RU2520317C2 - Pdc bit for horizontal well drilling - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to drilling bits used in construction of deep oil and gas wells, mainly for horizontal wells. PDC bit for horizontal well drilling has a body with a connecting thread, PDC rock cutting elements placed in sequence at one or more lead-in conical screw blades divided by conical spiral grooves with openings for attachments and passage of the flushing fluid. The bit peak is made as an elongated protrusion with the diameter base equal to d=(0.6÷0.7)D and height of h=(0.4÷0.6)D from the outer diameter B of the bit equipped with PDC-elements placed in planes close to the ones parallel to the axis of the bit, at two or more blades and flushing openings with attachments that forms at drilling a preliminary niche and conical screw blades from there cut the rock remaining at the well wall with an increased self-screwing effect.

EFFECT: improvement of drilling mechanical speed, stabilisation of cutting structure operation.

3 dwg

Description

The present invention relates to a tool for the construction of deep oil and gas wells, mainly horizontal sidetracks.

Known conical helical drill for drilling rocks [1]. This drill, adopted as an analogue, has a central interchangeable tip of a pointed shape, which plays the role of a pilot direction at the beginning of drilling, as well as a helical blade mounted on a central rod. Following the pointed tip, the helical blade with a constant pitch has a conical shape with a cone angle ranging from 15 ° to 20 °. When the drill rotates, the pointed tip is pressed into the rock, and the conical helical blade gradually expands the borehole diameter, crashing into its wall, while simultaneously causing the destroyed rock to move along the continuous curved helical space between the rod and the helical edge of the blade towards the wellhead.

The advantage of such a screw drill is that its outer working surface is conical with screw blades. The shape of these blades allows the drill to screw into the rock like a self-tapping screw. And as a “self-tapping screw” it requires significant axial effort only at the beginning of work until the well is deepened by several threads of screw blades into the rock. Then, the screw blade, cutting into the borehole wall along the helical surface, can significantly reduce the required axial load due to the decomposition of the applied force from the torque into two components, one directed along the surface of the cutting screw blade and the other along the drill axis. In this case, axial displacement - the introduction of the drill into the rock is possible practically without the use of axial load, only with the application of increasing torque from the drive of the drill.

Another advantage of a conical drill with a helical arrangement of a continuous blade is that during axial penetration, the vibrations and runout on the wall of the well inherent in roller cone bits are minimal, when the diameter obtained during drilling is larger than the diameter of the bit. In the latter case, transverse beating and vibrations that prematurely destroy the instrument are inevitable.

The disadvantages of this analogue include the fact that, as in any bit of a cutting type, the linear speed of movement of the cutting elements, and therefore the intensity of rock destruction, largely depends on their distance from the vertical axis of the bit. At the bottom periphery, the rate of destruction is maximum, and directly on the axis, the linear speed of the incisors is zero and the rate of rock destruction is minimal. In addition, as the central incisors become blunted, an ever increasing axial force is required to crush them, which makes it possible to create the necessary specific pressure greater than the limit of rock resistance to fracture.

With intensive destruction of the rock in the peripheral zone, the bit “hangs” on the crowns of the central zone, where the intensity of destruction lags behind the peripheral zone.

A diamond bit is also known [2], also taken as an analog. In this bit, armament is proposed as one of the options, including a multi-helical arrangement of the blades. The peripheral surface of the blades facing the borehole wall, as well as their end surface, are armed with fixed diamonds.

The advantage of this analogue is the screw arrangement of the blades, the horizontal projection of which, due to the inclination of the generators on the surface of the body, in total completely covers the entire length of the circumference of the bit along its largest diameter. This significantly reduces the possibility of radial runout of the bit and partially contributes to the effect of screwing it into the rock during rotation.

The disadvantage of the analogue under consideration, as well as the previous one, is the overload of weapons in the central zone, which contributes to a decrease in mechanical speed and “freezing” of the bit at the bottom of the well.

It is also known diamond bit [3], adopted as a prototype. This bit has a body with connecting thread, rock cutting elements, flushing channels, a core with breaker pins in an inclined flushing channel. The armament of the bit is made in the form of cutting rows of sequentially placed rock cutting teeth made of polycrystalline diamonds, or continuous crowns located on single-entry, two or more inlet conical helical blades separated by conical helical grooves to exit the bottom of the flushing fluid and particles of cuttings.

The bit is equipped with conical helical blades, a hole for the core. Several flushing channels with or without nozzles for cleaning the bottom of the cuttings are directed from the central channel to the external helical grooves. Part of the flushing fluid is directed into the gap between the wall of the hole under the core and the resulting core column. This gap is provided by rock-cutting elements at the end of the bit, drilling the core.

Armament elements located outside the bit along helical helical lines provide mechanical drilling speed with minimal radial runout of the bit. The effect of screwing external weapons into the rock at the same time reduces the axial load required for drilling from the weight of the drill pipe string.

The disadvantages of the prototype include the low resistance of a number of the lowest PDC teeth that drill the core base, as well as the fact that the core column impedes the flow of flushing fluid supplied through the central channel to the bottom.

Another disadvantage of the prototype is that the effect of self-tightening was influenced by too many turns that were simultaneously in contact with the surface of the face.

The technical result of the present invention is the creation of a drill bit with weapons, for example, from polycrystalline diamonds (PDC), having high mechanical speed during deep drilling of directional and horizontal wells, devoid of the disadvantages of analogues and prototype using their advantages.

The technical result is achieved in that in a PDC bit for drilling horizontal wells having a body with connecting thread, PDC rock cutting elements of any known shape, sequentially placed on one or more inlet conical helical blades with different angles of inclination, separated by conical helical grooves with holes for nozzles and passage of flushing fluid, the tip of the bit is made in the form of an elongated protrusion with a base diameter equal to d = (0.6 ÷ 0.7) D, and a height h = (0.4 ÷ 0.6) D from the outside the diameter of the bit D, equipped with PDC-elements located in planes close to the parallel axis of the bit, on two or more blades and flushing holes with nozzles, forming a preliminary niche during drilling, from which the conical helical blades destroy the remaining rock on the well wall with an enlarged self-tightening effect.

The list and description of the figures of the drawings.

Figure 1 shows a General view of the drill bit of the present invention.

Figure 2 shows a bottom view (from the end) of the proposed bit.

Figure 3 shows the cross section of the bit along the axis of the housing.

The bit 1 (figures 1, 2 and 3) has a body with a conical connecting thread 2, a neck 3, grooves 4 for fastening and further unfastening on the drill pipe string, belt 5, designed to accommodate calibrating wear-resistant teeth 6, PDC or carbide. The housing also has inclined helical blades 7 for accommodating rock cutting elements in the form of teeth made of polycrystalline diamonds PDC - 8, inclined helical grooves-grooves 9 for diverting the upward flow of flushing fluid from the bottom. Two or more blades 11 with teeth 15 located in planes close to parallel to the axis of the bit are located on the elongated protrusion 10 of the bit with a diameter of d. The teeth of the PDC 8 on each screw blade 7 are arranged one after another so that they, if possible, completely overlap their entire length. The inclination angles of the cutting surfaces of the teeth relative to the surface of the face are selected experimentally, depending on the hardness of the rocks intended for drilling. The number 12 indicates the side flushing holes with nozzles, the letter h denotes the height of the top of the elongated protrusion 10.

In figure 3, numeral 13 denotes an internal channel for directing washing fluid to the bottom; numeral 14 denotes washing channels with a nozzle at their outlet in an elongated protrusion 10. These nozzles may also have any known shape and method of attachment. The inner wall of the central channel and the walls of the channels leading the washing liquid to the nozzles can be reinforced, for example, with a diamond-containing cluster coating. The outer surface of the bit, including the elongated protrusion 10, may have a matrix protective layer (not shown). Of course, the shape of the placed side screw 8, as well as the arms of the top 15, can be not only in the form of elements with tablets made of polycrystalline diamonds, but also in another known design, for example, in the form of solid wedge-shaped helical crowns reinforced with wear-resistant material or carbide teeth, mounted on the crowns and on the end of the bit.

The ability to self-screw a bit into the rock depends on the angle α of the rise of the conical helical blades to the axis of the bit. Depending on the hardness of the drilled rocks, this angle is selected experimentally; its optimal value can fluctuate, as in the prototype, within α = 48 ° ÷ 75 °.

To increase the lifting intensity of the washing liquid and cuttings from the bottom, the side washing channels 12 connecting the inner central channel 13 with the external screw grooves grooves 9 can preferably be made at an acute angle to their surface in the direction of the upward flow of the washing liquid.

The bit works as follows. When drilling and deepening into the rock of the chisel, the central part of the face rock in the form of a niche turns out to be drilled primarily by weapons with the top of an elongated ledge. Upon entering this niche, the PDC teeth on the side conical helical blades come into operation and destroy the remaining rock on the well wall with an increased self-tightening effect.

The armament of the bit in the form of cutting rows on single-entry, two- or more inlet conical helical blades contributes to the effect of self-screwing the bit into the rock and to reduce the axial load required for drilling, which is difficult to ensure when drilling horizontal wells and their second shafts.

The presence of the self-tightening effect of the bit negates the possibility of beating of the bit and stabilizes the operation of weapons. The proposed location of the washing channels contributes to the intensification of cleaning the bottom of the cuttings. When working in soft and medium-sized rocks, for which the bit is mainly intended, the penetration and mechanical drilling speed increase significantly, which is confirmed by testing the prototypes directly in the field.

Information sources

1. US patent No. 3537537 from 11/3/1970, IPC E21C 13/04.

2. US patent No. 5004057 from 04/23/1987, IPC E21C 10/46.

3. RF patent No. 2360096 dated 06/27/2009, IPC E21B 10/00.

Claims (1)

 PDC bit for drilling horizontal wells, having a body with connecting thread, PDC rock cutting elements of any known shape, sequentially placed on one or more lead-in tapered helical blades with different angles of inclination, separated by tapered helical grooves with holes for nozzles and passage of flushing fluid characterized in that the tip of the bit is made in the form of an elongated protrusion with a base diameter equal to d = (0.6 ÷ 0.7) D, and a height h = (0.4 ÷ 0.6) D from the outer diameter of the bit D, equipped of PDC-members arranged in planes parallel close to the bit axis, two or more blades and flushing holes with nozzles forming the provisional niche during drilling, from which conical helical blades destroy the remaining rock at the borehole wall with an increased effect samozavinchivaniya.

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