Managed Surface Temperature/Pressure in Real-Time Drilling for Gas Migration and Wellbore Stability Detection in Subsurface

Wellbore stability and gas migration detection from a gas-saturated formation are important for engineer during production and drilling. Erroneous onset of gas migration and wellbore collapse may be predicted if no accurate bottom hole pressure (BHP) is obtained in real time, despite a reliable geomechanics and gas migration models are utilized. Pressure along a tubing-annulus system must be calculated from the surface to the bottom hole, where thermal-hydraulic-mechanical (THM) may be coupled through wellbore wall to those inside the porous formations. A wellbore-reservoir model including tubing-annulus-reservoir system is established so that a pressure profile coupled to the inflow/outflow of the gas-saturated porous formations may be achievable. Coupled to each other inside the tubing-annulus system, thermal-hydraulic (TH) is managed and coupled to those THM in the formation so that wellbore stability and gas influx from the formation and migration along the annulus are forecasted. Along managed pressure drilling (MPD), managed temperature (MT) is also critically important both for BHP calculation so that the wellbore stability and blowout are accurately predicted. Temperature changes in the circulated fluid may affect the BHP calculation and stress concentration at wellbore wall. In an environment of narrow drilling mud window, MT may enlarge the window and reduce the active stress concentration at wellbore wall at the same time. Along a comprehensive reservoir-wellbore model, an engineering procedure with integrated logging-geomechanics model for inputs is proposed. In this procedure, WITSMAL data reading, MEM model buildup, and wellbore collapsing/blowout detection is incorporated. Real-time WITSMAL data is processed and transferred into MEM model so that real-time critical pressure may be predicted in formation ahead of the drilling bit. Both the MEM model and wellbore stability in the drilled section are examined and corrected if erroneous results are detected. A prediction ahead of the drilling bit is forecast and safe mud weight is recommended or adjusted if pre-design mud is not adequate. A novel logging-drilling procedure focusing on geomechanics is proposed. Reading real-time WITSMAL data and modifying MEM model, on which a real-time critical wellbore pressure may be verified, wellbore stability and migrated gas before blowout in drilled section may be identified. All these processes are critically helped by MT and such a real-time modification may allow an accurate forecasting on wellbore instability and blowout risk in the section ahead of drilling bit.