIG. 3  is schematic depiction of the effect of excess alkali or alkaline earth cations or organic cations on the conventional water-based drilling fluid; and 
         FIG. 4  is schematic depiction of the effect of excess alkali or alkaline earth cations or organic cations on a drilling fluid including the synthetic functionalized additives, according to one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are directed to synthetic functionalized additives, methods of producing the same, and methods of use. 
     As used throughout, “brucite” may refer to a magnesium having monomeric formula MgO(OH) 2 . 
     As used throughout, “octahedral” may refer to the crystal pattern defining an octahedron, with eight triangular faces, twelve straight edges, and six vertices. 
     As used throughout, “tetrahedral” may refer to the crystal pattern defining a tetrahedron, with four triangular faces, six straight edges, and four vertices. 
     As used throughout, “silane” may refer to a silicon compound containing at least three alkoxy groups (an alkyl group bonded to oxygen), where the 4th substituent includes a functional group and may be a fourth alkoxy group or may be a carbon containing compound. 
     As used throughout, “viscosifier,” “viscosity modifier,” and “rheological modifier” may refer to compounds that change rheological properties when added to a fluid. Viscosifiers may be used to increase the viscosity of a fluid. 
     As used throughout, “thixotropic” may refer to the tendency of a fluid or gel to exhibit a decrease in viscosity when a stress or a change in temperature is applied, such as mixing, shaking, shearing, or agitating. This property may be time-dependent. Thixotropic control additives may include additives that may minimize the decrease in viscosity of a fluid when a stress or a change in temperature is applied. 
     As used throughout, “suspension additives” may refer to additives that may reduce settling of solid particles in fluids or gels. 
     As used throughout, “rheologically-independent behavior” may refer to a fluid that does not experience changes in rheological properties, such as viscosity and thixotropy, due to a variation in an applied stress. Applied stresses may include shear stress, temperature, and combinations of the same. For example, a variation in an applied stress would occur when a rate of mixing is increased or decreased. An example of a fluid that exhibits rheologically-independent behavior is a fluid that does not experience a change in viscosity due to a variation in the temperature. 
     Embodiments of the present disclosure are directed to synthetic functionalized additives and methods of producing the same. The synthetic functionalized additives may include a layered magnesium silicate having mixed functional groups covalently bonded to a tetrahedral silicate layer. A schematic depiction of a layered magnesium silicate, according to one or more embodiments of the present disclosure, is shown in  FIG. 1 . 
     Embodiments of the layered magnesium silicate may include a material that includes magnesium. In some embodiments, the material that includes magnesium may be a magnesium salt. In further embodiments, the magnesium salt may be magnesium chloride, magnesium nitrate, magnesium sulfate, or magnesium bromide. In some embodiments, the material that includes magnesium may include magnesium chloride hexahydrate. In embodiments, the material that includes magnesium may include magnesium oxide or magnesium hydroxide. 
     In some embodiments, the material that includes magnesium may be naturally-occurring. For example, in some embodiments, magnesium hydroxide may be obtained from a naturally-occurring mineral, such as brucite. In other embodiments, the naturally-occurring material that includes magnesium may include magnesium-rich bittern brine, which may be a byproduct of sodium chloride production from sea water. 
     In embodiments, the material that includes magnesium may be present as a layer of octahedral brucite positioned between two functionalized silicate layers. In some embodiments, layer of octahedral brucite may be synthesized as part of the process of producing the layered magnesium silicate. The octahedral brucite layer may be synthesized by reacting a magnesium salt with an aqueous hydroxide. Any magnesium salt that may react with a hydroxide may be used, including, but not limited to, magnesium chloride, magnesium chloride hydrates, magnesium nitrate, magnesium nitrate hydrates, magnesium bromide, magnesium bromide hexahydrate, and combinations of the same. Magnesium chloride hydrates have the chemical formula MgCl 2 (H 2 O) x , where x is selected from 2, 4, 6, 8, and 12. Magnesium nitrate hydrates have the chemical formula Mg(NO 3 ) 2 (H 2 O) y , where y is selected from 0, 2, and 6. In embodiments, the aqueous hydroxide may include a hydroxide in water. The hydroxide may be present in an amount of from 2 wt. % to 10 wt. %, based on the total weight of the aqueous hydroxide. In embodiments, the hydroxide may be present in an amount of from 2 wt. % to 8 wt. %, from 2 wt. % to 6 wt. %, from 2 wt. % to 4 wt. %, from 4 wt. % to 10 wt. %, from 4 wt. % to 8 wt. %, from 4 wt. % to 6 wt. %, from 6 wt. % to 10 wt. %, from 6 wt. % to 10 wt. %, or from 8 wt. % to 10 wt. %, based on the total weight of the aqueous hydroxide. The hydroxide may be any hydroxide that may react with a salt. Examples of the hydroxide may include sodium hydroxide, potassium hydroxide, ammonium hydroxide, and combinations of the same. 
     Embodiments of the layered magnesium silicate may include one or more functionalized silicate layers. In embodiments, each of the functionalized silicate layers contains a tetrahedral silicate layer and at least two functional groups. In embodiments, the at least two functional groups are different by having different chemical structures. References to “a functional group” should be interpreted to include multiple instances of one type of functional group bonded to the tetrahedral silicate layer and alternately multiple instances of multiple types of functional groups bonded to the tetrahedral silicate layer. Without being bound by theory, it is believed that having mixed functional groups may improve the hydrogen bonding in the aqueous medium. In some conventional methods, an alkaline solution (NaOH) may be added to improve hydrogen bonding. It is believed that the presence of mixed functionalities may reduce the amount of alkaline solution required to activate hydrogen bonding, which may, thus, improve gel strength. 
     The functional groups may be covalently bonded to the tetrahedral silicate layer. The functionalized silicate layers may be obtained by reacting the octahedral brucite with a silane. Any silane containing a functional group and capable of forming a tetrahedral layer may be used. The silanes may be available as an aqueous solution, a non-aqueous solution, or a liquid. Examples of silanes for use in the layered magnesium silicate include phenyltrimethoxysilane, trimethoxy(propyl)silane, trimethoxymethylsilane, hexadecyltrimethoxysilane, octyltriethoxysilane, tetraethyl orthosilicate, N-[3-(trimethoxysilyepropyl]ethylenediamine, (3-aminopropyl)triethoxysilane, silanes having the formula RSi(OR″)3, and combinations of the same. Where silanes have the formula RSi(OR″)3, R″ may include a methyl group (—CH 3 ), an ethyl group (—C 2 H 5 ), and combinations of the same; and R may include alkyl groups, aryl groups, and combinations of the same. Alkyl groups may include alkyl groups having saturated groups, alkyl groups having unsaturated groups, alkyl groups having functional substituents, and combinations of the same. Aryl groups may include aryl groups having saturated groups, aryl groups having unsaturated groups, aryl groups having functional substituents, and combinations of the same. The functional substituents may include amines, carboxylates, amides, acrylates, thiols, hydroxyls, isocyanates, methacrylates and combinations of the same. The functional substituents may be attached at the end of the chain, may be attached in-between, and combinations of the same. The functional substituents form functional groups of the silane. In at least one embodiment, the silanes for use in the layered magnesium silicate include phenyltrimethoxysilane, trimethoxy(propyl)silane, trimethoxymethylsilane, hexadecyltrimethoxysilane, octyltriethoxysilane, tetraethyl orthosilicate, N-[3-(trimethoxysilyepropyl]ethylenediamine, (3-aminopropyl)triethoxysilane, and combinations of the same. In at least one embodiment, the silane has the formula RSi(OR″) 3 . 
     The silanes may be selected based on the desired functional group. The functional groups may include hydroxyl groups (-OH); saturated alkyl groups having the formula (—CH 2 (CH 2 ) x CH 3 ), where x is an integer between 0 and 18, phenyl groups, amine groups, diamine groups, carboxylate groups, amide groups, acrylate groups, thiol groups, methacrylate groups, isocyanate groups; and combinations of the same. Table 1 lists the functional group resulting from some silanes. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Silane 
                 Functional Groups 
               
               
                   
               
             
            
               
                 phenyltrimethoxysilane 
                 Phenyl group, —C 6 H 5   
               
               
                 trimethoxy(propyl)silane 
                 Saturated alkyl group, —CH 2 (CH 2 )CH 3   
               
               
                 trimethoxymethylsilane 
                 Methyl group, —CH 3   
               
               
                 hexadecyltrimethoxysilane 
                 Saturated alkyl group, —CH 2 (CH 2 ) 14 CH 3   
               
               
                 octyltriethoxysilane 
                 Saturated alkyl group, —CH 2 (CH 2 ) 6 CH 3   
               
               
                 tetraethyl orthosilicate 
                 —OC 2 H 5   
               
               
                 N-[3-(trimethoxysilyl)pro- 
                 Diamine group, —(CH 2 ) 3 NH(CH 2 ) 2 NH 2   
               
               
                 pyl]ethylenediamine 
               
               
                 (3-aminopropyl)triethoxysi- 
                 Amine group, —(CH 2 ) 3 NH 2   
               
               
                 lane 
               
               
                 RSi(OR″) 3   
                 R″ is a methyl group (—CH 3 ), an ethyl 
               
               
                   
                 group (—C 2 H 5 ), and combinations of 
               
               
                   
                 the same; and R is an alkyl group, 
               
               
                   
                 an aryl group, and combinations of 
               
               
                   
                 the same. 
               
               
                   
               
            
           
         
       
     
     Producing the functionalized silicate layer from the at least two silanes that contains the desired functional groups results in a synthetic functionalized additive where the functional group is covalently bonded to the tetrahedral silicate layer of the layered magnesium silicate. As the functional groups extend from the tetrahedral silicate layer away from the octahedral brucite layer, the functional groups serve to separate the layered magnesium silicate platelets, as shown in  FIG. 1 . 
     In some embodiments, the layered magnesium silicate may have a silicon to magnesium ratio of from 0.7:1 to 1.5:1 or from 1:1 to 1.4:1 by mole. In further embodiments, the silicon to magnesium ratio may be 1.33 by mole. Without being bound by theory, it is believed that the silicon to magnesium ratio may affect the crystallinity of the synthetic functionalized additive. 
     In some embodiments, the layered magnesium silicate may have a thickness of from 1 nm to 5 nm. In other embodiments, the layered magnesium silicate may have a thickness of from 1 nm to 4 nm, from 1 nm to 3 nm, from 1 nm to 2 nm, from 2 nm to 5 nm, from 2 nm to 4 nm, from 2 nm to 3 nm, from 3 nm to 5 nm, from 3 nm to 4 nm, or from 5 nm to 5 nm. In some embodiments, the layered magnesium silicate may have a lateral dimension of from 10 nm to 2000 nm (2 microns), from 50 nm to 1000 nm, or from 100 nm to 500 nm. In embodiments, the overall thickness of the layered magnesium silicate may depend on the length of the functional groups. 
     Methods of producing a synthetic functionalized additive will now be described. As stated previously, in some embodiments, the synthetic functionalized additive may include a layered magnesium silicate. For example, the methodology of synthesizing the layered magnesium silicate may be summarized by the following reaction (1), where LMS represents the layered magnesium silicate, in shorthand: 
     
       
         
           
             
               
                 
                   
                     MgXW 
                     + 
                     
                       
                         GYSi 
                         ⁡ 
                         
                           ( 
                           Z 
                           ) 
                         
                       
                       3 
                     
                   
                   → 
                   LMS 
                 
               
               
                 
                   ( 
                   
                     EQ 
                     . 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ) 
                 
               
             
           
         
       
     
     where X may include Cl 2 , Br 2 , I 2 , (OH) 2 , O, formates, citrates, or combinations; W may include water molecules and hydrates, G may include primary amines, secondary amines, tertiary amines, hydroxyl, epoxies, thiols, phenols, aminobenzenes, carboxylates, and combinations of these groups, Y may include ethyl, propyl, ethylene, diamine, diethylene thiamine, triethylene tetramine, phenyl, or combinations; and Z may include methoxy, ethanol, isopropyl alcohol, glycol, ethylene glycol, or combinations. In embodiments, the reaction may take place in alkalis including, for example, sodium hydroxide, potassium hydroxide, or combinations; alcohols including, for example, methanol, ethanol, isopropyl alcohol, glycol, ethylene glycol, or combinations. 
     In embodiments of the presently-described methods, the synthetic functionalized additives may be reproduced resulting in consistent composition from batch to batch. Consistent and reproducible results may be an advantage over other naturally-derived additives, such as organoclays or organically modified layered materials, which are subject to the impurities in the natural source. Additionally, the presently-described methods may be manipulated to produce certain results in the product, such as changing the crystallinity. Advantageously, the synthetic functionalized additives provide consistency for the duration of an application and reduce or eliminate the need for additional additives in drilling fluid formulations during use and application. 
     In embodiments, an amount of the magnesium salt may be mixed with a fluid medium to produce a magnesium containing fluid. Any fluid medium suitable for suspending a metal oxide or metal hydroxide reaction. The fluid medium may include water, an alcohol, and combinations of the same. Examples of the alcohol may include methanol, ethanol, propanol, butanol, and combinations. The amount of magnesium salt may be in the range from 3 wt. % to 15 wt. % based on the total weight of the magnesium containing fluid. In other embodiments, the amount of magnesium salt may be in the range from 3 wt. % to 10 wt. %, from 3 wt. % to 5 wt. %, from 5 wt. % to 15 wt. %, from 5 wt. % to 10 wt. %, or from 10 wt. % to 15 based on the total weight of the magnesium containing fluid. 
     An amount of at least two silanes may be added to the magnesium-containing fluid to produce a reactant mix. In embodiments, the amount of the at least two silanes added may have a combined weight from 3 wt. % to 15 wt. % based on the total weight of the reactant mix. In other embodiments, the amount of the at least two silanes may be a combined weight from 3 wt. % to 10 wt. %, from 3 wt. % to 5 wt. %, from 5 wt. % to 15 wt. %, from 5 wt. % to 10 wt. %, or from 10 wt. % to 15 based on the total weight of the reactant mix. The combined amount of the at least two silanes added may be determined to maintain a silicone to magnesium molar ratio in the layered magnesium silicate of between 0.7:1 to 1.5:1, or from 1:1 to 1.4:1. In at least one embodiment, the combined amount of the at least two silanes added results in a silicone to magnesium molar ratio in the layered magnesium silicate of 1.33:1. 
     It is believed that adding the amount of the at least two silanes to the magnesium-containing fluid may be important in producing a synthetic functionalized additive having the layered structure. A change in the order of mixing, by adding the magnesium salt to the at least two silanes may produce amorphous materials that do not possess the layered structure of the presently-disclosed synthetic functionalized additive. 
     An amount of aqueous hydroxide may be added to the reactant mix to produce the reaction mixture. In embodiments, the formation of the layer of octahedral brucite may begin upon addition of the aqueous hydroxide. Hydrolysis of the at least two silanes may begin upon addition of the aqueous hydroxide. In some embodiments, the aqueous hydroxide is sodium hydroxide. The aqueous hydroxide may adjust the pH of the reactant mix. The aqueous hydroxide may be added to the reactant mix to reach a target pH. In embodiments, the target pH may be from 7 to 12. In some embodiments, the target pH may be from 9 to 10. In further embodiments, the aqueous hydroxide is added while stirring. In further embodiments, the aqueous hydroxide is added while stirring for 30 minutes. 
     In embodiments, each of the addition steps may be performed at a temperature in the range of from 10 degrees Celsius (° C.) to 35° C. In some embodiments, the addition steps may be performed at a temperature of from 20° C. to 30° C. In some embodiments, each of the addition steps may be performed at ambient pressure. Each addition step may be followed by a period of mixing. 
     The reaction mixture may be prepared in one reaction vessel. In some embodiments, the reaction vessel may be fitted with a stirring mechanism such that the mixture is constantly stirred during the addition steps. In some embodiments, the reaction vessel may be fitted with a condenser. In some embodiments, the reaction vessel may be configured for hydrothermal reaction, where the reaction mixture may be maintained at a pressure at the reflux conditions. 
     The reaction mixture may be mixed for a mixing period. In embodiments, the mixing period may be for at least 30 minutes or at least one hour. In some embodiments, the mixing period may be from 30 minutes to 72 hours, from 4 to 72 hours, from 12 hours to a 72 hours, or from 24 hours to 48 hours. Mixing the reaction mixture under an alkaline condition may enable the formation of brucite and the subsequent hydrolysis of the silanes. 
     Following the mixing period, the reaction mixture may be refluxed in the reaction vessel for a reflux period to produce the product mix. The reflux period may be at least 2 hours. In some embodiments, the reflux period may be from 2 hours to 1 week (168 hours), from 2 hours to 144 hours, from 2 hours to 120 hours, from 2 hours to 96 hours, from 2 hours to 72 hours, from 2 hours to 48 hours, or from 2 hours to 24 hours. 
     During the reflux period, the temperature in the reaction vessel may be increased to the refluxing condition. The refluxing condition may be the boiling point of the reaction mixture and may be from 25° C. to 110° C. In some embodiments, the refluxing condition may be from 25 ° C. to 100° C., from 25° C. to 75° C., from 25° C. to 50° C., from 50° C. to 110° C., from 50° C. to 100 ° C., from 50° C. to 75° C., from 75° C. to 110° C., from 75° C. to 100° C., or from 100° C. to 110° C. The condensation reactions of the at least two silanes may begin when the temperature in the reaction mixture is increased to the refluxing condition. The refluxing condition may allow for the two or more silanes to react to form the tetrahedral silicate layer having mixed functionalities on either side of the layer of octahedral brucite, resulting in the functionalized synthetic additive. The condensation reactions of the silanes continues for the reflux period. The functionalized silicate layers form on the layer of octahedral brucite during the reflux period. Without being bound by theory, it is believed that the reflux conditions may improve the crystallinity of the functionalized silicate layers. In embodiments, the length of the reflux period may influence the crystallinity of the layered magnesium silicates. In some embodiments, a longer reflux period may result in an increased lateral dimension. A hydrothermal reaction during the reflux period may allow crystallization and growth in the lateral dimension. In some embodiments, as the components boil, they may enter the condenser fitted onto the reaction vessel. 
     Following the refluxing step, the product mix may be subjected to one or more treatment operations to separate the solid layered magnesium silicates from the liquids in the product mix to produce the synthetic functionalized additive. The treatment operations may include reducing the temperature of the product mix, separating the solids, washing the solids, and drying the solids under vacuum. Separating the solids may be performed through filtration or through centrifuging. The separated solids may be washed with de-ionized water. In some embodiments, the product mix may be washed with deionized water more than once, for example, three times. In some embodiments, drying the solids under vacuum may be done at elevated temperatures or at room temperature. In embodiments, the product mix is dried at a temperature of at least 50° C., at least 60 C, at least 70 C, or at least 80 C. 
     Embodiments of the synthetic functionalized additive may be utilized in a variety of applications. The synthetic functionalized additive may be used as a viscosifier, a thixotropic control additive, a suspension additive, a nucleating agent additive, and a release rate control additive. The synthetic functionalized additive may be used as additives in well fluids, paints, inks, cosmetic formulations, personal care formulations, synthesis of nanocomposites from thermoplastic or thermosetting polymers, and therapeutic formulations (sustained release). Well fluids may include drilling fluids, packer fluids, lost circulation fluids, production fluids, and combinations of the same. The well fluid may be an aqueous-based fluid, an oil-based fluid, or combinations of the same. In embodiments, the synthetic functionalized additives may be used in place of organophilic nanosilicas. 
     In at least one embodiment, the synthetic functionalized additive may be mixed with a well fluid as a viscosifier to produce a rheologically-modified well fluid. The amount of synthetic functionalized additive added to the well fluid may be from 1 gram to 10 grams. In other embodiments, the amount of synthetic functionalized additive added to the well fluid may be from 1 gram to 5 grams or from 5 gram to 10 grams. The amount of synthetic functionalized additive in the rheologically-modified well fluid may be in an amount between 0.1% w/v and 20% w/v, alternately 0.5% w/v and 5% w/v, alternately between 1% w/v and 4% w/v, alternately between 1.5% w/v and 3.5% w/v. In at least one embodiment, the amount of the synthetic functionalized additive is 2% w/v. The rheologically-modified well fluid may be injected into a well. 
     Embodiments of a drilling fluid including the synthetic functionalized additive will now be described. Embodiments of drilling fluids including the synthetic functional additives may exhibit rheologically-independent behavior under high pressure and high temperature conditions meaning the drilling fluids may maintain their properties, such as viscosity and thixotropy, in the face of stresses and temperature. As such, in some embodiments, drilling fluids including the synthetic functionalized additive may be utilized to at least partially reduce thinning of the drilling fluids while drilling under HTHP downhole conditions. When compared to conventional drilling fluids, the drilling fluids including the synthetic functional additives may be less susceptible to stresses than conventional drilling fluids that do not exhibit rheologically-independent behavior. Drilling fluids containing the synthetic functional additives may, in embodiments, exhibit less change in viscosity due to variation in temperature as compared to the drilling fluids containing conventional rheology modifiers, such as organoclays, instead of the synthetic functional additives. 
     For a conventional drilling fluid formulation, several additives (that is, more than 10 types) may be required in order for the formulation to achieve desired rheological properties in well-treatment applications. In conventional drilling fluids, hydrophilic clays (including bentonites/montmorrilonites/hectorites) have been employed as viscosifiers in water-based drilling fluids in an attempt to maintain the rheological properties. These types of clays may be referred to as cationic layered materials. As shown in  FIGS. 2-3 , when these clays are added in to water, the lamellar structures of the bentonite may be disrupted and individual alumino-silcate platelets are dispersed in water. However, the network structure ( FIG. 2 ) may not be stable in the presence of other cations, e.g. inorganic cations (including K + , Ca 2+ , Mg 2+ ) or organic cations (quaternary ammonium salts). As shown in  FIG. 3 , the presence of these cationic species, the layered materials under goes flocculation and thus lose the rheological properties. Therefore, the use of Smectite clays may be limited in drilling fluid applications. 
     Embodiments of the presently-described synthetic functional additives may include a layered magnesium silicate having strong covalent bonds between the mixed functional groups and the tetrahedral silicate layer. Without being bound by theory, it is believed that these covalent bonds between the mixed functional groups and the tetrahedral silicate layers may be more resistant to stress and remain intact during well-treatment processes, when compared to conventional drilling fluids. As shown in  FIG. 4 , drilling fluids including the presently-described synthetic functional additives may exhibit stable gelation in in aqueous medium irrespective of the presence of alkali or alkaline earth cations or organic cations. Therefore, in some embodiments, a drilling fluid formulation that includes the presently-disclosed synthetic functionalized additives may reduce or eliminate the need for additional additives to achieve desired rheological properties, when compared to a conventional drilling fluid formulation. In some embodiments, the drilling fluid formulation that includes the presently-disclosed synthetic functionalized additives may include less than 10 or less than 5 additional additives. 
     In further embodiments, the drilling fluid formulation that includes the presently-disclosed synthetic functionalized additives may require three or four additional additives. Examples of additional additives may include viscosifiers (including natural polymers, synthetic polymers, hydrophilic clays), shale inhibitors, lost circulation additives, fluid loss additives, emulsifiers, antifoaming agents, surfactants, pH controlling compounds, lubricants, weighing materials, and fluid medium (including water, brine, sea water). 
     In embodiments, the drilling fluid formulation that includes the presently-disclosed synthetic functionalized additives may additionally comprise a viscosifier. In further embodiments, the viscosifier may comprise or consist of partially-hydrolyzed polyacrylamide/polyacrylate (PHPA). As is understood in the art, PHPA is a partially hydrolyzed linear copolymer of acrylate (anionic) and acrylamide (nonionic) monomers. The PHPA may be a random copolymer. In embodiments, the ratio of acrylic acid to acrylamide groups on the polymer chain can be varied in manufacturing, as can molecular weight. Another variable is the base used to neutralize the acrylic acid groups, which may include NaOH, KOH, and NH4OH. In some embodiments, the PHPA utilized in the drilling fluids described herein may have a concentration of from 10% to 30% acrylate groups. 
     Without being bound by theory, it is believed that the mixed functionalities of the synthetic functionalized additive (i.e., —OH and —NH2) form a hydrogen bond network with acrylamide and carboxylate groups of the PHPA. Furthermore, the carboxylate group may react with the —NH2 functionality of synthetic functionalized additive at higher temperatures (for example, greater than 200° F. (93.3° C.)) to form stronger linkages that preserve the viscosity of the drilling fluid at elevated temperatures. 
     The drilling fluid may include an aqueous base fluid and embodiments of the synthetic functionalized additive. The aqueous base fluid may include barite, bentonite, silica flour, polymers, viscosifiers, primary or secondary emulsifiers, fluid loss control additives, fluid stabilizers, loss circulation additives, metal salts, or combinations thereof. In embodiments, the aqueous base fluid of the subterranean wellbore fluid may include water. 
     According to one or more embodiments, the drilling fluid may comprise viscosifier (or PHPA) in an amount of from 0.5 lb/bbl to 10 lb/bbl, such as from 1 lb/bbl to 5 lb/bbl, or from 3 lb/bbl to 4 lb/bbl. For example, the drilling fluid may comprise PHPA in an amount of from 0.5 lb/bbl to 1 lb/bbl, from 1 lb/bbl to 2 lb/bbl, from 2 lb/bbl to 3 lb/bbl, from 3 lb/bbl to 4 lb/bbl, from 4 lb/bbl to 5 lb/bbl, from 5 lb/bbl to 6 lb/bbl, from 6 lb/bbl to 7 lb/bbl, from 7 lb/bbl to 8 lb/bbl, from 8 lb/bbl to 9 lb/bbl, from 9 lb/bbl to 10 lb/bbl, or any combination of these ranges. 
     In one or more embodiments, a drilling fluid may comprise from 0.1 wt. % to 10 wt. % of the synthetic functionalized additive described herein. For example, a drilling fluid may comprise from 0.1 wt. % to 1 wt. %, from 1 wt. % to 2 wt. %, from 2 wt. % to 3 wt. %, from 3 wt. % to 4 wt. %, from 4 wt. % to 5 wt. %, from 5 wt. % to 6 wt. %, from 6 wt. % to 7 wt. %, from 7 wt. % to 8 wt. %, from 8 wt. % to 9 wt. %, from 9 wt. % to 10 wt. %, or any combination of these ranges, of the synthetic functionalized additive described herein 
     In some embodiments, the weight ratio of viscosifier (or PHPA) to layered magnesium silicate may be from 1:5 to 5:1, such as about 1:3, about 1:2, about 1:1, about 2:1, or about 3:1. For example, the weight ratio of viscosifier (or PHPA) to layered magnesium silicate may be from 1:4 to 1:3, from 1:3 to 1:2, from 1:2 to 1:1, from 1:1 to 2:1, from 2:1 to 3:1, from 3:1 to 4:1, or any combination of these ranges. 
     In embodiments, the drilling fluid including the synthetic functional additives may have a gel strength (at temperatures of from 77° F. to 500° F., for 10 seconds) of from 1 lb/100 ft 2  to 5 lb/100 ft 2 , from 1 lb/100 ft 2  to 4 lb/100 ft 2 , from 1 lb/100 ft 2  to 3 lb/100 ft 2 , from 1 lb/100 ft 2  to 2 lb/100 ft 2 , from 2 lb/100 ft 2  to 5 lb/100 ft 2 , from 2 lb/100 ft 2  to 4 lb/100 ft 2 , from 2 lb/100 ft 2  to 3 lb/100 ft 2 , from 3 lb/100 ft 2  to 5 lb/100 ft 2 , from 3 lb/100 ft 2  to 4 lb/100 ft 2 , or from 4 lb/100 ft 2  to 5 lb/100 ft 2 . In embodiments, the drilling fluid including the synthetic functional additives may have a gel strength (at temperatures of from 77° F. to 500° F., for 10 minutes) of from 5 lb/100 ft 2  to 80 lb/100 ft 2 , from 5 lb/100 ft 2  to 50 lb/100 ft 2 , from 5 lb/100 ft 2  to 30 lb/100 ft 2 , from 5 lb/100 ft 2  to 10 lb/100 ft 2 , from 10 lb/100 ft 2  to 80 lb/100 ft 2 , from 10 lb/100 ft 2  to 50 lb/100 ft 2 , from 10 lb/100 ft 2  to 30 lb/100 ft 2 , from 30 lb/100 ft 2  to 80 lb/100 ft 2 , from 30 lb/100 ft 2  to 50 lb/100 ft 2 , or from 501b/100 ft 2  to 80 lb/100 ft 2 . 
     In embodiments, the drilling fluid including the synthetic functional additives may have a plastic viscosity (at temperatures of from 77° F. to 500° F.) of from 10 centipoise (cP) to 100 cP. In some embodiments, the drilling fluid including the synthetic functional additives may have a plastic viscosity (at temperatures of from 77° F. to 500° F.) of from 10 cP to 80 cp, from 10 cp to 60 cp, from 10 cp to 40 cp, from 10 cp to 20 cp, from 20 cp to 100 cp, from 20 cp to 80 cp, from 20 cp to 60 cp, from 20 cp to 40 cp, from 40 cp to 100 cp, from 40 cp to 80 cp, from 40 cp to 60 cp, from 60 cp to 100 cp, from 60 cp to 80 cp, or from 80 cp to 100 cp. 
     In embodiments, the drilling fluid including the synthetic functional additives may have a yield point (at temperatures of from 77° F. to 500° F.) of from 5 lb/100 ft 2  to 100 lb/100 ft 2 , from 5 lb/100 ft 2  to 80 lb/100 ft 2 , from 5 lb/100 ft 2 to 60 lb/100 ft 2 , from 5 lb/100 ft 2 to 40 lb/100 ft 2 , from 5 lb/100 ft 2 to 20 lb/100 ft 2 , from 20 lb/100 ft 2  to 100 lb/100 ft 2 , from 20 lb/100 ft 2  to 80 lb/100 ft 2 , from 20 lb/100 ft 2  to 60 lb/100 ft 2 , from 20 lb/100 ft 2  to 40 lb/100 ft 2 , from 40 lb/100 ft 2  to 100 lb/100 ft 2 , from 40 lb/100 ft 2  to 80 lb/100 ft 2 , from 40 lb/100 ft 2  to 60 lb/100 ft 2 , from 60 lb/100 ft 2  to 100 lb/100 ft 2 , from 60 lb/100 ft 2  to 80 lb/100 ft 2 , or from 80 lb/100 ft 2  to 100 lb/100 ft 2 . 
     In embodiments, the drilling fluid including the synthetic functional additives may have a low shear yield point (at temperatures of from 77° F. to 500° F.) of from 0 lb/100 ft 2  to 105 lb/100 ft 2 , from 10 lb/100 ft 2 to 105 lb/100 ft 2 , from 10 lb/100 ft 2 to 100 lb/100 ft 2 , from 10 lb/100 ft 2 to 75 lb/100 ft 2 , from 10 lb/100 ft 2  to 50 lb/100 ft 2 , from 10 lb/100 ft 2  to 25 lb/100 ft 2 , from 25 lb/100 ft 2 to 100 lb/100 ft 2 , from 25 lb/100 ft 2 to 75 lb/100 ft 2 , from 25 lb/100 ft 2 to 50 lb/100 ft 2 , from 50 lb/100 ft 2 to 105 lb/100 ft 2 , from 50 lb/100 ft 2  to 100 lb/100 ft 2 , from 50 lb/100 ft 2 to 75 lb/100 ft 2 , from 75 lb/100 ft 2  to 105 lb/100 ft 2 , from 75 lb/100 ft 2  to 100 lb/100 ft 2 , or from 100 lb/100 ft 2 to 105 lb/100 ft 2 . 
     TEST METHODS 
     Gel Strength 
     Gel strength refers to the shear stress measured at a reduced shear rate following a defined period of time during which the material tested is maintained in a static state. The shear stress at reduced shear rate may be measured using a standard a rheometer at ambient pressure, such as a FANN® Model 35 viscometer operated at reduced rotations per minute (“rpms”), such as at 3 rpm, according to the test methods described in API Recommended Practice On Determining the Static Gel Strength (RP 10B-6/ISO 10426-6:2008). To measure the gel strength, the drilling fluid is first stirred by contacting the drilling fluid with the spindle of the viscometer and operating the viscometer at 600 rotations per minute (rpm). The viscometer is then turned off for a period of time (time period). For a 10-second gel strength the time period is 10 seconds, and for a 10-minute gel strength the time period is 10 minutes. It should be understood that other time periods for measuring gel strength may be used as reference times for measurements of gel strength. During the time period, the drilling fluid comes to rest in a static state. Upon expiration of the time period, the viscometer is turned back on at a reduced speed, such as 3 rpm for example, to generate a reduced shear rate. The viscometer reading is then taken. The gel strength of the drilling fluid is reported in units of pounds of force per 100 square feet (lbf/100 ft 2 ). 
     Rheological Properties (Plastic Viscosity, Yield Point, Low Shear Yield Point, and Apparent Viscosity) 
     The rheological properties of the drilling fluids may be modeled based on Bingham plastic flow behavior. The rheological behavior of the drilling fluids may be determined by measuring the shear stress on the composition at different shear rates, which may be accomplished by measuring the shear stress, the shear rate, or both on the samples using a FANN® couette coaxial cylinder rotational viscometers (Model 35 Rheometer and iX77 Rheometer, Fann Instrument Company) operated at 3 rpm, 6 rpm, 100 rpm, 200 rpm, 300 rpm, or 600 rpm, for example. The Model 35 Rheometer was employed to obtained rheological properties at ambient conditions, while the iX77 Rheometer was utilized to record the rheological properties at high temperatures (up to 400° F.) and high pressure (10,000 psi). These rheometers offer a simulation of the flow process conditions encountered during drilling operations. Dial deflection torque readings (600, 300, 200, 100, 6, and 3 rpm) from the rheometers were recorded for the samples before and after ageing at different temperatures. Aged samples (i.e. drilling fluid samples) were tested at high temperature and high pressure to obtain data for each sample. 
     The rheology of the drilling fluids may be evaluated from the plastic viscosity (PV) and the yield point (YP), which are parameters from the Bingham plastic rheology model. The PV is related to the resistance of the composition to flow due to mechanical interaction between the solids of the composition and represents the viscosity of the composition extrapolated to infinite shear rate. The PV of the drilling fluids may be estimated by measuring the shear stress of the drilling fluids using a viscometer at spindle speeds of 300 rotations per minute (rpm) and 600 rpm and subtracting the 300 rpm viscosity measurement from the 600 rpm viscosity measurement according to Equation 2 (EQ. 2), which is subsequently provided. The PV values determined for the drilling fluids are provided in this disclosure in units of centipoise (cP). 
     
       
         
           
             
               
                 
                   PV 
                   = 
                   
                     
                       ( 
                       
                         viscosity 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         at 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         600 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                       
                       ) 
                     
                     - 
                     
                       ( 
                       
                         viscosity 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         at 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         300 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                     . 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ) 
                 
               
             
           
         
       
     
     The yield point (YP) of the drilling fluids represents the amount of stress required to move a fluid from a static condition. The YP is determined by extrapolating the Bingham plastic rheology model to a shear rate of zero. The YP of the drilling fluid may be estimated from the PV from EQ. 2 by subtracting the PV from the shear stress measured at 300 rpm according to Equation 3 (EQ. 3), which is provided subsequently. 
     
       
         
           
             
               
                 
                   YP 
                   = 
                   
                     
                       ( 
                       
                         300 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         reading 
                       
                       ) 
                     
                     - 
                     PV 
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                     . 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ) 
                 
               
             
           
         
       
     
     The YP is expressed as a force per area, such as pounds of force per one hundred square feet (lbf/100 ft 2 ). 
     The low shear yield point (LSYP) of the drilling fluids may be measured using a standard a rheometer at ambient pressure. The LSYP of the drilling fluids may be estimated by measuring the shear stress of the drilling fluids using a FANN® Model 35 viscometer at spindle speeds of 3 rpm and 6 rpm and according to Equation 4 (EQ. 4), which is subsequently provided. The LSYP values determined for the drilling fluids are provided in this disclosure in units of pounds of force per one hundred square feet (lbf/100 ft 2 ). 
       Low Shear Yield Point (LSYP)=2*(3 rpm reading)−(6 rpm reading)   (EQ. 4)
 
     The apparent viscosity of the drilling fluids may be measured using a standard a rheometer at ambient pressure. The apparent viscosity of the drilling fluids may be estimated by measuring the shear stress of the drilling fluids using a FANN® Model 35 viscometer at spindle speeds of 600 rpm Equation 5 (EQ. 5), which is subsequently provided. The apparent viscosity values determined for the drilling fluids are provided in this disclosure in units of pounds of force per one hundred square feet (lbf/100 ft 2 ). 
     
       
         
           
             
               
                 
                   
                     Apparent 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Viscosity 
                   
                   = 
                   
                     
                       ( 
                       
                         600 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         reading 
                       
                       ) 
                     
                     / 
                     2 
                   
                 
               
               
                 
                   ( 
                   
                     EQ 
                     . 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   ) 
                 
               
             
           
         
       
     
     EXAMPLES 
     The following examples illustrate features of the present disclosure but are not intended to limit the scope of the disclosure. The following experiments compared the performance of wellbore fluids with varying inhibitor additives, some of which included examples of presently-described synthetic functionalized additives. 
     Example 1—Synthesis of Synthetic Functionalized Additives 
     In Example 1, one or more siloxanes were used. In Samples 1-1, 1-2, 1-3, and 1-4, the ratio of the two siloxanes were varied. In Example 1, the siloxanes used included aminopropyltriethoxysilane and tetraethyl orthosilicate to obtain synthetic functionalized additives with mixed functionalities. 
     Based on Samples 1-1, 1-2, 1-3, and 1-4 and Comparative Samples 1-A and 1-B, It was observed that the presence of hydroxyl groups in combination with amine functionalities may improve the hydrogen bonding in an aqueous medium. As stated previously in this disclosure, generally, an alkaline solution (NaOH) may be added to improve hydrogen bonding. In the presence of mixed functionalities, the amount of alkaline solution required to activate hydrogen bonding may be minimized. Comparative Example 1-A (—NH 2 ) and Comparative Example 1-A (—OH), subsequently described in more detail, each have only one distinct functionality. It is believed that the amine-terminated layered magnesium silicate of Comparative Example 1-A may potentially form a gel structure in alkaline condition. However, it is believed that the hydroxyl terminated layered magnesium silicate of Comparative Example 1-B is unable to form gel structure irrespective of any activators. 
     Sample 1-1 
     To produce Sample 1-1, magnesium chloride hexahydrate (9.96 g) was dissolved in 200 mL of ethanol. Subsequently, aminopropyltriethoxysilane (11.7 g) and tetraethyl orthosilicate (2.5 g) were added with stirring at room temperature (20-30° C.). 1 N NaOH solution was added until the pH reached 10-12 at room temperature with continuous stirring over a period of 1 hour. The reaction mixture was stirred at this condition for 3-4 hours, followed by refluxing for 43 hours. The reaction mixture was then cooled, filtered/centrifuged, washed with de-ionized water (100 mL, three times), and dried at 80° C. in vacuum to obtain Sample 1-1. 
     Sample 1-2 
     To produce Sample 1-2, magnesium chloride hexahydrate (9.96 g) was dissolved in 200 mL of ethanol. Subsequently, aminopropyltriethoxysilane (7.2 g) and tetraethyl orthosilicate (6.8 g) were added with stirring at room temperature (20-30° C.). 1 N NaOH solution was added until the pH reached at 10-12 at room temperature with continuous stirring over a period of 1 hour. The reaction mixture was stirred at this condition for 3-4 hours, followed by refluxing for 43 hours. The reaction mixture was then cooled, filtered/centrifuged, washed with de-ionized water (100 mL, three times), and dried at 80° C. in vacuum to obtain Sample 1-2. 
     Sample 1-3 
     To produce Sample 1-3, magnesium chloride hexahydrate (9.96 g) was dissolved in 200 mL of ethanol. Subsequently, aminopropyltriethoxysilane (9.5 g) and tetraethyl orthosilicate (4.6 g) were added with stirring at room temperature (20-30° C.). 1 N NaOH solution was added until the pH reached at 10-12 at room temperature with continuous stirring over a period of 1 hour. The reaction mixture was stirred at this condition for 3-4 hours, followed by refluxing for 43 hours. The reaction mixture was then cooled, filtered/centrifuged, washed with de-ionized water (100 mL, three times), and dried at 80° C. in vacuum to obtain Sample 1-3. 
     Sample 1-4 
     To produce Sample 1-4, magnesium chloride hexahydrate (9.96 g) was dissolved in 200 mL of ethanol. Subsequently, aminopropyltriethoxysilane (4.9 g) and tetraethyl orthosilicate (9.0 g) were added with stirring at room temperature (20-30° C.). 1 N NaOH solution was added until the pH reached at 10-12 at room temperature with continuous stirring over a period of 1 hour. The reaction mixture was stirred at this condition for 3-4 hours, followed by refluxing for 43 hours. The reaction mixture was cooled, filtered/centrifuged, washed with de-ionized water (100 mL, three times), and dried at 80° C. in vacuum to obtain Sample 1-4. 
     Comparative Sample 1-A 
     To produce Comparative Sample 1-A, magnesium chloride hexahydrate (9.96 g) was dissolved in 200 mL of ethanol. Subsequently, aminopropyltriethoxysilane (14.4 g) was added with stirring at room temperature (20-30° C.). 1 N NaOH solution was added until the pH reached at 10-12 at room temperature with continuous stirring over a period of 1 hour. The reaction mixture was stirred at this condition for 3-4 hours, followed by refluxing for 43 hours. The reaction mixture was cooled, filtered/centrifuged, washed with de-ionized water (100 mL, three times), and dried at 80° C. in vacuum to obtain Sample 1-5. 
     Comparative Sample 1-B 
     To produce Comparative Sample 1-B, magnesium chloride hexahydrate (9.96 g) was dissolved in 200 mL of ethanol. Subsequently, tetraethyl orthosilicate (13.5 g) was added with stirring at room temperature (20-30° C.). 1 N NaOH solution added until the pH reached at 10-12 at room temperature with continuous stirring over a period of 1 hour. The reaction mixture was stirred at this condition for 3-4 hours, followed by refluxing for 43 hours. The reaction mixture was cooled, filtered/centrifuged, washed with de-ionized water (100 mL, three times), and dried at 80° C. in vacuum to obtain Sample 1-6. 
     Example 2—Preparation of Drilling Fluids 
     In Example 2, drilling fluids of Comparative Sample 2-A and Samples 2-1, 2-2, 2-3, and 2-were prepared as subsequently described. 
     Comparative Sample 2-A (Without Synthetic Functionalized Additive) 
     To produce Comparative Sample 2-A (having no synthetic functionalized additive), xanthan gum (0.36 g) was solubilized in water (234 g), and the was kept at 80° C. in static condition for 5 hours. Then, the solution was cool. Barite (65.52 g) was then added to the cooled solution and shear mixed for 5 min at room temperature. Then, the mixture was hot rolled for 16 hours. The formulation of Comparative Sample 2-A, aged at 90° C. is provided in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Formulation of Comparative Sample 2-A. 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 Amount (g) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Water 
                 234 
               
               
                   
                 Xanthan Gum 
                 0.36 
               
               
                   
                 Barite 
                 65.52 
               
               
                   
                 Total 
                 299.9 
               
               
                   
                 Density 
                 10.0 lb/gal 
               
               
                   
                   
               
            
           
         
       
     
     Sample 2-1 (Including Synthetic Functionalized Additive) 
     To produce Sample 2-1,: Sample 1-1 of Example 1 previously described (4.3 g) was added to water (231 g) and shear mixed for 10 minutes. Then, sodium hydroxide (1.5 g) was added, and the mixture was shear mixed for 10 minutes. Then, xanthan gum (0.36 g) was added and shear mixed for 10 minutes. The solution was then kept at 80° C. in static condition for 5 hours and then cooled. Barite (63.6 g) was added to the cooled solution, which was then shear mixed for 5 min at room temperature and hot rolled for 16 hours. The formulation of Sample 2-1, aged at 90° C. is provided in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Formulation of Sample 2-1. 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 Amount (g) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Water 
                 231 
               
               
                   
                 Sample 1-1 
                 4.3 
               
               
                   
                 Sodium hydroxide 
                 1.5 
               
               
                   
                 Xanthan Gum 
                 0.36 
               
               
                   
                 Barite 
                 63.6 
               
               
                   
                 Total 
                 301 
               
               
                   
                 Density 
                 10.02 lb/gal 
               
               
                   
                   
               
            
           
         
       
     
     Sample 2-2 (Including Synthetic Functionalized Additive) 
     To produce Sample 2-2, Sample 1-1 of Example 1 previously described (4.3 g) was added to water (213 g) and shear mixed for 10 minutes. Then, sodium hydroxide (1.5 g) was added, and the mixture was shear mixed for 10 minutes. Then, xanthan gum (0.36 g) was added and shear mixed for 10 minutes. The solution was then kept at 80° C. in static condition for 5 hours and then cooled. Barite (142 g) was added to the cooled solution, which was then shear mixed for 5 min at room temperature and hot rolled for 16 hours. The formulation of Sample 2-2, aged at 90° C. is provided in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Formulation of Sample 2-2. 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 Amount (g) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Water 
                 213 
               
               
                   
                 Sample 1-1 
                 4.3 
               
               
                   
                 Sodium hydroxide 
                 1.5 
               
               
                   
                 Xanthan Gum 
                 0.36 
               
               
                   
                 Barite 
                 142 
               
               
                   
                 Total 
                 361 
               
               
                   
                 Density 
                 12.0 lb/gal 
               
               
                   
                   
               
            
           
         
       
     
     Sample 2-3 (Including Synthetic Functionalized Additive) 
     To produce Sample 2-3, Sample 1-1 of Example 1 previously described (4.3 g) was added to water (231 g) and shear mixed for 10 minutes. Then, sodium hydroxide (1.5 g) was added, and the mixture was shear mixed for 10 minutes. Then, xanthan gum (0.36 g) was added and shear mixed for 10 minutes. The solution was then kept at 80° C. in static condition for 5 hours and then cooled. Barite (63.6 g) was added to the cooled solution, which was then shear mixed for 5 min at room temperature. Ca-montmorillonite (Ca-MMT) (15 g) was then added and shear mixed for 5 min and hot rolled for 16 hours. The formulation of Sample 2-3, aged at 90° C. is provided in Table 5. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Formulation of Sample 2-3. 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 Amount (g) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Water 
                 231 
               
               
                   
                 Sample 1-1 
                 4.3 
               
               
                   
                 Sodium hydroxide 
                 1.5 
               
               
                   
                 Xanthan Gum 
                 0.36 
               
               
                   
                 Barite 
                 63.6 
               
               
                   
                 Ca-Montmorillonite 
                 15 
               
               
                   
                 Total 
                 316 
               
               
                   
                 Density 
                 10.25 lb/gal 
               
               
                   
                   
               
            
           
         
       
     
     Sample 2-4 (Including Synthetic Functionalized Additive) 
     To produce Sample 2-5, Sample 1-1 of Example 1 previously described (4.3 g) was added to water (213 g) and shear mixed for 10 minutes. Then, sodium hydroxide (1.5 g) was added and shear mixed for 10 minutes. Then, xanthan gum (0.36 g) was added and shear mixed for 10 minutes. The solution was kept at 80° C. in static condition for 5 hours and cooled. Barite (142 g) was added to the cooled solution, which was then shear mixed for 5 min at room temperature. Ca-montmorillonite (Ca-MMT) (15 g) was added and shear mix for 5 min and hot rolled for 16 hours. The formulation of Sample 2-4, aged at 90° C. is provided in Table 6. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Formulation of Sample 2-4. 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 Amount (g) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Water 
                 213 
               
               
                   
                 Sample 1-1 
                 4.3 
               
               
                   
                 Sodium hydroxide 
                 1.5 
               
               
                   
                 Xanthan Gum 
                 0.36 
               
               
                   
                 Barite 
                 142 
               
               
                   
                 Ca-montmorillonite 
                 15 
               
               
                   
                 Total 
                 376 
               
               
                   
                 Density 
                 12.2 lb/gal 
               
               
                   
                   
               
            
           
         
       
     
     Example 3—Analysis of Drilling Fluids 
     The drilling fluids of Comparative Sample 2-A and Samples 2-1, 2-2, 2-3, and 2- were tested utilizing a Rheometer at ambient pressure. The rheological properties measurements were performed at different temperatures ranging from 77° F. to 180° F. The rheological parameters (plastic viscosity, apparent viscosity, yield point, low shear yield point) were derived from the data collected from the rheometer according to the test methods previously provided in this disclosure. 
     To observe the effects of synthetic functionalized additives on the drilling fluids of Comparative Sample 2-A, Sample 2-1, and Sample 2-2, the gelation characteristics were analyzed. The results are provided subsequently in Table 7. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Gelation characteristics of Comparative 
               
               
                 Sample 2-A, Sample 2-1, and Sample 2-2. 
               
            
           
           
               
               
               
               
               
               
            
               
                 Sample 
                 Gel 
                 80° F. 
                 100° F. 
                 140° F. 
                 180° F. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Comparative 
                 10 
                 sec. 
                 3 
                 3 
                 2 
                 1 
               
               
                 Sample 2-A 
                 10 
                 min. 
                 4 
                 3 
                 2 
                 2 
               
               
                 Sample 2-1 
                 10 
                 sec. 
                 7 
                 6 
                 5 
                 5 
               
               
                   
                 10 
                 min. 
                 10 
                 15 
                 29 
                 26 
               
               
                 Sample 2-2 
                 10 
                 sec. 
                 8 
                 8 
                 6 
                 5 
               
               
                   
                 10 
                 min. 
                 19 
                 20 
                 23 
                 21 
               
               
                   
               
            
           
         
       
     
     As shown in Table 7, the gelation (10 sec and 10 min) of Samples 2-1 and 2-2, both having synthetic functionalized additive, was higher when compared with Comparative Sample 2-A having no synthetic functionalized additive. It was also observed that this increase in gelation with respect to rise in temperature reached an apparent plateau after 140° F. 
     To observe the effects of synthetic functionalized additives on the drilling fluids of Comparative Sample 2-A, Sample 2-1, and Sample 2-2, the rheological properties were analyzed. The results are provided subsequently in Table 8. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Comparison of the rheological properties of Formulations 
               
               
                 A, B, and C at various temperatures. 
               
            
           
           
               
               
               
               
               
               
            
               
                 Property 
                 Sample 
                 80° F. 
                 100° F. 
                 140° F. 
                 180° F. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Plastic 
                 Comparative 
                 6 
                 4 
                 3 
                 2 
               
               
                 viscosity 
                 Sample 2-A 
               
               
                 (cP) 
                 Sample 2-1 
                 19 
                 17 
                 14 
                 11 
               
               
                   
                 Sample 2-2 
                 35 
                 32 
                 22 
                 18 
               
               
                 Yield point 
                 Comparative 
                 7 
                 5 
                 4 
                 4 
               
               
                 (lb/100 ft 2 ) 
                 Sample 2-A 
               
               
                   
                 Sample 2-1 
                 21 
                 16 
                 12 
                 15 
               
               
                   
                 Sample 2-2 
                 24 
                 17 
                 12 
                 12 
               
               
                 Low Shear 
                 Comparative 
                 1 
                 0 
                 0 
                 1 
               
               
                 Yield Point 
                 Sample 2-A 
               
               
                 (lb/100 ft 2 ) 
                 Sample 2-1 
                 5 
                 2 
                 3 
                 3 
               
               
                   
                 Sample 2-2 
                 5 
                 3 
                 2 
                 2 
               
               
                   
               
            
           
         
       
     
     As shown in Table 8, the rheological properties (plastic viscosity (PV), yield point (YP), and low shear yield point (LSYP)) Samples 2-1 and 2-2, both having synthetic functionalized additive, were improved when compared with Comparative Sample 2-A having no synthetic functionalized additive. It was also observed that the PV, YP, and LSYP increased and stabilized after 140° F. 
     To observe the effects of synthetic functionalized additives on the drilling fluids that have been contaminated by formation clays or clay minerals, the rheological properties Sample 2-3 and Sample 2-4 were analyzed. Therefore, the drilling fluids of Sample 2-3 and Sample 2-4 included Ca-montmorillonite to replicate the mixing of formation in the drilling fluids. The results are provided subsequently in Table 9. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Rheological properties of Samples 2-3 and 2-4 (the effect of mixing 
               
               
                 of formation is demonstrated by adding Ca-montmorillonite). 
               
            
           
           
               
               
               
               
               
               
            
               
                 Property 
                 Sample 
                 80° F. 
                 100° F. 
                 140° F. 
                 180° F. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Plastic viscosity 
                 Sample 2-3 
                 43 
                 33 
                 15 
                 9 
               
               
                 (cP) 
                 Sample 2-4 
                 32 
                 35 
                 23 
                 13 
               
               
                 Yield point 
                 Sample 2-3 
                 35 
                 50 
                 68 
                 65 
               
               
                 (lb/100 ft 2 ) 
                 Sample 2-4 
                 66 
                 92 
                 104 
                 84 
               
               
                   
               
            
           
         
       
     
     As shown in Table 9, the rheological properties (plastic viscosity (PV) and yield point (YP)) of Samples 2-3 and 2-4, both having synthetic functionalized additive, were not adversely affected by the presence of Ca-montmorillonite. 
     Example 4—Synthesis of Synthetic Functionalized Additive Sample 4-1 
     To produce the synthetic functionalized additive Sample 4-1, magnesium chloride hexahydrate (30.0 g, 0.148 mol) was dissolved in 100 mL of de-ionized water. (3-Aminopropyl)triethoxysilane (40.06 g, 0.181 mol) and tetraethyl orthosilicate (3.12 g, 0.015 mol) were added into the solution. Under vigorous stirring, aqueous sodium hydroxide solution (11.8 g NaOH in 25 mL de-ionized water)) was slowly added through peristaltic pump at 25° C. The white suspension was refluxed at 80° C. for 48 h with continuous stirring. The resulting colloidal dispersion were placed in oven at 100° C. for 24 hours to evaporate water. The dried product was ground through high speed mixer to result into white powder, designated as Sample 4-1. 
     Example 5—Synthesis of Drilling Fluid Samples 5-1, 5-2, and 5-3 and Comparative Drilling Fluid Samples 5-A, 5-B, and 5-C 
     In Example 5, three PHPA viscosifiers, EzMud (commercially available from Halliburton), EvoVis S (commercially available from Newpark), and PolyPlus RD (commercially available from Schlumberger), were tested to analyze their compatibility with the presently-disclosed synthetic functionalized additives and demonstrate the effect of the synthetic functionalized additives loading on the overall rheological properties of drilling fluids. 
     The composition of each drilling fluid sample is provided in Table 10. To produce each composition, in the amounts provided in Table 10, water was first added to the sodium hydroxide and sheared for 2 minutes; Sample 4-1 was added and sheared for 10 minutes; the viscosifier was added and sheared for 20 minutes; barite was added and sheared for 10 minutes; and RevDust (commercially available from Milwhite, Inc.) was added and sheared for five minutes. Finally, each drilling fluid sample was hot rolled at 250° F. under 500 psi in pressure cells for 16 hours. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Compositions of Drilling Fluid Samples 5-1,5-2, and 5-3 
               
               
                 and Comparative Drilling Fluid Samples 5-A, 5-B, and 5-C. 
               
            
           
           
               
               
            
               
                   
                 Component (lb/bbl for 350 cc) 
               
            
           
           
               
               
               
               
               
               
            
               
                 Sample 
                 Water 
                 NaOH 
                 Sample 4-1 
                 PHPA 
                 Barite 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Comparative Drilling Fluid 
                 323 
                 2 
                 — 
                 8 (EzMud) 
                 89.5 
               
               
                 Sample 5-A 
               
               
                 Comparative Drilling Fluid 
                 323 
                 2 
                 — 
                 4 (EvoVis S) 
                 89.5 
               
               
                 Sample 5-B 
               
               
                 Comparative Drilling Fluid 
                 323 
                 2 
                 — 
                 4 (PolyPlus RD) 
                 89.5 
               
               
                 Sample 5-C 
               
               
                 Comparative Drilling Fluid 
                 323 
                 2 
                 — 
                 4 (PolyPlus RD) 
                 — 
               
               
                 Sample 5-D 
               
               
                 Drilling Fluid Sample 5-1 
                 323 
                 2 
                 4 
                 8 (EzMud) 
                 89.5 
               
               
                 Drilling Fluid Sample 5-2 
                 323 
                 2 
                 4 
                 4 (EvoVis S) 
                 89.5 
               
               
                 Drilling Fluid Sample 5-3 
                 323 
                 2 
                 4 
                 4 (PolyPlus RD) 
                 89.5 
               
               
                 Drilling Fluid Sample 5-4 
                 323 
                 2 
                 4 
                 4 (PolyPlus RD) 
                 — 
               
               
                   
               
            
           
         
       
     
     Example 6—Analysis of Drilling Fluid Samples 5-1, 5-2, and 5-3 and Comparative Drilling Fluid Samples 5-A, 5-B, and 5-C 
     In Example 6, the rheological properties of Drilling Fluid Samples 5-1, 5-2, and 5-3 and Comparative Drilling Fluid Samples 5-A, 5-B, and 5-C were aged at 250° F. (121° C.). PHPA has been known to degrade above 200° F.; thus, 250° F. was chosen to analyze the effect of the synergy between the synthetic functionalized additives and PHPA in each drilling fluid sample. To test the rheological properties of the samples, the rheological properties of Drilling Fluid Samples 5-1, 5-2, and 5-3 and Comparative Drilling Fluid Samples 5-A, 5-B, and 5-C were recorded after aging using FANN® Model 35 viscometer at 120° F. according to the presently- disclosed test methods. The results are provided subsequently in Table 11. 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Rheological properties of Drilling Fluid Samples 5-1, 5-2, and 5-3 and Comparative 
               
               
                 Drilling Fluid Samples 5-A, 5-B, and 5-C at 120° F. after aging at 250° F. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Comp. 
                   
                 Comp. 
                   
                 Comp. 
                   
               
               
                   
                 Drilling 
                 Drilling 
                 Drilling 
                 Drilling 
                 Drilling 
                 Drilling 
               
               
                   
                 Fluid 
                 Fluid 
                 Fluid 
                 Fluid 
                 Fluid 
                 Fluid 
               
               
                   
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
               
               
                 RPM 
                 5-A 
                 5-1 
                 5-B 
                 5-2 
                 5-C 
                 5-3 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 600 
                 37 
                 125 
                 43 
                 90 
                 35 
                 154 
               
               
                 300 
                 20 
                 83 
                 21 
                 56 
                 18 
                 111 
               
               
                 200 
                 14 
                 64 
                 15 
                 41 
                 13 
                 90 
               
               
                 100 
                 8 
                 41 
                 9 
                 24 
                 8 
                 63 
               
               
                 6 
                 2 
                 9 
                 1 
                 3 
                 1 
                 16 
               
               
                 3 
                 1 
                 7 
                 1 
                 2 
                 1 
                 14 
               
               
                 10 sec (3 RPM) 
                 2 
                 9 
                 2 
                 4 
                 3 
                 16 
               
               
                 10 min (3 RPM) 
                 4 
                 11 
                 2 
                 4 
                 6 
                 22 
               
               
                 PV, cP 
                 17 
                 42 
                 22 
                 34 
                 17 
                 43 
               
               
                 AV, cP 
                 18.5 
                 62.5 
                 21.5 
                 45 
                 17.5 
                 77 
               
               
                 YP, lb/100 ft 2   
                 3 
                 41 
                 — 
                 22 
                 1 
                 68 
               
               
                   
               
            
           
         
       
     
     Based on the results of Table 11, it was observed that Samples 5-1, 5-2, and 5-3 comprising PHPA exhibited higher measured rheological values with the addition of Sample 4-1. Without being bound by theory, it is believed that the results may show synergy associated with formation of hydrogen bond networks between PHPA and the synthetic functionalized additives. Additionally, the results of Table 11 show that Comparative Drilling Fluid Samples 5-A, 5-B, and 5-C comprising PHPA without Sample 4-1 exhibited lesser rheological properties (i.e. viscosity), which evidenced the degradation and instability of these comparative drilling fluids at temperatures above 200° F. In particular, Drilling Fluid Sample 5-3 exhibited significantly higher rheological rheological properties when compared to Comparative Drilling Fluid Sample 5-C, which may correspond to the interaction of the synthetic functionalized additives with the functionalities of acrylamide groups of PHPA. 
     Drilling Fluid Sample 3 and Comparative Drilling Fluid Sample C were also hot rolled at 150° F. for 16 hours to establish the changes in rheology at different temperatures (78° F., 120° F., 140° F.) at ambient pressure and these are measured using a FANN® Model 35 viscometer. The results are provided subsequently in Table 12. 
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 Rheological properties of Drilling Fluid Sample 5-3 and Comparative Drilling 
               
               
                 Fluid Sample 5-C at 78° F., 120° F., and 140° F. after aging at 150° F. 
               
            
           
           
               
               
               
            
               
                   
                 Comp. Drilling Fluid Sample 5-C 
                 Drilling Fluid Sample 5-3 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 RPM 
                 78° F. 
                 120° F. 
                 140° F. 
                 78° F. 
                 120° F. 
                 140° F. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 600 
                 139 
                 125 
                 112 
                 135 
                 120 
                 110 
               
               
                 300 
                 105 
                 96 
                 88 
                 100 
                 92 
                 85 
               
               
                 200 
                 90 
                 83 
                 75 
                 85 
                 79 
                 73 
               
               
                 100 
                 70 
                 66 
                 61 
                 67 
                 63 
                 59 
               
               
                 6 
                 28 
                 26 
                 24 
                 30 
                 30 
                 27 
               
               
                 3 
                 22 
                 20 
                 18 
                 25 
                 24 
                 22 
               
               
                 10 sec 
                 22 
                 21 
                 18 
                 25 
                 25 
                 22 
               
               
                 10 min 
                 24 
                 21 
                 19 
                 27 
                 25 
                 22 
               
               
                 PV, cP 
                 34 
                 29 
                 24 
                 35 
                 28 
                 23 
               
               
                 AV, cP 
                 69.5 
                 62.5 
                 56 
                 67.5 
                 60 
                 55 
               
               
                 YP, lb/100 ft 2   
                 71 
                 67 
                 64 
                 65 
                 64 
                 62 
               
               
                 LSYP, lb/100 ft 2   
                 16 
                 14 
                 12 
                 20 
                 18 
                 17 
               
               
                   
               
            
           
         
       
     
     From the results of Table 12, it was observed that Samples 5-3 comprising PHPA and the synthetic functionalized additive exhibited higher measured rheological values than Comparative Sample 5-C after aging at 150° F. Without being bound by theory, it is believed that these results show that upon addition of the synthetic functionalized additive (Sample 4-1) formation of hydrogen bond networks between PHPA and the synthetic functionalized additive allow for improved properties under low shear rate, for example, as evidenced by the LSYP of Drilling Fluid Sample 5-3 (17 lb/100 ft 2 ) compared to the LSYP of Comparative Drilling Fluid Sample 5-C (12 lb/100 ft 2 ) at 140° F. 
     Drilling Fluid Sample 5-4 and Comparative Drilling Fluid Sample 5-D (which did not include barite) were also hot rolled at 250° F. for 16 hours to establish the changes in rheology at different temperatures (78° F., 120° F., 140° F.) at ambient pressure and these are measured using a FANN® Model 35 viscometer. The results are provided subsequently in Table 13. 
     
       
         
           
               
             
               
                 TABLE 13 
               
             
            
               
                   
               
               
                 Rheological properties of Drilling Fluid Sample 5-4 and Comparative Drilling 
               
               
                 Fluid Sample 5-D at 78° F., 120° F., and 140° F. after aging at 250° F. 
               
            
           
           
               
               
               
            
               
                   
                 Comp. Drilling Fluid Sample 5-D 
                 Drilling Fluid Sample 5-4 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 RPM 
                 78° F. 
                 120° F. 
                 140° F. 
                 78° F. 
                 120° F. 
                 140° F. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 600 
                 29 
                 22 
                 17 
                 63 
                 46 
                 38 
               
               
                 300 
                 16 
                 12 
                 9 
                 36 
                 26 
                 21 
               
               
                 200 
                 11 
                 7 
                 6 
                 26 
                 19 
                 15 
               
               
                 100 
                 6 
                 4 
                 3 
                 15 
                 10 
                 8 
               
               
                 6 
                 1 
                 0 
                 0 
                 4 
                 2 
                 2 
               
               
                 3 
                 1 
                 0 
                 0 
                 3 
                 2 
                 2 
               
               
                 10 sec 
                 2 
                 0 
                 0 
                 3 
                 3 
                 3 
               
               
                 10 min 
                 2 
                 0 
                 0 
                 3 
                 3 
                 3 
               
               
                 PV, cP 
                 13 
                 10 
                 8 
                 27 
                 20 
                 17 
               
               
                 AV, cP 
                 14.5 
                 11 
                 8.5 
                 31.5 
                 23 
                 19 
               
               
                 YP, lb/100 ft 2   
                 3 
                 2 
                 1 
                 9 
                 6 
                 4 
               
               
                 LSYP, lb/100 ft 2   
                 1 
                 0 
                 0 
                 2 
                 2 
                 2 
               
               
                   
               
            
           
         
       
     
     From the results of Table 13, it was observed that Samples 5-4 comprising PHPA and the synthetic functionalized additive exhibited higher measured rheological values than Comparative Sample 5-D after aging at 250° F. 
     Drilling Fluid Sample 3 and Comparative Drilling Fluid Sample C were also hot rolled at 150° F. for 16 hours to establish the changes in rheology at different temperatures (150° F., 200° F., 250° F., 275° F., 300° F., 350° F., and 400° F.) at 10,000 psi and these are measured using a FANN® Model 77 viscometer. The results are provided subsequently in Tables 14 and 15. 
     
       
         
           
               
             
               
                 TABLE 14 
               
             
            
               
                   
               
               
                 Rheological properties of Comparative Drilling Fluid Sample 
               
               
                 5-C at 150° F., 200 ° F., 250° F., 275° 
               
               
                 F., 300° F., 350° F., and 400° F. at 10,000 psi after aging at 150° F. 
               
            
           
           
               
               
            
               
                   
                 Comp. Drilling Fluid Sample 5-C 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 RPM 
                 150° F. 
                 200° F. 
                 250° F. 
                 275° F. 
                 300° F. 
                 350° F. 
                 400° F. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 600 
                 110.7 
                 94.9 
                 83.3 
                 73.5 
                 68.6 
                 56.6 
                 36.6 
               
               
                 300 
                 84.0 
                 72.9 
                 62.3 
                 51.0 
                 46.2 
                 36.3 
                 19.2 
               
               
                 200 
                 71.3 
                 62.5 
                 51.2 
                 41.2 
                 37.2 
                 28.0 
                 13.7 
               
               
                 100 
                 55.9 
                 49.1 
                 37.3 
                 27.7 
                 24.7 
                 17.7 
                 8.8 
               
               
                 6 
                 21.2 
                 16.1 
                 7.9 
                 5.4 
                 5.1 
                 4.6 
                 3.5 
               
               
                 3 
                 15.5 
                 11.3 
                 5.6 
                 4.3 
                 4.2 
                 3.9 
                 3.2 
               
               
                 PV, cP 
                 26.7 
                 22.0 
                 21.1 
                 22.5 
                 22.4 
                 20.4 
                 17.4 
               
               
                 AV, cP 
                 55.3 
                 47.4 
                 41.7 
                 36.7 
                 34.3 
                 28.3 
                 18.3 
               
               
                 YP, lb/100 ft 2   
                 57.2 
                 50.8 
                 41.2 
                 28.5 
                 23.9 
                 15.9 
                 1.9 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 15 
               
             
            
               
                   
               
               
                 Rheological properties of Drilling Fluid Sample 5-3 at 150° F., 200° 
               
               
                 F., 250° F., 275 ° F., 300° F., 350° F., and 400° F. at 10,000 psi after aging at 150° F. 
               
            
           
           
               
               
            
               
                   
                 Drilling Fluid Sample 5-3 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 RPM 
                 150° F. 
                 200° F. 
                 250° F. 
                 275° F. 
                 300° F. 
                 350° F. 
                 400° F. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 600 
                 116.2 
                 99.6 
                 88.4 
                 81.9 
                 75.9 
                 66.2 
                 56.6 
               
               
                 300 
                 87.8 
                 76.5 
                 67.3 
                 60.8 
                 57.8 
                 49.6 
                 40.6 
               
               
                 200 
                 74.7 
                 64.8 
                 56.9 
                 51.7 
                 48.4 
                 41.8 
                 34.0 
               
               
                 100 
                 59.5 
                 51.9 
                 45.4 
                 41.3 
                 37.9 
                 31.8 
                 25.4 
               
               
                 6 
                 27.9 
                 23.3 
                 17.2 
                 13.5 
                 11.3 
                 8.1 
                 7.0 
               
               
                 3 
                 23.1 
                 18.4 
                 12.6 
                 9.6 
                 8.1 
                 5.9 
                 5.6 
               
               
                 PV, cP 
                 28.5 
                 23.1 
                 21.1 
                 21.0 
                 18.1 
                 16.6 
                 15.9 
               
               
                 AV, cP 
                 58.1 
                 49.8 
                 44.2 
                 40.9 
                 38.0 
                 33.1 
                 28.3 
               
               
                 YP, lb/100 ft 2   
                 59.3 
                 53.5 
                 46.1 
                 39.8 
                 39.6 
                 33.0 
                 24.7 
               
               
                   
               
            
           
         
       
     
     The results of Tables 14 and 15 show that Comparative Drilling Fluid Sample 5-C and Drilling Fluid Sample 5-3 show almost similar PV, however, a decline in PV was observed at higher temperatures. Without being bound by theory, it is believed that the stability of Drilling Fluid Sample 5-3 may allow for improved penetration of the drilling fluid under downhole conditions. Also, the AV of Drilling Fluid Sample 5-3 appeared to be stable than Comparative Drilling Fluid Sample 5-C, which may be attributed to entanglement of colloidal platelets of the synthetic functionalized additives within the matrix of PHPA through hydrogen bonds. The results of Tables 14 and 15 further show a major difference in YP when Comparative Drilling Fluid Sample 5-C and Drilling Fluid Sample 5-3 were subjected to simulated downhole conditions. A steady decline in the YP for Comparative Drilling Fluid Sample 5-C was observed, which may indicate instability of PHPA at increased temperatures. The decrease in the YP may directly affect the suspension properties of the drilling fluid. For example, a sagging of weighing materials could arise on account of drop in YP, which could result issues with stuck pipes and increases in the non-productive time. The YP of Comparative Drilling Fluid Sample 5-C fell considerably at temperatures above 275° F. Comparatively, Drilling Fluid Sample 5-3 appeared to preserve the YP up to 400° F. Furthermore, the the low shear stability of the drilling fluids described herein may provide competence of fluid system stability in the presence of highly dense particles and suspended drill cutting. The results of Tables 14 and 15 show that Drilling Fluid Sample 5-3 showed higher low shear dialing reading (3 rpm and 6 rpm) throughout the temperature ranges when compared with Comparative Drilling Fluid Sample 5-C. 
     It will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.