Well re-fracturing method

Abstract

A method of re-treating a well with pre-existing fractures which includes: displacing a tool in a well, leaking off motive fluid to an open fracture zone passed by the tool to diminish the rate of displacement, and locating the open fracture zone above the tool.

What is claimed is: 
     
         1 . A method of re-fracturing a well with pre-existing fractures, comprising:
 deploying into the well a tool connected to surface by a cable;   pumping a motive fluid into the well at a flow rate effective to displace the tool in the well past one or more open fracture zones;   leaking off the motive fluid into the one or more open fracture zones passed by the tool, to diminish a rate of displacement of the tool relative to a rate of the pumping the motive fluid into the well, and locate the one or more open fracture zones above the tool; and   re-fracturing at least one of the one or more open fracture zones located above the tool.   
     
     
         2 . The method of  claim 1 , further comprising tensioning the cable to selectively leak off the motive fluid into the one or more open fractures passed by the tool. 
     
     
         3 . The method of  claim 1 , wherein the cable comprises a distributed measurement cable. 
     
     
         4 . The method of  claim 1 , further comprising conducting a distributed measurement survey along a length of the cable as it is deployed into the well. 
     
     
         5 . The method of  claim 1 , further comprising conducting a distributed measurement survey along a length of the cable in the well, wherein the surveyed measurement is selected from the group consisting of temperature, vibration data, strain data, and combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein the cable comprises a distributed measurement cable, and further comprising obtaining measurements from the cable to determine the location of the one or more open fractures located above the tool. 
     
     
         7 . The method of  claim 1 , wherein the cable comprises a distributed measurement cable, and further comprising obtaining measurements from the cable to monitor execution of the re-fracturing. 
     
     
         8 . The method of  claim 7 , wherein the measurements obtained comprise fluid flow rate versus depth during the re-fracturing to monitor fluid flow into the one or more open fracture zones located above the tool. 
     
     
         9 . The method of  claim 8 , wherein the re-fracturing comprises diverting a re-fracturing treatment fluid by placing a plug in at least one of the one or more open fracture zones located above the tool, and wherein the measurement of the fluid flow rate versus depth indicates the effectiveness of the plug, and further comprising reinforcing the plug if the plug is indicated to be ineffective. 
     
     
         10 . The method of  claim 1 , wherein the tool comprises an isolation device, a perforation tool, or a combination thereof. 
     
     
         11 . The method of  claim 1 , comprising setting the tool at a target depth to isolate the one or more open fracture zones located above the tool for the re-fracturing, from a portion of the well below the tool. 
     
     
         12 . The method of  claim 11 , comprising determining the target depth as a location where a total rate of the motive fluid leak-off into the one or more open fracture zones located above the tool matches the flow rate of the motive fluid pumped into the well, wherein the displacement of the tool is diminished substantially to zero. 
     
     
         13 . The method of  claim 1 , further comprising logging the location of the one or more open fracture zones located above the tool from measurement of the rates of displacement of the tool and pumping the motive fluid into the well. 
     
     
         14 . A method of re-fracturing a well with a series of pre-existing open fracture zones, comprising:
 (a) deploying into the well a first tool connected to surface by a cable;   (b) pumping a motive fluid into the well to displace the first tool at a rate relative to a rate of the pumping of the motive fluid;   (c) displacing the first tool past an open fracture zone to locate the open fracture zone above the first tool;   (d) leaking off the motive fluid into the open fracture zone located above the first tool to diminish a rate of displacement of the tool relative to a rate of the pumping the motive fluid into the well;   (e) plugging one or more of the open fracture zones located above the first tool to at least partially restore the rate of displacement of the first tool relative to the rate of the pumping the motive fluid into the well;   (f) repeating the pumping (b), the displacement (c) and the leaking off (d) until the first tool reaches a first target depth; and   (g) re-fracturing a portion of the well located above the first target depth.   
     
     
         15 . The method of  claim 14 , wherein the cable gathers distributed measurement information to monitor any of (b), (c), (d), (e), (f), (g), or any combination thereof. 
     
     
         16 . The method of  claim 14 , wherein the re-fracturing (g) introduces a fracturing fluid into one or more unplugged open fracture zones. 
     
     
         17 . The method of  claim 14 , wherein the re-fracturing (g) comprises introducing a fracturing fluid and a diverter into the well to distribute the fracturing fluid into one or more of the pre-existing fracture zones, new fracture zones, or a combination thereof. 
     
     
         18 . The method of  claim 17 , wherein the cable gathers distributed measurement information to monitor the distribution of the fracturing fluid. 
     
     
         19 . The method of  claim 14 , further comprising repeating the plugging (e) and (f) a plurality of times until the first tool reaches the first target depth in the well. 
     
     
         20 . The method of  claim 14 , wherein the first target depth is a toe of the well. 
     
     
         21 . The method of  claim 14 , further comprising:
 (h) optionally
 1) repeating the plugging (e) and (f) a plurality of times until the first tool reaches the first target depth in the well, or 
 2) setting the first tool at the first target depth for re-fracturing (g) at least once above the first target depth, or 
 3) a combination thereof; 
   (i) pulling the first tool up the well to a second target depth;   (j) setting the first tool at the second target depth to isolate a portion of the well above the second target depth from a portion of the well below the second target depth; and   (k) re-fracturing in the portion of the well isolated above the second target depth.   
     
     
         22 . The method of  claim 21 , wherein the second target depth is above an open fracture zone located between the first and second target depths. 
     
     
         23 . The method of  claim 21 , further comprising:
 (l) pulling the first tool up the well to a successively higher target depth;   (m) setting the first tool at the successively higher depth to isolate a portion of the well above the successively higher target depth from a portion of the well below the successively higher target depth; and   (n) re-fracturing in the portion of the well isolated above the successively higher target depth.   
     
     
         24 . The method of  claim 23 , further comprising repeating (l), (m), and (n) at least once more. 
     
     
         25 . The method of  claim 14 , further comprising:
 (h) optionally
 a. repeating the plugging (e) and (f) a plurality of times until the first tool reaches the first target depth in the well, or 
 b. setting the first tool at the first target depth for re-fracturing (g) at least once above the first target depth, or 
 c. a combination thereof; 
   (i) optionally disconnecting and retrieving the cable rom the first tool;   (j) deploying a second tool into the well to a second target depth above the first target depth;   (k) setting the second tool at the second target depth to isolate a portion of the well above the second target depth from a portion of the well below the second target depth; and   (l) re-fracturing in the portion of the well isolated above the second target depth.   
     
     
         26 . The method of  claim 25 , further comprising:
 (m) deploying a successive tool into the well to a successively higher target depth;   (n) setting the successive tool at the successively higher depth to isolate a portion of the well above the successively higher target depth from a portion of the well below the successively higher target depth; and   (o) re-fracturing in the portion of the well isolated above the successively higher target depth.   
     
     
         27 . The method of  claim 26 , further comprising repeating (m), (n), and (o) at least once more. 
     
     
         28 . The method of  claim 14 , wherein the plugging (e) comprises placing one or more degradable diverter plugs at one or more of the open fracture zones, respectively, and degrading at least one of the one or more degradable diverter plugs for the re-fracturing (g). 
     
     
         29 . The method of  claim 28 , wherein the cable gathers distributed measurement information to monitor the degradation of the at least one of the one or more degradable diverter plugs, or to monitor the re-fracturing (g), or both. 
     
     
         30 . The method of  claim 28 , wherein the cable gathers distributed measurement information to determine at least one of the one or more degradable diverter plugs has been degraded, and further comprising introducing a fracturing fluid into the at least one or more unplugged open fracture zones wherein the corresponding diverter plug has been determined to have been degraded. 
     
     
         31 . A method of re-fracturing a well with pre-existing fractures, comprising:
 (a) deploying into the well a tool connected to surface by a cable;   (b) pumping a motive fluid into the well at a target flow rate to displace the tool in a bore of the well at a rate of displacement of the tool relative to a rate of increase of a volume of the motive fluid in the well bore;   (c) displacing the tool past a first fracture zone comprising at least one open fracture to leak off the motive fluid into the first fracture zone and diminish the rate of displacement of the tool in response to the leak off;   (d) stopping displacement of the tool at a first target depth below the first fracture zone; and   (e) re-fracturing the first fracture zone located above the first target depth.   
     
     
         32 . The method of  claim 31 , further comprising setting the tool at the first target depth to isolate the first fracture zone above the first target depth prior to re-fracturing (e). 
     
     
         33 . The method of  claim 31 , wherein the first target depth corresponds to a location of the tool when the leak off of the motive fluid is substantially equal to or greater than the target pumping flow rate. 
     
     
         34 . The method of  claim 31 , further comprising:
 (f) placing diverter in the zone re-fractured in (e) to diminish a rate of the leak off to at least partially restore displacement of the tool in the well bore relative to the target pumping flow rate;   (g) displacing the tool past a successive fracture zone comprising at least one open fracture to leak off the motive fluid into the successive fracture zone and diminish the rate of displacement of the tool in response to the leak off;   (h) stopping displacement of the tool at a successive target depth below the successive fracture zone; and   (i) re-fracturing the successive fracture zone located above the successive target depth.   
     
     
         35 . The method of  claim 34 , further comprising:
 (j) placing diverter in the zone re-fractured in (i) to diminish a rate of the leak off to at least partially restore displacement of the tool in the well bore relative to the target pumping flow rate; and   (k) repeating the displacement in (g), the stopping in (h), and the re-fracturing in (i).   
     
     
         36 . The method of  claim 35 , further comprising repeating (j) and (k) one or a plurality of additional times. 
     
     
         37 . The method of  claim 1 , further comprising sealing at least one open fracture zone of the well with at least one removable sealing agent, selectively removing the removable sealing agent from at least one target zone, and re-fracturing the at least one target zone. 
     
     
         38 . The method of  claim 37 , wherein the re-fracturing occurs while at least one open fracture zone of the well is sealed with at least one removable sealing agent. 
     
     
         39 . The method of  claim 37 , wherein at least one of: sealing at least one open fracture zone of the well with at least one removable sealing agent, selectively removing the removable sealing agent from the at least one target zone, or the re-fracturing of the at least one target zone, is repeated at least one time. 
     
     
         40 . The method of  claim 37 , further comprising isolating at least one section of the well. 
     
     
         41 . The method of  claim 38 , further comprising unisolating the isolated section of the well. 
     
     
         42 . The method of  claim 39 , wherein during the repeating, multiple zones are re-fractured and form a first interval of the well, which upon completion of their re-fracturing the first interval is isolated and at least one more interval comprising a plurality of well zones is re-fractured in a substantially similar manner. 
     
     
         43 . The method of  claim 37 , further comprising sealing the re-fractured target zone with at least one removable sealing agent. 
     
     
         44 . The method of  claim 37 , wherein the selective removing comprises at least one of perforating, abrading, dissolving, hydrolyzing, oxidizing, degrading, or melting the removable sealing agent from at least one sealed target zone. 
     
     
         45 . The method of  claim 37 , wherein the selective removal of the removable sealing agent comprises contacting the at least one target zone with a removal agent by bullheading the removal agent downhole, spotting the removal agent downhole, the use of downhole containers to deliver the removal agent, or a combination thereof. 
     
     
         46 . The method of  claim 45 , wherein the removal agent dissolves the removable sealing agent; and wherein the removal agent is at least one of hydrochloric acid, formic acid, acetic acid, hydroxides, ammonia, organic solvents, diesel, oil, water, brines, solutions of organic or non-organic salts, and mixtures thereof. 
     
     
         47 . The method of  claim 37 , wherein the re-fracturing comprises at least one of a propped fracturing, a non-propped fracturing, a slick-water, acidizing, acid fracturing, injection of chelating agents, stimulating, or squeezing a chemical. 
     
     
         48 . The method of  claim 37 , wherein the removable sealing agent comprises a viscous fluid from at least one of gelled water, viscoelastic surfactant fluids, crosslinked polymer solutions, slick-water, foams, emulsions, dispersions of acid soluble solid particulates, dispersions of oil-soluble resins, and mixtures thereof. 
     
     
         49 . The method of  claim 37 , wherein the removable sealing agent comprises a solid material comprising at least one of acid soluble cement, calcium carbonate, magnesium carbonate, polyesters, magnesium, aluminum, zinc, and their alloys, hydrocarbons with greater than 30 carbon atoms, and carboxylic acids and derivatives thereof. 
     
     
         50 . The method of  claim 37 , wherein the removable sealing agent comprises manufactured shapes selected from at least one of particulates, sized particulates, fibers, flakes, rods, pellets and combinations thereof. 
     
     
         51 . The method of  claim 37 , wherein the removable sealing agent comprises a degradable composite material comprising a degradable polymer mixed with particles of a filler material. 
     
     
         52 . The method of  claim 37 , wherein the sealing comprises placing the removable sealing agent in a desired zone in the wellbore by at least one of bullheading the removable sealing agent downhole, spotting the removable sealing agent downhole, or using downhole containers to deliver the removable sealing agent. 
     
     
         53 . The method of  claim 52 , wherein the sealing further comprises:
 injecting the sealing material into the selected zone by increasing pressure in the well.   
     
     
         54 . The method of  claim 37  wherein at least one seal of the sealed zones is mechanically strengthened by compacting the seal with an epoxy resin gluing system or an emulsion comprising wax or paraffin. 
     
     
         55 . The method of  claim 37 , wherein at least two zones are sealed with two distinct removable sealing agents which possess the capability of being removed by dissimilar removal processes. 
     
     
         56 . The method of  claim 37 , further comprising sealing the re-fractured zone(s) by at least one of plugging of perforations and/or well or annulus space between a casing and a borehole, reducing permeability of formation rock, modifying the stress field, or changing formation fluid pressure. 
     
     
         57 . The method of  claim 1 , further comprising:
 isolating, or sealing with a removable sealing agent, or a combination thereof, all but one of a plurality of the open fracture zones;   re-fracturing the open fracture zone while the other zones are isolated or sealed or a combination thereof;   sealing the re-fractured zone or isolating the section of the wellbore comprising the re-fractured zone;   selectively removing the removable sealing agent from an untreated sealed zone; and   repeating the sequence of re-fracturing the open fracture zone while the other zones are isolated or sealed, isolating or sealing the re-fractured zone, and selectively removing the removable sealing agent from a sealed un-re-fractured zone until the desired number of zones are re-fractured.