In my last few columns, I described tools we would need for a cable-tool drilling program in addition to the components that make up our drill string. There are just a whole lot of different tools we will need for a successful drilling operation.
As we drill hole and add water, the drill tools form a slurry. After a few feet — or, perhaps, quite a few feet — we have to remove that slurry from the hole. For this, we need a bailer, a piece of pipe or tubing smaller than the inside diameter of the casing we use. Bailers vary from 2½-inches OD for 3-inch ID casing all the way up to 14-inches OD for 16-inch ID casing. Bailers range from 10- to 30-feet-long, and weigh from 40 to 1,000 pounds depending on the length and diameter. Drillers can also use bailers, in a limited capacity, to test pump a completed well.
Most bailers feature a dart valve at the bottom that looks similar to the intake or exhaust valve of an engine, though much larger in diameter. When the bailer reaches the bottom of the hole, this valve opens as the dart portion of the valve extends beyond the bottom of the bailer itself. This allows slurry or water to enter the bailer. The valve closes when the bailer raised off bottom, keeping the bailer full. The operator pulls it to the surface and discharges the contents on the ground or, better yet, into a tub or trough. Removing as much slurry as possible often requires running the bailer several times. The tub or trough can be of most any design as long as it keeps the slurry from around the casing.
The top of the bailer features — surprise! — a bail. This U shaped piece of steel from 6- to 12-inches-long welds or rivets to the bailer itself. The sand line on the rig attaches to the bailer at the bail. I found it most convenient to use a bailer link for this connection, but any way you attach the line to the bailer should work. A bailer link looks a little bit like a paper clip made of solid steel bar. One side opens to attach to the bail. I’ve used several designs, and every driller has a favorite, but these links help immensely when using different sizes or types of bailers. Bailers can hold anywhere from 2½ gallons of fluid or slurry for the smallest 3-inch hole up to roughly 72 gallons for the largest 16-inch hole. As slurry can weigh 10 pounds per gallon or more, these large bailers get very heavy when full. Needless to say, a 16-inch hole requires a big rig. Most any driller would own bailers of several diameters and lengths for their drilling program.
Flat-Bottom Bailers in Drilling
When running either a dart-valve or flat-bottom bailer, when you reach the bottom of the hole raise it a foot or two and let it drop several times before raising to the surface.
Next, I want to talk about the shorter flat-bottom bailer. While not as popular as the dart-valve bailer, it also comes in many different diameters. It features a flat bottom, or flapper, in place of the dart valve. The flapper functions much more effectively than the dart valve in sands and gravels. The flapper also cleans out closer to the bottom of the hole than the dart valve can. This feature helps when baling inside a well screen to remove sand pulled in through development. The flat-bottom bailer has the big disadvantage of having to be tipped or upset to dump, hence the shorter length.
For best results when running either a dart-valve or flat-bottom bailer, when you reach the bottom of the hole raise it a foot or two and let it drop several times before raising to the surface.
Sand Pump Bailers in Drilling
A third type of bailer called a sand pump or vacuum bailer shares the tubular construction of the dart-valve or flat-bottom types, but has a plunger inside attached to a rod that comes out the top. This bailer excels in sand and gravel. It lowers to the bottom of the hole and the plunger goes to the bottom of the bailer. When raised, the plunger creates suction, pulling sand and gravel into the bailer proper. Operators can do this once or several times on each trip to the bottom.
These bailers have a removable bottom, usually a flat type, that allows contents to drop out when removed. Depending on the formation, water levels in the casing and other factors, these bailers can vary from very effective to extremely ineffective. If we drill in sand and gravel, I’d call having one of these vacuum bailers or sand pumps essential to the operation. They are usually no more than 10-feet long.
Remember, regardless of type, every bailer varies in effectiveness with the geology and the characteristics of the hole.
Next time, I will write about more essential tools for a cable-tool operation: the drive blocks and their companion, the drive head.
The calendar says it is spring all over but, in southern Michigan, Mother Nature says, “Not so fast.” We have had one or two warm days, but it has generally been cold. As I write this in very early April, yesterday we had a light snow falling. (In fact, as I write this my running geothermal heat pump keeps my office cozy and warm. Spring will get here eventually and, when it does, it will come quickly. Until next time, as always, work hard, work safe and enjoy life.
For more John Schmitt columns, visit www.thedriller.com/schmitt.