In my last column, I wrote about the need to pull casing from the ground. Maybe you drilled a dry hole, or need to remove bent pipe or set a well screen by the telescoping method. I previously talked about two methods for casing not too tight in the ground: the slotted pulling head and pipe pulling jars. For casing driven down deep and really tight in the ground, we may want to use one of two other methods.
Here, I focus on the first: a very popular tool called a casing spear (or, sometimes, trip spear). You can lower this tool to any position inside the casing and teeth expand to grip that inside. You need to use long-stroke jars just above the trip spear with a drill stem and rope socket above the jars. The stroke of these jars needs to be longer than the stroke on the machine, and the operator would generally set the stroke at its shortest length. Small water well rigs have a short stroke of about 18 inches, so we would need to select jars made for a stroke of at least 24 inches or, preferably, 30 inches. The reason for this is that the casing spear is adjusted at the surface to slide down inside the pipe.
When reaching the point where jarring will be used, the driller pulls up on the tool string and the pulling slips engage the pipe. After some light, almost tap-like strokes on the jars, you can apply full power to them and the teeth will dig into the pipe and grip it, moving it toward the surface. To release this tool, you stop jarring and apply a few downward blows. That causes a spring in the spear to retract the jaws, and you can then pull the tool and the string itself to the surface — either because pullback finished or a section of casing needs removal. Avoid pulling from the same point in the casing every time you use the spear, as this might elongate the casing and ruin it.
Another reason for the long-stroke jars with a stroke of a fair amount longer than the stroke of the machine stems from downward force on the spear. Too much force can trip it, and then it has to be pulled from the casing and reset. This resetting is one of the disadvantages of this tool. I never owned a trip spear but I did borrow one on occasion, even rented one from a tool company. I found setting the jaws difficult — in fact, almost tricky. This setting adjusts how large of diameter of pipe the trip spear will engage. If set too light, it will not engage the pipe and be ineffective. If set too heavy, the spear will not disengage, complicating the driller’s problem. At least one manufacturer I know of advertises that their trip spear easily adjusts for different casing weights. I believe they have notches on the setting ring, a part of the spear. Other manufacturers use wood blocks to hold the jaws closed and they are quite tricky.
The big advantage of a trip spear comes from placement. You can lower it to the lowest part of the casing before engaging it. This is where the casing is tightest and the upward blow most effective. Casing has a springiness in it so that a blow at the top — as I wrote about last time — has affect than a blow near the bottom.
Another point about setting the machine to use the trip spear: If it has an adjustable stroke, set it in the fishing or pulling position with a fast rise and a slow drop. This is just the opposite of the drilling stroke. On a machine without this adjustment feature, the driller should select the shortest stroke possible. Under extreme conditions, he might go to medium stroke (with suitable fishing jars) but it is best to use the short stroke.
Most cable tools are pretty rough, tough and simple. They don’t have moving parts and, with properly set up joints, work very well. Not so for the casing spear. I find these spears difficult to use. If you use one, follow the manufacturer’s instructions to the letter. For example, one basic requirement is that the tapered “ways” that the jaws slide on need to be very clean and nicely lubricated.
Manufacturers make trip-type casing spears to pull 3-inch ID pipe all the way up to 16-inch OD casing, which covers just about all the water wells drilled in the United States and abroad.
This wraps up my thoughts on casing spears. Next time, I’ll get into yet another method to pull casing from the ground: the casing ring, a tool whose use and, indeed, selection is not simple.
As I write this very late July, we continue to have a rather nice summer in southern Michigan. We have had warm and slightly hot weather, but not terrible heat and high humidity. I know some of you in other parts of the country have had just terrible heat, and I feel for you. I also understand that drought is too prevalent in other areas. We have had enough rain to keep my infamous lawn green, although the buckhorn keeps coming back. Nearby corn and soybean fields look good and, if the weather holds, I think the farmers will have a good year. Until next time, work hard, work safe, enjoy life and remember pulling casing is just part of the job.
For more John Schmitt columns, visit www.thedriller.com/schmitt.
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