Historically, most drillers dug two pits prior to drilling a well.
A first pit, called a settling pit, received the drilling fluid and
cuttings from the drill hole via a short shallow trench. The
cuttings settled down to the bottom of the the settling pit. A
second pit, called a mud pit, was dug nearby and a second trench
directed the overflow of the settling pit into the mud pit. Most
of the cuttings settle to the bottom of the settling pit and the
drilling fluid in the mud pit has a much higher liquid to cutting ratio.
Drilling fluid from the mud pit is then pumped, by a mud pump, back down
the drillpipe. During the drilling process, cuttings are
continiously shoveled from the settling pit so it does not become
clogged with cuttings. Although most of the cuttings settle in the
settling pit, it is also necessary to occasionally shovel cuttings from
the mud pit.
The process is well illustrated in this drawing from the Lifewater site
Below is a photograph of mud pits prepared for drilling. This
photograph is from the hydra-jett site. Hydra-Fab manufacturing
http://hydra-jett.com/index.html sells small and medium sized
drilling rigs and is worth looking at if you are considering moving up
to a small rig.
As you might imagine, diggining mud pits is a significant undertaking and
it makes an even bigger mess of your drilling site. Modern
drillers, being both ingenious and capitalistic souls, have devised a
way to avoid this costly, unpleasant step. They bring portable mud
pits to the drill site. A portable mud pit is simply a container
or series of containers that the drilling fluid from the hole is
directed to where cuttings settle out prior to the fluid being pumped
again down the drillpipe. Not only does it eliminate the
time/money consuming digging but it leaves a cleaner drillsite upon
completion of the well.
....but it frequently doesn't work as well for those of us who have
small portable mud pits. Using real mud pits results in more
efficient drilling. There is no leakage around the guide tube with
real mud pits.
Here is an example of a portable mud pit positioned a the back of a
commercial drilling rig. Cuttings from the hole are directed into the
settling pit on the right. Then drilling fluid passes through to
the mud pit on the left and it is pumped back down the hole.
SETUP - PORTABLE MUD PIT
- COMMERCIAL MUD PIT SETUP
There is a wide variety of designs of portable mud pits. Here are
just a few sketches I found to give you an idea of designs that folks
have come up with.
So, by now your are probably wondering, where does all that leave us?
We are not going to buy one of those $500 portable mud pits for our $200
project are we? Absolutely not, in fact you may just be better off
digging your pits. If you are going to dig several wells you
might want to consider using a portable mud pit with a mud pump. I
made one out of wood and it works fine. It is not as efficient as
the commercial mud pits but it does the job. Please take a look at
the video below.
As you can see my portable mud pit is just a wooden box with a fitting
for the suction line and a minor obstruction to keep the cuttings away
from the suction. You can probably come up with a better design
for a portable mud pit that I have. I probably could but it is already
built and I'm not inclined to build another one - but - If I
were doing another one, I'd probably build two boxes that fit inside one
another for easier travel and storage, and then sat beside each other