Date of Award

2001

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

S.F. Korom

Abstract

Greater well efficiency and lower production costs may result from a knowledge of water flow through well screens. Current practice generally locates the intake of a pump in the cased section of the well above the screen. This work shows that placing the pump within the screen will increase well efficiency and therefore lower energy cost. This work also shows a correlation of increased well efficiency with respect to larger sand size, larger screen slot size, and lower flow rates.

A semicircular model based on the radial symmetry of a well and screen was used to simulate water flow from surrounding aquifer material. Pump intake location was varied between experiments. Two sand sizes, 12-20 and 16-30, were used for the experiments with a 0.25-mm screen slot size. The larger sand was used for experiments with two screens of 0.51-mm and 0.76-mm slot sizes. Hydraulic head data were recorded in twenty piezometers in a vertical cross section in the sand during experiments. The data were gridded and contoured and the resulting plots used to infer direction of flow. Data sets with different intake locations but identical well discharge, screen sizes, and sand size were subtracted from each other to examine the effect of intake location on head. The efficiency of different well configurations was determined comparing drawdown within the well to the hydraulic head in the aquifer surrounding the well.

For the experiments done in this study, flow through well screens was concentrated around the pump intake. The magnitude of this preferential flow increased with the pumping rate. Higher pumping rates were less efficient than lower pumping rates regardless of screen, sand, and intake location. This work suggests that pump intakes placed within the well screen are more efficient than intakes placed inside the cased section of the well. Of the intakes located within the screen section of the well the one 87 cm within the well screen was more efficient than the one only 26 cm within the screen. The larger the open area of a well screen, the more efficient flow will be through that well screen.

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