Modular kerfing drill bit

Abstract

A modular kerfing rock drilling bit (10) is presented. Drill bit (10) comprises a bit body (12) having a connection (14) for attachment to a drill string member. A base portion (16) below the connection (14) has an outer portion (18) and a bottom (20). Slots (22) are formed in the base portion (16). A cutter assembly (100) comprises a leg (110) insertable into the slot (22) of the bit body (16). A journal (126) extends angularly downward and inward from the leg (110) for bearing support of a cone (180) rotatably mounted on the journal (126). A plurality of cutters (182) extend outward from the surface of the cone (180). A kerfing segment (140) extends downward from the leg (110) beyond the cone (180). A plurality of kerf cutters (142) are attached to the bottom of the kerfing segment (140).

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] None. BACKGROUND OF THE INVENTION [0002] 1. Technical Field [0003] The present invention relates generally to drilling bits used for drilling earth formations. More specifically, the present invention relates to a novel modular design for the improved construction of kerfing type rock bits, comprised of a combination of fixed cutters and roller cone cutters. [0004] 2. Description of Related Art [0005] In the exploration of oil, gas, and geothermal energy, drilling operations are used to create boreholes, or wells, in the earth. These operations normally employ rotary and percussion drilling techniques. In rotary drilling, the borehole is created by rotating a tubular drill string with a drill bit secured to its lower end. As the drill bit deepens the hole, tubular segments are added to the top of the drill string. While drilling, a drilling fluid is continually pumped into the drilling string from surface pumping equipment. The drilling ...

AI Technical Summary

Benefits of technology

[0016] The present invention is a significant improvement over that described in the above enumerated prior art patents. The improvements of the present invention relate to both the location and relationship between cutting elements, as well as to the design, construction and manufacture of the drill bit. A principal advantage of the present invention is that it provides a drill bit capable of drilling more efficiently than prior art designs

[0017] Another advantage of the present invention is that it provides a hybrid bit design that is modular, permitting reduced inventories of component parts for assembly of multiple configurations of drill bits. Another advantage of the present invention is that it provides a hybrid bit design that can be assembled quickly, making the finished product deliverable faster than prior art designs. Another advantage of the present invention is that it provides a hybrid drill bit design that incorporates larger component cutting elements and larger bearing and seal systems which is more durable and drills faster.

[0018] Another advantage of the present invention is that it provides a hybrid drill bit design having very large flow relief area between the kerfing segments, allowing the bit to perform at very high rates of penetration without cutting build-up and balling of the bit. Other advantages of the present invention will become apparent from the following descriptions, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

[0019] In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a modular kerfing drill bit is disclosed, having a bit body with a threaded connection for attachment to a drill string member at it's upper end. A base portion is provided below the connection, having an outside surface, and a bottom surface. At one or more slots are formed in the base portion. A cutter assembly is provided having a leg which is insertable into the slot of the bit body. A journal extends downward and inward from a transition portion of the leg, towards the center of the bit body. A cone is rotatably mounted on the journal. A plurality of cutters are located extending outward from the surface of the cone. A kerfing segment extends downward from the leg, beyond the journal. A plurality of cutters are positioned in the bottom of the kerfing segment.

Problems solved by technology

As the roller cone cutters roll on the bottom of the hole being drilled, the teeth or carbide inserts apply a high compressive load to the rock and fracture it.

When drilling rock with a roller cone cutter, the fracture effect of loading on the teeth of the rock bed is limited due to the rock matrix surrounding the borehole.

Thus, it appears in usual drilling operations that small cracks are created in the rock, which return to the surface of the bottom of the wellbore creating chips instead of propagating deep into the rock itself.

Thus, the bit tooth of the usual rock bit presses on the rock surface tending to create small cracks which propagate downward, but by virtue of the resistance to fracture offered by the surrounding rock matrix, a crack follows the path of least resistance and emerges at the surface on the bottom of the wellbore, thus creating the small chips.

This bit design causes rapid failure of the drag cutters, however, since virtually all the drilling fluid escapes through the windows and results in insufficient fluid flow to cool the drag bit component.

A primary disadvantage of the prior art designs is that they are extremely difficult and expensive to manufacture.

Due to the extremely high cost of manufacturing the prior art designs, they have proven to be inefficient in a cost per foot analysis.

Another disadvantage of the prior art designs is the time required for manufacturing the drill bits.

In the drilling industry today, there is significant pressure to keep inventory levels very low.

The prior art kerf-cutting hybrid bits having combined kerf cutting segments and rolling cone cutters take far too long to manufacture, and are far too expensive to keep in inventory.

The result is that they have become an impractical choice for the oilfield drilling.

Another disadvantage of the prior art designs is that they are less durable than required.

The assembly of rotating cone cutting structures within the geometrical constraints of the fully circumferential kerfing segments provides numerous challenges.

For example, prior art hybrid drilling bits utilize relatively smaller bearing and seal systems which are less reliable when drilling larger diameter holes.

As with the sealed bearing system, these elements are less durable, and drill slower than the larger cutting elements conventionally used when drilling wells of the same diameter.

Another disadvantage of the prior art designs is that they lack cutting removal ability, limiting the life of cutting elements and rates of penetration at which the drill bits can operate, and subjecting the bits to balling and premature failure.

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