Unconventional deep gas completions are subject to extreme hydraulic fracturing stimulation and production loads. These loads impose tough requirements on completion design. These completions must be capable of withstanding high compression, collapse, burst and tension loads.

Tube move calculation is a key part of Polished Bore Receptacle (PBR) completion design. Software simulation estimates compressional tube move due to the ballooning effect during frac operations, and the elongating tube move due to temperature expansion during production operations. With tube move estimated for all possible loads imposed on completion, selecting the right PBR length becomes possible. Current design practice is not accounting for Friction Factor (FF) in tube move calculations. This practice is acceptable for conventional gas wells completions with less tube movement where 20 ft. long PBR is adequate. When dealing with unconventional deep gas frac stimulated completions, this design approach leads to tube move requiring 30 ft. PBR or possibly longer. While the solution seems to be a simple replacement of the equipment, the impact can be huge including such issues as logistics, use of heavier completion fluid, higher slack off weight for landing upper completion and other possible, unforeseen complications.

Discussion with engineering software provider and scouting industry publications did not reveal the answer to why the use of FF is not a standard practice in software simulation of tube move. We had to find the answer ourselves, allocating drilling rig time and conducting a number of tube move measurements in actual unconventional completions. Using digital slick-line with gamma-ray (GR) and casing collar locator (CCL) logging tool the actual tube move caused by high-pressure ballooning effect was measured and the applicable friction factor was deduced. Applying friction component drastically reduces software simulated tube move and requirements in length of PBR, weight of completion fluid and slack-off weight for landing upper completion, thus simplifying the completion and reducing risks and cost.

The following paper discusses the measurement of tube move under actual well conditions and the resulting deductions on the effect of friction. Identified FF is recommended for use in optimized unconventional completion design.

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