Frac Plug Drill Out Benefits from Hybrid Roller Cone Bit Design
Improving frac plug drill out in multi-zone completions is an important step in enhancing the development of unconventional assets. The key challenges are efficiency and durability in drilling the diverse materials that make up the 15 to 40 plugs in a typical completion, and addressing the resulting pressure spikes and exposure to high-hydrocarbon fluids that can reduce bit life.
Field observations identified trends in the frac plug bit dull modes, which resulted in a study of operating practices and analysis of what was being drilled. It was found that standard frac plugs have an outer component made of hardened steel, ceramic or other metal, and an inner component of softer composites and rubber. The outer sleeve can damage the bit, while the softer inner component result in large cuttings that are difficult to circulate out of the hole. The process also identified pressure spikes and high hydrocarbon exposure that raised bearing reliability issues.
Reviews with rig personnel, completions engineers, and plug manufacturers were conducted. A series of various bit designs were then run to identify how to best match the cutting structure of the bit with the plug to be drilled.
This review and design process resulted in a patent-pending hybrid roller cone bit with an outer cutting structure of tungsten carbide inserts from a 517 IADC bit, and an inner cutting structure from a 236 IADC steel tooth bit. The tungsten carbide inserts provide a much tougher cutting structure while the steel tooth cutting structure reduces the composite and rubber components to a smaller, more easily circulated cutting size.
This paper examines the review and design process, and presents field results that include the first presentation of a 57-well study conducted in the Eagle Ford shale play in south Texas, where the hybrid bit drilled frac plugs 13.6% faster than standard tooth bits and averaged 3.3 more plugs per use. The authors examine materials and manufacturing contributions, and the role of design software and simulations in optimizing durability and penetration rates. The paper includes operator perspectives on the technology’s development and application.
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