A Composite Drill Bit Suitable for Difficult-Drilling Formation

Abstract

The invention discloses a composite drill bit suitable for a stratum difficult to drill. The composite drill bit suitable for the stratum difficult to drill comprises a drill bit body, cutter wings which are fixedly connected with the drill bit body, tooth wheels which are rotatably connected with the drill bit body, and water holes or nozzles which are arranged on the drill bit body. A plurality of first sets of cutting teeth are arranged on each cutter wing. Pits are formed in the sides, provided with the teeth, of the cutter wings and used for fixing the first sets of cutting teeth. The tooth wheels are rotatably connected with the drill bit body through tooth palms. Teeth are mounted on the tooth wheels. In the common coverage area of the body contour line of at least one cutter wing and the body contour line of at least another cutter wing, at least one non-overlapping area and at least one overlapping point or overlapping area exist. Through the structure characteristic, the drill bit can operate in an asynchronous cutting mode, the longitudinal abrasion length of the drill bit can be increased, and the service life of the drill bit can be prolonged; and the drill bit is in a high-specific-pressure drilling state in the whole drilling process, the capacity to intrude into rocks of the drill bit is improved, the drilling speed of the drill bit in the stratum difficult to drill is increased accordingly, and the service life of the drill bit in the stratum difficult to drill is prolonged.

Description

technical field [0001] The invention belongs to the technical equipment fields of petroleum and natural gas drilling engineering, mining engineering, building foundation engineering construction, geological drilling, tunnel engineering, hydrology, shield tunneling and non-excavation, and in particular relates to a drilling bit. Background technique [0002] Drill bits are rock-breaking tools used to break rocks and form wellbores in drilling engineering. PDC bits and roller cone bits are commonly used. PDC bits rely on high hardness, wear-resistant, self-sharpening polycrystalline diamond composite sheets to shear and break rocks. PDC bits have high mechanical penetration rate, long life and low drilling cost in soft to medium hard formations. are widely used in. Existing fixed cutter bits represented by PDC bits usually have several blades, and multiple cutting elements are arranged on the blades along the radial direction of the bit (for PDC bits, the cutting elements are...

AI Technical Summary

Problems solved by technology

However, the longitudinal backup teeth in the above two schemes are all internal inserts, and the main cutting teeth work according to the principle of synchronous cutting. The internal inserts as an auxiliary cutting structure must be used after the main cutting teeth are completely worn out and the body is partially worn. However, while the internal inserts are cutting rocks, the body of the blades has been in contact with the formation in a large area, which significantly reduces the specific pressure of the reserve cutters acting on the rocks, thus greatly limiting the drilling efficiency of the drill bit

[0010] The existing PDC bit with synchronous cutting principle is not only limited in drilling efficiency but also has a short service life when facing complex and difficult-to-drill formations (high hardness, high abrasiveness, even heterogeneous formations containing gravel layers, interlayers, etc.). ideal

The main reasons are as follows: First, in order to ensure that the drill bit has a strong ability to eat or penetrate the rock surface when drilling in hard formations, it is necessary to use cutting teeth with a small size (diameter), but the small diameter cutting teeth The exposed height is small, and the wearable height is significantly lower than that of the large-diameter cutter, but the wear speed of the cutter is faster at this time, thus forming an insoluble contradiction in the design of the drill bit for difficult-drilling formations: if the large-diameter cutter is used , the cutting teeth are difficult to penetrate into the rock (especially after a certain degree of wear), and the rock breaking efficiency of the drill bit is low; if the small diameter cutting teeth are used, the working life of the cutting teeth is not enough

Second, when the drill bit drills in hard formations and heterogeneous formations, the cutting teeth are often subjected to strong impact loads, and a small number or even individual cutting teeth are prone to rapid failure phenomena such as shedding, fracture, fragmentation, and cracking of the diamond layer. Once this phenomenon occurs, it will lead to the chain failure of the cutting teeth in the adjacent area due to the increase of the working load, and then the circumcision phenomenon, that is, the exposed part of the cutting teeth of the drill bit in the radial area is completely or mostly worn off. , and then grind out annular grooves on each blade body of the drill bit

Therefore, when the ring groove is worn out on the drill bit, it is generally considered that the drill bit has lost or is close to losing its cutting ability. Not only can it not be used in the well, but even repair (replacement or refurbishment of the worn cutting teeth) is difficult to implement in severe cases.

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