Technical field

The invention pertains to a seal assembly (10) on a tool, for example a washing tool in a pipe string such as coiled tubing or drill pipe string (0) in a well, in order to prevent fluid flow in at least one direction in a tool annulus through an annulus between the pipe string with the seal assembly (10), and a surrounding casing pipe (2), a so-called “casing”, or another pipe as a production pipe. More specifically, this pertains to properties of the seal assembly (10) enabling it to pass through a well restriction, for example a downhole safety valve DHSV, “Down Hole Safety Valve”.

The background of the invention

In connection with drilling- and well operations in the field of oil and natural gas production, seal assemblies (10), such as “swab cups", are utilized in order to achieve a sealing between a tool string lowered into a well pipe (such as casing pipes, production pipes, etc.) in a well and the well pipe.

The seal assembly often comprises an elastic seal element often formed as a cup where the inside of the cup shape is turned towards the direction where a seal to prevent fluid flow is desired. In connection with such operations, restrictions or limitations may occur in the inner diameter of the well pipe where the tool string is to be inserted. Traditional seal assemblies formed as a cup will often contort and/or become damaged when pressed through such a restriction.

US 2014/0238660 A1 describes a downhole sealing element comprising a cup section which also forms or comprises an elastic, deformable material.

US 2013/0264056 A1 describes a plug, where a seal cup and an external sealing to pump and seal the plug to a location in the well bore are utilized. The seal top is mounted in a ring bracket, and can slide over the tool mandrel.

US 2014/0158369 A1 describes a device to guide a tool string through a well bore that possesses a flow limiter which forms a sealing between the tool string and the well bore in an expanded state. The flow limiter can be bent and deformed in order to pass obstructions / restrictions along the well bore, and expand again when the obstruction has been passed.

US 2274940 A describes a seal and means for setting and releasing this to a casing pipe in a well while cement is transported into the well under pressure. The seal can be a flexible cup-shaped/conical seal, mounted in the one end through a ring bracket, and in the other end to a spring shaped to hold the seal in place and prevent it from contorting. The document NO 20171650 A1 describes a system and a method for cleaning annulus in a well. The tool comprises radially expandable collars/rings in the shape of reversely aligned seal cups, which form a sealing towards the pipe and thus a delimited pressure cavity between the seal tops, where fluid can flow via and out through a limited number of perforations, and out to the annulus to be washed.

A typical restriction can be a downhole safety valve (DHSV) in a production pipe. A downhole safety valve DHSV can possess an actuation sleeve for a leaf valve with a smaller size than the pipe in which it sits, and such a restriction can damage elastic seal elements, especially if the seal element is forced through with the sealing side first. Other types of restrictions in well bores may also occur.

A typical use of such seal assemblies comes in the form of a washing tool with reversely aligned seal assemblies surrounding a nozzle from the pipe mandrel in order to wash the annulus on the outside of a perforated well bore for subsequent cementation, or for washing out the annulus in order to loosen a cut well bore to be withdrawn from the well. The well bore is, as such, cut or perforated to facilitate fluid communication between the inside and the outside of the well bore. A tool string with a washing tool comprising two (or four) reversely aligned seal assemblies are guided down into the well bore and the two reversely aligned seal assemblies are arranged on each side of the cut or in the perforated section of the well bore. Fluid is pumped down through the tool string and out through the radial port between the two seal assemblies. The seal assemblies thus prevent the fluid from flowing up or down along the tool string, and the fluid will consequently have to flow through the cut or the perforations in the well bore. Such a washing tool is known from EP2569506. It is also known, beyond washing the casing pipe annulus, to cement the casing pipe annulus, and also indirectly the casing pipe through such a washing tool, from the applicant’s own patent EP3036395, so that a cement pin is formed in the well. It is a frequently common problem that seal assemblies are damaged when passing restrictions in the well. One way to test whether the seal assemblies are intact when lowered down the well and utilized for example for casing pipe annulus washing through perforations in the casing pipe, is to prepare the washing tool above or below the perforations, and place it in an intact casing pipe, and then pressurize it. In the event that there is sufficient pressure resistance in the drill pipe string, this would be an indication of intact seal assemblies, and one may proceed to wash, if necessary, cement through the perforations.

There is a need for a seal assembly which enables the possibility of passing a restriction in a well, and subsequently to create a seal between the tool string and a well pipe, with a larger, inner diameter than the aforementioned restriction. It is also a requirement that the seal assembly can pass through the restriction on its way out of the well too.

The purpose of the invention

One main purpose of the invention is to produce a seal assembly which is capable of functioning as an ordinary swab cup on a coiled tubing or drill pipe string, that is also capable of passing a restriction in a well pipe without becoming contorted or damaged. In one embodiment, the seal assembly is one of two or more of these in a washing tool.

Summary of the invention

The invention is stated in the enclosed, independent claims. Preferred embodiments are stated in the subordinate claims.

Brief Figure description

The invention is illustrated in the enclosed Figure illustrations.

Fig. 1 illustrates a coiled tubing- or drill pipe string- (0) born seal assembly (10) moving towards a restriction (1) to be passed in a tubing, casing pipe, or production pipe (2). The other end (12.2) of the seal element (12) of the seal assembly (10) is approaching the restriction.

Fig. 2 illustrates the seal assembly (10) with its other end (12.2) of the seal element (12) in its incipient deformation when it enters through the restriction (1). At this point, a stop flange (11.1) on the tool mandrel (11) is pushing the second end (12.2), and the slide ring (14) along with it into the restriction (1). The bi-conical seal element’s (12) largest diameter (15) is squeezed radially.

Fig. 3 illustrates the seal assembly’s (10) seal element (12) on the inside of and compressed by the restriction (1), and moving through the restriction. At this point, it is now the seal element’s (12) second end (12.2) that is pushing its slide ring (14) away from the stop flange (11.1) along the mandrel (11). Here, the roles of the seal element and the slide ring have been switched: the seal element is pushing the slide ring away from the flange shoulder. The seal element (12) is as such capable of running undamaged and significantly reduced in its outer diameter, through a restriction. An ordinary swab cup would in this scenario become contorted and damaged.

Fig. 4 illustrates the seal element (12) moving out of the restriction (1). The central part of the seal element (12) with the largest diameter (15) is restored in shape, and consequently, through further movement, is sealing the seal element (12) against the casing pipe or the production pipe in a conventional manner. The first end (12.1) of the seal element (12) is in the process of passing the restriction.

Fig. 5 shows the seal assembly (10, 10U) with the upper seal element (12, 12U) as a part of a washing tool (20), where the lower seal assembly (10, 10L) with the lower seal element (12, 12L) already has passed the restriction (which is less problematic), and where the upper seal assembly (10, 10U) is moving in a direction through the restriction (1).

Fig. 6 illustrates the washing tool (20) within a perforated section of the casing pipe or the production pipe. A ball (23-k) has been circulated into the ball seat (24), washing fluid is circulated from coiled tubing or the drill pipe string (0) and out between the assemblies (which are spanned out tighter based on the pressure gradient) and the washing fluid washes out the casing pipe annulus, and circulate out debris. This may occur both in a downwards and upwards trajectory.

Cementation may occur through push and pull, i.e. on its way upwardly. Description of embodiments of the invention

The invention provides a seal assembly (10) to prevent flow of fluid in at least one direction in a tool annulus between the seal assembly (10) and a casing pipe (2).

The seal assembly (10) comprises:

- a tool mandrel (11) with a through bore (13).

- a double conical, elastic seal element (12) that is arranged around the tool mandrel

(11), which has an extension in the longitudinal direction of the tool mandrel (11) from the first end (12.1) to a second, axially moveable end (12.2). The seal element’s

(12) first end (12.1) is fixed in a ring bracket (18) to the tool mandrel (11). The second, axially moveable end (12.2) of the seal element is arranged to slide along the tool mandrel (11), between a first stop flange (11.1) and a second position or stop flange (11.2) on the tool mandrel (11). The double conical seal element (12) has a greatest outer diameter (15) between the first (12.1) and the second end (12.2), which forms a seal annular cavity (16) between the seal element and the tool mandrel.

The seal element (12) is compactable in towards the seal annular cavity (16) and the mandrel (11) through the other end (12.2) sliding away from the first end (12.1) along the tool mandrel (11), towards the second position (11.2) when the seal element (12) is pushed into a restriction (1) in the casing pipe (2).

In an embodiment, the seal assembly (10) comprises a tool mandrel (11) and a double conical seal element (12). The seal element (12) is positioned around the tool mandrel (11) and is fixed to the tool mandrel (11) with a ring bracket (18) in a first end (12.1) of the seal element (12). The seal element’s second end (12.2) has a slide ring (14) mounted on it, which is slidable between a first stop flange (11.1) and a second position or stop flange (11.2) on the tool mandrel (11). It is worth noting that the seal assembly also can function as designed without the second stop flange (11.2). The bi-conical seal element’s (12) second end (12.2) only extends to a greatest length to the position (11.2) when the seal element (12) is squeezed flatly against the mandrel (11).

In an embodiment, the tool mandrel (11) is arranged to be mounted inside a hollow well pipe string as coiled tubing or drill pipe string, and arranged to be guided down into the casing pipe (2). A typical utilization of the seal assembly is in a coiled tubing- or drill pipe string-born washing tool as shown in Fig. 5 and Fig. 6, however, they can also be mounted individually on a well pipe string. Between the tool mandrel (11) and the seal element (12) is a seal annular cavity (16). The seal element (12) is formed by elastic spring material. In the slide ring (14) or in the seal element (12) near the slide ring (14), there are one or more pressure release channels (17). These pressure release channels (17) put the seal annular cavity (16) in fluid communication with a casing pipe annulus to the right-hand side of the largest diameter (15), as shown in Fig. 1-3, or between the seal elements (12U, 12L) in Fig. 6. With the pressure release channels, the seal element (12) will be experienced as an ordinary swab cup, and force the largest diameter (15) out towards the inner wall of the casing pipe when the seal element is pressurized.

The slide ring (14) may comprise an outer (14.1) and an inner (14.2) slide ring bracket. The slide ring brackets (14.1, 14.2) squeeze around the other end (12.2) of the seal element (12) and as such hold the seal element’s second end (12.2) to the slide ring (14), and centers and controls this through restrictions. Bolts and screws (14.3) between the slide ring brackets (14.1, 14.2) and through the second end (12.2) of the seal element (12) pull the slide ring brackets towards each other, so that they fix the second end (12.2) of the seal element (12) as shown in Figures 1-4.

Figures 1-4 show in sequence how the seal assembly (10) and the seal element (12) behave when it is forced through a restriction (1) in a casing pipe 2. In Fig. 1, the seal element (10) of the seal assembly is approaching the restriction (1). The seal element’s largest diameter (15) is rests against the casing pipe (2), and seals up against the inner wall of the casing pipe. Figure 1 shows the second end approaching the restriction. The Figure shows the casing pipe or tubing, etc. (2) and restriction (1) in casing pipe. The Figure shows inner and outer slide ring bracket (14.1 and 14.2). Figure 1 shows a bypass channel (22), bypass ports (23), main bore (13), and radial port (21). Figure 1 shows tool mandrel (11), ring bracket (18), bi- conical seal (12), seal assembly (10), and the largest diameter (15). Figure 1 shows the first end (12-1) and the second end (12-2). The figure shows the second position or stop flange (stop flange (option)) (11-2).

In Fig. 2, the second end (12.2) of the seal element (12) hits the restriction (1), the first stop flange (11.1) pushes the slide ring (14) along with it, and the portion of the seal element (12) between its second end (12.2) and its largest diameter (15) is collapsed radially by the restriction (1), and is thus deformed into the seal annular cavity (16). The second end of the seal element (12) is pulled towards a left-hand side in the figure, but is prevented since the slide ring (14) stops in the first stop flange (11.1). When the slide ring (14) stops in the first stop flange (11.1), it prevents the seal element (12) from becoming contorted or damaged. The slide ring also secures a centering so that the restriction (1) can pass centrally, in the case the restriction is circular or cylindrical. This also contributes to the seal element (12) not being subject to strain in only one sector, and it prevents tearing of the seal material from the largest diameter (15). The Figure 2 shows the second end entering the restriction. The figure shows casing pipe (2) and restriction in casing pipe (1). The figure shows main bore (13), radial port (21), bypass channel (22), bypass ports (23). Figure 2 shows the first end (12.1) and the second end (12.2). The Figure shows second position or stop flange (stop flange (option)) (11-2). The Figure shows inner and outer slide ring bracket (14.1 and 14.2). The Figure shows a pressure release channel (17). The Figure shows that the diameter (15) of the bi-conical seal (12) is squeezed together. The Figure 2 shows the tool mandrel (11) and ring bracket (18). The Figure 2 shows the seal’s radial collapse, and the seal slide ring pushed by the flange edge.

In Fig.3, what was formerly called the largest diameter (15) has passed into the restriction (1). This temporary restriction of the flexible seal element’s (12) largest diameter (15) is allowed through the slide ring being allowed to slide towards the second position or the stop flange (11-2). Here, the roles have been switched between the seal element (12) and the slide ring (14); now, it is the seal element (12) that is pushing the slide ring (14) ahead of itself through the restriction (1). Figure 3 shows the second end (12.2) inside the restriction.

The Figure shows a casing pipe (2) and restriction (2) in the casing pipe. The Figure shows main bore (13), radial port (21), bypass channel (22), bypass ports (23).

Figure 3 shows the first end (12-1) and the second end (12-2). The Figure shows the second position or stop flange (optional) (11-2). The Figure shows inner and outer slide ring bracket (14-1 and 14-2). Figure 3 shows the tool mandrel (11) and ring bracket (18).

In Fig. 4, the largest diameter (15) of the seal element (12) has passed the restriction (1) and is again expanding, thus the seal element’s (12) second end will pull the slide ring (14) back in a direction towards the first stop flange (11-1). The seal element (12) will revert to its original form, and will seal up against the inner wall of the casing pipe (2). Figure 4 shows the second end almost completely passed through the restriction in the casing pipe (1). The Figure shows a casing pipe (2) and a restriction in a casing pipe (1). The Figure shows a radial port (21), bypass port (23), and bypass channel (22). Figure 3 shows the tool mandrel (11), the first end (12-1) and the second end (12-2). The Figure shows the second position or stop flange (stop flange (option)) (11-2). The Figure shows inner and outer slide ring bracket (14-1 and 14-2). Figure 3 shows through screws (14.3) or a pressure release channel (not shown) (17). the Figure shows largest diameter (15) and bi-conical seal re expanding (12).

Figs. 5 and 6 show seal assemblies (10) utilized as a part of a casing pipe annulus washing tool (20). Two oppositely directedseal assemblies (10U, 10L) are placed each on its side of a radial port (21). The washing tool (20) is guided into a well by means of a coiled tubing or drill pipe string. Fluid pumped down into the main bore (13), and communicating with and being able to flow out of the radial port (21), would, by the seal assemblies (10U, 10L), be prevented from continuing to flow along the mandrel (11) with the washing tool (20). The washing tool also comprises one or more bypass channels (22) placing the tool annulus above the washing tool in fluid communication with the tool annulus below the washing tool (20). The bypass channels (22) prevent the washing tool (20) from forcing along or displacing fluid in a tool annulus, i.e. preventing it from acting as a seal piston, and thus prevent movement of the coiled tubing or drill pipe string, which could otherwise also cause damage to the seal assembly (12).

Figure 5 shows the upper seal passing through a restriction. The Figure shows a coiled tubing or drill pipe (0). Figure 5 shows a washing tool (20), tool mandrel (11), radial port (21), casing pipe (2), restriction in casing pipe (1). The Figure shows upper seal assembly (10U), a seal assembly within the restriction (12U), and lower seal assembly (10L) which have easily passed the restriction.

Figure 6 shows washing tool with circulating fluid in a casing pipe (2) -annulus. The Figure shows upper seal assembly (10U), upper seal element (12U), lower seal assembly (10L), and lower seal element (12L). Figure 6 shows a radial port (21), a ball (23-k), and a ball seat (24). The Figure shows perforations and washing fluid cleaning/rinsing a casing pipe annulus. The Figure shows casing pipe or pipes in general (2), washing tool (20), and the material to be washed out of the casing pipe annulus or pipe annulus.

With two or more pairs of these oppositely arranged seal assemblies (10U, 10L), one may pressurize the main bore (13) and thus pressurize the tool annulus in the area between the first (10U) and the second (10L) seal assembly. The washing tool (20) may thus be utilized to pressurize one or more apertures in the casing pipe, for example a perforated section or a cut in a severed casing for pressure testing or casing pipe annulus washing or injection of fluid into the casing pipe annulus or cementation after washing. In the event of cementation, one may circulate inn cement via the washing tool to the perforated casing pipe annulus, and the cement may rise in the casing pipe annulus above the upper seal assembly (10U), and proceed to run down via the bypass channel (22) to a position below the lowermost seal assembly (10L) while the washing tool is slowly pulled upwardly, and as such, one may proceed with “push & pull” cementation of both the casing pipe annulus and the casing pipe simultaneously, in reference to the patent of Sverre Bakken, EP3036395.

In the following, an example of a well operation utilizing the annulus washing tool (20) will be described. The washing tool (20) is mounted into a pipe string on the surface above the well. A pipe string can be a coiled tubing or a drill pipe string. The washing tool (20) is guided down into the well by feeding the pipe string down into the well. When the washing tool (20) is approaching the depth of a restriction (1) in the well’s casing pipe (2) or production pipe, the operator will lower the feeding velocity in order to pass the restriction (1) with the seal assemblies (10) in a gentle fashion. After the restriction or restrictions (1) situated in the well have been passed by the washing tool (20), and before the depth of the washing location has been reached, the integrity of the seal assemblies (10) can be tested. A ball (23-k) is dropped in the pipe string (it can be in free fall in the fluid in the pipe string, or be circulated in) and lands in a ball seat (24), so that the main bore (13) below the washing tool’s (20) radial port is closed shut. The fluid in the main bore (13) is subsequently pressurized, while the washing tool (20) is positioned in a sealed casing pipe (2), a so-called “blank casing”, or in a production pipe. If pressure builds up, and the pressure is maintained, it means that the seal assemblies (10U, 10L) are intact. The washing tool (20) may subsequently be lowered down to the depth where perforations and cuts are, and where washing is to be carried out on the outside of the casing pipe (2) or the production pipe (2) wherein the washing tool (20) is situated. The washing task is carried out by pumping a suitable liquid down the main bore, and while the washing tool (20) is optionallyally moved upwardly or downwardly in the range to be washed. Standard procedure is to commence washing from the top and moving down. The washing can also be succeeded by a cementation task (preferably carried out from the bottom and moving upwardly) or other operations before the washing tool (20) is pulled out of the well. In order to receive an indication whether the washing was successful, i.e. whether the seal assemblies remain sealed, another test can be carried out in a blank casing or production pipe, wherein the seal assemblies (10) are pressure tested before proceeding to the next step in the operational sequence. Pressure is thus set between the seal assemblies (10) with the washing tool (20) in a section of the casing pipe/production pipe that is not perforated or cut in a corresponding fashion as before the washing. The ball (23-k) with the ball seat (24) can be sheared out upon pressure before extracting the washing tool, in order to allow circulation in the pipe string during the extraction. Otherwise, one may have to extract the string while wet, which can prove to be bothersome and messy.