FR3066777A1 - INSTALLATION FOR HEATING THE PRODUCTION AREA OF A WELL SINK FOR THE EXTRACTION OF HYDROCARBONS - Google Patents

Abstract

The invention relates to a heating plant (1) for producing the reservoir (12) of a well for extracting hydrocarbons through a well (2) connecting the surface to this deposit, comprising an envelope (3). ) substantially cylindrical consolidating said drilling and hydrocarbon extraction means (4) and means for injecting the hot fluid from the surface to the deposit. This installation comprises through the well (2) a first pipe (8) insulated thermally injection from the surface of the hot fluid to the deposit, a second pipe (11) surrounding the first pipe (8) to bring the hot fluid to the surface and a third hydrocarbon extraction pipe (7) independent of the first and second pipes (8, 11), said pipes extending from the surface to the reservoir.

Description

The technical sector of the present invention is that of installations for heating the deposit of a well for the extraction of hydrocarbons present in the geological deposits.

It is known to date to extract liquids from the ground, for example hydrocarbons, lying in underground deposits which can be found several kilometers in the ground. After drilling a hole from the surface to the deposit where the liquid to be extracted is located, this hole is consolidated as and when drilling with pipes of declining diameter. All of these pipes constitute an envelope. In the producing area, towards the buried end, this envelope 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 envelope is introduced into the preceding envelope in order to reach the bottom of the borehole to pump the liquid to the surface. This pipe is therefore an extraction pipe. This pipe can be fitted with a downhole pump.

A frequently encountered problem is the low value of the absolute or total flow of the wellbore. This flow is linked to several factors, but it is essentially the viscosity of the extracted liquid that is the problem. This liquid is all the more viscous the lower its temperature. Depending on the composition of the liquids to be extracted, another problem may appear. In the case of a liquid containing fractions which can solidify, for example paraffins or asphaltenes, these fractions tend to solidify and this all the more as the temperature drops. These fractions tend to settle and then gradually close off the orifices in the producing area, at the level of the envelope, and in the deposit itself in the vicinity of the envelope.

It is therefore found that the high viscosity and the solid deposits lead to slowing down of said flow rate, which increases the cost of production per unit of volume, which can lead to the closure of a well.

In order to remedy this problem, several solutions have already been proposed. Reference may be made, for example, to patents US-2757738 and US-4344485.

One solution is to inject a solvent for heavy fractions into the reservoir area. One drawback is the need to plan the logistics around this solvent: supply, storage, etc. Another drawback is that the chemical action of the solvent only affects certain fractions.

Another solution using heat is to have a heater at the bottom of the well in the drain. This heater is advantageously an electrical resistance. The difficult diffusion of this thermal power generates very high temperatures. Problems arise in the choice of materials, both for strength and for the end of the casing and / or of the extraction pipe. Given its location at the bottom of the well, it is difficult to produce such a reliable and easily maintainable resistance. Finally, for safety reasons, it is difficult to bring large amounts of electrical energy to the bottom of the well, typically 100 to 500 kW.

Another solution is to inject pressurized steam through the extraction pipe. Several drawbacks are linked to this method. Considering the long length of a well, which can reach several kilometers, it is difficult to guarantee that the steam arrives hot at the bottom of the well. In addition, the use of the extraction pipe for this use requires a complete stop of production during this phase. This method has the drawbacks of discontinuous production (known by the English term Huff n 'Puff).

It is known that injecting heat into an oil well promotes flow from the producing rock and through the strainer or drain. Heat acts in two ways: it decreases the viscosity of crude petroleum thus promoting its flow and it prevents the formation of deposits, paraffins and asphaltenes, or even melts them if deposits prior to the injection of heat existed.

Heat-acting methods have a double effect. They act on the deposits and on the fluidity of the heated liquid, thus increasing the extractable flow and the efficiency of extraction.

Finally, mention may also be made of patent FR-2881788 which describes a device in which a hot fluid is made to circulate in order to locally bring the rock to a higher temperature potential by conduction to fluidize the hydrocarbons, by means of a pipe. insulated. The hot fluid is recovered as a mixture with the hydrocarbons. The disadvantage of this device is that the hot fluid is mixed with the hydrocarbons extracted at the level of the producing zone and thus the flow which will have to accept the downhole pump will have to be increased by a factor of 5 to 30 depending on the flow of circulation and increased production from the well.

In the case where the heat transfer fluid is water, it is then necessary to separate the mixture thus formed on the surface.

Another drawback of this device in the case where the fluid heated at the surface is the fluid extracted from the well, is that the boiler required to heat this fluid will have to be sized to heat a mixture of hydrocarbons containing heavy elements and a portion of water also. The sizing of the boiler will therefore be more complex and the boiler more expensive. For example, the heating elements of the boiler must have a lower power density than for heating a thermal oil. The maintenance of a boiler heating a mixture of heavy hydrocarbons requires controlling deposits that may appear on the heating elements.

The aim of the present invention is to provide a system for improving the productivity of a well and increasing the recoverable reserves by adding heat to the reservoir at the level of the producing area of the well deposit by separating the heat transfer fluid and the extracted hydrocarbons. The subject of the invention is therefore an installation for heating the zone producing a well deposit for the extraction of hydrocarbons through the well connecting the surface to a deposit, comprising a substantially cylindrical envelope consolidating said well and a means for extracting hydrocarbons housed inside said envelope and means making it possible to circulate a hot heat-transfer fluid from the surface to the deposit, characterized in that it comprises through the well a first pipe thermally insulated from injection from the surface of the hot fluid to the deposit, a second pipe surrounding the first pipe to bring the hot fluid to the surface and a third hydrocarbon extraction pipe independent of the first and second pipes, said pipes extending from the surface to the deposit.

The surface equipment consists of a tank or an expansion tank, a pump and a heater. The hot fluid leaving the heater circulates in the thermally insulated pipe to the end of the latter then rises to the surface between the thermally insulated pipe and the second heating pipe.

According to a characteristic of the invention, the first and second pipes are connected to a hot fluid production station provided with a storage tank or expansion tank, a pump and a heater to ensure circulation in continuous hot fluid in said pipes.

According to another characteristic of the invention, the first pipe is open at its distal end and the second pipe is closed at its distal end.

According to yet another characteristic of the invention, the first pipe is thermally insulated using a compression-resistant insulation, either by its compressive strength properties or by the addition of spacers regularly between the first and the second pipeline.

Advantageously, the third pipe is connected to an extraction unit to bring up the surface of the hydrocarbons produced in the strainer or drain.

According to yet another characteristic of the invention, the third pipe is open at its distal end and fitted with a downhole pump.

According to yet another characteristic of the invention, the first pipe consists of a first internal tube surrounded by a second concentric external tube and a thermal insulator housed in the space between the two tubes.

Advantageously, the thermal insulator is a microporous material and a reduced pressure is established in the space between the two tubes.

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

According to yet another characteristic of the invention, the heat transfer fluid for heating the deposit is an industrial thermal oil. The invention also relates to the application of the closed loop circulation installation to the preheating in a closed circuit of a deposit chronologically upstream of the hydrocarbon extraction phase.

An advantage of the invention lies in the production of a closed circuit allowing the supply of heat to the bottom of the well. Thus, heat is provided both on paraffins, asphaltenes or bitumen agglomerates that it melts, and on the liquid that it heats up at the bottom of the well.

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.

Yet another advantage of the invention lies in the use of even polluting fluid.

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 thermally insulated pipe up to the end of the latter then rises to the surface between the first thermally insulated pipe and the second heating pipe. During this ascent, the heat energy contained in the hot fluid is dissipated by conducto-convection in the oil produced in the drain and in the deposit itself.

The temperature of the hot fluid is maximum at the surface at the outlet of the heater. The heat losses and therefore the decrease in the temperature of the fluid are low during the descent into the thermally insulated pipe. When the hot fluid rises to the surface, heat exchanges with the oil produced in the drain are important to allow heat exchange and the temperature of the fluid decreases sharply.

An advantage of the invention lies in the possibility of using an industrial thermal oil as heat transfer fluid. The volume of oil required in the closed loop formed by the first and second pipes is between 500 liters to 3000 liters. Such a thermal oil, standard in the industry, will have a composition optimized to be heated to the desired temperature, typically 200 ° C or up to 300 ° C and will allow the use of surface equipment, pump and heater, standard in industry and less complex.

Indeed, heating a mixture of hydrocarbons to temperatures of the order of 200 ° C has 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 the rise in temperature of the heating element concerned and its degradation. The method of heating a thermal oil will be simpler since its composition is uniform and it will be selected so as not to create deposits at the envisaged temperature.

Another advantage of the invention is that the amount of water contained in the hydrocarbon produced no longer influences the design of the heater. If water is present in the oil to be heated, from 0 to more than 90%, the heater will have to bring more energy to raise the temperature of the mixture by the same value and if steam appears, the heat exchanger efficiency drops.

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

Another advantage of the invention lies in the fact that the pipes allowing the closed-loop circulation of the hot fluid can be made from coiled pipes known under the term “coiled tubing”. The thermally insulated double-walled pipe can be produced from two “coiled tubing” and inserted into the second pipe of larger diameter, which can also be a coiled tubing. This triple pipe can be wound around a “coiled tubing” wheel for transport and installed in a single operation by a “coiled tubing” unit in the well. Special pieces are installed at each end of the coiled tubing to isolate or make the annulars communicate as required by closed-loop circulation.

Another configuration of this invention is the use of this circulation in a closed circuit to preheat a deposit chronologically upstream of the hydrocarbon extraction phase. Such preheating is necessary for certain methods of recovering heavy hydrocarbons such as the SAGD process (Steam-Assisted Gravity Drainage). In this configuration, there is no third line for raising the hydrocarbons; this is a preheating phase of the deposit only. An advantage of this configuration is that this preheating can be carried out with moving surface equipment using a thermal oil at high temperature, 200 ° C or more. This preheating configuration can advantageously replace preheating by steam injection for reasons of cost and scheduling of operations on an oil field. 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: - Figure 1 illustrates the upper part of an installation according to the invention , - Figure 2 is a section made at the level of the hydrocarbon deposit, - Figure 3 is a section along AA of Figure 1, and - Figure 4 is a section along BB of Figure 2.

An oil well is most generally made up of two essential parts, an external pipe (designated by the English term casing) responsible for consolidating the external wall of the well in the ground and an internal pipe (designated by the English term tubing) allowing the rise of oil on the surface. A strainer or drain performs two functions: it filters the extracted crude oil which rises to the surface and it prevents the hole drilled in the producing area from collapsing. Different manual and automatic valves ensure the seals and safety of the well vis-à-vis the outside. For more precision, reference may be made to patent FR-2881788 which illustrates the conditions for producing a well by providing heat. The invention will now be described in more detail, noting that FIG. 1 illustrates the upper and outer part of the wellbore and FIG. 2 the deep part where the hydrocarbons to be extracted are found. As indicated above, this involves heating the producing area of the deposit of a well in order to extract the hydrocarbons still present in the deposit.

According to Figure 1, there is partially shown the upper part of the heating installation 1 of extraction pipes according to the invention in which the vertical drilled well 2 is consolidated by a cylindrical metal casing 3. This well is in relation to a deposit as will be explained below. In the metal casing 3, a means 4 for extracting hydrocarbons is introduced on the surface and inside said casing 3 and means 5 making it possible to circulate a hot fluid from the surface to the deposit to be heated and then to new on the surface.

The extraction means 4 consist of an extraction unit 6 and a pipe 7 connecting this unit to the hydrocarbon deposit.

The means 5 comprise a first thermally insulated pipe 8 for circulating in a closed circuit from the surface of the hot fluid to the deposit and then again to the surface. This pipe 8 is connected to a unit 9 for heating and injecting the hot fluid continuously with continuous control of the temperature and the flow rate. This heating unit comprises a reservoir 23 or an expansion tank, a pump 10 and a heater 24. It goes without saying that this pipe 8 connects the unit 9 to the hydrocarbon deposit that it is heat. The expansion tank 23 makes it possible to accommodate the increase in volume of the hot oil in the closed circuit and thus avoid any overpressure in the circuit.

This first pipe 8 is surrounded by a second pipe 11 for bringing the hot fluid back to the unit 9. The pipes 8 and 11 constitute, with the hot fluid production unit 9, a closed circuit for the continuous circulation of this hot fluid.

In FIG. 2, the installation according to the invention has been represented at the level of the hydrocarbon deposit 12 which comprises a substantially vertical part 13 and a substantially horizontal part 14 of length 1. This envelope 3 is found in this figure, the end is provided with radial perforations 15 at its end in the deposit 12. These perforations allow the entry of the liquid 16 into the envelope 3. This part 14 of the envelope is commonly called strainer and there are the pipes 7 , 8 and 11. The pipe 7 extends from the surface to the start of the strainer 14 as can be seen in this figure.

In this strainer 14 of the casing 3, the first pipe 8 is open at its distal end 17 and the second pipe 11 is closed at its distal end 18 by a transverse wall. The insulator 21 can be a pulverulent material commonly used in this field. To reinforce the thermal insulation, the free or annular space delimited between the two tubes 19 and 20 is subjected to a reduced pressure. This reduced pressure can be between 1 and 100 mbar.

It is also possible to provide an electric heating wire applied to the level of the internal tube 19 so as to reinforce the thermal contribution of the pipe 8 as will be explained in relation to FIGS. 3 and 4.

The hot fluid circulating in a closed circuit in the deposit 12 can act thermally. By heating the deposit, its activity can be dissolving in order to limit, reduce or eliminate deposits, such as paraffins, asphaltenes or bitumen agglomerates, which during their solidification would deposit around the perforations 15 of the envelope 3, until they are closed. Since it is a closed circulation circuit, the deposit 12 does not undergo any contamination by the fluid used.

The fact of using a hot fluid confers a double action. The heat melts the already solidified or deposited fractions. The heat, dissipated by conducto-convection in the envelope 3 filled with fluid then by conduction in the deposit, acts in addition, by reducing the viscosity of the hydrocarbon 16. The latter becomes more fluid by being heated. By conduction in the rock of the deposit 12, the heat sent will fluidize the hydrocarbons to be extracted and, thereby, reduce the pressure drop. Thus, with the same pumping power, a larger quantity of liquid will be extracted (improvement of productivity) and it will be possible to pump liquid trapped further in the tank (improvement of recoverable reserves).

The depth of the well being able to reach several hundred meters (100 to 2000 m), it is essential to provide heat at the level of the deposit 12, to have a pipe 8 highly thermally insulated.

A thermally insulated pipe 8 has been provided. Line 8 is produced according to the technique known by the English term "pipe in pipe". Between the two tubes 19 and 20 is placed an insulator 21.

The internal tube 19 transports the hot fluid. This tube is mechanically protected by the second tube 20 of larger diameter concentric with the first tube 19 and thermally by the insulator 21.

Several possibilities are offered for producing an insulator between the two tubes 19 and 20. It is advantageous to provide an insulator 21 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 second pipes, to prevent the two tubes 19 and 20 from coming into contact with one another. A microporous material can be used as an insulator between the tubes 19 and 20.

This microporous material, of the type described in 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 / m3. The insulating thermal capacities of such a material are significantly improved when it is placed in the ring finger under low pressure between the two tubes 19 and 20.

It is also possible to produce an insulator 21 by producing a multilayer super-insulator consisting of reflective screens interposing layers of powder as described in patent FR-03.13197. 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 10 and 1 mbar between the two tubes 19 and 20. This insulator, having no resistance properties to sufficient compression requires the addition of spacers regularly between the tubes 19 and 20. The material used to make these spacers must have good insulating behavior. Such a material can advantageously be a microporous material as described above.

A pipeline as described above allows sufficient heat to make the hydrocarbons sufficiently fluid with a boiler of 20 to 500 KW. The installation 1 according to the invention makes it possible to increase the production of crude oil from 20 to 500%, to exploit abandoned reserves and to avoid any pollution of the deposits. As an indication, a pipe 8 according to the invention may consist of an outer tube 20 of 33 mm outside diameter with a thickness of 2 mm and an inner tube 19 of 13 mm outside diameter with a thickness of 2 mm and is able to transport 20 kW at 200 ° C over a total distance of 1000 meters. In this example, the pipe 11 can be a tube 60 mm in outside diameter with a thickness of 5 mm and the cylindrical envelope of 178 mm in diameter in the vertical part and 114 mm in the drain or strainer section. As a further indication, a pipe 8 consisting of an external tube 20 of 60 mm in diameter and 6 mm thick and of an internal tube 19 of 33 mm of external diameter and 4 mm thick will easily transport 200 kW to 200 ° C over a total distance of 2000 meters. In this case, the pipe 11 can be a 89 mm tube with a thickness of 6 mm and the cylindrical casing of 244 mm in diameter in the vertical part and 178 mm or 140 mm in the drain or strainer section.

In Figure 3, there is shown a section AA of Figure 1 in which we took the envelope 3. In this envelope, we find the pipes 7, 8 and 11. The first pipe 8 consists of a first tube internal 19 surrounded by a second concentric external tube 20 and an insulator 21 housed in the space between the two tubes.

We also see in this figure the heating wire 22 disposed along the outer wall of the inner tube 19 from the surface.

It goes without saying that the various elements illustrated in this FIG. 3 do not include a scale and are only shown for illustrative purposes.

In FIG. 4, which is a section BB in FIG. 2, we find the casing 3 fitted with pipes 8 and 11. As before, the first pipe 8 consists of a first internal tube 19 surrounded by a second tube external 20 concentric and an insulator 21 housed in the space between the two tubes. The third pipe 7 goes from the surface to the start of the strainer 14 or drain and is therefore absent in this figure.

Also shown in this figure is the heating wire 22 placed against the external wall of the internal tube 19.

It goes without saying that the various elements illustrated in this FIG. 4 do not include a scale and are only shown for illustrative purposes.

Claims (12)

1. Installation for reheating (1) the producing area of the deposit (12) of a well for the extraction of hydrocarbons through the well (2) connecting the surface to this deposit (12), comprising an envelope (3 ) substantially cylindrical consolidating said borehole and an extraction means (4) of hydrocarbons housed inside said envelope and means making it possible to circulate a hot heat-transfer fluid from the surface to the deposit (12), characterized in that it includes through the well (2) a first pipe (8) thermally insulated injection from the surface of the hot fluid to the deposit (12), a second pipe (it) surrounding the first pipe (8) to bring the hot fluid to the surface and a third pipe (7) for extracting hydrocarbons independent of the first and second pipes (8, il), said pipes extending from the surface to the deposit. 2. Reheating installation (1) according to claim 1, characterized in that the first (8) and second (it) pipes are connected to a station (9) for producing the hot fluid comprising a reservoir (23) or an expansion tank, a pump (10) and a heater (24) to ensure continuous circulation of the hot fluid in said pipes. 3. Reheating installation (1) according to claim 1 or 2, characterized in that the first pipe (8) is open at its distal end (17) and in that the second pipe (it) is closed at its distal end (18). 4. Reheating installation (1) according to any one of claims 1 to 3, characterized in that the first pipe (8) is thermally insulated using an insulation resistant to compression. 5. Reheating installation (1) according to one of claims 1 to 4, characterized in that the third pipe (7) is connected to an extraction unit (6) to bring up the surface of the hydrocarbons produced in the strainer or drain. 6. Reheating installation (1) according to claim 5, characterized in that the third pipe (7) is open at its distal end and provided with a downhole pump. 7. Reheating installation (1) according to any one of claims 1 to 6, characterized in that the first pipe (8) consists of a first internal tube (19) surrounded by a second external tube (20) concentric and an insulator (21) housed in the space between the two tubes. 8. reheating installation (1) according to claim 7, characterized in that the thermal insulator (21) is a microporous material and in that a reduced pressure is established in the space between the two tubes (19, 20). 9. Reheating installation (1) according to claim 8, characterized in that the reduced pressure between the two tubes (19, 20) of the first pipe (8) is between 1 and 100 mbar. 10. Reheating installation (1) according to any one of claims 7 to 9, characterized in that the first pipe (8) is provided with an electric heating wire (22) disposed against the external wall of the internal tube (19 ). 11. Reheating installation (1) according to any one of the preceding claims, characterized in that the heat transfer fluid for reheating the deposit (12) is an industrial thermal oil or water. 12. Application of the heating installation (1) according to any one of the preceding claims to the preheating in a closed circuit of a deposit upstream of the hydrocarbon extraction phase.