Water source required

Water source required

Generally, a 250 GPM water source is required to drill a well with reverse rotary method. This will vary with the ability of the formation. Very porous formations will readily take excessive amounts of water. In such formations, it may be necessary to add drilling mud to the hole while drilling in order to seal the well bore and prevent loss of circulation of the drilling water.

In many cases, natural clay formations will assist in sealing off such troublesome areas. The water source is one of the most important factors in drilling with reverse rotary equipment. It must be of sufficient capacity to handle both normal requirements and emergencies. It is beneficial to have municipal water available or a nearby well of sufficient capacity.

In some cases, it is necessary to install a water supply prior to starting construction of the permanent well. When a test well is required, it can be equipped with a proper sized pump to supply the rig. A test hole or test boring may be completed as a well and equipped if necessary.

Occasionally, the pit's subsurface material is not capable of holding water. When this happens, the pit can be sealed with clay or plastic. Sometimes a pit dug into the ground is not permitted. In such cases a shallow pit is constructed by putting up low walls of wood planking or soil, or both, and laying plastic sheeting over the structure. Upon completion of well construction this pit must be totally removed including drill cuttings and the area left clean.

In some cases it is necessary to elevate the pit and the rig. The reverse rotary method drills open hole to the bottom. The only thing that prevents the hole from collapsing is an additional head of water above the natural static water level. Usually an additional six feet to 10 feet of water added above static in the hole will accomplish this.

The weight of this additional water, regardless of the hole diameter, is the key to holding open the drilled, uncased hole. In order to maintain this head, and in order to be able to operate the equipment, the surface casing must extend to at least this much above static water level. If static is two feet below grade, the drilling surface will be plus six to plus eight feet above grade.

Should a natural plus head condition be known to exist either at surface or when a lower formation is penetrated, the rig and pit build-up must be high enough to overcome this before drilling can start. It is thus necessary to elevate both by hauling in material to mound up for a pit and as a berm for the rig. The pit, in this case, must be water tight and the berm compacted to support the rig in a constant level condition.

The surface casing must be inserted below natural grade to a depth that will insure positively against leakage and undermining of the superstructure. With the rig and pit elevated, ramps and elevated areas are required for access, work room and materials storage. Needless to say, this type of set up can be expensive in time and material costs.

As mentioned earlier, sufficient water must be available to maintain the level of the pit and to keep a head on the well. There are many ways of assuring that the water level remains constant. Some are complicated and practically fool-proof, while others are quite simple.

When working around the clock, a simple gate valve is all that is necessary to control the flow of water into the pit from the outside source. Once drilling is underway and normal conditions prevail, 50 gpm should be enough. With crews working around the clock, someone is available to adjust the valve as necessary.

Should the job be stopped while the hole is still uncased, it is necessary to keep a 24-hour watch on the water level or install an automatic float system that will adjust the water flow itself. The watch is generally the surest method. The automatic system can be affected by icing conditions which negate its operation or can be upset by vandals.

It is expensive to man equipment around the clock, but it is much more costly to lose a hole and damage equipment by not maintaining the proper water level.