Identification and Response Suggestions for Common Conditions During Well Drilling

Identification and Response Suggestions for Common Conditions During Well Drilling

When drilling a well for domestic use, the underground conditions are difficult to predict completely, and various different geological formations and unexpected situations are often encountered during construction. Understanding how to identify these common conditions and knowing the basic response principles will help you communicate effectively with the construction team, make joint decisions, and ensure the smooth progress of well drilling and the quality of the finished well.

I. Soft Strata (e.g., clay, silt)

Identification characteristics: Fast drilling speed, low resistance; the cuttings brought up are paste-like or fine-grained; the well wall is prone to self-closing, which may cause the drill pipe to become stuck.

Response suggestions:

Use a suitable drill bit (such as a spoon-shaped drill or auger drill) to improve slag removal efficiency.

Control the drilling speed to avoid the drill bit getting clogged or the well wall collapsing due to excessive speed.

Use drilling fluid (or clean water) in a timely manner to protect the well wall and stabilize the wellbore.

If the well wall is unstable, consider using casing before lowering the well pipe to prevent collapse.

II. Loose Sand Layer (e.g., quicksand layer)

Identification characteristics: The drilling feels "unstable," a large amount of sand gushes into the hole, the well wall is extremely prone to collapse, and almost pure sand is brought up; the water level may rise rapidly.

Response suggestions:

This is a more challenging condition. High-quality, high-viscosity drilling fluid must be used immediately, and its density may need to be increased to form a strong mud cake to block the quicksand.

Adopt a "rapid passage" strategy to reduce the time spent in this layer, and prepare a sufficiently long casing to follow up at any time to isolate this layer.

When lowering the pipe later, a high-quality filter pipe must be used at the corresponding position in this section, and ensure that the backfill filter material (gravel) has good gradation to stabilize the sand layer and ensure clear water output.

III. Cobble and Gravel Layer

Identification characteristics: Difficult drilling, slow and uneven progress; increased machine vibration and noise; the cuttings brought up are broken stones of varying sizes; drill bit jamming or drill tool bouncing is likely to occur.

Response suggestions:

Switch to an impact drill bit or drilling tools specifically designed for hard and broken layers.

Appropriately increase the weight of the drilling tool and use a "impact combined with rotation" method to break the stones. Drill slowly and carefully, paying close attention to the condition of the drilling tools to prevent pebbles from jamming the drill bit. Frequent drill string retrieval and cleaning may be necessary.

This layer is prone to mud (drilling fluid) loss; replenishment is required.

IV. Hard Bedrock Layer (e.g., granite, limestone)

Identification characteristics: Extremely slow drilling speed, almost no penetration; high machine load, muffled sound; the retrieved cuttings are hard rock powder or small rock fragments.

Recommended actions:

The drill bit must be replaced with a roller cone bit, alloy bit, or professional core drill bit.

Adjust drilling parameters, appropriately reducing rotation speed and increasing pressure.

Maintain smooth mud circulation to cool the drill bit and carry out rock powder.

Assess whether this rock layer is an aquifer. If so, drill a longer section in this layer to increase water yield; if not, and the depth is sufficient, consider completing the well.

V. Common Abnormal Working Conditions

Drill string jamming (drilling tools stuck in the well):

Identification: The drilling tools cannot rotate, cannot be lifted, or have very limited movement.

Recommendations: Do not forcibly lift or twist to avoid aggravating the situation. Immediately try moving the drilling tools in different directions, or use a "shock absorber" to free the jam. If ineffective, professional personnel need to use special tools such as reverse-threaded drill rods.

Lost circulation layer (large amount of mud/water loss):

Identification: The mud or water pumped into the well does not return to the surface, and the liquid level in the well drops.

Recommendations: Assess the severity of the loss. Try adding plugging materials (such as sawdust, clay balls, or special plugging agents), or switch to a thicker mud. In case of severe loss that cannot be sealed, it may be necessary to install casing to isolate the layer, or consider changing the well location.

Water/sand influx:

Identification: A large amount of water or sand suddenly gushes out of the borehole.

Recommendations: If it is clear water, it is a good sign, indicating that a water-rich layer has been encountered, but the speed needs to be controlled. If it is sand influx, it is very dangerous and must be immediately controlled with high-quality mud or casing, otherwise, the wellbore may be ruined.

Summary and Core Principles:

Maintaining calm communication with the construction team is crucial when facing different working conditions. As a user, you need to understand that it is normal to change drilling tools and methods for different geological formations, which will incur additional costs and time, and should be initially agreed upon in the contract. Your role is to stay informed of changes in the situation, jointly assess risks and costs with the contractor, and make informed decisions regarding significant plan adjustments (such as adding casing, changing drill bits, or significantly deepening the well). A good construction team will proactively explain the working conditions and proposed solutions to you. Maintaining this collaboration will maximize the chances of drilling a successful water well.