The present invention refers to a wellhead valve system for adjusting the flow, also called wellhead choke valve system, for example of hydrocarbons, having the integrated ability of measuring the multiphase flow rate, In the field of fluid extraction, particularly hydrocarbons such as petroleum or natural gas, the wellhead is the part of the well on the surface and comprises a set of control valves used for both directing and adjusting the flow of fluids, from or towards the well, as well as safety valves for preventing an uncontrolled release of petroleum or gas into the environment.

When the well is in a condition in which it can produce petroleum or gas, the valves of the wellhead are suitably opened and the fluids are released through a pipeline which conveys them to a gathering station, or otherwise to a platform or storage ship, in the case of a subsea well .

Currently on the market there are valves or valve systems which are used at the wellhead which allow the flow rate of the flow of hydrocarbons to be managed. The valve systems known to this day, however, do not foresee measuring the flow rate and, in order to carry out such measuring, it is necessary to use suitable flow rate measurement devices .

In plants already in existence, the flow rate measurement devices are generally shared amongst many wells due to problems of mechanical bulk or because they can only be installed by modifying the engineering of the pipelines downstream of the wellhead.

Alternatively, it is possible to install temporary flow rate measurement devices, externally and parallel to the existing plant, positioned downstream of the wellhead during specially organized measuring campaigns.

Such an operation, beyond generally requiring specific authorization, it is also time consuming and costly. With respect to the modality of modifying the degree of opening of the valve itself according to the adjustment of the flow, in on-shore applications, such valves or valve systems are mainly of the manual type. Valves or valve systems exist which are commanded remotely through suitable actuators actuated according to productive needs and flow rate data, generally used remotely only in inaccessible areas, like in the case of subsea wellheads, or unmanned sites.

Moreover, at a wellhead it is desirable to use valve systems which are able to carry out rapid transients of its degree of opening, so as to be able to carry out particular plant tests, for example, causing sudden flow rate variations. However, the most common valve systems used today do not allow for a fast enough manoeuvring speed to carry out such tests, for example, an opening or closing manoeuvre in less than a second.

On the other hand, the valve systems which are rapid enough for the manoeuvre have such mechanical clearances so as to not allow a sufficiently precise determination of the produced transition.

Therefore, an adjustment carried out through such valve systems, does not allow a high level of accuracy to be achieved for fine adjustments of the flow.

If it is desired to use the valve systems known today it is thus necessary to make the compromise between having high valve reaction speed and having a good level of accuracy. The purpose of the present invention is that of avoiding the aforementioned drawbacks and in particular that of conceiving a wellhead valve system for adjusting the flow which allows a rapid and accurate adjustment of the flow rate from or towards the well. A further purpose of the present invention is that of making a wellhead valve system which is able to measure the instantaneous multiphase flow rate.

Another purpose of the present invention is that of providing a wellhead valve system which allows rapid opening and/or closing transitions to be carried out whilst maintaining high accuracy with respect to its own instantaneous degree of opening. - A -

The last but not least purpose of the present invention is that of making a wellhead valve system which can be programmed, offering the possibility to operate fully automatically . These and other purposes according to the present invention are achieved by making a wellhead valve system as outlined in claim 1.

Further characteristics of the wellhead valve system are object of the dependent claims. The characteristics and the advantages of a wellhead valve system according to the present invention shall become clearer from the following description, given as an example and not for limiting purposes, referring to the attached schematic drawings in which: - figure 1 is a perspective view of an embodiment of a hydraulic valve used in the wellhead valve system according to the present invention; figure 2 is a section view of the wellhead valve system according to the embodiment of figure 1. With reference to the figures, a wellhead valve system is shown, wholly indicated with the numeral 100. The wellhead valve system 100 comprises a hydraulic control valve 10 adjusted to open and close by an actuator 24 in turn actuated through manual commands, or preferably, automatically through a control logic 25 which processes a suitable command signal based, amongst other things, upon values detected by a position gauge 17 indicative of the degree of opening of the valve 10. The hydraulic control valve 10, comprises a valve body 11 provided with an inlet opening 12 and an outlet opening 13 through which, if the valve 10 is in an at least partially open configuration, the fluids, for example, hydrocarbons, transit according to the flow direction indicated with the arrow F in figure 2. At the inlet opening 12 and the outlet opening 13, the valve body 11 comprises a first and a second flange 11a and lib.

Interposed between the inlet opening 12 and the outlet opening 13 an adjustable orifice 16 is foreseen. In the preferred embodiment illustrated, the inlet opening 12 and the outlet opening 13 are on planes perpendicular to one another, corresponding to the ends of an "L"-shaped pipe, i.e., made up of two pipe portions 14, 15 which are perpendicular to one another. The adjustable orifice 16 is arranged at the elbow of the "L" -shaped pipe. In order to adjust the degree of opening of the valve 10, the actuator 24 commands the adjustable orifice 16 in particular by operating on the opening and closing means 20 of such an adjustable orifice 16. In a preferable manner, the adjustable orifice 16 is an element with disks comprising a first fixed disk 18 provided with a hole (not illustrated) and a second moveable disk 19 also provided with a further hole (not illustrated) .

The moveable disk 19 is integral with a stem 20 which is commanded to rotate by the actuator 24.

In such a way also the moveable disk 19 is commanded to rotate so as to modify the overlapping surface portion of the openings of the two disks 18, 19.

In this way, a variation of the degree of opening of the valve 10, is obtained.

According to the present invention, the position gauge 17, like for example an encoder, is integral with the opening and closing means 20 of the adjustable orifice

16 so as to detect the exact degree of opening of said adjustable orifice 16 and therefore of the valve 10.

In the embodiment illustrated, the position gauge 17 is integral with the stem 20 of the moveable disk 19 thus detecting the exact position of the set made up of the moveable disk 19 and the stem 20, and therefore the exact relative position between the openings of the two disks 18, 19 fixed and moveable. From the relative position between the openings of the two disks 18, 19 it is possible to calculate the overlapping portion of the respective openings exactly.

In such a way, the adjustment of the position of the set

19, 20 is completely free from possible mechanical clearances that may affect the actuator 24 since the adjustment of the actuator 24 itself is free from such mechanical clearances. The wellhead valve system 100 according to the present invention can thus carry out rapid transitions without affecting the accuracy of the degree of opening of the valve 10 itself. Moreover, thanks to the accurate measurements carried out by the position gauge 17, the control logic 26 is able to accurately and instantaneously determine the gas/liquid single-phase and/or two-phase flow rate value, starting from the data measured by a plurality of fluid and/or flow parameters sensors 22, 23, comprising at least pressure sensors 22 and temperature sensors 23. In such a way, as well as based upon production needs, the opening and the closing of the hydraulic valve 10 can be adjusted in a fine manner based upon the calculated flow rate values.

Preferably, pressure sensors 22 are used which operate at a sampling frequency greater than or equal to 100 samples per second, and temperature sensors 23 which operate at a sampling frequency which is greater than or equal to one sample per second. This makes it possible to faithfully detect and record the effect of rapid transients of the degree of opening of the adjustable orifice 16. In a preferred manner, the fluid and/or flow parameters sensors 22, 23 are integral with the valve body 11 of the hydraulic control valve 10 and positioned both upstream, and downstream of the adjustable orifice 16 with respect to the direction of the flow F. In particular, such fluid and/or flow parameters sensors 22, 23 are constrained to the first and second flange 11a, lib of the valve body 11. In such a way, the measurements of the pressure, of the temperature and of the degree of opening of the valve as well as the consequent calculated gas/liquid monophase and/or biphase flow rate value, are known with absolute simultaneity thus eliminating time differences existing amongst these data in conventional well measuring and control systems.

Moreover, the ability of the wellhead valve system to obtain the gas/liquid single-phase and/or two-phase flow rate allows each well to have a complete set of measurements thus avoiding the need to install further apparatuses in suitable positions of the pipeline. Again, since the wellhead valve is a replaceable component without needing to actuate permanent modifications to the plants on the surface, the valve system of the present invention also allows even preexisting plants to be equipped with permanent measuring capability, of the fluid and/or flow parameters, where none was originally foreseen. Preferably, the wellhead valve system 100 additionally comprises gauges 21 for measuring the concentration of water in the liquid state, also called water-cut meters, integral with the valve body 11 positioned upstream and/or downstream of the adjustable orifice 16 with respect to the direction of the flow F.

In such a way, the wellhead valve system 100 is also able to determine the quantity of water in the hydrocarbon fluid which flows through the valve 10, therefore it can also detect the three-way flow rate, i.e., the flow rates of the single distinct fluid phases

(for example, vapour/hydrocarbon/water) .

Again, the use of a control logic 25 in the valve system 100 according to the present invention allows operations of the valve system 100 to be programmed, like for example, programming the automatic cleaning operation of the adjustable orifice.

Such an operation can be repeated at predetermined intervals or when there are anomalous variations in flow rate which the wellhead valve system 100 according to the present invention is able to detect, like for example, a sudden increase of the flow rate upstream of the adjustable orifice 16. From the description made the characteristics of the valve system object of the present invention as well as the relative advantages should thus be clear.

It is finally clear that the valve system 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 sizes, can be any according to the technical requirements .