Boring or penetrating the earth – Processes – Boring with specific fluid
Reexamination Certificate
2000-06-26
2001-03-27
Tsay, Frank (Department: 3672)
Boring or penetrating the earth
Processes
Boring with specific fluid
C175S172000, C175S100000
Reexamination Certificate
active
06206112
ABSTRACT:
This invention pertains generally to the drilling of boreholes in the earth and, more particularly, to apparatus and a method of drilling by the use of hydraulic jets.
For many years, oil and gas wells have been drilled by a rotary bit mounted on a tubular drill string which extends down the borehole from the surface of the earth. The drill string is rotated at the surface, and the rotary motion is transmitted by the string to the bit at the bottom of the hole. A liquid commonly known as drilling mud is introduced through the drill string to carry cuttings produced by the bit to the surface through the annular space between the drill string and the wall of the borehole. This method of drilling has certain limitations and disadvantages. The string must be relatively heavy in order to transmit torque to the bit at the bottom of the hole. In hard rock, the drilling rate is slow, and the bit tends to wear rapidly. When the bit must be replaced or changed, the entire string must be pulled out of the hole and broken down into tubing joints as it is removed. It is necessary to use heavy, powerful machinery to handle the relatively heavy drill string. It is also necessary to install a casing in the well as it is drilled. The string is relatively inflexible and difficult to negotiate around bends, and frictional contact between the string and the well casing or bore can produce wear as well as interfering with the rotation of the drill bit. Powerful equipment is also required in order to inject the drilling mud with sufficient pressure to remove cuttings from the bottom of the well.
More recently, wells and other boreholes have been drilled with high velocity streams or jets of fluid directed against the material to be cut. Examples of this technique are found in U.S. Pat. Nos. 4,431,069, 4,497,381, 4,501,337 and 4,527,639. In U.S. Pat. Nos. 4,431,069 and 4,501,337, the cutting jets are discharged from the distal end of a hollow pipe positioned within an eversible tube having a rollover area which is driven forward by pressurized fluid. U.S. Pat. Nos. 4,497,381 and 4,527,639 disclose hydraulic jet drill heads attached to drilling tubes which are driven forward by hydraulic pressure, with means for bending the tube to change the direction of drilling, e.g. from horizontal to vertical.
U.S. Pat. Nos. 4,787,465, 4,790,394 and 4,852,668 disclose hydraulic drilling apparatus in which pressurized drilling fluid is discharged through a nozzle as a high velocity cutting jet in the form of a thin conical shell. The direction of the borehole is controlled by controlling the discharge of the drilling fluid, either in side jets directed radially from the distal end portion of the drill string which carries the drill head or in a plurality of forwardly facing cutting jets aimed ahead of the drill string so as to modify the geometry of the hole being cut. Other drill heads in which steering is effected by controlled discharge of the drilling fluid through jets of different orientations are disclosed in U.S. Pat. Nos. 4,930,586 and 4,991,667.
U.S. Pat. Nos. 4,787,465, 4,790,394 and 4,852,668 also disclose a seal arrangement which permits a hydraulic drill head to be removed or withdrawn from a drill string without removing the string from the borehole, and U.S. Pat. No. 5,255,750 discloses a system and method for controlling the rate of advancement or penetration of a hydraulic drill head.
Recent expansion of offshore drilling has created a shortage of offshore drilling rigs, with increasing costs and delays in the drilling of such wells. In the past two years, for example, the daily rate charges for offshore drilling ships have doubled or tripled, and the only way to reduce drilling costs significantly is to decrease the time required to drill the wells.
It is in general an object of the invention to provide a new and improved hydraulic drilling apparatus and method.
Another object of the invention is to provide a drilling apparatus and method of the above character which are particularly suitable for use in the drilling of offshore wells and other wells.
Another object of the invention is to provide a drilling apparatus and method of the above character which reduce the time and cost of drilling offshore wells.
These and other objects are achieved in accordance with the invention by providing a hydraulic drilling apparatus and method in which a hole is formed with a series of drill heads and strings of successively smaller diameter. After each section of the hole is formed, the drill head is withdrawn back through the string, leaving the string in place in the hole to serve as a casing for the well. The next smaller size drill head and string are then introduced through the strings which have already been placed, and the process is repeated until the hole has reached the desired length. The course of the hole can be changed, e.g. from vertical to horizontal, without interruption of the drilling process by selective application of the drilling fluid to the nozzles in the drill head to steer the advancing string.
Multiple laterals are formed by introducing a module having a plurality of extensible drilling tubes with drill heads at the distal ends thereof into the string and applying the pressurized drilling fluid to the module to advance the tubes from the string. The direction of the holes formed with the tubes is controlled by inclining the drill heads at oblique angles relative to the axes of the tubes. Once the laterals have been drilled, the module is withdrawn from the string, and the drilling tubes can either be withdrawn with the module or they can be cut off and left in the well.
In one disclosed embodiment, the drill heads which form the laterals have a generally hemispherical nose with a plurality of vortex generators or nozzles distributed thereover. In another, the drill heads have a hemispherical button projecting from a forwardly facing planar surface, with forwardly directed nozzle openings toward the front of the button and laterally directed nozzle openings in the base of the button near the planar surface.
REFERENCES:
patent: 4527639 (1985-07-01), Dickinson et al.
patent: 4763734 (1988-08-01), Dickinson et al.
patent: 4790394 (1988-12-01), Dickinson et al.
patent: 4856600 (1989-08-01), Baker et al.
patent: 5199512 (1993-04-01), Curlett
patent: 5373906 (1994-12-01), Braddick
patent: 5597046 (1997-01-01), Fisk
Dickinson Robert Wayne
Dickinson, III Ben Wade Oakes
Nordlund Robert
Flehr Hohbach Test Albritton & Herbert LLP
Petrolphysics Partners LP
Tsay Frank
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