Patent Description:
Most of the offshore oil production in Brazil flows through flexible lines. The reserves in the pre-salt scenario contain a large quantity of CO2 in the oil flows that, along with other gas components, permeate through the polymer sealing layer as far as the carbon-steel layers in the annular space of the flexible line. These wires are isolated from the outside environment by a polymer layer, known as the external layer.

Determining the actual state of the annulus of a flexible line is a challenge in the oil industry, in particular in the undersea production system projects in the pre-salt layer of the Santos Basin, which use production systems with different types of undersea lines, including rigid lines, hybrid lines (comprising combinations of rigid and flexible lines) and mainly flexible lines, which make up more than <NUM>% of the total lines.

A lack of watertightness of the external layer of a flexible line causes the ingress or invasion of water into the annular space. This creates the conditions enabling the stress-corrosion mechanism caused by the presence of CO2, causing not just corrosion but also cracking with the possibility of breakage of these metal wires in the traction layers, with the consequent loss of the containment of these lines.

Since flooding of the annulus is only observed in a small fraction of lines, and this phenomenon significantly reduces calculated service life, potentially resulting in unexpected catastrophic failures.

It is essential to identify which lines are flooded so as to prevent the unnecessary collection (removal) of lines in which the annulus is dry, and to avoid interruptions to operation of the network of lines in an operating unit.

The invention relates to a device (equipment) and a method for measuring the pressure value inside the annulus of a flexible line in operation, to directly determine whether this annulus is watertight or otherwise. The invention makes it possible to directly check watertightness of the annulus of the line by measuring the pressure in the annulus using a safety valve in the connectors on the lines in operation. Reading the pressure in the connectors at the two ends of each section makes it possible to distinguish between flooded and dry states.

The invention uses a non-destructive testing technique given that said technique has to overcome the technical difficulties caused by the physical multi-layer composition of the flexible lines, primarily as a result of comprising different materials.

The invention makes it possible to collect fluid or gas samples from inside the annulus for subsequent analysis, which helps to distinguish between condensate and seawater, as well as assessing the composition and corrosiveness of the annulus, in the event of fluid being detected.

The invention can be used regardless of the number of layers and in oil production lines, gas injection lines and gas-lift lines. In addition to this, the operating water depth does not affect the efficiency of this technology since, unlike tubular-body inspection technologies, this technology checks the condition of the annulus through the connector, which is not liable to be deformed or affected by hydrostatic pressure.

The technologies available on the market have usage limitations relating to the number and thickness of the layers of the line, the operating water depth, and identifying, where applicable, the source of water in the annulus. There are patent documents in the prior art (listed below) that provide solutions for the aforementioned problems, albeit using completely different techniques.

The application published as BRPI0907411 discloses a technique for monitoring and measuring the quantity of water that has invaded the annulus. The system and method analyze and determine the volumetric composition of discharge gases, as well as detecting water flooding. The invention also measures pressure and temperature and gas flow in the annulus via a discharge valve. The invention is intended to resolve problems such as measuring composition and volume, for example using gas chromatography and mass spectrometry, etc., with samples collected and transported to a laboratory. Accordingly, the present invention is intended to speed up measurement by placing analyzers on the line with a processing unit and recording using specific software for interpreting the information. Patent <CIT> discloses a system and method for detection of fluid invasion in an annular space of a pipe structure. The system includes a thermal element and a temperature sensing element placed in the vicinity of each other in the annular space of the pipe structure. A thermal signal is generated by the thermal element. The temperature sensing element is connected to a monitor that monitors and processes the thermal signal. As the thermal signal changes when conducted through different types of fluids, the invasion of an annular space by seawater that normally contains oil or gas may be reliably detected.

Patent <CIT> discloses a method for pipeline leak detection in which a vacuum is maintained in the annulus of a pipe-in-pipe flowline with a vacuum pump having a discharge reservoir which is monitored for the appearance of water and hydrocarbon vapors. In another aspect of the invention, pipeline (undersea line) leak detection is accomplished through maintaining a gas at a nominally constant pressure in an annulus and monitoring the annulus for pressure increase indicative of water or product intrusion into the annulus.

The invention therefore relates to a system that not only identifies the presence of water in the annulus of a flexible line in operation, but also quantifies the pressure in the annulus at any depth.

As detailed below, the present invention is intended to provide a solution to the prior art problems described above in a practical and efficient manner.

<CIT> discloses the technical features of claim <NUM> but does not disclose that a connector of the line is grasped and the cylinder sealed against the wall of the recess of a valve.

The present invention is intended to provide a method and equipment (device) for measuring the pressure value inside the annulus of a flexible line in operation, to directly determine whether this annulus is watertight or otherwise.

To achieve the objectives set out above, the present invention provides a system for detecting the watertightness of a flexible line by measuring the pressure in the annulus from a connector of the flexible line including: an ROV that includes an arm element designed to move the main device until the device has engaged in the safety valve of the connector, and more specifically in the recess containing the safety valve, as defined by claim <NUM>.

The invention describes an operating method for the equipment for detecting the water tightness of the annulus of the flexible line to provide a critical analysis of the results, being therefore dependent on the initial and final pressure values indicated before and after movement of the plunger, as defined by claim <NUM>.

Furthermore, the invention may optionally contain a chamber for capturing fluid samples discharged from the annulus by causing the safety valve to open by reducing external pressure.

Furthermore, the device may optionally contain a hexagonal socket for removal of the safety valve or of the plug installed in the connector of the flexible line.

The detailed description provided below makes reference to the attached figures and the respective reference numbers therein.

The descriptions below relate to a preferred embodiment and to two additional optional embodiments expanding the functionality of the main invention. However, as is obvious to any person skilled in the art, the invention is not limited to these embodiments, the matter for which protection is sought being defined by the appended claims.

<FIG> is a schematic view of the system for detecting the watertightness of the annulus of a flexible line from the connector thereof, showing all of the component parts thereof according to the main configuration of the present invention. <FIG> details the main object and the main suggested embodiment.

The invention involves a method for checking the watertightness of the annulus of undersea flexible lines by measuring the pressure of the annulus. This measurement is taken using the safety valve (<NUM>) in the connectors of the flexible lines (<NUM>).

To enable the pressure in the annulus of the flexible lines to be measured in operation, the invention uses a device controlled by a remotely operated vehicle (ROV) (<NUM>).

Said device comprises an assembly in the form of a cylinder (<NUM>) and a plunger (<NUM>) (piston-cylinder arrangement) installed in the recess also containing the safety valve (<NUM>) of the connector of the flexible line (<NUM>). The cylinder (<NUM>) has a sealing system (<NUM>) that provides a seal between the external environment and the front region of the plunger of the cylinder, where the external portion of the safety valve (<NUM>) is located. There is also a pressure gauge (<NUM>) connected to the chamber created between the cylinder (<NUM>) and the plunger (<NUM>) for measuring the pressure in the front region of the cylinder, enabling variations in the external pressure acting on the safety valve (<NUM>) to be determined as the plunger (<NUM>) is moved.

To position the assembly of cylinder (<NUM>) and plunger (<NUM>) and to activate the sealing system (<NUM>) thereof, the invention has a dog-like coupling and anchoring system (<NUM>) controlled by the ROV (<NUM>) that grasps the connector of the flexible line (<NUM>), installing the device in the recess of the safety valve (<NUM>) of the connector of the line (<NUM>) and sealing the cylinder (<NUM>) of the device against the wall of the recess of the valve (<NUM>). The invention is intended to cover any coupling system of the device and activation of the sealing system.

The device can be sealed against the wall of the recess of the valve (<NUM>), ensuring watertightness from the external environment, by energizing polymer or metal rings against the wall and the base of the recess, as well as by opening threads in the wall of the recess or another mechanical device enabling permanent or non-permanent fastening.

The device is then installed and sealed from the external environment. The method for checking the watertightness of the annulus by measuring the pressure in the annulus involves moving the plunger (<NUM>) of the device to cause a pressure drop in the outer portion of the safety valve of at least <NUM> bar, thereby activating this valve (the safety valves of the connectors of the flexible line are activated automatically when the difference between the pressure in the annulus and the external pressure is greater than <NUM> bar). The pressure gauge monitoring the pressure in the device (<NUM>) indicates the pressure at which the valve (<NUM>) opened, thereby revealing the pressure in the annulus.

The method does not necessarily require activation of the valve to determine whether the annulus of the flexible line is watertight. Following the movement of the plunger (<NUM>) to reduce the external pressure of the valve (<NUM>), even if this reduction is not enough to activate the valve, stabilization of the pressure in the pressure gauge at a pressure less than the hydrostatic pressure indicates that the annulus is at a pressure below the hydrostatic pressure, from which it can be inferred that there is no communication between the annulus and the external environment, i.e. that the annulus is watertight.

If the pressure in the pressure gauge (<NUM>) stabilizes at a pressure similar to the hydrostatic pressure, it can be inferred that the pressure in the annulus is close to the hydrostatic pressure, which can be cause by two factors:.

Additionally and not exclusively, the device can include a chamber (<NUM>) for capturing samples of the fluids discharged from the annulus by causing the safety valve (<NUM>) to open in order to reduce the external pressure by movement of the plunger (<NUM>) of the device. As shown in <FIG>, connection with the sampling chamber (<NUM>) can be provided by the connection that engages the pressure gauge (<NUM>) to connect said gauge to the cylinder (<NUM>). In addition to this, the device can contain a hexagonal socket (<NUM>) for removing the safety valve (<NUM>) or the plug (<NUM>) installed in the connector of the flexible line once the device has been sealed against the wall of the recess of the valve (<NUM>) or the plug, in order to measure the pressure of the annulus and to inject fluids or chemical products into the annulus. <FIG> shows the present invention modified (as an alternative embodiment) so that the hexagonal socket (<NUM>) connected to a rod (<NUM>) with a coupling and anchoring structure (<NUM>) designed to be twisted by the handle (<NUM>) and conveyed by the arm of the ROV (<NUM>) to remove the safety valve (<NUM>). Finally, the control chamber (<NUM>) used to control the plunger (<NUM>) and cylinder (<NUM>) system with the liquid ingress is replaced by the chamber (<NUM>) in which operation of the rod (<NUM>) and the hexagonal socket (<NUM>) is enabled, and which is connected to the cylinder (<NUM>).

<FIG> shows how the system and method proposed by the present invention can be used in flexible lines and connectors subjected to high hydrostatic pressures (approximately <NUM> bar) such as in deep-sea applications, without any significant interference in the measurements.

Three practical examples shown in the embodiments in <FIG> are provided to help understand how the invention works. This figure shows a typical layout of an undersea flexible line, and the sections and connectors thereof. The connectors have valves designed to reach up to <NUM> bars above external pressure.

Example <NUM>: <FIG> also shows examples in which four connectors are arranged vertically and three connectors are arranged horizontally. The first two connectors are connected physically together and surrounded by <NUM> bars of static pressure PEST, and the second two connectors are also linked physically together and surrounded by <NUM> bar of static pressure PEST. The reference pressure for analyzing watertightness is different for each array of connectors and sections, and this one refers to the intermediate flexible line (<NUM>). The connectors connect the bore of the sections by means of the flanged connection (d) and do not connect the annulus of the sections. Consequently, when the external layer of the section is broken, the connectors located at the tips of each section will detect the flooded annulus, and with the flooding each connector will indicate the hydrostatic pressure of <NUM> bar and <NUM> bar respectively in the pressure gauge. If the intermediate section (<NUM>) is watertight, the pressure in the annulus will be up to <NUM> bar.

Example <NUM>: The analysis is carried out on the bottom riser, which includes the connectors 17d and 17e located at each tip of this section. A pressure reading of less than <NUM> bar indicates that the section is watertight. Values between <NUM> bar and <NUM> bar indicate flooding.

Example <NUM>: The analysis is carried out on the flexible line, commonly referred to as the flowline, which includes the connectors 18e and 18f located at each tip of this section. A pressure reading of less than <NUM> bar indicates watertightness, and the pressure reading of <NUM> bar indicates the total flooding of this section.

Example <NUM>: When the annulus is watertight, there is a column of permeate gas (CO2, CH4, etc.) filling the annulus. The pressure of this gas in the region of the upper connector is at most equal to the hydrostatic pressure at that point as a result of the action of the safety valves and in the lower connector is equal to the pressure value in the region of the upper connector added to the gas column. The low density of the gas makes it possible to approximate the pressure of the lower connector to the pressure of the upper connector.

Example <NUM>: In the case of flowlines where there is little difference in depth (external pressure) between the connectors of the sections, the gas permeation model provided by the manufacturer of the flexible line should be consulted to determine the maximum pressure value to be reached exclusively as a result of the permeate gases. It should be born in mind that the permeation model of the largest manufacturer of flexible lines specifies that the maximum pressure reached in the annulus as a result of permeate gases is approximately <NUM> bar. Consequently, in flowlines installed at depths greater than <NUM> (<NUM> bar of external pressure), it can be inferred that if the pressure in the annulus is less than the external pressure, then the annulus is watertight.

In general, the inspection analysis methodology for checking whether the annulus is watertight is as follows:.

If watertightness is confirmed, the method for collecting samples is usually as follows:.

If it is beneficial for a safety valve (<NUM>) to be removed from the connector (<NUM>), the equipment according to the present invention can be adapted for this purpose. The method continues as follows:.

Some example problems that could come up when executing the inspection method: the safety valves could get jammed, but are normally forced open by a pressure difference of around <NUM> bar, some flowlines can require dredging, and finally execution of all of the activities (procedures) needs to be mapped by the ROV pilots.

Claim 1:
A system for detecting the water tightness of the annulus in a flexible line from a connector that contains a safety valve (<NUM>) with a recess wherein the system includes:
- a Remotely Operated Vehicle, ROV (<NUM>)
- a device containing an assembly in the form of a plunger (<NUM>) and a cylinder (<NUM>), the cylinder (<NUM>) having a sealing system (<NUM>) configured to provide a seal between the external environment and the front region of the plunger (<NUM>),, said device being controlled by the ROV,
- a pressure gauge (<NUM>) connected to a chamber created between the cylinder (<NUM>) and the plunger (<NUM>), the pressure gauge (<NUM>) configured to monitor the pressure in the front region of the cylinder (<NUM>) of the device, and
- a rod (<NUM>) connected to a chamber (<NUM>) for controlled piston-cylinder-type actuation, wherein the face of the cylinder (<NUM>) is open and is configured to be fitted into the safety valve (<NUM>) of the connector of the flexible line (<NUM>),
- the ROV (<NUM>) includes an arm (<NUM>) that moves a handle (<NUM>),
the system further comprising:
- a coupling and anchoring system (<NUM>) controlled by the ROV and configured to position the assembly of cylinder (<NUM>) and plunger (<NUM>), to grasp the connector of the flexible line (<NUM>), to install the device in the recess of the safety valve (<NUM>) of the connector of the flexible line (<NUM>) and to activate the sealing system (<NUM>) by sealing the cylinder (<NUM>) of the device against the wall of the recess of the valve (<NUM>).