27 Jan 00
development and redevelopment in well maintenance is difficult to emphasize enough. Proper well
development breaks down the compacted borehole wall, liquefies gelled mud, and moves both mud and
formation fines into the well, from which they are removed by bailing or pumping. This action creates a
more permeable and stable zone about the screen or intake bore. The stabilization of the formation
adjacent to the well intake that is achieved by development can practically eliminate sand pumping, and
contributes to a more efficient well, longer well life, and reduced operation and maintenance costs. EM
1110-2-1914 and TM 5-813-1 provide general guidance on well development. Numerous detailed
references on development methods are available, including ADITC (1997), Driscoll (1986), and Roscoe
Moss Company (1992). Borch, Smith, and Noble (1993) provide information and guidance from a
redevelopment perspective. NGWA (1998) provides specific pumping well methods description and
c. Well development and redevelopment methods.
(1) Overpumping. The development process consists of continuous or intermittent pumping at
pumping rates up to 1-1/2 times the design capacity. Overpumping lacks the necessary in-and-out action
of optimal development action but can be conducted with available well pumps.
(2) Surging and bailing (utilizing surge block). The development process is carried out by surging
and bailing the well. The surging is done by a single or double solid (or valved) surge block with
development water and sediment removed typically by airlift pumping. Surging should be conducted with
tools capable of a 0.3- to 0.6-m/sec (1- to 2-ft/sec). stroke and capable of working the screen in 0.6- to
1.5-m (2- to 5-ft) sections, concentrating on known trouble spots. One variation is swabbing (e.g., Roscoe
Moss Co., 1992).
(3) Surging and pumping. Where there is insufficient submergence for airlift pumping to work
properly, development can proceed using surging and pumping with a well pump. Pumping is conducted
through the surge block which incorporates a piece of the suction pipe in the fabrication of the block, at
rates up to one half of the design capacity. Upon completion of the development work, the well is cleaned
to the bottom. A variation of surging and pumping and overpumping, especially useful in tight wells,
employs a well pump moved up and down with a reversible pump puller. Pumps especially equipped for
this purpose with attached surge block collar, etc., are available. Care must be taken to ensure that air
does not enter the formation, but is only used to move fluid, which carries the kinetic development force
(see paragraph 9-5e).
(4) Hydraulic jetting. Development is accomplished by simultaneous high velocity, horizontal
jetting and pumping. The outside diameter of the jetting tool must be 1 in. (about 25 mm) less in diameter
than the screen inside diameter. The minimum exit velocity of the jetting fluid at the jet nozzle should be
150 ft/sec (45 m/sec). The tool is rotated at a speed less than 1 rpm and positioned at one level for not
less than 2 min and then moved to the next level, which is no more than 6 in. (150 mm) vertically from
the preceding jetting level. Pumping from the well should be at a rate of 5 to 15% more than the rate at
which water is introduced through the jetting tool. Water to be used for jetting must contain less than 1
ppm suspended solids.
(5) Air development. Development is conducted:
Using a single pipe air pumping system either using the casing or the bore hole itself as the
eductor line (casing open) or with the casing closed to the atmosphere.
With a dual-line air system employing an air introducing pipe and an air and water eductor