Identification and Response Suggestions for Common Drilling Conditions

Identification and Response Suggestions for Common Drilling Conditions

In well drilling operations, timely identification of different working conditions and taking corrective measures are crucial to ensuring construction safety, efficiency, and well completion quality. The following outlines several common working conditions and basic response strategies.

I. Normal Drilling

Identification: The drill bit rotates smoothly or impacts, the drilling speed matches the current formation hardness, the circulating fluid (mud or water) returns normally, and it carries drill cuttings smoothly.

Response Suggestions: Maintain stable drilling parameters and carefully observe changes in the returned material (rock cuttings) to prepare for determining if a new formation has been entered. This is the ideal state and should be maintained.

II. Slow or No Drilling Progress

Identification: The drill bit rotates continuously but the drilling progress is extremely slow or completely stops, the mechanical load increases, and abnormal noises may be present.

Main Causes and Responses:

Drill bit wear: The amount of cuttings produced is significantly reduced. The drill should be pulled up for inspection, and the drill bit replaced.

Encountering hard rock or gravel layers: Ordinary drill bits cannot effectively break these layers. The drill bit should be replaced with a suitable hard rock drill bit (such as an alloy drill bit or a roller cone drill bit) or the drilling mode should be switched to percussion drilling.

Poor mud performance: In soft formations, excessively thin mud cannot effectively protect the borehole wall and carry drill cuttings, leading to drill bit clogging. The mud concentration and viscosity should be adjusted.

III. Well Circulation Fluid Loss

Identification: Mud or water pumped into the borehole enters but does not exit, or the outflow is much less than the inflow, and the fluid level at the wellhead drops.

Main causes and solutions:

Encountering fractures or permeable layers: Clay balls, sawdust, or a special plugging agent should be immediately added to the borehole, and the mud viscosity should be increased to seal the fractures. Observe while plugging; if ineffective, casing isolation should be considered.

Severe wellbore collapse: Large blocks of formation collapse block the circulation channels. After hoisting the drill, a special tool (such as a grab bucket) should be lowered to clean the borehole, while simultaneously optimizing mud performance to stabilize the wellbore.

IV. Stuck Drill Bit

Identification: The drill string is stuck in the hole, unable to rotate or be lifted, a relatively dangerous situation.

Main Causes and Solutions:

Stuck Drill Bit Due to Wellbore Instability and Collapse: Occurs in loose formations. Avoid forced rotation or lifting. Try starting the pump to establish circulation, using circulating fluid to flush, lubricate, and stabilize the wellbore, combined with gentle movements using equipment (such as jacks).

Stuck Drill Bit Due to Cuttings Settlement or Keyway: Caused by prolonged pump downtime or irregular wellbore. Try alternating pump operation, slow rotation, and lifting. Prevention is key; maintain good circulation and wellbore quality.

V. Well Deviation (Non-Straight Hole)

Identification: Drilling feels unstable, drill string friction is high; inclination meter data shows an angle exceeding the standard.

Main Causes and Solutions:

Uneven Formation Hardness or Encountering Inclined Rock Formations: Reduce drilling pressure and rotation speed, use a stabilizer or a more rigid drill string assembly to correct deviation. In severe cases, backfilling and correction are necessary before re-drilling. Uneven equipment installation or improper parameters: Strictly level the drilling rig before drilling begins, initially using light pressure to ensure a vertical entry point.

VI. Signs of Water Production and Aquifer Identification

Identification: The circulating fluid returning during drilling suddenly becomes clearer and increases in volume; or the fluid level at the wellhead rises rapidly after pump shutdown.

Responsibilities: Record the current depth, reduce drilling speed, and observe carefully. This layer may be the target aquifer. A simple pumping test can be conducted to preliminarily determine the water volume. If the water quality is clear and the volume is satisfactory, well completion near this depth can be considered.

Summary: Prevention is key, operate smoothly. Most complex operating conditions stem from inaccurate formation assessment, improper operation, or inadequate mud maintenance. The core is: frequently observe the returned material and instrument data, and adjust the drill bit, drilling pressure, rotation speed, and mud properties promptly according to formation changes. In case of danger, remain calm and prioritize gentle solutions such as circulation and movement to resolve the situation, avoiding direct confrontation that could escalate the accident. When the situation exceeds your own handling capabilities, seek professional support promptly.