Displacement and Pressure Control for Reaming of Blocked Horizontal Shale Gas Wells

Shale gas horizontal wells in the Hongxing Block are challenged by long horizontal sections, narrow annular clearances, well-developed fractures, and the coexistence of lost circulation and wellbore collapse. Complexities such as pipe sticking, pump surging, annular blockage, and cuttings accumulation frequently occur during reaming, severely affecting operational safety and efficiency. To overcome the drawbacks of conventional empirical methods, this paper establishes four quantitative models: displacement-pressure coupling, bottomhole Equivalent Circulating Density (ECD) constraint, critical cuttings transport displacement, and drill string safety loading. An integrated reaming technology involving staged displacement, closed-loop emergency treatment, bi-directional reaming, and segmented circulation is then developed. Field application in Well Hong 3-5HF and multi-well verification demonstrate that the proposed method reduces the reaming complication rate from 15% to below 6.2% and achieves a 100% one-trip success rate in the three application wells tested in this study. This work provides a standardized technical solution for safe and efficient reaming in the Hongxing Block and similar shale gas fields.