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Case Study Casing Path Well – An Effective Method to Deal with Cascading Water
Technical Memorandum 004-5 - Case Study Casing Path Well – An Effective Method to Deal with Cascading Water Imprimir
Domingo, 24 de Julio de 2011 17:02

 

Executive Summary

Air entrainment can be a serious problem with the potential to seriously affect a well’s production capacity and the efficiency of its pumping equipment. In a typical air entrainment scenario, water enters the well from an aquifer and cascades downward when the pumping water level is below the top of the well screen. The cascading water entrains air during its freefall and causes the pump to cavitate as the mixture of air and water passes the pump impeller. Cascading water and entrained air can be controlled by using the casing path well design. This unique approach has been shown to be very effective in many areas within the Southwest.

 

Background

In the 1980’s well owners and operators in California’s San Joaquin Valley began to notice that many water wells were losing production and also pumping water with entrained air. At that time (as now), it was not uncommon to pump water from shallow, unconfined aquifers and deep, confined aquifers in the same well. During that period, as demand increased for agricultural water in the Valley there was a marked decline in ground water recharge caused by reduced rainfall. These man-made and hydrologic conditions directly resulted in the lowering of ground water levels in many areas of the Valley. As static water levels declined in the Valley, pumping water levels in many wells were lowered below the top of the well screens. Consequently, as water entered the wells it would cascade downward and in doing so, air became entrained.

Entrained Air

Entrained air occurs in a well when the pumping level is lowered such that it produces a significant difference between the water level in the well and the water level in the adjacent aquifer. When this occurs, a seepage face is created between the saturated aquifer(s) exposed to the air space between the screened section(s) of the well. As the water enters the well it cascades, i.e., falls, downward to the pumping level. As it does so, air is entrained in the water. Then, when the well is pumped, the entrained air can cause the pump to cavitate and the discharge water with air.

Casing Path Well Design

A casing path well is designed to allow for concurrent production from a shallow aquifer and depth aquifer. Figure 1 is a typical casing path well design showing its key components, which consist of:

1. An upper exterior casing/screen segment that is installed within the upper aquifer zone;

2. A short reducer connected to the upper segment;

3. A lower casing/screen segment that is installed within the lower aquifer zone;

4. An interior casing sized to accommodate the pump bowls; and Roscoe

 

ENVIADO POR RAÚL CAMPILLO U., HIDROGEÓLOGO.

 

 

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