Technical Paper: Degradable Alternative to Risky Millout Operations in Plug and Perf

Society: SPE
Paper Number: 173695
Presentation Date: 2015
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With hundreds of thousands of well stages completed in 2014, the “plug-and-perf” technique is the number one stimulation method used in unconventional reservoirs. This technique relies on the use of metal or composite plugs to isolate sections of the reservoir to be hydraulically fractured. After all the stimulation operations are complete, plug removal is required to enable production to begin. A motor and a mill assembly must be conveyed into the well, usually by coiled tubing, to eliminate the plugs used during the stimulation.

In wells with low reservoir pressure or long horizontal sections, plug millout can prove very challenging. Returns do not easily reach the surface, and fluid is often lost into the recently created fractures. Even with the use of nitrogen to assist with cleaning operations, debris from the plugs removed can accumulate in the horizontal section, posing a risk of getting the coiled tubing stuck during the operation. In addition to this significant risk, the economic impact of such operations increases under these conditions because operations tend to be lengthier and more complex than traditional plug millouts. 

A new plug-and-perf technology has been developed to address the problems mentioned above. This method relies on degradable technology to eliminate the need to remove plugs. During fracturing, this new technology follows the same process as traditional plug and perf, but no plug removal is required after stimulation. Seat assemblies serve the function of plugs, and after all stages are completed, these seats remove themselves by simple contact with flowback water. Immediate production is possible and the well is left with a fullbore ID. No restrictions are left in the well that would prove problematic during any future workover intervention. This restriction-free environment also allows for the full production potential of the well to be achieved, as no chokes to production are left in the well. 

The operational sequence of the new, fully degradable isolation assembly for plug-and-perforate technique has shown a seamless integration into current best practices for operators in the Eagle Ford, where the technology has been applied.

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