Saturday, May 2, 2009

Getting wet

We arrived at the well site on Friday slightly before Boyd showed up. First thing he did was measure the static water level in the well. It came in at ~260 feet deep! If you refer to my amateur drawing a couple of posts ago, you'll see that the top of the aquifer was around ~290 feet. The well water could only have risen to 260' if there was at least some pressure from the aquifer to push it up that high. Boyd said that this means the well is slightly artesian; most people associate "artesian well" with a well that bubbles by itself onto the ground surface, but it can also be any well that has sufficient pressure to pump water some distance toward the surface. This is another positive indicator of the quality of our well, which I am very happy about.

Next he fired up his rig to do some more well development. This is kind of a cool movie sequence:

Clearly I was standing in the wrong place. Note how well Boyd was able to hide himself behind the edge of the rig too. To be fair, he did warn us all to get off to the sides of the rig, but I was too curious for my own good. :)

Part of developing the well involves filling the well casing with water, which (by gravity) forces water from the area around the well screens back into the surrounding aquifer. By reversing the flow, then pumping the water out again, you get a flushing action which helps to clean the aquifer, and to remove more of the fine particles. Boyd has a thousand-gallon water tank for this purpose (this is his helper Robert getting ready to open the valve):

I was expecting him to use a pump, but he simply connected a hose to the tank and set it over the cone-shaped drill stem threads, then let gravity take over:

On the previous day, Boyd had put 500 gallons of water into the well casing and seemed pleased with how fast the water had flown back into the aquifer. To figure out what this really meant, I crunched some numbers. This is an 6" diameter casing, so divide that by two to get the radius, then convert it to feet by dividing by 12, then square it and multiply by pi to get the horizontal area in square feet:

6"/2 = 3"

3"/12" = .25 ft

(.25 ft) ^ 2 = .0625 ft^2

.0625 ft^2 * 3.14 = .19635 ft^2

Let's pretend the empty part of the casing is 260' high (per the static level discussion above). So, .19635 ft^2 times 260, gives us a volume measurement of 51.1 ft^3. There are 7.48 gallons of water per cubic foot, so that results in a total figure of 51.1 ft^3 * 7.48 = 382 gallons. (All figures approximate, and no warranty is expressed or implied.) So when Boyd poured in 500 gallons, this was clearly enough to overflow the casing had the aquifer not accepted the backflow. This is another positive indicator :). Anyway, while we were there on Friday he put an additional 200 gallons into the well. After that we had to leave.

No comments:

Post a Comment