Method for sealing lost circulation zones

Abstract

Disclosed is a method of reducing lost circulation, sealing lost circulation zones, and stabilizing weak formations, using copolymers of ethylene acrylic or ethylene methacrylic acid, or the single valence ionomers thereof, characterized as low density, solid at ambient temperature, reactive in selected temperature ranges, ductile, and able to adhere to rock and to each other to form ionomers in situ, wherein said copolymers are optionally used in combination with other solid agents, and wherein the treatment of said zones can be further enhanced by particle sizing and by blending into the treatment mixture multivalent alkaline earth and/or transition metals to provide optimum properties for the resulting ionomers given formation temperatures, conditions, and compositions.

1 . A method of treating a borehole/wellbore penetrating an subterranean formation which comprises: 
 a) mixing one or more copolymers selected from ethylene acrylic acid, ethylene methacrylic acid, or any single valence ionomer of ethylene acrylic acid or ethylene methacrylic acid, individually or in combination, and optionally other solids and additives, in a wellbore fluid selected from drilling fluid and remedial fluid, and circulating in the wellbore;    b) temporarily discontinuing circulation of fluid in the wellbore; and    c) allowing the wellbore to remain static for a period of time sufficient to cause an increase in the temperature of the wellbore;    d) thereby causing said copolymer(s) or ionomers thereof to melt and react with the formation and any other solids in the treatment, thus forming a cohesive mass that will adhere to the formation surfaces.    
   
   
       2 . The method of  claim 1  further comprising the method is utilized for one or more of the following: 
 reducing lost circulation of drilling fluid; sealing lost circulation zones; sealing a natural fissure or fracture, induced fissure or fracture, vug, fault or other opening existing in the zone of lost circulation; and treating weak zones of the formation to increase stability.    
   
   
       3 . The method of  claim 1  further comprising the copolymers and/or ionomers are utilized as solid particles and the treatment method is enhanced by particle sizing.  
   
   
       4 . The method of  claim 1  further comprising the treatment method is enhanced by selecting acid numbers of the copolymers and/or ionomers for their properties at particular temperatures.  
   
   
       5 . The method of  claim 2  wherein the method is used to treat a zone of lost circulation further comprising: 
 a) Circulating said copolymers and/or ionomers in the wellbore in the zone of lost circulation;    b) Temporarily discontinuing circulation of fluid in the wellbore; and    c) Allowing the wellbore to remain static for a period of time sufficient to cause an increase in the temperature of the wellbore;    d) Thereby causing said copolymer(s) or ionomer(s) thereof to melt and react with the formation and any other solids in the treatment, thus forming a cohesive mass that will adhere to the formation surfaces in the zone of lost circulation.    
   
   
       6 . The method of  claim 2  wherein the method is utilized to seal a natural fissure or fracture, induced fissure or fracture, vug, fault or other opening existing in the zone of lost circulation further comprising: 
 a) Injecting said treatment mixture into a natural fissure or fracture, induced fissure or fracture, vug, fault or other opening existing in the zone of lost circulation;    b) Temporarily discontinuing injection of fluid in the wellbore; and    c) Allowing the wellbore to remain static for a period of time sufficient to cause an increase in the temperature of the wellbore, fracture, fissure, vug or fault;    d) Thereby causing said copolymer(s) to melt and react with the formation and any other solids in the treatment, thus forming a cohesive mass that adheres to the formation surfaces of the natural fissure or fracture, induced fissure or fracture, vug, fault or other opening existing in the zone of lost circulation.    
   
   
       7 . The method of  claim 2  wherein the method is utilized to strengthen a weak or unstable zone in the wellbore further comprising: 
 a) circulating said copolymers and/or ionomers in the wellbore in the zone of weakness or instability;    b) temporarily discontinuing circulation of fluid the wellbore;    c) allowing the wellbore to remain static for a period of time sufficient to cause an increase in the temperature of the wellbore; and    d) thereby causing said copolymer(s) or ionomer(s) thereof to melt and react with the formation and any other solids in the treatment, thus forming a cohesive mass that will adhere to the formation surfaces in the zone of weakness or instability.    
   
   
       8 . The method of  claim 1  wherein the single valence ionomers are single valence metal salt ionomers.  
   
   
       9 . The method of  claim 8  wherein the single valence metal salt ionomers are selected from single valence ionomers formed by reaction of the acidic groups on the copolymer(s) with alkaline salts of sodium, potassium, and lithium, or ammonia/ammonium (NH 3 /NH 4   + ).  
   
   
       10 . The method of  claim 4  wherein the copolymers have acid numbers in the range of about 20 to 180.  
   
   
       11 . The method of  claim 10  further comprising the wellbore has a temperature in the range of about 85° C. to 120° C. and the copolymers employed have acid numbers in the range of 20 to 80.  
   
   
       12 . The method of  claim 10  further comprising the wellbore has a temperature in the range of less than 65° C. and the copolymers employed have acid numbers in the range of 120-180.  
   
   
       13 . The method of  claim 3  further comprising the copolymers and/or ionomers are added as solid particles of different sizes.  
   
   
       14 . The method of  claim 13  wherein the copolymers and/or ionomers are selected from the group consisting of pellets, prills, beads, granules, or powders.  
   
   
       15 . The method of  claim 3  further comprising the copolymers and/or ionomers are utilized in the treatment as a dispersion.  
   
   
       16 . The method of  claim 15  wherein the size of the particles in the dispersion are in the range of 0.3 microns to 0.03 microns.  
   
   
       17 . The method of  claim 13  further comprising a mix of different sizes of solid particles of copolymer is employed that further aids bridging of a leak path.  
   
   
       18 . The method of  claim 17  further comprising the particles are sized such that large particles take up the most volume possible and the remaining volume is filled in with smaller solids.  
   
   
       19 . The method of  claim 18  wherein large particles are sized to occupy the most volume possible and filled in with smaller solids up to 80-90% of the volume, leaving enough volume for only 10-20% liquid by volume.  
   
   
       20 . The method of  claim 19  further comprising the particles are sized such that when the mixture enters a lost circulation zone, some fluid is lost, causing the remaining volume of large and smaller particles to lose flow properties and lock in place.  
   
   
       21 . The method of  claim 1  further comprising optionally adding at least one divalent or multivalent ion selected from the group consisting of alkaline earth metal ions and transition metal ions, or combinations thereof  
   
   
       22 . The method of  claim 21  wherein the divalent or multivalent ions selected from the group consisting of alkaline earth metal ions and transition metal ions, or combinations thereof, are chosen for specific formation temperatures, conditions, and composition in order to control the ionomer(s) formed in place.  
   
   
       23 . The method of  claim 21  wherein the divalent or multivalent ion is selected from the group consisting of ZnO, MgO, CaCO 3 , Zn(OH) 2 , Zn(CO 3 ) 2  and lime, and combinations thereof.  
   
   
       24 . The method of  claim 21  further comprising divalent or multivalent ion(s) can be utilized as part of the treating fluid or added as smaller particles or powders.  
   
   
       25 . The method of  claim 1  further comprising the treating fluid contains other solid agents selected from bridgers, fillers, surface plugging and interstitial agents, or a combination thereof.  
   
   
       26 . The method of  claim 1  further comprising the copolymer(s) and/or ionomer(s) are premixed and added to a drilling fluid.  
   
   
       27 . The method of  claim 1  further comprising the copolymer(s) and/or ionomer(s) are added to remedial fluid.  
   
   
       28 . The method of  claim 1  further comprising the copolymer and/or ionomer is added to wellbore treating fluid in an amount in the range of about 5 to 100 lbs/barrel.  
   
   
       29 . The method of  claim 28  wherein the copolymer and/or ionomer is added in an amount in the range of about 10 to 50 lbs/barrel of fluid.  
   
   
       30 . The method of  claim 1  further comprising the drilling fluid is selected from water-based and non-aqueous based.  
   
   
       31 . A wellbore treatment composition comprising one or more copolymer(s) of ethylene acrylic acid and ethylene methacrylic acid, or the single valence ionomer(s) thereof, added to drilling fluid in an amount in the range of about 5 to 100 lbs/barrel.  
   
   
       32 . The treatment composition of  claim 31  wherein the single valence ionomers are single valence metal salt ionomers.  
   
   
       33 . The treatment composition of  claim 32  wherein the single valence metal salt ionomers are selected from single valence ionomers formed by reaction of the acidic groups on the copolymer(s) with alkaline salts of sodium, potassium, and lithium, or ammonia/ammonium (NH 3 /NH 4   + ).  
   
   
       34 . The treatment composition of  claim 31  further comprising the copolymer(s) and/or single valence ionomers thereof have acid numbers in the range of about 20 to 180.  
   
   
       35 . The treatment composition of  claim 31  further comprising the copolymer(s), or partially neutralize ionomer(s), are added as solid particles of different sizes.  
   
   
       36 . The treatment composition of  claim 35  wherein the particles are selected from the group consisting of pellets, prills, beads, granules, or powders.  
   
   
       37 . The treatment composition of  claim 31  further comprising the copolymers and/or ionomers are utilized as dispersions.  
   
   
       38 . The treatment composition of  claim 31  further comprising optionally adding at least one divalent or multivalent ion selected from the group consisting of alkaline earth metal ions and transition metal ions.  
   
   
       39 . The treatment composition of  claim 38  wherein the divalent or multivalent ion is selected from the group consisting of ZnO, MgO, CaCO 3 , Zn(OH) 2  , Zn(CO 3 ) 2  and lime, and combinations thereof.  
   
   
       40 . The treatment composition of  claim 31  in combination with any other solid bridging agents or fillers or additives known in the art utilized for lost circulation.