Fracking Fluid #1 provided an introduction to fracking fluid, its major constituents, and the generic contents of Halliburton’s CleanStim fluid. This post looks at some of the inventions involved in the "greening and cleaning" of fracking fluids.
Some Inventions Behind Clean Frack FluidsHalliburton is not the only company that is developing new fracking fluid formulations. The range of inventions is broad, spanning all of the component constituents of fracking fluids. Foodstuffs for Fracking A Halliburton invention relates to the gel used to thicken the frack fluid so that it can suspend the proppant. US 7,595,391, “Crosslinked polysaccharides and methods of making and using crosslinked polysaccharides,” was issued in September 2009 to Lewis Norman and co-inventors and assigned to Halliburton Energy Services, Inc. The invention,
relates to methods of crosslinking polysaccharides to form crosslinked polysaccharides, and more particularly, to crosslinked polysaccharides that may be incorporated in fluids useful in, for example, applications requiring a crosslinked viscoelastic gel. In one embodiment, the present invention provides a method of crosslinking a polysaccharide comprising the steps of: providing a metal coordinating group having a reactive site, derivatizing a polysaccharide with the metal coordinating group to produce a derivatized polysaccharide having bidentate ligands, and crosslinking the derivatized polysaccharide having bidentate ligands with a metal ion to form a metal ligand coordination complex.
The inventors explain that "Polysaccharides are carbohydrates in which tens, hundreds, or even thousands of simple sugars are linked together. … Cellulose, starch, and various galactomannans are some of the most-widely occurring polysaccharides. … If the polysaccharide is crosslinked, these viscosified treatment fluids can approach near zero particle settling rates." They prefer that “the polysaccharide is selected from the group consisting of guar, xanthan, locust bean gum, hydroxy ethyl and hydroxy propyl derivatives of gums, hydroxyethylcellulose, and combinations thereof.” Guar gum is derived from guar beans and is commonly used as a thickener in food products, and in watercolor paints. Xanthan gum is found in salad dressings, sauces, frozen foods, beverages, egg substitutes, cosmetics, and fake blood. Locust bean gum is derived from the seeds of the carob tree and is commonly used to thicken ice cream and cream cheese, and serves as a chocolate substitute.
Fillers for Fracking
Another constituent of hydraulic fracturing fluid is the propping agent. Phillip Nguyen and co-inventors were granted US 7,281,581, “Methods of hydraulic fracturing and of propping fractures in subterranean formations” in October 2007. It was assigned to Halliburton Energy Services, Inc.
As described in the abstract, the invention provides a "method of propping at least one fracture in a subterranean formation, that comprises forming a plurality of proppant aggregates, each proppant aggregate comprising a binding fluid and a filler material, and introducing the plurality of proppant aggregates into the at least one fracture, is provided. Methods of fracturing a subterranean formation also are provided." A filler material - what is that? Claim 20 reveals that,
the filler material is selected from the group consisting of: a sand, a bauxite, a ceramic material, a glass material, a polymer material, a nut shell piece, a seed shell piece, a cured resinous particulate comprising nut shell pieces, a cured resinous particulate comprising seed shell pieces, a fruit pit piece, a cured resinous particulate comprising fruit pit pieces, wood, a composite particulate, a lightweight particulate, a microsphere plastic bead, a ceramic microsphere, a glass microsphere, a man-made fiber, a cement, fly ash, carbon black powder, and a combination thereof.
Nut shells, seed shells, fruit pits, wood, fibers, carbon black - it doesn’t get much greener than that.
Plant Parts for Fracking
Boyce Burts, Jr. was granted US 6,016,871, Hydraulic fracturing additive, hydraulic fracturing treatment fluid made therefrom, and method of hydraulically fracturing a subterranean formation, in January 2000. That seems like a l-o-o-o-n-g time ago. Claim 1 is a succinct explanation of the hydraulic fracturing process:
A method for hydraulically fracturing a subterranean hydrocarbon bearing formation below an earthen surface in fluid communication with a wellbore comprising:(a) providing a hydraulic fracturing additive comprising a dry mixture of water soluble crosslinkable polymer, a crosslinking agent, and a reinforcing material selected from among fibers and comminuted plant materials; (b) contacting the hydraulic fracturing additive with water or an aqueous solution to form a hydraulic fracturing fluid; and (c) injecting the hydraulic fracturing fluid into said formation via said wellbore at a pressure sufficient to hydraulically fracture said formation.
Later claims provide details on the reinforcing and additive materials. These are:
|bamboo||cotton linters||peat moss fibers||straw|
|bark||cotton seed stems||peat moss fibers||sugar cane|
|cellophane||crude pectate pulp||rice bran||sunflower seed stems|
|cork||dehydrated vegetable matter||rice bran||wheat|
|corn cob chaff portion||flax||rice straw||wheat stems|
|corn cob ground woody ring portion||flax stems||rice tips||whole ground corn cobs|
|corn cob light density pith core||maize stems||rye grass stems||wood|
|corn stalks||millet stems||sawdust||wool|
|Mixtures of comminuted rice fraction with|
|wood fiber or almond hulls|
|corn cob fraction|
|corn cob fraction and at least one of wood fiber, nut shells, and paper|
|Nut and Seed Shells or Hulls of|
|cocoa bean||linseed peanut||walnut|
On second thought, perhaps this one is more green and clean than the '581 patent.
Water comprises about 95% of hydraulic fracturing fluid. James Mothersbaugh and Gene Hancock recognize the importance of controlling the quality of source water and flowback (the fluid that is pumped back to the surface after the fractures are created) in their patent US 8,347,960, Method for using electrocoagulation in hydraulic fracturing, issued in January 2013 and assigned to Water Tectonics, Inc.
Mothersbaugh and Hancok propose to use electrocoagulation to cause impurities in the source water or flowback to coagulate (or flocculate), settle to the bottom of settling tanks, and be removed for disposal. Their abstract says they provide a,
method of improving natural gas release from a well via an enhanced hydraulic fracturing operation. The method includes capturing or retrieving the flow back from the well following the fracturing operation. The flow back or other source water is introduced to an electrocoagulation ("EC") treatment process. EC treatment separates the water from other fracturing fluid components in the flow back and also removes bacteria and other contaminants. Thereafter, the EC-treated fluid is recycled for subsequent fracturing operations. The process may also be used to treat all source water, including fresh water delivered to the well before it is used as a fracturing fluid.
The inventors are not the first to apply EC (electrocoagulation, not Eric Clapton) to the fracking process. We looked at other fracking treatment technologies last year, including one using the EC process (see especially US 7,731,854 in our March 15, 2012 post. Interestingly, this same process can be used to produce an organic fertilizer from liquid manure.
A very useful site for discovering the chemicals used in specific wells around the country is FracFocus.org, a national hydraulic fracturing chemical registry managed by the Ground Water Protection Council and Interstate Oil and Gas Compact Commission. Ten states presently use the site as their official state chemical disclosure means. The registry is used by 452 companies as of early February 2013.