What is Well Surging and Why is it Necessary?

Crucial Safety & Professional Disclaimer

First and foremost, well development, especially surging, is a technical job that should ideally be performed by a licensed and experienced well driller or hydrogeologist. The process involves heavy equipment and a deep understanding of the well's construction and local geology. Attempting this without the proper knowledge or tools can lead to:

• Irreversible damage to the well screen or casing.

• Collapse of the borehole.

• The surge block or other tools becoming stuck in the well.

• Personal injury.

This guide is for informational purposes to help you understand the process, not as a DIY manual.

What is Well Surging and Why is it Necessary?

When a well is drilled, the process pushes fine particles of sand, silt, and clay (known as "drilling fines") into the pores of the surrounding water-bearing aquifer. The well screen itself can also be clogged with drilling mud or natural sediment. If left in place, this clogging dramatically reduces the rate at which water can flow into the well.

Well surging is a development technique that uses a piston-like action to force water rapidly back and forth through the well screen. This vigorous, repeated reversal of flow achieves several key goals:

1. Unclogs the Aquifer: It dislodges the fine particles that are plugging the pores of the aquifer just outside the well screen.

2. Cleans the Well Screen: It clears any blockages from the screen's slots or perforations.

3. Settles the Gravel Pack: In wells with a "gravel pack" (a filter of coarse sand or gravel placed around the screen), surging helps settle and grade these particles into a stable, natural filter.

4. Increases Well Yield & Efficiency: By clearing the blockages, it significantly increases the amount of water the well can produce and reduces the energy a pump needs to draw water out.

5. Prevents Pumping Sand: A properly developed well will produce clean, sand-free water.

   
   

Think of it like vigorously plunging a clogged sink, but on a much larger and more controlled scale.

The Tools for the Job

The primary methods for surging involve a few key pieces of equipment:

• Surge Block (or Plunger): This is the most common tool. It's a heavy, solid disc, often made of rubber or layered leather, that is slightly smaller in diameter than the well casing. It's attached to a drill string or a heavy cable operated by a winch or drill rig.

• Bailer: A long, pipe-like bucket with a valve at the bottom. It's used to remove the sediment-laden water from the well after a period of surging.

• Air Compressor (for Air-Lift Surging): A powerful alternative where compressed air is injected into the well to create the surging action and lift water and sediment out.

• Pump: A submersible pump is used for the final cleaning and to conduct a pumping test to measure the well's performance.

The Step-by-Step Process of Mechanical Surging

Here is a general overview of how a professional would develop a well using a surge block.

Step 1: Initial Well Cleaning

Before surging begins, the driller will use a bailer to remove any loose cuttings and thick mud that settled at the bottom of the well after drilling.

Step 2: The Surging Action

1. The surge block is lowered into the well casing to a position just above the top of the well screen.

2. The driller begins raising and lowering the surge block in long, steady, and vigorous strokes.

   • The Downstroke (Push): This is the power stroke. It acts like a piston, forcing water in the well outward through the screen and into the aquifer, dislodging fines.

   • The Upstroke (Pull): This stroke pulls water and the newly loosened sediment back into the well casing.

3. This up-and-down action is repeated for a set period (e.g., 15-30 minutes). The driller will be careful not to create a vacuum strong enough to damage the well or pull the tool down too fast and get it stuck.

   
   

Step 3: Purging the Sediment

After a session of surging, the water inside the well will be full of suspended sand, silt, and clay.

1. The surge block is removed.

2. A bailer is lowered to the bottom of the well to scoop out the sediment-rich water. This process is repeated until most of the accumulated sediment is gone.

3. Alternatively, an air-lift system or a temporary pump can be used to purge the dirty water.

   
   

Step 4: Repeat the Cycle

This cycle of Surge → Purge → Surge → Purge is the core of the development process.

• The driller will typically move the surge block down the length of the well screen, concentrating on small sections at a time to ensure the entire screen is developed.

• With each cycle, the amount of sediment drawn into the well should decrease. This is a key indicator that the development is working.

Step 5: Knowing When to Stop

Development continues until the following conditions are met:

• The water being purged from the well becomes consistently clear and free of sediment.

• The water level in the well recovers quickly after purging, indicating good flow from the aquifer.

• Continuing the process produces diminishing returns (i.e., very little additional sediment is being removed).

Step 6: Final Pumping and Testing

Once development is complete, a submersible pump is installed to pump the well continuously for several hours. This gives the well a final cleaning and allows the driller to conduct a pumping test to measure its final, stable yield (flow rate) and drawdown (how much the water level drops during pumping). This data confirms the success of the development and provides the basis for selecting the correct permanent pump.