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Study on the Influence of Tripping Operation on Annular Transient Surge-swab Pressure of Herschel-Bulkley Fluid


 The accurate prediction of transient surge-swab pressure, during the tripping operation under a narrow annular clearance-narrow pressure window, is an important premise to ensure the safety of tripping operation and drilling. The influence of drilling fluid flow friction under different rheological modes was mainly considered according to the transient flow model. Meanwhile, the influence of pumpage on transient surge-swab pressure during tripping operation was also considered with Herschel-Bulkley Fluid based tripping operation bottomhole transient surge-swab pressure calculation model established. Compared with the Herschel-Bulkley mode, the Power-law mode and Bingham mode will overestimate the flow friction of drilling fluid. The surge-swab pressure peak values of different rheological modes are Bingham mode > Power-law mode > Herschel-Bulkley mode. The surge-swab pressure peak values of different mud systems are water-based mud > polymer mud > oil-based mud, and selecting the oil-based and polymer mud that can effectively reduce the transient fluctuation pressure during tripping operations. During tripping out operation, the pump shall be turned on to the critical displacement to offset the decrease of bottomhole surge-swab pressure. During tripping in operation, the pump shall be turned off and the tripping velocity shall be strictly controlled to avoid excessive high bottomhole surge-swab pressure. Conclusions: Herschel-Bulkley Fluid based tripping operation bottomhole transient surge-swab pressure study helps control the surge-swab pressure during tripping operations and it is of great significance for lean, safe and efficient drilling in narrow pressure window formations.