Unique Solution to Repair Casing Failure in a HP/HT Wellbore Allows for Successful Multistage Stimulation Treatment in an Unconventional Reservoir

Wellhoefer, Benjamin (Halliburton) | Stegent, Neil (Halliburton) | Tunstall, K. Michael (Halliburton) | Veillette, Christian (Enduring Resources) | Frazier, Garrett (Magnum Oil Tools)



Horizontal shale completions require multistage high-pressurehydraulic-fracturing stimulation treatments to deliver commercially viableproduction in low-permeability reservoirs. Unconventional shale plays, such asthe Eagle Ford shale and Haynesville shale, often can require stimulationtreatments that must be implemented in high-pressure, high-temperature (HP/HT)conditions. Typically, these wells are completed with long casing strings, andit is critical that these monobore casing strings withstand high injectionpressures as well as maintain mechanical integrity during thermalcontraction/expansion. So, what happens when the prefracturingcasing-pressure-integrity pressure test fails? What is the "fix" that willallow treatments to be pumped at high pressure and rate? How will fracturingstages be isolated during the completion? Typically, remediation techniqueshave included everything from casing patches and expandable casing tocoiled-tubing completions. Unfortunately, these solutions can have pressurelimitations and can also be expensive. The authors of this paper will discusshow design of a 4-in. tieback string with flush joint connections equal to theproperties of the casing was capable of repairing a 5 1/2-in. monoboreproduction casing that experienced extensive casing failure. The extremelysmall annular tolerance did not allow a conventional packer assembly orcementing for pressure isolation; thus, swellable- packer technology was usedto anchor the casing in place. A special flow-through fracturing plug wasdesigned so that it could be pumped through the 4-in. tieback casing and set inthe 4 1/2-in. lateral, allowing a plug-and-perforate fracture completion to beperformed. The stimulation treatments were pumped to completion anddemonstrated that the pressure isolation integrity of the casing system wassatisfactory and that the flow-through fracturing plugs could maintainisolation between stimulation treatments. This wellbore was in the Eagle Fordshale. True vertical depth was approximately 13,000 ft, bottomhole temperaturewas approximately 325°F with a 0.95-psi/ft fracture gradient, and surfacepressures exceeded 10,000 psi during the stimulation treatments.