WO2023014227A1

WO2023014227A1 - System and method for geothermal power production

Info

Publication number: WO2023014227A1
Application number: PCT/NO2022/050185
Authority: WO
Inventors: Eivind GIMSE
Original assignee: Oktra As
Priority date: 2021-08-02
Filing date: 2022-07-31
Publication date: 2023-02-09
Also published as: NO20210956A1

Abstract

The present invention discloses a system and method for utilizing geothermal energy from existing oil and gas wells installations, taking advantage from the offshore geological sources for production of electric power, comprising existing offshore installations 102 including oil/gas/hydrocarbon wells 110 and means for an offshore geothermal powerplant 101. The powerplant 101 is located next to installations 102; where powerplant 101 utilizes an organic rankine cycle (ORC) 104 with a closed loop working fluid 208. The heat exchanger 206 is fed by hot liquid 202 directly from wells 110 and where condenser 211 is fed by cold seawater 209, neither hot liquid 202 or seawater 209 is in contact with the working fluid, but returned to said well and sea, respectfully.

Description

Title of Invention: System and method for geothermal power production

Technical Field

[0001 ] The present invention relates to means for converting installations built for search and production of hydrocarbons, into means for geothermal energy extraction. More specifically the invention relates to means for converting geothermal energy into electricity by capturing geothermal heat from offshore wells, drilled for oil and gas production from platforms installed on seabed or part of floating installations.

Background Art

[0002] The search for hydrocarbons at big scale use (as fuel for energy) is at present a political topic. As this has shown to have a negative impact on the environment, as the burning of oil and gas increases the level of CO2 in the world’s atmosphere, thus increasing the temperature on the planet. As oil wells have been drained and installations are shut down, the world is looking for environmentally friendly energy sources.

[0003] When the offshore hydrocarbon fields have been depleted and production has stopped, the permanent sealing of well and dismantling and/or removing of installations, will represent huge costs for the industry.

[0004] The invention seeks to contribute towards transforming the offshore oil and gas industry into environmentally friendly energy production. Electricity production may extend an installation of lifetime and postpone cost of decommissioning.

[0005] There are however different ideas on how to utilize these installations for future operations and for environmentally friendly energy production based on the existing technology. The basic idea to reuse of installations and wells for capturing geothermal heat contains prior art.

[0006] US 6000471 , Langset, Dec. 14, 1999, discloses a method for using old wells offshore, earlier used for the extraction of hydrocarbons, for the now new use for extraction of geothermal energy. The offshore installation is proposed for using means for converting the heat energy into electricity using pipes in loops to conduct the heat exchange fluid through the existing wells, two wells at the time, although this is not shown or described in any detail. The publication discloses an example from utilizing 2 X 20 wells at Statfjord B., which is estimating to enable production of 65MW electricity.

[0007] US 2013/0300127 A1 , DiNicolantonio, Nov.14, 2013, discloses a method and apparatus for recovering geothermal heat from abandoned sub sea oil wells and converting it to electricity. It uses a heat transfer fluid down well and has focus on the piping and system. The claims are however unclear and not formally written, the case anyway now abandoned.

[0008] US 861600, Parella, Dec. 31 , 2013, also discloses a system for recovering geothermal heat from predrilled oil wells, other pre-drilled operations and new wells, to generate electricity. It uses a closed loop solid-state heat extracting system including insulation of the piping. The piping system is the essence here, as the heat is extracted from heating exchanging elements within a well and rock. This publication is not especially aimed at offshore operations, but a large number of prior art is listed, US patents and publications from 1965 to 2011 and other international patents and literature.

[0009] Prior art finds it problematic to use a closed loop system for heat exchange fluids underground in wells and rock. The invention however uses the produced water and other liquids from the wells directly, including a separator and purifier system, as the high temperature input to an Organic Rankine Cycle (ORC) system to generate electric power.

[0010] By utilizing the hot water from the oil and gas reservoirs and an efficient cooling from the sea, electric power can be produced with an Organic Rankine Cycle (ORC) system. One important challenge has been the vast size and weight of these systems for industrial size production.

[0011] Neither of the prior art has addressed this issue and this is the main reason why offshore production of electricity utilizing this method has yet to be seen constructed. Numerous plants reusing petroleum wells for electricity generation are in production onshore, where there are no limitations on space and weight. However, air-cooling is most often used and is costly and inefficient. [0012] Windmills have become popular, and most of windmills have been placed on land however, to increasing protests on large footprint - impact on landmasses, nature and birds. Windmills at sea are increasing, however this requires large investments, complex installations and large footprint. The performance is also uneven (dependent on wind - 41% of theoretical maximum) and must rely on backup power from shore or gas turbines. The total Co2 footprint is also an issue.

[0013] Compared to offshore windmill farms, the geothermal power production does not depend on wind, has no impact on the environment (footprint on seabed and effect on wildlife), reuses subsea and production knowledge gained from decades of petroleum exploration and continue to utilize drilling and production investments from depleted, abandoned or halted oil and gas production.

[0014] Mega-Watts for floating windmills easily require 4-5 times the Capex compared to a geothermal solution based in existing offshore installations and wells.

[0015] Reservoir/well temperatures are typically 60-180 °C from 2000 to 5000m below seabed, and there is a vast supply of hot liquid (water) and unlimited cooling in the heat exchange system is done by cold seawater. Existing offshore production installations have each tenfold of drilled wells. The number of plugged wells from the Norwegian North Sea is estimated to be 250 in the 2021 - 2029 period.

[0016] The existing world shipping fleet has enormous carbon emissions, and it is now proposed to be included in EU Emission trading system (ETS). In the future, the world’s fleet of ships therefore will have to be electrified or use other means than today’s oil dependent vessels. It is expected that charging station out at sea will be of demand.

[0017] KR20150074709, Lee et al. July. 2, 2015, discloses a floating charging station for vessels, powered by windmills. This solution is however dependent on wind and the power of the wind as mentioned above.

Summary of Invention

[0018] The present invention discloses a system converting offshore installations built for drilling and production of hydrocarbons, converting geothermal energy into electricity. This includes reuse of offshore oil and gas installations and production knowledge gained from decades of exploration and continue to utilize drilling and production investments from depleted, halted or abandoned oil and gas wells. By utilizing the hot water produced from the oil and gas reservoirs and efficient cooling from the sea, electric power can be produced by a plant, utilizing an Organic Rankine Cycle (ORC) system.

[0019] The invention comprises a system for utilising the many wells and the access to enormous amount of warm liquid from the underground reservoir through existing installations. The solution to the vast size and weight of these systems for industrial size production is to deploy a separate platform, rig or floating unit, which can carry the powerplant (ORC) and position this floating geothermal powerplant next to an existing oil/gas production installation. To produce 20MW it will demand 5000m2 and weigh 1000 tons.

[0020] Two levels of ORC on one platform could produce up to 40MW.

[0021] The invention allows the installation to continue to extract oil form the wells, and at the same time produce hot water for the ORC system. An oil, gas and water system and separator are therefore part of the invention.

[0022] Within the invention there are two options for hot water supply; 1 ) during ongoing petroleum production after the oil-water separation and before the water is re-injected into the reservoir; 2) production of water from the reservoir after the end of hydrocarbon production. Cold water from the sea is supplied to cool of the ORC unit (condensation of the working fluid). It is released back to the sea, as it does not mix with other fluids.

[0023] The floating geothermal plant of the invention will produce electricity for exporting to other offshore installations, and for exporting to the PowerGrid, charge and store batteries.

[0024] Also, the platform can support a charging station for marine vessels or means for exchange of batteries of vessels, out at sea. Such a station at sea, far from land, will include landing facilities for helicopters and means for charging of electrified aircrafts. [0025] Such a station can provide service to any marine vessel and helicopters or aeroplanes and their crew/passengers including typical hotel facilities.

[0026] The invention therefore represents a system and method for utilizing geothermal energy from existing oil and gas wells installations, taking advantage of offshore geological sources of hot water for production of electric power, through an ORC powerplant. The invention is further disclosed in the following description and as defined in claim 1 and following subclaims 2-1 1 .

Brief Description of Drawings

[0027] The foregoing aspects and many of the advantages of the present invention will be more appreciated and better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

Fig.1

[0028] Fig. 1 shows an illustration of the offshore geothermal platform relative the offshore drilling and production platform and wells.

[0029] Fig. 2 shows a block schematic of a typical electric power production using an Organic Rankine Cycle (ORC) system.

[0030] Fig. 3 shows a block schematic of simultaneous oil and power electricity production.

[0031 ] Fig. 4 shows an illustration of the geothermal powerplant with means for charging electric powered vessels and replacement of batteries.

[0032] Fig. 5 shows an illustration of the geothermal powerplant, charging station and hotel.

Description of Embodiments

[0033] Fig. 1 shows the offshore installation according to the invention comprising the geothermal platform 101 and a drilling platform installation for extracting hydrocarbons 102. The installations may be supported on structures placed on the seabed or installed on floating structures. Floating structures for platform 101 are preferred as it then easily can be constructed a dock by a side and then towed or steamed by own propulsion to a side next to a drilling platform 102. It may then also be easily moved to other sites if required. Platform 102 have drilled wells into the geological structures below the seabed and into well 110 where there are hydrocarbon (oil, gas) and water resources 1 1 1 and 1 12.

[0034] As the well 1 1 1 is emptied of hydrocarbons, it will be filled with water. Platform 102 pumps the liquids through pipes 120 to surface. Oil, gas and water is separated, as disclosed in Fig 2, and hot water is pumped into a facility for geothermal energy.

[0035] When the well is empty of hydrocarbons, separation process will stop. The hot liquid (water) of the ORC may be drawn from several wells or through several wells where the adjoining pipes are drilled.

[0036] As illustrated in fig 1 , a geothermal powerplant 101 is located on a platform next to the drilling platform 102; powerplant 101 generates energy by using of the Organic Rankine Cycle (ORC) 104, as shown in Fig. 3.

[0037] Hot liquid (water) is pumped out from platform 102 to platform 101 through the pipes 121 to the ORC facility 104. For cooling in this process, cold water is pumped through pipes 122 directly from the colder sea water. The seawater is retained in a closed loop and returns to the sea, 123. The hot liquid from the well is also retained in a closed loop that is not mixed with the hot working fluid within the ORC, and is returned to the pipes 124 to the drilling platform 102 and pumped back in to well 1 10 (aquifer) via pipes 126.

[0038] Fig. 2 illustrates the powerplant within the invention utilizing an ORC system 201 . Hot liquid 202 is drawn from well 203, 1 10. The hot liquid passes through heat exchanger 206 where the internal working fluid 208 is boiled. The heat from the liquids drawn from the wells exceed 100 °C and therefore evaporates directly the working fluid 208.

[0039] The vaporized internal working fluid 208 flows through the turbine 210, which drives a generator 212 to produce electricity 214. Condenser 21 1 converts the gas into liquid as it meets the cooling fluid 209 in the heat exchanger. The cold working fluid is cold seawater. No big cooling towers or energy is therefore needed for the cooling as is required on land.

[0040] The internal working fluid 208 is moved through the cold and hot heat exchangers, 208/21 1 in a closed loop. [0041] Fig. 3 shows an illustration for oil, gas and water separator 301 of which will be part of the drilling platform 102 during a simultaneous hydrocarbon and electric power production; as it will separate oil and water during production of oil. This separator 301 system is connected to the ORC 104. Liquid 302 (202) is pumped into the separator 301 whereas oil is run through a cooler 304 cooled by seawater 305. The oil is then stored for further shipment 306. The water 306, separated from oil (still containing some oil particles) is run through a purifier 308 and then over to the ORC 104 and heat exchanger 206 (fig. 2) before reinjected 314 to reservoir 110. The separated oil 307 is stored in 303. 310 illustrate the means for compression and storage of gas 311 and burning of excess gas 312.

[0042] Within the invention, there are therefore two options for hot water supply:

[0043] - During petroleum production after the oil-water separation and before the water is re-injected into the reservoir.

[0044] - Production of water from reservoir after end of hydrocarbon production.

[0045] The wells are typically at 2000-5000 metres deep below the seabed 113 and the liquids (oil/water) hold temperatures from 70- 180 °C.

[0046] To produce 20MW it will demand an ORC power plant of 5000m2 and a total weight about 1000 tons. Two levels of ORC on one platform could produce up to 40MW.

[0047] Offshore oil fields with a high number of wells and high reservoir temperature are well suited for geothermal power production. For example, in the North Sea, the installations of Ula, the liquids in wells hold 150 °C. The potential here is 12MW per well pair, total 13 well pairs = 156 MW. From Eldfisk temperatures of liquids hold 160 °C with a potential of 14MW per well pair, total 30 well pairs = 420 MW. This power output is only possible after oil production has ceased.

[0048] During oil production, the power output is less. Still the hot water after oilwater separation is used. As example from Ekofisk: the temperature of liquid can hold 130°C. Max water production is estimated to 38,000m3/day, the power potential 21 MW/day.

[0049] At Statfjord; temperature 100°C, max water production 80,000m3/day, and power potential 27MW/day. [0050] The electricity produced is used by the whole plant, and to other offshore or onshore installations and to the whole PowerGrid for export of electricity.

[0051] The offshore geothermal powerplant 101 will also serve as charging station for electrically powered vessels. Ell’s Emission Trading System (ETS) may include the world’s fleet of ships which therefore will have to be electrified and a charging station out at sea will be of demand. This will also save steaming time to port for charging for vessels which does not need to go to port.

[0052] Fig. 4 shows the powerplant 101 with means for charging electric powered vessels and replacement of batteries (fuel cells). The platform will have an ORC 104 which produces power to one or more charging units 402 for charging of batteries 403 which are stored on the platform or batteries 505, 506 on board vessels 406,407. Along with living accommodation for the workers, there will also be a hotel 410 for all services for short- and long-term visitors. As the platform will function as a charging station and hotel 401 (101 ), it can serve the needs for vessels like oil tankers and off shore service vessels, trawlers, passenger ships (ferries/cruise ships) and smaller boats and vessels, like speedboats, rescue vessels, fishing and leisure boats.

[0053] The station 401 will provide a service 412 for replacing empty batteries with charged batteries, especially for vessels with huge powerpacks, which does not want to wait for a recharge. When the station 401 connected with an operational drilling platform 102 producing oil, oil tankers run on electricity 409. They can have their batteries charged 416 when loading oil 418.

[0054] Electrification is being introduced into the aircrafts and ones might soon be seen helicopters run on by electricity. The installation 102 and platform 101 and station 401 will have helicopter decks 420 with charging facilities.

[0055] Fig. 5 shows another illustration of the invention whereas the geothermal platform 101 is shown with two ORC units 104’ and 104”, and the means 412 for changing batteries 403 and 404 are illustrated by crane 512.

[0056] Charging facilities for vessels 405, 406 are denoted numeral 402. On top of hotel 410 is located a helicopter deck 420 with charge unit 402’. The platform and station 101/401 will have storage rooms and an infrastructure for handling of the batteries and the changing of batteries on vessels. This will involve a system where batteries have a range of standard sizes and performance. The captain of any vessel would have to make sure to order a replacement in advance. The replacement itself would require a transport and lifting system from the ship storage, which would require the use of conveyor belt system and/or trucks and set up of cranes.

[0057] The platforms and installation will have systems for securing against fire and extinguishing of fire; this will involve the use of prior art from the offshore oil industry. However, batteries can explode, both on platforms and on vessels. On station, the batteries will be stored in separate rooms from the other installation, and be storage in separated cells of limited sizes.

[0058] The existing installations for the extraction of hydrocarbons may be converted from drilling platforms to a geothermal power plant, if the size and structures allows the size and weight, and in such an event, a specially built platform for the ORC will not be needed. [0059] It should be understood that the system here disclosed for offshore geothermal energy production is easily converted into an onshore power plant with access to cold water.

Claims

1 . A system and method for utilizing geothermal energy from existing offshore oil and gas wells for production of electric power, comprising existing offshore installations (102) including oil/gas/hydrocarbon wells and means for an offshore geothermal power plant (101 ), characterized by:

- The said power plant (101 ) located next to the mentioned installations (102).

- And where power plant (101 ) utilizes an organic rankine cycle (ORC) (104) with a closed loop working fluid (208).

- Whereas the heat exchanger (206) is fed by hot liquid (202) directly from wells (1 10) and where the condenser (21 1 ) is fed by cold seawater (209). Neither hot liquid (202), nor seawater, (209) is in contact with the internal working fluid, but returned to said well and sea, respectfully.

2. A system and method according to claim 1 , whereas the installation (102) extracts hot fluid (202) from the well (101 ) to the ORC (104); whereas after the heat exchange the fluid (202) is returned from the ORC to the installation (102), which then retunes the fluid back into the wells (1 10) to the ORC by returning the seawater after condensation, to the sea.

3. A system and method according to claim 1 , whereas the hot liquid for the ORC is water and is supplied after an oil-water separation of the liquid from well (1 10), and before the water is injected back into the well/reservoir (1 10).

4. A system and method according to claim 3, whereas the installation has a system for oil/gas and water separation where oil and gas is produced for storage and the water (309) used by the ORC for powerproduction.

5. A system and method according to claim 1 , whereas the installation has a system for oil/gas and water separation and purifier of water (309) used by the ORC for power-production.

6. A system and method according to claim 1 , whereas the hot liquid (202) for the ORC is water from production of water from the well after end of hydrocarbon production within the wells (110, 112).

7. A system and method according to claim 1 , whereas the powerplant (101 ) is built on a floating structure, steamed by own propulsion or towed to any required location.

8. A system and method according to claim 1 , whereas the powerplant (101 ) produces electricity for:

- Export to offshore or onshore PowerGrid

- Use by the installation (102) or other offshore installations.

- Charging and storing of batteries.

- Charging of offshore vessels.

9. A system and method according to claim 1 , whereas the powerplant (101 ) produces electric power and comprises on platform a charging station and means for marine services as:

- Charging of electric powered seagoing vessels,

- Changing of batteries of electric powered seagoing vessels,

- Charging of electric powered aircraft’s batteries/tanks.

- Hotel accommodation facilities for workers and travelers.

10. A system and method according to claim 1 , whereas the powerplant (101 ) produces electric power on platform and has a charging station which can provide charging to electric powered oil tankers while anchored at installation (102) which bunkers for oil, and for charging of electric powered service vessels, associated with the operations at the plant (101 ) or installation (102).

11 . A system and method according to claim 1 , whereas the powerplant (101 ) produces electric power to a remote marine activity platform including: - A charging station for charging of electric powered seagoing vessels, charging of electric powered aircraft’s batteries and hotel accommodation facilities for workers and travelers.