In
my last column, I described some methods to test-pump the fictional well I had
been drilling for several months. As I said then, we really should have
developed the well first and then done the test-pumping, so the procedure that
I am writing about is somewhat backwards. In larger-capacity wells –
irrigation, commercial, municipal and industrial – development may be a
requirement, and a charge for that would be included in the bid price. In many
domestic wells, however, the finished well merely is test-pumped, and while
this may yield a satisfactory product, a properly developed well will be better
both for the drilling contractor and the well owner.
Some drillers believe that just pumping a well at a capacity greater than it
normally will be pumped is a sufficient development. With this, I disagree. The
flow of the water into the well must be reversed to loosen fine material that
then can be brought into the well and removed to waste. Some formations also
will contain minor amounts of native clays, and these really will gum up the
works, resulting in a much-lowered capacity well. Before I describe several
development methods that I have used with varying degrees of success, I give
you a word of caution. Don’t ever presume that giving an effective development
very far out from the borehole or the well screen is going to be easy – it is
not, due to a lot of factors, some of which I doubt anybody
understands.
A popular development method used in my area is the surge block. This is a
sandwich-like device, the cross section of which looks like a double-decker
hamburger. The bun portion at top, middle and bottom is constructed of steel
plate, and the two burger portions (sometimes just a single burger, but usually
a double) are sandwiched between the buns. Our “sandwich” is compressed
together, using a large bolt or pipe thread in the center, or machine bolts
spaced evenly some distance from the center. In actuality, our “hamburgers” are
made of rubber belting or other reinforced rubber material and sized to fit
rather tightly in whatever size casing we have in the well to be
developed.
The surge block is attached to our drill stem in place of the drill bit and
lowered into the well below the static level. The spudding motion is started,
and usually run more slowly than the drilling motion. Sometimes this action
will drive water from the well, and some external water has to be added from
time to time. It is a good idea to run the surge block for a few minutes on the
first trial, and then remove the tools and go down inside the well screen with
a flat bottom bailer and remove any material that has come into the screen. If
the screen is full or nearly full, we can run the block a second, third or more
times until we don’t get much material in the screen, at which point we’ve done
about all we can do with this method. Personally, I never had a lot of really
good luck using the surge-block method, but I do know drillers who swear by
it.
Another method that I have used again with mixed results is to use a tool
called a jetter, consisting of a short length of pipe that will go inside the
screen with its bottom plugged and a series of small-diameter holes drilled
through the pipe walls. This tool is lowered into the screen on drop pipe, and
the pipe is connected to a high-pressured pump. An external water source feeds
the pump, and starting at the extreme bottom of the screen, the tool is rotated
back and forth by hand and raised an inch or so at a time until the entire
screen has been jetted, or the screen becomes full of sand. The tool then is
removed, and the screen bailed out clean. A good high-pressure pump is
necessary for this method to work successfully, as we need a high velocity of
water coming out of our so-called nozzles.
In practice, I had mixed results with this system, too, perhaps because the
pump I was using could not perform to the level needed. The late Bill Anderson,
long-time employee of the Johnson Screen Co. of St. Paul, Minn., who, in my
opinion, was a genuine expert on the subject of well screens and well
performance, once told me that if you had but one method to use in well
development, this jetting method was the one. Bill is gone now and greatly
missed by his friends, so we will take his statement to be an accurate
one.
In the area of Michigan where I have drilled all my life, our water-bearing
formations sometimes contain enough native clay to be a problem. The best
method I found for developing wells made in these formations is to use
phosphates. These products are available through the companies that supply
bentonite and other drilling products. The method I used was to mix some
phosphate product, which I believe was sodium tri-phosphate or sodium
tetra-phosphate – don’t quote me on that; I may be wrong – with fresh water in
a tank using a ditch pump. The phosphates are very difficult to mix with water,
and the material gets very gummy when it is wet. With patience, though, it
could be mixed with several hundred gallons of water, and then pumped through a
drop pipe into the well screen and out into the formation.
A downside of this method is that the solution needs to soak in the well at
least overnight and, if possible, for a couple days. Surging the well right
after injection of the solution seemed to help a lot. I even had a Rube
Goldberg pumping system that worked pretty darn well. Rube Goldberg, for you
younger readers, was a cartoonist from many years ago who was famous for
devising and drawing up extremely complicated systems to perform basically
simple tasks. My system consisted of a surge block made of cup leathers the
size of the casing, one up and one down, and attached near the bottom of a drop
pipe. I usually put an extension down in the screen to pump any fines brought
into it out to the surface. A plunger is run into the drop pipe on a smaller
pump rod as described in my May 2009 article, and the whole assembly is
supported on top of the casing with a coil-type car spring, and moves up and
down in rhythm with the pumping stroke. In effect, I have a surge block and a
pumping system all in one. When I want just to test the well, I remove the car
spring and, of course, the surging stops, and I can pump the well clear. A
further downside of this method was that there was a lot of work involved in
setting it up and tearing it down, but the results sometimes were spectacular
and worth the time spent.
With this last system, I have had some total failures, but more times than not,
I have seen a big improvement and the difference between a successful well and
a failure. In one case, I improved the capacity of the well by a factor 12;
that is, it went from about 2 gallons a minute to 25 gallons a minute. This
brings up a good final point. Sometimes, no matter what you try, nor how many
methods, nothing works, and you end up having to go deeper or perhaps even
move. Such are the frustrations of being a water well
contractor.
I’m sure many of you have your own favorite way of development. If you need to
do some well development and are unsure of what method to use, talk with other
contractors in your area or utilize one of several good books that discuss this
subject, which are available to our industry. I hope I have given my loyal
readers some ideas, and jogged the memory of others. The snows of a couple
columns ago now are only an unpleasant memory, and I need to quit writing, warm
up my John Deere and mow 2.5 acres of grass. My best to all of you.
ND