Patent ID: 7090036

Claim:
A method for balancing the pressure in a wellbore defined by a first end adjacent the surface and a second end below the surface, said wellbore having a drill string extending from above the wellbore to a location adjacent the second end of said wellbore, said method comprising the steps of: (a) introducing a first fluid having a first density into the drillstring; (b) discharging said first fluid from said drill string adjacent the second end of said wellbore to form a first colunm of fluid within said wellbore; (c) introducing a second fluid having a second density greater than the first density into said wellbore at a location removed from said second end of said wellbore to form a second column of fluid within said wellbore, wherein said second column of fluid is formed between said first colunm and said first end of said wellbore; (d) establishing a gradient between said first and second columns; and (e) adjusting said second column to adjust fluid balancing in the wellbore.