1.Settled Cuttings Sticking: High-Risk Static Condition
Critical Negligence: Stopping pumps too early and restarting too late during connections after rapid drilling, leading to prolonged mud static time.
Potential Consequences: Significant cuttings settlement burying bottom hole assembly (BHA), risking expensive equipment loss.
Essential Protocol: Minimize mud static time. Delay pump shutdown and initiate restart promptly to compensate for poor suspension capacity.
2.Internal Drill String Failure: Covert Circulation Loss
Critical Negligence: Ignoring sudden pump pressure drop or abnormal cuttings returns.
Potential Consequences: Washed-out tools, thread disconnection, or string failure; inadequate hole cleaning leading to cuttings accumulation, bit balling, and stuck pipe or wellbore instability.
Essential Protocol: Immediately halt drilling upon pressure drop. First inspect surface equipment; if unresolved, pull out slowly and smoothly. Never back off with rotary table! Rig crew must inspect every joint during tripping.
3.Wellbore Collapse: Geomechanical Instability
Critical Negligence: Inadequate hole fill during tripping out, poor mud properties (high fluid loss, low density), or excessive tripping speed causing surge/swab pressures.
Potential Consequences: Sudden pump pressure increase, severe drag/pull during tripping, or large cavings returns. May escalate to stuck pipe.
Essential Protocol: Maintain continuous hole fill during tripping out. Dedicated personnel must verify fill efficiency (volume in = volume out). Optimize mud properties to control fluid loss and stabilize wellbore. If encountering drag: Return to free depth, circulate at low flow rate, and work pipe to clear debris.
4.Bit Balling: Performance Degradation
Critical Negligence: Insufficient flow rate in soft clay formations, excessively high mud viscosity/gel strength, or drilling without returns.
Potential Consequences: Torque fluctuations, reduced ROP, elevated pump pressure, "piston-effect" during pull-out, high sticking risk.
Essential Protocol: Optimize mud properties for cuttings transport. At first signs of balling: Stop drilling, circulate at high flow rate, and rotate string aggressively. Trip out cautiously: Pull slowly; if resistance occurs, consider circulating via kelly or filling annulus.
5.Single-Elevator Lifting: Critical Handling Error
Critical Negligence: Hoisting drill string with only one elevator engaged due to operational miscommunication.
Potential Consequences: Pipe bending/failure, ejected elevator causing injury, equipment damage.
Emergency Response: Immediately set brakes. Secure slips. Never set elevators on rotary table! Rotate slowly to prevent sticking. Assess damage: Remove affected joint, connect new joint for controlled hoisting, or sever bent section for fishing. Safety first!
6.Early Kick Indicators: Well Control Precursors
Critical Negligence: Failure to recognize unexpected mud flowback/uprising in drill pipe during tripping as kick warning.
Potential Consequences: Missed critical well control window, potentially leading to blowout.
Essential Protocol: Stop tripping immediately. Install kelly, close BOP (if available). Control flowback and fill annulus! Circulate for observation; prepare for well control. If unable to circulate, pull out cautiously while continuously filling.
7.Core Barrel Reaming: Prohibited Operation
Critical Negligence: Attempting to ream obstructions with a core barrel assembly.
Potential Consequences: Core catcher deformation/failure, sidetracking, pump pressure spikes, or barrel breakage.
Essential Protocol: Never ream with core barrels! If encountering obstruction: Retrieve core head and run standard BHA (with taper tap + drill pipe) for reaming.
Safety Principle:
There is no room for compromise in drilling safety—only strict adherence to procedures. Every compliant operation demonstrates respect for life; every risk mitigation action embodies professional responsibility.
