BACKGROUND OF THE INVENTION

The present invention relates to the inspection of orifice meter in an oil and gas pipeline and to the assessment of the flow in an oil and gas pipeline. The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. Furthermore, all embodiments are not necessarily intended to solve all or even any of the problems brought forward in this section.

In oil and gas industry, the flow assessment in a pipeline may be very important to evaluate the daily production of a well and also process allocation.

For this flow assessment, "orifice meter" is widely used in the industry because of optimum price and good accuracy. An "orifice meter" is a dedicated plate installed in pipeline, perpendicular to the pipeline direction, with a calibrated orifice bore in its middle.

Knowing the radius / diameter of an orifice bore in the orifice plate, it is possible to determine flow rate based on differential pressure.

Nevertheless, this "orifice meter" may be subject to extreme working conditions, such as high pressure, sand, impacts, cavitation bubbles, etc. Therefore, "orifice meter" may experience deformations and wear (e.g.: change in orifice bore due to erosion by sand).

In order to be sure the orifice meter is still accurate, it is recommended to physically inspect the orifice. According to international standard for technical meters (more strict for fiscal meters), the orifice must physically be checked every 6 months (API MP MS Chapter 20 - Allocation Measurement, Section 1- Allocation Measurement, sub section 1. 11.4 Meter Calibration; Edition 1993).

It may be very difficult to comply with this regulation as there is a need to stop the production (if there is no bypass line). Majority of orifice meters are installed within non retractable orifice holders, and physical checks require production shutdown (if no other production routing).

Stopping the production is costly and should be avoided. As the result many orifice meters installation are not inspected for years (can be even tens of years), which result to lower accuracy and it may create wrong understanding on well/production site performance, wrong production forecast, etc.

There is thus a need for enabling the inspection of the orifice bore without stopping the production of the oil and gas well. SUMMARY OF THE INVENTION

The invention relates to a method to inspect an orifice bore of an orifice meter installed on an industrial pipeline, wherein the method comprises:

- installing a radiographic source and a radiographic receiver, the orifice bore being between the radiographic source and the radiographic receiver; - capturing a radiographic image of the orifice bore on the radiographic receiver using the radiographic source;

- determining a dimension or a shape of the orifice bore based on the captured radiographic image.

The radiographic source may be a gamma ray source (radioisotopes) or an X-ray source (electromagnetic radiation) for instance.

The radiographic source may be a set of any plurality of sources.

The radiographic receiver may be a radio film or any receiver sensitive to rays emitted by the radiographic source.

Based on that determined dimension or form, it is possible to raise an alert (e.g. if this determined dimension or form is not in a predetermined range). Determining a dimension or a shape of the orifice bore based on the captured radiographic image may comprise:

- determining if the captured radiographic image includes a symmetrical egg shape. If the radiographic image does not include a perfect symmetrical egg shape, the orifice bore may have an impact and may not be a circle: therefore, by checking if the captured radiographic image includes a symmetrical egg shape, the shape of the orifice bore is indirectly checked.

Determining a dimension or a shape of the orifice bore based on the captured radiographic image may also comprise:

- comparing an egg shape in the captured radiographic image with a reference shape.

The reference shape may be contained in database of reference shapes. Therefore the comparison may be performed with the database.

The reference shapes may be issued from previous measurements of the same orifice bore or a similar orifice bore in the same conditions (i.e. same relative positions of the source, the receiver and the bore, an identical dummy can be used for this purpose).

For example, using old data of same installations taken several years ago, current radius / diameter of the orifice bore may be evaluated: if the egg shape in the captured radiographic image is bigger than the reference shape, it may be derived that the edges of the orifice bore have been eroded.

In a possible embodiment, determining a dimension or a shape of the orifice bore based on the captured radiographic image may comprise:

- determining a minimum diameter of an egg shape in the captured radiographic image; - determining a real dimension of the orifice bore as a function of said minimum diameter.

Determining a dimension or a shape of the orifice bore based on the captured radiographic image may also use interpolation method(s), for instance, contained in a database.

The minimum diameter may be the maximum dimension in a direction perpendicular to the maximum dimension of the egg shape.

The real dimension may be the radius of the diameter of the orifice bore.

In addition, the method may further comprise:

- capturing a radiographic image of a portion of the pipeline on a second radiographic receiver using the radiographic source, a line orthogonal to said portion going through the radiographic source and the second radiographic receiver;

- determining a projection coefficient value as a function of a first dimension of the captured radiographic image of the portion of the pipeline and of a second dimension of the portion corresponding to the first dimension.

The determination of the real dimension of the orifice bore may then be function of the determined projection coefficient value.

In a possible embodiment, the second dimension may be a diameter of the portion of the pipeline.

Advantageously, the method may further comprise:

- computing D = D _proj _ _bore * K _proj * (1 - 5 _proj ) where D _proj _ _bore is the minimum diameter, K _proJ is the projection coefficient and 5 _proJ is an experimental projection offset.

The determination of the real dimension of the orifice bore may function of D or may be D depending of the definition of 5 _proj .

The experimental projection offset may be determined according a plurality of experiences with different sizes of pipelines and/or different size of orifice bores.

The experimental projection offset may be determined as a function of 0.0038 * Dpipe + 0.013 where D _pipe is the external diameter of the pipeline and is expressed in inch.

This relation has been determined with a set of different sizes of pipeline and with a linear regression. Similar functions may be simply derived if the pipeline diameter is expressed in meter or other metrics (conversion into a different system).

In addition, determining the real dimension of the orifice bore may further comprise: - determining an angle between two lines passing respectively by the radiographic source and the center of the orifice bore and by the radiographic source and one edge of the orifice bore.

The determination of the real dimension of the orifice bore may be function of the determined angle. The determination of this angle may be performed according to classical geometrical considerations based on the known dimensions of the installation. Examples of such determination are presented below.

A second aspect relates to a computer program product comprising a computer readable medium, having thereon a computer program comprising program instructions. The computer program is loadable into a data-processing unit and adapted to cause the data-processing unit to carry out the computation steps of the above described method when the computer program is run by the data-processing unit.

Other features and advantages of the method and apparatus disclosed herein will become apparent from the following description of non-limiting embodiments, with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements and in which: - Figure 1 a is a side view of a pipeline, an orifice plate and a radiographic device according one embodiment of the present invention;

- Figure 1 b is a 3D view of the capturing of the orifice bore according one embodiment of the present invention;

- Figure 2a and 2b are respectively captured image of the pipeline and of the orifice bore using a same radiographic source.

- Figure 3 is a possible embodiment for a device that enables the computation steps of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 a is a side view of a pipeline, an orifice plate and a radiographic device according one embodiments of the present invention.

In this embodiment, the orifice plate 103 is installed between two portions of the pipeline 101 and 102 (external diameter D) and it is maintained in place by screws 104: the two portions 101 and 102 maintain the orifice plate 103 in place.

A radiographic source 105 in installed close to one portion of the pipeline (elevation ho, distance from the orifice plate l ₀ ), for instance, with a physical connection to the portion 102.

The radiographic source is able to "illuminate" the orifice bore 106 (diameter: h ₂ ) of the orifice plate 103.

A radiographic receiver 107 (for instance, a radiographic paper or any electronic receiver which is sensitive to the rays of the radiographic source 105) is installed under the pipeline (i.e. the orifice bore being between the radiographic source and the radiographic receiver) (elevation h-i ) so that a radiographic image of the orifice bore 106 may be created on the radiographic receiver 107 using the radiographic source 105.

The image of the orifice bore 106 on the radiographic receiver 107 should be a perfect symmetrical egg shape image if the orifice bore is a perfect circle. Therefore, if the image of the orifice bore 106 is not a perfect symmetrical egg shape image, it is possible to determine that the orifice bore has a defect based on the captured radiographic image.

Nevertheless this is not the only defect it is possible to detect. For instance, if there is some sand in the extracted oil or gas, the orifice bore may slowly be eroded and the size of the orifice bore may slowly increase while the orifice bore remains a perfect circle.

Therefore, it may be useful to accurately determine the diameter of the orifice bore without removing the orifice plate.

A first method to determine the diameter of the orifice bore without removing the orifice plate may be the following.

It is assumed that the orifice bore may be determined as D _bore = D _proJ _ _bore * Kproj * (1 - Sproj) , D _bore being the calculated orifice bore diameter, D _proJ _ _bore being the minimum diameter of the egg shape image (see Figure 2b) on the radiographic image (i.e. if the "egg" have its greater dimension in a vertical direction, D _proJ _ _bore is the greater horizontal dimension of the shape), K _proJ being a projection coefficient and 5 _proJ being a projection offset. In figure 2b, the greater diameter is element 202 while the minimum diameter is element 203. To determine the projection coefficient K _proj , it is possible to compute the ratio

Kproj =— — where D _pipe is the external diameter of the pipe (D on Figure 1 a), and D _proJ _ _pipe being the diameter of the projected image (see Figure 2a) of the pipe 102 on a radiographic receiver 108 (said latter image being a projected image of the pipeline perpendicular to the main direction 109 of the pipeline, i.e. the line passing through the radiographic source and the radiographic receiver 108 and the line 109 in the middle of the pipe are perpendicular and have an intersection). In figure 2a, Dproj-pipe is element 201.

In addition, 5 _proJ has been experimentally determined and is 5 _proJ = 0.0038 * D _pipe + 0.013 (if D _pipe is expressed in inch).

This method is very simple to implement as only simple measurements are needed on two radiographic images. The relative positions of the radiographic source and of the radiographic receivers may be unknown.

A second method is described in relation of Figure 1 b (geometrical method).

Figure 1 b is a 3D view of the capturing of the orifice bore according one embodiment of the present invention.

In this Figure 1 b, element 106 is the orifice bore (circle) and element 106 _prOj is the egg shape image of said orifice bore. To determine the radius (similar method may be set for the diameter) of the orifice bore (i.e. the distance between E and H), it is possible to execute the following steps:

1 ) compute the angle CAB between AC and AB, with:

- AB is known by measuring vertical distance between radiographic source and the radiographic receiver (i.e. h ₀ +D+hi according to Figure 1 a);

- BC is known by measuring BF (l ₀ according to Figure 1 a) + FC ( according to Figure 1 a); the angle CAB is computed thanks to the following formula

compute AC thank to the following formula: AC

cos(CAB)' -2bis) alternatively to steps 1 ) and 2), AC may be computed as AC = -2ter) it is possible to compute AC as an average value of any combinations of the computed values of AC in steps 1 -2), and/or 1 -2bis); ) compute angle CAD of AC and AD, with:

- CD is known from measurement performed on the egg shape image (minimum diameter divided by 2);

- the angle CAD is determined thanks to the following formula : tan(CA~D) =—

J AC ) compute AE, with:

- AG is known (h ₀ +D/2 according to Figure 1 ) ;

- AE is computed thanks to the following formula: AE =

cos(CAB) ' bis) alternatively to step 4), AE may be computed thanks to the following

GE

formula: AE = _sin(e¾g) (GE is l ₀ according to Figure 1 a); ter) alternatively to step 4) or step 4bis), AE may be computed as AE = y/AG ² + GE ² (GE is l ₀ according to Figure 1 a); quater) it is possible to compute AE as an average value of any combinations of the computed values of AE in steps 4), 4bis) and/or 4ter); ) compute radius of the orifice bore (i.e. EH) thanks to the following formula:

AE

EH =

cos(CAD) ^' Figure 3 is a possible embodiment for a device that enables the present invention.

In this embodiment, the device 300 comprise a computer, this computer comprising a memory 305 to store program instructions loadable into a circuit and adapted to cause circuit 304 to carry out the steps of the present invention when the program instructions are run by the circuit 304.

The memory 305 may also store data and useful information for carrying the steps of the present invention as described above.

The circuit 304 may be for instance:

- a processor or a processing unit adapted to interpret instructions in a computer language, the processor or the processing unit may comprise, may be associated with or be attached to a memory comprising the instructions, or

- the association of a processor / processing unit and a memory, the processor or the processing unit adapted to interpret instructions in a computer language, the memory comprising said instructions, or

- an electronic card wherein the steps of the invention are described within silicon, or

- a programmable electronic chip such as a FPGA chip (for « Field- Programmable Gate Array »). This computer comprises an input interface 303 for the reception of the various measurements/measures used needed for the execution of at least one of above described steps and an output interface 306 for providing the radius or the diameter of the orifice bore.

To ease the interaction with the computer, a screen 301 and a keyboard 302 may be provided and connected to the computer circuit 304.

Expressions such as "comprise", "include", "incorporate", "contain", "is" and "have" are to be construed in a non-exclusive manner when interpreting the description and its associated claims, namely construed to allow for other items or components which are not explicitly defined also to be present. Reference to the singular is also to be construed in be a reference to the plural and vice versa.

A person skilled in the art will readily appreciate that various parameters disclosed in the description may be modified and that various embodiments disclosed may be combined without departing from the scope of the invention.