Pumping Fluid To Seal A Subterranean Fracture

Abstract

The disclosure teaches a method of sealing fractures in a wellbore wherein the steps comprise pumping a first sealing fluid into a wellbore under pressure, monitoring the hydraulic pressure of the sealing fluid in the wellbore for an indicator of seal initialization, stopping the pumping of fluid into the wellbore, monitoring the hydraulic pressure of the sealing fluid in the wellbore, and pumping a second sealing fluid into the wellbore. The disclosure also includes the method wherein the concentration of sealing materials in the first fluid is greater than the concentration of sealing materials in the second fluid and the method wherein the first sealing fluid contains a higher concentration of larger diameter sealing materials than the second sealing fluid. The disclosure also includes a method wherein the pumping rate change between the first pumping of sealing fluid and the pumping of the second sealing fluid. The first and second sealing fluids can be the same. The sealing materials of a sealing fluid are selected such that some of the sealing materials are larger than an estimated original fracture size.

What I claim is: 
     
         1 . A method of placing a sealing fluid into a subterranean fracture connecting to a wellbore to seal the fracture proximate to the wellbore comprising the following steps:
 a) pumping a large volume of the sealing fluid into the fracture at a high pump rate;   b) stopping the pumping and waiting for a seal to initialize;   c) resuming pumping a small volume of the sealing fluid into the fracture at a low pump rate; and   d) stopping pumping.   
     
     
         2 . The method of  claim 1  further comprising repeating steps c) and d). 
     
     
         3 . The method of  claim 1  further comprising monitoring wellbore fluid pressure and look for an indicator of seal initialization in step a). 
     
     
         4 . The method of  claim 1  further comprising monitoring wellbore fluid pressure and look for an indicator of seal initialization in step b). 
     
     
         5 . The method of  claim 1  wherein the pumping at the low pump rate maintains an increasing pressure differential across the seal. 
     
     
         6 . The method of  claim 1  further comprising applying a packer or blowout preventer above the fracture in the wellbore. 
     
     
         7 . The method of  claim 1  further comprising pumping sealing fluid of a first concentration followed by stopping of pumping then resuming pumping sealing fluid of a second concentration. 
     
     
         8 . The method of  claim 7  wherein the first concentration is higher than the second concentration. 
     
     
         9 . The method of  claim 7  wherein the first concentration is of larger sized sealing materials and the second concentration is of smaller sized sealing materials. 
     
     
         10 . The method in  claim 1  wherein the procedure further comprises a step, wherein an excess of a seal formed inside the wellbore is removed by the rotation of a drill bit. 
     
     
         11 . The method in  claim 1  wherein the high pump rate is equal to or larger than 2 barrel per minute. 
     
     
         12 . The method in  claim 1  wherein the large volume pumped is at least 5 barrels unless the pump pressure has reached a predefined pressure limit. 
     
     
         13 . The method in  claim 1  wherein the sealing fluid contains some of sealing materials selected to have a size larger than an estimated original fracture size. 
     
     
         14 . The method in  claim 1  further comprising estimating an original fracture size. 
     
     
         15 . The method in  claim 1  wherein further comprises repeating steps a) and b) for at least one cycle. 
     
     
         16 . The method in  claim 15  wherein steps a) and b) are repeated, the large volume pumped in each subsequent cycle is smaller than that in its previous cycle. 
     
     
         17 . The method in  claim 1  wherein the low pump rate is smaller than or equal to 1 barrel per minute. 
     
     
         18 . The method in  claim 1  wherein the low pump rate is no greater than 5 barrels per minute. 
     
     
         19 . The method in  claim 1  further comprising repeating steps c) and d) wherein the pumping is stopped for less than 60 minutes. 
     
     
         20 . The method in  claim 1  wherein the small volume is limited by a predefined pressure increment. 
     
     
         21 . The method in  claim 20  wherein the predefined pressure increment is at least 20 psi. 
     
     
         22 . The method in  claim 20  wherein the predefined pressure increment is no more than 500 psi. 
     
     
         23 . The method in  claim 1  wherein the sealing materials consist of one or more of the following materials: diatomaceous earth, calcium carbonate, sand, coke, petroleum coke, graphite, resilient graphitic carbon, synthetic graphite, cedar fiber, nut hulls, corn cobs, asphalt, gilsonite, rubber, drilled cuttings, saw dust, mica, wood chips, engineering plastics, fly ash, cotton seed hulls, walnut hulls, pistachio hulls, almond hulls, peanut hulls, cement, lime, clay, bentonite, modified clay, organoclay, limestone, lime, cement, concrete, dolomite, marble, resin particles, metal particles, ceramic particles, weighting materials such as barite, hematite, iron oxide, ilmenite, nanotechnology particles such as silica nanoparticles, clay nanoparticles, chemically treated particles of these materials such as resin coated, surface sticky, surface hydrophobic and surface hydrophilic particles or combinations thereof. 
     
     
         24 . The method in  claim 23 , wherein the sealing materials further consist of one or more of the following: sponge, open-cell sponge, foam rubber or open-cell foam-rubber. 
     
     
         25 . A method of sealing fractures in a wellbore comprising the steps of:
 a) selecting a size of sealing materials added to a first sealing fluid;   b) pumping the first sealing fluid into a wellbore under a first pressure and rate;   c) monitoring the pressure in the wellbore;   d) stopping the pumping of the first sealing fluid for a first period of time;   e) pumping a second sealing fluid into the wellbore under a second pressure and rate;   f) monitoring the pressure of the second sealing fluid in the wellbore; and   g) stopping the pumping of the second sealing fluid for a second period of time.   
     
     
         26 . The method of  claim 25  further comprising estimating the size of sealing material and mixing the sealing materials into the first sealing fluid. 
     
     
         27 . The method of  claim 25  further comprising looking for indicators of seal initialization in steps b) or d). 
     
     
         28 . The method of  claim 25  wherein the pumping of the first sealing fluid is at a selected first pressure and the pumping of the second sealing fluid at a different selected pressure. 
     
     
         29 . The method of  claim 25  wherein the pumping of the first sealing fluid is at a specified rate and the pumping of the second sealing fluid is at a different specified rate. 
     
     
         30 . The method of  claim 25  wherein the first sealing fluid has a different composition than the second sealing fluid. 
     
     
         31 . The method of  claim 25  wherein the first sealing fluid is the same as the second sealing fluid. 
     
     
         32 . The method of  claim 25  wherein the first sealing fluid has a higher concentration of large size sealing materials than the second sealing fluid. 
     
     
         33 . A method of sealing fractures in a wellbore comprising the steps of:
 a) estimating an original fracture size;   b) selecting a size of sealing materials added to a sealing fluid   c) a first cycle of alternatively pumping the sealing fluid under pressure and a volume rate into a wellbore and stopping the pumping for a first period of time; and   d) a second cycle of alternatively pumping a sealing fluid under pressure and a volume rate into a wellbore and stopping the pumping for a second time; and   e) repeating the pumping and stopping cycle of steps c) or d) a selected number of times until a seal initialization indicator is observed.   
     
     
         34 . The method of  claim 33  further comprising slowly pumping a first sealing fluid into a wellbore before commencing the first cycle. 
     
     
         35 . The method of claim of  33  further comprising monitoring an extension of the drill string or change in the weight on bit. 
     
     
         36 . The method of  claim 33  comprising utilizing comparison of fluid pressure. 
     
     
         37 . The method of  claim 36  further comprising a comparison of fluid pressure during pumping and after pump shut down. 
     
     
         38 . The method of  claim 36  further comprising comparison of fluid pressure during pumping at the same pump rate. 
     
     
         39 . A method of sealing fractures in a wellbore comprising the steps of:
 a) inflating a fracture width with fluid pumped into a wellbore under pressure;   b) pumping a sealing fluid with sealing materials into the fracture; and   c) reducing or stopping the pumping to decrease the fracture width.