Completing the Bakken shale in North Dakota presents options that are varied and complex. To achieve optimum recovery, the Bakken formation needs to be drilled horizontally and hydraulically fracture-stimulated. If the wellbore is drilled in the orientation to achieve a longitudinal fracture treatment, only one fracture treatment is needed and the issue of frac-stage isolation is not an issue. If the stress orientation is unknown, or the wellbore is drilled in the orientation for transverse oriented hydraulic fracture direction, then frac-stage isolation is an important decision. In the past few years, numerous methods have been tried to achieve good frac-stage isolation in the Bakken. A brief review of completion success in the Bakken identifies one method that has the highest degree of success when completing transverse-oriented hydraulic fractures. The best wells have an uncemented liner and a compartmental completion technique. These compartments can be tailored to cover specific areas of the borehole so the treatment is placed near the best shows. The frac compartments are created with the use of swellable external casing packers and ball-actuated stimulation sleeves. In one pumping event, multiple frac-stages are pumped, separated by opening individual stimulation sleeves selectively from the toe to the heel. The completion of two wells are discussed that show positive proof of this concept from a completion and production perspective.

Horizontal shale completions require multi-stage high-pressure hydraulic fracturing stimulation treatments in order to deliver commercially viable production in low permeability reservoirs. Unconventional shale plays, such as the Eagle Ford and Haynesville Shale, often can require stimulation treatments that must be implemented in high pressure and high temperature (HPHT) conditions. Typically, these wells are completed with long casing strings, and it is critical that these monobore casing strings withstand high injection pressures as well as maintain mechanical integrity during thermal contraction/expansion. So what happens when the pre-frac casing pressure integrity pressure test fails? What is the "fix" that will allow treatments to be pumped at high pressure and rate? How will frac stages be isolated during the completion? Typically, remediation techniques have included everything from casing patches and expandable casing to coiled tubing completions. Unfortunately, these solutions can have pressure limitations, and in addition, can be cost prohibitive. The authors of this paper will discuss how design of a 4-in. tie-back string with flush joint connections equal to the properties of the casing was capable of repairing a 5-1/2-in. monobore production casing that experienced extensive casing failure. The extremely small annular tolerance did not allow a conventional packer assembly or cementing for pressure isolation; thus, swellable packer technology was used to anchor the casing in place. A special flow-thru frac plug was designed so that it could be pumped through the 4-in. tie-back casing and set in the 4-1/2-in. lateral, allowing a plug-and-perf fracture completion to be performed. The stimulation treatments were pumped to completion and demonstrated 1), that the pressure isolation integrity of the casing system was satisfactory; and 2), that the flow-thru frac plugs could maintain isolation between stimulation treatments. This wellbore was in the Eagle Ford Shale. True vertical depth (TVD) was ~ 13,000 ft, bottomhole temperature (BHT) was ~325°F with a 0.95 psi/ft frac gradient, and surface pressures exceeded 10,000 psi during the stimulation treatments.

Horizontal shale completions require multistage high-pressure hydraulic-fracturing stimulation treatments to deliver commercially viable production in low-permeability reservoirs. Unconventional shale plays, such as the Eagle Ford shale and Haynesville shale, often can require stimulation treatments that must be implemented in high-pressure, high-temperature (HP/HT) conditions. Typically, these wells are completed with long casing strings, and it is critical that these monobore casing strings withstand high injection pressures as well as maintain mechanical integrity during thermal contraction/expansion. So, what happens when the prefracturing casing-pressure-integrity pressure test fails? What is the "fix" that will allow treatments to be pumped at high pressure and rate? How will fracturing stages be isolated during the completion? Typically, remediation techniques have included everything from casing patches and expandable casing to coiled-tubing completions. Unfortunately, these solutions can have pressure limitations and can also be expensive.The authors of this paper will discuss how design of a 4-in. tieback string with flush joint connections equal to the properties of the casing was capable of repairing a 5 1 =2-in. monobore production casing that experienced extensive casing failure. The extremely small annular tolerance did not allow a conventional packer assembly or cementing for pressure isolation; thus, swellable-packer technology was used to anchor the casing in place. A special flow-through fracturing plug was designed so that it could be pumped through the 4-in. tieback casing and set in the 4 1 =2-in. lateral, allowing a plug-and-perforate fracture completion to be performed. The stimulation treatments were pumped to completion and demonstrated that the pressure isolation integrity of the casing system was satisfactory and that the flow-through fracturing plugs could maintain isolation between stimulation treatments. This wellbore was in the Eagle Ford shale. True vertical depth was approximately 13,000 ft, bottomhole temperature was approximately 325 F with a 0.95-psi/ft fracture gradient, and surface pressures exceeded 10,000 psi during the stimulation treatments.