Methods of treating subterranean formations using low-molecular-weight fluids

Abstract

The present invention relates to systems and methods useful in subterranean treatment operations. More particularly, the present invention relates to systems and methods for treating subterranean formations using low-molecular-weight fluids. Examples of methods of the present invention include methods of treating a subterranean formation intersected by a wellbore; methods of enhancing production from multiple subterranean formations penetrated by a well bore during a single trip through the well bore; methods of enhancing production, in real time, from multiple subterranean formations penetrated by a well bore during a single trip through the well bore; and methods of reducing the cost of enhancing production from multiple formations penetrated by a well bore by stimulating multiple formations, on a single trip through the well bore, with a fluid that minimizes damage to the formation.

1 . A method of treating a subterranean formation intersected by a wellbore comprising: 
 lowering a work string having a first packer apparatus connected to a lower end of the work string to a desired location in the wellbore, the work string being communicated with the wellbore through a longitudinal opening defined by the first packer apparatus, the first packer apparatus comprising: 
 a packer mandrel; and  
 an expandable packer element disposed about the packer mandrel;  
   compressing the expandable packer element by lowering the packer mandrel relative to the expandable packer element thereby expanding the packer element outward to engage and seal a casing in the wellbore below the formation, wherein the compressing step seals the longitudinal opening to prevent communication therethrough;    displacing a low-molecular-weight fluid down the work string and into the wellbore through a flow port defined in the work string above the first packer apparatus, so as to create or enhance at least one fracture in the subterranean formation;    unsealing the longitudinal opening after the displacing step to communicate a portion of the wellbore above the expandable packer element with a portion of the wellbore below the expandable packer element through the longitudinal opening to equalize a pressure in the wellbore above and below the expandable packer element; and    disengaging the expandable packer element from the casing.    
   
   
       2 . The method of  claim 1  wherein the work string has a second packer apparatus connected therein, the second packer apparatus being located above the formation, the method further comprising: actuating the second packer apparatus to seal the wellbore above the formation.  
   
   
       3 . The method of  claim 1  further comprising: 
 moving the work string to a second desired location in the wellbore;    compressing the expandable packer element by lowering the packer mandrel relative to the expandable packer element to seal the casing and seal the longitudinal opening in the first packer apparatus after the moving step;    displacing a second fluid down the work string into the wellbore above the first packer apparatus; and    reopening the longitudinal opening to equalize the pressure above and below the expandable packer element of the first packer apparatus after the step of displacing a second fluid down the work string.    
   
   
       4 . The method of  claim 1  wherein the first packer apparatus further comprises: a drag sleeve disposed about the packer mandrel, the drag sleeve being slidable relative to the packer mandrel; and an equalizing valve connected to a lower end of the drag sleeve and extending upwardly therefrom into the packer mandrel.  
   
   
       5 . The method of  claim 1  further comprising the step of moving the packer apparatus to another formation adjacent the well and repeating the step of displacing a low-molecular-weight fluid down the work string and into the wellbore to create or extend at least one fracture in the formation.  
   
   
       6 . The method of  claim 1  wherein the equalizing valve may be moved between the open and closed positions by reciprocation of the work string.  
   
   
       7 . The method of  claim 1  wherein the equalizing valve defines a generally cylindrical outer surface, and wherein in the closed position the generally cylindrical outer surface sealingly engages an inner surface of the packer mandrel.  
   
   
       8 . The method of  claim 1  wherein an interior of the work string is in communication with the wellbore through flow ports defined in the work string above the packer element so that a fluid may be communicated into the formation through the flow ports when the equalizing valve is in the closed position, and wherein the portion of the wellbore above the packer element is in communication with the portion of the wellbore below the packer element through the flow ports, the packer mandrel, and the drag sleeve into the wellbore when the equalizing valve is in the open position in order to equalize the pressure in the wellbore above and below the packer element.  
   
   
       9 . The method of  claim 1  wherein the equalizing valve moves from the open position to the closed position when the packer apparatus is actuated to expand the packer element to sealingly engage the wellbore.  
   
   
       10 . The method of  claim 1  wherein the longitudinal opening has a reduced diameter portion, wherein the equalizing valve comprises a generally tubular element disposed in the longitudinal opening, and wherein the equalizing valve is moved between the open and closed positions by moving the equalizing valve in and out of the reduced diameter portion to seal and open the longitudinal opening.  
   
   
       11 . The method of  claim 1  wherein the equalizing valve moves between the open and the closed positions as the packer apparatus is moved between the set and unset positions.  
   
   
       12 . The method of  claim 1  wherein the equalizing valve may be moved from the closed position to the open position by pulling upward on the work string.  
   
   
       13 . The method of  claim 1  wherein the low-molecular-weight fluid has an average molecular weight in the range of from about 100,000 to about 250,000.  
   
   
       14 . The method of  claim 1  wherein the low-molecular-weight fluid has a viscosity of at least about 2 cP, where the viscosity is measured at about 25° C.  
   
   
       15 . The method of  claim 1  wherein the low-molecular-weight fluid comprises an acid system.  
   
   
       16 . The method of  claim 15  wherein the acid system comprises a viscosifier.  
   
   
       17 . The method of  claim 16  wherein the viscosifier is present in the acid system in an amount in the range of from about 0.002% to about 0.035% by volume.  
   
   
       18 . The method of  claim 16  wherein the viscosifier comprises an emulsifier or a surfactant.  
   
   
       19 . The method of  claim 15  wherein the acid system comprises a hydrochloric acid based delayed carbonate acid system.  
   
   
       20 . The method of  claim 15  wherein the acid system comprises a hydrofluoric acid based delayed carbonate acid system.  
   
   
       21 . The method of  claim 1  wherein the low-molecular-weight fluid comprises water.  
   
   
       22 . The method of  claim 1  wherein the low-molecular-weight fluid comprises water, a substantially fully hydrated depolymerized polymer, and a crosslinking agent.  
   
   
       23 . The method of  claim 22  wherein the substantially fully hydrated depolymerized polymer is a depolymerized polysaccharide.  
   
   
       24 . The method of  claim 22  wherein the substantially fully hydrated depolymerized polymer is selected from the group consisting of hydroxypropylguar, carboxymethylhydroxypropylguar, carboxymethylguar, hydroxyethylguar, and carboxymethylhydroxyethylguar.  
   
   
       25 . The method of  claim 22  wherein the substantially fully hydrated depolymerized polymer is present in the low-molecular-weight fluid in an amount in the range of from about 0.2% to about 5% by weight of the water therein.  
   
   
       26 . The method of  claim 22  wherein the crosslinking agent is a boron-based compound, ulexite, colemanite, a compound that comprises zirconium IV ions, a compound that comprises titanium IV ions, an aluminum compound, or a compound that comprises antimony ions.  
   
   
       27 . The method of  claim 22  wherein the crosslinking agent is present in the low-molecular-weight fluid in an amount in the range of from about 50 ppm to about 5000 ppm active crosslinker.  
   
   
       28 . The method of  claim 1  wherein the low-molecular-weight fluid further comprises a pH-adjusting compound, a delayed delinker, a buffer, a surfactant, a clay stabilizer, a fluid loss control agent, a scale inhibitor, a demulsifier, a bactericide, a breaker, an activator, or a mixture thereof.  
   
   
       29 . A method of reducing the cost of enhancing production from multiple formations penetrated by a well bore by stimulating multiple formations, on a single trip through the well bore, with a fluid that minimizes damage to the formation comprising: 
 lowering a work string having a first packer apparatus connected to a lower end of the work string to a desired location in the wellbore, the work string being communicated with the wellbore through a longitudinal opening defined by the first packer apparatus, the first packer apparatus comprising: 
 a packer mandrel; and  
 an expandable packer element disposed about the packer mandrel;  
   compressing the expandable packer element by lowering the packer mandrel relative to the expandable packer element thereby expanding the packer element outward to engage and seal a casing in the wellbore below the formation, wherein the compressing step seals the longitudinal opening to prevent communication therethrough;    displacing a low-molecular-weight fluid down the work string and into the wellbore through a flow port defined in the work string above the first packer apparatus, so as to create or enhance at least one fracture in the subterranean formation, the low-molecular-weight fluid having the capability of enhancing the regain permeability of the formation;    unsealing the longitudinal opening after the displacing step to communicate a portion of the wellbore above the expandable packer element with a portion of the wellbore below the expandable packer element through the longitudinal opening to equalize a pressure in the wellbore above and below the expandable packer element;    disengaging the expandable packer element from the casing; and    moving the packer apparatus to another formation in the well bore and repeating the step of displacing a low-molecular-weight fluid down the work string and into the wellbore to create or extend at least one fracture in the formation.    
   
   
       30 . The method of  claim 29  wherein the low-molecular-weight fluid has an average molecular weight in the range of from about 100,000 to about 250,000.  
   
   
       31 . The method of  claim 29  wherein the low-molecular-weight fluid has a viscosity of at least about 2 cP, where the viscosity is measured at about 25° C.  
   
   
       32 . The method of  claim 29  wherein the low-molecular-weight fluid comprises an acid system.  
   
   
       33 . The method of  claim 32  wherein the acid system comprises a viscosifier.  
   
   
       34 . The method of  claim 33  wherein the viscosifier is present in the acid system in an amount in the range of from about 0.002% to about 0.035% by volume.  
   
   
       35 . The method of  claim 33  wherein the viscosifier comprises an emulsifier or a surfactant.  
   
   
       36 . The method of  claim 32  wherein the acid system comprises a hydrochloric acid based delayed carbonate acid system.  
   
   
       37 . The method of  claim 32  wherein the acid system comprises a hydrofluoric acid based delayed carbonate acid system.  
   
   
       38 . The method of  claim 29  wherein the low-molecular-weight fluid comprises water.  
   
   
       39 . The method of  claim 29  wherein the low-molecular-weight fluid comprises water, a substantially fully hydrated depolymerized polymer, and a crosslinking agent.  
   
   
       40 . The method of  claim 39  wherein the substantially fully hydrated depolymerized polymer is a depolymerized polysaccharide.  
   
   
       41 . The method of  claim 39  wherein the substantially fully hydrated depolymerized polymer is selected from the group consisting of hydroxypropylguar, carboxymethylhydroxypropylguar, carboxymethylguar, hydroxyethylguar, and carboxymethylhydroxyethylguar.  
   
   
       42 . The method of  claim 39  wherein the substantially fully hydrated depolymerized polymer is present in the low-molecular-weight fluid in an amount in the range of from about 0.2% to about 5% by weight of the water therein.  
   
   
       43 . The method of  claim 39  wherein the crosslinking agent is a boron-based compound, ulexite, colemanite, a compound that comprises zirconium IV ions, a compound that comprises titanium IV ions, an aluminum compound, or a compound that comprises antimony ions.  
   
   
       44 . The method of  claim 39  wherein the crosslinking agent is present in the low-molecular-weight fluid in an amount in the range of from about 50 ppm to about 5000 ppm active crosslinker.  
   
   
       45 . The method of  claim 29  wherein the low-molecular-weight fluid further comprises a pH-adjusting compound, a delayed delinker, a buffer, a surfactant, a clay stabilizer, a fluid loss control agent, a scale inhibitor, a demulsifier, a bactericide, a breaker, an activator, or a mixture thereof.  
   
   
       46 . A method of enhancing production, in real time, from multiple subterranean formations penetrated by a well bore during a single trip through the well bore, comprising 
 lowering a work string having a first packer apparatus connected to a lower end of the work string to a desired location in the wellbore, the work string being communicated with the wellbore through a longitudinal opening defined by the first packer apparatus, the first packer apparatus comprising: 
 a packer mandrel; and  
 an expandable packer element disposed about the packer mandrel;  
   compressing the expandable packer element by lowering the packer mandrel relative to the expandable packer element thereby expanding the packer element outward to engage and seal a casing in the wellbore below the formation, wherein the compressing step seals the longitudinal opening to prevent communication therethrough;    displacing a low-molecular-weight fluid down the work string and into the wellbore through a flow port defined in the work string above the first packer apparatus, so as to create or extend at least one fracture in the subterranean formation, the low-molecular-weight fluid having the capability of enhancing the regain permeability of the formation;    unsealing the longitudinal opening after the displacing step to communicate a portion of the wellbore above the expandable packer element with a portion of the wellbore below the expandable packer element through the longitudinal opening to equalize a pressure in the wellbore above and below the expandable packer element;    determining, in real time, at least one parameter related to the creation or enhancement of the at least one fracture;    disengaging the expandable packer element from the casing; and    moving the packer apparatus to another formation adjacent the well and repeating the step of displacing a low-molecular-weight fluid down the work string and into the wellbore to create or extend at least one fracture in the formation.    
   
   
       47 . The method of  claim 46  wherein the step of determining, in real time, at least one parameter related to the creation or enhancement of the at least one fracture comprises determining, in real time, that at least one fracture therein has been created or enhanced to a desired extent.  
   
   
       48 . The method of  claim 47  wherein the step of relocating the tool assembly within the well bore to another desired location in the same, or different, formation is performed after the step of determining, in real time, that at least one fracture therein has been created or enhanced to a desired extent.  
   
   
       49 . The method of  claim 46  further comprising performing a remediative step after the step of determining, in real time, at least one parameter related to the creation or enhancement of the at least one fracture.  
   
   
       50 . The method of  claim 49  wherein the remediative step comprises reducing the concentration of a proppant present in the low-molecular-weight fluid.  
   
   
       51 . The method of  claim 49  wherein the remediative step comprises reducing the viscosity of the low-molecular-weight fluid.  
   
   
       52 . The method of  claim 46  wherein the low-molecular-weight fluid has an average molecular weight in the range of from about 100,000 to about 250,000.  
   
   
       53 . The method of  claim 46  wherein the low-molecular-weight fluid has a viscosity of at least about 2 cP, where the viscosity is measured at about 25° C.  
   
   
       54 . The method of  claim 46  wherein the low-molecular-weight fluid comprises an acid system.  
   
   
       55 . The method of  claim 54  wherein the acid system comprises a viscosifier.  
   
   
       56 . The method of  claim 55  wherein the viscosifier is present in the acid system in an amount in the range of from about 0.002% to about 0.035% by volume.  
   
   
       57 . The method of  claim 55  wherein the viscosifier comprises an emulsifier or a surfactant.  
   
   
       58 . The method of  claim 54  wherein the acid system comprises a hydrochloric acid based delayed carbonate acid system or a hydrofluoric acid based delayed carbonate acid system.  
   
   
       59 . The method of  claim 46  wherein the low-molecular-weight fluid comprises water.  
   
   
       60 . The method of  claim 46  wherein the low-molecular-weight fluid comprises water, a substantially fully hydrated depolymerized polymer, and a crosslinking agent.  
   
   
       61 . The method of  claim 60  wherein the substantially fully hydrated depolymerized polymer is a depolymerized polysaccharide.  
   
   
       62 . The method of  claim 60  wherein the substantially fully hydrated depolymerized polymer is selected from the group consisting of hydroxypropylguar, carboxymethylhydroxypropylguar, carboxymethylguar, hydroxyethylguar, and carboxymethylhydroxyethylguar.  
   
   
       63 . The method of  claim 60  wherein the substantially fully hydrated depolymerized polymer is present in the low-molecular-weight fluid in an amount in the range of from about 0.2% to about 5% by weight of the water therein.  
   
   
       64 . The method of  claim 60  wherein the crosslinking agent is a boron-based compound, ulexite, colemanite, a compound that comprises zirconium IV ions, a compound that comprises titanium IV ions, an aluminum compound, or a compound that comprises antimony ions.  
   
   
       65 . The method of  claim 60  wherein the crosslinking agent is present in the low-molecular-weight fluid in an amount in the range of from about 50 ppm to about 5000 ppm active crosslinker.  
   
   
       66 . The method of  claim 46  wherein the low-molecular-weight fluid further comprises a pH-adjusting compound, a delayed delinker, a buffer, a surfactant, a clay stabilizer, a fluid loss control agent, a scale inhibitor, a demulsifier, a bactericide, a breaker, an activator, or a mixture thereof.  
   
   
       67 . A method of enhancing production from multiple subterranean formations penetrated by a well bore during a single trip through the well bore, comprising 
 lowering a work string having a first packer apparatus connected to a lower end of the work string to a desired location in the wellbore, the work string being communicated with the wellbore through a longitudinal opening defined by the first packer apparatus, the first packer apparatus comprising: 
 a packer mandrel; and  
 an expandable packer element disposed about the packer mandrel;  
   compressing the expandable packer element by lowering the packer mandrel relative to the expandable packer element thereby expanding the packer element outward to engage and seal a casing in the wellbore below the formation, wherein the compressing step seals the longitudinal opening to prevent communication therethrough;    displacing a low-molecular-weight fluid down the work string and into the wellbore through a flow port defined in the work string above the first packer apparatus, so as to create or extend at least one fracture in the subterranean formation, the low-molecular-weight fluid having the capability of enhancing the regain permeability of the formation;    unsealing the longitudinal opening after the displacing step to communicate a portion of the wellbore above the expandable packer element with a portion of the wellbore below the expandable packer element through the longitudinal opening to equalize a pressure in the wellbore above and below the expandable packer element;    disengaging the expandable packer element from the casing; and    moving the packer apparatus to another formation adjacent the well and repeating the step of displacing a low-molecular-weight fluid down the work string and into the wellbore to create or extend at least one fracture in the formation.    
   
   
       68 . The method of  claim 67  wherein the low-molecular-weight fluid has an average molecular weight in the range of from about 100,000 to about 250,000.  
   
   
       69 . The method of  claim 67  wherein the low-molecular-weight fluid has a viscosity of at least about 2 cP, where the viscosity is measured at about 25° C.  
   
   
       70 . The method of  claim 67  wherein the low-molecular-weight fluid comprises an acid system.  
   
   
       71 . The method of  claim 70  wherein the acid system comprises a viscosifier.  
   
   
       72 . The method of  claim 71  wherein the viscosifier is present in the acid system in an amount in the range of from about 0.002% to about 0.035% by volume.  
   
   
       73 . The method of  claim 71  wherein the viscosifier comprises an emulsifier or a surfactant.  
   
   
       74 . The method of  claim 70  wherein the acid system comprises a hydrochloric acid based delayed carbonate acid system or a hydrofluoric acid based delayed carbonate acid system.  
   
   
       75 . The method of  claim 67  wherein the treatment fluid comprises water.  
   
   
       76 . The method of  claim 67  wherein the treatment fluid comprises water, a substantially fully hydrated depolymerized polymer, and a crosslinking agent.  
   
   
       77 . The method of  claim 76  wherein the substantially fully hydrated depolymerized polymer is a depolymerized polysaccharide.  
   
   
       78 . The method of  claim 76  wherein the substantially fully hydrated depolymerized polymer is selected from the group consisting of hydroxypropylguar, carboxymethylhydroxypropylguar, carboxymethylguar, hydroxyethylguar, and carboxymethylhydroxyethylguar.  
   
   
       79 . The method of  claim 76  wherein the substantially fully hydrated depolymerized polymer is present in the low-molecular-weight fluid in an amount in the range of from about 0.2% to about 5% by weight of the water therein.  
   
   
       80 . The method of  claim 76  wherein the crosslinking agent is a boron-based compound, ulexite, colemanite, a compound that comprises zirconium IV ions, a compound that comprises titanium IV ions, an aluminum compound, or a compound that comprises antimony ions.  
   
   
       81 . The method of  claim 76  wherein the crosslinking agent is present in the low-molecular-weight fluid in an amount in the range of from about 50 ppm to about 5000 ppm active crosslinker.  
   
   
       82 . The method of  claim 67  wherein the low-molecular-weight fluid further comprises a pH-adjusting compound, a delayed delinker, a buffer, a surfactant, a clay stabilizer, a fluid loss control agent, a scale inhibitor, a demulsifier, a bactericide, a breaker, an activator, or a mixture thereof.