Boring or penetrating the earth – Bit or bit element – Rolling cutter bit or rolling cutter bit element
Utility Patent
1999-04-01
2001-01-02
Neuder, William (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Rolling cutter bit or rolling cutter bit element
C175S336000, C175S376000
Utility Patent
active
06167975
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
It is commonplace to drill wells today with tricone drill bits. Tricone drill bits represent the industry standard and have done so since their advent about 75 years ago. The tricone drill bit has a number of advantages, and these advantages have prompted the domination of the business with tricone drill bits. To be sure, single cone drill bits existed many years ago and were somewhat common drill bits prior to the advent of the tricone drill bit. This disclosure, however, is directed to a single cone rotary drill bit which is especially useful in a number of circumstances today. With a tricone drill bit, a large diameter hole can be drilled. To mount all three of the cones and to make arrangements for the balanced support of the three cones and to provide relatively symmetrical loading on the threaded drill bit as it connects with the drill collar thereabove, the tricone drill bit, when drilling a large diameter hole, has many advantages. It is not uncommon, however, to drill extremely deep wells where the wells do have reductions in diameter.
Reductions in diameter from the surface can be achieved with tricone drill bits in a limited measure. Very large drill bits are used to form the first few hundred feet of a hole, and then the next step involves a large tricone drill bit, and then the next step involves a smaller tricone drill bit. Eventually, it is desirable to reduce the diameter of the hole even further. When a drill bit is reduced in diameter, typically below about six inches in diameter, certain size dictating limitations come into play, thereby reducing the life of the tricone drill bit. Such wells (sometimes known as a slim hole) are often now drilled with a mud motor. Even when drilled with the rotary equipment at the well head rather than a mud motor, there is a common limitation which relates to the bearings. In general terms, because of crowding in a small tricone drill bit, the three cones are supported on bearing assemblies which are relatively small. Because they are so small, bearing life is shortened. A tricone drill bit of large diameter equipped with large diameter bearings will last much longer. One advantage of the single cone drill bit in this disclosure is that a very large diameter bearing is installed even though the drilled hole is relatively small, and relative bearing speed is also reduced, extending the life of the bearing assembly.
Every drill bit has an estimated life. Sometimes, the driller can just place his hand on the rig floor equipment and guess by the surface located vibration or chatter whether or not the bearings in the drill bit are failing, and hence initiate a trip to remove the drill bit, replace the drill bit, and reenter the well. This is an experience factor which is commonly encountered with the tricone drill bit. It has a notable way of chattering or forming a constant repetitious noise and vibration signal at the surface sensed by skilled and experienced personnel. In part, this results from the fact that one bearing assembly on one cone will fail first and yet the bit will continue to operate, limping along with more vibration. Since that can be detected at the surface, another trip is initiated to replace that drill bit. The smaller the bits the more difficult it is to recognize symptoms of failure. The good news in a slim hole single cone bit is that it has a very large bearing and the simple cone rotates much slower than a cone on a similar size tricone bit rotating at the same RPM. When it runs slower, the velocity inflicted on the bearing assembly is slower. When that occurs, the single cone drill bit will simply last longer. The single cone drill bit of this disclosure can last longer even when driven by mud motor. Typically, a rotary table turns somewhere between 60 and 120 rpm. Where a mud motor is used, the mud motor will rotate the drill bit at perhaps 200 rpm. Even 300 rpm is sometimes achieved. As the speed is picked up, bearing failure occurs sooner.
Bit life has been extending by the drill bit of the present disclosure. It operates longer and it will operate at a greater rpm. This is because of the installation of a much larger and stronger bearing assembly in the single cone drill bit and the fact that the cone in this bit rotates slower than the three cones in a tricone drill. With a single large bearing assembly, life is measurably extended.
One aspect of the present disclosure is the incorporation of a sealed, pressure compensated journal bearing mounted on a journal having a journal angle of less than about 45°. The journal supports a cone which in turn is equipped with an appropriate cutting structure. The preferred form is a set of tungsten carbide (WC) inserts. These inserts are known below as TCI. The single cone has a novel set of fluid channel grooves on the cone aligning with the jet nozzles. The single cone has a nose area with a circular groove which improves cutting face flushing.
SUMMARY OF THE INVENTION
It is the object of this invention to provide an improved one cone rotary TCI rock bit having enhanced performance due to better cuttings removal. This invention provides a radial groove on the nose end of the cone which connects three spiraling axial grooves. This novel series of connected grooves provides a more efficient flow path for fluid directed to the hole bottom. Less resistance on the return path allows the fluid to circulate faster under the bit and remove the cuttings faster. It is important to remove cuttings quickly to prevent re-grinding the cuttings. In some formations, better removal of the cuttings will also help prevent bit balling. The single cone has a set of nose located bearing inserts.
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patent: 4790397 (1988-12-01), Kaalstad et al.
patent: 4832143 (1989-05-01), Kaalstad et al.
patent: 4936398 (1990-06-01), Auty et al.
Felsman Bradley Vaden Gunter & Dillon, LLP
Neuder William
Rock Bit International, Inc.
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