INSTALLATION OF HEATING FOR HYDROCARBON EXTRACTION PIPES

Abstract

A heating installation for hydrocarbon extraction pipes via a well linking the surface to an extraction zone, including a substantially cylindrical casing consolidating the drill hole, a hydrocarbon extraction method and method to enable a hot fluid to be made to circulate from the surface to the well zone to be heated. The injection method includes in the casing first thermally insulated heating tubing to inject the hot fluid from the surface to the required depth and second heating tubing surrounding the first tubing to bring the hot fluid towards the surface and the extraction method includes a pumping tubing surrounding the first and second heating tubing for the extraction of hydrocarbons.

Claims

1. A heating installation for hydrocarbon extraction tubing via a well linking the surface to an extraction zone, comprising a substantially cylindrical casing consolidating said drill hole, a hydrocarbon extraction means and means to enable a hot fluid to be made to circulate from the surface to the well zone to be heated, wherein the circulation means comprise in the casing a first thermally insulated heating tubing to inject the hot fluid from the surface to the required depth and a second heating tubing surrounding the first tubing to bring the hot fluid towards the surface and where in the extraction means comprise a pumping tubing surrounding the first and second heating tubing for the extraction of hydrocarbons.

2. The heating installation according to claim 1, wherein the first and second heating tubing are connected on the surface to a hot fluid production unit composed of a storage tank or an expansion tank, a pump and a heater to ensure a continuous circulation of the hot fluid in said heating tubing.

3. The heating installation according to claim 1, wherein the first heating tubing is open at its distal end and the second heating tubing is closed at its distal end by a transversal wall.

4. The heating installation according to claim 1, wherein the first heating tubing is thermally insulated using a compression-resistant insulation.

5. The heating installation according to claim 1, wherein the pumping tubing is connected to a surface extraction unit.

6. The heating installation according to claim 5, wherein the pumping tubing is open at its distal end and equipped with a well-bottom pump.

7. The heating installation according to claim 1, wherein the first heating tubing is constituted by a first inner pipe surrounded by a second concentric outer pipe and by an insulation housed in the space between the two pipes.

8. The heating installation according to claim 7, wherein the insulation is constituted by a microporous material and where in a reduced pressure is established in the space between the two pipes.

9. The heating installation according to claim 8, wherein the reduced pressure between the two pipes of the first tubing is of between 1 and 100 mbar.

10. The heating installation according to claim 7, wherein the first heating tubing is fitted with an electric heating wire arranged against the inner wall of the inner pipe.

11. The heating installation according to claim 1, wherein the hot fluid is an industrial thermal oil or water.

Description

[0038] Other characteristics, particulars and advantages of the invention will become more apparent from the detailed description given hereafter by way of illustration and with reference to the drawings, in which:

[0039] FIG. 1 shows a hydrocarbon extraction tubing heating installation according to the invention, on a well, and

[0040] FIG. 2 is a section view along AA in FIG. 1.

[0041] An oil well is generally constituted by two essential parts, an external envelope, called casing, intended to consolidate the inner wall of the well in the ground and an inner pipe, called tubing, enabling the oil to be brought up to the surface.

[0042] The invention will now be described in greater detail, noting that FIG. 1 illustrates all the vertical part of the drilling well.

[0043] FIG. 1 shows a substantially vertical crude oil extraction well incorporating an external part and a part at depth corresponding to the actual well.

[0044] The installation of heating 1 according to the invention thus incorporates a vertical drilled well 2 consolidated by a cylindrical metallic pipe 3. The well, in its extension, is linked to a deep reservoir 12.

[0045] This hydrocarbon extraction installation 1 via a well 2 links the surface to an extraction zone in a reservoir 12 located at the well bottom. It comprises the substantially cylindrical casing 3 consolidating said drilling, means 4 to extract the hydrocarbons and means 5 to enable a hot fluid to be circulated in a closed loop from the surface to the section of tubing 7 of the well 2 to be heated then back to the surface.

[0046] In the metallic casing 3, tubing 7 is positioned to pump hydrocarbons to the surface and heating tubing 8 and 11 is arranged enabling a hot fluid to be circulated from the surface along the section of pumping tubing to be heated.

[0047] The extraction means 4 are thus constituted by an extraction unit 6 incorporating the pumping tubing 7 linking this unit to the hydrocarbon reservoir at a deep reservoir level 12 and a well-bottom pump (not shown) for the extraction of the hydrocarbons.

[0048] The closed loop circulation means 5 comprise in casing 3 a first thermally insulated heating tubing 8 to inject hot fluid from the surface towards the reservoir. This heating tubing 8 is connected to a unit 9 to continuously heat and inject the hot fluid, for example using a pump 10.

[0049] This first heating tubing 8 is surrounded by a second heating tubing 11 to bring back the hot fluid towards the unit 9. The heating tubing 8 and 11 with the hot fluid production unit 9 constitute a continuous flow closed loop for this hot fluid. The hot fluid production unit 9 is constituted by a storage tank or expansion tank 22, a pump 10 and a heater 23 to ensure the continuous flow of the hot fluid in said heating tubing with a continuous control of the temperature and flow rate.

[0050] The hot fluid circuit is closed at the distal end of the second tubing 11 by a transversal wall 18 whereas the first tubing 8 is open at its distal end 17. The Figure shows that the distal end 17 opens out in the vicinity of the wall 18 and at a distance from it.

[0051] The length of tubing 8 and 11 in casing 3 depends on the zone in which the paraffin builds up against the wall of tubing 7. This zone is generally located at the upper part of the tubing which is the zone in which the hydrocarbons have suffered the most cooling. This zone is generally located from the surface to the depth at which the paraffin deposits appear, which is from 200 to 2,000 metres in depth.

[0052] Thus, the hot fluid is injected by the pump 10 in tubing 8 up to its distal end 17, then this hot fluid rises back up to the unit 9 by means of tubing 11. It is thus easy to control the temperature of the hot fluid leaving the heater 23 and the necessary flow of the pump 10.

[0053] The Figure also shows that tubing 8 and 11 are inserted in their vertical part into the hydrocarbon extraction tubing 7.

[0054] FIG. 2 shows a section along AA in FIG. 1 which shows the casing 3. In this casing, there is the extraction tubing 7 surrounding the heating tubing 8 and 11. The first tubing 8 is constituted by a first inner pipe 16 surrounded by a second concentric outer pipe 17 and by an insulation 20 arranged in the space between these two pipes.

[0055] It goes without saying that the different elements shown in FIGS. 1 and 2 are not drawn to scale and are only shown by way of illustration.

[0056] The insulation 20 may be a powder material commonly used in this type of domain. To reinforce the thermal insulation of the tubing 8, the free space or annulus delimited between the two pipes 16 and 17 is subjected to reduced pressure. This reduced pressure can be of between 1 and 100 mbar.

[0057] Given that this is a closed flow loop, the hydrocarbons do not become contaminated by the fluid used.

[0058] The fact of using a hot fluid has a two-fold effect. The heat prevents the appearance and depositing of solid fractions such as paraffin and asphaltene and also melts the fractions that have already solidified or been deposited during the restarting of a well, for example.

[0059] In the case of a heavy oil, the heat acts by maintaining the viscosity of the hydrocarbons as in the reservoir. Thus, for the same pumping power, a greater quantity of liquid will be extracted thereby contributing to an improvement in productivity.

[0060] Since the well may reach several hundred metres in depth (100 to 2,000 m), in order for heat to reach the reservoir level, it is essential for highly thermally insulated tubing heat to be used.

[0061] Thermally insulated tubing 8 is provided. The tubing 8 is made using the technique known as pipe-in-pipe. Between the two pipes 16 and 17, insulating material is arranged as described previously.

[0062] The first pipe 16 and the inner pipe ensure the circulation of the hot fluid. This pipe 16 is mechanically protected by the second pipe 17, of larger diameter, concentric to the first pipe 16, and thermally by the insulation 20.

[0063] There are several possibilities to provide insulation between pipes 16 and 17. It is advantageous to provide crush-resistant insulation 20 that acts as a spacer, either because of its compressive strength or by the regular addition of spacers between the first and second tubing, to prevent the two pipes 16 and 17 from coming into contact with one another. A microporous material may be used as insulation between pipes 16 and 17.

[0064] This microporous material, of the type described in patent FR-2746891, is advantageously obtained by compressing a powder, for example fumed silica.

[0065] Such a compressed microporous material advantageously has a density of between 180 and 400 kg/m.sup.3. The thermal insulating capacities of such a material are significantly improved when it is placed at low pressure in the annulus between the two pipes 16 and 17.

[0066] Insulation 20 may also be made by providing a multi-layer super-insulation constituted by reflective screens separated by layers of powder, such as described in patent FR-2862122. The screens are constituted by a reflective sheet, for example aluminium, onto which the powder is deposited, coiled in a spiral around itself.

[0067] The powder has a granulometry substantially equal to 40 m, pores whose size is in the order of magnitude of the mean free path of the gas molecules in which this powder is placed and a density of between 50 and 150 kg/m.sup.3. The thermal insulating capacities of such a material are significantly improved when it is placed at low pressure, between 10.sup.2 and 1 mbar, in the annulus between the two pipes 16 and 17.

[0068] This insulation, as it does not have sufficient compressive strength properties, requires the addition of spacers regularly positioned between pipes 16 and 17. The material used for these spacers must have good insulating properties. Such a material may advantageously be a microporous material such as that described above.

[0069] The heating tubing 8 as described previously with reference to FIGS. 1 and 2 enables sufficient heat to be provided to make the hydrocarbons sufficiently fluid using a boiler of 5 to 500 KW.

[0070] The installation 1 according to the invention enables continuous operation to be ensured and avoids the appearance of deposits on the pumping tubing. This enables the crude oil production to be increased by 20 to 100% and avoids any pollution of the reservoirs.

[0071] By way of illustration, tubing 8 according to the invention may be constituted by an outer pipe 17 with an outer diameter of 33 mm, a thickness of 2 mm, and an inner pipe 16 with an outer diameter of 13 mm and a thickness of 2 mm and is able to transport 20 kW at 200 C. for an overall distance of 1,000 metres.

[0072] Again by way of illustration, tubing 8 constituted by an outer pipe 17 with a diameter of 60 mm and a thickness of 5 mm and an inner pipe 16 with an outer diameter of 33 mm and a thickness of 4 mm will easily transport 200 kW at 200 C. for an overall distance of 2,000 metres.

[0073] The length of tubing 8 and 11 depending on the section of the tubing 7 in which the paraffin builds up against the wall. This section is generally located in the upper section of the tubing which is the zone at which the hydrocarbons have been subjected to significant cooling but may also propagate at depth. This section is generally located over a distance of between the surface and a depth of 100 to 2,000 m.

[0074] In the case of heavy oil, the length of tubing 8 and 11 may also vary from the surface to the end of the tubing 7 depending on the power that is required to maintain the temperature of the petrol produced.

[0075] In the case where there is no well-bottom pump, tubing 8 and 11 may extend beyond the end of tubing 7, in casing 3, in order to have an action on the screen or drain, at the end of casing 3 as well as on the reservoir.

[0076] Thus, the hot fluid is injected by the pump 10 in tubing 8 up to its distal end 17, then this hot fluid returns to the unit 9 by means of tubing 11. It is thus easy to control the temperature of the hot fluid and the required flow rate of the pump 10.

[0077] In FIGS. 1 and 2, heating tubing 8 and 11 can be seen to be inserted in their vertical part in the hydrocarbon pumping tubing 7.