Monitoring system of temporarily abandoned subsea wells without wet christmas tree, and method of installation and monitoring of temporarily abandoned subsea wells without wet christmas tree employing said system

Abstract

Which basically consists of the application of a hydraulic connector (1), equipped with a subsea control module (5), replacing the WCT, which locks and seals in the H4 profile of the BAP high-pressure housing, becoming part of the secondary PBA, and whose sealing (VX or VGX ring) will be tested periodically.

Description

"MONITORING SYSTEM OF TEMPORARILY ABANDONED SUBSEA WELLS WITHOUT WET CHRISTMAS TREE, AND METHOD OF INSTALLATION AND MONITORING OF TEMPORARILY ABANDONED SUBSEA WELLS WITHOUT WET CHRISTMAS TREE EMPLOYING SAID SYSTEM" FIELD OF THE INVENTION

[0001] The present invention belongs to the field of systems and methods formonitoring temporarily abandoned subsea wells, and more specifically for monitoring the integrity of primary barrier assemblies (PBA), including cement, packer, production column and its components, DHSV and plug of the production tubing, and secondary, including cement, production casing, wellhead, BAP (“high-pressure wellhead housing), tubing hanger and tubing hanger plug. BACKGROUND OF THE INVENTION

[0002] The abandonment of oil wells is a critical and complex step in a well'slife cycle. This phase involves strategic and operational decisions that ensure safety, economic viability, and environmental protection. In this context, understanding the reasons and methods of temporary and permanent abandonment is essential for operators and regulators. The absence of a Wet Christmas Tree (WCT) during temporary abandonment can introduce a number of challenges and risks, which need to be managed efficiently to minimize adverse impacts.

[0003] The exploration phase is the first stage in the development of an oil well.It involves the identification of promising sites through geological and geophysical studies. Techniques such as 2D and 3D seismic, gravimetry and magnetometry are employed to map underground structures and identify potential hydrocarbon reservoirs. During this phase, exploratory soundings are carried out to confirm the presence of oil or gas.

[0004] After a promising site is identified, the drilling phase begins. This stepinvolves drilling the well with specialized equipment, passing through several layers of rock until it reaches the oil reservoir. Advanced drilling equipment, such as diamond drill bits and directional systems, are utilized to ensure drilling accuracy and efficiency. The casing is installed in several steps to stabilize the well and prevent cave-ins.

[0005] After drilling, the evaluation phase is crucial to determine thecommercial viability of the reservoir. Formation tests, such as the formation pressure test and the flow test, are performed to assess the productivity of the well. Profiling tools, such as electrical and imaging logs, provide detailed data on reservoir properties. Based on this data, reservoir engineers model the behavior of the field and make estimates on the recoverable amount of hydrocarbons.

[0006] If the reservoir is considered commercially viable, the development andproduction phase begins. This step involves the installation of production infrastructure, such as production platforms, pipelines, and processing facilities. Primary, secondary, and tertiary recovery techniques are implemented to maximize oil extraction. Production management includes maintaining reservoir pressure, separating hydrocarbons, and managing produced water and other by-products.

[0007] When the well is no longer economically viable, it enters theabandonment phase. This phase can be temporary, with the expectation of future reactivation, or subsequent permanent abandonment, sealing the well definitively. Abandonment must be conducted in a manner that ensures safety and minimizes environmental impacts. Strict sealing and monitoring procedures are implemented to prevent hydrocarbon leaks.

[0008] Temporary abandonment is a common practice when there is anexpectation that the well can be reactivated in the future or later abandoned permanently. This decision can be influenced by a variety of factors, including fluctuations in oil prices, technological advances that allow for more efficient extraction, or regulatory changes. During temporary abandonment, the well is sealed securely, but in a way that allows reopening and reactivation with minimal costs and effort and also a subsequent definitive abandonment. Procedures such as installing mechanical plugs and injecting preservation fluids are common to ensure the integrity of the well during downtime.

[0009] When a well is deemed not viable for future production, it is abandonedpermanently. This decision is made after a thorough assessment that takes into account economic viability, safety and environmental impacts. Permanent abandonment involves the definitive sealing of the well with cement and other sealing materials to prevent any fluid migration. This process must comply with strict regulatory standards to ensure that the well does not pose future risks.

[0010] Fluctuations in the price of oil are one of the main reasons for temporarywell abandonment. When prices drop significantly, production can become economically unviable. In such cases, companies may choose to temporarily seal the well, pending a recovery in market prices. This strategy allows operators to avoid operating costs during periods of low profitability, while retaining the option to reactivate production when economic conditions improve.

[0011] Technical problems can also lead to temporary abandonment of wells.Damage to the well, such as casing collapses or issues with the integrity of the cement, can require significant time and resources to resolve. In some cases, the technology needed to resolve these problems may not be immediately available, justifying a temporary abandonment while solutions are developed.

[0012] Changes in regulations may require operators to temporarily haltproduction to comply with new standards. Environmental issues, such as the need to conduct environmental impact studies or comply with remediation requirements, can also result in a temporary abandonment. In these situations, operators can temporarily seal the well until all regulatory and environmental compliances are achieved.

[0013] Another very common reason for temporary abandonment is thepostponement of definitive abandonment to optimize the allocation of the resources necessary for abandonment, especially the hiring of rigs.

[0014] The Wet Christmas Tree (WCT) is a set of valves installed at thesubmerged wellhead, responsible for controlling the flow of oil and gas to the surface. This equipment is crucial for the safe and efficient operation of submerged wells. It is called "wet" because it is designed to operate on the seabed. WCT includes master valves, flow control valves, sensors, and other components that allow remote monitoring and control of the well.

[0015] In some cases, a well may be temporarily abandoned withoutinstallation or maintenance by the WCT. This can occur due to WCT or control system integrity issues. In these cases, it may be necessary to remove the WCT and replace it with barriers in the well. During temporary abandonment without WCT, alternative well sealing and control procedures are implemented to ensure the safety and integrity of the well.

[0016] The absence of WCT can compromise the control of the flow ofhydrocarbons, increasing the risk of leaks and explosions. Without the proper control equipment, it can be difficult to quickly detect and respond to issues such as overpressure or leaks. This represents a significant risk to the safety of workers and the integrity of the well.

[0017] Oil and gas spills resulting from the lack of proper control can causesevere damage to marine and coastal ecosystems. Hydrocarbon spills can affect marine life, water quality, and coastal habitats, resulting in long-term environmental impacts. Remediation of such leaks can be complex and costly, requiring significant efforts to restore the affected environment.

[0018] Lack of proper control during temporary abandonment can result inhigher costs when the well needs to be reactivated or permanently sealed. Issues such as leaks or damage to the well during downtime may require costly repairs and additional procedures to ensure the safety and integrity of the well.

[0019] The Well Integrity Management System (WIMS) is a set of policies,processes, and technologies implemented to ensure the integrity and safety of oil and gas wells throughout their life cycle. The WIMS covers from the drilling and production phase to temporary or permanent abandonment, requiring continuous monitoring of the condition of the well and its safety barriers.

[0020] Well integrity refers to a well's ability to contain and control undergroundfluids, preventing leaks that could cause safety, environmental, and production risks. Maintaining the integrity of the well is crucial to prevent catastrophic incidents, such as explosions and oil spills, which can have serious consequences.

[0021] Well-barrier envelopes are multi-layered systems of protection installedin a well to ensure its integrity and safe containment of underground fluids. These assemblies include various physical barriers, such as coatings, cementations, and mechanical plugs, which work together to prevent fluid migration. The main components of barrier assemblies include:

[0022] . liners: steel pipes installed in the well to stabilize the walls and preventcollapses;

[0023] . cementing: sealing material pumped between the casing and the wellwall, or between two casings, to create a solid barrier;

[0024] . mechanical plugs: devices installed inside the casing or productiontubing to block the flow of fluids, and

[0025] . cement plugs: cement columns placed inside the production casing topermanently seal certain sections of the well.

[0026] Several methods can be employed to monitor the integrity of elementsof the barrier assemblies in temporarily abandoned wells. These methods include:

[0027] . pressure monitoring: pressure sensors are installed to detect anyvariation that may indicate leaks or failures in the barriers;

[0028] . temperature monitoring: temperature sensors help identify changesthat may suggest fluid migration;

[0029] . remote visual inspection: cameras and remote inspection devices areused to check the physical condition of the barriers;

[0030] . barrier integrity testing: periodic testing, such as pressure testing andleak testing, is performed to ensure that the barriers are functioning properly.

[0031] The technologies used in well integrity monitoring include:

[0032] . smart sensors: Advanced sensors that provide real-time data on thecondition of the well and its barriers;

[0033] . remote monitoring systems: digital platforms that aggregate andanalyze sensor data, enabling continuous monitoring and early detection of problems, and

[0034] . profiling tools: equipment that performs detailed measurements of theinternal conditions of the well, such as casing integrity and cement quality.

[0035] The WIMS also includes rapid response protocols to handle anyindication of barrier failure. This may include mobilizing intervention teams, conducting emergency repairs, or reassessing the condition of the well to determine the need for furthercontrol measures.

[0036] The temporary abandonment of a well without WCT can present severalchallenges and risks that need to be properly managed to ensure the safety and integrity of the well, such as risks of leaks, since, due to the absence of WCT, an additional layer of barriers is lost, increasing the risk of oil, gas, or water leakage from the well, which may compromise the integrity of the plugs, whether cement or mechanical, that have not been installed or maintained correctly, and there may be failures in the seals, which can result in leaks.

[0037] Corrosion and degradation, due to the exposure of the wellhead andother components to salt water, oxygen and other environmental elements, can compromise the integrity of the well, and without WCT, which offers additional protection against corrosion through its anodes, the regular maintenance of exposed components becomes even more critical.

[0038] The absence of the WCT may hinder continuous monitoring of the well,since monitoring systems integrated with the WCT will not be available, and maintenance and repairs may also be more complicated and risky without the WCT structure, which facilitates access to critical components of the well.

[0039] If the well needs to be reactivated, the absence of the WCT can makethe process more complex, as it requires the installation of new equipment and additional safety checks, which can be time-consuming and expensive, and during temporary abandonment, critical components may suffer damage or degradation, making reactivation even more difficult and increasing the risk of operational failures.

[0040] Undetected or poorly managed leaks can contaminate soil andgroundwater, causing significant environmental damage, and failure to comply with environmental regulations, due to shortcomings in temporary abandonment, can result in severe fines and penalties.

[0041] Thus, to mitigate these issues, it is essential to follow strict planning andexecution practices, which include ensuring that cement and mechanical plugs are installed correctly and tested to ensure proper sealing; perform periodic inspections and maintenance to identify and correct corrosion issues, degradation, and other potential failures; apply anti- corrosion coatings and use corrosion-resistant materials in the exposed parts of the well; provide well-defined emergency plans to deal with leaks or other incidents, including procedures for quick repairs and containment measures, and, most importantly, implement remote monitoring system and method or regular visits to check the integrity of the well and detect leaks or other anomalies. BACKGROUND OF THE ART

[0042] The state of the art is already known in the patent documentUS2013 / 0299165 which deals with a system and method for long-term monitoring of abandoned wells, which proposes the formation of a series of barriers within a formation and within a well casing to prevent leakage of materials from the well, said formation barriers being formed within the formation, and annular at the site of perforations in the casing, with one or more sensors formed within the barriers to monitor the conditions around the barriers over long periods of time, such sensors being configured to measure the conditions around one or more barriers during the formation of one or more barriers and over long periods of time after the formation of one or more barriers, where sensors are configured to include, or be connected to, one or more power sources that allow the sensors to operate for long periods of time, and one or more power sources may be included in the sensors or external to the sensors, which remotely supply power to the sensors, and may for example include long-life batteries, power supplies that draw energy from the environment, inductive power sources that produce power from received electromagnetic signals, and external power supplies that are electrically coupled to sensors; sensors may also include components that allow monitoring systems to communicate with sensors over long periods of time, electronic circuitry that allows monitoring systems to communicate with and / or wirelessly with sensors in order to monitor conditions in the well, sensors may be configured with nanoparticle material that becomes an integral part of the formation barrier or casing barrier.

[0043] Although this document, and others of the art, provide for a system andmethod for long-term monitoring of abandoned wells, to avoid leakage of materials from the well, the provision of an additional barrier and the monitoring of the two solidary assemblies of well barriers is not foreseen, and this additional barrier can be periodically tested in temporarily abandoned wells with a tubing hanger, allowing the double-sealing valve of the tubing hanger to also be tested, through its own sensors, without depending on sensors installed in the well.

[0044] Thus, it is desirable to propose a system and method for monitoringtemporarily abandoned subsea wells without WCT that overcomes the limitations of the current state of the art. SUMMARY OF THE INVENTION

[0045] The main objective of this invention is to provide a system that allowsmonitoring the integrity of the primary (cement, Packer, production tubing and its components, DHSV and production tubing plug) and secondary (cement, production casing, wellhead, BAP, tubing hanger and tubing hanger plug) solidary assemblies (PBA).

[0046] Another objective of this invention is to provide a hydraulic connectorthat locks and seals in the H4 profile of the BAP high-pressure housing, becoming part of thesecondary PBA, whose sealing (VX or VGX ring) will be tested periodically.

[0047] Another objective of the present invention is to provide a submarinecontrol module coupled, through a flange, at the top of the hydraulic connector, equipped with pressure sensors that allow the reading of pressure growth versus time to measure any leakage through the DHSV, through the Packer, the production tubing and its components or the production liner.

[0048] Another purpose of the present invention is to provide a motor and pumpassembly in the subsea control module to test the sealing of the hydraulic connector.

[0049] Another objective of this invention is to provide the submarine controlmodule with an ROV panel with a hot stab interface, so that the test can be done with the aid of ROV.

[0050] Another objective of the present invention is to allow the submarinecontrol module, through ROV-operated valves, to relieve the pressure to a hydrocarbon tank installed on the seabed.

[0051] Another objective of the present invention is to equip the subsea controlmodule with a hot stab interface to allow locking and unlocking the hydraulic connector with the ROV

[0052] Another objective of this invention is to provide the submarine controlmodule with an acoustic modem that allows communication and data sending to an ROV, AUV, USV or buoy.

[0053] Another objective of the present invention is to provide the submarinecontrol module with other means of communication.

[0054] Another objective of the present invention is to propose a method ofinstallation and use of the submarine control module and hydraulic connector assembly, from a support vessel. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIGURE 1 illustrates a schematic view of the hydraulic connectorinstalled at the wellhead, replacing the WCT, also illustrating the pressure monitoring points of the temporarily abandoned well. PREFERRED DESCRIPTION OF THE INVENTION

[0056] Broadly speaking, a system for monitoring abandoned wells of thepresent invention consists of the application of a hydraulic connector (1), replacing the WCT, which locks and seals in the H4 profile of the BAP high-pressure housing, and this connector becomes part of the secondary PBA and its sealing (VX or VGX ring), which should be periodically tested.

[0057] The hydraulic connector provides a lower stab that fits and seals theproduction bore (2) of the tubing hanger (3), similar to the WCT connector; the connector also has a stab that fits and seals in the annulus bore (4) of the tubing hanger, and when the tubing hanger is equipped with DUAL-SEAL VALVE , this stab opens this valve, allowing communication with the annular, and, alternatively, when the tubing hanger is equipped with DUAL-SEAL VALVE , the hydraulic connector can dispense with the use of annular stab, and, in this case, the pressure will be measured at point A, called Spool Cavity, to check for leakage through the annular, the advantage of this alternative being the fact that it can remove the hydraulic connector with the guarantee that the DUAL-SEAL VALVE is sealing, and if there is an annular stab in the hydraulic connector, the DUAL-SEAL VALVE closes after the hydraulic connector is removed, without being able to test it.

[0058] Another alternative is to equip the hydraulic connector with a retractableannular stab, so that it is possible to test the DUAL-SEAL VALVE , from top to bottom, before unlocking the connector, in this case, there must be, at point B, a motor / pump assembly in the subsea control module (5), which is coupled, by means of a flange, at the top of the hydraulic connector, equipped with pressure sensors that allow the reading of the pressure at points C and D.

[0059] The measurement of pressure versus time growth at point C allows thedetection of any leakage from the well, through the DHSV, and this measurement is compared with an acceptable value to determine the integrity of the barriers.

[0060] The measurement of pressure versus time growth at point D allows thedetection of any annular leak, which can be through the Packer, the production tubing and its components, or the production casing (6).

[0061] This measurement is compared with an acceptable value to determinethe integrity of the barriers.

[0062] The submarine control module can also be equipped with an ROVpanel, with a hot stab interface, so that the test can be done with the aid of ROV.

[0063] The subsea control module allows, through ROV-operated valves, therelief of pressure at points A, C and D, for a hydrocarbon tank installed on the seabed, and this operation is routinely used in the dissociation of hydrates from subsea equipment, thus, when the pressure at points A, C or D is equal to the static pressure at the wellhead, there will be no pressure growth at these points, even if there is a leak in the well barriers.

[0064] The subsea control module is also equipped with a hot stab interfacethat allows the locking and unlocking of the hydraulic connector with ROV, and alternatively, this operation can be done through the pressurization and depressurization of hydraulic fluid using the motor and pump of the subsea control module itself.

[0065] The submarine control module is also equipped with an acousticmodem that allows communication and sending data to an ROV; AUV; USV or buoy, and communication with the buoy can be done through an electric cable.

[0066] Other means of communication can also be used, such as, for example,laser.

[0067] The cable installation method, from a support vessel, for monitoringthrough the submarine control module and hydraulic connector assembly, is carried out through the following steps:

[0068] a) remove the corrosion layer with ROV;

[0069] b) install the cable system, with a support boat;

[0070] c) sit and lock the hydraulic connector on top of the BAP high-pressurehousing (7) with the aid of ROV;

[0071] d) test the seal of the VX or VGX ring between the connector and theBAP high-pressure housing;

[0072] e) test the operation of the communication and the system with the aidof ROV; and

[0073] f) measure the pressure growth versus time at point C, to detect anyleakage from the well, through the DHSV, and this measurement is compared with an acceptable value to determine the integrity of the barriers;

[0074] g) measure the pressure versus time growth at point D to detect anyannulus leakage, which may be through the Packer, the production tubing and its components, or the production lining (6), this measurement being compared with an acceptable value to determine the integrity of the barriers, and (h) relieve the pressure at points A, C and D, through valves of the subsea control module allowing, operated by ROV, to a hydrocarbon tank installed on the seabed, when the pressure at points A, C or D is equal to the static pressure at the wellhead, so that there is no pressure growth at these points, even if there is a leak in the well barriers.

Claims

AMENDED CLAIMS received by the International Bureau on 2 December 2025 (02.12.2025)1 .A monitoring system for temporarily abandoned subsea wells without wet Christmas tree, CHARACTERIZED by the fact that it consists of a hydraulic connector (1 ), designed to be installed in replacement of the WCT, which locks and seals in the H4 profile of the BAP high-pressure housing, where said hydraulic connector (1 ) becomes part of the solidary set of the secondary barrier; a subsea control module (5) coupled, by means of a flange, on top of the hydraulic connector; the said subsea control module (5) equipped with pressure sensors to monitor the integrity of the well barriers, such as the subsea control valve (DHSV) and the production packer.

2. The system according to claim 1 , CHARACTERIZED by the fact that the hydraulic connector provides, at the bottom, a stab that fits and seals the production hole (2) of the tubing hanger (3), similarly to the WCT connector, the connector also having a stab that fits and seals in the annulus bore (4) of the tubing hanger, and when the tubing hanger is equipped with DUAL-SEAL VALVE , this stab opens this valve, allowing communication with the annular.

3. The system according to claim 2, CHARACTERIZED by the fact that, when the tubing hanger is equipped with DUAL-SEAL VALVE, the hydraulic connector dispenses with the use of annular stab.

4. The system according to claim 3, CHARACTERIZED by the fact that the pressure is measured at point A, called Spool Cavity, to check for leakage through the annular, being able to remove the hydraulic connector with the guarantee that the DUAL-SEAL VALVE is sealing.

5. The system according to claim 4, CHARACTERIZED by the fact that, if there is an annular stab on the hydraulic connector, the DUAL-SEAL VALVE closes only after the hydraulic connector is removed.

6. The system according to claim 5, CHARACTERIZED by the fact that the hydraulic connector is equipped with a retractable annular stab to test the DUAL-SEAL VALVE from top to bottom before unlocking the connector.

7. The system according to claim 6, CHARACTERIZED by the fact that there is a motor / pump assembly at point B of the subsea control module (5).

8. The system according to claim 1 , CHARACTERIZED by the fact that the subsea control module (5) is equipped with pressure sensors that allow the pressure to be read at points C and D.

9. The system according to claim 8, CHARACTERIZED by the fact that themeasurement of pressure growth versus time at point C allows the detection of any leakage from the well, through the DHSV, this measurement being compared with an acceptable value to determine the integrity of the barriers.

10. The system according to claim 8, CHARACTERIZED by the fact that the measurement of pressure growth versus time at point D allows the detection of any leakage of the annular, which may be through the Packer, the production tubing and its components, or the production casing (6).11 . The system according to claim 9 and 10, CHARACTERIZED by the fact that the measurement is compared with an acceptable value to determine the integrity of the barriers.

12. The system according to claim 1 , CHARACTERIZED by the fact that the subsea control module (5) is equipped with a motor and pump to test the seal of the hydraulic connector at point B.

13. The system according to claim 12, CHARACTERIZED by the fact that the subsea control module (5) can be equipped with an ROV panel, with a hot stab interface, so that the test can be done with the aid of an ROV.

14. The system according to claim 1 , CHARACTERIZED by the fact that the subsea control module (5) allows, through ROV-operated valves, the relief of pressure at points A, C and D, to a subsea hydrocarbon collection tank.15 The system according to claim 14, CHARACTERIZED by the fact that, when the pressure at points A, C, or D is equal to the static pressure at the wellhead, there will be no pressure growth at these points, even if there is leakage at the well barriers.

16. The system according to claim 1 , CHARACTERIZED by the fact that the subsea control module (5) is equipped with a hot stab interface that allows the locking and unlocking of the hydraulic connector with ROV.

17. The system according to claim 16, CHARACTERIZED by the fact that, alternatively, this operation is done through the pressurization and depressurization of hydraulic fluid using the engine and pump of the subsea control module itself (5).

18. The system according to claim 1 CHARACTERIZED by the fact that the submarine control module (5) is equipped with an acoustic modem that allows communication and the sending of data to an ROV; AUV; USV or buoy.

19. The system according to claim 18, CHARACTERIZED by the fact that communication with the buoy is done through an electric cable.

20. The system according to claim 18, CHARACTERIZED by the fact that communication with the buoy is done through other means of communication can also be used, such as, for example, laser.21 .A method of installation and monitoring of temporarily abandoned subsea wellswithout a wet Christmas tree, from a support vessel, for use with the system as defined in claims 1 to 20, CHARACTERIZED by comprising the following steps: a) remove the corrosion layer with ROV; b) install the cable system, with a support boat; c) place and lock, with the aid of ROV, the hydraulic connector on top of the BAP high-pressure housing (7); d) test the seal of the VX or VGX ring between the connector and the BAP high- pressure housing; e) test, with the aid of ROV, the operation of communication and the system; f) measure the pressure growth versus time at point C, to detect any leakage from the well, through the DHSV, and compare it with an acceptable value to determine the integrity of the barriers;(g) measure the pressure versus time growth at point D to detect any leakage of the annular through the Packer, the production tubing and its components, or the production lining (6), and compare this measurement with an acceptable value to determine the integrity of the barriers, and(h) relieve the pressure at points A, C and D, through valves of the subsea control module allows, operated by ROV, to a hydrocarbon tank installed on the seabed, when the pressure at points A, C or D is equal to the static pressure at the wellhead, so that there is no pressure growth at these points, even if there is a leak in the well barriers.

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