DOWNHOLE SCREW MOTOR

Abstract

To obtain technical result—creation of a new downhole screw motor ensuring a higher efficiency and increasing performance coefficient of a motor and motor operational life, improving of drilling efficiency—in a downhole screw motor comprising a stator having an internal screw surface, a rotor placed inside a stator having external screw surface, a sealing system, a spindle assembly, as per the invention as a sealing system the following system is used: a system, which contains a contact elastic, multilayered sealing agent, moreover a tough straps making layers in a sealing agent, have close ring-like shapes and are similar to the surface, to which they are fixed; the quantity of layers of a sealing agent is not more than six; in the layers separately gas and/or liquid is used as sealing media; a sealing system contains a separation joint of drilling mud flow, an electrogenerating turbine, a pumping unit for drill mud, regulating units of movement direction of sealing media and drill mud, a mud hopper, automatic control system and also, in accordance with applied sealing media, a tank-stabilizer with gas, a compressor, a heat exchanger for gas cooling and/or a tank-stabilizer with liquid, a pump, a heat exchanger for liquid cooling.

Description

TECHNICAL FIELD

The invention relates to drilling equipment.

BACKGROUND ART

It is known a downhole screw motor comprising a body; a stator, fixed inside a body; a rotor, placed inside a stator; a spindle assembly; in the above motor the cover (made of elastomer, for example, rubber) fixed on the stator and having an internal screw surface, is used as contact elastic sealing agent between a metal rotor and a stator. (Baldenko D. F., Baldenko F. D., Gnoyevykh A. N. Downhole screw motors: Information Manual—M.: OJSC <<Publishing Office <<Nedra>>, 1999, 375 Page).

It is known a downhole screw motor comprising a body; a stator, fixed inside a body, a rotor placed inside a stator; the quantity of screw lobes of a rotor is one less than a stator, a spindle assembly; in the motor the cover (made of elastomer, for example, rubber) applied on the metal frame of a rotor, is used as contact elastic sealing agent between a rotor and a stator. (Patent RU No. 2011778, IPC E 21 B 4/02 dated 30 Apr. 1994).

Closest analogous solution is a downhole screw motor comprising a body; a stator, fixed inside a body; a rotor, placed inside a stator; the quantity of screw lobes of a rotor is one less than a stator, a spindle assembly; in the motor the following system is used as a sealing system—screw cavities have been milled on the body; hollow hoses of special profile are put inside above screw cavities; one end of a special profile hose is plugged, and other end is connected to a common manifold; above the hoses, inside the body a rubber stator is cured-on so that stator's screw surface is coincident with screw cavities of a body; the hose cavity through manifold and back pressure valve built in a body are filled in with oil under pressure and by that the hoses filled by oil to a certain level, are designed for compensating for wear of a stator top. (Inventor's Certificate USSR No. 1717782 A1, IPC E 21 B 4/02 dated 7 Mar. 1992).

In all of these prior arts, elastomer—rubber used for sealing purpose, has the following ineffective physical and mechanical characteristics:

For example, in comparison with steel, there is a high friction coefficient for the pair rubber-steel and pair rubber-rubber, low tensile strength, low heat (Patent RU No. 2145012, IPC F 16 F 15/00 dated 27 Jan. 2000; Chemical Encyclopaedical Dictionary/Head Editor I. L. Knunyants.—Moscow: Soviet Encyclopedia, 1983.—791 Pages).

Due to ineffective physical and mechanical characteristics of rubber, prior art has common disadvantages: the applied sealing agents are characterized by increased wear, reduced strength, reduced heat-resistant feature, not wide temperature and pressure range for operation, impossibility of efficient control for the sealing agent temperature to maintain a constant working temperature, impossibility to eliminate the overheating resulting in rubber destruction; the use of rubber for the sealing of moving elements in known downhole motors reduce the effectiveness, performance coefficient and motor operational life, decrease drilling efficiency.

SUMMARY OF INVENTION

Technical object of the invention is creation of a new downhole screw motor removing the above mentioned disadvantages of prior art, which will ensure a higher effectiveness, increasing performance coefficient of a motor and motor operational life, improving of drilling efficiency.

In order to solve this technical object in a downhole screw motor comprising a stator having internal screw surface; a rotor having external screw surface and placed inside stator, the quantity of screw lobes of a rotor is one less than of a stator; a sealing system, a spindle assembly in accordance with an invention as a sealing system the following system is used: a system, which consists of a contact elastic, multilayered sealing agent rigidly connected either with a stator or with a rotor or consists of two sealing agents, which are separately rigidly connected one with a stator, the other with a rotor; moreover a tough straps (made of strong material, for example, metal) making layers in a sealing agent, have close ring-like shapes and are similar to the surface, to which they are fixed; the quantity of layers of a sealing agent is not more than six; in the layers gas and/or liquid is used as sealing media; a sealing system contains a separation joint of drilling mud flow, electrogenerating turbine, a pumping unit for drill mud, regulating units of movement direction of sealing media and drill mud (for example, back pressure valves), a mud hopper, automatic control system (hereinafter, ACS), as well as in accordance with applied sealing media, tank-stabilizer with gas, a compressor, a heat exchanger for gas cooling and/or tank-stabilizer with liquid, a pump, a heat exchanger for liquid cooling.

The conceptual design and function of the above mentioned contact elastic, multilayered sealing agent is described in the original source (Innovative Patent KZ No. 23655, IPC F16J 15/16 dated 17 Jan. 2012).

The concept of the invention is illustrated by schematic drawings, describing one of the best options of offered subject containing contact elastic, multilayered sealing agent rigidly connected with a stator; in the agent in the layers gas and liquid in the order of interchange are used as sealing media. Reviewing of these schemes is enough to understand the concept of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a general scheme of an offered downhole screw motor.

FIG. 2 is a scheme containing a part of contact elastic, multilayered sealing agent,

FIG. 3 and FIG. 4 are sectional elevations A and B accordingly.

MODES FOR CARRYING OUT THE INVENTION

A downhole screw motor comprises a stator 1, a rotor 2, a sealing system containing a separation joint of drilling mud flow 3, a contact elastic, multilayered sealing agent 4, rigidly connected with a stator 1, moreover a tough straps 5 making layers in a sealing agent 4, have close ring-like shapes and are similar to the surface, to which they are fixed, tank-stabilizer with gas 6, a compressor 7, tank-stabilizer with liquid 8, a pump 9, a heat exchanger for gas cooling 10, a heat exchanger for liquid cooling 11, an electrogenerating turbine (electric generator) 12, pumping unit for drill mud 13, regulating units of movement direction of sealing media and drill mud 14 (for example, back pressure valves), a mud hopper 15, ACS 16. (It should be noted that in case when two separate contact elastic multilayered sealing agents, one of which rigidly connected with a stator, and the other with a rotor, are used; drill mud moves between these sealing agents). At the same time drill mud specified as 17, sealing media: gas-18 and liquid-19 are used in a downhole screw motor.

Offered downhole screw motor operated as follows.

High pressure supplied drill mud enters a separation joint of drilling mud flow 3 and is divided into three flows. The first flow forms a main flow of drill mud and is consumed directly for operation of a downhole screw motor providing a running torque of a rotor 2 relative to a stator 1. The second flow is directed to an electrogenerating turbine 12, the third flow—to heat exchanger for gas cooling 10 and heat exchanger for liquid cooling 11. Drill mud is a working substance of an electrogenerating turbine 12, drill mud passing through an electrogenerating turbine generates electric energy to power equipment elements. Drill mud also used as cooling agent in heat exchangers 10 and 11, applied in order to control temperature of sealing media of a sealing system of an offered downhole screw motor. A separation joint of drilling mud flow 3 is managed by ACS 16, which increases or decreases the quantity of bleed drill mud for the operation of electrogenerating turbine 12 depending on required horse power of appropriate consumer of an offered device. Also under the control of ACS a separation joint of drilling mud flow 3, changing the quantity of drill mud delivered to heat exchangers 10 and 11, ensures the temperature control of sealing media (gas and liquid) in a sealing system. Managed by ACS 16 tank-stabilizers 6 and 8, a compressor 7, a pump 9, heat exchangers 10 and 11 regulate pressure and flow rate of sealing media (gas and liquid), increasing or decreasing permeability of clearance between a stator and a rotor, in the same way allow to regulate rotational torque of a downhole screw motor and to control drilling process, it is of great importance and significantly distinguishes an offered subject matter from the prior art. ACS 16, besides the specified operations of regulation and control, ensures the forcing of drill mud through electrogenerating turbine 12, regulating units of movement direction of sealing media and drill mud 14 and provides the delivery of waste mud to pumping unit for drill mud 13 followed by accompanied by connection with main flow of drill mud.

Tank-stabilizer with gas 6 and tank-stabilizer with liquid 8 allow operating relatively a compressor 7 and a pump 9 with different efficiency, depending on the change of power on a shaft of a rotor 2 of a downhole screw motor. Additionally the design of tank-stabilizers 6 and 8 ensures the presence of initial pressure and ensures the possibility of compensation of dynamic impulse and temperature expansion of gas and liquid during the operation and motion of a drilling system in rock formation having a definite temperature gradient. Tank-stabilizers 6 and 8 together with a compressor 7 and a pump 9 allow control a sealing system creating an opportunity to control rotational torque on a rotor 2 within a specified range, namely bypassing through a contact elastic, multilayered sealing agent 4 more or less of sealing media.

Availability of a compressor 7 and a pump 9 ensures continuous pumping of sealing media through sealing layers 4, as well as through heat exchangers for gas and liquid 10 and 11. Sealing media (gas and liquid) heated during operation enter relatively to heat exchangers 10 and 11. Heat removal is ensured by delivery of drill mud as a cooling agent as per classical scheme for such type of equipment. Regulating units of movement direction of sealing media and drill mud 14 applied in the device prevent the back motion of drill mud and sealing media (gas and liquid), ensure the unidirectionality of motion. A mud hopper 15 ensures the delivery of a waste drilling mud after heat exchangers 10 and 11 and after electrogenerating turbine 12 back to main flow of drill mud and directs it to a pumping unit for drill mud 13. Then drill mud is sent directly to hollow spaces of operating chambers of a gerotor mechanism, the hollow spaces formed by a stator 1 and a rotor 2. A rotational torque, arising on a rotor 2, causes its eccentric motion regarding a stator 1, the eccentric motion then transforms into rotating motion of a shaft of a spindle assembly (not shown in Figures.). Drill mud from operating chambers enters rock destruction tool and then the downhole.

Based on practical experiments concerning the development of thermal conditioning of multilayered sealing agent in order to maintain its operational temperature, it is reasonable to limit the quantity of layers of a sealing agent to no more than six. The condition required the quantity of layers not more than six is connected with the fact that if the quantity of layers more than six, heat-exchange efficiency related to sealing agent will increase slightly, in particular, temperature gradient will change slightly and, accordingly, the further increasing of layers makes no sense.

It should be also noted that as it was mentioned above in an offered subject sealing media may be composed of liquid and gas phases, moreover the layers in sealing agent may be composed of liquid of similar or different density and viscosity, and may contain or not contain the layer with gas phase—the choice of sealing media depends on a designated task. One of the best options of an offered subject is above described case when the layers of sealing media, containing separately gas and liquid, interchange in a contact elastic, multilayered sealing agent; in case of such interchange of layers, optimum efficiency of control of elastic and heat exchange properties of system can be reached.

Claims

1. A downhole screw motor comprising a stator having an internal screw surface, a rotor placed inside a stator having external screw surface, the quantity of screw lobes of a rotor is one less than a stator, a sealing system, a spindle assembly is different in that as a sealing system the following system is used: a system, which contains a contact elastic, multilayered sealing agent rigidly connected either with a stator or with a rotor or contains two sealing agents, which separately rigidly connected one with a stator, the other with a rotor, moreover a tough straps (made of strong material, for example, metal) making layers in a sealing agent, have close ring-like shapes and are similar to the surface, to which they are fixed; the quantity of layers of a sealing agent is not more than six; in the layers separately gas and/or liquid is used as sealing media; a sealing system comprises, a separation joint of drilling mud flow, an electrogenerating turbine, a pumping unit for drill mud, regulating units of movement direction of sealing media and drill mud, a mud hopper, automatic control system and also, in accordance with applied sealing media, a tank-stabilizer with gas, a compressor, a heat exchanger for gas cooling and/or a tank-stabilizer with liquid, a pump, a heat exchanger for liquid cooling.