Abstract:
A drilling fluid additive is provided and the additive consist of: hydrolyzed glucose syrup solids in the amount from about 30 to about 90% by weight of total volume of the additive and a liquid medium in the amount from about 10 to about 70% by weight of total volume of the additive.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a drilling fluid additive and more specifically, a continuous liquid phase of drilling fluids consisting of corn syrup solids and a liquid medium. 
     2. Description of the Related Art 
     There are various drilling applications and additives in the art that combine carbohydrates with a plurality of different ingredients. These formulations have provided for moderate results. 
     There are also various ingredients combined to provide for a continuous liquid phase of a drilling fluid. In the past, water, diesel oil, synthetic oils and combinations of oils and emulsions have been used as the continuous liquid phase of drilling fluids with inefficient to moderate results. 
     A drilling fluid with water as the continuous liquid phase has many economical advantages. Water is plentiful, non-polluting and environmentally friendly when properly maintained. It is very important that the additives mixed with the water are also non-polluting and environmentally friendly. Fluid loss additives, lubricants, dispersants, shale and formation inhibitors should also be non-polluting and environmentally friendly. A fluid that has higher concentrations of these additives typically has higher toxicity and subsequently has a lower LC50 number. 
     Using diesel oil as a continuous liquid phase of a drilling fluid is economical, but environmentally hazardous. Drill cuttings must be contained and remediated, as well as earthen pits are contaminated with the diesel oil and salt water used, adding to the costs and inefficiency of diesel based fluids. 
     Using a synthetic hydrocarbon or specific olefin for the continuous liquid phase of the drilling fluid has its advantages, however, these synthetic oils are expensive and in short supply. 
     The present invention provides for an economically efficient and environmentally safe drilling fluid additive and can also function as the continuous liquid phase of the drilling fluid. The present invention also provides for a drilling fluid additive that provides the advantages of lubrication and wellbore stability. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention provides for a drilling fluid additive consisting essentially of: corn syrup solids in the amount from about 30 to about 80% by volume of total volume of the additive and a liquid medium in the amount from about 20 to about 70% by volume of total volume of the additive. 
     In another embodiment, the liquid medium is selected from a group consisting of water, purified water, ionized water, salt water and mixtures thereof. In yet another embodiment, the additive improves the lubrication and reduces the coefficient of friction on the water phase of the drilling fluid. 
     In still another embodiment, the liquid medium is an aqueous liquor. For purposes of this invention, the term “aqueous liquor” is defined as any liquid medium or juice. 
     In still yet another embodiment, the corn syrup solids are in the amount from about 70 to about 80% by volume of the total volume of the additive. In a further embodiment, the liquid medium is in the amount from about 20 to about 30% by volume of the total volume of the additive. In yet a further embodiment, the density of the additive is from about 8 to about 12 pounds per gallon and more specifically 9 to about 11.8 pounds per gallon. In still a further embodiment, the additive suppresses and restricts hydration of clays and shales when deposed into a wellbore. 
     In another further embodiment, the additive is dextrose syrup. In still yet a further embodiment, the syrup solids can be derived from all different types of sugars and carbohydrates. Sugars include sucrose, dextrose and fructose. The carbohydrates utilized in the present invention may be derived from sugar cane, sugar beet, fruit, honey sorghum and sugar maple (Maple syrup). 
     In another embodiment, the corn syrup solids are hydrolyzed prior to being combined with a liquid medium. In still another embodiment, the additive is combined with copolymer beads. In yet another embodiment, the copolymer beads are comprised of styrene and divinylbenzene (DVB). 
     In still yet another embodiment, the present invention relates to a continuous liquid phase solution for a drilling fluid, said solution consists essentially of: corn syrup, corn syrup solids and a liquid medium. 
     In a further embodiment, the corn syrup is from about 10 to about 90% by volume of total volume of the solution, the corn syrup solids is from about 10 to about 80% by volume of total volume of the solution, and the liquid medium is from about 20 to about 90% by volume of total volume of the solution. 
     In still a further embodiment, the present invention relates to a drilling fluid additive consisting of hydrolyzed glucose syrup solids in the amount from about 30 to about 90% by volume of total volume of the additive and a liquid medium in the amount from about 10 to about 70% by volume of total volume of the additive. 
     In another embodiment, the present invention also relates to a continuous liquid phase of the drilling fluid which consists essentially of concentrated carbohydrates, namely corn syrup or cane syrup, or a combination of the two with a liquid medium such as water. The testing established that the higher the concentration of carbohydrates, the more the continuous fluid resembles an oil based continuous phase fluid. It was also discovered that the degree of lubrication, well bore stabilization and fluid loss control are directly proportional to the percentage of the concentrated carbohydrates. Testing show that this present invention is non-toxic, biodegradable and environmentally friendly with an LC 50 rating of greater than 1,000,000 at a concentration of 50%. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the present invention. These drawings are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the present invention, and together with the description, serve to explain the principles of the present invention. 
         FIG. 1  is a depiction of the additives of the present invention in varying concentrations and how such concentrations of syrup solids effectuate the reaction with clays; 
         FIG. 2  is a graph showing compressed clay pellets that were submerged for 72 hours in varying concentrations of the corn syrup solids in the additive; 
         FIG. 3  is a graph showing the lubricity of the present invention; and 
         FIG. 4  is a graph showing a comparison of a water based drilling fluid weighing 16.0 ppg containing 30% of additive with a 16.0 ppg oil based drilling fluid. 
     
    
    
     Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
     DETAILED DESCRIPTION OF THE INVENTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various forms. The figures are not necessarily to scale, some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     In one embodiment, the additive of the present invention is manufactured as follows: pure corn starch that is approximately 99 percent pure is converted into ordinary corn syrup through a process called acid hydrolysis. In this process, the liquid corn starch is mixed with a weak solution of hydrochloric acid and heated in order to break down the corn starch molecules into sugar. The hydrolysis can be controlled in order to produce varying concentrations of corn syrup. The longer the hydrolysis process is allowed to proceed, the more concentrated the corn syrup becomes. The liquid corn syrup is then filtered and further refined and evaporated to reduce the amount of water, thus producing corn syrup solids. Some important properties of corn syrup are the dextrose and fructose content. Product information and product samples for testing were obtained from the Grain Processing Corporation (GPC). The initial testing of GPC products with a trademark name Maltrin® was to improve the solid suspension properties of various liquids in drilling fluid additives such as glycols, oils, and water. The particular solid to be suspended would be styrene and divinylbenzene (DVB) copolymer beads with a specific gravity of approximately 1.05 to 1.2 kg/m 3 . The density of the liquid corn syrup is directly proportional to the dissolved solids content of the corn syrup. Clear corn syrup with densities of 11.5 to 11.8 pounds per gallon may be blended. 
     Preventing Hydration and Swelling of Clays in Well Bore: 
     Referring now to  FIG. 1 , the drilling additive of the present invention prevents the hydration and absorption of water by the hydrophilic clays and shales in the drilled formation. Hydrophilic water sensitive clays and shales contain substantial amounts of colloidal bentonite. Surface hydration and osmotic hydration cause the diameter of the well bore to shrink smaller than what was originally drilled. Preventing this hydration and swelling is essential in order to prevent well bore swabbing when the drilling assembly is extracted from the well bore. There have been various water-based drilling fluids that have been used to prevent hydration and swelling but such fluids have been used with moderate success. These fluids included calcium in lime based fluids, gypsum based fluids, potassium based fluids, and salt based fluids such as calcium chloride and sodium chloride fluids. 
     In one embodiment, the present invention uses a solution of higher concentrations of dissolved corn syrup solids to restrict or suppress the hydration of hydrophilic, water-sensitive clays and shales. In addition, the adhesion or stickiness of the Gumbo-type shales have also been reduced. In  FIG. 1 , the hydration and swelling of clay are tested by inserting a compressed clay pellet (Bentonite) in each of nine containers. The containers (from left to right in  FIG. 1 ) are then filled with the following solutions as set forth in Table 1 below: 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Testing of Hydration and Swelling of Clays Based on Increased 
               
               
                 Concentrations of Corn Syrup Solids 
               
             
          
           
               
                   
                   
                 Corn Syrup 
                   
               
               
                 Container (#) 
                 Water % 
                 Concentrate (%) 
                 Results 
               
               
                   
               
               
                 #1 
                 100%  
                  0% 
                 Poor 
               
               
                 #2 
                 90% 
                 10% 
                 Poor 
               
               
                 #3 
                 80% 
                 20% 
                 Fair 
               
               
                 #4 
                 70% 
                 30% 
                 Good 
               
               
                 #5 
                 60% 
                 40% 
                 Good 
               
               
                 #6 
                 50% 
                 50% 
                 Good 
               
               
                 #7 
                 40% 
                 60% 
                 Excellent 
               
               
                 #8 
                 30% 
                 70% 
                 Excellent 
               
               
                 #9 
                 20% 
                 80% 
                 Excellent 
               
               
                 #10  
                 10% 
                 90% 
                 Excellent (not shown) 
               
               
                   
               
             
          
         
       
     
       FIG. 1  and Table 1 clearly show how increased amounts of the concentration of the corn syrup solids provide for increased results in the suppression and restriction of the hydration of the clay. This invention shows that the osmolality of the liquid corn syrup carbohydrate is created by the dissolved corn syrup solids in the continuous liquid phase of the drilling fluid. The degree of osmolality is directly proportional to the percentage of dissolved corn syrup solids in the liquid corn syrup. This osmotic dehydration was accomplished without any salts. 
       FIG. 2  shows a graph showing compressed clay pellets submerged for 72 hours in concentrations from about 0 to about 90% of additive mixed with water having a pH of 9.5. The graph shows how increased amounts in the concentration of the additive lessened the amount of swelling in the compressed clays further providing evidence that the present invention prevents the hydration and absorption of water by the hydrophilic clays and shales in the drilled formation. 
     It appears that the dissolved corn syrup solids in the liquid corn syrup carbohydrate have a greater demand for the water present in the drilling fluid than the hydrophilic shale, thus lessening the swelling of the wet well bore. It seems that the wall cake which is formed as soon as the shale is penetrated acts as the semi-permeable membrane in order for any osmosis to occur. 
     Keeping the Well Bore “In Gauge”: 
     In drilling subterranean oil and gas wells, keeping the well bore “in gauge” is critical. This term means keeping the well bore the same size as the drilling bit that drilled the well bore. The reduction in well bore size is usually directly proportional to the amount of time that the well bore is exposed to the drilling fluid. In many cases, the well bore may be exposed to the fluid for many days or weeks before the well bore casing is installed. The drilling fluid deposits a wall cake on the surface of the well bore. The thickness of the wall cake is directly proportional to the fluid loss or the amount of liquid that is forced from the drilling fluid into the well bore. Therefore, the less liquid leaving the drilling fluid, the thinner the cake wall (filter cake) will be. Having a low filtrate loss and a thin filter cake is desired and produces an “in gauge” well bore. 
     Another reason for the well bore size to lose its “in gauge” would be the hydration and swelling of the hydrophilic clays and shale in the wall of the well bore. The swelling of this shale may be caused by osmotic absorption of the drilling fluid or “hydration”. 
     Controlling the thickness and the quality of the filter cake which is deposited on the wellbore is absolutely essential to keeping the wellbore “in gauge”. The thickness of the filter cake is directly proporational to the volume of liquid passing through the filter cake. 
     To represent “in gauge” testing of the drilling fluid additive of the present invention, the following tests were conducted to observe (a) fluid loss in ml; (b) filter cake weight in grams; and (c) filter cake thickness in inches: 
     (1) High Pressure High Temp Filtration Test: A mud sample is heated to 250 degrees F. and 500 psi of pressure is applied to force liquid through the a filter paper. The volume of liquid and filter cake thickness are recorded. 
     The results of the High Pressure High Temp Filtration Test is set forth in Table 2 below: 
                                                                                                               TABLE 2                   High Pressure High Temp Filtration Test                    Base Mud + 30%   Base Mud + 40%           Base Mud   Additive   Additive                    Density:   11.0               pH Meter   8.3               600 rpm   32   92   62       300 rpm   19   56   35       200 rpm   15   42   25       100 rpm   10   25   15       6 rpm   4   5   4       3 rpm   3   4   3       PV @ 120 F.   13   36   27       YP   6   20   8            Gels 10 s/10 m/30 m   10/34   7/22/29   3/10/19            HPHT @ 250   36.0   3.2   2.4       degree F./mL                   Cake Wt/g   24   5.4   4.7            Cake Thickness/inch   6/32   1/32   1/32                    
(2) Dynamic Filtration Test: This test utilizes a sand disc with a 5 Darey, 20 micron filter media. This test consists of more pressure, 1000 psi, with a more porous filter media. The fluid is sheared or stirred during the test.
 
     The results of the Dynamic Filtration Test is set forth in Table 3 below: 
                                                                                     TABLE 3                   Dynamic Filtration Test       5 Darcy, 20 Micron Filter Media       200 Degree F., 600 RPM @ 1000 PSI for 60 Minutes                    Base Mud + 30%   Base Mud + 40%           Base Mud   Additive   Additive            Time (Minutes)   Fluid Loss (ml)                    Initial Spurt   8.0   0.0   0.0       15 Minutes   31.2   2.0   1.2       30 Minutes   46.0   3.4   2.2       45 Minutes   56.4   4.7   3.0       60 Minutes   66.0   6.5   5.4       Cake wt (g)   44   8   8            Cake thickness (inch)   11/32   2/32   1/32                    
Results of High Pressure High Temp Filtration Test &amp; Dynamic filtration Test:
 
     Substantial reductions in fluid loss, filter cake weight and filter cake thickness are obvious from these results. The additive of this invention contributes to the improvement of the wall cake quality thereby helping to provide an “in gauge” well bore. 
     Lubricity Testing: 
     Improving the lubricating qualities of the drilling fluid is an area where the additive of the present invention excelled. A lubricity meter was used to measure the lubricating qualities of water having a pH of 9.5 and comparing the results with various concentrations ranging from 10% to 90% by volume of additive with water. Torque readings were taken from 100 to 600 inch pounds of torque. 
     The results of the lubricity testing are set forth in Table 4 below and shown in 
       FIG. 3 : 
     
       
         
               
             
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Lubricity Test 
               
             
          
           
               
                 Sample: 
                 Results: 
               
               
                   
               
               
                 (1) water 
                 seized at a torque of 290 inch pounds 
               
               
                 (2) 10% additive and 90% water 
                 seized at 360 inch pounds 
               
               
                 (3) 20% additive and 80% water 
                 seized at 440 inch pounds 
               
               
                 (4) 30% additive and 70% water 
                 did not seize at 600 inch pounds 
               
               
                 (5) 40% additive and 60% water 
                 torque reading at 55 
               
               
                 (6) 50% additive and 50% water 
                 torque reading at 50 
               
               
                 (7) 60% additive and 40% water 
                 torque reading at 42 
               
               
                 (8) 70% additive and 30% water 
                 torque reading at 35 
               
               
                 (9) 80% additive and 20% water 
                 torque reading at 27 
               
               
                   
               
             
          
         
       
     
     From  FIG. 3  and Table 4, it can be seen that a concentration of 30% or more of the additive did not seize and the resulting torque reading continually decreased as the concentration of the additive was increased. 
       FIG. 4  illustrates the comparison of a water based drilling fluid weighing 16.0 ppg containing 30% of additive with a 16.0 ppg oil based drilling fluid. As evidenced by  FIG. 4 , the lubricating qualities of the water based drilling fluid containing 30% by volume of additive was almost identical to the oil mud. The water based drilling fluid used for this test is extremely environmentally friendly having an LC50 rating of greater then 1,000,000. 
     Controlling the Density of the Drilling Fluid: 
     Controlling the density of the drilling fluid is essential to the success of drilling oil or gas wells. The density of water having a specific gravity of 1.0 and weighing 8.34 pounds per gallon may be increased by dissolving a salt such as sodium chloride and increasing the density of water to about 10.5 pounds per gallon at the saturation point of sodium chloride. By saturating calcium chloride, a density of about 11.6 pounds per gallon may be achieved. Other salts such as zinc bromide may be used to produce higher densities. The negative side of salt water fluids is the corrosion and lack of compatibility with other additives and also exhibit poor lubrication qualities. 
     A concentrated carbohydrate corn syrup consisting of fresh water and from about 60 to about 75 percent by weight of dissolved corn syrup solids will have a density of approximately 11.5 to 11.8 pounds per gallon. In a further embodiment, the present invention uses concentrated corn syrup to increase the density of the liquid phase of the drilling fluid as set forth in Table 5 below: 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Increased Concentrations of Corn Syrup Solids Relate to 
               
               
                 Density of Liquid Phase of Drilling Fluid 
               
             
          
           
               
                 Volume of Additive (%) 
                 Water (%) 
                 Density (lbs per Gallon) 
               
               
                   
               
             
          
           
               
                 90% 
                 10% 
                 11.2 
               
               
                 80% 
                 20% 
                 10.9 
               
               
                 70% 
                 30% 
                 10.6 
               
               
                 60% 
                 40% 
                 10.3 
               
               
                 50% 
                 50% 
                 10.0 
               
               
                 40% 
                 60% 
                 9.7 
               
               
                 30% 
                 70% 
                 9.4 
               
               
                 20% 
                 80% 
                 9.1 
               
               
                 10% 
                 90% 
                 8.8 
               
               
                   
               
             
          
         
       
     
     The densities of a drilling fluid may be increased by these values without the addition of particulate solids such as barite. Thus, any settlings or stratifying of barite solids for a liquid drilling fluid up to 11.8 pounds per gallon are eliminated. 
     Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the attendant claims attached hereto, this invention may be practiced otherwise than as specifically disclosed herein.