Continuous Plug Milling in an Ultra-Dense, Small-Bore Completion
PY9-1HF is a shallow shale-gas appraisal horizontal well. With densely spaced post-fracturing plugs, limited annular clearance, and wellbore losses, the field program coordinated mill selection, circulation timing, and debris management to sustain milling efficiency and cleanout performance.
Engineering Challenge
Following ultra-dense staged fracturing, 88 plugs were closely distributed through the lateral. The 4 in OD casing provided limited annular clearance, while wellbore losses added circulation uncertainty. Debris transport, mill life, circulating pressure, and stable continuous milling were the principal controls.
Tool and Process
A 76 mm bladed mill shoe was selected to balance plug-removal efficiency with useful mill life. The program included a short-trip circulation cycle after every six plugs so that plug debris could be removed before accumulation caused repeated grinding or increased sticking risk.
Field Execution
Execution centered on stable milling parameters and continuous wellbore cleaning. Milling feedback and circulation response were used to control progress, while staged short trips maintained effective returns and supported uninterrupted access to subsequent plugs.
Application Result
All 88 plugs in PY9-1HF were milled within seven days. The result established a new SINOPEC record for the number of plugs removed in a single CT well campaign and demonstrated the effectiveness of coordinated mill selection and circulation cleanout in 4 in OD casing under loss-prone conditions.