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Down-Hole Perforating: A Technique to Increase Water Production from Existing Wells
Technical Memorandum 004-6 - Down-Hole Perforating: A Technique to Increase Water Production from Existing Wells Imprimir
Domingo, 24 de Julio de 2011 20:00



Today’s well-refined methods of well design, drilling, construction and development commonly result in water supply wells that are efficient, reliable, and productive. However, on occasion a well may fall short of these ideal results despite the best applied design and construction efforts. This memorandum describes an approach that has the potential to improve water production by using a down-hole perforator to increase the linear footage of open area and expand the production zones of the well. Assuming that the site-specific hydrogeology and ground-water levels are favorable for this approach, marked improvement in the well’s performance can be realized at a relatively low cost.


In the case of a completed well which yields appreciably less than its pre-design forecast, it may be advisable to revisit the well-specific data, including the following:


• well driller’s log

• geologist’s lithologic log (if prepared)

• down-hole geophysical log

• as-built well design

• pumping test results

• water quality results

Well Logs. During the drilling of the borehole, the driller and geologist (if assigned to the project) visually analyze the cuttings that were returned from the hole and independently prepare well logs. The logs consist of concise physical descriptions of the cuttings and estimated depths for the top and bottom of each zone that encountered. A typical geologist’s log provides important notations on the size, angularity, and sorting of each geologic unit.

These are key parameters when one re-evaluates a potential water-yielding zone that was not screened and is not as yet a source of water for an existing well.

Geophysical Log. The down-hole geophysical log typically includes resistivity logs and a spontaneous potential log. These two logs are interpreted to determine the top and bottom of each water-bearing unit and nonwater-bearing unit. The geologist’s log (and/or driller’s log) is used in conjunction with the resistivity and spontaneous potential logs to interpret the results.

As-Built Well Design. This design drawing shows key below-ground details of the well including (but not limited to) the current depth intervals of blank casing, well screen, gravel pack, annular fill, seal(s), and sounding tubes. It also shows the gradation of the gravel pack, slot size of the louvers or wire-wrapped well screen, and casing thickness.

Pumping Test Results. These data indicate the depth of the static water level, pumping water level, well yield, and specific capacity.

Water Quality. Depending upon the suite of analyses performed on water samples from the well, the test results may show the physical and chemical parameters that characterize the...