Patent Application
20120034113
This invention relates to the technology of drilled wells producing fluids which it is attractive to extract.
As these wells may be of very great depth—several thousand metres—a pumping mechanism capable of delivering well fluid under pressures of several hundred bars is required.
The depth of these wells gives rise to a high temperature of over 200—the pumping mechanism must be designed to withstand high temperatures.
The fluid delivered may be of very low viscosity, so the pumping mechanism must be capable of delivering a low viscosity fluid at high pressure (well depth).
According to the invention the mechanism for pumping well fluids capable of delivering a very hot fluid of very low viscosity at high pressure comprises the combination of a hydraulic pump and a hydraulic motor, the hydraulic motor driving the said pump, this combination being made possible through a rotating seal which is essential for proper functioning of the motor. The associated hydraulic pump and motor are located at the bottom of the well.
The fluids pumping device located at the bottom of drilled wells according to the invention is characterised in that it comprises a combination of a hydraulic pump and a hydraulic motor driving the said pump through the intermediary of a rotating seal which ensures a leaktight seal between the hydraulic motor and the hydraulic pump.
Depending upon the embodiment, the invention also comprises all or some of the following:
The invention will be better understood and other aims, details, characteristics and advantages thereof will be more clearly apparent in the course of the following description of various embodiments of the invention provided purely for illustration and without limitation with reference to the appended drawings.
In these drawings:
Space 1 within which the material which has to be pumped is located is at a temperature of the order of 200° or more and at a pressure of approximately 300 bar or more.
A hydraulic pump 10 designed to draw in fluid 2 and deliver it to the surface 3 is located in this bottom.
The viscosity of the fluid, its temperature and the pressure required to deliver the said fluid make it necessary to choose a pump technology capable of ensuring acceptable performance under these conditions. A piston pump fulfils these requirements.
Rotation of inclined plate 14 of pump 10 transmits movement to ball-race plate 12 bringing about alternating movement of pistons 11. Inclined plate 14 is caused to rotate by a shaft 41 (which will be described below) through the intermediary of a key 15. Inclined plate 14 is supported by ball races 16 in a leaktight enclosure 17 within which the mechanical components of pump 10 are housed.
A thrust plate 18 through which pistons 11 pass bears through washers 19 on the heads 11a of pistons 11. A spring 20 presses thrust plate 18 against the heads 11a of pistons 11 via a tapering block 21 which bears against the spherical head 18a of thrust plate 18.
Pistons 11 slide in openings 22 passing through a fixed barrel 23. Openings 22 open onto a fixed part 24 in which inlet openings 25 fitted with inlet valves 26 are provided in order to draw in fluid 2, and delivery openings 27 fitted with delivery valves 28 to deliver fluid 2 towards a delivery column 4 which opens at the surface 2.
Each piston 11 is fitted with at least one inlet valve 26 and one delivery valve 28 (
In order to protect delivery pump 10 from contaminants and impurities present in fluid 2, in particular on the inlet valve 26 side of pump 10, filters 29 are located on inlet openings 25 of the pump.
In order to ensure that the mechanical functioning of pump 10 is satisfactory a leaktight separation is made between hydraulic fluid 5 which lubricates the mechanical components of the pump and fluid 2 which has to be pumped.
In order to provide this seal, sealing segments 30, for example of the metal segments type, may be provided on the body of pistons 11 of the pump (
In order to recover any leaks of fluid 2 towards lubricating fluid 5 a low pressure seal 31 may be provided at the heads of the pistons, together with a drainage opening 32, fitted with a calibrated valve 33 and if appropriate a filter 34, to drain any leaks towards fluid 2.
The metal segments are chosen in such a way as to create the minimum possible compressibility on the fluid side. With the same concern, deadspace 35 between the free ends of pistons 11 of the pump and its valves and 28 will preferably be of minimum size. These arrangements are to be preferentially adopted so as to provide pump 10 with maximum compression power in relation to fluid 2 which has to be delivered.
As the fluid which has to be pumped may be contaminated, provision needs to be made to clear filters 29 which will become obstructed and render pump 10 inoperative.
For this purpose provision may for example be made (see
The internal space within enclosure 17 is entirely filled with lubricating hydraulic fluid 5.
In order to prevent fluid 2 entering lubricating fluid from the mechanical part of delivery pump 10, provision may be made for slightly pressurising lubricating fluid 5 by locating a piston accumulator 37 loaded by a spring 38 between fluid 2 and lubricating fluid 5 in an opening 36 passing through enclosure 17.
This piston 37 can also be used to compensate for temperature changes and changes in the flow from the pump, and thus to produce a compensated leaktight space 17. Piston 37 allows the volume of said space 17 to vary slightly to compensate for cyclical changes in flow and to place the enclosure at the same pressure as fluid 2. This compensation may also be performed by a leaktight membrane.
The piston pump is driven by a hydraulic motor.
In the embodiment illustrated in
The pressurised hydraulic fluid arrives via a pipe 46 and returns to motor/pump unit 6 through a pipe 47. Hydraulic motor 40, which is housed in an enclosure 48, is immersed in the return hydraulic fluid 42. The pipes connecting the hydraulic motor to motor/pump unit 6 are the normal inlet and outlet pipes for the feed openings for the hydraulic motor.
Pistons 43 are connected alternately to pipe 46 through which the pressurised fluid arrives and pipe 47 for return to the reservoir 9 of motor/pump unit 6 on the surface, through a flat plate glass distributor, which is not described in detail because it is well known and does not form part of the invention.
Rotating barrel 45 of hydraulic motor 40 is connected to rotating angled plate 14 by shaft 41.
There then arises the problem of providing a seal between hydraulic fluid 5 lubricating the mechanical part of the pump and hydraulic fluid 42 returned to hydraulic motor 40.
In fact there may be a significant pressure difference between the fluid in which the barrel of the hydraulic motor is immersed and the lubricating fluid for the pump.
This significant pressure difference raises the problem of providing a link between pump 10 and motor 40 which is both leaktight and rotating, and for this purpose shaft 41 passes through a seal 50, which is a rotating seal.
The technology of leaktight rotating seals is known, but in this case it has to operate at temperatures of the order of 200° C. with a pressure difference of at least the pressure obtaining in return line 47 from the hydraulic motor.
By way of example the invention provides two embodiments for rotating seal 50 (see
The two variants of rotating seals 50 provided have the property of creating small friction torques so as not to have an adverse effect on the performance of the transmission.
With this object, in the example in
Thrust member 51 is caused to bear against block 53 by means of a spring 52 located between the base of thrust member 51 and a shoulder 41a on shaft 41.
The spherical head of thrust member 51 rotates together with rotating shaft 30 through a key 55. The axis of rotation B of the spherical head is excentric in relation to the axis of rotation A of shaft 41. Because of this the spherical head rotates with shaft 41 and causes a displacement movement of block 53. This movement ensures that a hydrostatic film is present beneath block 53 and thus ensures that it operates satisfactorily.
Only the head of thrust member 51 is excentric, causing double tapering block 54 to rotate.
It will be seen in
These arrangements ensure that a slight high pressure leak towards the low pressure has the effect of preventing any possibility of fluid 2 entering within the hydraulic motor.
In order to prevent the risk of fluid 2 entering hydraulic motor 40 a slight high pressure leak towards the low pressure may be provided for.
With this object a slight leakage flow is provided in rotating seal 50, which passing through a non-return valve 60 communicates with space 1 containing fluid 2. Rotating seal 50 is designed so that any leaks flow in front of the radial seal at the end of the hydraulic pump. This flow is controlled to have a low pressure through non-return valve 60 which is slightly loaded by a spring.
Fluid 2 may be at 200° or more. Because of this the components of the motor and hydraulic pump assembly must work at high temperature and only fluid 2 can be regarded as being a heat exchange fluid.
In order to prevent too great a temperature difference between the interior of the assembly of pump 10-40 located in the well and said fluid 2 the exterior of enclosures 17 and 48 of the said assembly may be constructed in the form of a heat exchanger, for example with radial fins 17a (see
Although the invention has been described in connection with several particular embodiments, it is obvious that it is not in any way restricted thereby and that it comprises all technical equivalents of the means described, including combinations thereof if they fall within the scope of the invention.
The use of an indefinite article “a” for one component does not unless mentioned otherwise exclude the presence of a plurality of such components.
In the claims no reference numbers between brackets may be interpreted as a restriction of the claim.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1056478 | Aug 2010 | FR | national |
