Methods of fracturing subterranean zones to produce maximum productivity

Abstract

Methods of fracturing subterranean zones to produce maximum hydrocarbon productivity are provided. The methods are basically comprised of providing a fracturing fluid comprised of water, a gelling agent present in an amount in the range of from about 0.06% to about 0.3% by weight of the water and an inorganic salt for preventing clay swelling present in an amount in the range of from about 0.01% to about 1% by weight of the water. The fracturing fluid is introduced into the subterranean zone at a rate and pressure sufficient to form fractures and the fracturing fluid is recovered from the zone.

What is claimed is:  
     
         1 . A method of fracturing a subterranean zone whereby maximum hydrocarbon productivity therefrom results comprising the steps of: 
 (a) providing a fracturing fluid comprised of water, a gelling agent present in an amount in the range of from about 0.06% to about 0.3% by weight of said water and an inorganic salt for preventing clay swelling present in an amount in the range of from about 0.01% to about 1% by weight of said water;    (b) introducing said fracturing fluid into said subterranean zone at a rate and pressure sufficient to form one or more fractures in said zone; and    (c) recovering said fracturing fluid from said zone.    
     
     
         2 . The method of  claim 1  wherein said water in said fracturing fluid is selected from the group consisting of fresh water and salt water containing dissolved salts in no greater a concentration than 3.5% by weight of said salt water.  
     
     
         3 . The method of  claim 1  wherein said viscosity increasing gelling agent is selected from the group consisting of galactomannan gums, modified or derivatized galactomannan gums, cellulose derivatives, xanthan biopolymer, succinoglycon biopolymer, polyacrylamides and polyacrylates.  
     
     
         4 . The method of  claim 1  wherein said gelling agent is selected from the group consisting of hydroxyethylcellulose, hydroxypropylguar, guar and anionically charged guar gelling agents such as carboxymethylguar, carboxymethylhydroxypropylguar, carboxyethylguar and carboxymethylhydroxyethylcellulose.  
     
     
         5 . The method of  claim 1  wherein said gelling agent is carboxymethyl-hydroxypropylguar.  
     
     
         6 . The method of  claim 1  wherein said gelling agent is present in said fracturing fluid in an amount in the range of from about 0.18% to about 0.24% by weight of water therein.  
     
     
         7 . The method of  claim 1  wherein said inorganic salt is selected from the group consisting of potassium chloride, sodium chloride, potassium nitrate and ammonium chloride.  
     
     
         8 . The method of  claim 1  wherein said inorganic salt is potassium chloride.  
     
     
         9 . The method of  claim 1  wherein said inorganic salt is present in said fracturing fluid in an amount in the range of from about 0.1% to about 0.2% by weight of water therein.  
     
     
         10 . The method of  claim 1  wherein said fracturing fluid further comprises a cross-linking agent for cross-linking said gelling agent and increasing the viscosity of said fracturing fluid.  
     
     
         11 . The method of  claim 10  wherein said cross-linking agent is selected from the group consisting of borate releasing compounds, a source of titanium ions, a source of zirconium ions, a source of antimony ions and a source of aluminum ions.  
     
     
         12 . The method of  claim 10  wherein said cross-linking agent is present in said fracturing fluid in an amount in the range of from about 0.02% to about 0.6% by weight of water therein.  
     
     
         13 . The method of  claim 1  wherein said fracturing fluid further comprises a delayed breaker for reducing the viscosity of said fracturing fluid whereby said fracturing fluid can be recovered from said subterranean zone.  
     
     
         14 . The method of  claim 13  wherein said delayed breaker is selected from the group consisting of alkali metal and ammonium persulfates which are delayed by being encapsulated in a material which slowly releases said breaker, alkali metal chlorites, alkali metal hypochlorites and calcium hypochlorite.  
     
     
         15 . The method of  claim 13  wherein said delayed breaker is present in said fracturing fluid in an amount in the range of from about 0.001% to about 0.25% by weight of water therein.  
     
     
         16 . The method of  claim 1  wherein said fracturing fluid further comprises proppant particles suspended therein which are deposited in said one or more fractures when said viscosity of said fracturing fluid is reduced selected from the group consisting of graded sand, bauxite particles, ceramic particles, glass particles, walnut hull particles and polymer particles.  
     
     
         17 . A method of fracturing a subterranean zone whereby maximum hydrocarbon production therefrom results comprising the steps of: 
 (a) providing a fracturing fluid comprised of water, a gelling agent selected from the group consisting of anionically charged guar gelling agents present in an amount in the range of from about 0.06% to about 0.3% by weight of said water, potassium chloride for preventing clay swelling present in an amount in the range of from about 0.1% to about 1% by weight of water, a cross-linking agent for cross-linking said gelling agent selected from the group consisting of a source of zirconium ions and a borate releasing compound present in an amount in the range of from about 0.04% to about 0.3% by weight of water and a sodium chlorite breaker present in an amount in the range of from about 0.001% to about 0.25% by weight of water;    (b) introducing said fracturing fluid into said subterranean zone at a rate and pressure sufficient to form one or more fractures in said zone;    (c) allowing said fracturing fluid to break into a low viscosity fluid; and    (d) recovering said fracturing fluid from said zone.    
     
     
         18 . The method of  claim 17  wherein said anionically charged guar gelling agent is carboxymethylhydroxypropylguar.  
     
     
         19 . The method of  claim 17  wherein said cross-linking agent is a source of zirconium ions.  
     
     
         20 . The method of  claim 17  wherein said fracturing fluid further comprises proppant particles suspended therein which are deposited in said fractures when said fracturing breaks into a low viscosity fluid.  
     
     
         21 . The method of  claim 20  wherein said proppant particles are graded sand.