EP3631155B1 - Facility for heating hydrocarbon extraction conduits - Google Patents

Description

The technical sector of the present invention is that of devices for heating hydrocarbon extraction conduits in a paraffinic or heavy crude oil well.

It is known to date to extract liquids from the ground, for example hydrocarbons, resting in underground deposits which may be several kilometers underground. After drilling a hole from the surface to the deposit where the liquid to be extracted is located, this hole is consolidated as the drilling progresses with pipes of decreasing diameter. All of these pipes constitute an envelope.

In the producing zone, towards the buried end, this casing is pierced with a certain number of orifices in order to provide access to the liquid. This pierced part is designated by the term strainer or drain according to its length. A pipe of constant diameter and smaller than that of the casing is introduced into the previous casing in order to reach the bottom of the borehole to pump the liquid to the surface. This pipe is therefore a pumping pipe. This pipe can be fitted with a downhole pump. The documents US8955591 , US2005072567 and WO2004020895 describe wells provided with pumping installations and pipelines for such wells.

A problem frequently encountered with certain oils lies in the deposition of paraffins or asphaltenes on the walls of the pipe for raising crude oil in the wells. These fractions tend to solidify all the more as the temperature drops. These fractions tend to settle in the oil rise pipe as mentioned above and then gradually block this pipe. It is then necessary, to continue the extraction, to carry out a so-called mechanical scraping operation in order to eliminate the paraffin accumulated in the pipe, which imposes a stoppage of production.

Depending on the wells, these production shutdowns must be carried out at frequencies ranging from once a week to several times a day for the most critical wells. These shutdowns lead to a decrease in overall production of Wells.

Another problem encountered in the case of heavy oils is the increase in pressure drops when the temperature of the oil decreases in the rise line to the surface. This may result in a decrease in the production rate of the well or the need to select a more powerful pump.

It is therefore observed that the high viscosity and the solid deposits lead to slowdowns in the production rate, which increases the cost of production per unit volume, which can lead to the closure of a well.

To solve this problem, a solution by supplying heat consists in arranging resistive or inductive electrical heating elements along the oil rise pipe. These elements can be installed either outside or inside the pipe. In the case of an outdoor installation, these electrical elements need to be installed against the wall of the pipe to promote heat exchange between the resistors and the pipe. The risk is to have a high temperature of the resistors. The problem then arises of choosing the material of these resistors as well as the connections.

Finally, for reasons of reliability, it is difficult to bring large quantities of electrical energy downhole.

The object of the present invention is to provide a heating system for the oil rise pipe in a well to prevent the deposition of paraffins or asphaltenes on the wall of the pipe during production, to dissolve these deposits which may have appeared in the oil lift pipe during a shutdown and before a restart of the well or maintain the viscosity of the oil at an acceptable level for the downhole pump.

The subject of the invention is therefore an installation for heating pipes for the extraction of hydrocarbons through a well connecting the surface to an extraction zone, comprising a substantially cylindrical pipe consolidating said drilling, means for extracting hydrocarbons and means for circulating a hot fluid from the surface towards the zone to be heated of the well, characterized in that the circulation means comprise in the pipe a first insulated heating pipe thermally injected from the surface of the hot fluid to the desired depth and a second heating pipe surrounding the first pipe to bring the hot fluid back to the surface and in that the extraction means comprise a pumping pipe surrounding the first and second heating pipes for the extraction of hydrocarbons.

According to one characteristic of the invention, the first and second heating pipes are connected at the surface to a hot fluid production station composed of a storage tank or expansion tank, a pump and a heater for ensuring continuous circulation of the hot fluid in said heating pipes with continuous control of the temperature and the flow rate.

The hot fluid leaving the heater circulates in the thermally insulated pipe as far as the end of the latter then rises to the surface between the thermally insulated pipe and the second heating pipe.

The expansion vessel accommodates the increase in volume of hot oil in the closed circuit and thus avoids any overpressure in the circuit.

According to yet another characteristic of the invention, the first heating pipe is open at its distal end and the second heating pipe is closed at its distal end by a transverse wall.

Advantageously, the first heating pipe is thermally insulated using a compression-resistant insulator, either by virtue of its properties of resistance to compression or by the addition of spacers regularly placed between the first and the second pipe. .

According to yet another characteristic of the invention, the pumping pipe is connected to an extraction unit surface.

Advantageously, the pumping pipeline is equipped with a downhole pump.

Advantageously again, the pumping pipe is open at its distal end and has perforations at least at its end part.

According to yet another characteristic of the invention, the first heating pipe consists of a first inner tube surrounded by a second concentric outer tube and an insulator housed in the space between the two tubes.

Advantageously, the insulation consists of a microporous material and in that a reduced pressure is established in the space between the two tubes.

Even more particularly, the reduced pressure between the two tubes of the first pipe is between 1 and 100 mbar.

According to yet another characteristic of the invention, the first heating pipe is provided with an electric heating wire placed against the internal wall of the internal tube.

An advantage of the invention resides in the production of a closed circuit allowing the supply of heat into the pumping pipe, up to its end in the well, before the downhole pump. The hot fluid can be chosen from the fluids used in heating installations, for example an industrial thermal oil or water.

The hot fluid leaving the heater circulates in the first heat-insulated pipe as far as the end of the latter then rises to the surface between the first heat-insulated pipe and the second heating pipe. During this rise, the heat energy contained in the hot fluid is dissipated by conducto-convection in the oil produced in the pumping pipe and in the pumping pipe itself.

The temperature of the hot fluid is maximum at the surface in heater outlet. The thermal losses and therefore the reduction in the temperature of the fluid are low during the descent into the thermally insulated pipe. During the rise of the hot fluid towards the surface, the heat exchanges with the pumping pipe are important to allow the exchange of heat and the temperature of the fluid drops sharply.

Thus, the heat is supplied to the pumping pipe and the crude oil produced in this pipe will maintain the temperature of the oil during the rise to the surface and prevent the appearance of paraffins or asphaltenes in the pumping pipe. The temperature at which paraffins appear can be between 25°C and 70°C depending on the hydrocarbons.

The closer the reservoir temperature is to this paraffin appearance temperature, the greater the risk of paraffin deposition on the walls of the pumping pipe. Some deposits have a temperature only a few degrees Celsius higher than the temperature at which paraffin appears. These cases require heating the oil in the pumping pipe near the bottom end of this pipe.

In the case of so-called heavy oil, this temperature maintenance makes it possible to maintain the viscosity of the oil at the same level as in the formation at the bottom of the well and thus limit the pressure drops in the pumping pipe.

Another advantage of the invention resides in the control of the heat supply at the level of the section of the pumping pipe to be heated, in order to maintain the temperature of the oil produced while ensuring continuity of production. The flow rate and temperature of the hot fluid are controlled at the surface and can vary depending on the minimum acceptable temperature for the oil in the pumping line.

Another advantage of the invention lies in the fact that there is no mixing of the hot fluid and the recovered hydrocarbons, thus allowing the elimination of a hydrocarbon separation station.

Another advantage of the invention lies in the absence of pollution of the deposit since the hot fluid does not contaminate this deposit.

Another advantage of the invention resides in the use of an industrial thermal oil as heat transfer fluid. The volume of oil required in the closed loop formed by the first and the second pipe is between 500 liters and 3000 liters. Such thermal oil, standard in the industry, will have a composition optimized to be heated to the desired temperature, typically 80°C or up to 200°C and will allow the use of surface equipment, pump and heater, standard in industry and less complex.

Indeed, heating a hydrocarbon mixture to temperatures of the order of 200°C runs the risk of creating solid deposits on the heating elements of the boiler which can lead to a reduction in the heating power or even a rise in temperature of the heating element concerned and its degradation. The method of heating a thermal oil will be simpler since the composition of the latter is uniform and it will be selected so as not to create deposits at the temperature envisaged.

Yet another advantage of the invention resides in the use of even polluting fluid. The installation according to the invention allows surface control and adjustment of the temperature of the hot fluid, of the injection rate of this hot fluid as a function of the need for heating in the pumping pipe. Thus, any accumulation of paraffin in the pipe at its vertical part and/or at its horizontal part is prevented or eliminated.

Another advantage of the invention is that after a modification of the wellhead, this installation is independent of the other standard production equipment of the well and can therefore be installed and removed according to the needs of the well, leaving this equipment in place. downhole and surface production standards.

Another advantage of the invention resides in the fact that the pipes allowing the closed-loop circulation of the hot fluid can be made from coiled piping known by the English term “coiled tubing”. The double-walled heat-insulated pipe can be produced from two coiled pipes and inserted into the second larger diameter pipe, which can be a coiled pipe as well. This triple pipe can be wrapped around a wheel for transport and installed in a single operation by a coiled tubing unit in the well. Specific parts are installed at each end of the coiled pipes to isolate or communicate the annular rings as required for closed loop circulation.

• la figure 1 illustre une installation de réchauffage de conduits d'extraction d'hydrocarbures selon l'invention, à partir d'un puits, et
• la figure 2 est une coupe selon AA de la figure 1,

Other characteristics, details and advantages of the invention will emerge more clearly from the detailed description given below by way of indication in relation to the drawings in which:

• the figure 1 illustrates an installation for heating pipes for extracting hydrocarbons according to the invention, from a well, and
• the picture 2 is a cut according to AA of the figure 1 ,

An oil well is most generally made up of two essential parts, an outer envelope (designated by the English term casing) responsible for consolidating the inner wall of the well in the ground and an internal pipe (designated by the English term tubing) allowing the rise of oil to the surface.

The invention will now be described in more detail noting that the figure 1 illustrates the entire vertical portion of the wellbore.

According to figure 1 , there is shown a substantially vertical crude oil extraction well comprising an outer part and a deep part corresponding to the well itself.

The heating installation 1 according to the invention therefore comprises a drilled vertical well 2 consolidated by a cylindrical metal pipe 3. This well is related with a deep deposit 12 in its extension.

This installation 1 for extracting hydrocarbons through the well 2 connects the surface to an extraction zone at the level of the deposit 12 located at the bottom of the well. It comprises the substantially cylindrical pipe 3 consolidating said drilling, means 4 for extracting hydrocarbons and means 5 making it possible to circulate a hot fluid in a closed loop from the surface towards the section of the pipe 7 to be heated from the well 2 then again on the surface.

In the metal pipe 3, there is a pipe 7 for pumping hydrocarbons to the surface and heating pipes 8 and 11 allowing a hot fluid to circulate from the surface and along the section of the pumping pipe to be heated. .

The extraction means 4 therefore consist of an extraction unit 6 comprising the pumping pipe 7 connecting this unit to the hydrocarbon deposit up to the level of the deep deposit 12 and a downhole pump (not represented) for the extraction of hydrocarbons.

The closed-loop circulation means 5 comprise, in line 3, a first heat-insulated heating pipe 8 for injecting hot fluid from the surface to the deposit. This heating pipe 8 is connected to a unit 9 for heating and injecting hot fluid continuously, for example using a pump 10.

This first heating pipe 8 is surrounded by a second heating pipe 11 to bring the hot fluid back to the unit 9. The heating pipes 8 and 11 constitute with the unit 9 for the production of hot fluid a closed circulation circuit in flow of this hot fluid. The hot fluid production unit 9 consists of a storage tank 22 or expansion tank, a pump 10 and a heater 23 to ensure continuous circulation of the hot fluid in said heating pipes with continuous temperature and flow control.

The hot fluid circuit is closed at the level of the distal end of the second pipe 11 by a transverse wall 18 while the first pipe 8 is open at its distal end 17. of it.

The length of the pipes 8 and 11 in the casing 3 is a function of the zone in which the paraffins accumulate against the wall of the pipe 7. This zone is generally located in the upper part of the pipe which is the zone at the level at which the hydrocarbons have undergone significant cooling. This zone is generally located from the surface to the depth at which the paraffin deposits appear, ie 200 to 2000 meters deep.

Thus, the hot fluid is injected by the pump 10 into the pipe 8 as far as its distal end 17, then this hot fluid rises towards the unit 9 via the pipe 11. It is therefore easy to control the temperature of the hot fluid leaving the heater 23 and the necessary flow rate of the pump 10.

In the figure, it can still be seen that the pipes 8 and 11 are inserted in their vertical part into the pipe 7 for extracting the hydrocarbons.

On the figure 2 , an AA section of the figure 1 on which the casing 3 has been taken up. In this casing, there is the extraction pipe 7 surrounding the heating pipes 8 and 11. The first pipe 8 consists of a first internal tube 16 surrounded by a second tube external concentric 17 and an insulator 20 housed in the space between these two tubes.

It goes without saying that the various elements illustrated on the figure 1 and 2 are not to scale and are shown for illustrative purposes only.

Insulator 20 may be a powder material commonly used in this field. To reinforce the thermal insulation of the pipe 8, the free or annular space delimited between the two tubes 16 and 17 is subjected to a reduced pressure. This reduced pressure can be between 101.3 and 10000.8 Pa (1 and 100 mbar).

Since it is a closed circulation circuit, the hydrocarbons are not contaminated by the fluid used.

The fact of using a hot fluid confers a double action. The heat makes it possible to prevent the appearance and deposit of solid fractions such as paraffins and asphaltenes and to melt the fractions already solidified or deposited during a restart of the well, for example.

In the case of a heavy oil, the heat acts by maintaining the viscosity of the hydrocarbons as in the tank. Thus, with the same pumping power, a larger quantity of liquid will be extracted contributing to the improvement of productivity.

The depth of the well being able to reach several hundreds of meters (100 to 2000 m), it is essential to bring heat to the level of the deposit, to have a pipe 8 highly thermally insulated.

A thermally insulated pipe 8 has been provided. Line 8 is made using the technique known as “pipe in pipe”. Between the two tubes 16 and 17 is placed the insulator 20 as explained above.

The first tube 16, internal, ensures the transport of the hot fluid. This tube 16 is mechanically protected by the second tube 17 of larger diameter concentric with this first tube 16 and thermally by the insulator 20.

Several possibilities are offered for producing an insulator between the two tubes 16 and 17. It is advantageous to provide an insulator 20 resistant to crushing, acting as a spacer, either by its properties of resistance to compression or by the regular addition spacers between the first and the second pipe, to prevent the two tubes 16 and 17 from coming into contact with one another. A microporous material can be used as insulation between tubes 16 and 17.

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

Such a compressed microporous material advantageously has a density of between 180 and 400 kg/m ³ . The insulating thermal capacities of such a material are markedly improved when it is placed in the ring finger under low pressure between the two tubes 16 and 17.

It is also possible to produce an insulator 20 by providing a multilayer super-insulator consisting of reflective screens interposing layers of powder as described in the patent FR-2862122 . The screens consist of a reflective sheet, for example of aluminum, on which the powder is deposited, wound in a spiral on itself.

The powder has a particle size substantially equal to 40 μm, pores whose size is of the order of magnitude of the mean free path of the molecules of the gas in which this powder is placed and a density of between 50 and 150 kg/m ³ . The insulating thermal capacities of such a material are markedly improved when it is placed in the ring finger under low pressure between the two tubes 16 and 17, between 10 ^-2 and 1 mbar

This insulation, not having sufficient compressive strength properties, requires the addition of spacers regularly between the tubes 16 and 17. The material used to make these spacers must exhibit good insulating behavior. Such a material can advantageously be a microporous material as described above.

The heating pipe 8 as previously described in relation to the figure 1 and 2 allows a sufficient heat input to make the hydrocarbons sufficiently fluid with a boiler of 5 to 500 KW.

The installation 1 according to the invention makes it possible to ensure continuous operation and to avoid the appearance of deposits on the pumping pipe. This makes it possible to increase the production of crude oil by 20 to 100% and to avoid any pollution of the deposits.

By way of indication, a pipe 8 according to the invention may consist of an outer tube 17 of 33 mm outside diameter with a thickness of 2 mm and a tube internal 16 of 13 mm outer diameter with a thickness of 2 mm and is suitable for transporting 20 kW at 200 ° C over an overall distance of 1000 meters.

As a further indication, a pipeline 8 consisting of an outer tube 17 60 mm in diameter and 5 mm thick and an inner tube 16 33 mm in outer diameter and 4 mm thick will easily transport 200 kW to 200°C over an overall distance of 2000 meters.

The length of pipes 8 and 11 depends on the section of pipe 7 in which the paraffins accumulate against the wall. This section is generally located in the upper section of the pipe which is the zone at the level of which the hydrocarbons have undergone significant cooling but can also propagate at depth. This section is generally located over a distance between the surface and 100 to 2000 m depth.

In the case of heavy oil, the length of pipes 8 and 11 can also vary from the surface to the end of pipe 7 depending on the power required to be supplied to maintain the temperature of the oil produced.

In the case where there is no downhole pump, the pipes 8 and 11 can extend beyond the end of the pipe 7, in the casing 3 to have a thermal action on the perforations of the strainer or drain, at the end of the casing 3 as well as on the deposit.

Thus, the hot fluid is injected by the pump 10 into the pipe 8 as far as its distal end 17, then this hot fluid rises towards the unit 9 via the pipe 11. It is therefore easy to control the temperature hot fluid and the required pump flow 10.

On the figure 1 and 2 , it can also be seen that the heating pipes 8 and 11 are inserted in their vertical part into the pipe 7 for pumping the hydrocarbons.

Claims (8)

1. A heating installation (1) for hydrocarbon extraction tubing via a well (2) linking the surface to an extraction zone (12), comprising a substantially cylindrical casing (3) consolidating said drill hole, a hydrocarbon extraction means (4) and means (5) to enable a hot fluid to be made to circulate from the surface to the well (2) zone to be heated, wherein the circulation means (5) comprise in the casing (3) a first thermally insulated heating tubing (8) open at its distal end (17) to inject the hot fluid from the surface to the required depth and a second heating tubing (11) closed at its distal end by a transversal wall (18) and surrounding the first tubing (8) to bring the hot fluid towards the surface and wherein the extraction means (4) comprise a pumping tubing (7) surrounding the first and second heating tubing (8, 11) for the extraction of hydrocarbons, characterised in that the first heating tubing (8) is constituted by a first inner pipe (16) surrounded by a second concentric outer pipe (17) and an insulation (20) housed in the space between the two pipes and in that the first heating tubing (8) is fitted with an electric heating wire (21) arranged against the inner wall of the inner pipe (16).
2. A heating installation (1) according to Claim 1, wherein the first (8) and second (11) heating tubing are connected on the surface to a hot fluid production unit (9) composed of a storage tank (22) or an expansion tank, of a pump (10) and of a heater (23) to ensure a continuous circulation of the hot fluid in said heating tubing (8, 11).
3. A heating installation (1) according to any one of Claims 1 or 2, wherein the first heating tubing (8) is thermally insulated using a compression-resistant insulation (20).
4. A heating installation (1) according to any one of Claims 1 to 3, wherein the pumping tubing (7) is connected to a surface extraction unit (6).
5. A heating installation (1) according to Claim 4, wherein the pumping tubing (7) is open at its distal end and equipped with a well-bottom pump.
6. A heating installation (1) according any one of the above claims, wherein the insulation (21) is constituted by a microporous material and where in a reduced pressure is established in the space between the two pipes (16, 17).
7. A heating installation (1) according to Claim 6, wherein the reduced pressure between the two pipes (16, 17) of the first tubing (8) is of between 1 and 100 mbar.
8. A heating installation (1) according to any one of the above Claims, wherein the hot fluid is an industrial thermal oil or water.

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