Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
1999-01-04
2001-10-02
Tucker, Philip (Department: 1721)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C507S269000, C507S906000, C507S921000, C507S202000, C516S034000
Reexamination Certificate
active
06297202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to defoaming compositions and methods, and more particularly, to such compositions and methods for preventing the formation of foam or breaking foam in well treating fluids.
2. Description of the Prior Art
Defoaming compositions and agents have long been used in the oil and gas industry to prevent the formation of a foam or to destroy a previously formed foam. The defoaming compositions are commonly utilized as components in well treating fluids to prevent the formation of foam during the preparation and/or pumping of the treating fluids. Also, defoaming compositions have been utilized heretofore for breaking previously formed foamed well treating fluids. That is, when a stable foamed well treating fluid must be disposed of on the surface, a defoaming composition is added to the fluid to destroy the foam whereby the non-foamed components of the treating fluid can be readily disposed of.
A variety of defoaming compositions and agents have been utilized heretofore. Examples of such defoaming compositions and agents utilized in well treatment fluids include tributyl phosphate and acetylenic diol which are environmentally unsafe. Other prior art defoaming agents which are environmentally safe include polypropylene glycol and a mixture of polypropylene glycol with a copolymer of ethylene oxide and propylene oxide monomers. While these defoamers function adequately to prevent the formation of foam in well treating fluids when they are prepared and pumped, they do not function adequately for defoaming previously formed foamed well treating fluids, and particularly, previously formed foamed well cement slurries.
Thus, there is a continuing need for improved environmentally safe defoaming compositions for use in various fluids including well treatment fluids.
SUMMARY OF THE INVENTION
The present invention provides improved environmentally safe defoaming compositions and methods which meet the needs described above and overcome the deficiencies of the prior art. The compositions of the invention are basically comprised of polypropylene glycol, particulate hydrophobic silica and a liquid diluent. While various liquid diluents can be utilized, those which are particularly suitable include fatty acid methyl esters, olefins having one or more internal double bonds, alpha-olefins, polyalpha-olefins and linear paraffins.
A preferred defoaming composition of this invention is comprised of polypropylene glycol having a molecular weight of about 4,000 present in the composition in an amount of about 30% by weight thereof, a particulate hydrophobic silica comprised of silicone oil treated precipitated silica present in the composition in an amount of about 16% by weight thereof and an olefin having from about 11 to about 14 carbon atoms and one or more internal double bonds present in the composition in an amount of about 54% by weight thereof.
A method of the present invention for preventing the formation of foam in a well treating fluid during its preparation or pumping into a well bore comprises combining a defoaming composition of this invention with the well treating fluid prior to preparing or pumping the fluid.
This invention also provides a method of defoaming a previously formed stable foamed well treating fluid by combining a defoaming composition of this invention therewith.
It is, therefore, a principal object of the present invention to provide improved defoaming compositions and methods.
Other and further objects, features and advantages of the invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
As mentioned above, defoaming compositions are commonly utilized in a variety of fluids to prevent the fluids from forming foam with air when they are agitated, mixed or the like in the presence of air. In the treatment of wells with well treating fluids, the fluids are commonly mixed or blended in the presence of air on the surface and then pumped into the well bore. If the well treating fluids are inadvertently foamed while being mixed and pumped, adverse results can take place. For example, in completing and stimulating a well, unfoamed treating fluids are often utilized which, if foamed, would not accomplish their intended purposes or would produce less than desirable results.
Some well treating fluids are intentionally formed into stable foams on the surface in order to reduce the densities of the fluids or for other reasons. When such stable foams must be disposed of on the surface, it is often necessary to break the foams in order to efficiently dispose of the non-foamed components. While defoaming compositions and agents have been developed and used successfully heretofore, such defoaming compositions and agents generally have either been environmentally unsafe or have produced less than desirable results when utilized to break previously formed stable foams. By the present invention, improved defoaming compositions and methods are provided which are environmentally safe and also produce better defoaming results than the heretofore utilized defoaming compositions and agents.
The improved defoaming compositions of the present invention are basically comprised of polypropylene glycol, particulate hydrophobic silica and a liquid diluent. The polypropylene glycol utilized in the compositions can have a molecular weight in the range of from about 425 to about 4,000. It is preferred that the polypropylene glycol have a molecular weight at the high end of the above range, most preferably about 4,000. The polypropylene glycol is generally included in the defoaming compositions of this invention in an amount in the range of from about 20% to about 75% by weight of the compositions, most preferably about 30%.
A particulate hydrophobic silica useful in accordance with this invention is silicone oil treated precipitated silica. This hydrophobic silica functions in combination with the polypropylene glycol to defoam fluids very efficiently. The precipitated silica can be prepared by simultaneously adding sulfuric acid and sodium silicate solutions to water with agitation. The pH of the mixture during the reaction is maintained above about 9 whereby smaller particles are continuously dissolved during the precipitation of silica. As a result, uniform particle sizes are obtained. During the precipitation process, the properties of the silica can be varied by changing the ratio of reactants, the reaction time, the reaction temperature and the reaction mixture concentrations. The suspension that results from the precipitation process is filtered and dried followed by milling to reduce the size of agglomerates formed in the drying stage.
The precipitated silica is hydrophobized by spraying it with a uniform coating of silicone oil followed by heating. The quantity of silicone oil utilized is usually about 10% by weight of the precipitated silica. Particularly suitable silicone oil treated precipitated silica for use in accordance with this invention is commercially available under the trade designations SIPERNET D-11™ and SIPERNET D-13™ from the Degussa Company having a place of business in Chester, Pa. The SIPERNET D-11™ has a BET surface area of 90 square centimeters per gram while the SIPERNET D-13™ has a BET surface area of 85 square centimeters per gram. Other properties of the products are the same and are as follows: average particle size—less than 5 microns; tapped density—120 grams per liter; pH—9.5 to 11.5; moisture loss at 105° C. after 2 hours—1.5%; ignition loss after 2 hours at 1,000° C.—5%; methanol wetability—greater than about 60%; SiO
2
content—98%; and NaSO
4
content—2%.
The particulate hydrophobic silica is generally included in the defoaming compositions of this invention in an amount in the range of from about 10% to about 20% by weight of the compositions, preferably about 16%.
A variety of liquid diluents which also function as dispersion mediums for the particulate hydroph
Chatterji Jiten
Cromwell Roger S.
King Bobby J.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Roddy Craig W.
Tucker Philip
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