APPARATUS AND PROCESS FOR CONVEYING AND RECOVERING HYDROCARBONS FROM AN UNDERWATER WELL OR FROM AN UNDERWATER PIPELINE IN UNCONTROLLED RELEASE (BLOWOUT) CONDITIONS

Apparatus and process for recovering hydrocarbons from an underwater well or pipeline in uncontrolled release conditions, wherein the apparatus comprises a separation chamber (11) having an inlet (11a) for a multi-phase stream comprising the flow of hydrocarbons (23) in outlet from the underwater well or from the underwater pipeline, and a plurality of outlets (13, 14, 18) for respectively conveying a mainly gas phase (21), a mainly light liquid phase (22b) and a mainly heavy liquid phase (22a) coming from the separation of the multi-phase stream in inlet, the inlet (11a) consisting of a directioning body (31) of the multi-phase stream towards the inside with respect to the separation chamber (11), the directioning body (31) comprising a first inlet end (31c) of the multi-phase stream and a second end (31b), opposite to the first end (31c), the second end (31b) being in fluid communication with the separation chamber (11) and it is characterised in that an outlet (18) for the mainly heavy liquid phase (22a) of the plurality of outlets (13,14,18) is in fluid connection with the inlet (11a) of the separation chamber (11).

The present invention refers to an apparatus and to a process for conveying and recovering hydrocarbons from an underwater well or from an underwater pipeline for extracting hydrocarbons in uncontrolled release conditions.

The constant increase in the global demand for hydrocarbon fluids has led to a growing activity in offshore exploration and production.

The submarine environment, in addition to making the production more difficult, leads to a greater risk of environment damage in the case in which there are blowouts i.e. an uncontrolled release of hydrocarbons from the extraction wells, and/or other uncontrolled leaking of hydrocarbons into the sea, for example, as a consequence of broken underwater pipelines.

Such events, although rare, are not only a loss in terms of energy, but can have very serious consequences in terms of safety of the workers, of pollution of the environment and of well recovering costs.

There have been many attempts in the past to try to ensure an effective recovery of the uncontrolled outflow of hydrocarbons in deep seas.

Blowout prevention systems known today have application limitations due to the formation of hydrates, especially at great sea depths and/or at high pressure conditions and low temperatures.

Indeed, at such depths, cold water, mixing with methane, leads to the formation of hydrates that tend to cause the separation system and/or hydrocarbon conveying lines to become blocked.

One solution for controlling underwater blowout is described in patent application n. WO2011/158093 the object of which is a conveying apparatus essentially consisting of a hollow cylindrical body provided with an inner quasi-cylindrical body, such as to identify inside it a separation chamber with an annular section in which the separation and stratification of the multiphase fluid in inlet occurs, in a light phase mainly made up of a gas and a heavy mainly liquid phase.

Such an apparatus is positioned above the exit of the well in blowout in a way such as to capture the flow of hydrocarbons in outlet, also called plume, so as to separate the gas part from the liquid part and subsequently convey them to the surface.

The apparatus object of patent application n. WO2011/158093 however, has the limitation of bringing, together with the jet, of hydrocarbons, significant amounts of sea water with flow rates also equal to many times that of liquid and gas hydrocarbons.

This phenomenon in addition to requiring pumping means that are over-sized with respect to those actually necessary for conveying only jets of liquid hydrocarbons, also leads to a considerable volume of fluids to be separated at the surface.

Moreover, in order to prevent hydrates from forming, methanol is required to be continuously introduced inside the apparatus from the surface, wherein the flow rate of methanol to be introduced is proportional to the flow rate of water to be treated.

The problems found above relating to the apparatus object of patent application n. WO2011/158093 can be partially solved by separating the water before the hydrocarbons are conveyed to the surface. However, the separation of two liquid phases at the bottom of the sea requires there to be very high separation volumes, making it difficult to manage the apparatus.

The purpose of the present invention is that of avoiding the drawbacks mentioned above and in particular that of making an apparatus and a process for conveying and recovering hydrocarbons from an underwater well or from an underwater pipeline in uncontrolled release conditions that are indeed capable of preventing the separation system and/or the hydrocarbon conveying lines from becoming blocked.

Another purpose of the present invention is that of providing an apparatus and a process for conveying and recovering hydrocarbons from an underwater well or from an underwater pipeline in uncontrolled release conditions that are capable of minimising the amount of sea water brought along with the jet of hydrocarbons.

A further purpose of the present invention is that of making an apparatus and a process for conveying and recovering hydrocarbons from an underwater well or from an underwater pipeline in uncontrolled release conditions that are capable of keeping the volumes of fluids to be separated low.

These and other purposes according to the present invention are achieved by making an apparatus for conveying and recovering hydrocarbons from an underwater well or from an underwater pipeline in uncontrolled release conditions as outlined in claim1.

Such purposes are moreover achieved with a process for conveying and recovering hydrocarbons from an underwater well or from an underwater pipeline in uncontrolled release conditions according to claim16.

Further characteristics of the apparatus and of the process for conveying and recovering hydrocarbons from an underwater well or from an underwater pipeline in uncontrolled release conditions are object of the dependent claims.

With reference to the figures, an apparatus for conveying and recovering hydrocarbons from an underwater well in uncontrolled release conditions is shown, wholly indicated with reference numeral10.

The apparatus for conveying and recovering hydrocarbons comprises a chamber11for the separation of a multi-phase stream consisting of the plume23coming from the well20and from sea water, into a mainly gas phase21and a mainly liquid phase22, in which the mainly liquid phase22comprises at least one heavy phase22aand a light phase22b.

The separation chamber11comprises an inlet11aof the multi-phase stream and a plurality of outlets13,14, one for conveying each of the separate phases21,22a,22b,respectively.

The inlet11aof the separation chamber11is advantageously made up of a directioning body31comprising a first end31cfor introducing the multi-phase stream and a second end that is opposite the first end, in fluid connection with the separation chamber11.

Preferably, the second end of the directioning body ends with a perforated cap31b.

The geometry of the perforated cap31bis such as to dampen the amount of motion of the multi-phase stream in inlet and to help separating the gas phase21from the liquid phase22.

Specifically, the directioning body31comprises a lower tapered portion, the wider lower end of which makes up the first inlet end31c.

The upper narrower end of the lower portion opens out, at the top, into an upper cylindrical portion31aof the directioning body31, in which such an upper cylindrical portion31aends at the top with the perforated cap31b.

The separation chamber11is placed in fluid connection with at least one collector means12through the outlet for conveying the light liquid phase22b,coinciding with the inlet of at least one connection tube14between the separation chamber11and the collector means12having a substantially vertical arrangement.

The collector means12is preferably arranged at the tapered portion31cof the directioning body31of the flow of hydrocarbons.

The collector means12has the advantageous shape such as to convey the multi-phase stream and the mainly heavy liquid phase22aout from the separation chamber11towards the inlet11a.

A preferred shape, given as a non-limiting example of the collector means12, is the toroidal shape, which is characterised by a circular annular plan and a section that is also circular.

According to the present invention, the outlet18for conveying the heavy liquid phase22ais in fluid connection with the inlet11aof the multi-phase stream.

The outlet18for conveying the heavy liquid phase22ais placed near to the first inlet end31cof the directioning body31.

Such an advantageous shape and arrangement of the outlet18for conveying the heavy liquid phase22apromotes the recirculation of part of the plume23entering the separation chamber11and of part of the heavy liquid phase22aseparated inside such a chamber11and subsequently conveyed towards the inlet11a, in such a way reducing the intake of sea water from outside.

Indeed, the difference in pressure that is generated inside the separation chamber and the inlet11athereof, causes the heavy liquid phase22ato come out from the openings18and to re-circulate towards the jet of hydrocarbons23, thus reducing the flow rate of water brought along with the jet towards the directioning body31.

The outlet for conveying the gas phase is made up from a first pipeline13for conveying the gas phase towards the surface.

In the preferred embodiment illustrated, the separation chamber11is defined inside a hollow outer body30having a frustoconical or frusto-pyramidal shape, which is open at the bottom and connected at the top to the first pipeline13for conveying the gas phase towards the surface.

Preferably, the hollow outer body30is suitably insulated so as to keep the temperature of the single phases21,22a,22babove the temperature in which hydrates are formed.

The directioning body31, located inside the hollow outer body30, acts as a separation element between a lower area30aof the outer body, through which there is the introduction11aof the multi-phase stream, and an upper area30bof the outer body for separating the multi-phase stream, which are placed in fluid communication with one another.

In the illustrated embodiment, the cylindrical upper portion31aof the directioning body31has a shorter diameter with respect to the inner diameters of the outer hollow body30and the lower tapered portion31cof the directioning body31acts as a connection element between the lower base of the cylindrical upper portion31aand the inner wall of the body30.

Preferably, the directioning body31is arranged coaxially with respect to the hollow outer body30, at a height that is substantially intermediate with respect to the axial extension of such a body30.

Preferably, the tapered portion31chas a frustoconical shape with its shorter diameter coinciding with the diameter of the cylindrical upper portion31aand its longer diameter coinciding with a diameter of the inner wall of the outer body30.

Inside the hollow outer body30, it is moreover provided a hollow tubular body32, having a circular or square-shaped section according to whether the outer body30has a frustoconical geometry or has the shape of a truncated pyramid, open both at the top, and at the bottom, placed at the upper area30aof the outer body30, therefore at the top with respect to the directioning body31, substantially at the cylindrical upper portion31a.

The hollow tubular body32is connected at the perimeter of the upper end of its side wall to the inner wall of the outer body30.

In its side wall32a,substantially at the upper end facing the first conveying pipeline13, the hollow tubular body32is provided with at least one hole33that is suitable for keeping a pressure balance between the liquid arranged inside and outside the hollow tubular body32itself.

In the illustrated embodiment, the separation chamber11is delimited peripherally and externally by the inner wall of the outer body30and internally and below by the group made up of the directioning body31and the hollow tubular body32.

In such an embodiment, the inlet11aof the multi-phase stream is located at the lower area30aof the hollow outer body30and the fluid connection with the outlet for conveying the heavy liquid phase22ais obtained by means of a plurality of holes18present in the tapered portion31cof the directioning body31.

The collector means12is arranged below the tapered portion31cof the directioning body31and the at least one connection tube14passes through such a tapered portion31cso as to obtain the fluid connection between the collector means12and the separation chamber11.

In alternative embodiments that are not illustrated, the collector means12is arranged at the top of the tapered portion31cof the directioning body31. In the case in which there are many connection tubes14, these are preferably arranged spaced equally angularly apart along the circular development of the toroidal collector means12.

The collector means12is in fluid connection with the surface by means of the interposition of pumping means15, preferably of the type with variable revs, to which the collector means12is connected through a pipe16for conveying the light liquid phase22b.The pumping means15are in turn connected to the surface through a second pipeline17for conveying the light liquid phase22b.

Downstream of the pumping means15it is preferably provided a known type of ejection system (not illustrated), as described in WO2011/158093.

The at least one connection tube14has an extension inside the separation chamber11so that an upper end thereof14ais positioned at a height that is greater with respect to the lower base of the cylindrical upper portion31aof the directioning body31and at a height that is lower with respect to the perforated cap31b.

In particular, the height at which the upper end14aof the connection tube14is positioned, is spaced away from the height of the perforated cap31bin a way that is sufficient so as to allow keeping the gas-liquid interface34at an intermediate height with respect to the height of the perforated cap31band to that of the upper end14aof the connection tube14.

The height of the gas-liquid interface34is, for example, adjusted by means of suitable control means (not illustrated) acting on the pressure of the system or on the number of revs of the pumping means15for evacuating the light liquid phase22b.

The operation of the apparatus10for conveying and recovering hydrocarbons from an underwater well for extracting hydrocarbons in uncontrolled release conditions is as follows.

In the operative condition the plume23, consisting of a mixture of gas and oil, comes out at high pressure from the well20, in such a way incorporating inside it sea water, and is intercepted, at a certain height, by the apparatus10for conveying and recovering hydrocarbons according to the invention, wherein the height is determined by the operative conditions of the apparatus10.

The sea water entering inside the apparatus for conveying and recovering hydrocarbons10forms the heavy liquid phase22a.

The multi-phase stream in inlet, thus consisting of at least oil, gas and sea water, enters inside the separation chamber11of the apparatus for conveying and recovering hydrocarbons10through the directioning body31.

The geometry of the directioning body31, together with that of the perforated cap31bis such as to dampen the amount of motion of the stream in inlet.

The amount of the damping carried out by the perforated cap31bdepends upon the height at which the flow of the multi-phase stream in outlet from the well is intercepted.

Passing through the holes of the perforated cap31bthe multi-phase stream enters inside the separation chamber11where the oil-gas-water mixture tends to separate and to be stratified in three phases.

By gravity, there is a first separation into a mainly gas phase21consisting of a mixture of gas and liquid hydrocarbons, and a mainly liquid phase22, consisting of a mixture of water and liquid hydrocarbons containing small amounts of dispersed gas.

Moreover, the mainly liquid phase22stratifies at the top into a light hydrocarbon phase22band at the bottom into a heavy liquid phase22amainly consisting of water.

The gas phase21flows towards the first pipeline13for conveying the gas phase towards the surface.

The light hydrocarbon phase22bflows, through the at least one connection tube14, into the collector means12from which it is subsequently sucked by the pumping means15and conveyed to the surface inside the corresponding second pipeline17for conveying the light liquid phase22btowards the surface.

In the case in which there is an ejection system, the pumping means15convey the light liquid phase22bthrough it.

The heavy aqueous phase22astratified in the lower part of the separation chamber11, is roughly separated and flows through the holes18present in the tapered portion31cof the directioning body31towards the inlet11aof the separation chamber.

At the inlet11aof the separation chamber, by exploiting the pressure gradients present inside the separation chamber11, the stream of roughly separated aqueous phase22arotates around the collector means12and is recirculated with the plume23.

The characteristics of the device object of the present invention are clear from the description made, just as the relative advantages are also clear.

The incorporation of the stream of roughly separated aqueous phase with the plume coming out from the well minimises the dilution of the multi-phase stream entering the separation chamber.

Analogously, also the part of plume which does not enter inside the separation chamber is recirculated with the plume in outlet from the well, possibly rotating around the collector means, avoiding also in this case the incorporation of sea water from outside and consequently a dilution of the multi-phase stream entering the separation chamber.

This leads to a considerable reduction of the requirement of surface separation treatments.

Moreover, the recirculation of part of the plume and of the roughly separated aqueous phase, considerably reducing the incorporation of sea water from outside, having temperatures that are substantially lower, leads to an overall increase in the temperature of the multi-phase stream entering the apparatus.

By maintaining the temperature of the plume, also promoted by the insulation of the outer wall of the separation chamber, the risk of hydrates forming is considerably reduced.

It is finally clear that the device thus conceived can undergo numerous modifications and variants, all covered by the invention; moreover, all the details can be replaced by technically equivalent elements. In practice the materials used, as well as the dimensions, can be any according to the technical requirements.