WO2019064043A1

WO2019064043A1 - Heating a zone of a reservoir

Info

Publication number: WO2019064043A1
Application number: PCT/IB2017/001395
Authority: WO
Inventors: Anne BRISSET
Original assignee: Total Sa
Priority date: 2017-09-28
Filing date: 2017-09-28
Publication date: 2019-04-04

Abstract

The invention notably relates to a method for producing hydrocarbons with a production well (10) arranged in a reservoir (20), the method comprising: heating a zone (30) of the reservoir; and meanwhile adding a liquid (32) to the heated zone, the liquid being heated and generating gas upon being added to the heated zone. This improves the field of hydrocarbon production.

Description

HEATING A ZONE OF A RESERVOIR

FIELD OF THE INVENTION

The invention relates to oil and/or gas extraction, and more particularly to a method and an installation for producing hydrocarbons with a production well arranged in a reservoir.

BACKGROUND

Different techniques are known for enhancing hydrocarbon production, in particular oil production. Among them are for example solutions based on steam injection, such as Steam Assisted Gravity Drainage (SAGD). These enhanced oil recovery (EOR) solutions consist in stimulating production by injecting steam in the reservoir. They are useful to increase recovery rate, notably in cases of reservoirs where the produced hydrocarbon has a high ratio of oil, such as heavy crude oil and bitumen. In such cases the hydrocarbon may present a relatively high viscosity which impedes its flow toward and inside the production well, making it difficult to produce.

Existing enhanced recovery techniques are however not fully satisfactory. Steam injection solutions for example involve vapor generation issues at the surface, and a large surface footprint in order to treat water outputted by the production well. This renders them relatively inadequate for offshore production. In order to be effective, steam injection solutions also require steam to be injected via an injection well located at a relatively low distance from the production well. Such relatively low distance constrains the scope of action of steam and thereby limits the quantity of hydrocarbon of which recovery can be enhanced.

In this context, there is still a need for an improved solution for producing hydrocarbons.

SUMMARY OF THE INVENTION

It is therefore provided a method for producing hydrocarbons with a production well arranged in a reservoir. The method comprises heating a zone of the reservoir, and meanwhile adding a liquid to the heated zone. The liquid is heated and generates gas upon being added to the heated zone.

The method may comprise one or more of the following: heating the zone of the reservoir comprises activating a heating element arranged in the zone;

the heating element is a heating cable;

the heating cable is an electrically heating cable;

- the adding of the liquid to the heated zone is performed via an injection well;

the adding of the liquid to the heated zone is performed via an injection well, the heating cable being arranged for liquid added to the injection well to reach and contact the heating cable;

- the liquid comprises water;

the method further comprises adding one or more additives to the heated zone;

the method comprises adding more additive than water; the one or more additives comprise a solvent or a reagent of a solvent producing reaction, and/or a surfactant or a reagent of a solvent producing reaction;

the one or more additives comprise carbamide and/or an alkane;

the production well comprises one or more perforations and the heated zone is located remote from the one or more perforations; - the heated zone is located at a distance from the one or more perforations higher than 5 or 10 meters; and/or

the production well comprises a horizontal section including the one or more perforations.

It is further provided an installation for producing hydrocarbons configured for performing the method. The installation comprises the production well arranged in the reservoir, a system configured for the heating of the zone of the reservoir, and a system configured for the adding of a liquid to the heated zone.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of non-limiting example, and in reference to the accompanying drawings, where FIGs. 1-2 illustrate an example of performing the method with an example of the installation. DETAILED DESCRIPTION OF THE INVENTION

The method is for producing hydrocarbons with a production well arranged in a reservoir. The method comprises heating a zone of the reservoir. The method also comprises, meanwhile (i.e. simultaneously) to the heating, adding a liquid to the heated zone. The method is performed in a way that, upon the liquid being added to the heated zone, the liquid is heated and generates gas.

The method thus performs an in situ heating of the reservoir, and along with such heating an in situ generation of gas inside the reservoir. This enhances hydrocarbon production. In other words, the method increases the quantity of hydrocarbons of the reservoir that the installation is able to produce and/or effectively produces, and/or the method increases the rate at which hydrocarbons are produced by the installation. The generation of gas being in situ, this enhancement may be obtained at a relatively low cost in terms of surface footprint and/or post-production water treatment.

The heat of the heated zone diffuses in the reservoir and thereby fluidifies hydrocarbons contained in the reservoir, as such enhancing hydrocarbon production. Moreover, the heating creates a high-pressure zone which sweeps fluids away from the heated zone, including hydrocarbons, thereby enhancing drainage.

In addition to the heating, the generation of gas forms a gas cap which yet enhances hydrocarbon production.

The addition of gas to hydrocarbons contained in the reservoir gas cap has in itself a positive impact on the fluidification.

The gas cap may further enhance flow toward the production well and/or inside the production well (e.g. acting as a turbine in the latter case). Compared to a mere heating, the addition of liquid and the gas cap accordingly generated leads to a relatively higher pressure, and thus to a relatively intense pressing of fluids away from the heated zone. Such artificially created gas cap is particularly useful in cases where the produced hydrocarbons initially contain a relatively low ratio of gas or no gas, as in such a situation no or little natural gas cap can be created for the purpose of acting as a turbine inside the production well. Moreover, the in situ generation of gas inside the reservoir allows creating a gas cap relatively voluminous in size, and thus a relatively large scope of action. In other words, the method enhances production of hydrocarbons contained in a relatively large zone of the reservoir and thereby the method enhances production of a relatively large quantity of hydrocarbon.

The reservoir may be any geological environment (e.g. a subsoil) comprising, consisting or forming a part of one or more hydrocarbon fields. The reservoir may in particular comprise hydrocarbons to be produced by the method. The method may comprise, during and/or after the heating of the zone and the addition of the liquid to the heated zone, extracting and/or receiving at the surface from the production well a mixture containing such hydrocarbons. The method may then comprise treating the mixture in any way, for example including to treat water (if present).

The hydrocarbons to be produced by the method may notably contain oil, such as heavy and/or viscous oil (e.g. heavy crude oil and/or bitumen). Such oil is particularly difficult to produce with traditional unenhanced methods. The method may produce hydrocarbons containing oil which presents a viscosity higher than 100, 200, 500 or 1000 centipoises. The oil may additionally be mobile oil, in other words oil able to flow (e.g. even if highly viscous), for example presenting a viscosity lower than 5000 or 3000 centipoises.

The production well may at least comprise a portion located at a relatively high depth (e.g. the depth applying the center of the portion), for example at a depth higher than 50, 100, 200, 500 or 1000 meters. The enhancement offered by the method proves particularly useful in such a situation. The portion may in examples be located at a depth lower than 5000 or 3000 meters.

The location of the heated zone may be configured for the generated gas to push hydrocarbons already inside the production well toward the surface. This enhances production by increasing production rate. Alternatively or additionally, the location of the heated zone may be configured for the generated gas to push hydrocarbon initially outside the production well toward the inside of the production well. This enhances production by increasing the oil recovery factor. The production well may comprise one or more perforations through which hydrocarbon enters and then flows toward the surface for production. The one or more perforations may be arranged on a section of the production well, which may in an example comprise several perforations regularly spread on at least a portion of the section. The heated zone may be located remote from the one or more perforations. This allows pushing hydrocarbon initially located outside the production well, precisely between the one or more perforations and the heated zone, toward the one or more perforations and inside of the production well.

The distance between the heated zone and the one or more perforations may be below a first predetermined threshold configured for the gas cap to press hydrocarbons already inside the production well toward the surface and/or hydrocarbons outside the production well toward the perforations. The first predetermined threshold may be lower than 100, 50 or 20 meters. Said distance may further be above a second predetermined threshold configured for the gas cap to press hydrocarbon initially outside the production well toward the inside of the perforations. The second predetermined threshold may be higher than 5 or 10 meters. The second predetermined threshold may also allow avoiding the generated gas to enter the production well, which would otherwise create turbulences inside the production well, to avoid impeding the oil production. The distance between the heated zone and the one or more perforations may for example be equal or of the order of 15 meters. The distance between the heated zone and the one or more perforations may be the minimum of each of the distances between the center of the heated zone and a respective one of the one or more perforations.

The production well may present any configuration.

The production well may comprise a horizontal section including the one or more perforations. The horizontal section may be a portion arranged in the reservoir e.g. and at a relatively high depth, for example at a depth higher than 50, 100, 200, 500 or 1000 meters.

In such a case, the heated zone may for example be located above the horizontal section, so as to induce a gravitational drainage and/or exert a downward pressure toward the horizontal section. Such downward pressure is particularly useful in case the reservoir is located above (e.g. and adjacent) to an aquifer, e.g. and the horizontal section is relatively close to such aquifer (for example at a distance below 20 meters). In such a case, the downward pressure allows reducing the risk of creation of a channel between the aquifer and the production well, which would otherwise reduce production efficiency. Indeed, in such a case the water of the aquifer would also be produced (and possibly in large quantities when oil is produced as said water is less viscous than oil). This would decrease production rate and/or induce specific water treatment at the surface.

Alternatively, the heated zone may be located below the horizontal section, for example in case the horizontal is located relatively far from an aquifer (e.g. the heated zone being in such a case located between the horizontal section and an aquifer) or there is no aquifer in the production environment. This allows recovery of hydrocarbons below the production well.

The production well may alternatively or additionally comprise a vertical section connected to the surface and/or including one or more perforations. In such a case, the heated zone may be located aside the vertical section (e.g. aside the one or more perforations).

The production well may comprise several horizontal and/or vertical sections each presenting one or more perforations. The production well may notably present a manifold structure comprising several horizontal sections.

In such case and other cases, the method may be repeated, for example each time with a different heated zone. The repetition of the method may be sequential, with instances of the method performed at different times with the same production well. Alternatively, the repetition may comprise executing several instances of the method at the same time or at overlapping times. In such a case, the method may comprise heating several zones of the reservoir and adding a liquid to each heated zone. This may generate several gas caps, for example one per set of perforations (e.g. one per horizontal section). The expression "heating zone" may thus designate a connected (i.e. compact) volume of the reservoir. The installation comprises for performing the method a system configured for the heating of the zone of the reservoir and a system configured for the adding of a liquid to the heated zone. The systems may share components.

The system may comprise a heating element arranged in the zone to be heated. The heating element may be any component which heats when activated. The heating element may comprise a heating surface. The heating element may be electrically activated. Electricity supply cables may thus connect the heating element to an electricity supply facility located at the surface. The heating element may be a heating cable, such as an electrically heating cable. A heating cable allows an elongate heating and thus an efficient gas cap to be created. A heating cable further allows an easy arrangement/insertion inside the reservoir, for example via a well (e.g. an injection well of the system for adding liquid). An electrically heating cable allows performing the method in a particularly simple way.

The heating element may present a maximal length higher than 5 meters (e.g. when located in a vertical injection well) and/or lower than 2000 meters (e.g. when located in a horizontal injection well). A heating cable may for example present a length higher than 5 meters (e.g. when located in a vertical injection well) and/or lower than 2000 meters (e.g. when located in a horizontal injection well), and/or a diameter higher than 1 cm and/or lower than 10 cm.

The liquid may then be added to heated zone and generate gas. The liquid may for example be added directly on a heating element, in other words so as to (physically) reach and contact the heating element. The heating zone or heating element is at a temperature adapted for the generation of gas and creation of the required gas cap upon the liquid being added (e.g. upon the liquid contacting the heating element).

The addition of the liquid to the heated zone may be performed via an injection well. In case of a heating element such as a cable, the heating element may be arranged with respect to the injection well, so as to receive liquid injected to the reservoir via the injection well such that said liquid reaches and contacts the heating cable. The heating element may for example be arranged at the extremity of the injection well, inside the injection well and/or along the injection well. In case of an electrically heating element, the electricity supply cables may pass within and/or along the injection well.

The method may comprise an initial step of arranging the heating element inside the reservoir (at a location corresponding to the zone to be heated).

The method may in examples be performed after a first production phase was performed with the same production well. The method may in such a case allow producing hydrocarbons "missed" (i.e. not recovered) during the first phase, for example due to their viscosity. In such a case, the method may for example comprise, after the first phase is ended, an initial step of arranging the heating element inside the zone to be heated. The injection well may be drilled after the first production phase. The extremity of the injection well may be provided for inserting and activating the heating cable therein. Such insertion and activation may be performed after the injection well is drilled and before the liquid for gas generation is added.

The liquid may generate gas in any way upon being added to the heated zone (e.g. upon contacting the heating element). The generation of gas may for example include one or more vaporizations and/or one or more chemical reactions.

For example, the liquid may comprise water and the heated zone or heated element may be at a temperature adapted for vaporization of water with respect to reservoir pressure (between 60 and 300 °C).

In examples, the method comprises adding only liquid water to the heated zone, such that the gas cap stems entirely from water vaporization.

In alternative examples, the method may comprise adding liquid water and one or more additives (i.e. additional compositions), which may for example participate in enhancing production in any way. The liquid added by the method may for example be a water solution of one or more additives (which are thus soluble in water). The method may comprise adding only such water solution to the heated zone, or alternatively, in addition to such water solution, simultaneously or not, one or more other additives (e.g. which may be insoluble in water).

The one or more additives may all be liquid or solid (e.g. dissolved). In that case, the only gas added to the reservoir by the method is the gas cap generated in situ. Alternatively, the one or more additives may include a gas. The one or more additives may comprise a solvent, for example C0₂. A solvent fluidifies hydrocarbons it is mixed with so as to reduce their viscosity.

The one or more additives may comprise a surfactant, for example NH3. A surfactant acts on the interfacial tension between rock and oil and has an emulsifying effect, which facilitates drainage.

The one or more additives may comprise a reagent of a solvent and/or surfactant producing reaction, that is a reagent of a chemical reaction producing such solvent and/or surfactant, such as a hydrolysis. The heated zone or heated element may be at a temperature adapted for of such chemical reaction with respect to reservoir pressure (between 60 and 300 °C). The solvent may for example be C0₂. The surfactant may for example be NH3.

The one or more additives may comprise carbamide: (CO(NH₂)2. Carbamide or urea is particularly cheap and may be provided in a solid or dissolved form, thereby allowing in situ generation of any gas. The method may be configured for the hydrolysis of carbamide to occur when water and carbamide is added to the heating zone and/or contacts the heating element. The hydrolysis of carbamide is provided by the following formula: CO(NH₂)₂ + H₂0 -> 2 N H3 + C0₂.

In examples, the method may add to the heating zone a water solution of carbamide (e.g. and no other additive). Upon being heated (e.g. by contacting the heating element), such a water solution of carbamide undergoes hydrolysis so as to enhance hydrocarbon production.

The one or more additives may comprise an alkane. Alkanes also are a reagent of a similar solvent and surfactant producing reaction.

The liquid may comprise more additive than water. This reduces quantity of water added to the reservoir and/or produced by the method and thereby to be treated.

In examples, water may be added at a rate between 0.005 and 0.1 and/or the total of the one or more additive (e.g. consisting of carbamide only) may be added at a rate between 0.17 and 0.350, where the rates are expressed in m³ per day and per meter of production well length. FIGs. 1-2 illustrate schematically and not to scale an example of performing the method with an example of the installation, respectively before and after the addition of liquid.

A production well 10 is arranged in a reservoir 20 located between a soil layer 24 and an aquifer 22. Production well 10 comprises horizontal section 11 which presents one or more perforations (not represented on the figures). The installation also comprises an injection well 14, and a heating cable 12 arranged at the extremity of the injection well 14. Heating cable 12 may for example be an electrically heating cable, for example connected to an electricity supply facility (not represented on the figures) located at the surface 26 with electricity supply cables passing within and/or along injection well 14 (not represented on the figures).

Heating cable 12 heats a zone 30 of the reservoir of relatively small size (e.g. all points at a distance from heating cable 12 inferior to a predetermined value smaller than 1 meter, e.g. about 50 centimeters) and located at a distance D above the one or more perforations (e.g. with D higher than 5 or 10 meters and/or lower than 100, 50 or 20 meters, e.g. D ~ 15 meters). Heating cable 12 is arranged so as to receive liquid 32 injected via injection well 14. Injection of liquid 32 is operated by any system, which is symbolically represented by tank 16 on the figures. Liquid 32 may comprise water and/or one or more additives. Upon contact of liquid 32 with heating cable 12, liquid 32 is heated and generates gas so as to create a gas cap 34 of relatively large size (e.g. with diameter of a size about or larger than 5 or 30 meters). Gas cap 34 is created above horizontal section 11 and perforations of production well 10. At the beginning of the injection, size of the gas cap will grow and will be adjusted based on the available distance between the production well 10 and the heating cable 12, in order to avoid gas coning into the production well 10.

Gas cap 34 enhances production by:

- Sweeping to a relatively high extent hydrocarbons contained in zone 21 located between heating cable 12 and horizontal section 11 toward perforations of horizontal section 11 and thereby increasing rate and/or quantity of hydrocarbons (even if presenting a high viscosity) penetrating production well 10. - Increasing flow 40 inside production well 10.

- Fluidifying hydrocarbons contained in reservoir 20 especially above horizontal section 11 thereby enhancing drainage, thanks to the heat induced by heating cable 12, gas cap 34 reducing viscosity of hydrocarbons it mixes with via addition of gas and/or action of a solvent and/or gas cap 34 modifying interfacial tension where it spreads via action of a surfactant.

- Reducing risks of channel creation between aquifer 22 and horizontal section 11 by exerting a downward pressure.

The example of the figures could be adapted and still enhance hydrocarbon production. Any one or any combination of the following non-limiting list of adaptations could for example be implemented:

- The production well could consist of a vertical section presenting perforations only and/or not comprise any horizontal section. The gas cap could be aside a vertical section presenting perforations.

- The injection well could comprise a horizontal section.

- The heating element could be any other heating element than a cable, for example a ball.

- The gas cap could be generated not directly above the horizontal section but also in an offset location.

- The reservoir could present a different shape and/or not be above an aquifer.

- The liquid 32 could be added with another system than tank 16.

- One or more additives could be added apart from liquid 32, simultaneously or at a different time.

Claims

1. A method for producing hydrocarbons with a production well (10) arranged in a reservoir (20), the method comprising:

- heating a zone (30) of the reservoir; and meanwhile

- adding a liquid (32) to the heated zone, the liquid being heated and generating gas upon being added to the heated zone.

2. The method of claim 1, wherein heating the zone of the reservoir comprises activating a heating element arranged in the zone.

3. The method of claim 2, wherein the heating element is a heating cable (12).

4. The method of claim 3, wherein the heating cable is an electrically heating cable.

5. The method of any one of claims 1 to 4, wherein the adding of the liquid to the heated zone is performed via an injection well (14).

6. The method of claim 3 or 4, wherein the adding of the liquid to the heated zone is performed via an injection well, the heating cable being arranged for liquid added to the injection well to reach and contact the heating cable.

7. The method of any one of claims 1 to 6, wherein the liquid comprises water.

8. The method of claim 7, wherein the method further comprises adding one or more additives to the heated zone.

9. The method of claim 8, wherein the method comprises adding more additive than water.

10. The method of claim 8 or 9, wherein the one or more additives comprise a solvent or a reagent of a solvent producing reaction, and/or a surfactant or a reagent of a solvent producing reaction.

11. The method of claim 10, wherein the one or more additives comprise carbamide and/or an alkane.

12. The method of any one of claims 1 to 11, wherein the production well comprises one or more perforations and the heated zone is located remote from the one or more perforations.

13. The method of claim 12, wherein the heated zone is located at a distance from the one or more perforations higher than 5 or 10 meters.

14. The method of claim 12 or 13, wherein the production well comprises a horizontal section (11) including the one or more perforations.

15. An installation (10-16) for producing hydrocarbons configured for performing the method of any one of claims 1 to 14, the installation comprising:

- the production well (10) arranged in the reservoir (20);

- a system (12-14) configured for the heating of the zone (30) of the reservoir; and

- a system (14-16) configured for the adding of a liquid to the heated zone.