GB2038909A

GB2038909A - Improvements in and Relating to Drilling

Info

Publication number: GB2038909A
Application number: GB8000014A
Authority: GB
Original assignee: Compagnie Francaise des Petroles SA
Current assignee: Total Compagnie Francaise des Petroles SA
Priority date: 1979-01-05
Filing date: 1980-01-02
Publication date: 1980-07-30
Also published as: GB2038909B; FR2445887B1; FR2445887A1

Abstract

The present invention relates to drilling using a rotary drilling tool which is cooled and cleaned by low- pressure drilling sludge. In such a drilling process, a high- pressure rotary hydraulic jet is provided for dislocating the working face by causing the low-pressure drilling sludge F1 to drive a motor 5, 6 located near the working face and connected to drive a high-pressure pump 4, a fraction F3 of the low- pressure output F2, F3 of the motor 3 being supplied to the pump 4, the output of which provides the high- pressure hydraulic jet F5. <IMAGE>

Description

SPECIFICATION Improvements in and Relating to Drilling The present invention relates to drilling in which the actual cutting action provided by a rotary tool is combined with the action of a highpressure rotary hydraulic jet, the purpose of which is to dislocate the rock or other material in order to facilitate the attack thereof by the rotary tool.

Numerous attempts have already been made to increase the efficiency of drilling work by making use of the impact effects produced by liquid jets, in particular jets at very high pressure, acting on the working face at the same time as the actual cutting tool, for example a conventional rotary tool.

However, these attempts all ended in failure and were successively abandoned, either because of the prohibitive cost per metre drilled, or because of the technological difficulties encountered, in particular in the method of assembling the sets of drill pipes, it being necessary for each set to comprise two lines of concentric pipes, respectively conveying lowpressure sludge and the high-pressure liquid; a further cause of failure was the breakdown of the leaktight linings, which led to the appearance of leaks along the whole length of the set of drill pipes.

It has been observed that, in view of the high power and the high throughput involved, in particular the power of the pumps used for drilling purposes, which can easily be greater than 1,000 HP for a throughput of at least 2,000 litres/minute, the possible tapping of a small fraction of a throughput of such a magnitude would not have a great effect on the efficiency of the process or, in particular, on the cutting progress or on the result of washing the cutting tools.

According to one aspect of the present invention there is provided a drilling process using a rotary drilling tool for attacking a working face, comprising providing a flow of low-pressure fluid for cleaning and cooling said drilling tool, and providing a flow of high-pressure hydraulic fluid passing through said drilling tool for dislocating the working face, wherein said low-pressure fluid actuates a hydraulic motor located near the working face, the output of fluid from said motor being divided into a larger fraction which flows directly through said drilling tool for cleaning and cooling said drilling tool and a smaller fraction which flows to a high-pressure pump which is driven by said hydraulic motor, the fluid output from said pump flowing through said drilling tool for dislocating the working face.

According to another aspect of the present invention there is provided a device for use in carrying out the above method comprising a rotary drilling tool which is adapted to be mechanically driven from the surface and to be connected to a low-pressure pump located at the surface to receive a flow of low-pressure fluid, a hydraulic motor which is located near the working face and is connected to receive the flow of lowpressure fluid, a high pressure pump which is mechanically connected to said hydraulic motor, and passage means connected to the outlet of said motor and to the inlet of said pump for receiving a smaller fraction of the low-pressure fluid leaving said hydraulic motor, for receiving the output of said pump and connected to passages in said drilling tool, and connected to said outlet of said motor for receiving the larger fraction of the low-pressure fluid leaving said motor and connected to passages in said drilling tool.

In a preferred embodiment, a system for producing low-pressure drilling sludge is associated with a conventional drilling system of the rotary type. The first system comprises a powerful pump feeding a suitable hydraulic circuit which, near the cutting face, actuates a lowpressure hydraulic motor, such as, for example, an axial-flow turbine, or a helical-jet motor of the Moineau type, the output being divided, on leaving the hydraulic motor, into two branches, the larger of which is led directly towards the tool and passes through the latter via suitable passages or channels, whilst the other part, which constitutes only a small fraction of the overall throughput, is led towards a high-pressure forcing pump which can also be of the Moineau type with a helical jet.The high-pressure fluid leaving this pump is led towards the rotary tool and also passes through the latter via suitable passages or channels which are different from the above mentioned channels. Thus the major part of the throughput is used in a known manner in order to clean and cool the rotary tool. As regards the high-pressure jet leaving the high-pressure pump, it is directed through the passages in the tool onto the rock of the working face and contributes to the cracking and the dislocation of the latter, which greatly facilitates the cutting work of the rotary tool.

This results, in particular, in the creation of grooves for relieving stress, which correspondingly improves the progress of the work.

Furthermore, if is seen that the above described process permits integral use of the power available at the outlet of the high-pressure pump, because, in particular, any intermediate pressure loss is eliminated.

By way of example, it would be possible to consider a turbine having a power of about 400 HP on the shaft, which turbine drives a pump having an assumed efficiency of 50%, whereupon the pump has an output power of 200 HP, which could then produce a throughput of 90 litres/minutes, under a very high pressure of 700 bars, in the form of three jets each having a diameter of 1.5 mm.

Embodiments of the invention will now be -described, by way of example only, with reference to the accompanying drawings.

In the drawings: Figure 1 is a schematic vertical half-section through an embodiment of a device for use according to an embodiment of a process according to the invention, which section shows, in particular, the high-pressure and low-pressure hydraulic circuits; Figure 2 is a vertical half-section through another embodiment of a device for use according to an embodiment of a process according to the invention; Figure 3 is a vertical half-section through a modified embodiment of a device for use in accordance with an embodiment of a process according to the invention; and Figure 4 is a vertical section through an embodiment of a tool according to the invention.

Figure 1 shows the lining 1 of a conventional rotary drilling tool. Arrow F1 shows the direction of arrival of the drilling sludge which drives an hydraulic motor 3. The output of the motor 3 is divided into two parts, one of which is shown by arrow F2 and the other by arrow F3. The first part shown by the arrow F2, which is by far the larger part, is led directly towards the tool 2, passing through the tool in the direction of arrow F4 and leaving it through an orifice 8. The remaining fraction shown by the arrow F3 passes through a high-pressure pump 4, the output of which passes through the tool 2 in the direction of the arrow F5 and leaves it through an orifice 13.

Drive shaft 12 connects the hydraulic motor 3 to the high-pressure pump 4.

Figure 2 shows the lining 1 of a rotary drilling tool, on which lining the fixed blading 5 of an hydraulic motor, schematically represented by 3 in Figure 1, are mounted. The hydraulic motor, in this embodiment, is an axial-flow turbine of which the rotating blades are schematically represented by6.

The high-pressure pump, which is indicated by 4 in Figure 1, is in this embodiment an axial-flow multicellular pump of which the fixed blades are shown at 7 and the rotatable blades of the various stages are shown by 10. The main part F2 of the output of the hydraulic motor flows along path 9, the fraction F3 of the output passing through the pump and leaving it at 11. The high-pressure and low-pressure flows pass through the rotary tool 2 in the direction of the arrows F5 and F4 respectively, the high pressure flow leaving through outlet 13 and the low pressure flow leaving through outlet 8.

In Figure 3, both the hydraulic motor and the high-pressure pump are of the Moineau type with a helical jet. The paths of the various jets through the turbine and the pump, and also the respective circuits for passage through the rotary tool 2, are the same as described above.

The stator of the turbine is shown at 1 5, the rotor of the turbine at 1 6, the stator of the highpressure pump at 1 8 and the rotor of the highpressure pump at 1 9. The turbine drives the highpressure pump by shaft 1 7.

Figure 4 shows a preferred configuration of a rotary tool for use according to the present invention.

Starting from the central zone of the tool, which zone is reserved for the high-pressure fluid, the latter flows along passage 21 in the direction of the arrow F6 towards the high-pressure outlet orifice 24. The annular space 22 in the connector 2a, which space is approximately concentric with the central space in the tool, is reserved for the low-pressure fluid which enters the passage 23 and then divides, inside the tool 2, into 2 divergent passages in which the fluid flows in the direction of the arrows F7 and F8 and arrives, in the former case, in the central outlet zone 25 of the tool and, in the latter case, in the more off centre outlet zone 26.

The capacity which is intended to contain the high-pressure fluid is preferably in the central region of the connector 2a and of the tool 2 in order to avoid the need for rotating gaskets, which gaskets would be necessary if the opposite solution were adopted, namely if the central zone were reserved for the low-pressure fluid and a concentric annular capacity, located towards the periphery, were reserved for the high-pressure fluid.

It will be apparent that the present invention is not intended to be limited to the embodiments which hueen described above, but that modifications of detail can be applied to these embodiments without thereby going outside the ambit or scope of the invention.

Thus, in a simplified variant of the invention, the high-pressure forcing pump can be driven mechanically, directly from the surface. in the same spirit, it is possible to envisage driving the same high-pressure forcing pump by means of an electric motor coupled directly thereto, which motor is supplied with electrical energy from the surface.

Claims

1. A drilling process using a rotary drilling tool for attacking a working face, includes providing a flow of low-pressure fluid for cleaning and cooling said drilling tool, and providing a flow of highpressure hydraulic fluid passing through said drilling tool for dislocating the working face, wherein said low-pressure fluid actuates a hydraulic motor located near the working face, the output of fluid from said motor being divided into a larger fraction which flows directly through said drilling tool for cleaning and cooling said drilling tool and a smaller fraction which flows to a high-pressure pump which is driven by said hydraulic motor, the fluid output from said pump flowing through said drilling tool for dislocating the working face.

2. A device for carrying out the process according to claim 1, comprising a rotary drilling tool which is adapted to be mechanically driven from the surface and to be connected to a lowpressure pump located at the surface to receive a flow of low-pressure fluid, a hydraulic motor which is located near the working face and is connected to receive the flow of low-pressure fluid, a high-pressure pump which is mechanically connected to said hydraulic motor, and passage means connected to the outlet of said motor and to the inlet of said pump for receiving a smaller fraction of the low-pressure fluid leaving said hydraulic motor, for receiving the output of said pump and connected to passages in said drilling tool, and connected to said outlet of said motor for receiving the larger fraction of the lowpressure fluid leaving said motor and connected to passages in said drilling tool.

3. A device according to claim 2, wherein said passage means for receiving said smaller fraction of the low-pressure fluid passing to said pump are located centrally, and said passage means for receiving said larger fraction of the low-pressure fluid passing directly into said passages in the drilling tool are located peripherally.

4. A device according to either claim 2 or claim 3, wherein said hydraulic motor is an axial-flow turbine.

5. A device according to any one of claims 2 to 4, wherein said pump is an axial-flow multicellular pump.

6. A device according to either claim 2 or claim 3, wherein said hydraulic motor is a helicaldet turbine.

7. A device according to any one of claims 2, 3 and 6, wherein said pump is a helical-jet pump.

8. A device according to any one of claims 2 to 7, wherein said passages for low-pressure fluid divide the fluid so as to cause it to emerge axially bdth in a central region and in a peripheral region of said drilling tool, said passages for said highpressure fluid causing the fluid leaving the pump to emerge through a peripheral orifice in the drilling tool.

9. A drilling process substantially as herein described with reference to the accompanying drawings.

10. A drilling device substantially as herein described with reference to the accompanying drawings.