Method for powering an offshore injection facility

Abstract

It is provided a method for powering an offshore injection facility of carbon storage in a subterranean reservoir. The method comprises flowing CO2 through a pipeline to the offshore injection facility; converting energy provided by the CO2 flow into electrical energy; and powering equipment located at the offshore injection facility using the electrical energy. The method forms an improved solution for electrically powering an offshore injection facility for carbon storage in a subterranean reservoir.

Description

[0001] METHOD FOR POWERING AN OFFSHORE INJECTION FACILITY

[0002] Technical field

[0003] The present disclosure relates to the field of power at offshore injection facilities of carbon storage in subterranean reservoirs, and more specifically to a method for powering an offshore injection facility of carbon storage in a subterranean reservoir. It is also provided an offshore injection facility and an onshore installation with an offshore injection facility.

[0004] Technical background

[0005] Carbon storage projects often use subterranean formations as storage candidates for CO2 (i.e., CO2). These subterranean formations may comprise existing depleted oil and / or gas subterranean reservoirs, depleted meaning that the pressure in the subterranean reservoir has diminished to a certain level. Saline aquifers can also serve as such reservoirs. CO2 is stored following CO2 capture to address the increasing demand for minimizing impacts on climate change.

[0006] There is an advantage in using existing subterranean depleted reservoirs as they are already proven to be capable of storing gas / oil for a long time, their storage size is known and they are already penetrated with a number of wells. On the other hand, saline aquifers are known to efficiently store water which can serve to store CO2.

[0007] These facilities, as many other facilities, require electrical power to operate (instrumentation, telemetry, communications, etc.). The electrical power can be provided from generators using gas, diesel or oil. The electrical power can be generated locally, if a gas or oil infrastructure is close. Alternatively, electrical power can be imported via a power cable. Alternatively, wind turbines or solar panels can be used to provide electrical power, with diesel generators as a backup. However, each of these solutions result in high cost, high maintenance, result in CO2 emissions, and add complexity to the logistics.

[0008] Within this context, there is still a need for an improved method for electrically powering an injection facility for carbon storage in a subterranean reservoir.

[0009] Summary of the invention

[0010] It is therefore the object of this invention to provide a method for powering an injection facility of carbon storage in a subterranean reservoir. The method comprises flowing CO2 through a pipeline to the injection facility, converting energy provided by the CO2 flow into electrical energy, and powering equipment located at the injection facility using the electrical energy.

[0011] The injection facility may be an offshore injection facility, or alternatively an onshore injection facility remote from an inlet of the pipeline in which CO2 is injected for flowing through the pipeline.

[0012] In examples, the method may optionally comprise any one or any combination of:

[0013] - the method comprises injecting the CO2 into the reservoir via an injection well, the pressure of the flowing CO2 when offloaded through the pipeline being higher than the pressure of the flowing CO2 when entered into the injection well;

[0014] - the pressure of the flowing CO2 when offloaded through the pipeline is at most 20% greater than the pressure of the flowing CO2 when entered into the injection well;

[0015] - the pressure of the flowing CO2 when offloaded through the pipeline is at least 2.5% greater than the pressure of the flowing CO2 when entered into the injection well;

[0016] - the pressure of the flowing CO2 when entered into the injection well lies from 15MPa to 30MPa, for example from 20MPa to 25MPa, and wherein the pressure of the flowing CO2 when offloaded through the pipeline has a value between 0.5MPa and 3MPa greater than the pressure of the flowing CO2 when offloaded through the pipeline, for example between 1 MPa and 2MPa greater;

[0017] - the method comprises selecting the pressure of the flowing CO2 when offloaded through the pipeline as a function of the length of the pipeline and / or the diameter of the pipeline and / or the flow rate of the CO2 and / or conditions of the subterranean reservoir;

[0018] - the method comprises, over a same period of time, injecting the CO2 into the reservoir via a plurality of injection wells, the pipeline comprising a respective terminal branch supplying each injection well and a common branch supplying each respective terminal branch, the pressure of the flowing CO2 when offloaded through the common branch being higher than the pressure of the flowing CO2 when entered into each injection well, and the method further comprises converting energy provided by the CO2 flow in the respective terminal branch supplying at least one first injection well into a first quantity of electrical energy, and converting energy provided by the CO2 flow in the respective terminal branch supplying at least one second injection well into either (i) a second quantity of electrical energy lower than the first quantity of electrical energy or (ii) a zero quantity of electrical energy;

[0019] - the method comprises injecting the CO2 into the reservoir via an injection well over a first period of time and then over a second period of time, the pressure of the flowing CO2 when offloaded through the pipeline being the same during the first period of time as during second period of time, the pressure of the flowing CO2 when entered into the injection well being lower during the first period of time than during the second period of time, the method converting, during the first period of time, energy provided by the CO2 flow into a first quantity of electrical energy, and the method converting, during the second period of time, energy provided by the CO2 flow into either (i) a second quantity of electrical energy lower than the first quantity of electrical energy or (ii) a zero quantity of electrical energy;

[0020] - the flowing of the CO2 has a flow rate of a maximum value of 0.4m3 / s, for example of a maximum of 0.3m3 / s;

[0021] - the flow rate provides a CO2 head ranging from 8m to 400m, for example from 10m to 300m;

[0022] - the injection facility is a subsea injection facility;

[0023] - the injection facility is at or above sea level;

[0024] - converting the energy to electrical energy comprises generating a minimum of 2kW, for example a minimum of 5kW ;

[0025] - converting the energy to electrical energy comprises generating a maximum of 500kW;

[0026] - the facility comprises one or more turbine generators, the converting being performed at least partly by one or more turbine generators;

[0027] - the facility comprises one or more pumps, the converting being performed at least partly by one or more pumps, for example a centrifugal pump;

[0028] - at least part of the electrical energy powers one or more batteries;

[0029] - the one or more batteries power instrumentation of the injection facility, such as telecommunications components, well control components, and / or lighting of the injection facility;

[0030] - the instrumentation of the injection facility includes one or more flow meters, one or more temperature sensors, and / or one or more pressure sensors;

[0031] - the pipeline has a length ranging from 50km to 700km, for example ranging from 100km to 600km, for example from 200km to 500km; - the CO2 flows through the pipeline to the injection facility from an onshore CO2 source; and / or

[0032] - the CO2 flows through the pipeline to the injection facility from an offshore CO2 source.

[0033] It is further provides an injection facility, for example an offshore injection facility, of carbon storage in a subterranean reservoir. The injection facility is configured for performing the above method.

[0034] It is further provides an installation including an onshore or offshore CO2 source connected by a pipeline to such an injection facility.

[0035] Brief description of the drawings

[0036] Non-limiting examples will now be described in reference to the accompanying drawings, where:

[0037] FIG. 1 A and FIG. 1 B show examples of installations for providing power to offshore injection facilities of carbon storage in a subterranean reservoir according to the prior art;

[0038] FIG. 2 and FIG. 3 each show an example of the installation of the present disclosure;

[0039] FIG 4 shows a schematic example of an implementation of the method according to the present disclosure.

[0040] FIG. 5 shows a schematic example wherein the method comprises, over a same period of time, injecting the CO2 into the reservoir via a plurality of injection wells.

[0041] FIG.s 6 to 10 show schematic examples of different architectures for adding turbine generators.

[0042] FIG. 11 shows phase diagrams.

[0043] Detailed description

[0044] The disclosure will now be described in detail without limitation in the following description, with reference to the example where the injection facility is an offshore injection facility. The description and presented concepts however equally apply to an onshore injection facility remote from an inlet of the pipeline in which CO2 is injected for flowing through the pipeline.

[0045] It is provided a method for powering an offshore injection facility of carbon storage in a subterranean reservoir. The method comprises flowing CO2 through a (e.g. pre-existing) CO2 pipeline (e.g. connected to an onshore or offshore CO2 source) to the offshore injection facility. The method comprises converting energy provided by the CO2 flow (i.e. the flowing of the CO2) into electrical energy (e.g., by turbining the CO2 flow). The method comprises powering equipment located at the offshore injection facility using the electrical energy.

[0046] The present disclosure makes it possible to address the need mentioned above.

[0047] In particular, the method provides a simpler and more environmentally friendly alternative to providing electrical power to an offshore injection facility of carbon storage in a subterranean reservoir.

[0048] This is achieved by converting energy provided by the flow of CO2 into electrical energy, for example by turbining the CO2 flow (i.e. flowing the CO2 into one or more turbine generators, such that the cinematic energy can be converted into electrical energy by the one or more turbine generators), and using the electrical energy to power equipment located at the offshore injection facility. This allows for the CO2 flow itself to be used as a power source, using infrastructure (e.g. the pipeline) that is already installed for the purpose of injecting CO2 to an offshore facility and into an injection well. This reduces (e.g. removes entirely) the need for using a dedicated power source for powering at least certain equipment of the facility. Consequently, the facility can be simplified and can operate in a more environmentally friendly manner. For example, this can allow for saving energy that may be supplied from a power cable and / or by a fuel such as diesel. Optionally, the method may allow for the removal of a power cable altogether from the offshore injection facility. For a fuel in particular, the method of the disclosure can also allow for reducing carbon emissions by reducing / eliminating use of the fuel for powering the injection facility.

[0049] By flowing CO2 through a CO2 pipeline to the offshore injection facility, it is meant flowing CO2 from a predetermined location, such as for example a CO2 feed point or from an onshore location, to the offshore injection facility. It is also meant flowing CO2 that is itself intended for injection into the subterranean reservoir. It can therefore also be understood that the CO2 is injected into an injection well fluidically connected to the subterranean reservoir. This therefore allows for a method that is multifunctional. In other words, the method reduces the need for having a dedicated method that is purely for the purpose of providing power to the offshore facility in addition to a dedicated method for flowing CO2 into an offshore subterranean reservoir. The CO2 pipeline is a pipeline that is conventionally used for carrying CO2 and that therefore satisfies the design requirements for carrying flowing CO2.

[0050] The CO2 pipeline may be a pipeline that is conventionally used for injecting CO2 into the subterranean reservoir. The CO2 pipeline may be a subsea pipeline, for example that lies on the seabed. As the CO2 pipeline is connected to an offshore injection facility, the CO2 pipeline may too be considered to be offshore, i.e. an offshore CO2 pipeline.

[0051] Converting energy provided by the flowing CO2 into electrical energy, results in harnessing the (kinetic) energy provided by the flowing CO2 to provide to the injection facility. In other words, the flowing CO2 itself provides power to the injection facility. The fact that the CO2 is flowing CO2 allows for providing an available source of energy. Converting the energy into electrical energy allows for powering equipment that can be electrically operated. The flow of CO2 allows foremost for the CO2 to arrive at the facility for subsequent subterranean storage, and optionally the pressure at which the CO2 arrives may be such that it is energetically speaking self-sufficient so as to achieve said subterranean storage. In turn, converting a fraction of that flow power into electrical power for feeding the equipment at the facility may cause little impact and induce only little increase in the power used for flowing the CO2, as the fraction may be small.

[0052] Such equipment may indeed be equipment that is used for operating the injection facility and / or for communicating facility and / or operation information to another location (e.g. an onshore location or other). Powering the equipment may comprise entirely powering one or more items of equipment (i.e. the only power source of the one or more items being the flowing CO2). Alternatively, powering the equipment may comprise partially powering one or more items of equipment.

[0053] By an offshore injection facility of carbon storage in a subterranean reservoir, it is meant an injection facility of carbon storage for example in a hydrocarbon reservoir or saline aquifer within a subterranean formation. This reservoir may be partly, substantially or fully depleted - i.e. the hydrocarbons or seawater in the reservoir may have been previously produced at the time the method of the disclosure is implemented. A reservoir is an underground portion wherein a fluid such as CO2 or hydrocarbons can be contained without substantially diffusing to neighboring portions. In this respect, the reservoir can be considered as a geological enclosure within a subterranean formation. For example, the neighboring portions may be made of rock material having a lower porosity than the rock material of the reservoir itself. In some variations, a layer of clay may be present above the reservoir. In some variations, a water-containing layer may be present below the reservoir. In some variations, the reservoir may be partly delimited by a crack creating a porosity discontinuity through which a fluid may not easily flow.

[0054] It is to be understood that the features of the method described herein can also apply to the offshore installation and / or the onshore installation, as these installations are configured for implementing the method. The method may comprise injecting the CO2 into the reservoir via an injection well, and the pressure of the flowing CO2 when offloaded through (i.e. injected into) the pipeline (i.e. supply pressure) may be higher than the pressure of the flowing CO2 when entered into the injection well (i.e. injection pressure). In other words, the method may comprise flowing CO2 into the pipeline (i.e. at a predetermined location of the pipeline such as at one end of the pipeline that is opposite to the end of the pipeline fluidically connected to the offshore injection facility and that is connected to a CO2 source) at a pressure that is higher than a pressure necessary for ensuring injection of the CO2 into an injection well of the offshore injection facility. The pressure necessary for injection is a pressure higher than the pressure inside the reservoir and therefore sufficient for said injection. The pressure necessary for injection therefore has a minimal value when entered into the injection well that allows for completing an injection based on pressure differential only. In other words, the minimal value of pressure required for entering into the injection well may be enough for the CO2 to flow independently into the reservoir from the injection well, i.e. for the CO2 to flow into the reservoir from the injection well using only the pressure of the CO2 upon injection, without any enhancement such as pumping. In particular, this minimal value is thus higher than the reservoir pressure.

[0055] By the supply pressure (i.e. initial pressure, that is, the pressure of the CO2 at its supply point, that is, at the inlet of the supply pipeline) being higher than the injection pressure, prior to injection into the injection well, and after arrival of the flowing CO2 at the injection facility, the CO2 can have a surplus of energy (for example exhibited by the pressure of the CO2) in addition to the energy required for completing injection. In other words, when arriving at the injection facility, the total pressure of the CO2 can be greater than the minimal pressure required for injection. There may be a pressure differential between the initial pressure and the total pressure, due to for example pressure drops along the length of the pipeline, for example due to friction. However, this pressure differential may be accounted for when offloading the CO2 through the pipeline (i.e. injecting the CO2 into the pipeline). The pressure of the CO2 when offloaded through the pipeline can therefore be a pressure value that is high enough to allow for injection of CO2 into the injection well after the occurrence of any pressure losses experienced by the flowing CO2 between its entry into the pipeline and its injection into the injection well (i.e. the point of injection).

[0056] This allows for providing a pressure differential of the CO2 arriving at the offshore injection facility that can be used for providing power to the offshore injection facility. This pressure differential can be harnessed from the flowing CO2 (i.e. the extra pressure can be taken out of the total pressure of the CO2) by translating the energy of the flowing CO2 into electrical energy. The flowing CO2, after the conversion of its provided energy to electrical energy, may subsequently be injected into the offshore injection well.

[0057] The initial pressure may be predetermined to be at a pressure high enough to result in a predetermined power output. In other words, the initial pressure may be predetermined to be at a pressure high enough so that the energy conversion can harness a predetermined portion of energy from the flowing CO2 and convert this energy into a predetermined quantity of electrical energy so as to achieve a predetermined power output to the equipment of the offshore facility. For example, the predetermined initial pressure may be high enough to power one or more specific items of equipment, such as for example lighting of the offshore injection facility (e.g. of the platform of the facility), one or more telecommunications components of the facility (e.g. exchange of monitoring data or control data), one or more items of instrumentation of the injection facility, and / or any other piece of equipment of the injection facility. The equipment may for example be powered by the predetermined quantity of harnessed energy through one or more batteries, or for example through a battery pack. The one or more batteries may be supplemental or back up energy sources for powering one or more pieces of equipment. Alternatively, the one or more batteries may power one or more pieces of equipment entirely.

[0058] According to some examples, the in itial / supply pressure of the flowing CO2 when offloading through the pipeline may be at most 20% greater than the pressure of the flowing CO2 when entered into the injection well. Additionally or alternatively, the initial / supply pressure may be at least 2.5% greater than the pressure of the flowing CO2 when entered into the injection well. A fraction of such a pressure drop can be sufficient to allow for providing a surplus of energy to the offshore facility that is sufficient for providing power (e.g. through a battery) to one or more items of equipment (e.g. several) of the injection facility. The initial / supply pressure may be at most 15% greater than the pressure of the flowing CO2 when entered into the injection well. The initial pressure may be at most 10% greater than the pressure of the flowing CO2 when entered into the injection well.

[0059] The percentage by which the pressure of the flowing CO2 when offloading through the pipeline is greater than the pressure of the flowing CO2 when entered into the injection well may depend on the desired power output that is to be extracted from the flowing CO2 at the offshore injection facility, i.e. the injected pressure may depend on the amount of energy required to power one or more desired pieces of equipment. Alternatively, the selected percentage may be a fixed or standard selected pressure, the choice of one or more pieces of equipment which are to be powered by the converted energy to be based on the available amount of energy provided by the flowing CO2.

[0060] Additionally or alternatively, the selected percentage may depend on the design pressure of the CO2 pipeline. The design pressure of the CO2 pipeline may range from 4000MPa to 35000MPa (40-350bar). The CO2 pipeline may be a carbon steel pipeline. The flowing CO2 may be liquid CO2, or dense-phase CO2. The CO2 may be dry or dehydrated CO2. The CO2 pipeline may therefore be a pipeline conventionally used for carrying liquid CO2. For example, the pipeline may be adapted to withstand the corrosive nature of the CO2.

[0061] Converting the energy into electrical energy may comprise generating (for a period of time and in average during said period of time) a minimum predetermined amount of power for supplying to equipment of the offshore injection facility. Converting the energy into electrical energy may comprise generating (for a period of time and in average during said period of time) a minimum of 2kW, for example a minimum of 5kW. Converting the energy into electrical energy may comprise generating a maximum of 500kW, , or for example a maximum of 300 kW or 10OkW, or for example a maximum of 20kW. Generating a minimum wattage (in average) of such values can allow for ensuring that the at least one or more items of equipment receive sufficient power. The higher values allow for a CO2 hub to be made, so as to supply several facilities and / or injection wells. In case there is no such hub and the CO2 flows to only one single facility, for a low power consumption facility, power up to 20 kW may be sufficient.

[0062] According to some examples, the pressure of the flowing CO2 when entered into the injection well may lie from 15MPa to 30MPa, for example from 20MPa to 25MPa and the pressure of the flowing CO2 when offloaded through the pipeline may have a value between 0.5MPa and 3MPa greater than the pressure of the flowing CO2 when offloaded into the pipeline, for example between 1 MPa and 2MPa greater.

[0063] The method may comprise selecting the pressure of the flowing CO2 when offloaded through the pipeline as a function of the length of the pipeline. Additionally or alternatively, the method may comprise selecting the pressure of the flowing CO2 when offloaded through the pipeline as a function of the diameter of the pipeline. Additionally or alternatively, the method may comprise selecting the pressure of the flowing CO2 when offloaded through the pipeline as a function of the flow rate of the CO2. Additionally or alternatively, the method may comprise selecting the pressure of the flowing CO2 when offloaded through the pipeline as a function of conditions of the subterranean reservoir. Additionally or alternatively, the method may comprise selecting the pressure of the flowing CO2 when offloaded through the pipeline as a function of the number of injection wells to be supplied with CO2 and / or to their (e.g. individual) pressure requirements (minimal pressure to achieve storage via pressure differential) and / or to the pressureimpacting (in terms of pressure drop) characteristics (e.g. including length and / or diameter) of their (e.g. individual) pipeline supplying branches.

[0064] The length of the pipeline and / or the diameter of the pipeline can have an impact on the pressure drop of the flowing CO2 as it moves through the CO2 pipeline. Therefore, the method may comprise selecting the pressure of the flowing CO2 when offloaded through the pipeline to be sufficiently high so as to account for any pressure drops along the pipeline so that, when the flowing CO2 arrives at the injection facility, it is still of a sufficiently high pressure (a predetermined pressure that is higher than injection pressure) for both supplying power to equipment of the injection facility and for injection into the offshore injection well(s). This can allow for a method that incorporates pipelines of a considerable length, i.e. for CO2 that is flowed to the offshore injection facility from a distant location. The pipeline may have a length ranging from 50km to 700km, for example ranging from 100km to 600km, for example from 200km to 500km. In other words, such distances can allow for long distance CO2 travel through the pipeline as opposed to forming the pressure of the flowing CO2 (i.e. increasing the pressure of the flowing CO2 to the desired value) when offloaded through the pipeline at the injection facility or in close proximity to the injection facility.

[0065] The method may comprise injecting the CO2 into the reservoir via the injection well over a first (e.g., continuous) period of time and then over a second (e.g., continuous) period of time. The second period of time may start after the first period of time ends, and optionally the second period of time may start exactly when the first period of time ends, the two periods of time thus being consecutive portions of a same larger period of time, said larger period of time being optionally non-interrupted. The (average) pressure of the flowing CO2 when offloaded through the pipeline may be (at least substantially) the same during the first period of time as during second period of time. The (average) pressure of the flowing CO2 when entered into the injection well may however be lower during the first period of time than during the second period of time. This may be due for example to the minimal pressure required for entering CO2 into the injection well during the first period of time being lower than the minimal pressure required for entering CO2 into the injection well during the second period of time, for example because the pressure of the reservoir has increased between the two periods of time (precisely due to the injection of CO2 into the reservoir that has occurred during the first period of time). The method may comprise converting, during the first period of time, energy provided by the CO2 flow into a first quantity of electrical energy, and during the second period of time, energy provided by the CO2 flow into either (i) a second (non-zero) quantity of electrical energy lower than the first quantity of electrical energy or (ii) a zero quantity of electrical energy.

[0066] The supply of CO2 into the pipeline may have been sized in view of the higher requirement of pressure during the second period of time, such that said supply is oversized when considering the first period of time only. However, instead of using said supply at partial capacity during the first period of time, the method may comprise using the supply at full or at least non-minimal capacity (non-minimal for the pressure requirement to inject the CO2 during the first period of time). In turn, the method may comprise converting energy provided by the CO2 flow into a first quantity of electrical energy during the first period of time, and either perform no such conversion during the second period of time, or perform a conversion to a lesser extent (since no or less pressure surplus is present during the second period of time). The method thus optimizes use of pressure surplus over the lifetime of the injection well, whereby during such lifetime pressure requirements increase to perform the carbon storage injection, such that accordingly any surplus becomes less and less present.

[0067] The method may comprise injecting the CO2 into the reservoir via a single injection well, over a certain period of time. The pipeline may in such a case be linear. Alternatively, the method may comprise injecting the CO2 into the reservoir via a plurality of injection wells (optionally belonging to the same facility), over a same period of time (each injection well is used to inject CO2 into the reservoir at least at some point during said same period of time). When the present disclosure refers, earlier and later, to “the” injection well, this must be understood as a reference to the single injection well in the case of a single injection well, or to at least one injection well of the plurality in the case of a plurality of injection wells, and for example to each injection well of the plurality in such a case.

[0068] In the case of a plurality of injection wells, the pipeline may comprise a respective terminal branch supplying each injection well and a common branch supplying each respective terminal branch. For example, the pipeline may comprise a manifold (or hub), the common branch supplying the manifold in CO2, and each respective terminal branch being supplied in CO2 at the manifold (the common branch being upstream the manifold, and the respective terminal branches being downstream the manifold). The pipeline may optionally comprise several such manifolds, the common branch referring to the section of the pipeline upstream the first manifold. A pipeline having one or more such manifolds allows for optimizing material consumption and pipeline total length, while using several injection wells for maximal carbon storage.

[0069] The pressure of the flowing CO2 when offloaded through the common branch may be higher (at least in average) than the pressure of the flowing CO2 when entered into each injection well, during said same period of time. In other words, the (average) pressure of the flowing CO2 when offloaded through the common branch may be higher than the maximum value between all (average) pressure values of the flowing CO2 when entered into each injection well, during said same period of time. In particular, the common branch of the pipeline may be supplied in CO2 by an installation such as a pump as described later, and such installation may be sized in view of the requirements in pressure of all the injection wells of the plurality, so as to notably satisfy the maximum requirement among them.

[0070] The method may further comprise, during said same period of time, converting energy provided by the CO2 flow in the respective terminal branch supplying at least one first injection well into a first quantity of electrical energy (per first injection well). During said same period of time, the method may comprise converting energy provided by the CO2 flow in the respective terminal branch supplying at least one second injection well into (per second injection well) either (i) a second quantity of electrical energy lower than the first quantity of electrical energy or (ii) a zero quantity of electrical energy. In other words, when considering potential conversion into electrical energy of CO2 flow inside the respective terminal branches, the method converts into electrical energy a lesser amount or even no amount at all of energy provided by the CO2 flow, depending on which respective terminal branch of which CO2 flow is used to perform the potential conversion.

[0071] This may be due for example to the minimal pressure required for entering CO2 into a first injection well being lower than the minimal pressure required for entering CO2 into a second injection well, for example because the pressure of the reservoir to which the first injection well connects is lower than the pressure of the reservoir to which the second injection well connects. Since the first injection well and the second injection well may be supplied by the same common branch of the same pipeline, the pipeline architecture is optimized, but in turn, the supply of CO2 into the common branch of the pipeline must be sized in view of the pressure requirement of the second injection well, which is higher than the requirement of the first injection well, such that supply may be oversized when considering the first injection well only. The method may thus turn this oversizing into an advantage by converting the surplus available in the respective terminal branch of the first injection well, due to this asymmetry (or by outputting more electrical energy from said conversion than from an optional conversion from a potential surplus also available -but to a lesser extent- in the respective terminal branch of the second injection well).

[0072] This may additionally or alternatively be due for example to the pressure drop being lower in the respective terminal branch terminal supplying the first injection well than in the respective terminal branch terminal supplying the second injection well, for example because the former is shorter and / or has a smaller diameter than the latter. Again, the supply of CO2 into the common branch of the pipeline must be sized in view of the pressure requirement of the second injection well, which is higher than the requirement of the first injection well so as to compensate for the higher pressure drop, such that supply may be oversized when considering the first injection well only. The method also turns this into an advantage.

[0073] The method thus optimizes the pipeline architecture and use of consequent pressure surpluses at individual injection wells.

[0074] A pump may pump the flowing CO2 to achieve the desired pressure upon entry of the CO2 into the (e.g. common branch of) pipeline. The pump may pump the CO2 to the injection facility. The pump may be located at the offloading point of the CO2, i.e. the point at which the CO2 is offloaded through the pipeline. The offloading point may for example be located at the point at which the pipeline enters the sea. For example, the offloading point may be located at one end of the pipeline that is connected to a CO2 source onshore (and that is opposite to the end fluid ically connected to the offshore injection facility). The onshore source may be another pipeline fluidically connected to the pipeline, or a CO2 source in the form of a tank or container or storage device. Alternatively for example, the offloading point may be located at one end of the pipeline that is connected to a CO2 source offshore (and that is opposite to the end fluidically connected to the offshore injection facility), for example an offshore vessel or ship. Alternatively for example, the offloading point may be located along the length of the pipeline (the pipeline running on land) at or just before entry of the pipeline into the sea.

[0075] The CO2 may flow at a predetermined flow rate. The method may comprise harnessing the kinetic energy provided by the flow rate of the flowing CO2 and converting this energy into the electrical energy. The pump may control the flow rate of the flowing CO2. The flowing CO2 may have a flow rate of a maximum value of 0.4 m3 / s, for example of a maximum of 0.3 m3 / s. If the entry to the injection well is at a predetermined height from the pipeline, i.e. is not at the same height as the pipeline relative to the seabed, flowing the CO2 at such rates can allow for the CO2 to build a head or static pressure when reaching the injection facility. The flow rate may provide a CO2 head ranging from 8 m to 400 m, for example from 10 m to 300 m. Such values can allow for ensuring sufficient pressure in the CO2 flow when arriving at the injection facility for conversion into electrical energy. Such values of flow rate may be applied if the injection facility is at or above sea level, being for example positioned on a rigid riser, and can ensure that the flowing CO2 is of a sufficient pressure for extracting electrical energy from the flowing CO2. According to some examples, the flowing CO2 may have a flow rate of a maximum value of 2 m3 / s, for example of 0.5 m / 3. Such values of flow rate may be applied if the injection facility is below sea level and can ensure that the flowing CO2 is of a sufficient pressure for extracting electrical energy from the flowing CO2.

[0076] The injection facility may be a subsea injection facility. The subsea injection facility may comprise a wellhead on the seabed. The pipeline may be fluidically connected to the injection well or jacket of the injection well.

[0077] Alternatively, the injection facility may be at or above sea level. The injection well may be held above sea level, for example by a platform fixed to the seabed. The injection facility may be fluidically connected to the injection well and may be supported by a rigid riser. By being at or above sea level, the flowing CO2 may travel upwards (substantially vertically, travelling from beneath the sea surface to at or above the sea surface) to reach the injection facility, the CO2 thereby forming a head of CO2 in the pipeline. As previously described, the energy provided by the pressure head may be used to provide electrical energy to the equipment and to inject the CO2 into the injection well.

[0078] As previously mentioned, the energy provided by the flowing CO2 may be exhibited by the pressure of the flowing CO2. In other words, the energy provided by the flowing CO2 may be expressed by the pressure (pressure energy) provided by the flowing CO2. Additionally, the energy provided by the CO2 may be expressed by the flow rate of the CO2 in the form of kinetic energy. Converting the energy provided by the flowing CO2 into electrical energy may comprise using the pressure of the CO2 to apply a force that moves a mechanical component (e.g. a plurality of blades) of the injection facility, converting the energy provided by the flowing CO2 comprising harnessing the energy from the movement of the mechanical component and converting this energy to electrical energy. The method may comprise converting the pressure energy of the flowing CO2 and kinetic energy provided by the flowing CO2, converting the energy into mechanical energy, and converting the mechanical energy into electrical energy. The energy provided by the flowing CO2 may be converted into electrical energy by flowing the CO2 into a device (e.g. turbine) that can receive energy and that can convert the energy into electrical energy. The device or turbine may use mechanical means (e.g. blades, rotor) to convert the energy into electrical energy. The device or turbine may use electromagnetic means (e.g. rotor, stator) to convert the energy into electrical energy. The device or turbine may use both mechanical and electromagnetic means to convert the energy into electrical energy. The device may for example be a turbine generator. Alternatively, the device may be a pump, such as a centrifugal pump.

[0079] The facility may comprise one or more turbine generators, the converting being performed at least partly by one or more turbine generators. The method can therefore allow for providing power like a hydropower plant. The one or more turbine generators can allow for an efficient way for converting the energy provided by the CO2 into electrical energy. The method may comprise using hydraulic turbine technology to recover power from the energy provided by the CO2 to power equipment of the injection facility, as such technology can be adapted to the ranges of rates, pressures and efficiencies required for the converting the provided energy of the flowing CO2. The turbine generators may each comprise a series of blades or vanes, a rotor, a rotor shaft and a stator. The flowing CO2 may enter the turbine generator and may push the series of blades of the turbine generator that are mounted on a rotor shaft. The CO2 may apply a force to the blades, resulting in their movement and a turning of the rotor shaft. In other words, the turbine generator may develop torque as a result of the pressure of the CO2. The rotational movement may be translated from the rotor shaft to the rotor, i.e. the rotor may too rotate or spin. The rotation or spinning of the rotor may generate a magnetic field that the stator can then convert to an electric current. In other words, the method may comprise converting mechanical energy into electrical energy by using a magnetic field formed by the mechanical energy. A magnet may be moved (e.g. rotated) by the mechanical energy of the turbine of the turbine generator, generating a magnetic field. The movement of a conductor into the magnetic field can result in a difference in voltage along the conductor, resulting in a flow of electric charge and finally an electric current. The electric current can then be supplied to one or more pieces of equipment of the injection facility.

[0080] The method may comprise flowing CO2 into one turbine generator for the energy conversion. This may for example be used for powering low-power consuming equipment. Alternatively, the method may comprise flowing CO2 into a plurality of turbine generators for the energy conversion. The one or more turbines of the turbine generators may be reaction turbines. The CO2 when flowing into the one or more reaction turbines may completely fill a plurality of vane passages of the turbine throughout the operation of the turbine. The one or more turbines may be mixed flow turbines. For example, the one or more turbines may be Francis turbines. The one or more turbines may be axial turbines. For example, the one or more turbines may be Kaplan turbines, or the one or more turbines may be propeller turbines.

[0081] If the one or more turbines are reaction turbines, only a portion (i.e. not all) of the energy of the flowing CO2 may be transformed into kinetic energy before the flowing CO2 enters the turbine runner. The CO2 may enter the runner with an excess pressure, and then both the velocity and pressure may change as CO2 passes through the runner. The blades of the turbine may be in constant motion / action while the turbine is running. The CO2 may be admitted into the turbine over the circumference of the wheel of the turbine. CO2 may completely fill the vane passages throughout the operation of the turbine. Pressure at inlet to the turbine may be much higher than the pressure at the outlet. The turbine unit may be sealed from atmospheric conditions with a casing. The turbine, within the casing, may be kept entirely submerged in CO2 below the tail race. Flow regulation of the CO2 may always be accompanied by loss. There may be a continuous drop in pressure during flowing of CO2 through the blade passages, the relative velocity thereby decreasing.

[0082] Additionally or alternatively, the facility may comprise one or more pumps, the converting being performed at least partly by the one or more pumps, for example a centrifugal pump. Each of the one or more pumps may be a pump as turbine (PAT). Each of the one or more pumps may use the energy of the CO2 (for example expressed as pressure and / or flow rate) to run each pump in reverse, thereby converting the energy of the CO2 into electrical energy. The pump may behave like a Francis turbine. The method may comprise flowing CO2 into one pump for the energy conversion. This may for example be used for powering low- power consuming equipment. Alternatively, the method may comprise flowing CO2 into a plurality of pumps for the energy conversion.

[0083] The injection facility may comprise one or more turbine generators only for the energy conversion (i.e. without the use of one or more pumps for performing the energy conversion). Alternatively, the injection facility may comprise one or more pumps only for the energy conversion (i.e. without the use of one or more turbine generators for performing the energy conversion). Alternatively, the injection facility may comprise one or more turbine generators and one or more pumps for the energy conversion. For example, the installation may comprise one pump and one turbine generator, or one pump and multiple turbine generators, or one turbine generator and multiple pumps, or multiple pumps and multiple turbine generators.

[0084] In the case of a plurality of injection wells, the injection facility may comprise at least one such device (turbine and / or pump) per each first injection well, that is, at least one device located on the pipeline terminal branch of each first injection well (i.e. located downstream any node of the pipeline with respect to the first injection well). In this way, the conversion of CO2 flow into electrical power / energy can be individualized for each first injection well, for example depending on the pressure requirement of the first injection well and / or the pressure drop of the respective terminal branch). Similarly, the injection facility may further comprise, optionally, at least one such device (turbine and / or pump) per each second injection well (in case non-zero conversion is to be performed for such second injection wells).

[0085] Each such device (turbine and / or pump) may further achieve a choke function (i.e. control the flow of CO2 injected into the injection well), such that the pipeline may comprise no separate choke valve (in addition to the turbine / pump) at all or no separate choke valve on the respective terminal branch of the pipeline, and in particular no choke valve at the wellhead of the injection well. In alternative designs, the pipeline or terminal branch may comprise a choke valve, and the device (turbine and / or pump) may be arranged in series and upstream the choke valve, in parallel to the choke valve and the choke valve is unique, in parallel to the choke valve and the pipeline or terminal comprises another choke valve arranged in series with the device / choke parallel assembly, or in series and downstream the choke valve.

[0086] The electrical energy resulting from the conversion of energy provided by the CO2 may power each of one or more batteries, for example a pack of batteries. The batteries may in turn provide power to one or more pieces of equipment of the injection facility. One pump executing the energy conversion or one turbine generator executing the energy conversion may provide electrical energy to one battery or to one or more batteries. The injection facility may comprise a plurality of turbine generators, each turbine generator providing electrical energy to one or more batteries. Alternatively, the injection facility may comprise a plurality of pumps, each pump providing electrical energy to one or more batteries.

[0087] The one or more batteries may power instrumentation of the offshore injection facility, telecommunications components, well control components, and / or lighting of the offshore injection facility. Consequently, the injection facility can operate with a reduced need for an external supply source. The instrumentation of the offshore injection facility may include one or more items of instrumentation for monitoring the flowing CO2. The instrumentation may include one or more flow meters, one or more temperature sensors, and / or one or more pressure sensors. The one or more items of instrumentation may include instrumentation for monitoring the CO2 itself, for example during injection. This can therefore allow for a method wherein the CO2 inadvertently allows for its own monitoring.

[0088] The batteries may power all the equipment needed in a standby situation, for example communications equipment, metering equipment, and / or the like. The batteries may also provide power for start up, e.g. to open valves, and / or in jacket solutions, e.g. to provide light.

[0089] The disclosure will now be described in relation to the following figures.

[0090] FIG. 1 A shows an example of an offshore injection facility 125 according to the prior art comprising a rigid riser 110 supporting an injection well 108. A power generator 103 is connected to the injection facility 125 (more specifically to equipment of the injection facility, although not represented in the figure), as illustrated by connection line 105. An onshore power source 104 powers an onshore pump 103 and the source 104 is also connected to the facility 125 by a power cable 101. The power cable 101 travels the same distance as a CO2 pipeline 100 in order to reach the injection facility 125. The power cable 101 is also a subsea power cable, requiring insulation to protect the electrical cable within from the surrounding sea water. Further, and although not illustrated as such in the figure, the power cable 101 is buried for protection against fishing and anchoring.

[0091] FIG. 1 B shows another example of an offshore injection facility 125 according to the prior art wherein the injection facility 125 is subsea. Like in FIG. 1A, a power cable 101 runs from onshore out to the injection facility 125 to power the equipment of the facility 125.

[0092] FIG. 2 shows an example of the offshore injection facility 125 according to the present disclosure. Features of such facilities already known from the examples of FIG.s 1A and / or 1 B are represented by alike numeral references. The figure is divided into three main sections 121 , 123, 125. The first section 121 shows an onshore facility 121 comprising a liquid CO2 source 106, a pump 102, a power source 104 powering the pump 102, and an offloading point for the CO2 in the form of an end of a CO2 pipeline 100. The second section 123 shows an offshore pipeline 100 submerged in the sea 107. The third section 125 shows the offshore injection facility 125. The injection facility 125 is a facility for carbon storage in a subterranean reservoir 114. The injection facility 125 is above sea level (the sea being indicated by area 107) and is supported by a rigid riser 110. CO2 flows through a pipeline 100 to the offshore injection facility 125. The CO2 flows into the pipeline 100 from onshore. The pipeline 100 is a subsea pipeline and lies on the seabed 109. A pump 102 pumps the CO2 as it is offloaded into the pipeline 100 from a CO2 source 106. The pump 102 pumps the CO2 to a pressure value high enough so that the CO2 can be successfully injected into an injection well 108 without need for additional pumping or other enhancement of the pressure. The CO2 source is in the form of another pipeline 106 fluidically connected to the pipeline 100. The CO2 flows through the pipeline 100 and to the injection facility 125 fluidically connected to the pipeline 100. As the offshore injection facility (and therefore the entrance to the injection well 108) is above sea level, the flowing CO2 travels upwards (substantially vertically) to reach the injection facility, the CO2 thereby forming a head of CO2 in the pipeline 100. Energy provided by the CO2, such as pressure from the head and / or kinetic energy from the flow rate of the flowing CO2, is converted into electrical energy. The CO2 may flow from the pipeline into a turbine generator 118, the pipeline being fluidically connected to the turbine generator 118 at one end of the pipeline 100. The turbine generator 118 converts the energy provided by the CO2 into mechanical energy using blades or vanes of the turbine generator 118. The turbine generator 118 converts the mechanical energy into electrical energy by using a magnetic field formed by the mechanical energy. In other words, a magnet is moved (e.g. rotated) by the mechanical energy of the turbine of the turbine generator 118, generating a magnetic field. The movement of a conductor into the magnetic field can result in a difference in voltage along the conductor, resulting in a flow of electric charge and finally an electric current. The electrical energy is provided to one or more batteries 122. The one or more batteries are then used to power equipment of the injection facility 125, as indicated by arrow line 126. Following the energy conversion, the remaining energy of the CO2 is used to flow the CO2 into the injection well 108. The CO2 flows into the injection well 108 and from the injection well 108 falls into the subterranean reservoir 114.

[0093] FIG. 3 shows another example of the offshore injection facility 125 according to the present disclosure. According to this example, the offshore injection facility 125 is a subsea offshore injection facility 125. CO2 flows through the pipeline 100 from the onshore facility 121 . The CO2 flows through the pipeline 100 until it reaches the subsea offshore injection facility. The subsea injection facility 125 is at the same height or a similar height as the pipeline 100. The pressure of the CO2 and / or the flow rate of the flowing CO2 may exhibit the provided energy of the flowing CO2. The subsea injection facility 125 may alternatively be at a position that is higher than (i.e. closer to the sea surface) the position of the CO2 pipeline and the flowing CO2 may therefore form a pressure head for the energy conversion. The CO2 enters the injection facility 15 via the turbine generator 118, such as through an inlet of the turbine generator 118.

[0094] FIG. 4 shows an example of an implementation of the method. In a first step 402, liquid CO2 is provided as a source of CO2 for the offshore injection facility. The liquid CO2 is at a pressure Psuppiy at the inlet to a booster pump, the pressure being 6MPa to ensure the CO2 is in a liquid phase only at ambient temperature. In a second step 404, a power input Winput is provided to a pump. In a third step 406, the pump pumps the CO2. In a fourth step 408, liquid flows into the inlet of the pipeline. The liquid CO2 has an inlet pressure that can be expressed by the following equation:

[0095] Pinlet=Pinj + dPturbine + dPfriction, wherein Piniet is the pressure at the inlet, Pinj is the injection pressure (or minimal injection pressure), dPturbine is the pressure differential caused by flowing the CO2 through a turbine generator, and dPfriction is the pressure differential caused by friction along the length of the CO2 pipeline.

[0096] In a fifth step 410, CO2 flows along the length of the (offshore) pipeline. The pressure of the CO2 undergoes pressure losses due to friction with the pipeline (dPfriction) as the CO2 flows through the pipeline. In a sixth step 412, the liquid CO2 flows from the outlet of the pipeline (i.e. the end of the pipeline flu idically connected to the offshore injection facility). The pressure at the outlet of the pipeline can be expressed by the following equation:

[0097] Poutlet=Pinlet - dPfriction, wherein Poutiet is the pressure at the outlet, Piniet is the pressure at the inlet and dPfriction is the pressure differential caused by friction.

[0098] In a seventh step 414, the CO2 flows from the pipeline and into a turbine generator. The CO2 experiences a pressure drop from the turbine, expressed by pressure differential dPturbine. The turbine converts the energy provided by the CO2 from the pressure drop dPturbine to electrical energy. In an eight step 416, the electrical energy is used to power equipment of the injection facility, the power output being expressed as Wout. In a ninth step 418, CO2 is injected at the injection pressure Pinj into the wellhead of the offshore injection well. In a tenth step 420, the flowing CO2 upon injection reaches the subterranean reservoir, wherein it can be stored. The sequence between the steps is not limited to the described ordering, although this can be one implementation example. FIG. 5 illustrates an example of the case where the facility comprises a plurality of injection wells 511 , 512 and 513, supplied by a same pipeline having a common branch 520, a manifold / hub P10, and individual terminal branches P10- P21 , P10-P22, and P10-P23 supplying each respective well 511 , 512 and 513. In such a case, the facility may comprise a turbine (or pump) 540 arranged on the common branch 520 of the pipeline, and additionally, or alternatively, a respective turbine (or pump) 541 , 543 arranged on the terminal branch of each first well, 511 and 513 here in the example. This way, the conversion of CO2 flow into electrical energy can be performed commonly for all wells with turbine 540, and / or individually for each relevant well 511 and 513 with turbines 541 and 543. In the example, the second well 512 is shown as not comprising any turbine / pump, but alternatively the second well 512 could also comprise such an individual turbine for individual conversion. In the example, the individual devices 541 and 543 are arranged on their respective terminal branch downstream the node P10 of the pipeline where the common branch 520 is divided into its terminal branches, and further in series and upstream respective choke valves 531 and 533. But other designs can be implemented with the same facility architecture.

[0099] The example of FIG. 5 takes into account the discrepancy in the overhead pressure needed to inject CO2, which is due to the difference in the reservoir pressure, well completion, and distance from the CO2 export point, for each individual well 511 , 512, 513. The pressure of the pipeline in the common branch 520 may be imposed by the well 512 which needs the highest pressure for injectivity. Hence the other wells 511 and 513 might have excess pressure at wellhead. The wellhead pressure needed for the different wells is thus not identical. The highest pressure is the one imposing the overall system pressure. Also, pressure evolves along the lifetime ofthe wells from a lower value to a higher value. This is more significant in case of depleted reservoirs.

[0100] The facility and method of the example addresses such a case of CO2 hubs with multiple wells / platforms resulting in some wells with higher well head pressure compared to other ones, as it allows for recovery of extra energy from the CO2 flow in such a case. This energy would have been lost via the chokes 531 , 532 and 533 if not recovered. This ensures self-sufficiency in terms of energy production for the facility. This facility may implement use of energy storage facilities such as batteries to ensure system availability, and / or use of static head energy of water to store part of the energy (such as with a compressed air energy storage balloon). The recovery of energy at high pressure allows to have small scale turbines with limited footprint and weight on the platform. A single phase (liquid phase) operation permits to have a compact system. This all results in a compact solution for offshore applications.

[0101] Referring to FIG.s 6-10, different configurations to arrange each CO2 flow converting device (e.g. turbine or pump) are now discussed.

[0102] The device may be arranged at different alternative locations vis-a-vis a choke valve upstream an injection well (e.g. at the wellhead), for example before (upstream), after (downstream), or in parallel of the choke.

[0103] In one configuration, the device can replace the choke (FIG. 6). In designs wherein the terminal branch of the injection well has a choke upstream (FIGs. 7- 10), the presence of the choke allows to precisely control the well head pressure and consequently flow rate. In addition, the pressure drop imposed by injection requirements may be well above the pressure drop needed to produce the electricity. This may be managed by inlet guide vanes of the turbine, preferably at a liquid phase. A choke which already has inlet valves allows a narrow control on the pressure. The facility may optionally comprise expanders on each well, so as to allow back-up solutions in case maintenance is needed.

[0104] FIG. 6 shows in a more detail a first design wherein the traditional choke 630 is replaced by a turbine 640, such that the facility or pipeline or pipeline terminal branch comprises no such choke 630 in this first design (whereas it comprises at least one such choke in the other designs, as shown on FIG.s 7-10, which use the same symbolic representation as FIG. 6 for representing the choke and the turbine). In this first design, all the CO2 flows through the turbine. The turbine may be configured to provide both a predefined mechanical energy (for electricity production) and a predefined pressure drop to ensure correct wellhead pressure.

[0105] FIG. 7 shows a second design wherein the terminal branch of the injection well has a turbine in parallel to the choke. The flow rate through the turbine is controlled. This further allows a flow control FT on the choke valve or choke line to control flow through the turbine. The flow rate may be controlled as a function of the required pressure drop for the wellhead and the electricity production. This design provides a high flexibility. In addition, the turbine may be selected to optimize its size and also energy generation requirements.

[0106] FIG. 8 shows a third design wherein the terminal branch of the injection well has a turbine placed upstream of the choke valve. This allows an exact control on the outlet pressure. A smaller pressure drop may be achieved as all the flow passes through an expander. As all the flow passes through the turbine, it may present a relatively larger size than other designs. This design can produce maximum electricity with possible export to other facilities at proximity. FIG. 9 shows a fourth design wherein the terminal branch of the injection well has, as a variant to the third design, a bypass line added around the turbine. This allows to adapt the flow rate and hence the size of the turbine and hence the overall system weight. Such a bypass facilitates maintenance, as flow can be maintained while the turbine is isolated for maintenance. In case of a biphasic injection, the turbine can be kept at a single phase condition and the choke can be used for any phase change.

[0107] FIG. 10 shows a fifth design wherein the terminal branch of the injection well has a turbine downstream the choke. The flow enters with a cooler temperature into the turbine. In case of a biphasic injection, the turbine may have a biphasic design.

[0108] FIG. 11 illustrates different phase diagrams for pure CO2, for CO2 mixed with other components (e.g. nitrogen) for ship transportation, and for CO2 mixed with other components (e.g. nitrogen) for pipeline transportation. The figure also shows phases of the examples presented in the later table.

[0109] Single phase (liquid or SC) is preferred. Thanks to the single liquid phase, the system may stay well away from cavitation risks and well above NPSH. In addition, higher density results in a compact system. The temperature reduction may also be small inside the system.

[0110] Any one of three designs may be implemented based on the CO2 phases. For the single phase, this may be liquid turbines. As illustrated on the graph, the pressures are well above the two-phase region. For the supercritical phase, this may be supercritical turbines. The temperature is above the critical point, such that there is no phase change. For the two-phase region, two-phase turbines may be used, wherein CO2 changes its phase from liquid to gas or gas-liquid.

[0111] Any one of two configurations may be implemented based on the throughput. This may be full flow: all of the CO2 flows through the turbine. This may alternatively be partial flow: only a portion of the fluid flows via the turbine.

[0112] Six examples based on the above principles have been computed as shown in the table below:

[0113] Examples 1 - 5: single phase liquid turbine with different flow rates and different pressure drops

[0114] Example 6: biphasic gas - liquid turbine Example 7: super critical phase turbine with no phase change

[0115] The turbine efficiency for all cases is 50%. The electrical efficiency in all cases is 98%. The flow and pressure drop are determining factors, independently from of designs shown previously.

[0116] Electric power required in a platform varies as a function of the design. A power of 10 kW may be sufficient for a typical platform with a 1 to 3 mtpa injection rate. As illustrated in the examples of the table, this level of electricity can be easily achieved with a 0.5 mtpa flow and a pressure drop of 10 bar (example 5), or 0.2 mtpa and 30 bar pressure drop (example 6).

Claims

Claims1. A method for powering an injection facility of carbon storage in a subterranean reservoir, the method comprising:- flowing CO2 through a pipeline to the injection facility;- converting energy provided by the CO2 flow into electrical energy; and- powering equipment located at the injection facility using the electrical energy.

2. The method according to claim 1 , wherein the method comprises injecting the CO2 into the reservoir via an injection well, the pressure of the flowing CO2 when offloaded through the pipeline being higher than the pressure of the flowing CO2 when entered into the injection well.

3. The method according to claim 2, wherein the pressure of the flowing CO2 when offloaded through the pipeline is at most 20% greater than the pressure of the flowing CO2 when entered into the injection well.

4. The method according to 2 or 3, wherein the pressure of the flowing CO2 when offloaded through the pipeline is at least 2.5% greater than the pressure of the flowing CO2 when entered into the injection well.

5. The method according to any one of claims 2 to 4, wherein the pressure of the flowing CO2 when entered into the injection well lies from 15MPa to 30MPa, for example from 20MPa to 25MPa, and wherein the pressure of the flowing CO2 when offloaded through the pipeline has a value between 0.5MPa and 3MPa greater than the pressure of the flowing CO2 when offloaded through the pipeline, for example between 1 MPa and 2MPa greater.

6. The method according to any one of claims 2 to 5, wherein the method comprises selecting the pressure of the flowing CO2 when offloaded through the pipeline as a function of the length of the pipeline and / or the diameter of the pipeline and / or the flow rate of the CO2 and / or conditions of the subterranean reservoir.

7. The method according to any one of claims 1 to 6, wherein the method comprises, over a same period of time, injecting the CO2 into the reservoir via a plurality of injection wells, the pipeline comprising a respective terminal branch supplying each injection well and a common branch supplying each respective terminal branch, the pressure of the flowing CO2 when offloaded through the common branch being higher than the pressure of the flowing CO2 when entered into each injection well, and the method further comprises converting energy provided by the CO2 flow in the respective terminal branch supplying at least one first injection well into a first quantity of electrical energy, and converting energy provided by the CO2 flow in the respective terminal branch supplying at least one second injection well into either (i) a second quantity of electrical energy lower than the first quantity of electrical energy or (ii) a zero quantity of electrical energy.

8. The method according to any one of claims 1 to 7, wherein the method comprises injecting the CO2 into the reservoir via an injection well over a first period of time and then over a second period of time, the pressure of the flowing CO2 when offloaded through the pipeline being the same during the first period of time as during second period of time, the pressure of the flowing CO2 when entered into the injection well being lower during the first period of time than during the second period of time, the method converting, during the first period of time, energy provided by the CO2 flow into a first quantity of electrical energy, and the method converting, during the second period of time, energy provided by the CO2 flow into either (i) a second quantity of electrical energy lower than the first quantity of electrical energy or (ii) a zero quantity of electrical energy.

9. The method according to any one of claims 1 to 8, wherein the flowing of the CO2 has a flow rate of a maximum value of 0.4m3 / s, for example of a maximum of 0.3m3 / s.

10. The method according to claim 9, wherein the flow rate provides a CO2 head ranging from 8m to 400m, for example from 10m to 300m.

11. The method according to any one of claims 1 to 10, wherein the injection facility is a subsea injection facility.

12. The method according to any one of claims 1 to 11 , wherein the injection facility is at or above sea level.

13. The method according to any one of claims 1 to 12, wherein converting the energy to electrical energy comprises generating a minimum of 2kW, for example a minimum of 5kW .

14. The method according to any one of claims 1 to 13, wherein converting the energy to electrical energy comprises generating a maximum of 500kW.

15. The method according to any one of claims 1 to 14, wherein the facility comprises one or more turbine generators, the converting being performed at least partly by one or more turbine generators.

16. The method according to any one of claims 1 to 15, wherein the facility comprises one or more pumps, the converting being performed at least partly by one or more pumps, for example a centrifugal pump.

17. The method according to any one of claims 1 to 16, wherein at least part of the electrical energy powers one or more batteries.

18. The method according to according to claim 17, wherein the one or more batteries power instrumentation of the injection facility, such as telecommunications components, well control components, and / or lighting of the injection facility.

19. The method according to claim 18, wherein the instrumentation of the injection facility includes one or more flow meters, one or more temperature sensors, and / or one or more pressure sensors.

20. The method according to any one of claims 1 to 19, wherein the pipeline has a length ranging from 50km to 700km, for example ranging from 100km to 600km, for example from 200km to 500km.

21. The method according to any one of claims 1 to 20, wherein the CO2 flows through the pipeline to the injection facility from an onshore CO2 source.

22. The method according to any one of claims 1 to 21 , wherein the CO2 flows through the pipeline to the injection facility from an offshore CO2 source.

23. An injection facility of carbon storage in a subterranean reservoir, the injection facility being configured for performing the method according to any one of claims 1 to 22.

24. An installation including an onshore or offshore CO2 source connected by a pipeline to an injection facility according to claim 23.

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