Compound bit formed by rotary cutting bit and PDC (polycrystalline diamond compact) blades

Abstract

The invention discloses a compound bit formed by a rotary cutting bit and PDC (polycrystalline diamond compact) blades. The compound bit comprises a main body (1), rotary cutting bit cones (2), rotary cutting bit cutting teeth (3), PDC blades (4), PDC cutting teeth (5), oil storage sacs (6) and nozzles (7), wherein the main body (1) comprises a cone journal, centralizing blocks, high-pressure slurry channels and a connection screw thread. The compound bit is characterized in that a compound bit cutting unit comprises the rotary cutting bit and a PDC bit cutting unit. The compound bit has the following beneficial effects: the rotary cutting bit completes drilling the central part of the borehole in the drilling process; the rotary cutting bit in the compound bit shocks, crushes and cuts the rocks by way of rotary cutting, has high central rock breaking efficiency, high rate of penetration and better dynamic performance, is uniform in wear, simultaneously improves the bit bearing structure and ensures to prolong the service life of the bit while improving the rock breaking efficiency; and the linear velocity of the periphery of the borehole is high in the drilling process and the rotary cutting bit and the PDC bit cutting unit complete drilling the periphery of the borehole, thus improving the cutting capability of the compound bit and ensuring good gauge protection effect.

Description

technical field [0001] The invention belongs to the field of technical equipment such as oil and gas drilling engineering, mining, geological drilling, construction engineering, tunnel engineering, shield tunneling and non-excavation, and relates to a composite drill bit formed by a rotary cutting drill bit and a PDC blade. Background technique [0002] The drill bit is a tool that directly contacts the rock during the drilling process and breaks the rock through cutting and punching. The drill bits widely used in modern drilling engineering mainly include roller cone bits and PDC bits (Polycrystalline Diamond Compact Bits). Today, both the roller cone bit and the PDC bit have been developed to a fairly high level, but there are still some insurmountable problems. One is fear of reaming and reaming, which will damage the roller cone bit of the sealed bearing, especially the PDC bit; the other is that the movement of the center rock at the bottom of the well is small, the fu...

AI Technical Summary

Problems solved by technology

Since the compressive strength of the rock is much greater than the shear and tensile strength, and the three-cone bit uses the impact of the teeth on the rock to break the rock, the energy utilization rate is not high

Especially in the case of high drilling pressure such as deep well drilling, due to the action of high-density drilling fluid, the cuttings holding effect at the bottom of the well is obvious, and it is difficult for the drill bit teeth to impact the broken rock, so the rock breaking efficiency is relatively low

[0004] The bearing life of the tri-cone bit is one of the main factors restricting the service life of the bit. The bearing bears the load caused by the drilling pressure. In addition, the tri-cone bit breaks the rock in the form of impact. The impact load on the bearing is large, and the load amplitude is high. In addition, The speed-up effect of the tri-cone bit: the body speed ratio of the tri-cone bit (the ratio of the rotational speed of the cone to the rotational speed of the bit during drilling) is greater than 1, that is, the rotational speed of the cone is greater than the speed of penetration of the bit when the bit is drilling, so the rotational speed of the bearing is relatively low. faster, resulting in shorter bearing life for tricone bits

The single cone bit is characterized by low cone speed, large bearing size, and longer service life than the three-cone bit. However, the single-cone bit has unavoidable shortcomings: the full-hole structure of the single-cone bit determines its rock-breaking process. Prone to repeated crushing and difficult chip removal

[0008] (1) High requirements on the bottom of the well: If there are foreign objects at the bottom of the well, it will cause chipping or thermal friction of the PDC bit, the temperature will rise and the carcass will be blackened, and even the brazing layer will be melted, resulting in tooth loss and affecting the ROP. Accelerated bit failure

[0009] (2) Serious consequences of PDC tooth failure: Compared with the roller cone bit, the failure of individual teeth of the PDC bit (tooth loss, tooth collapse, etc.) will seriously increase the load of nearby PDC teeth, accelerate its wear rate, and aggravate the failure of the drill bit

[0010] (3) The rock-breaking efficiency of the core is not high: the wear speed of the PDC teeth on different radial regions of the PDC bit is significantly different, and the outer shoulder cuts a large proportion of rocks, and the wear speed is fast

[0012] (1) The efficiency of center rock breaking is not high: since the composite drill bit is composed of roller cone bits, its rock breaking form is still impact crushing, and the energy utilization rate is not high

Like the roller cone bit, in the case of high bit pressure, due to the effect of high-density drilling fluid, the cuttings holding effect at the bottom of the well is obvious, and the bit teeth are difficult to impact and break rock, and the rock breaking efficiency is relatively low, especially in the borehole. In the center, the situation is more serious

[0013] (2) Severe wear and tear on the peripheral bit of the wellbore: near the periphery of the wellbore of this type of compound drill bit, the cone size of the roller cone bit is relatively small, but the high speed of the drilling process will accelerate the wear and failure of the bit, and at the same time cause the bit to appear molar back Phenomenon

[0014] (3) The service life of the central and peripheral cones is not equal, and the service life of the composite drill bit is not high: based on the rock-breaking mechanism and structural composition of this type of composite drill bit, the rock-breaking efficiency of the center is not high, while the structure size of the cones on the periphery of the borehole is small and the speed is low. High and severe wear, resulting in differences in the life of the roller cone bits in the center of the wellbore and the periphery of the wellbore, making it difficult to achieve overall optimization and life improvement of the composite drill bit

The rock breaking at the center of the composite drill bit is completed by the blade, which still cannot change the low efficiency of rock breaking at the center of the PDC bit

At the same time, the roller cone drill in the composite drill bit still cuts the periphery of the borehole with a large circle, and the small ring gear cuts the center of the borehole, which cannot effectively improve the bearing size and the life of the drill bit.

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