Fact and Fallacy
Originally written for the NGWA toolkit
By Christopher S. Johnson, PG, CHg
Drilling holes in the ground for one purpose or another is easily managed by my
grandson— that is, up to a certain depth, in the right soils, above water, with a long shovel, and with the patience of his grandmother. Once we get deeper than grandson depth, drilling gets more complicated. In fact, drilling holes in the ground is so complex it has advanced several specific fields of science: materials science, mechanical engineering, and borehole geophysics just to name a few.
Entire volumes are dedicated to drill bits, casing, well screen, development, and everything in between. Unfortunately there are few, if any, readily available books on common sense in the well drilling business. As such, we are often confronted with what I will affectionately refer to as “Bob’s College of Drilling Holes in the
Ground” or individuals who learned working with “Bob” and never had the benefit of any other kind of education.
We’ve all met folks like Bob. Flatly stated, these people will simply not let facts influence their opinions. They will press onward despite engineering, chemistry, physics, mathematics, or any other form of unnecessary knowledge.
It’s been said, “Experience is the worst teacher because you get the test first, then the lesson.” Oh, how that is true. Experience teaches us to be cautious.
For example: Drilling Team Omega just changed towers. Senior Driller A tells Relief Driller B to make sure he adds more mud to the tanks before he makes his next connection. Relief Driller B tells the closest hand to see this gets done. Yours truly witnesses this exchange and follows the hand to watch the addition of mud.
One of the more important characteristics of polymer based drilling fluids, especially when used as an additive or the primary drilling fluid, is to provide a means of adequately shearing the polymer molecules to facilitate hydration. It pretty much says so on the bucket, bag, and even in the pamphlet.
This is often accomplished with a high velocity jet of water, to which small amounts of dry, powdered polymer are slowly added. Generally speaking, the absence of “fish eyes” (those globs of unsheared polymer floating in the tank) is a rule of thumb indicator that at least you’ve mostly sheared the polymer.
Our stalwart hand proceeds to dump dry polymer powder into the mud tanks. Gasp! Yeah, he did. And I asked him why he didn’t use some kind of water shear to pull apart the polymer? Deer in the headlights.
Then, to make matters worse, I asked another question, “How come you are dumping that here, almost at the outlet of the mud pits to the conductor casing, rather than back over there?” He dumped his bucket and headed for the drill deck to ask Relief Driller B what to say. Relief Driller B appears, nonchalant and just finishing his first cup of coffee. We nod at each other, and he starts with “So, what’s wrong with how we mix mud?” I begin with an explanation of how polymers need to be torn apart so they can hydrate before going down the hole.
Relief Driller B nods and proceeds to explain, “So, polymers are these long chains of polymer stuff, and when they are powdered up, they get torn a little bit right there. Then, when you put them into the mud pit, all the agitation in the pit tears them up more. Finally, when they head down the hole, all that chaos down there
stirs them up more, and it’s all good!”
I decided to approach this diplomatically. “The instructions on the bucket, along with the instructions on the drilling fluid company documents, all clearly state that proper hydration of the polymer drilling fluids is required.” Blank stare.
Next, I went with the location of the mixing question, “And, how about why are you mixing it right at the outfall of the mud pits to the conductor, and not back there?” I pointed to where the drilling return flow was dropping into the tanks. “Seems you would gain some hydration time if you added back there.”
Experience on that job taught me unsheared polymer is a problem, but a much larger problem was the location where the polymer was added. The dry, relatively unsheared polymer dove headlong down the drill hole, and our best guess is rather then return upwards, these polymers got stuck in the formation.
Breathtaking concentrations of chlorine solution applied during well development could not diminish the residual polymer that had invaded the formations we drilled through. This well did not perform as expected. Two subsequent wells, in similar formations on the same project, produced outstanding volumes of water, thanks in part to a new mud program involving high velocity water sheared polymer drilling fluid added at the back end (mud inflow) of the mud tanks, and a willingness to learn. Back to Relief Driller B. His initial response to the mixing location question was so the driller could watch the hand pour in the polymer.
Now Relief Driller B was a refreshing bit of fresh air because he was willing to accept his opinions might benefit from my facts. He was slightly fazed when I pointed to the part of the documents that read: “Shear thoroughly, using highvelocity water.” But he was downright amazed when I cracked a book and pointed to a diagram stating, “Add stuff here” in reference to where to add drilling mud and additives.
The lessons learned are as follows:
Common sense isn’t always common: Too often we rely on hand me down
knowledge, which can be helpful, but it can also be quite detrimental. If something seems wrong, ask a question. There are no stupid questions, only stupid answers. The easy way is often the wrong way: This is pretty self explanatory, but keep in mind things should be done for the right reason, not to make it easy.
Christopher S. Johnson, PG, CHg, is the president and principal hydrogeologist at Aegis Groundwater
Consulting LLC in Fresno, California. Johnson works with well owners and operators on a variety
ground water related projects, including locating new water resources, well design and construction management, aquifer testing, and well rehabilitation. He can be reached at email@example.com.
The views expressed in this column are the author’s opinions based on his professional experience.