Patent ID: 8899332

Claim:
A method for building a plug in a horizontal wellbore, the method comprising: (a) pumping a fracturing fluid into the horizontal wellbore; (b) pumping into the wellbore a fluid pill having a well treatment agent suspended therein, the well treatment agent comprising an ultra lightweight (ULW) deformable core and a viscosifying polymer and crosslinking agent coated onto the core, wherein the ULW deformable core has an apparent specific gravity less than 2.45; (c) pumping a displacement fluid down the wellbore and displacing the fluid pill further into the wellbore in proximity to a perforation tunnel in a desired location; (d) varying the pumping rate of the displacement fluid for a time sufficient for at least one fracture within the horizontal wellbore to at least partially close, the well treatment agent remaining suspended within the fluid pill; (e) pumping the displacement fluid down the horizontal wellbore to slowly displace the fluid pill; (f) increasing the viscosity of the fluid pill to form a gelled fluid by the in-situ reaction of: (i) the crosslinking agent as it is disassociated from the ULW deformable core; and (ii) viscosifying polymer disassociated from the ULW deformable core wherein the ULW deformable core is suspended within the gelled fluid; and (g) at least partially preventing the gelled fluid containing the suspended ULW deformable core from entering the at least one fracture in the zone, wherein the gelled fluid forms a fluid-impermeable plug within the wellbore.