Direct circulation drilling involves using a hand or engine powered / hydraulic drill rig to turn a bit in the earth to drill a borehole. The drill pumps water or drilling mud through the drill stem to remove the cuttings from the borehole. In the process, a pump sucks water from a mud pit and pumps the water through a drill stem, down the borehole, through the bit and back up the borehole where it deposits the cuttings in the mud pit. The system depends on the pressure of the mud pump to remove the cuttings from the borehole.
Direct circulation drills cannot drill large diameter holes or remove large rocks or gravel from the borehole because the velocity of water or mud moving up the borehole decreases by the square of the diameter of the borehole. When attempts are made to increase the ability of the drill to remove cuttings the processes used damage the borehole either by causing the addition of drilling mud to be required, fracturing the formation, leaving mud and debris in the bore or by a failure to advance the borehole. In some areas as many as 50 percent of a boreholes drilled fail within a few years. Many of those failures are due to using the direct circulation method to drill the well.
Direct circulation drilling will drill a low or good quality well in most instances. In ideal situations, the direct circulation drill will drill an acceptable well. In no circumstance usually encountered will direct circulation drilling produce a better quality well than reverse circulation. The reason this is true is because direct circulation drills produce a high pressure at the bottom of the drill stem that forces drill debris and drilling mud into the aquifer. In addition, a direct circulation drill may not be capable of removing clay, gravel or stones from the bottom of the borehole that are easily removed by a reverse flow drill. Those clay,stones and gravel can stop drilling altogether. Sometimes that means that an owner will pay for a well that cannot reach a proper depth to produce sufficient water. Â In order to effectively remove cuttings from a borehole, it is generally accepted, that a velocity greater than 80 to 100 feet per minute up the annulus of the borehole be maintained. Because all direct circulation drills are limited as to the size of borehole by the output capacity of their mud pump, all direct circulation drills have a maximum diameter bore they can drill. If due to caving or using the wrong size bit, that diameter is exceeded, damage will occur to the borehole. There are driller's tricks that will allow larger diameters to be drilled, but those tricks produce a lower quality well. Drillers tricks will not overcome the fact that large gravel cannot be removed and that debris and mud will be injected in the aquifer.
Reverse Circulation drilling is the opposite of Direct circulation drilling. In Reverse Circulation Drilling the drill fluid goes down the annulus of the borehole and up the interior of the drill stem and is then discharged into the mud pit. This movement of the drilling water occurs in an air lift reverse flow drill by injecting air into the area just above the drill bit and within the drill stem. The air is delivered either from a tube within or outside the drill stem.
The air discharged within the drill stem mixes with the water within the drill stem as it is submerged within the borehole. When the air mixes with the water, then a unit of air and water mixed together within the drill stem weighs less than water without air mixed that is in the annulus outside the drill stem. Because the air and water mixture weighs less, it is pushed up the drill stem by water flowing into the drill stem past the drill bit. The water that enters is then mixed with more air and that water and air mixture is then lighter and moves up the drill stem. This sets up a circulation where water travels up the drill stem and down the borehole. This process continues as long as compressed air is supplied to the interior of the drill stem. The moving water at the bit sucks up the cuttings from the bit and carries them up the drill stem at a very high velocity. The circulation of drill water discharges into the mud pit where the debris settles out and the drill water then travels back down the annulus of the borehole. This process continues until the well is complete.
It is important to note that all our powered reverse circulation drills will not only drill in reverse circulation mode, they also are capable of drilling with an add on direct circulation kit.
This patented reverse flow air lift drill and system have resolved most of the problems associated with air lift reverse flow drilling. For example there is no longer a price issue, or design issue, or simplicity issue. Cost is no longer an issue. And most other issues are resolved as well. However, because this patented system will drill where direct circulation drills will not drill, there are some issues. Because direct circulation stops up the aquifer, it requires less drill water. In fact, because this drill will drill large gravel that is highly porous, it can require large quantities of drill water. But that means that the well in that porous zone will produce more water, water that would not be recovered by a direct circulation drill. This drill also requires an air compressor. However the cost of the air compressor is offset by the fact that a mud pump is not required. This drill requires a starter hole at least 3 ft. deep. But that is a minor cost offset by the fact that only a single mud pit is required. This drill also creates more water and mud at the drill site, but that is because it produces a greater circulation velocity that brings large rocks from the excavation. So while there are problems, those problems are offset by the fact that this drill is more efficient and will drill where other drilling systems fail.
The basics of reverse flow drilling and direct circulation drilling are very similar. For that reason direct and reverse circulation rigs have the same mast, rotary, power and hydraulic system requirements. Basically a reverse circulation drill system can do everything a direct circulation system can do if modified properly. Plus it can drill reverse flow wells. The opposite is not true when compared to the patented system I use for reverse circulation drilling. Because this system is patented, it cannot be sold or used by others. Because the new patented system has major refinements, even if a direct circulation rig is modified with an old style reverse flow system it cannot work as inexpensively or efficiently as this new system. While this newly patented system can be used for direct circulation drilling and do everything other drills can do, other drills cannot be modified to do what this drill can do.
We can build this newly patented drill to meet any normal drilling requirement you may have. We can ship your drill with options for direct circulation, auger drilling, top head drive, Kelly drive, steel drill stem, plastic drill stem or down the hole hammer. This is the only drill system that is fully adaptable to your drill needs.
I have been building drilling rigs since I was 14 years old and helped my dad build his first Kelly bar drill. I have built multiple drilling rigs that mount on trucks, trailers and cranes. In fact I hold a U.S. patent on another reverse flow drill I designed, patented and used in the 1980's.
I am prepared to build you the best reverse flow air lift drill on the market. That drill can be crane mounted, truck mounted, trailer mounted, mounted on a 4 wheeler or any other platform.
I have available hand operated drills that I currently have in operation in India, Africa, the U.S. and Mexico. So if you are doing charity work in a third world country, order hand drilling equipment or an oxcart mounted drill and train the locals in your country of choice.
We currently have a 4 week lead time for a trailer mount drill and an even shorter lead time for export hand drilling equipment.