Below fracture pressure pulsed gel injection method

Abstract

A method for the injection of a pre-determined volume of gel below a fracture pressure limit is described. The fracture pressure limit for an unfractured formation is the fracture initiation pressure. The pressure limit for a previously fractured formation is the fracture extension pressure. Initially, a desired gel is injected into a thief zone at a constant rate while maintaining the injection pressure below the limiting fracture pressure. When the injection pressure reaches the formation fracture pressure limit, gel injection is halted for a period of about 3 hours. Afterwards, the bottom hole pressure is allowed to decline and stabilize. Next, gel injection is resumed at the same rate and pressure used prior to halting the injection. If necessary gel injection can be halted when the formation's pressure limit is again reached. After a period of about 3 hours, injection of gel can be again commenced. These steps can be repeated until a pre-determined volume of gel has been placed into the thief zone.

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