US2011220349A1PendingUtilityA1

Methods for minimizing fluid loss to and determining the locations of lost circulation zones

38
Assignee: MI LLCPriority: Nov 19, 2008Filed: Nov 13, 2009Published: Sep 15, 2011
Est. expiryNov 19, 2028(~2.3 yrs left)· nominal 20-yr term from priority
Inventors:Eugene Dakin
E21B 21/003
38
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Claims

Abstract

A method for determining a location of a lost circulation zone in a wellbore having a first wellbore fluid therein that includes allowing loss of the first wellbore fluid to the lost circulation zone to stabilize; adding a volume of a second wellbore fluid having a density less than the first wellbore fluid to the wellbore on top of the first wellbore fluid to a predetermined wellbore depth; determining an average density of the combined first wellbore fluid and second wellbore fluid; mixing the first wellbore fluid and the second wellbore fluid together; pumping a volume of a third wellbore fluid having a density greater the average density of the combined first and second wellbore fluid into the wellbore bottom until fluid loss occurs; and determining the location of the lost circulation zone is disclosed.

Claims

exact text as granted — not AI-modified
1 . A method for determining a location of a lost circulation zone in a wellbore having a first wellbore fluid therein, comprising:
 allowing loss of the first wellbore fluid to the lost circulation zone to stabilize;   adding a volume of a second wellbore fluid having a density less than the first wellbore fluid to the wellbore on top of the first wellbore fluid to a predetermined wellbore depth;   determining an average density of the combined first wellbore fluid and second wellbore fluid;   mixing the first wellbore fluid and the second wellbore fluid together;   pumping a volume of a third wellbore fluid having a density greater the average density of the combined first and second wellbore fluid into the wellbore bottom until fluid loss occurs; and   determining the location of the lost circulation zone.   
     
     
         2 . The method of  claim 1 , further comprising:
 pumping a lost circulation treatment into the determined location of the lost circulation zone.   
     
     
         3 . The method of  claim 1 , wherein the third wellbore fluid has a density of at least 0.5 ppg more than the average density of the combined first and second wellbore fluid. 
     
     
         4 . The method of  claim 1 , wherein the pumping the volume of third wellbore comprises:
 pumping the third wellbore fluid to a bottom of a drilling assembly; and   pumping and measuring pump strokes as the third wellbore fluid exits the bottom of the drilling assembly until fluid loss is detected and pumping is halted.   
     
     
         5 . The method of  claim 1 , further comprising:
 identifying loss of the first wellbore fluid to the loss circulation zone.   
     
     
         6 . The method of  claim 5 , further comprising:
 stopping pumping of the first wellbore fluid into the wellbore.   
     
     
         7 . The method of  claim 1 , further comprising:
 determining a location of a second loss circulation zone in the wellbore.   
     
     
         8 . The method of  claim 1 , wherein the mixing comprises forming a homogenous blend of the first and second wellbore fluids. 
     
     
         9 . A method for minimizing fluid loss to a lost circulation zone in a wellbore having a first wellbore fluid therein, comprising:
 allowing loss of the first wellbore fluid to the lost circulation zone to stabilize;   adding a volume of a second wellbore fluid having a density less than the first wellbore fluid to the wellbore on top of the first wellbore fluid to a predetermined wellbore depth;   determining an average density of the combined first wellbore fluid and second wellbore fluid; and   pumping a third wellbore having the determined average density of the combined first and second wellbore fluids into the wellbore to fill the wellbore.   
     
     
         10 . The method of  claim 9 , further comprising:
 drilling with the third wellbore fluid having the determined average density.   
     
     
         11 . The method of  claim 9 , further comprising:
 pumping a third wellbore having the average density of the combined first and second wellbore fluids into the wellbore to fill the wellbore;   pumping a volume of fourth wellbore fluid having a density greater the average density of the combined first and second wellbore fluid into the wellbore bottom until fluid loss occurs; and   determining the location of the lost circulation zone.   
     
     
         12 . The method of  claim 11 , further comprising:
 pumping a lost circulation treatment into the determined location of the lost circulation zone.   
     
     
         13 . The method of  claim 11 , wherein the fourth wellbore fluid has a density of at least 0.5 ppg more than the average density of the combined first and second wellbore fluid. 
     
     
         14 . The method of  claim 11 , wherein the pumping the volume of fourth wellbore comprises:
 pumping the fourth wellbore fluid to a bottom of a drilling assembly; and   pumping and measuring pump strokes as the fourth wellbore fluid exits the bottom of the drilling assembly until fluid loss is detected and pumping is halted.   
     
     
         15 . The method of  claim 9 , further comprising:
 identifying loss of the first wellbore fluid to the formation.   
     
     
         16 . The method of  claim 9 , further comprising:
 stopping pumping of the first wellbore fluid into the wellbore.   
     
     
         17 . The method of  claim 11 , further comprising:
 determining a location of a second loss circulation zone in the wellbore.   
     
     
         18 . The method of  claim 9 , wherein the pumping the third wellbore fluid comprises displacing the first and second wellbore fluids from the wellbore. 
     
     
         19 . A method for determining a location of a lost circulation zone in a wellbore having a wellbore fluid therein, comprising:
 allowing loss of the wellbore fluid to the lost circulation zone to stabilize;   calculating the pressure gradient of the lost circulation zone;   increasing the weight of the wellbore fluid in the wellbore from a bottom of the wellbore upwards until fluid loss occurs; and   calculating the location of the lost circulation zone.   
     
     
         20 . The method of  claim 17 , further comprising:
 pumping a lost circulation treatment into the determined location of the lost circulation zone.   
     
     
         21 . The method of  claim 17 , wherein calculating the pressure gradient comprises determining a wellbore fluid density that balances or slightly overbalances the pressure gradient. 
     
     
         22 . The method of  claim 17 , wherein the fluid loss stabilizes when the pore pressure and the fluid pressure are substantially the same.

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