Water Well Ebooks Catalog
Reverse circulation techniques are not restricted to air drilling operations. Reverse circulation techniques often use standard drill string like that shown in Figure 3-1. In the past two decades there has been a dramatic increase in the use of air drilling reverse circulation techniques for drilling water wells, monitoring wells, geotechnical boreholes, and other shallow (i.e., less than 3,000 ft) wells. The increased use of reverse circulation techniques has been encouraged by the development of new technologies. One of these innovations is the development of dual wall drill pipe.
Water additive concentrations can be adjusted by setting the mixing pump to run at the appropriate rate. A minimum rig water supply pressure of 25 psi is typically required for the correct operation of the mixing system and to provide a fluid supply at least equal to the rate at which mix fluid is drawn from the tank by the high pressure pumps.
Applications that required penetration of the ground included mining for resources, digging water wells, burying objects, supporting columns and structures and searching for food (including plant bulbs and roots). Advances in penetration tools were made as a result of discovering more effective fabrication materials, developing methods of processing and machining, increasing the capability to leverage forces and driving tools with the aid of mechanical, electrical, pneumatic and hydraulic actuators.
Some subsea wellhead designs require a separate trip to run and pull the annulus pack off. On a deep water well with perhaps a 7 inch tieback, this can result in considerable extra rig time, particularly if an abandonment is likely. It may be more cost-effective in these cases to run a system where the lock down rings can be removed and the pack off and hanger run simultaneously.
Drilling is a very old technique, for water supply and for exploitation of mineral resources. Water wells have been drilled in Egypt more than three millenia ago. Fig. 1 shows an example of a quite sophisticated, hand-operated drill rig used in China to drill several hundred meter deep in a few month.
Schlumberger is committed to meeting the demands of the future. A deepwater center of excellence has been established to identify and develop cost effective, solutions to deep-water challenges. The center is focused on integrated solutions encompassing all aspects from the planning to completion of deep-water wells around the world.
Drilling fluid was used in the mid-1800s in cable tool (percussion) drilling to suspend the cuttings until bailed from the drilled hole.1 With the advent of rotary drilling in the water well-drilling industry, drilling fluid was well understood to cool the drill bit and to suspend drilled cuttings for removal from the wellbore. Clays were being added to the drilling fluid by the 1890s and by the time Spindletop was discovered in 1901, it was considered necessary to have suspended solids (clays) in the drilling fluid to support the walls of the borehole. These solids (clays) resulted from the disaggregation2 of formations penetrated by the drill bit.2 If the penetrated formations failed to yield sufficient clay in the drilling process, clay was mined on the surface from a nearby source and added to the drilling fluid. These were native muds created either by mud making formations or, as mentioned, by adding specific materials from a surface source.
The methods for drilling and data collection vary between countries, but are basically the same as those used for other exploration purposes, like in water well industry, foundation drilling and in the mining industry. The importance of geological exploration for shallow geothermal applications is discussed by Andersson et al. (1997).
The method of reverse-circulation drilling was designed primarily for drilling large-diameter production wells in unconsolidated formations. The practical minimum diameter (about 16 in.) for drilling holes by the reverse-circulation method almost precludes its being used for test-hole drilling. However, this method provides the best cuttings samples of any drilling method because of the large intake capacity of the bit (5 in. or more) this method also provides fast delivery of cuttings to the surface because of high ascending velocities (can be several hundred feet per minute) of the drill cuttings and fluid. Therefore, reverse circulation is an excellent drilling method for obtaining cutting samples. Ibr those readers interested in the method, comprehensive descriptions are provided in Water Well Techology (Campbell and Lehr, 1973) and Ground Water and Wells (Universal Oil Products, 1966).
The rotary drilling method is comparatively new, having first been practiced by Leschot, a French civil engineer, in 1863. United States patents on rotary equipment were issued as early as 1866 but, as was the case with cable tools, the early application was for water well drilling. It was not until approximately 1900 that two water well drilling contractors, M. C. and C. E. Baker, moved their rotary equipment from South Dakota to Corsicana, Texas where it found use in the soft rock drilling of that area.1 In Texas in 1901 Captain Lucas drilled the Spindletop discovery well with rotary tools. This spectacular discovery is credited with initiating both the Southwest's oil industry and the widespread use of the rotary method. The inherent advantages of this method in the soft rock areas of Texas and California insured its acceptance, and it was in general use by the early 1920's. It is interesting to note that in the 1914-18 period, cable tools drilled 90 of all U.S. wells. At the...
Water-well drilling industry, drilling fluid was well understood to cool the drill bit and to suspend drilled cuttings for removal from the well bore. Clays were being added to the drilling fluid by the 1890s. At the time that Spindletop, near Beaumont, Texas, was discovered in 1901, suspended solids (clay) in the drilling fluid were considered necessary to support the walls of the borehole. With the advent of rotary drilling at Spindletop, cuttings needed to be brought to the surface by the circulating fluid. Water was insufficient, so mud from mud puddles, spiked with some hay, was circulated downhole to bring rock cuttings to the surface. Most of the solids in the circulating system (predominantly clays) resulted from the so-called disaggregation of formations penetrated by the drill bit. The term disaggregation was used to describe what happened to the drilled clays. Clays would cause the circulating fluid to thicken, thus increasing the viscosity of the fluid. Some of the...
DURATHERM is a high-temperature mud system sold by M-I Drilling Fluids. This mud system uses small concentrations of bentonite for suspension. XP-20, a modified chrome lignite containing potassium, is used as a fluid loss additive and viscosity stabilizer. XP-20 is used primarily in fresh water systems. MELANEX-T, a melanin polymer derivative, is used as a high-temperature deflocculant to reduce viscosity and high-temperature gelation. RESINEX, a resin polymer, is used for HTHP filtration control and can be used to replace the XP-20 in salty environments.
The drilling fluid used for air-rotary coring is aii but it occasionally has additives, such as water, foam, polymers, and bentonite gels injected to (1) cut down airborne dust and prevent sediment balling (2) aid in removal of cuttings at lower air velocity, as well as removal of water in saturated zones, and (3) seal off lost circulation zones. For a more detailed description of these additives and how they are used, see Water Well Technology (Campbell and Lehi 1973, p. 121-125) and commercial catalogs from most drilling-additive supply companies. The velocity and volume of air required to lift cuttings out of the hole are variables that are related to the specific gravity of the particles and to the volume of the annulus formed between the drill pipe and borehole wall. Generally, an average uphole air velocity of 3,000 ft min is required for drilling materials to remove drilled cuttings having an average specific gravity of 2.6 from the borehole. Also required is some amount of...
Figure 1-11 shows a schematic of the various drilling fluids and their respective potential for avoiding formation damage. Formation damage is an important issue in fluid resource recovery (e.g., water well, environmental monitoring, well drilling operations, oil and natural gas, and geothermal fluids). The lighter the fluid column in the annulus (with entrained rock cuttings), the lower the potential for formation damage (arrow points upward to increasing avoidance of formation damage). Formation damage occurs when the fluid column pressure at the bottom of borehole is higher than the pore pressure of the resource fluid (oil, gas, or water) in the rock formations. This higher bottomhole pressure forces the drilling fluid (with entrained rock cutting fines) into the exposed fractures and pore passages in the drilled rock formations. These fines plug these features in the immediate region around the borehole. This damage is called a skin effect . This skin effect damage restricts
Percussion air hammers have been used for decades in shallow air drilling operations. These shallow operations have been directed at the drilling of water wells, monitoring wells, geotechnical boreholes, and mining boreholes. In the past decade, however, the percussion air hammers have seen increasing use in drilling deep oil and natural gas wells. Percussion air hammers have a distinct advantage over roller cutter bits in drilling abrasive, hard rock formations.
Dual wall drill pipe elements are used exclusively in reverse circulation drilling operations. This type of drill pipe is used for drilling shallow ( 3,000 ft or less) water wells, environmental monitoring wells, geotechnical boreholes, and mining boreholes. These rotary drilling operations can be a) rotation of the dual wall pipe drill string with a tri-cone or drag type bit, b) rotation of the dual wall pipe drill string with a standard downhole air hammer (with standard air hammer bit), or c) rotation of the dual wall pipe drill string with a reverse circulation downhole air hammer (with reverse circulation air hammer bit). These rotary drilling operations are carried out with hydraulic top drives (for single rotary drilling rigs) and with power swivels (for double and triple rotary drilling rigs).
Rotary drilling is a method used to drill deep boreholes in rock formations of the earth's crust. This method is comparatively new, having been first developed by a French civil engineer, Rudolf Leschot, in 1863 3 . The method was initially used to drill water wells using fresh water as the circulation fluid. Today this method is the only rock drilling technique used to drill deep boreholes (greater than 3,000 ft). It is not known when air compressors were first used for the drilling of water wells, but it is known that deep petroleum and natural gas wells were drilled utilizing portable air compressors in the 1920's 4 . Pipeline gas was used to drill a natural gas well in Texas in 1935 using reverse circulation techniques 5 . Today rotary drilling is used to drill a variety of boreholes. Most water wells and environmental monitoring wells drilled into bedrock are constructed using rotary drilling. In the mining industry rotary drilling is used to drill ore body test boreholes and...
Poly Kem EZT Liquid polymer and drilling fluid additive for use in HDD applications along with bentonite or as a substitute. Excellent for clear water drilling, for water well drilling, and exploration bores. Has excellent borehold stabilization properties and prevents clay from swelling Improves cutting transport in air foam injection. Specially modified for water-well drilling or wherever a minimum 220 bbl yield is required. Mixes rapidly for quick hydration and carries cuttings in mud with lower soil content. A phpa polymer viscosifier for addition to a bentonite system offering improved viscosity and lubrication qualities. Mud Up can be used as a viscosifier in a clear water system, is biodegradable or can be rapidly broken back
The third category of drilling is the down-the-hole (DTH) percussive hammer. Unlike the drifter drill, the hammering action passes through the drill string. The DTH hammering action takes place at the end of the bit only, with little loss of energy. These tools are unique in that the more air pressure they can hold, the faster they will cut. It does not require high rotational torque or much thrust, as with the rotary bit, to penetrate the rock. As the high-pressure air passes through the hammer with the button bit engaged in the face of the rock, the piston will hit the back of the bit, forcing the bit into the rock at a rate of 2000 blows per minute. The air then passes through the end of the bit, removing the rock cuttings through the bore hole back to atmospheric air pressure. This is called up-hole velocity and is measured in feet per minute. Down-the-hole percussive hammers are very cost-effective for drilling hard rock. They are used for water-well drilling, blast-hole...
De-dusters are usually required for any air or gas drilling operation. Figure 2-14 shows the location of the de-duster near the exit end of the blooey line. Figure 2-17 shows a typical de-duster design. The de-duster is a small diameter pipe (2 inch nominal diameter or smaller) water system located inside the blooey line. A pump supplies the system with water. The water is sprayed on the dry rock dust particles that exit the line. This reduces or eliminates the dust clouds that are typical of dry air or natural gas drilling operations.
On the surface, unconfined water moving from a high-potential to a low-potential zone simply flows downhill. In a municipal water system, however, water flows down from a high water tower, travels horizontally through a water main, and rises again into hilltop houses and the upper stories of high buildings. As long as its outlet is below the level of the water tower, water will flow uphill or down.
Polymer chains are extremely long when compared to clay particle dimensions. When high molecular weight (several million) polymer chains become linked with multitudes of clay particles in a water system, there is a combined effect that creates highly viscous, but shear-thinning, rheology.
If drilling foam or other gel additives are injected considerably lower air velocity and annular pressure are required to lift the cuttings from the hole. Ear a more detailed overview of the air-rotary drilling method, see Water Well Technology (Campbell and Lehr, 1973, p. 121-136).
Polymers are often used in drilling fluids to improve the properties of the bentonite. This improvement typically involves increasing the yield. The polymers reduce the amount of dry bentonite required to produce a given amount of drilling fluid. When used in drilling fluids, Wyoming bentonite yields in excess of 85 barrels per ton of material. The addition of polymers to produce high-yield bentonite can increase the yield to 200 barrels per ton of material. Polymers are long-chain molecules consisting of many simple molecules linked together. They offer a clay-free drilling fluid that is nontoxic. There are a variety of polymer types that are often used in water-well drilling. Polymers are added to achieve specific functions such as water swelling and gel strength.
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