Green coal bed methane fracturing fluid compositions, methods of preparation and methods of use

Abstract

The invention describes improved environmentally friendly, non-toxic, CBM friendly, green fracturing compositions, methods of preparing fracturing compositions and methods of use. Importantly, the subject invention overcomes problems in the use of water-based mists as an effective fracturing composition particularly having regard to the ability of a mist to transport an effective volume of proppant into a formation. As a result, the subject technologies provide an effective economic solution to using high ratio gas fracturing compositions that can be produced in a continuous (i.e. non-batch) process without the attendant capital and operating costs of current pure gas fracturing equipment.

We claim: 
     
         1 . A fracturing fluid composition for use in fracturing a coal bed methane formation comprising:
 a non-toxic and coal bed methane (CBM) friendly liquid component for temporarily supporting a proppant within the liquid component at surface, the liquid component including:
 i) a viscosified water component including a viscosifier, the viscosified liquid component having a viscosity sufficient to temporarily support proppant admixed within the viscosified water component; and 
 ii) a breaker for relaxing the viscosity of the viscosified water component within a pre-determined period 
   wherein the non-toxic liquid component passes toxicity testing.   
     
     
         2 . The fracturing fluid composition as in  claim 1  wherein the toxicity testing is a Microtox™ test. 
     
     
         3 . The fracturing fluid composition as in  claim 2  wherein the Microtox™ test is an EC50 test. 
     
     
         4 . The fracturing fluid composition as in  claim 1  wherein the toxicity testing includes the step of monitoring changes in the level of light emission from  Vibrio fischeri  NRRL-B-11177 when challenged with the non-toxic liquid component. 
     
     
         5 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is any one of or a combination of hydroxyethyl cellulose (HEC), PAC (poly anionic cellulose) or a derivative thereof. 
     
     
         6 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is a guar gum or a derivative thereof. 
     
     
         7 . The fracturing fluid composition as in  claim 6  wherein the viscosifier is a guar gum or a derivative thereof initially suspended in a non-toxic mineral oil. 
     
     
         8 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is characterized as having zero or minimal residual solids after breaking. 
     
     
         9 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is HEC and the HEC is characterized as having zero solids. 
     
     
         10 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is HEC and is initially suspended in an isoparaffinic hydrocarbon. 
     
     
         11 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is initially a dry powder. 
     
     
         12 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is initially a dry powder and has a final concentration of 1-20 kg/m3 within the fracturing fluid composition. 
     
     
         13 . The fracturing fluid composition as in  claim 1  wherein the viscosifier is initially a dry powder and has a final concentration of 3 kg/m3 within the fracturing fluid composition. 
     
     
         14 . The fracturing fluid composition as in  claim 1  wherein the viscosified water component includes 0.1-2.0 wt % gelling agent. 
     
     
         15 . The fracturing fluid composition as in  claim 1  wherein the breaker is an enzyme breaker. 
     
     
         16 . The fracturing fluid composition as in  claim 15  wherein the enzyme breaker is hemicellulase enzyme. 
     
     
         17 . The fracturing fluid composition as in  claim 1  wherein the concentration of breaker within the liquid component is sufficient to relax the initial viscosity of the liquid component to less than 10 cP at 170 sec −1  (20° C.) within 30 minutes. 
     
     
         18 . The fracturing fluid composition as in  claim 1  wherein the concentration of breaker within the liquid component is sufficient to relax the initial viscosity of the liquid component to less than 10 cP at 170 sec −1  (20° C.) within 10 minutes. 
     
     
         19 . The fracturing fluid composition as in  claim 1  wherein the concentration of breaker is greater than 0 and less 0.05% by weight. 
     
     
         20 . The fracturing fluid composition as in  claim 1  wherein the concentration of breaker is 0.005% by weight. 
     
     
         21 . The fracturing fluid composition as in  claim 1  wherein the water component contains saline water. 
     
     
         22 . A fracturing fluid composition as in  claim 21  wherein the saline water is derived from a dewatering process. 
     
     
         23 . The fracturing fluid composition as in  claim 1  wherein the water component is fresh water. 
     
     
         24 . The fracturing fluid composition as in  claim 23  wherein the fresh water is derived from a dewatering process. 
     
     
         25 . The fracturing fluid composition as in  claim 1  further comprising a proppant admixed within the viscosified water component. 
     
     
         26 . The fracturing fluid composition as in  claim 25  wherein the mass of proppant is 0.25-5.0 times the mass of the liquid component. 
     
     
         27 . The fracturing fluid composition as in  claim 25  wherein the mass of proppant is 1.0-2.5 times the mass of the liquid component. 
     
     
         28 . The fracturing fluid composition as in  claim 1  further comprising a gas component admixed with the liquid component under high turbulence conditions sufficient to support the proppant within a combined liquid component/gas component mixture wherein the combined liquid component/gas component mixture is characterized as a mist or liquid slug. 
     
     
         29 . The fracturing fluid composition as in  claim 28  wherein the gas component is carbon dioxide, nitrogen, or a mixture of carbon dioxide and nitrogen. 
     
     
         30 . The fracturing fluid composition as in  claim 28  wherein the combined fluid/gas component mixture is 3-15 vol % liquid component and 85-97 vol % gas component exclusive of the proppant. 
     
     
         31 . The fracturing fluid composition as in  claim 1  wherein the initial viscosity of the liquid component is 15-100 centipoise (cP) at 170 sec −1  prior to mixing with a proppant or a gas component. 
     
     
         32 . The fracturing fluid composition as in  claim 1  wherein each of the viscosifier, water and breaker components are individually and collectively non-toxic. 
     
     
         33 . The fracturing fluid composition as in  claim 1  further comprising a clay control agent. 
     
     
         34 . The fracturing fluid composition as in  claim 1  further comprising a non-toxic coal bed methane friendly clay control agent. 
     
     
         35 . The fracturing fluid composition as in  claim 33  wherein the clay control agent is diallyl dimethyl ammonium chloride (DADMAC). 
     
     
         36 . The fracturing fluid composition as in  claim 1  further comprising greater than 0 and less than 1 vol % clay control agent. 
     
     
         37 . The fracturing fluid composition as in  claim 33  wherein the clay control agent is KCL or naturally occurring salts thereof. 
     
     
         38 . The fracturing fluid composition as in  claim 35  wherein the clay control agent is greater than 0 and less than 0.75% (by weight). 
     
     
         39 . The fracturing fluid composition as in  claim 1  further comprising a non-toxic buffer. 
     
     
         40 . The fracturing fluid composition as in  claim 1  wherein the non-toxic buffer is less than 1 vol %. 
     
     
         41 . The fracturing fluid composition as in  claim 39  wherein the non-toxic buffer is an organic acid. 
     
     
         42 . The fracturing fluid composition as in  claim 39  wherein the non-toxic buffer is formic acid. 
     
     
         43 . A fracturing fluid composition for use in fracturing a coal bed methane formation comprising:
 a non-toxic and coal bed methane (CBM) friendly liquid component for temporarily supporting a proppant within the liquid component at surface, the liquid component including:
 a viscosified water component including a viscosifier, the viscosified liquid component having a viscosity sufficient to temporarily support proppant admixed within the viscosified water component wherein the viscosifier is any one of or a combination of hydroxyethyl cellulose (HEC), PAC (poly anionic cellulose) or a derivative thereof; and 
 an enzyme breaker for relaxing the viscosity of the viscosified water component within a pre-determined period wherein the concentration of enzyme breaker within the liquid component is sufficient to relax the initial viscosity of the liquid component to less than 10 cP at 170 sec −1  (20° C.) within 30 minutes; 
   wherein each of the viscosifier, water and breaker are individually and collectively non-toxic.