Downhole washing tool

Abstract

A downhole tool for washing at least one annulus with a washing tool The washing tool including a valve adapted for splitting the fluid flow providing a pressure difference in the at least one annulus. The pressure difference increases available lifting force for the particles in the annulus during the washing operation. The valve may be a split flow valve. It is also disclosed methods for washing at least one annulus in a wellbore by use of the washing tool. The downhole tool may be used in a perforate, wash and cement operation performed in a single trip.

Description

INTRODUCTION The disclosure concerns a downhole washing tool and a method for washing a borehole. The disclosure also concerns a method for performing a perforate, wash and cement operation in a single trip in a wellbore. BACKGROUND In plug and abandonment operations (P&A), the annulus behind the casing in the well is cleaned before the well is sealed off. Before cleaning the annulus, the casing is perforated. A washing tool washes the annulus behind the casing to clean the annulus for mud, debris and dirt. A clean wellbore is important for the final quality of the cement plug sealing off the well. Some wells may be difficult to wash; e.g. wells with a packed annulus or wells with a second annulus. SUMMARY OF THE INVENTION The invention provides a downhole tool for washing at least one annulus. In a first aspect, the downhole tool comprising a washing tool and a valve. The valve is adapted for creating a pressure difference in the at least one annulus. The downhole tool may include a further washing tool. In a second aspect, the downhole tool comprising a washing tool, a further washing tool, and a valve. The valve is adapted for splitting the fluid flow between the washing tool and the further washing tool. The valve may be integrated in the washing tool or in the further washing tool. The washing tool may be a cupless tool and the further washing tool may be a cup tool. The washing tool may be a cup tool and the further washing tool may be a cupless tool. The washing tool may be a cupless tool or a cup tool. The washing tool may include at least one pressure sensor. The further washing tool may include at least one pressure sensor. The washing tool may include at least one temperature sensor. The further washing tool may include at least one temperature sensor. In a further aspect, the invention provides a method for washing at least one annulus in a wellbore by use of a downhole tool comprising a washing tool and a valve. The method comprising running the downhole tool in hole, positioning the washing tool in a perforated zone of the wellbore, and controlling the valve to create a pressure difference in the at least one annulus. The downhole tool may include a further washing tool, the method comprising: controlling the valve to create a pressure difference in the at least one annulus between the washing tool and the further washing tool. The valve may be controlled based on at least one measured pressure. The valve may be controlled based on at least one measured temperature. The valve may be controlled splitting the flow between the washing tool and the further washing tool. In an even further aspect, the invention provides a method for performing a perforate, wash and cement operation in a wellbore in a single run. The method comprising: running a downhole tool in hole; perforating a planned barrier zone; positioning the downhole tool in the perforated zone; controlling a valve of the downhole tool to create a pressure difference in the at least one annulus; washing at least one annulus of the wellbore; and setting a cement barrier in the at least one annulus. The valve of the downhole tool may be controlled splitting a washing fluid flow between a first washing tool and a second washing tool of the downhole tool, wherein the first washing tool is arranged below the second washing tool. The method may further comprise controlling the valve during washing of the at least one annulus to increase or decrease the flow of washing fluid to the first washing tool and the second washing tool. The valve may be controlled based on at least one measured pressure. The valve may be controlled based on at least one measured temperature. A high viscosity pill may be provided in the annulus to assist in the washing of the annulus. A mechanical restriction may be provided in the annulus to increase a fluid velocity in the annulus in the area of the restriction. The mechanical restriction may be provided by the washing tool. The downhole tool and the methods disclosed above may be used in a P&A operation. Example operational procedure may be as follows: • Run in hole and perforate planned barrier zone. • Operation might include setting a cement barrier in the main bore below the perforated zone. • There can be either a single tubular with single annulus or a dual tubular string with dual annulus scenario. • Position combination of cup and cupless tool somewhere in the perforated zone (top, bottom or in the middle). • Split flow between cup tool and cupless tool (any split; e.g. 50 / 50). The split flow can be adjusted during operation to either increase or decrease for either cup or cupless tool. • Pressure data used to analyze washing performance and cement placement. • Tool moving downwards or upwards over the perforated interval to wash the annulus clean. • Operation might include spotting high viscosity pill in the annulus as cement base or creating a mechanical restriction in annulus as cement base. • Cement perforated and washed section in the annulus and main bore. • Completed operation. Split flow effect: (1) High pressure between cups, open perforations channel pressure into annulus space (2) Flow through cupless tool with high velocity upwards around tool body causing low static pressure in annulus. Combined effect of split flow through cup and cupless tool is a pressure difference in the annulus with high pressure and high velocity close to the cup tool and low pressure close to the cupless tool increasing lifting force and velocity in the annulus. The washing tool together with the valve splitting the flow creates a pressure difference in the annulus between a high-pressure zone Phigh and a low-pressure zone Plow. The effect of the pressure difference in the annulus combined with the flow rate increases the available lifting force for the washing fluid in the annulus of the well. The washing tool improves the washing efficiency especially in tightly packed annulus (<10-20mV) and in dual annulus wells. Particles in the annulus will be lifted as a result of the combined effect of flow rate and pressure difference between the high-pressure zone and the low-pressure zone. BRIEF DESCRIPTION OF DRAWINGS Example embodiments are described with reference to the following drawings, where: Fig. 1 is a schematic illustration of an exemplary well with a perforated casing and an annulus to be washed by an exemplary washing tool, where the washing tool has set up a pressure difference in the annulus between a high-pressure zone Phigh and a low-pressure zone Plow. Fig.2a is a schematic illustration of an exemplary washing tool provided by a cupless tool and a cup tool and a valve. Fig.2b is a schematic illustration of an exemplary washing tool provided by a cup tool and a cupless tool and a valve. Fig.2c is a schematic illustration of an exemplary washing tool provided by a single cup tool and a valve. Fig.2d is a schematic illustration of an exemplary washing tool provided by a single cupless tools and a valve. DETAILED DESCRIPTION Example embodiments are described with reference to the drawings. The same reference numerals are used for the same or similar features in all the drawings and throughout the description. The example embodiments are examples only and not limiting for the disclosure. A wellbore 1 to be washed is illustrated in Fig. 1 The wellbore has an annulus 2 provided with a casing 3. The annulus may also include a second annulus. A downhole tool is arranged in the well. The downhole tool may be run on drillpipe or coiled tubing. The downhole tool may be a perforate, wash and cement tool. The downhole tool may perform a perforate, wash and cement operation in a single trip. The casing in Fig. 1 has been perforated by a perforation tool. The perforations are illustrated by the dotted lines in the casing 3 in Fig. 1. The perforation tool may be a part of the downhole tool. The downhole tool includes a washing tool 4. The downhole tool includes a valve 7. The valve is adapted for creating a pressure difference in the at least one annulus. The washing tool 4 is provided with the valve 7. The valve 7 is adapted for controlling the flow of washing fluid to the washing tool 4 to set up a pressure difference in the annulus between a high-pressure zone Phigh and a low-pressure zone Plow. The valve may be a split flow valve 7. The valve may be controlled during operation to either increase or decrease the flow of washing fluid to the washing tool. As illustrated in Fig. 1, there is a pressure difference in the annulus between a high-pressure zone Phigh and a low-pressure zone Plow. A washing fluid flow path is illustrated with the dotted line going from the high-pressure zone Phigh to the low-pressure zone Plow. The washing tool 4 illustrated in Fig. 1 includes a first washing tool 5 and a second washing tool 6. The valve splits the fluid flow between the first washing tool and the second washing tool. The first washing tool 5 is the bottom part and the second washing tool 6 the upper part of the washing tool in Fig. 1. The first washing tool 5 is provided with cups. The second washing tool 6 is a cupless washing tool. The first washing tool may be a cupless washing tool. The second washing tool may be provided with cups. The first washing tool and the second washing tool are connected to each other. The washing tool 4 is provided with a valve 7. The valve 7 splits the flow of washing fluid between the first washing tool 5 and the second washing tool 6. The valve may be integrated in the first washing tool. The valve may alternatively be integrated in the second washing tool. The valve may be a split flow valve 7. The valve may be controllable. The valve can be controlled during operation to either increase or decrease the flow of washing fluid for either the first washing tool or the second washing tool. The valve dividing the washing fluid flow between the first and the second washing tool is controlled to provide: (1) A high pressure zone in the annulus in the area where the washing fluid exits the first washing tool. (2) A washing fluid flow emitted from the second washing tool with a high velocity upwards around the downhole tool body causing low static pressure in the annulus. The control of the valve may depend on several parameters. The valve splits the flow of washing fluid between the first and second washing tools. The split may have any value and non-limiting examples may e.g. be a 50 / 50, 75 / 25, 20 / 80 split. The split of washing fluid flow between the first and second washing tool depends on a number of factors e.g. the washing fluid used, the properties of the annulus, and pressure and temperature in the zone to be cleaned. The combination of a high-pressure zone in the area of the bottom washing tool and a low static pressure zone in the area of the upper washing tool results in a circulation from the high-pressure zone to the low static pressure zone in the annulus. The pressure difference in the annulus increases an available lifting force in the annulus of the well. Particles in the annulus will also be lifted upwards in the annulus by the lifting force provided by the pressure difference in combination with the available flow rate. The combination of the high-pressure zone and the low-pressure zone also increases the flow rate in the annulus. The use of two washing tools and the valve splitting the flow increases the energy supplied by the washing fluid into the annulus. As illustrated in Fig. 1 a pressure sensor P is provided on the cup tool and a pressure sensor P is provided on the cupless tool. At least one pressure sensor P may be provided on the washing tool. At least one temperature sensor T, may be provided on the washing tool. The pressure sensor(s) and / or temperature sensor(s) may monitor washing job performance. A pressure sensor and / or a temperature sensor, may be provided on the first washing tool and / or the second washing tool, to monitor the pressure and / or the temperature. The pressure and / or the temperature may be monitored in the area where the washing fluid exits the washing tool. The washing tool may include a pressure sensor measuring the internal pressure of the flow of washing fluid in the first washing tool and / or the second washing tool. Pressure data obtained from the pressure sensors may be used to analyze the washing performance. Temperature data obtained from the temperature sensors may be used to analyze the washing performance. The valve may be controlled based on at least one of the pressure data, temperature data or the parameters for the washing performance. The washing tool may move downwards or upwards over the perforated interval to wash the annulus clean. Some wells may be difficult to wash; e.g. wells with a packed annulus or wells with a second annulus. It may be difficult to initiate the washing process in a packed annulus. It may be difficult to clean out a highly packed material. Dirt and mud may also clog the perforations in the tubular (s). The particles should be removed from the planned zone and moved upwards in the annulus. There may be little available space for the washing fluid to flow. A dual annulus wellbore may also require more energy to be washed. The perforations in the tubular may be clogged with particles or debris. The annulus may also be packed with particles or debris. The high-pressure zone also enables opening of the perforations in the tubular into the annulus space in this zone. The high-pressure washing fluid flows into the packed annulus and cleans out particles and debris in the packed annulus. In case of a second annulus in the well, the high pressure is high enough for the washing fluid to flow through the perforations in the second tubular, clean the second annulus and set up an upwards flow in the annulus. The creation of a high-pressure washing fluid zone has an impact of opening the perforations in the tubular and increasing the washing effect of the annulus(es) in the high-pressure zone. The pressure difference between the high-pressure zone and the low-pressure zone may also stimulate the start of the washing process particularly in packed wells. The washing fluid is pumped down an interior channel of the washing tool at high pressure. As illustrated in Fig. 1, the first washing tool provided in the bottom part of the washing tool, is a cup tool. The cups 8 when activated and engaging the inner walls of the annulus, create a sealed space inside the casing providing a high-pressure zone of washing fluid. The cup tool in Fig. 1 has two pairs of cups, but only one set of cups may be also be used. The washing fluid flows out of the washing tool through openings in the area between the cups 8 (the high-pressure area). The openings for the outflow of the washing fluid may be a plurality of radial holes arranged between the cups of the washing tool. The washing fluid flow in the high-pressure zone is forced radially outward through the perforations 10 in the casing and into the annulus. A pressure P and / or a temperature sensor may be provided between the cups 8 of the cup tool 5. The second washing tool 6 provided in the upper part of the washing tool, may be a cupless washing tool. The cupless washing tool is in Fig. 1 provided with ports 11 or nozzles outputting the washing fluid at high speed and high pressure. The ports or nozzles may be in the form of fluid jets. In Fig. 1, the cupless washing tool is provided with helical wings 9. The helical wings are arranged externally on the tubular body of the cupless washing tool. Nozzles / ports 11 emitting washing fluid are provided on the helix-shaped wings. The tubular member with the helixshaped wings may be provided with a central channel and a flow control sleeve for controlling a radial flow of washing fluid to the nozzles. The nozzles may be inserted at an angle into the helical wings enabling the washing fluid to be directed with a significant tangential component in order to initiate a toroidal movement of the fluid flow emitted from the nozzles. The toroidal flow would be in the same direction as the helical wings. A high-pressure washing fluid may be flushed out through the nozzles and create a high-pressure flushing force from the washing fluid in the wellbore. The cupless tool 6 may have a large outside diameter (OD). The combination of the angled flow ports, i.e. having nozzles directed with a tangential component, and preferably with a large outside diameter (OD) of the cupless washing tool, creates a powerful cyclone effect. The helix shaped wings 9 provide a mechanical restriction of the annulus. A large OD provides a mechanical restriction of the annulus. According to the Bernoulli principle an increase of speed of a fluid flow occurs at the same time as a decrease in static pressure. A fluid flowing in a pipe will have a higher fluid velocity in a smaller cross-section of the pipe causing a lower static pressure in the small cross-section than in the larger cross section of the pipe. Above the helical wings of the cupless washing tool there will be a high fluid velocity due to the smaller cross-section of the annulus causing a low static pressure Plow. The smaller cross-section is provided by the helical wings. Between the helical wings on the cupless washing tool, the fluid will have a slower fluid velocity due to a larger cross-section and thereby a higher static pressure Phigh for the fluid. This has the effect of creating an upwards fluid flow along and above the cupless tool creating a low-pressure zone above the cupless tool. A pressure sensor P is in Fig. 1 integrated in the cup tool in the area between the two cups for measuring the pressure in the sealed space between the two cups. A temperature sensor T may also be arranged on or integrated in the cup tool in the area between the two cups. A second pressure sensor P is in Fig. 1 integrated in the cupless tool for measuring the pressure in the annulus in the area of the cupless tool. In Fig. 1, the second pressure sensor is arranged above the fluid exit area (above the wing area) of the cupless tool. A temperature sensor may also be arranged on or integrated in the cupless tool. The valve 7 splitting the flow between the cup tool and the cupless tool may be integrated in the cupless tool or integrated in the cup tool. The valve may be a splitflow valve. As illustrated in Fig. 1 the valve is integrated in the cupless tool. The valve may have different positions and / or functions during a perforate, wash and cement operation. The valve is open for circulating bottoms up and cementing in a blank casing. The flow ports on the cupless tool functions as diversion ports for the washing fluid flow. The flow ports / diversion ports are closed when the valve is open. The valve is closed for pumping washing fluid between the cups of the bottom cup washing tool. The valve is closed and flow ports / diversion ports are open to set up the low-pressure zone. The downhole tool illustrated in Fig. 1 may also be run up-side down with the cup tool above the cupless tool. An example of a perforate, wash and cement operation in a borehole may be as follows: • The downhole tool is run in hole (RIH). The borehole has either a single tubular with a single annulus or a dual tubular with a dual annulus scenario. • The casing(s) is perforated in the planned barrier zone of the borehole. • (Optional) Operation might include setting a cement barrier in the main bore below the perforated zone before washing the perforated zone. • The washing tool combination of the first and the second washing tool is positioned somewhere in the perforated zone (e.g. top, bottom or in the middle of the zone). • The valve in the washing tool combination is controlled providing a split flow of the supplied washing fluid between the first and the second washing tool (any split, e.g. 50 / 50, 40 / 60, 75 / 25;). The split flow can be adjusted during operation to either increase or decrease the washing fluid flow provided to the first or the second washing tool based on at least the measured pressure by the pressure sensors. The split flow may additionally be controlled by e.g. temperature and / or the washing performance. • Moving the downhole tool downwards or upwards over the perforated zone to wash the annulus clean. • Pressure data used to analyze washing performance and cement placement. • (Optional) Operation might include spotting high viscosity pill in the annulus cement base or creating a mechanical restriction in annulus as a cement base. • Cement the perforated and washed zone in the annulus and main bore. • Completed operation. The perforate, wash and cement operation may be performed by the downhole tool in a single trip. Exemplary non-limiting embodiments of a downhole tool for washing an annulus is illustrated in Fig.2a-2d. In Fig.2a, the first washing tool is a cupless tool 6 and the second washing tool is a cup tool 5. A valve 7 splitting the flow of washing fluid is integrated in the cupless tool. In Fig.2b, the first washing tool is a cup tool 5 and the second washing tool is a cupless tool 6. A valve 7 splitting the flow of washing fluid is integrated in the cupless tool. In the exemplary embodiments illustrated in Fig.2a and 2b, the valve 7 splits the flow of washing fluid between the first and the second washing tool. In Fig. 2c, the washing tool is only one washing tool in the form of a cup tool 5. A valve adapted for creating a pressure difference in the annulus is integrated in the cup tool 7. The valve 7 may be positioned either above or below the cup tool. The valve 7 may be arranged in the upper end or bottom end of the cup tool as illustrated in Fig.2c. In Fig.2d, the washing tool is only one washing tool in the form of a cupless tool 6. A valve 7 adapted for creating a pressure difference in the annulus is integrated in the cupless tool. The valve 7 may be positioned either above or below the cupless tool. The valve may be arranged in the upper end or bottom end of the cupless tool as illustrated in Fig.2d. In the exemplary embodiments illustrated in Fig.2c and 2d, where the washing tool is a single washing tool, the downhole tool is provided with a port directing a portion of the washing fluid into the annulus. The valve may be provided with the port. The valve may be positioned either above or below the single washing tool. The port directs a portion of the washing fluid between the tool / drill pipe and the casing. The valve 7 splits the flow of washing fluid between the single washing tool and the port. The flow that passes through the port would then go straight up and would allow circulation. This would be advantageous in tightly packed annulus scenarios when it is difficult to start circulation. The valve 7 may be controlled to split a portion of the washing fluid flow between the single washing tool and the port. The split may be any split sufficient to provide an intended effect. In the embodiment illustrated in Fig.2c, the washing tool is provided by a single cup tool. The valve 7 may be positioned either above or below the cup tool. The valve is controlled to split the flow of washing fluid between the cup tool and the port. This would be advantageous in tightly packed annulus scenarios when it is difficult to start circulation between the cups of the cup tool. In the embodiments in Fig.2c and 2d, pressure sensors P and / or temperature sensors T, may be provided on the washing tool to monitor washing job performance. A pressure sensor and / or a temperature sensor, may be provided to monitor the pressure and / or the temperature, in the area where the washing fluid exits the washing tool. The washing tool may include a pressure sensor measuring the internal pressure of the flow of washing fluid. Pressure data obtained from the pressure sensors may be used to analyze the washing performance. Temperature data obtained from the temperature sensors may also be used to analyze the washing performance. The valve may be controlled based on the pressure data. The valve may also be controlled by the temperature data and / or the parameters for the washing performance. The washing tool may move downwards or upwards over the perforated interval to wash the annulus clean. An example of a perforate, wash and cement operation in a borehole by use of a single cup tool or single cupless tool as in Fig.2c or Fig.2d may be as follows: • The downhole tool is run in hole (RIH). The borehole has either a single tubular with a single annulus or a dual tubular with a dual annulus scenario. • The casing(s) is perforated in the planned barrier zone of the borehole. • (Optional) Operation might include setting a cement barrier in the main bore below the perforated zone before washing the perforated zone. • The washing tool is positioned somewhere in the perforated zone (e.g. top, bottom or in the middle of the zone). • The valve in the washing tool is controlled to provide a split flow of the supplied washing fluid between the single washing tool and the port of the valve (the split of flow may e.g. be 50 / 50, 60 / 40; 75 / 25;). The split of the flow can be adjusted during operation to either increase or decrease the washing fluid flow provided to the single washing tool and port. The split of washing fluid flow may be adjusted based on at least the measured pressure by the pressure sensors. The split flow may additionally be controlled by e.g. temperature and / or the washing performance. • Moving the downhole tool downwards or upwards over the perforated zone to wash the annulus clean. • Pressure data used to analyze washing performance and cement placement. • (Optional) Operation might include spotting high viscosity pill in the annulus cement base or creating a mechanical restriction in annulus as a cement base. • Cement the perforated and washed zone in the annulus and main bore. 5      • Completed operation. The perforate, wash and cement operation may be performed by the downhole tool in a single trip. 10 Having described example embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. These and other examples illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following is claims.

Claims

1. A downhole tool for washing at least one annulus comprising:- a washing tool; and- a valve adapted for creating a pressure difference in the at least one annulus.

2. A downhole tool for washing at least one annulus comprising:- a washing tool,- a further washing tool, and- a valve adapted for splitting the fluid flow between the washing tool and the further washing tool.

3. Downhole tool according to claim 1, further comprising a further washing tool.

4. Downhole tool according to one of claims 1-3, wherein the valve is integrated in the washing tool or in the further washing tool.

5. Downhole tool according to one of claims 1-4, wherein the washing tool is a cupless tool and the further washing tool is a cup tool.

6. Downhole tool according to one of claims 1-4, wherein the washing tool is a cup tool and the further washing tool is a cupless tool.

7. Downhole tool according to claim 1, wherein the washing tool is a cupless tool or a cup tool.

8. Downhole tool according to one of claims 1-7, wherein the washing tool further comprising at least one pressure sensor.

9. Downhole tool according to one of claims 2-, wherein the further washing tool comprising at least one pressure sensor.

10. Downhole tool according to one of claims 1 -8, wherein the washing tool comprising at least one temperature sensor.

11. Downhole tool according to one of claims 2-10, wherein the further washing tool comprising at least one temperature sensor.

12. A method for washing at least one annulus in a wellbore by use of a downhole tool comprising a washing tool and a valve, the method comprising:- running the downhole tool in hole,- positioning the washing tool in a perforated zone of the wellbore,- controlling the valve to create a pressure difference in the at least one annulus.

13. A method according to claim 12, wherein the downhole tool comprising a further washing tool, the method comprising: controlling the valve to create a pressure difference in the at least one annulus between the washing tool and the further washing tool.

14. Method according to claim 12 or claim 13, further comprising controlling the valve based on at least one measured pressure.

15. Method according to one of claims 12-14, further comprising controlling the valve based on at least one measured temperature.

16. Method according to one of claims 13-15, further comprising controlling the valve splitting the flow between the washing tool and the further washing tool.

17. A method for performing a perforate, wash and cement operation in a wellbore in a single run, the method comprising:- running a downhole tool in hole;- perforating a planned barrier zone;- positioning the downhole tool in the perforated zone;- controlling a valve of the downhole tool to create a pressure difference in the at least one annulus;- washing at least one annulus of the wellbore; and- setting a cement barrier in the at least one annulus.

18. A method according to claim 17, further comprising:controlling the valve of the downhole tool splitting a washing fluid flow between a first washing tool and a second washing tool of the downhole tool, wherein the first washing tool is arranged below the second washing tool.

19. Method according to claim 18, further comprising controlling the valve during washing of the at least one annulus to increase or decrease the flow of washing fluid to the first washing tool and the second washing tool.

20. Method according to one of claims 17-19, further comprising controlling the valve based on at least one measured pressure.

21. Method according to one of claims 17-21, further comprising controlling the valve based on at least one measured temperature.

22. Method according to one of claims 17-21, further comprising providing a high viscosity pill in the annulus to assist in the washing of the annulus.

23. Method according to one of claims 17-22, further comprising establishing a mechanical restriction in the annulus to increase a fluid velocity in the annulus in the area of the restriction.

24. Method according to claim 23, wherein the mechanical restriction is provided by the washing tool.

25. Use of the downhole tool according to claim 1 or the method according to claim 12 or the method according to claim 17 in a P&A operation.

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