WO2007148979A1

WO2007148979A1 - Sampling tool for hydrocarbon-producing wells

Info

Publication number: WO2007148979A1
Application number: PCT/NO2007/000213
Authority: WO
Inventors: Helge LØKEN
Original assignee: Inwell Technology As
Priority date: 2006-06-19
Filing date: 2007-06-18
Publication date: 2007-12-27
Also published as: DK2038514T3; NO328442B1; ATE461355T1; NO20062844L; EP2038514A1; EP2038514B1; DE602007005375D1

Abstract

The present invention relates to a sampling tool for extraction of production samples in a well. The tool comprises at least one set of a collecting cylinder (1), a collecting chamber (6) formed during use, with at least one inlet (11) and one outlet (12), and at least two pistons (4), arranged to be moved from the collecting chamber (6) into the collecting cylinder (1) at a given distance apart, and a flow channel (10) through the tool. The invention also comprises a method for extraction of samples in a flowing well.

Description

Sampling tool for hydrocarbon-producing wells

The present invention relates to a method and device for sampling the production in a well.

One of the most important areas of focus for the oil companies at the present time is the acquisition of as much information as possible on the conditions down in the oil reservoir and how they alter over time. In order to obtain more knowledge of the conditions in the production zone in the well, the oil companies hire well service operators who conduct a logging operation on the way down into the well and on throughout the whole production zone. The measurements carried out include measurements of temperature and pressure in the formation fluid. In addition, measurements are also carried out which indicate the existing quantitative proportions of the oil, gas and water phases.

Fig. 1 illustrates a simplified example of a production zone in a typical horizontal well. A well may be, for example, 3000-5000 metres long, with several zones, where pure oil, gas or water phases may flow out in some of the zones. It is also normal for mixed phases to flow out in some of the producing zones, where two or all three phases are present in the mixture.

In a hydrocarbon-producing well which produces by means of water injection, or where there is a combination of an injection consisting of water/gas, the result will be that all three phases will be a part of the total flow pattern over time. After a long production time, the water will become an essential part of the total flow pattern when the well has obtained what we define as a water break-through in the well's formation.

Due to the fact that the three phases have different specific gravity and the well is extensive in length, a flow pattern will form in the production tubing as illustrated in fig. 2 with gas (g), oil (o) and water (w) flowing through the tubing.

In a producing well it is normal for the flow rate to reach 20-30 meters per second. With the total flow pattern as illustrated above in fig. 2 in combination with the flow rate in the tubing, this makes it difficult to undertake local physical sampling down in the actual production zone.

The object of the present invention is to provide a device and method which in a satisfactory manner reduce or solve the problems encountered by previously known devices and methods in obtaining information on the production in a well. It is also an object to provide a device which can take samples in the flowing well with little influence on the production in the well. It is also an object to provide a reliable method of performing purely physical sampling of the production in a given portion of the reservoir. These objects are achieved with a tool and a method as indicated in the following independent claims, where further details will be apparent in the dependent claims and following description.

The present invention relates to a sampling tool for extraction of production samples in a well. According to the invention the tool comprises at least one set of: a collecting cylinder, a collecting chamber formed during use, with at least one inlet and at least one outlet and at least two pistons spaced at a given minimum distance apart, arranged to be moved from the collecting chamber into the collecting cylinder. The inlet to the collecting chamber is arranged so that the production flow from a chosen portion of the well flows into the collecting chamber. Thus it is only the production from this chosen portion of the well that flows into the collecting chamber, and other production in the well is not mixed into this collecting chamber, thereby exerting no influence on the fluid in the collecting chamber. Furthermore, the collecting chamber is so designed that the production flow coming in through the at least one inlet from this portion of the well is permitted to leave the collecting chamber through the at least one outlet, with the result that where no samples are taken, the production flow at the chosen portion flows out into the common production flow in the well. The collecting chamber may have a number of different configurations, but it is formed by the space which is located between the inlet to the tool and thereby the collecting chamber and the outlet of the chamber which also forms the outlet of the tool.

According to an embodiment of the invention, the sampling tool comprises a main body with a longitudinal axis. The longitudinal axis of the main body will be substantially parallel to a longitudinal axis of a pipe when the tool is arranged for use in the pipe.

According to an embodiment, surfaces of the main body together with an inner wall of a pipe and sealing devices, mounted at outer points of the surfaces for sealing against an inner wall of a pipe during use, form a collecting chamber. In such an embodiment the interface with the inner wall of the pipe will form an inlet to the collecting chamber, whereby it will be able to form a relatively large inlet. In another embodiment the collecting chamber is formed by a first partial chamber formed by an inner wall of a pipe wherein the device is located, and surfaces of the main body, where such a first partial chamber is connected to a transfer chamber leading to a second partial chamber comprising the pistons which are moved from this second partial chamber into the collecting cylinders, where this second partial chamber comprises an outlet to the rest of the production flow. The transfer chamber may be a radial, axial, a combination thereof or another chamber connecting the first and second partial chambers of the collecting chamber. A possible variant is an outer peripheral first partial chamber, a plurality of radially oriented transfer chambers leading a flow which is to be sampled radially inwards to a centrally located second partial chamber comprising the pistons. In this case upstream production will pass the sampling tool through passages provided in an annulus between the first and second partial chambers, which annulus is divided by the transfer chambers extending between the first and second partial chambers through this annulus. In another variant there is an outer peripheral first partial chamber, from which the transfer chamber leads in an axial direction to a position downstream of the first partial chamber, where the second partial chamber is located. In this embodiment this transfer chamber may be composed of a plurality of substantially axially extending pipes between the first and second partial chambers. In such a configuration upstream production fluid can be passed on the inside of the outer first partial chamber, and between and round the transfer chambers, and centrally through or on the outside of the second partial chamber. According to an aspect, the collecting chamber is formed by or in other words separated from the rest of the production flow by at least a portion of two at least partly annular seals between the main body and an inner wall of a pipe, where these annular seals are mounted at a distance apart. In such a case a whole chamber can be formed round the circumference of the main body. In this case the inlet to the chamber will be the interface with the inner pipe wall. Furthermore, according to an aspect sealing elements may be provided extending from one annular seal to the other annular seal in a direction substantially parallel with the longitudinal axis of the main body, thereby forming two or more collecting chambers round the circumference of the main body. This means that the circumference of the main body is divided into several sectors. The variant may also be envisaged where the seal is composed of two circle-sector seals and two longitudinal seals, without circle-sector seals extending round the whole circumference of the main body. Alternatively, seals of other shapes may be provided between the main body and the inner wall of the pipe during use, forming a collecting chamber or the inlet to the collecting chamber. The essential thing is to separate the inlet to the collecting chamber from the rest of the production in the well.

According to an embodiment the pistons are mounted on a connecting element, for example in the form of a piston rod mounted substantially centrally in the pistons. This piston rod may extend between two pistons or where there are several pistons, it may be arranged to pass through the middle pistons and possibly also the end pistons. A variant may also be envisaged, however, where the pistons are connected to several rods passing through the pistons. A variant may also be envisaged where the pistons are mounted on a rod in such a manner that they have a given spacing when moved into the collecting cylinder, but otherwise may be spaced at a fixed or varying distance apart. For example, they may be located closer together before being inserted into the collecting cylinder with a given spacing.

According to an aspect the collecting cylinder is composed of a pipe, which is open at both ends, with the result that it is pressure balanced for pressure in the well at the sampling location.

In an embodiment the pipe may also include a funnel-shaped inlet at the end of the pipe facing the collecting chamber and the pistons, in order to facilitate the insertion of the pistons into the pipe. The pipe may have a cylindrical cross sectional shape, but other cross sectional shapes, such as oval, square, triangular, etc. are also conceivable.

According to another aspect the collecting cylinder comprises at least one drain screw mounted in an area between two pistons when the pistons are completely inserted into the collecting cylinder. In this state the pistons have a given spacing in order to gain access to the samples when the collecting cylinder is taken up to the surface to the location for analysis of the samples. Mixing devices and displacement devices may be provided between the pistons in order to expel the fluid between the pistons through the drain screw. The collecting cylinder may also include a safety valve mounted in an area between two pistons when the pistons are completely inserted into the collecting cylinder. This safety valve and the drain screw may be provided as one unit mounted in the wall of the collecting cylinder.

According to another aspect the tool also comprises a pipe, in one variant a cylindrical pipe provided in connection with or in the collecting chamber for storing the pistons before they are moved towards and into the collecting cylinder. This is in order to ensure that an outer abutment surface of the pistons that provides the seal between the chambers formed between the pistons in the collecting cylinder is kept substantially isolated from the production flow until a sample is taken between two pistons. When the piston is moved from the cylindrical pipe to the collecting cylinder, at least a portion of the outer abutment surface will be exposed for a period to the production fluid in the well in the isolated area. In a variant the whole of the outer abutment surface of the piston is exposed to the production fluid in the isolated area in the well.

According to another aspect the tool is advantageously designed so that during use at least four collecting chambers are formed round the circumference of the tool, where the tool further comprises at least one flow channel. In this case the flow channel may preferably be arranged centrally in the main body. In an alternative embodiment the main body may be designed so that the collecting chamber is provided with one or more partial chambers and transfer chambers as described above, thus enabling upstream production to flow past the tool in several ways. An embodiment may also be envisaged with a collecting chamber which is U-shaped in cross section with the bottom of the U substantially in the centre of the tool and the flow channel for upstream production formed by the cross sectional area outside the U. The top of the U-shape then forms an inlet of the collecting chamber. The outlet from the collecting chamber is normally provided at a point downstream of the collecting chamber thereby obtaining a good flow through the chamber.

In an embodiment, the seal which is mounted on portions of the main body may be fluid-activated seals, or alternatively or as a combination at least partly mechanically activated seals and/or mechanical seals may also be envisaged.

According to the invention a method is also provided for extraction of samples in a well by means of a tool according to claim 1, where the tool is lowered into the well and moved to the sampling location which is of interest. At this position, the production flow is permitted to flow through the collecting chamber, whereupon the pistons are moved from a position in the collecting chamber to a position in the collecting cylinder, thereby causing a sample at the location of interest to be enclosed inside the collecting cylinder between two pistons, whereupon the tool is removed from the well and the collecting cylinders can be transported to the desired location for analysis of the samples.

In a variant of the method the tool comprises three or more pistons in a row, with the result that when the two first pistons are located in the collecting cylinder, the tool is moved to a new position, whereupon the pistons are moved further into the collecting cylinder until another piston is located in the collecting cylinder, and this process is repeated until all the pistons have been moved into the collecting cylinder.

Production in the well upstream of the tool is permitted to flow through the tool and will thereby not influence the samples taken in the collecting chamber.

The invention will now be explained in greater detail with reference to the attached figures, in which;

Fig. 1 is a schematic view of a well with several producing zones, Fig. 2 is a schematic cross sectional view of a gas, oil and water production, Fig. 3 illustrates a first embodiment of a sampling tool according to the invention, Fig. 4 illustrates a second alternative embodiment of the tool, Fig. 5 illustrates a cross section of a portion of the tool in fig. 4,

Fig. 6 illustrates an internal detail of the sampling tool in a first and a last position during sampling, Fig. 7 is a perspective view of parts of a third embodiment of the sampling tool,

Fig. 8 is a partial perspective view of parts of a fourth embodiment of the sampling tool,

Fig. 9 illustrates the cross section of a part of a fifth embodiment of the sampling tool,

Fig. 10 is a perspective view of a portion of a sampling tool in a sixth embodiment, and

Fig. 11 is a cross sectional view of the principles employed in the sampling tool in fig. 10. The invention comprises an assembled tool with characteristics which in an embodiment can perform a plurality of simultaneous samplings down in the production zone for the production tubing. This can be carried out while the well is producing hydrocarbons. By means of a swivel and an eccentric weight between the sampling tool and the tool that advances the tool in the well, for example by means of a wireline tractor, the sampling chambers will be located through the influence of gravity in a manner corresponding to, for example, the four positions: up or down and east or west, thereby providing information on the relative orientation of the samples. Corresponding elements in the different embodiments are given the same reference numeral. Fig. 3 illustrates a sampling tool according to the invention, comprising four sets of: a collecting cylinder 1, a collecting chamber 6 and pistons 4 at a given distance apart. The tool has a longitudinal axis 13, which during use will substantially coincide with the longitudinal axis of the pipe wherein the tool is employed. The collecting chamber 6 which is formed during use is composed of surfaces of the main body 20 and an internal surface of a pipe (not shown) wherein the tool is employed with two circumferential seals 2 and longitudinal seals 3, thereby forming four chambers round the circumference of the tool. The collecting chamber 6 has an inlet 11 formed by the interface with the internal wall of the pipe wherein the tool is employed and several outlets 12 provided in a downstream end of the collecting chamber 6. In the collecting chamber 6 a plurality of pistons 4 are provided, arranged at a given distance apart on a connecting element 14. Before being used for sampling, the pistons 4 are mounted internally in guide pipe 7 which both guides and protects the pistons 4. The seals 2, 3 may be activated hydraulically by the supply of hydraulic fluid via a hydraulic line 19. The tool is also designed in such a manner that collecting chamber 6 is formed round the circumference of the tool with a central flow channel 10 for through-flow of upstream production fluid in the well. Since the sampling tool allows flows from forwardly located zones in the front end of the tool to pass through the flow channel 10 in the tool, the local sampling will not be influenced by other production zones.

As we can see from the invention in fig. 3, the tool has four collecting cylinders 1 for sampling. For sampling, these four collecting cylinders, which are substantially in the form of pipes, are open to the well's pressure at the inlet 15 of the collecting cylinder, where the actual samples are drawn in, and in the outlet 16 at the rear. Based on this, the seals 24 on pistons 4 for sealing between the pistons 4 and an internal wall of the collecting cylinder 1 will not be subjected to the substantial differential pressures in the well. The tool has hydraulic packers 2 in the front and rear of the tool, which packers are activated when the tool has to undertake the actual sampling. Packers are contracted and expanded by a hydraulic fluid which enters internal cavities in packers through the pipe 19. Alternative methods may also be used for providing a seal between the tool chambers and the production tubing, such as a mechanical expansion. When the tool has to take the four samples simultaneously, since they are divided into four segments round the tool, packers 2 in the front and rear and packers 3 along the tool are activated.

The tool will then stay in this position for some time to enable the local sampling chambers to receive a through-flow of oil, water, gas or a mixture of these three phases from the zone. The through-flow will pass through two outlets 12 for each of the collecting chambers 6 beside the inlet 15 to the collecting cylinder for the samples. In order for the piston seals 24 to stay as clean as possible, and avoid being influenced by misalignment and vibrations, the tool has a stabilising guide pipe 7 which ensures that the connecting element 14 with the pistons 4 is correctly drawn into the collecting cylinder 1. The four samples are drawn simultaneously into the four collecting cylinders 1 by a common plate 8 attached to all the connecting elements 14 by a second tool (not shown) located behind the sampling tool. This tool also has a built-in hydraulic pump (not shown) which delivers pressure for activating packers.

In the embodiment illustrated in fig. 3 it can be seen that six pistons 4 are exposed to the fluid flow from the isolated zone through the collecting chamber 6 when one or more samples are taken at a position in the well.

Fig. 4 illustrates another embodiment of the tool. The difference here is that only one piston at a time is exposed to the fluid through-flow in the collecting chamber from the isolated zone. The figures show one position of pistons and connecting element 14 where a piston has just been inserted in the collecting cylinder 1 and a piston is located on the edge of the guide pipe 7. In this variant the collecting chamber 6 is formed by the wall of the pipe wherein the tool is employed, two radial surfaces 21, 22, which are formed by radial walls extending from an internal pipe which internally forms the flow channel 10 and externally forms an internal peripheral surface 23 of the collecting chamber together with two peripheral flange surfaces 25, 26 which form end surfaces in the longitudinal direction of the tool.

Fig. 5 illustrates a section of a portion of the sampling tool where packers 2 are activated and forwardly located flow zones pass through the flow channel 10 of the tool. The flow channel 10 is also provided with a funnel-shaped inlet 27 accomodating for the flow through the tool. In the detail figure it can also be seen that the guide pipes 7 are provided with a funnel-shaped outlet 18 and that the collecting cylinders are provided with a funnel-shaped inlet 19 to facilitate moving the pistons 4 in and out of these elements. In fig. 6 the upper partial section shows that all the pistons 4 are located in the guide pipe 7 and the lower partial section in the figure shows that all the sampling pistons 4 are retracted into the collecting cylinder 1 which stores the physical samples. When all the samples are retracted into the collecting cylinder, the pistons will be located between drain screws 9. These drain screws 9 may also be spring- based safety valves. These safety valves will be adjusted to a dump pressure which will be a slightly lower pressure than the pressure required for a leakage to occur in the piston seals between the pistons. The reason for providing safety valves connected with each sample chamber is that gas samples and oil samples with a high gas content will expand in volume when the tool has to be pulled upwards and out of the well.

It is also possible to lay smaller hoses/pipes from the points between pistons 4 for a degasification in the tool behind the actual sampling part. This will provide an extended cavity which is larger than the volume in the collecting cylinder and the safety valve is then placed at the top of this cavity. This will provide better degasification and output in order to preserve the greatest possible volume of the fluids.

A portion of the volume from the samples taken down in the well will be lost on the way up. Due to the fact that the safety valves are adjusted just below the maximum pressure tolerated by the piston seals, the pressure inside the container will be a great deal higher than the atmospheric pressure up on the platform. The sampling tool is equipped with a pressure sensor which registers current pressure down in the well when the actual sampling is taking place. By means of an analysis tool we can measure the remaining gas composition in the samples. By taking account of the pressure set on the safety valves, and including the pressure registered during the sampling, on this basis we can calculate the original composition at the moment of sampling.

Fig. 7 illustrates a third embodiment of the sampling tool according to the invention, where one end of the tool is cut off showing a cross section through the tool. In this embodiment there is a set consisting of collecting cylinder, pistons and collecting chamber. The collecting chamber comprises an outer partial chamber 61 round the circumference of the tool with circumferential seals 2 (only one shown) located at two ends of this partial chamber 61, where this partial chamber 61 is connected to a connecting chamber 62 via slot 64, where the connecting chamber 62 leads to an inner partial chamber 63. In this inner partial chamber are mounted pistons 4 which are moved from this centrally located partial chamber 63 into a centrally located collecting cylinder 1. Upstream production flow is guided through the tool through several flow channels 10, provided between the outer partial chamber 61 and the inner partial chamber 63. Fig. 8 illustrates a further variant of a tool according to the invention. In this variant a collecting cylinder 1 is also provided, connected to a connecting element 14 with pistons 4 mounted in a guide pipe 7 in a collecting chamber 6. In this embodiment the collecting chamber 6 is formed round the circumference of the tool between two seals 2. In fig. 9 a cross section of the main body 20 is illustrated in this variant between the seals 2, where it can be seen that the collecting chamber 6 comprises an outer partial annular chamber 66 connected with a partial chamber 65, which is substantially U-shaped in cross section. The guide pipe 7 with the pistons 4 is disposed in the inner bottom of the U-shaped partial chamber 65. The part of the internal opening of the main body which does not form the U-shaped partial chamber 65 forms the flow channel 10 for upstream production in the well.

Fig. 10 illustrates a portion of a sixth embodiment of a sampling tool according to the invention. The principles of this tool are illustrated in the sketch in fig. 11, where it can be seen that the main body 20 of the tool has a long extension in the longitudinal direction of the pipe 100 wherein the sampling tool is located. In this embodiment the collecting chamber comprises a first outer peripheral partial chamber 61, a transfer and/or connecting chamber 62 and a second centrally located partial chamber 63. The inlet 11 to this collecting chamber is formed by the inner wall of the pipe 100, with the openings 101, and the first partial chamber is further defined by the inner wall of the pipe 100, a radial surface 21 and radial surface 22 and a peripheral surface 23 of the main body, provided between two peripheral packers 2 for providing a seal against the inner wall of the pipe 100. In this embodiment the transfer chamber 62 is formed, among other things, by pipe 67 which extends in a substantially axial direction, but may extend in other directions as a combination of partly axial and partly radial. The second partial chamber 63 comprises outlet 12 at the downstream end of this second partial chamber 63. Due to the fact that the collecting cylinder 1 has a central location and on account of the distance of this collecting cylinder 1 from the wall of the pipe 100, the sampling tool is also shown to comprise a centralising device 30. In fig. 10 the tool is shown without packers with the result that instead the surface 2a of the main body 20 is shown adapted for the packers. The invention has now been explained with reference to several embodiments. A person skilled in the art, however, will understand that several modifications and alterations may be made to the embodiments illustrated which lie within the scope of the invention as defined in the following claims. The tool may be constructed with one, two, three, four or more separate sectors round the circumference of the tool. The flow channel may be one or more openings, which may be placed centrally or located between partial chambers, or eccentrically in the tool. The collecting chamber may comprise several partial chambers and connecting chambers, where these may extend radially and/or axially relative to the tool. Collecting cylinder and pistons may have any cross section whatever as long as they are compatible with one another. Variants of the tool may well be envisaged where the guide pipe is not relatively located in the collecting chamber but forms a part of the main body or a variant where the guide pipe is omitted. Variants may be envisaged where the pistons may be moved relatively to one another until they are inserted in the collecting cylinder where they have a given relative spacing for sampling.

The invention will make it possible to conduct local sampling down in the production zone in hydrocarbon-producing wells in a simple manner. These samples will be valuable for analyses and verification since sampling has been carried out at local sites in the production tubing, and since there is no admixture of other flowing fluid phases from forwardly located production zones in the front edge of the sampling tool. The invention can take several samples simultaneously, where these samples are radially divided sectors in the production tubing's sampling point.

Claims

1. A sampling tool for extraction of production samples in a well, characterised in that it comprises at least one set of a collecting cylinder (1), a collecting chamber (6) formed during use, with at least one inlet (1 1) and one outlet (12), and at least two pistons (4), arranged to be moved from the collecting chamber (6) into the collecting cylinder (1) at a given distance apart, and a flow channel (10) through the tool.

2. A sampling tool according to claim 1, characterised in that it comprises a main body (20) with a longitudinal axis (13), where surfaces (21, 25, 26) of the main body (20) together with an inner wall of a pipe and sealing devices (2, 3), mounted at outer points of the surfaces to provide a seal against an inner wall of a pipe during use, form the collecting chamber (6).

3. A sampling tool according to claim 1, characterised in that the pistons (4) are mounted on a connecting element

(14).

4. A sampling tool according to claim 1, characterised in that the collecting cylinder (1) is composed of a pipe which is open (15, 16) at both ends.

5. A sampling tool according to claim 1, characterised in that the collecting cylinder (1) comprises at least one drain screw (9) mounted in an area between two pistons (4) when the pistons (4) are completely inserted into the collecting cylinder (1).

6. A sampling tool according to claim 1, characterised in that it comprises a pipe (7) disposed at least partly inside the collecting chamber (6) for storing the pistons (4).

7. A sampling tool according to claim 1, characterised in that it is designed in such a manner that during use at least two collecting chambers (6) are formed round the circumference of the tool, where the tool further comprises at least one flow channel (10).

8. A sampling tool according to claim 1, characterised in that the flow channel (10) is provided centrally in the main body (20).

9. A sampling tool according to claim 2, characterised in that the sealing devices (2, 3) are fluid-activated seals.

10. A method for extraction of samples in a well by means of a tool according to claim 1 , where the tool is lowered into the well and moved to the location of interest for sampling, characterised in that the production is permitted to flow through the collecting chamber (6), where the pistons (4) are then moved from a position in the collecting chamber (6) to a position in the collecting cylinder (1), thereby causing a sample at the relevant location to be enclosed in the collecting cylinder (1) between two pistons (4), whereupon the tool is removed from the well and the collecting cylinders (1) can be transported to the desired location for analysis of the samples.

11. A method according to claim 11 , characterised in that the tool comprises three or more pistons (4) in a row, with the result that when the two first pistons (4) are located in the collecting cylinder (1), the tool is moved to a new position whereupon the pistons (4) are moved further into the collecting cylinder (1) until another piston (4) is located in the collecting cylinder, and this process is repeated until the desired number of pistons (4) have been moved into the collecting cylinder.

12. A method according to claim 11 or 12, characterised in that production in the well upstream of the tool is permitted to flow through the tool and thereby does not influence the samples taken in the collecting chamber.