Rotary Drilling

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 pilot boreholes for guiding larger shaft borings. Rotary drilling techniques are used to drill boreholes for water, oil, gas, and other fluid pipelines that need to pass under rivers, highways, and other natural and man-made obstructions. Most recently, rotary drilling is being used to drill boreholes for fiber optics and other telecommunication lines in obstacle ridden areas such as cites and industrial sites. The most sophisticated application for rotary drilling is the drilling of deep boreholes for the recovery of natural resources such as crude oil, natural gas, and geothermal steam and water. Drilling boreholes for fluid resource recovery requires boreholes drilled to depths of 3,000 ft to as much as 20,000 ft.

Rotary drilling is highly versatile. The rotary drilling applications given above require the drilling of igneous, metamorphic, and sedimentary rock. However, the deep drilling of boreholes for the recovery of crude oil and natural gas are almost exclusively carried out in sedimentary rock. Boreholes for the recovery of geothermal steam and water are constructed in all three rock types. The rotary drilling method requires the use of a rock cutting or crushing drill bit. Figure 1-1 shows a typical mill tooth tri-cone roller cone bit. This type of drill bit uses more of a crushing action to advance the bit in the rock (see Chapter 3 for more details). This type of bit is used primarily in the drilling of sedimentary rock.

Figure 1-1: Mill tooth 7 7/8 inch tri-cone roller cutter bit 1ADC Code 126 (courtesy of Reed Rock Bit Company).

To advance the drill bit in rock requires the application of an axial force on the bit (to push the bit into the rock face), torque on the bit (to rotate the bit against the resistance of the rock face), and circulating fluid to clear the rock cuttings away from the bit as the bit generates more cuttings with its advance (see Figure 1-2).

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Figure 1-2: The three necessary components for rotary drilling.

Rotary drilling is carried out with a variety of drilling rigs. These can be small "single" rigs, or larger "double" and "triple" rigs. Today most of the land rotary drilling rigs are mobile units with folding masts. A single drilling rig has a vertical space in its mast for only one joint of drill pipe. A double drilling rig has a vertical space in its mast for two joints of drill pipe and a triple drilling rig space for three joints. Table 1-1 gives the API length ranges for drill collars and drill pipe [6].

Table 1-1: API length ranges for drill collars and drill pipe.

Ranges

Minimum Length (ft)

Maximum Length (ft)

Range 1

18

22

Range 2

27

30

Range 3

38

45

Figure 1-3 shows a typical single drilling rig. Such small drilling rigs are highly mobile and are used principally to drill shallow (less than 3,000 ft in depth) water wells, environmental monitoring wells, mining related boreholes, and other geotechnical boreholes. These single rigs are usually self-propelled. The self-propelled drilling rig in Figure 1-3 is a George E. Failing Company Star 30K. These rigs typically use Range 1 drill collars and drill pipe.

Figure 1-3 shows a typical single drilling rig. Such small drilling rigs are highly mobile and are used principally to drill shallow (less than 3,000 ft in depth) water wells, environmental monitoring wells, mining related boreholes, and other geotechnical boreholes. These single rigs are usually self-propelled. The self-propelled drilling rig in Figure 1-3 is a George E. Failing Company Star 30K. These rigs typically use Range 1 drill collars and drill pipe.

Failing Drilling

Figure 1-3: Typical self-propelled single drilling rig (courtesy of George E. Failing Company).

Single rigs can be fitted with either an on-board air compressor, or an on-board mud pump. Some of these rigs can accommodate both subsystems. These rigs have either a dedicated prime mover on the rig deck, or have a power-take-off system which allows utilization of the truck motor as a prime mover for the drilling rig equipment (when the truck is stationary). These small drilling rigs provide axial force to the drill bit through the drill string via a chain or cable actuated pull-down system, or hydraulic pull-down system. A pull-down system transfers a portion of the weight of the rig to the top of the drill string and then to the drill bit. The torque and rotation at the top of the drill string is provided by a hydraulic tophead drive (similar to power swivel systems used on larger drilling rigs) which is moved up and down the mast (on a track) by the chain drive pull-down system. Many of these small single drilling rigs are capable of drilling with their masts at a 45° angle to the vertical. The prime mover for these rigs is usually diesel fueled.

Figure 1-4 shows a typical double drilling rig. Such drilling rigs are also mobile and can be self-propelled or trailer mounted. Figure 1-5 shows the schematic of a self-propelled double drilling rig.

Ss40 Drilling Rig
Figure 1-4: Typical trailer mounted drilling rig (courtesy of George E. Failing Company).

The trailer mounted drilling rig in Figure 1-4 is a George E. Failing Company SS-40. These double rigs have the capability to drill to depths of approximately 10,000 ft and are used for oil and gas drilling operations, geothermal drilling operations, deep mining and geotechnical drilling operations, and water wells. Double rigs typically use Range 2 drill collars or drill pipe. These rigs are fitted with an on-board prime mover which operates the rotary table, drawworks, and mud pump. The axial force on the drill bit is provided by drill collars. The torque and rotation at the top of the drill string is provided by the kelly and the rotary table. The double drilling rigs have a "crows nest" or "derrick board" nearly midway up the mast. This allows these rigs to pull stands of two drill collar joints or two drill pipe joints. These rigs can carry out drilling operations using drilling mud (with the on-board mud pump) or using compressed air or gas drilling fluids (with external compressors). A few of these drilling rigs are capable of drilling with their masts at a 45° angle to the vertical. The prime mover for these rigs is usually diesel fueled, but can easily be converted to propane or natural gas fuels.

Triple drilling rigs are available in a variety of configurations. Nearly all of these drilling rigs are assembled and erected from premanufactured sections. The vertical tower structure on these drilling rigs are called derricks. The smaller triple land rigs can drill to approximately 20,000 ft and utilize Range 2 drill collars and drill pipe. Very large triple drilling rigs are used on offshore platforms. These rigs can utilize Range 3 drill collars and drill pipe.

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BLOCK

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Figure 1-5: Typical self-propelled double drilling rig schematic layout.

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Figure 1-5: Typical self-propelled double drilling rig schematic layout.

The schematic layout in Figure 1-5 shows a typical self-propelled double drilling rig. This example rig is fitted with a mud pump for circulating drilling mud. There is a vehicle engine that is used to propel the rig over the road. The same engine is used in a power-take-off mode to provide power to the rotary table, drawworks, and mud pump. For this rig, this power-take-off engine operates a hydraulic pump which provides fluid to hydraulic motors to operate the rotary table, drawworks, and mud pump. The "crows nest" on the mast indicates that the rig is capable of drilling with a stand of two joints of drill pipe. This drilling rig utilizes a rotary table and a kelly to provide torque to the top of the drill string. The axial force on the bit is provided by the weight of the drill collars at the bottom of the drill string (there is no chain pull-down capability for this drilling rig). This example schematic shows a rig with on-board equipment that can provide only drilling mud or treated water as a circulate fluid. The small air compressor at the front of the rig deck is to operate the pneumatic controls of the rig. However, this rig can easily be fitted for air and gas drilling operations. This type of drilling rig (already fitted with a mud pump), would require an auxiliary hook up to external air compressor(s) to carry out an air drilling operation. Such compressor systems and associated equipment for air drilling operations are usually provided by a subcontractor specializing in these operations.

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Responses

  • Cino
    What is offshore mast drilling?
    9 years ago
  • HYIAB
    Does rotary drilling pull collars?
    9 years ago
  • elliott millar
    How to recover Rotary Drilling shaft?
    9 years ago
  • sara
    How deep can a ss 40 drill?
    9 years ago
  • Dominik Frankfurter
    How to drill 3000ft borehole sand?
    8 years ago
  • justin
    What is the crow's nest on a drill rig?
    5 years ago
  • J
    How deep do you go for oil and how is the drilling done with air or mud rotary?
    1 month ago

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