What could be causing low water yield or turbid water in a newly drilled well?

What could be causing low water yield or turbid water in a newly drilled well?

Insufficient water yield or turbid water in a new well is often related to improper handling of key aspects of the drilling process. Understanding the potential causes will help you communicate effectively with the construction team and seek solutions.

I. Possible Reasons for Low Water Yield

* **Failure to reach the target aquifer:** This is the most common reason. The drilling depth may be insufficient, failing to penetrate the impermeable layer to reach the water-rich sand layer or fracture zone. Alternatively, the groundwater resources at the drilling location may be limited.

* **Improper placement of the filter pipe:** The filter pipe (commonly known as a "spread pipe") is not accurately aligned with the water-bearing sand layer or fracture zone, but is placed in a relatively impermeable clay layer, resulting in obstructed water intake.

* **Improper filling or blockage of the filter media (gravel):** The filter media (quartz sand) filling the space between the well casing and the well wall may be of mismatched specifications, unevenly filled, or contain excessive soil, failing to form a good natural filtration layer and instead blocking the water intake channel. Sometimes, excessively thick drilling mud during construction can form a "mud cake" that clogs the aquifer.

Incomplete well washing: At the end of drilling, insufficient, forceful, and prolonged well washing fails to effectively remove fine sand and mud from the wellbore and aquifer, leading to blocked water flow.

II. Possible Causes of Turbid Water (Containing Sand and Impurities)

* Filter pipe or filter media layer failure:

Filter pipe pores are too large: Ineffective at preventing fine sand from entering the aquifer.

Improper filter media gradation or insufficient filling: Failure to form an effective transition filter layer outside the well casing allows sand particles from the formation to directly enter the well.

Incomplete well washing: This is the primary cause of persistent turbid water from new wells. If the washing time is short or insufficient, a large amount of drill cuttings and mud remaining in the well cannot be removed, resulting in persistent turbidity.

Cementing (sealing) failure: The upper part of the filter media layer was not properly sealed with high-quality clay balls or bentonite, allowing sewage and impurities from the upper soil layer or near the surface to seep into the well along the outer wall of the well casing, contaminating the water source.

Well casing rupture or leakage at connections: Damage to the well casing during installation or loose connections allowed sediment from the formation to flow directly into the well from the damaged area.

Pump installation too low: The pump inlet is too close to the bottom of the well, drawing in sediment deposited at the bottom.

III. What to do? – Preliminary assessment and action recommendations

Contact the original contractor: First, contact the drilling team and clearly describe the problem (when it started, the degree of turbidity, and specific water volume data).

Request a second well flush: For turbidity issues, the primary and most economical solution is a thorough and professional second well flush (usually using an air compressor or high-power pump for vibration and jet flushing). Many persistent turbidity problems can be resolved with powerful well flushing.

Verify construction records: Review basic formation records and well completion diagrams to determine the rationality of the filter pipe location.

Consider professional inspection and repair: If re-washing the well is ineffective, a professional team may be needed to use downhole television inspection to determine if the filter pipe is damaged, the filter media layer is faulty, or repair measures such as patching or pipe replacement are required. For water volume issues, deepening the well or re-drilling in a different location may need to be considered.

Summary: Prevention is better than cure. Most problems stem from oversights in the construction process. Therefore, clearly defining material standards and procedural requirements (especially well washing and acceptance standards) in the well drilling contract, and personally supervising key stages such as casing installation, gravel filling, isolation, and well washing, is the most effective way to prevent these problems. If problems arise, communicate promptly and begin investigating the most likely cause: incomplete well washing.