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August 2017 – Directional Water Wells, Really!

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Directional Water Wells, Really!

Horizontal directional drilling (HDD) methods have been utilized for environmental and engineering applications starting in the late 1980’s. Since then, HDD wells have been installed for a wide variety of environmental and geotechnical applications.

One industry that has not significantly utilized HDD drilling and well installation methodology is the water supply industry. Over the last twenty years only a handful of high capacity water wells have been installed using HDD technology, compared with hundreds of environmental and geotechnical wells. Most of these water supply installations have been in relatively shallow aquifers with direct connections to surface water bodies.

It has long been recognized that horizontal wells allow significantly more screen to be placed into the production zone of a thin aquifer than vertical wells. But so few horizontal wells have been installed for water supply, that municipalities and industry has been hesitant to apply the technology. Directed Technologies Drilling (DTD) is transforming this market, and has recently completed two water supply projects of note.

Texas – DTD was contracted to install a horizontal water supply well for use at a power plant. The well, completed in July of 2017 is 2,300 feet long with 500 feet of screen set at 190 feet below ground surface. For this installation, a continuous (entry/exit) drilling method was used, with the screen and casing pulled into the borehole in tension. The well screen is twelve-inch diameter steel, specially designed to have the required strength to withstand the rigors of the installation. The custom screen can be generally described as a pipe-based, wire-wrapped screen.

Mud rotary drilling methods with a bentonite-based drilling fluid were used to drill the pilot hole and complete the multiple reaming passes. Well development combined both chemical and physical methods including airlift, jetting and overpumping along the length of the well screen. The development process for a well with a screen like this is lengthy, and in this case took several weeks.

Once well development was completed a series of pumping tests were performed to quantify the sustainable yield. Based on the pump tests, the yield of the well will be between 650 and 1,000 gpm 10 times the production of nearby 16″ vertical wells.

Colorado – DTD drilled and installed six potable water supply wells for a Front Range community in Colorado. The wells were completed in a surficial aquifer, hydraulically connected to a perennial stream. Five of the wells were installed adjacent to vertical wells; i.e. a horizontal vertical couplet. In this configuration, a submersible pump was placed in the vertical well and the long horizontal screen next to the vertical well served as a lateral to enhance water flow. One of the wells was constructed without the vertical well component. The individual flow rates from the six wells averaged about 60 gpm.

Horizontal directional drilling methods can be used for industrial, agricultural and potable water well installations. Placing long screens horizontal or nearly horizontal has many benefits when compared to traditional vertical water wells in unusual settings, such as shallow or thin aquifers or aquifers connected to surface waters.