TAPS permits injection at higher pressure and is a relatively simple and inexpensive system that relies on only one specialty piece of equipment. These all operate on the fundamental fact that gravity separation of gas and water efficiently occurs in the annulus as formation fluids enter the wellbore. The simplest DGWS device is a bypass tool in which the bottom end of an insert sucker rod pump is seated. The pumping action loads the tubing with water from the casing tubing annulus. When the hydrostatic head in the tubing is great enough, the water drains into the disposal zone below the producing perforations and packer.
Gas flows up the tubing-casing annulus.
A second type of rod pump-operated DOWS system is termed the modified plunger pump. On the downstroke, the plunger moves the fluid down and out of the barrel and into a disposal zone below the packer. ESPs provide for very high flow rates and are generally more economic in deeper wells. For water production rates less than 50 bpd, conventional surface disposal is most cost effective. Bypass tool systems are more cost effective in the 25-250 bpd range, up to a maximum depth of about 8,000 feet.