A Long-Life Reaming Drill Bit in Difficult-Drilling Formation

Abstract

The invention discloses a reaming drill bit with a long service life for strata difficult to drill. The reaming drill bit comprises a drill bit body and a plurality of blades. The drill bit body comprises a pilot body and a reaming body; the blades extend from the pilot body and the reaming body, water holes are formed in flow channels among the blades, or spray nozzles are arranged in the flow channels among the blades, a plurality of first groups of cutting teeth are arranged on the blades, pits are formed in tooth distribution surfaces of the blades and are used for fixing the first groups of cutting teeth, and contour lines of bodies of the blades of at least two pilot sections and / or at least two reaming sections have non-coincidence regions and coincidence points or coincidence regions. The reaming drill bit with structural characteristics has the advantages that the reaming drill bit can work in asynchronous cutting modes, the abrasive lengths of the blades can be increased, and the service life of the reaming drill bit can be prolonged; the reaming drill bit can be in high-specific-pressure drilling states in integral drilling procedures, the rock intrusion capacity of the reaming drill bit can be enhanced, accordingly, the drilling speeds of the reaming drill bit in the strata difficult to drill can be increased, and the service life of the reaming drill bit in the strata difficult to drill can be prolonged.

Description

technical field [0001] The invention belongs to the technical equipment fields of oil and natural gas drilling engineering, mining engineering, building foundation engineering construction, geological drilling, tunnel engineering, hydrology, shield tunneling and trenchless, in particular to a drilling bit. Background technique [0002] With the increasing number of casing windows and sidetracking and secondary development of old wells, reaming tools have been widely used. There are usually two ways of reaming construction in drilling engineering: First, use a conventional drill to drill a pilot hole (ie, a pilot hole), and then use a reaming bit or tool for reaming construction, that is, drilling a pilot hole. Reaming and reaming are carried out separately; secondly, the method of "reaming while drilling" is used to ream while drilling, and the drilling and reaming constructions are completed at one time. The reaming bit (also known as the reaming tool) is usually composed ...

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

[0012] Similar to the ordinary PDC bit, the existing PDC reaming bit with synchronous cutting principle not only improves the drilling efficiency when facing complex and difficult-drilling formations (high hardness, high abrasiveness, even gravel-containing layers, interlayers and other heterogeneous formations). Limited and its service life is not 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 cause 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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