Patent Application
20080004189
The present disclosure provides compositions and methods for the biocidal treatment of oil field fluids. Specifically, effervescent biocidal compositions for oil field applications are disclosed. The compositions generally include one or more biocidal ingredients delivered in the form of an effervescent tablet.
A familiar example of effervescence is Alka-Seltzer dissolving in water. The inventors have discovered that effervescent tablets provide a useful delivery method for delivering biocidal agents to oil field fluids because (1) they alleviate problems encountered with the current mode of choice for application of dry biocides, i.e., water soluble bags and (2) the effervescent action of the tablet dissolving in the fluid serves to disperse the biocidal agent in the fluid.
Effervescence is the reaction (typically in aqueous environment) of acids and bases to produce a gas such as carbon dioxide. Examples of suitable acids include citric, malic, tartaric, adipic, and fumaric acids. Examples of suitable bases include sodium bicarbonate, potassium bicarbonate, sodium carbonate, and potassium carbonate. Effervescent tablets can include additional components such as binders, lubricants, and fillers. Examples of additional components can include, but are not limited to, dextrose, sorbitol, xyitol, lactose, borax, sodium benzoate, polyethylene glycol, and adipic acid. Additional examples of suitable acids, bases, lubricants and the like for effervescent formulations are described in U.S. Pat. No. 6,811,793, which is incorporated by reference herein in its entirety. Additionally, the effervescent tablets disclosed here include one or more biocidal agents.
Methods of making effervescent tablets are known in the art. Generally, effervescent tablets and powders are produced in a similar manner as conventional tablets and powders, but production must occur in a low humidity environment. Effervescent granulations can be mixed in conventional blending equipment, such as ribbon, twin-cone, and V-type blenders. Traces of moisture can result in erratic granulation results. Formulations can go through a drying process prior to tabletting. A typical effervescent formulation will contain less than about 0.5% moisture. Temperature and humidity in the production area typically should be about 65 to about 75 F and relative humidity of about 10 percent or less.
The effervescent tablets disclosed herein can be used to deliver essentially any biocides used for oil field applications, including but not limited to, 2,2,-dibormo-3-nitrilo-propionamide (DBNPA), 1,2-dibromo-2,4-dicyanobutane, 2-bromo-2-nitropropane-1,3-diol, 4,4-dimethyloxazolidine, 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride, tris(hydroxymethyl)nitromethane, alkyl dimethyl benzyl ammonium chloride, isothiazolone, carbamates, metronidazole, and glutaraldehyde. Additional biocides are known in the art, for example, the biocides listed in U.S. Pat. No. 4,552,591, the entire contents of which are incorporated herein by reference. Furthermore, commercially available biocide formulations can be reformulated as effervescent formulations for delivery according to the present disclosure. Examples of suitable formulations include formulations such as the BIO-CLEAR formulations e.g., BIO-CLEAR 550, BIO-CLEAR 1050, BIO-CLEAR 750, and BIO-CLEAR 1000, available from Clearwater, Inc., Houston, Tex.
Effervescent tablets can contain one biocidal agent or can contain more than one biocidal agent. The amount of biocidal agent per tablet can be typically between about 10 weight percent and about 90 weight percent, although about 20 weight percent to about 80 weight percent is more typical. For example, a effervescent biocidal tablet might contain about 50 percent biocide. A tablet containing two different biocides might contain 25 percent of one biocide, 25 percent of another biocide, 20 percent acid, 20 percent base, and 10 percent flow improver, filler, binder, etc. As an example, an effervescent biocidal tablet might contain about 5 to about 35 weight percent of 2,2,-dibormo-3-nitrilo-propionamide and about 5 to about 35 weight percent of percent of 1,2-dibromo-2,4-dicyanobutane. As a more specific example, an exemplary effervescent biocidal tablet contains about 25 percent DBNPA, about 25 percent 1,2-dibromo-2,4-dicyanobutane, about 20 percent sodium bicarbonate, about 20 percent citric acid, and about 10 percent boric acid.
Given an effervescent biocidal formulation containing a given concentration of biocide, it is within the ability of one of skill in the art to decide how much effervescent biocidal formulation to use to treat a given amount of oil field fluid. Oil field fluids include any fluid used in oil field applications, including but not limited to drilling fluid, completion fluid, workover fluid, fracturing fluid packer fluid, injection water, produced water that is to be reinjected, and the like. Such fluids are typically aqueous. The fluids are treated by adding a sufficient amount of effervescent biocidal tablet to the fluid to achieve the desired amount of biocidal agent in the fluid. As an example, the desired amount of biocidal agent might be about 10 ppm to about 50,000 ppm, and more typically about 100 ppm to about 2,000 ppm for treating fracturing fluid.
Generally, the oil field fluid is treated by adding an adequate amount of effervescent tablets to a tank or other container containing the oil field fluid and allowing the tablets to effervesce, thus dispersing the biocidal agent in the oil field fluid. The oil field fluid can then be used for its intended purpose or stored for a time prior to use.
While the disclosed effervescent biocidal materials have primarily been discussed herein with regard to tablets, any form of effervescent material can be used to deliver biocides according to the disclosed methods. For example, effervescent powder blends, flakes, particles, sachets, and the like can be used. The effervescent biocidal composition can be delivered to a container containing oil field fluid by any means, for example by simply dumping the biocidal composition into the container using a shovel, scoop, hopper, or by hand. Alternatively, dissolvable packages of effervescent biocidal material can be added to such containers.
While the disclosed effervescent biocidal materials have primarily been discussed herein with regard to treating oil field fluids, the effervescent biocidal materials can be used to treat any fluid under circumstances where control of contamination and proliferation of bio-organisms is needed. For example, the disclosed compositions and methods can be used to treat water in cooling towers, evaporation ponds, waste water, and the like.
It should be understood that the inventive concepts disclosed herein are capable of many modifications. To the extent such modifications fall within the scope of the appended claims and their equivalents, they are intended to be covered by this patent.
