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How to tell if a well is properly developed?: The Specific Drawdown Method
How to tell if a well is properly developed?: The Specific Drawdown Method Imprimir
Sábado, 05 de Noviembre de 2011 13:10

1.   Introduction

Regardless the method used for drilling a well, the development is the most relevant operation for the successful completion of a good groundwater well, assuming its design and construction have been duly performed. Good design is a more complex task than usually thought.

Many drillers know how to properly design a well and there is ample technical literature on the subject, however the latest information is not sufficiently widespread locally. Updating design techniques is essential.

Few drillers are in a position to assert they have satisfactorily completed the development of the wells they drill. The reasons are several and they are listed below, in no particular order.

- Many contracts specify a development of a fixed amount of hours, especially in those wells performed under a ‘lump sum’ contract, which is very functional, but technically illogical, as wells are not subject to any Construction Quality Control. If too many development hours are included in the offer, you may lose the tender due to pricing concerns, and nobody wants to run such a risk, especially when there aren’t so many jobs around!

-     Other drillers apply standards such as “a silting lower than 10 centimeters of sand per meter of screen or slotted pipe installed in the well, per hour of development” (sic), with these drillers not knowing that this standard used to be applied to wells drilled with the percussion method and completed with slotted pipes; then and now there not being any satisfactory technical explanations about the origin of this standard, which only for being so much widespread, is believed to be correct.

-     Most drillers don’t know how to scientifically verify that a well is fully developed, or don’t have the necessary tools to so, and consequently the well Efficiency is not adequate.

-     Methods for calculating well Efficiency, which demand monitoring wells, are impracticable due to high costs.

 

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