Method for subsea cementing

Abstract

A casing is cemented in a wellbore by primping a fluid into the casing. RFID tags are suspended in the fluid. The fluid with suspended RFID tags travel downwardly through a drill pipe and the casing and then upwardly in an annulus between the casing and the wellbore to the wellhead. A sensor is used to detect RFID tags exiting the wellhead at the seafloor.

Description

METHOD FOR SUBSEA CEMENTINGFIELD OF THE INVENTION

[0001] The present invention relates to the field of subsea wellbore construction and completion operations, and, in particular, to subsea cementing operations.BACKGROUND OF THE INVENTION

[0002] In wellbore construction and completion operations, cementing is performed to anchor a well casing in a wellbore by filling an annulus surrounding the casing with cement. A cement slurry is circulated downhole through the casing and then upwards in the annulus to the top of the wellbore.

[0003] In subsea operations, especially in deepwater applications, drilling operations are often conducted without a riser. Accordingly, when cementing, the circulating cement slurry is driven upward to a subsea wellhead and flows outward from the wellhead through side outlet valves.

[0004] The cementing is continued until cement exiting the wellhead is detected. In conventional processes, the exiting cement is detected by visually inspecting for a dye or by measuring pH of the stream from the wellhead outlet valve.

[0005] A problem with the dye is that visibility7is impeded in the subsea environment, and, in particular, when the seafloor is disturbed by the fluid flow, creating clouds of particulates at the wellhead. As well, the dye may become diluted in the pumping operation making visual inspection even more challenging.

[0006] A drawback with the alternate solution of using a pH meter is that the meter must be in contact with the flowing stream, which contains solids, that may damage or clog the meter.

[0007] RFID tags have been contemplated for other aspects of the drilling operation. For example, US77125227, US8162050, US8291975, US8297352, US8297353 and US9194207 describe servicing a wellbore using a sealant composition comprising one or more MEMS sensors. Related US8083849 and US8162055 describe increasing the setting rate of a cement by activating a device with a wireless signal. Related US8342242 describes placing a MEMS sensor in a subterranean formation to detect a location of the wellbore composition (drilling fluid, spacer fluid, or cement). A plurality of interrogation units is spaced apart along the length of the wellbore in related US2011187556 and US9732584. Related US8302686 disclosesMEMS sensors disposed in a composite or resin portion of a casing, centralizer, plug, casing shoe or collar. Related US8316936 describes MEMS sensors and acoustic sensors that are interrogated by units spaced along the length of the wellbore. In related US9200500, the sensors are elastomer-coated. Related US9822631 describes MEMS sensors in surface wellbore operating equipment. Related US9394756 relates to operating a downhole assembly by operating an RFID sensor of the downhole assembly where the RFID sensor is responsive to RFID tags in an annulus surrounding the casing string in the borehole. In related US 9394784 and US9394785, azimuthally offset regions of the annulus are monitor with RFID tags. Related US9494032 discloses a communication assembly supported by a casing string. The communication assembly is configured to obtain information associated with RFID tags in an annulus surrounding the casing string when in a borehole. Related US9879519 describes a fluid sensing component supported by a casing string in a borehole with pairs of electrodes for measuring impedance of fluid in the annulus between the casing string and formation sidewalls. Related US 10358914 describes a method for detecting RFID tags in a borehole environment by scanning at a plurality of frequencies in a portion of the annulus between the casing string and the borehole.

[0008] Similarly, US10815768 describes a method of detecting RFID tags in a borehole by scanning in the annulus surrounding a casing string or in the interior of a casing string to detect a first frequency for a first type of RFID tag and a second frequency for a second type of RFID tag.

[0009] US11118446 describes a drilling assembly connected between a drilling platform and a wellhead. A reader group is located at a position along a riser of the drilling assembly to read information from RF tags in the riser relating to parameters of the returning drilling fluid in the riser.

[0010] Hannegan et al. (US9249646, 2 Feb 2016) relates to managing pressure cementing. Flow of fluid displaced from the wellbore is controlled to control pressure of the annulus between the tubular string and the wellbore. In one embodiment, the curing of the cement slurry is monitored by pumping a RFID tag into a second annulus between the drill string and the tubular string and communicates with cement sensors while returning through the second annulus.

[0011] There remains a need for improving the cementing operations in subsea environments.SUMMARY OF THE INVENTION

[0012] According to one aspect of the present invention, there is provided a method for cementing a casing in a subsea wellbore, comprising: providing a casing connected to a wellhead, the wellhead positioned at a seafloor; pumping a fluid through a drill pipe into the casing to travel downwardly through the casing and then upwardly in an annulus between the casing and the wellbore to the wellhead; adding a plurality of RFID tags to the fluid; providing a sensor for detecting one or more of the plurality of RFID tags; and detecting one or more of the plurality of RFID tags by the sensor at the seafloor.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The method of the present invention will be better understood by referring to the following detailed description of preferred embodiments and the drawings referenced therein, in which:

[0014] Fig. 1 is a schematic illustration of the method of the present invention in operation using an underwater vehicle for detecting RFID (radio-frequency identification) tags at a seafloor;

[0015] Fig. 2 is a schematic illustration of the method of the present invention in operation using a sensor mounted on the seafloor for detecting RFID tags at the seafloor; and

[0016] Fig. 3 is a schematic illustration of the method of the present invention in operation using a sensor mounted on a wellhead for detecting RFID tags at the seafloor.

[0017] It will be understood by those skilled in the art that the drawings are not to scale in order to show more clearly the various elements of the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention provides a method for cementing a casing in a subsea wellbore. RFID (radio-frequency identification) tags are provided in a fluid circulated to the wellbore. The fluid is pumped downhole until a sensor provided at the seafloor detects RFID tags flowing with the cement slurry at the seafloor. When the fluid is a cement slurry, detection of the RFID tags at the seafloor indicate that the cement slurry has circulated through the annulus of the wellbore and pumping of the cement slurry may then be stopped. When the fluid is a drilling fluid and / or a spacer fluid, detection of the RFID tags at the seafloor indicates the volume of cement slurry that should be pumped thereafter.

[0019] A cementing operation is used to anchor a casing in a wellbore during a drilling and completion operation. A challenge with marine environments, and in particular with deepwater environments, is the distance between the drilling rig and the seafloor, as well as the space limitations on a drilling rig. In view of the distance between the drilling rig and the seafloor, drilling and completion operation is often done without a riser, known to those skilled in the art as a riserless operation. A riserless operation then introduces a challenge of monitoring circulating cement slum to the top of the wellbore.

[0020] Those skilled in the art will calculate the amount of cement slurry needed to anchor the casing in the wellbore, factoring in the quality’ of the cement that can suffer from dilution with drilling mud in the wellbore for a period of time after pumping of cement slurry is conducted. However, due to the space limitations on the drilling rig, it is not efficient nor economical to over-pump the cement slurry to the wellbore. By improving the efficiency of the cementing operation, costs of transport of cement slurry to the rig can be reduced, thereby also reducing carbon footprint for the drilling and completion operation.

[0021] The method of the present invention adds RFID tags to a fluid that is pumped to the wellbore. The fluid may be selected from a cement slurry, a drilling fluid, and a spacer fluid. The fluid and RFID tags are pumped to the wellbore through a drill pipe to a casing that has been positioned in the drilling operation. The fluid and RFID tags exit the casing to the annulus between the wellbore and the casing. The fluid and RFID tags travel upwards in the wellbore to the wellhead at the seafloor and exit through a fluid outlet valve of the wellhead.

[0022] The method of the present invention improves efficiency of the drilling and completion operation by providing the correct amount of cement to anchor the casing in the wellbore without over-pumping cement. Beyond the cost and efficiency improvement, the disruption to the seafloor and / or to any infrastructure at the seafloor is reduced.

[0023] Referring now the drawings, Figs. 1 - 3 are schematic illustrations of embodiments of the present invention 10.

[0024] In the embodiment of Fig. 1. a cement slurry 12 is pumped through a drill pipe 16 from a rig (not shown) to a casing 18 in a wellbore 22. A plurality of RFID tags 14 are pumped with the cement slurry’ 12.

[0025] The RFID tags 14 may be added to the entire volume of the cement slurry 12, in an initial volume, or at intervals during pumping. Preferably, the RFID tags 14 are added to the cement slurry’ 12 at the start of the pumping step. More preferably, RFID tags 14 are added to the cement slurry 12 for an initial volume in a range of 10 - 50 bbls of cement slurry’ 12.

[0026] The cement slurry 12 and suspended RFID tags 14 travel downwardly through drill pipe 16 and the casing 18. The casing 18 was provided to the wellbore 22 in a prior drilling operation. The casing 18 is typically suspended in the wellbore 22 from a wellhead 24.

[0027] The cement slurry 12 and suspended RFID tags 14 then travel upwardly in the annulus between the wellbore 22 and the casing 18 to the wellhead 24. The excess cement slurry 12 flows out of the wellhead 22 through a fluid outlet valve 26. The plume 28 flowing out of the fluid outlet valve 26 contains the cement slurry 12 and any RFID tags 14 suspended in cement slurry 12. The RFID tags 14 are detected by a sensor 34 at the seafloor 32. As used herein 'at the seafloor” includes within a distance of the seafloor 32. for example, within 1 meter above the seafloor.

[0028] In the embodiment of Fig. 2, a drilling fluid 42 and a plurality' of RFID tags 14 are pumped into the wellbore 22 via the drill pipe 16 and casing 18. A cement slurry 12 displaces the drilling fluid 42 and RFID tags 14 towards the wellhead 24. The displaced drilling fluid 42 flows out of the wellhead 22 through a fluid outlet valve 26. The plume 28 flowing out of the fluid outlet valve 26 contains the drilling fluid 42 and any RFID tags 14 suspended therein. The RFID tags 14 are detected by a sensor 34 at the seafloor 32.

[0029] In the embodiment of Fig. 3, a spacer fluid 44 and a plurality of RFID tags 14 are pumped into the wellbore 22 via the drill pipe 16 and casing 18. The spacer fluid 44 is used to displace the drilling fluid (not shown in Fig. 3). A cement slurry 12 then displaces the spacer fluid 44 and RFID tags 14 towards the wellhead 24. The displaced spacer fluid 44 flows out of the wellhead 24 through a fluid outlet valve 26. The plume 28 flowing out of the fluid outlet valve 26 contains the spacer fluid 44 and any RFID tags 14 suspended therein. The RFID tags 14 are detected by a sensor 34 at the seafloor 32.

[0030] In the embodiment of Fig. 1, any RFID tags 14 in the plume 28 are sensed by a sensor 34 carried by an underwater vehicle 36. The underwater vehicle 36 may be a remote operated vehicle, an autonomous underwater vehicle, or a human-operated vehicle. The embodiment of the underwater vehicle 36 may be used whether the plume 28 contains cement slurry 12, drilling fluid 42, or spacer fluid 44.

[0031] In the embodiment of Fig. 2, any RFID tags 14 in the plume 28 are sensed by a sensor 34 mounted on a support 38 at the seafloor 32. The support 38 may be a platform anchored to the seafloor 32 or associated with existing infrastructure (not shown) at the seafloor 32. The embodiment of the support 38 for the sensor 34 may be used whether the plume 28 contains cement slurry 12, drilling fluid 42, or spacer fluid 44.

[0032] In the embodiment of Fig. 3, any RFID tags 14 in the plume 28 are sensed by a sensor 34 mounted on the wellhead 24. The embodiment of the sensor 34 mounted on the wellhead 24 may be used whether the plume 28 contains cement slurry 12, drilling fluid 42, or spacer fluid 44.

[0033] The sensor 34 of Figs. 1 - 3 communicates to a controller at the rig that fluid containing the RFID tags 14 has reached the seafloor.

[0034] Where the RFID tags 14 were suspended in the cement slurry 12, pumping may be stopped immediately or within a predetermined interval and / or volume to ensure a quality cement is formed. This would be determined according to best practices of the rig team, a well location, and / or properties of the specific formation in which the wellbore is formed.

[0035] Where the RFID tags 14 were suspended in the drilling fluid 42 and / or the spacer fluid 44, pumping of the cement slurry 12 may be continued for a calculated volume for displacement of the drilling fluid 42 and / or the spacer fluid 44. In these embodiments, the sensor 34 may be used to first detect presence of RFID tags 14 and then absence of RFID tags 14, thereby indicating that the cement slurry 12 has reached the seafloor 32. In another embodiment, the drilling fluid 42 may contain RFID tags 14 of a first frequency and the spacer fluid 44 may contain RFID tags 14 of a second frequency so that the sensor 34 can communicate the type of fluid in the plume 28.

[0036] In accordance with the present invention 10, the operators at the rig can confirm that the casing 18 is properly cemented in the wellbore 22. By reducing the amount of excess cement slurry 12 circulating out of the wellbore 22, the method of the present invention reduces costs associated with transporting and storing the cement slurry’ at the rig, as well as material costs. In addition, any disruption to the seafloor 32 and / or any related infrastructure at the seafloor 32 is reduced.

[0037] While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions, and improvements are possible. Various combinations of the techniques provided herein may be used.

Claims

CLAIMS1. A method for cementing a casing in a subsea wellbore, comprising: providing a casing connected to a wellhead, the wellhead positioned at a seafloor; pumping a fluid through a drill pipe into the casing to travel downwardly through the casing and then upwardly in an annulus between the casing and the wellbore to the wellhead; adding a plurality of RFID tags to the fluid; providing a sensor for detecting one or more of the plurality of RFID tags exiting the wellhead: and detecting one or more of the plurality of RFID tags by the sensor at the seafloor.

2. The method of claim 1, wherein the fluid is selected from the group consisting of drilling fluid, spacer fluid, and cement slurry’.

3. The method of claim 1, wherein the fluid is a cement slurry, and the method further comprises the step of discontinuing the flow of cement slurry after detecting the one or more of the plurality of RFID tags.

4. The method of claim 3, wherein the plurality' of RFID tags is added to an initial volume of the cement slurry7.

5. The method of claim 1 , wherein the fluid is selected from a drilling fluid and a spacer fluid, and, prior to the detecting step, the method further comprises the steps of pumping a cement slurry through the drill pipe to the casing to displace the fluid selected from drilling fluid and spacer fluid, and, after the detecting step, continuing pumping the cement slurry for a predetermined volume, and discontinuing the flow of cement slurry7.

6. The method of claim 4, wherein a first fluid is drilling fluid and a second fluid is spacer fluid, and wherein the plurality of RFID tags provided to the first fluid have a first frequency, and the plurality of RFID tags provided to the second fluid have a second frequency .

7. The method of claim 1, wherein the sensor is provided by an underwater vehicle selected from the group consisting of a remote operated vehicle, an autonomous underwater vehicle, and a human-operated vehicle.

8. The method of claim 1, wherein the sensor is mounted on the wellhead.

9. The method of claim 1, wherein the sensor is mounted at the seafloor proximate the wellhead.

10. The method of claim 1, wherein the sensor is configured to detect RFID tags flowing through a fluid outlet valve on the wellhead.

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