Reverse circulation equipment

Reverse circulation equipment

The equipment consists of a rotary table, an engine to run the rotary table, plus an engine to handle the pump. In some instances a single engine can be installed to handle both the pump and rotary table. Gasoline or diesel power is determined by preference of the drilling contractor.

A pump with enough capability and stamina is necessary to handle 500 gpm and drill cuttings including stones up to six inches in diameter. It is normally a centrifugal suction pump. The mast is raised hydraulically and is constructed to handle maximum weights of drill rod and well casing based on diameter and depth rating of the rig.

Generally the rig is trailer mounted due to mechanical equipment space requirements. (Reverse rotary rigs for shallow, small diameter wells can be made up on truck mountings.) Usually a reverse rotary rig is operated around the clock until the well has reached a point of construction where no chance of collapse can occur. In order to operate on a 24-hour basis a generator is necessary and can be mounted on the rig for lights and hand tools.

Drill rod used may be in any diameter from three to eight inch and in any length from 10 to 30 feet. Again, requirements of the type of work to be done determine this factor along with general rig size. Most drill rods are flanged while some are threaded, (similar to mud rotary rod), with full hole diameter maintained at the joint.

Air compressors are a help when drilling deep holes. This equipment, coupled to an air line set inside of, or to enter, the drill rod at about 250 feet below drilling grade, will permit the operator to obtain greater depths with more ease by reducing the pressure inside the drill rod. This eases the strain on the pump in lifting the drill cuttings to the surface and discharging them into a pit.

The bits will vary with the type of material drilled. All have open bottoms to permit entry of the drill cuttings. Some bits are mounted on an eccentric and roll on a ball bearing race while penetrating. Others are true vertical and are equipped with horizontal blades used to cut the material as they scrape through the formation.

Combination pilot and drill bits are also used to guide the hole progress. These are made up of graduated diameters until the desired hole diameter is reached. They are mounted one immediately on top of the other and look like an upside down Christmas tree. Some bits are equipped with rock rollers similar to conventional rotary rock bits. These are used in place of the blades on the drag bits in hard packed materials. In many cases the hard pack material will snap the blades of the drag bit causing an undersized hole, loss of time in repairs, and once in a while a prolonged fishing job.

Some necessary equipment to accompany the rig, assuming it is trailer mounted, is a tractor to pull the rig, a truck or tractor and trailer to carry drill rod, proper diameter surface casing to prevent the grade surface from sloughing in, flow casing to feed water through the surface casing, setting timbers, leveling jacks, additional gasoline/diesel fuel tanks (or delivery arrangements), crew and tool shanty, bits, and flood lights.

In addition, a bulldozer is required to dig the pit to hold the drill cuttings and drilling water. There is need for space for a trailer to hold the gravel pack material and a place close to the rig to store the well casing and screen.

Since this method of drilling is fast, and well construction completion can occur at any hour during a 24-hour period, it is necessary to have as much of the final material and accessory equipment as possible present on the site at the start of operations.

Wells of this type can be drilled from a minimum of 10 inch hole diameter to a maximum of 60 inches or more under normal drilling requirements. Depths can vary from 40 feet to over 1500 feet.