Asymmetric Transient Pressure Response and Rebalancing Control During Flow-Path Switching in Ultra-Cold Narrow-Window Drilling: A Field Study Based on an Integrated MPD–CCS

In ultra-cold narrow-window drilling, pipe connection causes flow-path switching as the main circulation is interrupted and bypass circulation is established, breaking the initial relative pressure balance of the whole wellbore and inducing asymmetric transient variations in flow distribution, annular friction, and bottomhole pressure response, thereby increasing the risks of wellbore instability, lost circulation, and kicks. To address the poor pressure-control accuracy, long non-productive time, and inadequate low-temperature adaptability of conventional drilling technologies in the Irkutsk block of Russia, this study developed and field-tested an integrated all-electric managed pressure drilling (MPD) and cold-resistant continuous circulation system (CCS). Existing conventional technologies often suffer from high communication latency and hydraulic freezing in extreme cold environments, leading to uncoordinated pressure compensation. To overcome these limitations, the scientific novelty of this work lies in proposing a transient pressure rebalancing mechanism that effectively suppresses the asymmetric pressure disturbances induced by topological flow path switching. Methodologically, the proposed system was validated through a comprehensive industrial field test. An improved Herschel–Bulkley temperature–pressure coupled model was established to dynamically calculate full wellbore annular pressure loss. Furthermore, a dedicated hardware adapter module utilizing multi-protocol conversion was integrated to achieve a communication delay of less than 8 ms, enabling high frequency coordinated pressure regulation. Field results demonstrate that compared to the delayed responses of conventional systems, the proposed integrated approach successfully maintained a dynamic backpressure tracking error within ±0.069 MPa under extreme conditions of −38 °C and a narrow pressure window of 0.08 g/cm3. The rapid suppression of asymmetric transient responses prevented any lost circulation, kicks, or wellbore collapse. These findings highlight the significant advantages of the integrated system in maintaining pressure field stability, thereby providing a robust and innovative engineering solution for complex well interventions.