Downhole tubular assembly of a well tubular structure

A downhole tubular assembly configured to be mounted as part of a well tubular structure in a borehole of a well having a top, has a well metal tubing configured to be mounted as part of the well tubular structure. A tubular metal receptacle has an inner receptacle diameter larger than the outer diameter of the well metal tubing, and a second part extending from the first part towards the well metal tubing. The tubing length is larger than the receptacle length, and the a wall of the well metal tubing extends inside the tubular metal receptacle along the entire length of the tubular metal receptacle, and the second part of the tubular metal receptacle is fastened to the outer face of the well metal tubing, thereby closing the tubular metal receptacle in one end and defining an annular space between the tubular metal receptacle and the well metal tubing.

This application is the U.S. national phase of International Application No. PCT/EP2016/059601 filed 29 Apr. 2016, which designated the U.S. and claims priority to EP Patent Application No. 15165785.5 filed 29 Apr. 2015, the entire contents of each of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a downhole tubular assembly configured to be mounted as part of a well tubular structure in a borehole of a well having a top. Furthermore, the invention relates to a well tubular structure for being arranged in a borehole in a well and to a downhole system configured to be arranged in a borehole of a well. Finally, the invention relates to a structure replacement method for replacing at least part of the well tubular structure of a downhole system.

BACKGROUND ART

Oil and gas wells are completed in many different ways and have a variety of different designs. Some wells have cemented inner casings and some wells have uncemented inner casings. Cemented casings are completed after cementing the intermediate casing A and the lower part of the well is drilled so that the inner casing B can be submerged into the well, as shown inFIG. 1A. The cement is then led down the inner casing and out into the annulus C. In the event that, after the borehole has been drilled, tests show that the hydrostatic pressure in the annulus is too high for the cement to rise sufficiently in the annulus, the upper part of the inner casing is removed and replaced by a drill pipe, as shown inFIG. 1B. When replacing the upper part of the inner casing with a drill pipe, the annular space D between the intermediate casing and the inner casing is increased, thereby decreasing the hydrostatic pressure, which allows for the cement to be pressured up to the predetermined level shown inFIG. 1B.

In order to be able to replace the upper inner casing with a drill pipe, the inner casing has a receptacle R into which sealing elements of the upper inner casing can be fit to create a good sealed connection after the drill pipe has been retracted. However, these sealed connections tend to deteriorate over time even though they have never been used, and thus, such wells may leak over time.

SUMMARY OF THE INVENTION

It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved well tubular structure decreasing the risk of leaks occurring without limiting the possibility of increasing the annular space between the intermediate casing and the inner casing.

The above objects, together with numerous other objects, advantages and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole tubular assembly configured to be mounted as part of a well tubular structure in a borehole of a well having a top, the downhole tubular assembly comprising:a well metal tubing configured to be mounted as part of the well tubular structure, the well metal tubing having a longitudinal extension, a tubing length along the longitudinal extension, an inner diameter and an outer diameter defining a wall, an inner face and an outer face, anda tubular metal receptacle having an inner receptacle face and an outer receptacle face, a receptacle length and a first part closest to the top of the well, and having an inner receptacle diameter larger than the outer diameter of the well metal tubing, and having a second part extending from the first part towards the well metal tubing,
wherein the tubing length is larger than the receptacle length, and the wall of the well metal tubing extends inside the tubular metal receptacle along the entire length of the tubular metal receptacle, and the second part of the tubular metal receptacle is fastened to the outer face of the well metal tubing, thereby closing the tubular metal receptacle in one end and defining an annular space between the tubular metal receptacle and the well metal tubing.

The second part may incline from the first part towards the well metal tubing.

Also, the tubular metal receptacle may surround the well metal tubing.

Moreover, the annular space may be at least filled with a fluid for preventing deterioration of the inner receptacle face of the tubular metal receptacle.

The fluid may be grease or silicone.

Furthermore, the fluid may be an inert gas or a noble gas.

In addition, the inner receptacle face of the tubular metal receptacle may be at least partly polished.

Also, the inner receptacle face of the tubular metal receptacle may be at least partly provided with a thread.

Moreover, the second part of the tubular metal receptacle may be fastened by welding or a threaded connection or by crimping to the outer face of the well metal tubing.

Furthermore, the tubular metal receptacle may comprise a sealing element for sealing off the annular space.

Further, the sealing element may be a closure closing the annular space.

Moreover, the inner face of the well metal tubing may have a cutting indication, such as a circumferential recess or a circumferential projection configured to indicate where the well metal tubing is to be cut.

The well metal tubing may be cut e.g. at a predetermined distance from the cutting indication.

Also, the cutting indication may be arranged opposite the tubular metal receptacle.

Moreover, the sealing element may comprise an elastomeric material, a metal, a polymer, rubber or any combination thereof.

In addition, the tubular assembly may comprise a circumferential recess having an inner recess diameter larger than the inner diameter of the well metal tubing, the recess being configured to receive a projecting element of a tool string and being arranged at a predetermined distance from the second part of the tubular metal receptacle.

Moreover, an identification tag may be arranged at the tubular metal receptacle for identifying the position of the tubular metal receptacle, especially the second part of the tubular metal receptacle.

The downhole tubular assembly described above may further comprise an annular barrier comprising:a tubular metal part for mounting as part of a well tubular structure,an expandable metal sleeve surrounding the tubular metal part and having an inner face facing the tubular metal part and an outer face, each end of the expandable metal sleeve being connected with the tubular metal part, andan annular space between the inner face of the expandable metal sleeve and the tubular metal part.

The present invention furthermore relates to a well tubular structure made of metal for being arranged in a borehole in a well, comprising a plurality of tubular sections, at least one of the tubular sections being the downhole tubular assembly as described above.

Moreover, at least one of the tubular sections may comprise an annular barrier comprising:a tubular metal part for mounting as part of the well tubular structure,an expandable metal sleeve surrounding the tubular metal part and having an inner face facing the tubular metal part and an outer face, each end of the expandable metal sleeve being connected with the tubular metal part, andan annular space between the inner face of the expandable metal sleeve and the tubular metal part.

Furthermore, at least one of the tubular sections may comprise a circumferential recess.

The circumferential recess may be arranged at a predetermined distance from the second part of the tubular metal receptacle.

The present invention furthermore relates to a downhole system configured to be arranged in a borehole of a well, comprising:a well tubular structure as described above,an intermediate tubular metal structure, the well tubular structure being at least partly arranged in the intermediate tubular metal structure, andat least one main annular barrier arranged between the well tubular structure and the intermediate tubular metal structure, defining an annulus above the main annular barrier.

Also, the downhole system may comprise a tool string comprising a tubing cutting tool.

Furthermore, the tool string may further comprise a docking unit having a projecting element being configured to engage with the circumferential recess.

The tubing cutting tool and the projecting element may have a mutual tool distance between them, the tool distance and the predetermined distance between the circumferential recess and the second part of the tubular metal receptacle being substantially equal.

Furthermore, the tool string may comprise a logging unit configured to detect an identification tag.

Finally, the present invention relates to a structure replacement method for replacing at least part of the well tubular structure as described above of a downhole system as described above, comprising the steps of:submerging a tool string having the tubing cutting tool into the well tubular structure,positioning the tubing cutting tool opposite the tubular metal receptacle,cutting the well metal tubing above the position where the second part is fastened to the well metal tubing,retracting the tool string from the well tubular structure,retracting the well tubular structure above the cut to expose the tubular metal receptacle,inserting a new and/or second well tubular structure in the borehole,inserting an end of the new and/or second well tubular structure in the tubular metal receptacle, andlanding the new and/or second well tubular structure in the exposed tubular metal receptacle to sealingly connect the new and/or second well tubular structure to the tubular metal receptacle.

Moreover, the step of positioning the tubing cutting tool may be performed by engaging a projecting element in the circumferential recess, the tubing cutting tool and the projecting element having a mutual tool distance between them, the tool distance and the predetermined distance between the circumferential recess and the second part of the tubular metal receptacle being substantially equal.

Furthermore, the step of positioning the tubing cutting tool may be performed by a logging tool identifying an identification tag arranged at the tubular metal receptacle.

Moreover, sealing elements may be arranged on an outside face of the new and/or second well tubular structure, which outside face is arranged opposite the inner receptacle face of the tubular metal receptacle to provide a sealing between the tubular metal receptacle and the new and/or second well tubular structure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2shows a downhole tubular assembly1configured to be mounted as part of a well tubular structure2in a borehole3of a well4having a top5, as shown inFIG. 3. The downhole tubular assembly1comprises a well metal tubing6configured to be mounted as part of the well tubular structure2and a tubular metal receptacle9arranged on an outside of the well metal tubing and circumferenting the well metal tubing so that the well metal tubing extends inside the tubular metal receptacle9along an entire length of the tubular metal receptacle.

The downhole tubular assembly1ofFIG. 2has a tubing length Ltalong a longitudinal extension of the well metal tubing6, an inner face7and an outer face8, and an inner diameter IDtand an outer diameter ODtdefining a wall28therebetween. The tubular metal receptacle9has an inner receptacle face10and an outer receptacle face11, a receptacle length Lrwhich is smaller than the tubing length Lt, and a first part12closest to the top of the well. The tubular metal receptacle9has an inner receptacle diameter IDrlarger than the outer diameter of the well tubing part, and a second part14of the tubular metal receptacle9extends from the first part12towards the well metal tubing6in an inclining manner. Thus, the wall28of the well metal tubing6extends inside the tubular metal receptacle9along the entire length of the tubular metal receptacle, and the second part14of the tubular metal receptacle9is fastened to the outer face8of the well metal tubing6, thereby closing the tubular metal receptacle in one end furthest away from the top of the well and defining an annular space15between the inner receptacle face10of the tubular metal receptacle9and the outer face8of the well metal tubing6.

The well metal tubing6is thus intact and uninterrupted opposite the metal receptacle9, and when the well metal tubing is mounted as part of the well tubular structure2, there is no sealing risk as there is no interrupted well tubing parts opposite the metal receptacle9as in the known solutions. In the event that calculations and tests show that the upper section of the well tubular structure above the metal receptacle9needs to be replaced with a drill pipe, a tool string24comprising a tubing cutting tool25is submerged into the well tubular structure2so that a projectable cutting part29is arranged opposite the metal receptacle9and cuts a first section34of the well metal tubing6from a second section36of the well metal tubing6, as shown inFIG. 4. By having the metal receptacle9on the outside of the well metal tubing6, the well tubular structure2is prepared to replace an upper part42with a drill pipe by a simple cut if needed. However, if the tests and calculations show that there is no need for inserting a drill pipe to perform the cement job, the well metal tubing6and the well tubular structure2are kept intact, and the risk of leaks in the receptacle connections is avoided. The casing collars necessary for mounting the well tubular structure2from the tubular sections22is still unavoidable, but these very firmly sealed connections do not have the same risk of causing leaks.

As shown inFIG. 4, the tool string24also comprises an anchoring section45for providing a backing during the machining operation when the tubing cutting tool25cuts and separates the first section34of the well metal tubing6from a second section36of the well metal tubing6, thus separating the upper part42of the well tubular structure from a lower part46.

The inner receptacle face10of the tubular metal receptacle9is polished at least along the first part12. The annular space15ofFIG. 2may be at least partly filled with a fluid16for preventing deterioration of the inner receptacle face10of the tubular metal receptacle9to prevent the inner receptacle face from deteriorating significantly. In this way, the receptacle9is ready for use at any time during the life time of the well. The fluid16may be grease or silicone filling up the annular space15.

InFIG. 2, the tubular metal receptacle9is open at its top, and since the tubular metal receptacle is often used within a few months from insertion in the borehole, the polished inner receptacle face is normally not deteriorated significantly. However, when the annular space15is filled with grease or silicone, the polished inner receptacle face10is still maintained in a non-corroded condition and is thus ready for use years after completion of the well. The annular space15may also be fully closed in that the second part14of the tubular metal receptacle9is fastened by welding48, as shown inFIG. 5, by a threaded connection or by crimping to the outer face8of the well metal tubing6. The annular space15may also by be sealed off by a sealing element17, as shown inFIG. 6. The annular space15may, even when fully closed, also be filled with a fluid, such as the grease or silicone mentioned above or an inert gas or a noble gas. The sealing element17comprises an elastomeric material, a metal, a polymer, a rubber or any combination thereof.

InFIG. 5, the tubular assembly1further comprises a circumferential recess18having an inner recess diameter IDrelarger than the inner diameter of the well metal tubing6. The recess is configured to receive a projecting element19of a docking unit26of the downhole tool string24as shown inFIG. 4. The recess18ofFIG. 5is thus arranged at a predetermined distance Dtfrom the second part14of the tubular metal receptacle9so that when cutting the well metal tubing6, the cut is positioned correctly.

Another way of identifying the position of the tubular metal receptacle9, especially the second part14of the tubular metal receptacle, and thus identifying where to cut, is to identify an identification tag20arranged in the tubular metal receptacle9, as shown inFIG. 6. The downhole tool string24may thus comprise a logging unit53for identifying the identification tag20, as shown inFIG. 6. The logging unit may also be a magnetic profiling or an ultrasonic tool capable of identifying the tubular metal receptacle.

As shown inFIG. 7, the downhole tubular assembly1further comprises an annular barrier30comprising a tubular metal part37being the well metal tubing6for mounting as part of the well tubular structure2. The annular barrier30comprises an expandable metal sleeve38surrounding the tubular metal part and having an inner face39facing the tubular metal part37and an outer face31facing the borehole3. Each end32of the expandable metal sleeve38is connected with the tubular metal part37, defining an annular space35between the inner face of the expandable metal sleeve and the tubular metal part. The tubular metal part37comprises an expansion opening27opposite the annular space35so as to allow pressurised fluid inside the tubular metal part37to enter the annular space and expand the expandable metal sleeve38.

As shown inFIG. 7, the well tubular structure2arranged in the borehole3in the well4comprises a plurality of tubular sections22, where at least one of the tubular sections is the downhole tubular assembly1comprising the metal receptacle9. The well tubular structure2comprises two other annular barriers30isolating a production zone101, and one of the tubular sections22opposite the production zone101comprises an inflow control device49for allowing well fluid to flow into the well tubular structure2. A tubular section22of the well tubular structure2above the metal receptacle9comprises a circumferential recess18which is arranged at a predetermined distance Dt(shown inFIG. 5) from the receptacle9so that the tubing cutting tool is positioned in such a way that it cuts correctly just above the second part14of the receptacle9. The well tubular structure2further comprises tubular sections22comprising a metal receptacle9, meaning that metal receptacles9are arranged further down the well. In this way, lower parts of the well tubular structure2can be replaced with new and/or second tubular sections22or tubular sections22comprising e.g. an annular barrier or an inflow control device. By having metal receptacles9arranged further down the well, parts of the well tubular structure2arranged above such receptacles can be pulled out of the well and replaced with a new and/or second tubular structure, and thus, corroded parts of the well tubular structure can be replaced without having to pull out the entire well tubular structure2.

As shown inFIG. 7, a new improved downhole system100configured to be arranged in a borehole of a well has been provided, comprising the well tubular structure2and an intermediate tubular metal structure23, where the well tubular structure2is arranged inside the intermediate tubular metal structure23and lowered further down the well. Between the well tubular structure2and the intermediate tubular metal structure23a main annular barrier51is arranged, defining an annulus52above the main annular barrier. The main annular barrier51is thus an annular barrier as described above.

The downhole system100ofFIG. 7has another recess18arranged at a predetermined distance from a completion component, e.g. the inflow control device49, so that the projecting elements of the docking unit of the downhole tool string24shown inFIG. 4can be projected and in a biasing manner abut the inner face of the well tubular structure2. As the tool string24approaches the circumferential recess, the projecting elements project further into the recess and thus dock into the recess, thereby positioning the tool in the correct distance from the component, and the tool can thus operate e.g. a sliding sleeve, the inflow control device, etc.

InFIG. 8, the well tubular structure2has a second annular barrier arranged below the main annular barrier51. The well is thus cemented all the way up to the level of the second annular barrier, and subsequently, the second annular barrier is expanded. Thus, the main annular barrier provides a primary barrier of the A annulus and the second annular barrier provides a secondary barrier of the B annulus.

InFIG. 9, the downhole tubular assembly1has a metal receptacle9and a cutting indication43in the well metal tubing6. The cutting indication43is arranged opposite the annular space15between the tubular metal receptacle9and the well metal tubing6and indicates where the well metal tubing6is to be cut in order to expose the inner face10of the tubular metal receptacle.

The inner face of the tubular metal receptacle is exposed so that a second well metal tubing abutting the inner face can be arranged and sealed against the inner face of the tubular metal receptacle9. A second well metal tubing may be used to replace a worn out part of the previous well metal tubing or the second well metal tubing may have a smaller inner diameter which promotes the production of hydrocarbons. Thus, the second well metal tubing may have an outer diameter which is larger than the outer diameter ODtof the cut well metal tubing6, so that the outer face of the second well metal tubing contact the inner face10of the tubular metal receptacle. The cutting indication may also be arranged at a distance to the area which is most suitable to cut in. By having a cutting indication, the projectable cutting part29(shown inFIG. 6) of the tubing cutting tool may slide along the inner face7of the well metal tubing6, and once engaging the cutting indication, the tubing cutting tool stops moving along the longitudinal extension and the cutting operation is initiated. The cutting indication may be a circumferential recess or a circumferential projection.

By well fluid is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By gas is meant any kind of gas composition present in a well, completion, or open hole, and by oil is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc. Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively.

By a casing or a well tubular structure is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production. The well tubular structure is made of metal and mounted from tubular sections.

In the event that the tool is not submergible all the way into the casing, a downhole tractor can be used to push the tool all the way into position in the well. The downhole tractor may have projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.

Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.