Turbodrill

Abstract

A turbodrill comprises a housing coupled with its one end to a drill pipe for feeding drilling fluid, the housing accommodating a hydraulic downhole motor comprising a multistage turbine. Each stage of the multistage turbine comprises a directing stator disk defining through passages and a working rotor disk defining through passages, the rotor disk being installed on a shaft. The shaft is rotatably mounted in the housing on supports and carries a rock breaking tool on the end thereof facing the bottomhole. The total area of the inlet openings of the stator disk through passages is from about ⅕ to about ⅗ of the total area of the inlet openings of the rotor disk through passages.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the drilling technology for drilling wells in different geologic rocks, and more particularly to a turbodrill.

BACKGROUND OF THE INVENTION

[0002] Increasing volumes of drilling production and prospecting wells for oil and gas recovery have called for the development of new type turbodrills allowing the use of present-day rock breaking tools made from high-strength hard-alloy materials with a torque strength on the shaft of the order of 2000 Nm. However, the known designs of hydraulic downhole motors used in turbodrills cannot provide normal operation of the new type rock breaking tools because of the low power and torque strength.

[0003] Therefore, attempts to increase the torque strength of the downhole motor transmitted to the turbodrill rock breaking tool have led to the development of a turbodrill described in the “Drilling Engineer's Handbook” by V. I. Mishchevich and N. A. Sidorov (Eds.), vol. 1, Moscow, Nedra Publ. House, pp. 212-213, FIG. VI.1, 1973 (in Russian). The known turbodrill comprises a housing coupled with its one end to a drill pipe for feeding drilling fluid. The housing accommodates a hydraulic motor comprising a multistage turbine, each stage of which is constituted by a directing stator disk defining through passages and a working rotor disk defining through passages. The rotor disk is installed on a shaft rotatably mounted in the housing on supports and carries a rock breaking tool on the end thereof facing the bottomhole. The total sectional area of the stator disk through passages corresponds to the total sectional area of the rotor disk through passages.

[0004] The through passages of the stator and rotor disks are defined by profiled blades providing an increase of the drilling fluid pressure, that results in an increase of the power and torque strength acting on the rock breaking tool. In order to substantially increase the downhole drive power and the developed torque strength on the rock breaking tool, more than 300 stages are installed on the shaft thereof, the result being a significant increase of the turbodrill dimensions, causing deformation of the stator and rotor disks, that may lead to breakage thereof. As a result, the turbodrill service life becomes reduced, and the cost of drilling operations increases. The closest technical solution in terms of the totality of essential features and of the achieved result is a turbodrill known from the textbook “Drilling Oil and Gas Wells” by Sereda N. G., Soloviev E. M. (Eds.), Moscow, Nedra Publ. House, pp. 109-110, FIGS. 71, 72, 1974 (in Russian).

[0005] The known turbodrill comprises a housing coupled with its one end to a drill pipe for feeding drilling fluid. The housing accommodates a hydraulic motor comprising a multistage turbine, each stage of which is constituted by a directing stator disk defining through passages and a working rotor disk defining through passages. The rotor disk is installed on a shaft rotatably mounted in the housing on supports and carries a rock breaking tool on the end thereof facing the bottomhole. The total sectional area of the stator disk through passages corresponds to the total sectional area of the rotor disk through passages. In the process of drilling, the rock breaking tool is brought in rotation by a hydraulic downhole motor. The flow of the drilling fluid fed through the drill pipe changes its direction in the stator disk and in the rotor disk, and, flowing from one stage into another, gives off a part of its hydraulic power to each stage. As a result, the power generated by all the stages is summarized on the turbodrill shaft and is transmitted to the rock breaking tool. However, the above-described design of the turbodrill cannot provide the power and torque strength sufficient for the normal operation of the new type rock breaking tool, unless the number of the downhole motor sections is increased.

BRIEF DESCRIPTIONS OF THE INVENTION

[0006] It is an object of the present invention to provide a turbodrill in which, owing to structural changes in the stator disk, a significant increase in the power and torque strength on the rock breaking tool can be ensured without increasing the number of the downhole motor sections.

[0007] Another object of the present invention is to make the turbodrill less metal-intensive.

[0008] One more object of the present invention is to simplify the design and to prolong the service life of the turbodrill.

[0009] According to the above-stated and other objects, the essence of the present invention is that in a turbodrill comprising a housing coupled with its one end to a drill pipe for feeding drilling fluid, the housing accommodating a hydraulic downhole motor which comprises a multistage turbine each stage of which is constituted by a directing stator disk defining through passages and a working rotor disk defining through passages, the rotor disk being installed on a shaft rotatably mounted in the housing on supports and carrying a rock breaking tool on the end thereof facing the bottomhole, according to the invention, the total area of the inlet openings of the stator disk through passages is from about ⅕ to about ⅗ of the total area of the inlet openings of the rotor disk through passages.

[0010] Such an embodiment of the stator disk provides an increase of the drilling fluid pressure in the through passages defined by the blades thereof. As a result, the torque strength on the rotor disk blades increases. For instance, with the rotor disk rotating with a speed of about 500 rpm and with the stator disk embodied according to the present invention, a torque strength of about 1800 Nm is provided on the rock breaking tool with one-section embodiment of the downhole motor. A stator disk having the total area of the inlet openings of the through passages less than ⅕ of the total area of the inlet openings of the rotor disk through passages will result in a substantial growth of the pressure drop on the stator disk and on the rotor disk, bringing about higher hydraulic losses and decreasing the turbodrill efficiency, as well as intensive wear of the flow part of the stator disk and the rotor disk for each stage and axial support of the shaft.

[0011] An embodiment of the stator disk with the total area of the inlet openings of the through passages more than ⅗ of the total area of the inlet openings of the rotor disk through passages will result in a decrease of pressure on the stator disk, which in turn will reduce the pressure drop of the drilling fluid between the stator disk and the rotor disk. This will lead to reducing the torque strength and decreasing the power of the turbodrill, i.e., the values thereof will approach those of the widely used well-known turbodrills.

[0012] It is preferable that the inlet openings of the through passages of the stator disk of all the stages should lie in one diametral plane and form a through axial duct with the longitudinal axis thereof parallel to the axis of the shaft.

[0013] Such structural embodiment of the stator disk makes it possible to feed the drilling fluid with a lower pressure drop at each stage of the downhole motor with the required flow-in of the drilling fluid and to provide the required torque strength for effective operation of the rock breaking tool.

[0014] It is no less preferable that the inlet openings of the through passages of the stator disk of each stage subsequent to the incoming flow of the drilling fluid should be displaced circumferentially to the inlet openings of the stator disk of the preceding stage through at least 1 degree, so that the outlet openings of the stator disk through passages of all the stages be disposed along a helical line with a center lying on the shaft axis.

[0015] Such structural embodiment of the stator disk results in a displacement of the drilling fluid flow and in an appearance of a horizontal component thereof, the direction of whose vector is accordant with the direction of rotation of the rotor disk. Thereby an additional torque strength is created on the rotor disk blades. For instance, with the inlet openings of the through passages of the stator disk of each stage subsequent to the entering flow of the drilling fluid displaced circumferentially through 15 degrees with respect to the inlet openings of the stator disk of the preceding stage, at least one of the outlet openings of the through passages of the of the stator disk of the preceding stage is closed. A part of fluid acting on the blades of the rotor disk enters a closed space defined by the body of the stator disk of the subsequent stage, by the walls of the through passage of the rotor disk and by the walls of the through passage of the stator disk of the preceding stage, one of the walls being a side of the stator disk blade, and the other being the body thereof. Such a phenomenon is typical of volumetric downhole motors which are noted for enhanced power and torque.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other objects and advantages of the invention will become more apparent from the following particular exemplary embodiment thereof and the drawings, in which:

[0017] FIG. 1 shows diagrammatically a turbodrill according to the invention, with a partially exploded view;

[0018] FIG. 2 shows a scaled-up view of the flow part assembly shown in the exploded view;

[0019] FIG. 3 shows section A-A in FIG. 2;

[0020] FIG. 4 shows a developed view of the flow part of two stages of a downhole motor;

[0021] FIG. 5 shows a developed view of the flow part of two stages of a downhole motor, a variant of embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0022] A turbodrill according to the present invention comprises a housing 1 (FIG. 1) coupled with one end 1a to a drill pipe 2 for feeding drilling fluid, the housing accommodating a hydraulic downhole motor 3 comprising a multistage turbine. Each stage is constituted by a directing stator disk 5 defining through passages 4 (FIG. 2) and a working rotor disk 7 defining through passages 6. The disks 7 are installed on a shaft 8 which is rotatably mounted in the housing 1 on supports (not shown in the drawings) and carries a rock breaking tool 9 on its end 8a facing the bottomhole. The total area of inlet openings of the through passages 4 of the stator disk 5 is from about ⅕ to about ⅗ of the total area of inlet openings of the through passages 6 of the rotor disk 7 of each stage.

[0023] Inlet openings 4a of the through passages 4 of the stator disks 5 of all the stages lie on one diameter and constitute an open axial duct 10 whose longitudinal axis 10a is parallel to an axis 11 of the shaft 8. The proposed embodiment of the stator disk 5 makes it possible to feed the drilling fluid with a lower pressure drop at each stage of the downhole motor with the required flow-in and to provide the required torque strength for effective operation of the rock breaking tool 9.

[0024] The turbodrill operates in the following manner. Drilling fluid shown with dotted arrows k is fed along the drill pipe 2 to the housing 1 of the turbodrill. The hydraulic energy of the fluid flow is converted into mechanical energy of rotation of the shaft 8 carrying the rock breaking tool 9. The drilling fluid flow interacts with the body of the stator disk, then enters through a limited number of the inlet openings 4a into the through passages 4 restricted by blades 12, and leaves said passages in the form of jets. Said jets of the drilling fluid act on blades 13 of the rotor disk 7, then a part of the jet flow is directed via the through passages 6 of the rotor in an axial direction to the inlet openings 4a of the through passages 4 of the stator of the subsequent stage stator, while another part of the jet flow continues to move substantially in a horizontal direction, since it is found in a closed space defined by the body of the stator disk 5 of the preceding and subsequent stages and by the sides of the blades 13 of the rotor disk 7. The movement of a part of the fluid jet flow in a horizontal direction shown by arrow m promotes an increase in the torque strength on each stage of the downhole motor, this resulting in an increase of the torque strength on the turbodrill shaft. The latter circumstance, with a required flow-in of the drilling fluid, causes a reduction of the number of the turbodrill stages when developing of the necessary torque strength on the shaft thereof, providing effective operation of the present-day rock breaking tool.

[0025] A variant of the turbodrill embodiment, according to the present invention, is structurally similar to the above-stated, the difference being in the structural embodiment of the stator disk 14. In the stator disk 14 (FIG. 5) of each subsequent stage the inlet openings 15a of the through passages 15 with respect to the incoming flow of drilling fluid along arrow k are displaced circumferentially relative to the inlet openings 15a of the stator disk 14 of the preceding stage through at least 1 degree, so that outlet openings 15b of the through passages 15 of the stator disk 14 of all the stages are disposed along a helical line with a center lying on the axis 11 of the shaft 8.

[0026] The turbodrill embodied as described in the above variant, operates in the following manner. Drilling fluid is fed along the drill pipe 2 to the housing 1 of the turbodrill, and the drilling fluid via the through passages 15 of the stator disk 14, defined by the blades 12, comes to the blades 13 of the rotor disk 7. Owing to the displacement of the inlet openings 15a of the stator disk in each stage there occurs a circumferential displacement of the drilling fluid flow and a horizontal component thereof appears, whose vector is accordant with the direction of rotation of the rotor disk 7. Thereby an additional torque strength is created on its blades 13.

[0027] This is due to the fact that a part of the inlet and outlet openings of the rotor of the preceding stage prove to be closed by the body of the stator of the preceding and subsequent stages. Thus a part of the drilling fluid acting on the blades 13 of the rotor disk 7 proves to be in a closed space defined by the body of the stator disk 14 of the preceding and subsequent stages and by the sides of the blades 13 of the rotor disk 7 of the preceding stage. The fluid found in the limited volume interacts with the blades 13 of the rotor disk 7, creating increased torque strength on the shaft 8. The flow of the drilling fluid moving from one stage to another is helix-shaped. Such character of the drilling fluid movement is typical of volumetric downhole motors noted for enhanced power and torque strength. For instance, circumferential displacement of the inlet openings 15a of the stator disk 14 of each subsequent stage in respect to the incoming flow of the drilling fluid, e.g., in the direction of rotation of the rotor disk through 15 degrees, i.e., for blade pitch of the rotor disk 7, results in closing thereof. Thereby an additional volume of fluid acting on the blades 13 of the rotor disk 7 is created. This additional volume is created in the closed space defined by the body of the stator disk 14 of the subsequent stage, by the walls of the through passage 6 of the rotor disk 7 and by the walls of the through passage 4 of the stator disk 14 of the previous stage, one of which is a side of the blade 12 of the stator disk 14, and the other is the body thereof. A still greater increase in the volume of the fluid acting on the rotor blades results in an even greater increase in the torque strength on the shaft of the turbodrill.

[0028] All the above-stated results either in increasing the torque strength on the shaft of the turbodrill, for example, by 30% with a preset flow-in of the drilling fluid or in preserving the required torque strength, e.g., of 2000 Nm, on the shaft of the turbodrill with a decreased flow-in of the drilling fluid, that allows using the turbodrill with present-day high-performance rock breaking tools.

Claims

1. A turbodrill in combination with a drill pipe comprising:

a housing which is a bearing member and has two ends, one of said ends being coupled to said drill pipe;

a hydraulic downhole motor arranged in said housing;

a multistage turbine of said hydraulic downhole motor;

a directing stator disk of said multistage turbine, secured in said housing;

supports installed in said housing;

a shaft rotatably mounted in said housing on said supports, having an axis and a carrying end facing the bottomhole;

a working rotor disk of said multistage turbine disposed on said shaft;

each stage of said multistage turbine constitututed by said directing stator disk and working rotor disk, installed sequentially downstream the drilling fluid;

through passages formed in said directing stator disk;

through passages formed in said working rotor disk;

inlet openings of said through passages in said working rotor disk;

inlet openings of said through passages in said directing stator disk, the total area of said inlet openings of said through passages in said directing stator disk being from about ⅕ to about ⅗ of the total area of said inlet openings of said through passages in said working rotor disk;

a rock breaking tool secured on said carrying end of said shaft.

2. A turbodrill according to claim 1, comprising:

a diametral plane, in which there lie said inlet openings of said through passages in said directing stator disk of said each stage;

a through axial duct formed by said inlet openings of said through passages in said directing stator disk of said each stage, lying in said diametral plane, said duct having a longitudinal axis parallel to said axis of said shaft.

3. A turbodrill according to claim 1, wherein said inlet openings of said through passages of said directing stator disk of said each stage being subsequent with respect to the incoming flow of the drilling fluid are displaced circumferentially through at least 1 degree relative to said inlet openings of said through passages of said directing stator disk of said each preceding stage, so that said outlet openings of said through passages of said directing stator disk of all the stages of said multistage turbine are disposed along a helical line with a center lying on said axis of said shaft.

4. A turbodrill according to claim 2, wherein said inlet openings of said through passages of said directing stator disk of said each stage being subsequent with respect to the incoming flow of the drilling fluid are displaced circumferentially through at least 1 degree relative to said inlet openings of said through passages of said directing stator disk of said each preceding stage, so that said cutlet openings of said through passages of said directing stator disk of all the stages of said multistage turbine are disposed along a helical line with a center lying on said axis of said shaft.