Abstract:
Disclosed is a method for modifying bentonite to allow the bentonite to be useful in drilling mud applications. The method includes the steps of: preparing bentonite local to Saudi Arabia using raw water to remove contaminants from the bentonite; grinding the bentonite to a fine powder; sieving the fine powder to be between about 50 μm and about 150 μm in particle size to produce a sieved fine powder; mixing the sieved fine powder with polyanionic cellulose polymer to produce a modified bentonite composition; adding the modified bentonite composition to water until a homogeneous solution of modified bentonite in water is formed; and allowing the homogeneous solution of modified bentonite in water to rest for about 16 hours to form a composition useful in drilling mud applications.

Description:
BACKGROUND 
     Field 
       [0001]    Embodiments of the disclosure relate to compositions for use in drilling fluids for hydrocarbon-bearing reservoirs. In particular, embodiments of the disclosure relate to drilling fluid compositions comprising modified bentonite. 
       Description of the Related Art 
       [0002]    In hydrocarbon-bearing reservoirs, wellbores contain wellbore fluid from the first moment of formation until completion and production. Wellbore fluid serves several purposes, including well control (hydraulic pressure against the fluids in the hydrocarbon-bearing formation), wellbore wall integrity (hydraulic pressure on the wellbore wall and providing loss control additives) and lubricity (operating machinery). Wellbore fluid is in fluid contact with all portions of and everything in the wellbore not fluidly isolated, including tubulars internal to the fluid conduit, the wellbore annulus, and the wellbore wall. Other fluid conduits coupled to the wellbore often contain at least some wellbore fluid. 
         [0003]    While drilling, drilling fluid (also referred to as drilling mud) fills the interior of the wellbore as the wellbore fluid. Some muds are petroleum-based materials and some are water-based materials. Petroleum-based materials comprise at least 90 weight percent of an oil-based mud (OBM). Examples of suitable base petroleum materials include crude oils, distilled fractions of crude oil, including diesel oil, kerosene and mineral oil, and heavy petroleum refinery liquid residues. A minor part of the OBM is typically water or an aqueous solution that resides internally in the continuous petroleum phase. Other OBM components can include emulsifiers, wetting agents and other additives that give desirable physical properties. 
         [0004]    Oil-based muds also include synthetic oil-based muds (SOBMs). Synthetic oil-based muds are crude oil derivatives that have been chemically treated, altered or refined to enhance certain chemical or physical properties. In comparison to a crude temperature fraction of a partially-refined crude oil, which may contain several classes (for example, alkane, aromatic, sulfur-bearing, nitrogen-bearing) of thousands of individual compounds, a SOBM can comprise one class with only tens of individual compounds (for example, esters compounds in a C8-14 range). Examples of materials used as base fluids for SOBMs include linear alpha olefins, isomerized olefins, poly alpha olefins, linear alkyl benzenes and vegetable and hydrocarbon-derived ester compounds. SOBMs are monolithic systems that behave in a manner as if they were an oil-based mud but provide a more narrow and predictable range of chemical and physical behaviors. 
         [0005]    While performing drilling operations, wellbore fluid circulates between the surface and the wellbore interior through fluid conduits. Wellbore fluid also circulates around the interior of the wellbore. The introduction of drilling fluid into the wellbore through a first fluid conduit at pressure induces the motivation for the fluid flow in the wellbore fluid. Displacing wellbore fluid through a second fluid conduit connected to the surface causes wellbore fluid circulation from the first fluid conduit to the second fluid conduit in the interior of the wellbore. The expected amount of wellbore fluid displaced and returned to the surface through the second fluid conduit is equivalent to the amount introduced into the wellbore through the first fluid conduit. Parts of the wellbore that are fluidly isolated do not support circulation. 
         [0006]    Drilling muds that are not water based tend to dehydrate and lose additives during drilling operations. Dehydrated and additive-poor residues can collect in lower-flow velocity parts as solids, gels and highly viscous fluids. “Filter cake” is a layer of deposited solids and gelled drilling fluid that adheres to the interior surfaces of the wellbore, including the wellbore wall and the exterior of the fluid conduit. Drilling muds of appropriate density, viscosity, and other properties are required for the beneficial drilling of wellbores in hydrocarbon-bearing reservoirs. 
         [0007]    Bentonite clay is a major component in drilling fluid and any drilling fluid must have certain properties that facilitate safe and satisfactory completion of a well. Consumption of bentonite clay in drilling operations in Saudi Arabia alone can reach over 100 thousand tons per year, and substantially all of the bentonite is imported from outside of the country. 
       SUMMARY 
       [0008]    The disclosure presents modified bentonite compositions, which in some embodiments meet the American Petroleum Institute&#39;s (API&#39;s) specifications for drilling mud. The modifications can include both physical and chemical treatments with the use of one or more polymers to achieve certain API specifications. Modified bentonite can be used as a drilling mud additive according to the disclosure presented as follows. A local bentonite outcrop (bentonite local to Saudi Arabia, particularly in the Khulais area, 70 kilometers north of Jeddah and adjacent to Makkah-Madinah road) was modified in-house to meet the American Petroleum Institute (API)&#39;s specifications for drilling mud. The modification includes both physical and chemical treatments with the use of PAC™-R polymer to achieve API specifications. The modified bentonite can now be used as a drilling mud additive according to the collected analysis data. 
         [0009]    The properties of local bentonite can be improved economically by adding materials to prepared drilling muds to enhance viscosity and filtration loss, including materials such as carboxymethyl cellulose (CMC), DRISPAC® polymer (a multifunctional polyanionic cellulose polymer), and bentonite extenders. Also, shearing speed can be used as an enhancement method to improve the dispersion rate of clay suspensions, and hence increase viscosity and decrease filtration loss. A bentonite extender can be either a salt or a polymer, and it enhances viscosity buildup by slightly flocculating the bentonite suspension. 
         [0010]    Therefore as disclosed, embodiments include a method for modifying bentonite to allow the bentonite to be useful in drilling mud applications. The method includes the steps of preparing bentonite local to Saudi Arabia using raw water to remove contaminants from the bentonite; grinding the bentonite to a fine powder; sieving the fine powder to be between about 50 μm and about 150 μm in particle size to produce a sieved fine powder; mixing the sieved fine powder with polyanionic cellulose polymer to produce a modified bentonite composition; adding the modified bentonite composition to water until a homogeneous solution of modified bentonite in water is formed; and allowing the homogeneous solution of modified bentonite in water to sit at rest to form a composition useful in drilling mud applications. 
         [0011]    In some embodiments, the homogeneous solution of modified bentonite in water is formed in about 20 minutes. In other embodiments, the composition useful in drilling mud applications substantially meets the American Petroleum Institute&#39;s (API&#39;s) requirements for drilling mud. Still in other embodiments, the bentonite local to Saudi Arabia is a sodium-type bentonite and no hydroxide compositions are used in the method for modifying bentonite. 
         [0012]    In some other embodiments, the bentonite local to Saudi Arabia comprises by weight percent about 58% sodium montmorillonite, about 5% feldspar, about 25% SiO 2 , about 8% kaolinite, about 2% halite, and about 2% illite. In certain embodiments, the modified bentonite composition comprises by weight percent about 71% sodium montmorillonite, about 5% feldspar, about 15% SiO 2 , about 6% kaolinite, about 0% halite, and about 1% illite. 
         [0013]    Still in other embodiments, the method includes the step of verifying that viscosity of the homogeneous solution of modified bentonite in water substantially meets the API&#39;s requirements for viscosity of drilling mud. In other embodiments, the method includes the step of mixing the sieved fine powder with low viscosity sodium carboxymethyl cellulose. In some embodiments, the modified bentonite composition comprises between about 3% and about 11% polyanionic cellulose polymer by weight. Still in other embodiments, the modified bentonite composition comprises between about 4% and about 10% polyanionic cellulose polymer by weight. In yet other embodiments, the modified bentonite composition comprises between about 4% and about 9% polyanionic cellulose polymer by weight. In certain embodiments, the modified bentonite composition comprises between about 5% and about 8% polyanionic cellulose polymer by weight. 
         [0014]    Still in yet other embodiments, the modified bentonite composition comprises about 8.5% polyanionic cellulose polymer by weight. In some embodiments, the polyanionic cellulose polymer comprises at least a first polyanionic cellulose polymer and a second polyanionic cellulose polymer. Some embodiments of the method include the step of conducting x-ray powder diffraction (XRD) to verify that the composition useful in drilling mud applications substantially meets the API requirements for drilling mud. In certain embodiments, the method includes the step of applying the composition useful in drilling mud applications to a wellbore hydrocarbon recovery operation. 
         [0015]    Still in yet other embodiments of the method, the step of allowing the homogeneous solution of modified bentonite in water to sit at rest to form a composition useful in drilling mud applications continues for about 16 hours. 
         [0016]    Additionally disclosed is a modified bentonite composition useful in drilling mud applications, the composition comprising: a powdery mixture composition comprising: about 90% by weight bentonite local to Saudi Arabia, the bentonite existing as a fine powder, the fine powder to be between about 50 μm and about 150 μm in particle size, and about 10% by weight polyanionic cellulose polymer; and water. 
         [0017]    In some embodiments, the powdery mixture composition comprises by weight percent about 71% sodium montmorillonite, about 5% feldspar, about 15% SiO 2 , about 6% kaolinite, about 0% halite, and about 1% illite. Still in other embodiments, the modified bentonite composition substantially meets the API&#39;s requirements for drilling mud. In yet other embodiments, the composition comprises soda ash. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following descriptions, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the disclosure and are therefore not to be considered limiting of the disclosure&#39;s scope as it can admit to other equally effective embodiments. 
           [0019]      FIG. 1  shows a process diagram for one embodiment of a method to modify non-American Petroleum Institute (API) bentonite into a composition suitable for a drilling mud according to API standards. 
           [0020]      FIG. 2  shows a diffractogram comparing the compositions of a sample of API bentonite, a sample of non-API bentonite (“Untreated Bentonite”), and a sample of modified non-API bentonite (“Treated Bentonite”). 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    So that the manner in which the features and advantages of the embodiments of compositions of and methods for making modified non-API bentonite, as well as others, which will become apparent, may be understood in more detail, a more particular description of the embodiments of the present disclosure briefly summarized previously may be had by reference to the embodiments thereof, which are illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various embodiments of the disclosure and are therefore not to be considered limiting of the present disclosure&#39;s scope, as it may include other effective embodiments as well. 
         [0022]    Bentonite is an absorbent aluminum phyllosilicate, essentially impure clay consisting mostly of montmorillonite. Montmorillonite is the most abundant of the smectite clay minerals. A good quality bentonite contains mainly smectites (montmorillonite) and secondary minerals such as quartz, calcite, and micas. Bentonites come about in numerous forms on the market. In industry, montmorillonites are generally classified as sodium (Na), or calcium (Ca) types, depending on which exchangeable ion is dominant. Bentonite has certain characteristics such as negative electric charge, fine size, and very high specific surface area, and high sensitivity to hydration. Bentonite&#39;s functions in drilling mud include the control of the flow properties and the filtration rate of drilling fluids in drilling operations, which are important aspects of drilling fluid technology. 
         [0023]    Desirable rheological properties include a high shear thinning viscosity. In other words, the higher the shear rate, the lower the viscosity, and there is a relatively high gel strength with a high ratio of yield point to plastic viscosity for cuttings transport and suspension. 
         [0024]    Referring now to  FIG. 1 , a process diagram is shown for one embodiment of a method to modify non-American Petroleum Institute (API) bentonite into a composition suitable for a drilling mud according to API standards. In process  100 , unmodified bentonite, local to Saudi Arabia and not meeting API standards for use in drilling mud, was cleaned and rinsed with raw water to remove contaminants at step  102 . At step  104 , the cleaned and rinsed unmodified bentonite was ground to a very fine powder using a Mortar Grinder RM  200  by Retsch®. At step  106 , the ground unmodified bentonite was sieved to about 75 μm (200 mesh) particle size using an electronic sieve shaker column. At step  108 , the sieved unmodified bentonite was mixed with polyanionic cellulose polymer (PAC™-R) at a weight ratio of about 91.5% by weight unmodified bentonite to about 8.5% by weight PAC™-R polymer. 
         [0025]    Bentonite ore is normally accompanied by other mineral materials which vary in amount and composition according to the location at which the bentonite is mined or quarried. Some common impurities in bentonite, to be removed by water, are clay-sized silica, gypsum, illite, and non-crystalline compounds. 
         [0026]    PAC™-R polymer is a product of Halliburton and is a modified natural polyanionic cellulosic polymer that is a white, free-flowing powder. PAC™-R polymer is composed largely of carboxymethylcellulose sodium salt. While the specification and examples discuss the use of PAC™-R polymer, one of ordinary skill in the art would understand other suitable polymers could be used in the embodiments of the present disclosure, either in addition to or alternative to PAC™-R polymer. At step  110 , the mixture of sieved unmodified bentonite and PAC™-R polymer (the mixture also being referred to as “modified bentonite” throughout) was added to distilled water and mixed until the solution became homogeneous, after about 20 minutes. At step  112 , the modified bentonite in water (an example drilling solution) was covered and stored overnight for about 16 hours. 
         [0027]    At step  114 , the modified bentonite was analyzed according to API specifications for bentonite drilling mud. The analysis shows that the modified bentonite is similar to the commercially available bentonite. 
         [0028]    Table 1 compares certain properties of bentonite that meets the American Petroleum Institute&#39;s standards for making drilling mud with modified “local bentonite” or bentonite local to Saudi Arabia that has been modified with PAC™-R polymer. In some embodiments of the present disclosure, because bentonite local to Saudi Arabia is a sodium-type bentonite, no sodium hydroxide is used or required for modifying the bentonite. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Physical properties of modified bentonite local to Saudi Arabia  
               
               
                 versus commercially available bentonite. 
               
             
          
           
               
                   
                 API Bentonite VS. Modified Local Bentonite 
               
             
          
           
               
                   
                   
                   
                   
                 Yield 
                   
                   
               
               
                   
                   
                   
                   
                 Point 
                   
                   
               
               
                   
                 Viscosity 
                   
                 Plastic 
                 (YP) 
                   
                 dispersed 
               
               
                   
                 centipoise  
                   
                 Viscosity 
                 (lbs./ 
                 b  
                 Plastic 
               
               
                   
                 (cp) 
                   
                 (PV) 
                 100 
                 ratio 
                 Viscosity 
               
             
          
           
               
                   
                 600 
                 300 
                 pH 
                 (cp) 
                 ft. 2 ) 
                 YP:PV 
                 (cp) 
               
               
                   
               
             
          
           
               
                 API  
                 71 
                 43.5 
                 7.6 
                 27.5 
                 16 
                 0.58 
                 25 
               
               
                 bentonite 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Local  
                 68.5 
                 44 
                 8.4 
                 24.5 
                 19.5 
                 0.79 
                 25 
               
               
                 bentonite 
               
               
                   
               
             
          
         
       
     
         [0029]    Table 2 provides x-ray powder diffraction (XRD) data comparing the compositions of unmodified bentonite local to Saudi Arabia and modified bentonite (using PAC™-R polymer) local to Saudi Arabia. XRD is an analysis technique used for clay minerals identification. For the unmodified sample, after the preliminary removal of sand, clay was separated from silt by using a centrifugation technique. XRD patterns were obtained for air-dried samples and for samples treated with ethylene glycol vapor or heated to 350° C. and 550° C. Diffraction patterns were compared with standards for identification of minerals. 
         [0030]    Samples of API bentonite, non-API bentonite, and modified non-API bentonite were analyzed by XRD. The samples were crushed to fine powder by grinding in a McCrone Micronizing mill. The samples were identified by the three major peaks of individual compounds shown in Table 2 below and in  FIG. 2 . The quantification of the identified compounds was performed by using the area under each of the major peaks. A sample of bentonite containing known concentration of components was analyzed to calculate the concentration by area of the peaks, because the areas corresponded to actual known values. Then, the non-API bentonite sample and modified non-API bentonite sample were tested. Component concentrations were calculated by area of the peaks. The sodium montmorillonite peak was modified and the area under the peak was increased for the modified non-API bentonite (“Treated Bentonite” in  FIG. 2 ). The quartz concentration was reduced for the modified non-API bentonite sample. The feldspar concentration was largely unaffected, and clay minerals were also largely unaffected. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 XRD data comparing the compositions of unmodified 
               
               
                 bentonite local to Saudi Arabia and modified bentonite 
               
               
                 (using PAC ™-R polymer) local to Saudi Arabia. 
               
             
          
           
               
                   
                   
                   
                 Modified 
               
               
                   
                 API 
                   
                 (Treated) 
               
               
                   
                 Bentonite 
                 Untreated non-API 
                 Bentonite 
               
               
                 Phase Identified 
                 Weight % 
                 Bentonite Weight % 
                 Weight % 
               
               
                   
               
               
                 Na Montmorillonite 
                 74  
                 58  
                 71  
               
               
                 Cristoballite-SiO 2   
                 16  
                 n/a 
                 n/a 
               
               
                 Feldspar 
                 8 
                 5 
                 5 
               
               
                 Quartz-SiO 2   
                 2 
                 25  
                 15  
               
               
                 Kaolinite-Al 2 Si 2 O 5 (OH) 4   
                 n/a 
                 8 
                 6 
               
               
                 Halite-NaCl 
                 n/a 
                 2 
                 0 
               
               
                 Illite 
                 2 
                 2 
                 1 
               
               
                   
               
             
          
         
       
     
         [0031]    The identification of the crystalline mineral phases was achieved using X′Pert HighScore software by PANalytical. Semi-quantification of XRD data was performed by using JADE software by MDI Products based on the area of the peaks. The relative approximate values of the crystalline phases are listed in Table 2. 
         [0032]      FIG. 2  shows a diffractogram comparing the compositions of a sample of API bentonite, a sample of non-API bentonite, and a sample of modified non-API bentonite. Table 3 shows a comparison of data for five unmodified bentonite samples, local to Saudi Arabia (collected at different locations and different depths), and their properties. As shown, many of the properties do not meet required specifications, such as yield, dispersed plastic viscosity, dispersed filtrate, the methylene blue test, and the residue on 100 mesh (dry). 
         [0033]    There were four main tests that were carried out to determine the rheological properties of the bentonite according to the API specifications. For the yield point:plastic viscosity ratio, the viscosity of samples at 600 rpm and 300 rpm were measured by using the Fan Viscometer device. After measuring the viscosity, the yield point:plastic viscosity ratio was calculated. The pH value of the samples were tested. To test dispersed plastic viscosity, sodium hexametaphosphate (10 wt. %) was prepared and 5 μl was added to the modified non-API bentonite. After that, the viscosity at 600 rpm and 300 rpm were measured again. The dispersed plastic viscosity is calculated by taking the difference between the viscosity at 600 rpm and the viscosity at 300 rpm. 
         [0034]    To measure dispersed filtrate volume, the sample was pressurized by nitrogen gas to about 100 psi. The filtered water coming out of the pressurized cell was collected after 7.5 minutes of the starting of the nitrogen pressure until 30 minutes had elapsed. Finally, the volume of the water was multiplied by 2 to calculate the filtrate volume. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Properties of five unmodified non-API bentonite samples. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Internal 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Required 
               
               
                 Tests 
                 Unit 
                 # 1 
                 # 2 
                 # 3 
                 # 4 
                 # 5 
                 Mean 
                 Specs. 
               
               
                   
               
             
          
           
               
                 Yield 
                 Barrel/ 
                 27.59 
                 37.24 
                 27.59 
                 26.95 
                 27.59 
                 29.39 
                 Minimum 
               
               
                   
                 Short Ton 
                   
                   
                   
                   
                   
                   
                 90.0 
               
               
                 Moisture 
                 % by wt. 
                 9.0 
                 8.6 
                 8.6 
                 9.1 
                 8.3 
                 8.72 
                 Maximum 
               
               
                 Content 
                   
                   
                   
                   
                   
                   
                   
                 13.0 
               
               
                 Ratio of Yield 
                   
                 −0.50 
                 0.0 
                 0.0 
                 0.0 
                 −3.0 
                 -0.70 
                 Maximum 
               
               
                 Point:Plastic 
                   
                   
                   
                   
                   
                   
                   
                 1.50 
               
               
                 Viscosity (b) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Dispersed 
                 Centipoise 
                 1.0 
                 1.0 
                 1.0 
                 1.0 
                 1.0 
                 1.0 
                 Minimum 
               
               
                 Plastic 
                   
                   
                   
                   
                   
                   
                   
                 10.0 
               
               
                 Viscosity 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Dispersed 
                 ml/30 
                 46.0 
                 42.0 
                 30.0 
                 54.0 
                 50.0 
                 44.4 
                 Maximum 
               
               
                 Filtrate 
                 min 
                   
                   
                   
                   
                   
                   
                 12.50 
               
               
                 Cement 
                 pH 
                 8.62 
                 8.51 
                 8.89 
                 8.47 
                 8.69 
                 8.636 
                 Maximum 
               
               
                 Contamination 
                   
                   
                   
                   
                   
                   
                   
                 9 
               
               
                 Methylene blue 
                 meq/100 g 
                 100 
                 95 
                 100 
                 100 
                 100 
                 99.0 
                 Minimum 
               
               
                 Test (MTB) 
                   
                   
                   
                   
                   
                   
                   
                 65.0 
               
               
                 Residue on 200 
                 % by wt. 
                 0.69 
                 0.64 
                 0.72 
                 0.75 
                 0.65 
                 0.69 
                 Maximum 
               
               
                 mesh (wet) 
                   
                   
                   
                   
                   
                   
                   
                 2.50 
               
               
                 Residue on 100 mesh  
                 % by wt. 
                 81.52 
                 87.26 
                 71.33 
                 68.07 
                 65.31 
                 74.69 
                 Maximum 
               
               
                 (Dry) 
                   
                   
                   
                   
                   
                   
                   
                 2.00 
               
               
                   
               
             
          
         
       
     
         [0035]    Table 4 shows data comparing five samples of modified non-API bentonite, where the bentonite was modified with low viscosity sodium carboxymethyl cellulose (CMC-LV). During modification, the viscosity at both 300 and 600 rpm, pH value, plastic viscosity (cp), and yield point (lbs./100 ft. 2 ) were modified to meet API specifications. 
         [0036]    Table 3 describes yield of unmodified non-API bentonite whereas Table 4 describes the yield point of modified non-API bentonite. Yield is calculated using a yield test, and certain internal minimum specification requirements are 90 barrel/short ton. For yield point, certain internal maximum specification requirements include a maximum ratio of 1.5 yield point:plastic viscosity. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Evaluation of five modified bentonite samples. 
               
             
          
           
               
                   
                   
                 Bentonite 
                 Soda ash 
                 PAC ™-R 
                   
               
               
                 Sample # 
                 Total (g) 
                 (g) 
                 wt. % 
                 wt. % 
                 CMC wt. % 
               
               
                   
               
             
          
           
               
                 1 
                 30 
                 27.6 
                 1% 
                 3% 
                 4% 
               
               
                 2 
                 30 
                 27.3 
                 1% 
                 3% 
                 5% 
               
               
                 3 
                 30 
                 27 
                 1% 
                 3% 
                 6% 
               
               
                 4 
                 30 
                 26.7 
                 1% 
                 3% 
                 7% 
               
               
                 5 
                 30 
                 26.4 
                 1% 
                 3% 
                 8% 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Evaluation of five modified bentonite samples. 
               
             
          
           
               
                   
                 Viscosity 
                   
                 plastic 
                 yield point 
                   
               
               
                   
                 (cp) 
                   
                 viscosity 
                 (lbs./100  
                   
               
             
          
           
               
                 Sample # 
                 600 
                 300 
                 pH 
                 (cp) 
                 ft 2 ) 
                 b 
               
               
                   
               
             
          
           
               
                 1 
                 37.5 
                 22 
                 7.44 
                 15.5 
                 6.5 
                 0.41 
               
               
                 2 
                 41 
                 26 
                 8.14 
                 15 
                 11 
                 0.73 
               
               
                 3 
                 39.5 
                 23 
                 7.92 
                 16.5 
                 6.5 
                 0.39 
               
               
                 4 
                 47.5 
                 28.5 
                 7.9 
                 19 
                 9.5 
                 0.5 
               
               
                 5 
                 46 
                 27.5 
                 7.89 
                 18.5 
                 9 
                 0.48 
               
               
                   
               
             
          
         
       
     
         [0037]    Table 5 shows certain effects of grain size on the modified non-API bentonite performance. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Effect of grain size on the modified non-API bentonite. 
               
             
          
           
               
                   
                 Total  
                   
                 Particle  
                 PAC  
                 CMC  
                 Viscosity 
               
               
                   
                 Mass  
                 Bentonite  
                 size 
                 wt. 
                 wt. 
                 (cp) 
               
             
          
           
               
                 # 
                 (g) 
                 (g) 
                 (mesh) 
                 % 
                 % 
                 600 
                 300 
               
               
                   
               
             
          
           
               
                 1 
                 30 
                 26.625 
                 1 
                 3.75% 
                 7.50% 
                 30 
                 16 
               
               
                 2 
                 30 
                 26.625 
                 50 
                 3.75% 
                 7.50% 
                 38 
                 21 
               
               
                 3 
                 30 
                 26.625 
                 100 
                 3.75% 
                 7.50% 
                 43.5  
                 24.5 
               
               
                 4 
                 30 
                 26.625 
                 140 
                 3.75% 
                 7.50% 
                 44.5  
                 25.5 
               
               
                 5 
                 30 
                 26.625 
                 200 
                 3.75% 
                 7.50% 
                 50 
                 30 
               
               
                   
               
             
          
         
       
     
         [0038]    Table 6 shows certain effects of soda ash on the modified non-API bentonite performance. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                 Certain effects of soda ash concentration on modified  
               
               
                 non-API bentonite. 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   
                   
                 Soda  
                 PAC ™- 
                   
               
               
                   
                 Total  
                 Bentonite  
                 ash  
                 R  
                   
               
               
                 # 
                 (g) 
                 (g) 
                 wt. % 
                 wt. % 
                 CMC wt. % 
               
               
                   
               
               
                 1 
                 30 
                 27.3 
                   1% 
                 3% 
                 5% 
               
               
                 2 
                 30 
                 27.15 
                 1.5% 
                 3% 
                 5% 
               
               
                 3 
                 30 
                 27 
                   2% 
                 3% 
                 5% 
               
               
                 4 
                 30 
                 26.85 
                 2.5% 
                 3% 
                 5% 
               
               
                 5 
                 30 
                 26.7 
                   3% 
                 3% 
                 5% 
               
               
                   
               
             
          
           
               
                   
                 Viscosity 
                   
                 plastic  
                 yield point 
                   
               
               
                   
                 (cp) 
                   
                 viscosity 
                 (lbs./ 
                   
               
             
          
           
               
                   
                 600 
                 300 
                 pH 
                 (cp) 
                 100 ft 2 ) 
                 b 
               
               
                   
               
               
                 1 
                 41 
                 26 
                 8.14 
                 15 
                 11 
                 0.7333 
               
               
                 2 
                 49 
                 31 
                 8.47 
                 18 
                 13 
                 0.7222 
               
               
                 3 
                 60.5 
                 41 
                 8.78 
                 19.5 
                 21.5 
                 1.1026 
               
               
                 4 
                 55 
                 37 
                 8.93 
                 18 
                 19 
                 1.0556 
               
               
                 5 
                 60.5 
                 42.5 
                 9.3 
                 18 
                 24.5 
                 1.3611 
               
               
                   
               
             
          
         
       
     
         [0039]    Table 7 shows certain effects of PAC™-R concentration on modified non-API bentonite. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                 Effects of PAC ™-R concentration on modified non-API bentonite. 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Total  
                 Bentonite  
                 Soda ash  
                 PACT ™-  
                   
               
               
                 # 
                 (g) 
                 (g) 
                 wt. % 
                 R wt. % 
                 CMC wt. % 
               
               
                   
               
               
                 1 
                 30 
                 27.9 
                 1% 
                 1% 
                 5% 
               
               
                 2 
                 30 
                 27.6 
                 1% 
                 2% 
                 5% 
               
               
                 3 
                 30 
                 27.3 
                 1% 
                 3% 
                 5% 
               
               
                 4 
                 30 
                 27 
                 1% 
                 4% 
                 5% 
               
               
                 5 
                 30 
                 26.7 
                 1% 
                 5% 
                 5% 
               
               
                   
               
             
          
           
               
                   
                 Viscosity 
                   
                 Plastic  
                 yield point 
                   
               
               
                   
                 (cp) 
                   
                 viscosity 
                 (lbs./100  
                   
               
             
          
           
               
                 # 
                 600 
                 300 
                 pH 
                 (cp) 
                 ft 2 ) 
                 b 
               
               
                   
               
               
                 1 
                 20 
                 11 
                 8.1 
                 9 
                 2 
                 0.2222 
               
               
                 2 
                 34 
                 19 
                 8.02 
                 15 
                 4 
                 0.2667 
               
               
                 3 
                 41 
                 26 
                 8.14 
                 15 
                 11 
                 0.7333 
               
               
                 4 
                 50 
                 31.5 
                 7.46 
                 18.5 
                 13 
                 0.7027 
               
               
                 5 
                 68.5 
                 44 
                 8.44 
                 24.5 
                 19.5 
                 0.7959 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
             
               
               
             
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 8 
               
               
                   
               
               
                 Evaluation for modified non-API bentonite sample (8.5% PAC ™-R added). 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Yield Test 
                 Internal Requirement 
               
               
                   
               
             
          
           
               
                 Concentration 
                 20 ppb 
                 22.5 ppb 
                 24 ppb 
                 Min 90 Barrel/Short Ton 
               
               
                 Viscosity at 600 rpm 
                 40 
                 53 
                 59 
                 Yield 
               
               
                 Apparent viscosity 
                 20 cp 
                 26.5 cp 
                 29.5 cp 
               
             
          
           
               
                 Yield 
                 113.88 Barrel/Short Ton 
                   
               
             
          
           
               
                 Yield Point/Plastic Viscosity Ratio Test 
                 Required Specification 
               
             
          
           
               
                 Viscosity at 600 rpm 
                 66 
                 Max 1.5 YP/PV Ratio 
               
               
                 Viscosity at 300 rpm 
                 42 
               
               
                 Plastic Viscosity Ratio 
                 22 cp 
               
               
                 Yield Point 
                 22 lbs./100 sq. ft. 
               
               
                 YP/PV Ratio 
                  1 
               
             
          
           
               
                 Dispersed Plastic Viscosity &amp; Filtrate Test 
                 Required Specification 
               
             
          
           
               
                 Viscosity at 600 rpm 
                 65 
                 Min 10 cp 
               
               
                 Viscosity at 300 rpm 
                 42 
               
               
                 Dispersed Plastic Viscosity 
                 23 cp 
               
               
                 Dispersed Filtrate 
                 10 ml/30 min 
                 Max 12.5 ml/30 min 
               
             
          
           
               
                 Cement Contamination Test 
                 Required Specification 
               
             
          
           
               
                 pH After Aging 
                   8.6 
                 Max 9 
               
             
          
           
               
                 Residue on 100 mesh (dry) Test 
                 Required Specification 
               
             
          
           
               
                 Residue on 100 mesh (dry) 
                 0.15 wt. % 
                 Max 2 
               
             
          
           
               
                 Moisture Test 
                 Required Specification 
               
             
          
           
               
                 Moisture 
                 10.2 wt. % 
                 Max 13 
               
             
          
           
               
                 Residue on 200 mesh (wet) Test 
                 Required Specification 
               
             
          
           
               
                 Residue on 200 mesh (wet) 
                 0.12 wt. % 
                 Max 2.5 
               
             
          
           
               
                 MBT (Active Clay) 
               
             
          
           
               
                 MBT (Active Clay) 
                 122 lb/bbl 
               
               
                   
               
             
          
           
               
                 Peroxide Test 
               
             
          
           
               
                   
                 RHEOLOGY @ ROOM- 
                 Treated Bentonite 
               
               
                   
                 TEMPERATURE ON FANN-36 
                 Pre-hydrated in: 
               
             
          
           
               
                   
                 VISCOMETER 
                 Water 
                 Hydrogen 
               
               
                   
               
               
                 After Static Aging for 70 
                 600 rpm 
                 72 
                 6 
               
               
                 His at Room Temperature 
                 300 rpm 
                 46 
                 4 
               
               
                   
                 200 rpm 
                 36 
                 3 
               
               
                   
                 100 rpm 
                 24 
                 2 
               
               
                   
                  6 rpm 
                 4 
                 1 
               
               
                   
                  3 rpm 
                 2 
                 1 
               
               
                   
                 PV 
                 26 
                 2 
               
               
                   
                 VP 
                 20 
                 2 
               
               
                   
               
             
          
         
       
     
         [0040]    In Table 8, dispersed filtrate is according to API Standard 13A which outlines the test procedure used for drilling fluids. Fluid loss is a measure of bentonite slurry&#39;s ability to form a low permeability filter cake. The max internal requirement for testing was 12.5 ml/30 min. 
         [0041]    Advantageously in the embodiments of the present disclosure, raw water was used to remove contaminants from unmodified bentonite before its modification by carboxymethylcellulose. Acid was not used to remove contaminants to avoid any negative effect on the chemical properties of bentonite ore. Notably, commercial bentonite was not used in the preparation recipe. PAC™-R polymer was used to enhance the viscosity of the bentonite ore in water. In certain embodiments, other additives were not used to enhance the viscosity of the bentonite ore. 
         [0042]    The addition of soda ash shows a positive effect in terms of plastic viscosity; however, as the amount of soda ash is increased, the pH of the composition increases as well. 
         [0043]    The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise. 
         [0044]    In the drawings and specification, there have been disclosed embodiments of compositions of and methods for making modified bentonite, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The embodiments of the present disclosure have been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the disclosure as described in the foregoing specification, and such modifications and changes are to be considered equivalents and part of this disclosure. 
         [0045]    Where the Specification or the appended Claims provide a range of values, it is understood that the interval encompasses each intervening value between the upper limit and the lower limit as well as the upper limit and the lower limit. The present disclosure encompasses and bounds smaller ranges of the interval subject to any specific exclusion provided. Where the Specification and appended Claims reference a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously except where the context excludes that possibility.