Dear readers, two columns back, I wrote about some unusual casings I have encountered in my career in Southern Michigan. This column will discuss two more unusual types.


Case #1: Thinwall 4 

The first one I want to write about is what I will call thinwall 4”. Now this was 4-1/2” OD galvanized casing with a thinner wall than standard 4”. I believe standard 4” has a wall thickness of .237”. If I’m not mistaken, this thinwall type had a wall thickness of .1875” or 3/16” plus or minus. I believe this thinwall casing had a finer thread type to avoid nearly cutting through the wall when threading. I encountered this thinwall casing on some pump replacement jobs in far Southern Michigan. Of course, with the thinner wall came a larger ID which was a good thing when installing a 4” submersible pump. The cable guard and motor diameter on many 4” submersibles made it a tight fit in a typical 4” well, so the extra ID was more than welcomed.  

How much heavy driving this thinner wall pipe could stand is something that I don’t know. These wells were over 150 feet deep, as I recall, and were drilled by cable tool so that the thinwall must have stood up okay. The wall thickness of this pipe was comparable to that of a standard 2” Schedule 40 pipe. My dad drilled quite a few 2” wells to over a 200-foot depth, and the casing stood the driving, so probably the 4” thin wall was just as robust as the 2” standard. I have only seen a couple of these thinwall-cased 4” wells in my career and don’t really know why that casing was selected. 


Case #2: 4-1/2” ID Well With Cable Tool-Drilled Couplings 

Another really unusual casing that I saw only once was a 4-1/2” ID well with couplings on the inside drilled by a cable tool machine. Another veteran cable tool driller and I were invited to watch this well being drilled. The contractor was a very competent and well-known cable tool driller. He was at least a second and maybe a third-generation driller. He had a spudder-type rig that was plenty big enough for the job, and it had an extra tall mast and other custom features he had added. The tall mast allowed for a long string of tools, which was a desirable feature as weight on the bit is a significant factor in cable tool drilling. This man was known as ‘Mr. Cable Tool’ in Michigan, and as far as I know, he is still alive but retired. He was a very good cable tool driller and a strong advocate for that type of drilling. 

This drilling contractor obtained some plain-end steel casing that was 4-1/2” ID and 5” OD. As I recall, it was in 20-foot lengths or perhaps 21 feet, a standard length of a section of steel pipe. He cut up some 4” ID by 4-1/2” OD sections of pipe (Schedule 40 pipe) into pieces about a foot or 1-1/2 feet long. He inserted this into one end of the larger pipe and attached it with a fillet weld. 

A fillet weld is much easier to make than a butt weld, in my opinion, especially in the field. His rig had enough mast that he could get his tool string up and into a 20-foot section. He would insert a new section of the so-called coupling (the smaller pipe) into the lower section and complete the joint by welding. He would then proceed to drive the whole darn thing into the ground, and with a long string of tools, he could easily do this. 

I don't think he reamed the smaller coupling sections, so when he lowered his tool string to drill out the end and his baler to recover slurry, you could hear them going "clunk, clunk, clunk" down the casing. The cable tool driller who accompanied me that day and I never quite figured out the purpose of this “couplings on the inside” method. It possibly had something to do with grouting issues. I think the contractor drilled only a few wells by this method and then went back to the standard “couplings on the outside” method or butt welding his casing. He called the “coupling on the inside” method ‘Smooth Sleeve Casing.’

The grouting of cable tool drilled holes I referenced above was a hot topic in Michigan in the 1980s when this all took place. Up til then, with the exception of high rock areas where cement grout was placed around casing that was lowered into an oversized hole, most all casing in drift conditions was just hammered in and left that way. 

Questions were asked about holes drilled in clay and whether the clay adhered to the casing wall after a coupling went through it, making a larger hole. I will discuss how this was settled in my next column, as attempting to do that would make this column way too long to read. Stay tuned for the next chapter. 


Michigan Weather Watch 

We have had a strange winter here in Michigan with a lot of nasty cold rain and only one decent snow that melted quickly. In the middle of March, our lawns are pale green and are not growing in these frigid temperatures, sometimes in the 60s during the day and low 30s at night. 

This will probably change and we will get our fair share of snow—we always have in my years on earth. For the drilling industry pros out in the field right now, fingers crossed the weather levels out, and that sunshine and rainbows are headed our way. 

Stay tuned for the next chapter of ‘drilling the way it used to be.’