Identification and Response to Common Situations During Well Drilling: Mud Loss, Hole Collapse, and Lack of Water Production

Identification and Response to Common Situations During Well Drilling: Mud Loss, Hole Collapse, and Lack of Water Production

During well drilling, operators closely observe changes in drilling mud, cuttings, and downhole conditions. These are indicators of subsurface conditions and the progress of the drilling operation. Timely identification of common anomalies and correct responses are crucial for ensuring construction safety, well quality, and avoiding significant losses. The following describes several typical situations and basic response strategies.

Situation 1: Significant mud loss, with a sharp decrease or complete cessation of mud return.

Identification: During normal drilling, the mud pumped into the well should continuously return from the wellhead carrying cuttings. If the amount of returning mud significantly decreases, becomes thinner, or even stops returning, while the pump pressure does not increase abnormally, this indicates "mud loss."

Causes and Response: This indicates encountering formations with well-developed fractures or large pores, such as fractured zones, gravel layers, or karst cavities, where the drilling mud has leaked into these spaces.

Response: Immediately reduce pump pressure and rotation speed to prevent further erosion and enlargement of the leakage channels. Try adding plugging materials (such as sawdust, fibers, or specialized plugging agents) to the mud to seal the fractures. If the leakage is severe and cannot be sealed, it may be necessary to switch to water drilling or adjust the drilling process. In severe cases, it may even be necessary to install casing prematurely to isolate the leaking formation.

Situation 2: Hole collapse, resulting in falling debris and stuck drill string.

Identification: Resistance suddenly increases during drilling or tripping; the drill string becomes stuck; a large amount of fresh debris (irregularly shaped chunks) from a different formation appears in the cuttings returning from the wellhead; abnormal bubbles or a drop in the mud level at the wellhead.

Causes and Response: This usually occurs in loose, poorly cemented sandy soil layers or fractured rock formations due to poor mud wall protection or prolonged drilling downtime.

Response: First, keep the drill string moving to prevent it from becoming completely stuck. Try adjusting the mud properties to increase its viscosity and specific gravity to improve wall protection. Attempt to flush out the collapsed material with a high-volume mud circulation. If the drill string is severely stuck, it may be necessary to use specialized fishing tools or jarring tools to free it. Prevention is better than cure; continuous operation and high-quality drilling mud should be maintained in formations prone to collapse. Situation 3: Drilling reaches the expected depth, but no water or very little water is produced during the pumping test.

Identification: This is a post-completion assessment. When the water pump is running, the water level drops rapidly below the pump inlet, preventing the formation of a stable water flow; or only a very small amount of water is produced, which is quickly pumped dry.

Causes and Solutions: The causes are complex, mainly including:

No aquifer encountered: The formation itself contains no water, indicating an error in site selection or depth estimation.

Filter pipe not aligned with the aquifer: The well casing was installed in the wrong position, and the screen pipe (filter pipe) is positioned in an impermeable layer (such as clay).

Filter material or well cleaning problems: Improper filter material filling or incomplete well cleaning, resulting in the aquifer channels being blocked by mud and fine particles.

Solutions:

First, check the drilling formation records to confirm whether the target aquifer was reached and whether the casing was installed correctly.

If it is not a geological problem, a strong and thorough secondary well cleaning (such as piston cleaning, air compressor cleaning) should be performed to try to clear the blockage.

If still ineffective, it may be necessary to remove the well casing, inspect and realign the casing, or continue deepening the well at the original location to find a new aquifer.

Situation 4: Well water is turbid and contains a high amount of sand.

Identification: During well cleaning or pumping, the water remains turbid, and a large amount of fine sand settles after sedimentation.

Causes and Solutions: This is usually caused by unreasonable grading of the filter material, improper filling, or excessively large gaps in the filter pipe, failing to effectively block the fine sand in the aquifer.

Solutions: The well cleaning time needs to be extended; sometimes the amount of fine sand will decrease over time. If sand production persists for a long time, it indicates a defect in the well completion process, and a professional team may need to intervene to repair the well or refill the filter material. In severe cases, reconsideration of well completion may be necessary.

Core Principle: For complex situations in the borehole (loss of circulation, borehole collapse, drill pipe jamming), non-professionals should not handle them blindly.  They should be handled by experienced drillers and technicians using professional tools and methods. For problems after well completion (no water, sand production), the responsibility should be clarified with the contractor based on the construction records, and technical remedial solutions should be discussed. Detailed construction records are the fundamental basis for analyzing and solving all problems.