Wells – Processes – Placing fluid into the formation
Reexamination Certificate
2002-03-08
2002-09-24
Suchfield, George (Department: 3672)
Wells
Processes
Placing fluid into the formation
C166S309000, C507S202000, C507S922000, C507S924000
Reexamination Certificate
active
06454008
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to foamed fracturing fluids, additives for foaming the fracturing fluids and methods of using the fracturing fluids.
2. Description of the Prior Art
Viscous gelled fracturing fluids are commonly utilized in the hydraulic fracturing of subterranean zones penetrated by well bores to increase the production of hydrocarbons from the subterranean zones. That is, a viscous fracturing fluid is pumped through the well bore into a subterranean zone to be stimulated at a rate and pressure such that fractures are formed and extended into the subterranean zone. The fracturing fluid also carries particulate proppant material, e.g., graded sand, into the formed fractures. The proppant material is suspended in the viscous fracturing fluid so that the proppant material is deposited in the fractures when the viscous fracturing fluid is broken and recovered. The proppant material functions to prevent the fractures from closing whereby conductive channels are formed through which produced fluids can flow to the well bore.
After the viscous fracturing fluid has been pumped into a subterranean zone in a formation and fracturing of the zone has taken place, the fracturing fluid is removed from the formation to allow produced hydrocarbons to flow through the created fractures. Generally, the removal of the viscous fracturing fluid is accomplished by converting the fracturing fluid into a low viscosity fluid. This has been accomplished by adding a delayed breaker, i.e., a viscosity reducing agent, to the fracturing fluid prior to pumping it into the subterranean zone. Examples of delayed breakers that can be used include, but are not limited to, enzymes, acids and oxidizing agents.
In carrying out hydraulic fracturing, the fracturing fluids must often be lightweight to prevent excessive hydrostatic pressure from being exerted on subterranean formations penetrated by the well bore. As a result, a variety of lightweight fracturing fluids have heretofore been developed and used including foamed fracturing fluids.
Foamed fracturing fluids have heretofore included various surfactants known as foaming and foam stabilizing agents for facilitating the foaming and stabilization of the foam produced when a gas is mixed with the fracturing fluid. However, the foaming and stabilizing surfactants have not met complete environmental requirements. That is, when the foaming and stabilizing surfactants find their way into water in the environment, they do not fully degrade which can result in interference with aquatic life cycles.
Thus, there are needs for improved foamed fracturing fluids, improved fracturing fluid foaming and stabilizing additives which degrade completely in the environment and are harmless thereto and improved methods of utilizing the foamed fracturing fluids.
SUMMARY OF THE INVENTION
The present invention provides improved foamed fracturing fluids, improved foaming additives for foaming and stabilizing the fracturing fluids which are harmless to the environment and methods of using the improved foamed fracturing fluids which meet the needs described above and overcome the deficiencies of the prior art. The improved foamed fracturing fluids for forming fractures in subterranean zones are basically comprised of water, a gelling agent for forming the water into gelled water and increasing the viscosity thereof, sufficient gas to form a foam and an effective amount of an environmentally harmless additive for foaming and stabilizing the gelled water comprised of hydrolyzed keratin.
The gelled water fracturing fluid foaming and stabilizing additive of this invention which is harmless to the environment is hydrolyzed keratin. The additive is preferably predissolved in water to form an aqueous solution which is added to a fracturing fluid to be foamed along with a gas for foaming the fracturing fluid.
The methods of the present invention for fracturing subterranean zones penetrated by well bores are basically comprised of the following steps. A foamed fracturing fluid comprised of water, a gelling agent for forming the water into gelled water and thereby increasing the viscosity of the water, sufficient gas to form a foam and an effective amount of an additive for foaming and stabilizing the gelled water comprised of hydrolyzed keratin. Thereafter, the subterranean zone is contacted with the foamed fracturing fluid under conditions effective to create at least one fracture therein.
The objects, features and advantages of the present 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
The improved foamed fracturing fluids of this invention are useful for fracturing subterranean zones penetrated by well bores to increase the production of hydrocarbons therefrom. The foamed fracturing fluids are basically comprised of water, a gelling agent for forming the water into gelled water and increasing the viscosity thereof, sufficient gas to form a foam and an effective amount of an environment harmless additive for foaming and stabilizing the gelled water comprised of hydrolyzed keratin.
The water utilized for forming the foamed fracturing fluid of this invention can be fresh water or salt water. The term “salt water” is used herein to mean unsaturated salt solutions and saturated salt solutions including brines and seawater. The gelling agent is added to the water for forming the water into gelled water and increasing the viscosity thereof. A variety of gelling agents can be used including natural or derivatized polysaccharides which are soluble, dispersible or swellable in an aqueous liquid to yield viscosity to the aqueous liquid. One group, for example, of polysaccharides which are suitable for use in accordance with the present invention includes galactomannan gums such as gum arabic, gum ghatti, gum karaya, tamarind gum, tragacanth gum, guar gum, locust beam gum and the like. Modified gums such as carboxyalkyl derivatives, like carboxymethylguar and hydroxyalkyl derivatives, like hydroxypropylguar can also be employed. Doubly derivatized gums such as carboxymethylhydroxypropylguar can also be used.
Modified celluloses and derivatives thereof can also be employed as gelling agents in accordance with the present invention. Examples of water-soluble cellulose ethers which can be used include, but are not limited to, carboxymethylcellulose, carboxymethylhydroxyethylcellulose, hydroxyethylcellulose, methylhydroxypropylcellulose, methylcellulose, ethylcellulose, propylcellulose, ethylcarboxymethylcellulose, methylethylcellulose, hydroxypropylmethylcellulose and the like. Of these, hydroxyethylcellulose and carboxymethylhydroxyethylcellulose are preferred. The most preferred cellulose derivative is hydroxyethylcellulose grafted with vinyl phosphonic acid as described in U.S. Pat. No. 5,067,565 issued on Nov. 26, 1991 to Holtmyer et al., the disclosure of which is incorporated herein by reference.
Other gelling agents which can be used include, but are not limited to, biopolymers such as xanthan gum, welan gum and a biopolymer commercially available from Halliburton Energy Services of Duncan, Ok. under the tradename “Flo-Back™”. Of these, xanthan biopolymer is preferred.
Additional gelling agents include water dispersible hydrophillic organic polymers having molecular weights greater than 100,000 such as polyacrylamide and polymethacrylamide wherein about 5% to about 75% of the carboxamides are hydrolyzed to carboxyl groups and a copolymer of about 5% to about 70% by weight acrylic acid or methacrylic acid copolymerized with acrylamide or methacrylamide. These water dispersible organic hydrophillic polymers can be cross-linked with a cross-linking composition comprising water, a zirconium compound having a valence of 4
+
, an alpha-hydroxy acid and an amine compound as more fully described in U.S. Pat. No. 4,524,829 issued to Hanlon et al. on Jun. 25, 1985 which is incorporated herein by reference.
Still ot
Chatterji Jiten
Crook Ron
King Karen L.
Dougherty, Jr. C. Clark
Halliburton Energy Service,s Inc.
Kent Robert A.
Suchfield George
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