The present invention relates to a downhole production casing string for insertion in a borehole in a reservoir. Furthermore, the invention relates to a downhole production casing string system for completing a well downhole and to a method of implementing a production casing string according to the invention.
Oil and gas wells may have a variety of completion designs depending on the reservoir conditions. Most of the wells have a metal tubing, also called a casing, which is entered into a drilled borehole, and in some implementations the casing gets stuck, or the packer or annular barriers are not forming a tight zone isolation when set. This sometimes occurs due to the fact that the drilling operation results in a borehole having a plurality of projections which prevent free passage of the casing.
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 casing string which is easier to implement in a borehole, also when the production casing string has annular barriers.
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 production casing string for insertion in a borehole in a reservoir, the downhole production casing string having a first end nearest a top of the borehole and a second end furthest away from the top, the downhole production casing string extending along a longitudinal axis and comprising:
at least one opening which during production allows hydrocarbon-containing fluid from the reservoir into the downhole production casing string,
a plurality of casing parts having end sections and a base section between the end sections, the base section having an outer diameter, and
at least one annular projecting element having an outer face and at least one helical groove arranged in or on the outer face and having an overall outer diameter which is larger than the outer diameter of the base section.
The annular projecting element may be a casing collar connecting the casing parts.
The downhole production casing string as described above may further comprise at least one annular barrier.
Moreover, the annular projecting element may be arranged between two annular barriers.
Also, the annular projecting element may be part of an annular barrier.
The annular barrier may comprise a casing part, an expandable sleeve surrounding the casing part and having an inner sleeve face facing the casing part and an outer sleeve face facing the borehole, each end of the expandable sleeve being connected with the casing part in two connections, and an annular space between the inner sleeve face of the expandable sleeve and the casing part, and wherein the annular projecting element may be arranged on an outer casing face adjacent at least the connection closest to the second end of the production casing string.
The annular barrier may further comprise a casing part, an expandable sleeve surrounding the casing part and having an inner sleeve face facing the casing part and an outer sleeve face facing the borehole, each end of the expandable sleeve being connected with the casing part in two connections, and an annular space between the inner sleeve face of the expandable sleeve and the casing part, and wherein the annular projecting element at least may constitue the one connection arranged closest to the second end of the production casing string.
Moreover, the annular projecting element may be arranged in each end of the expandable sleeve for connecting the sleeve to the casing part.
Additionally, the annular projecting element may constitute a connection part overlapping the ends of the sleeve so that the sleeve is sandwiched between the annular projecting element and the casing part.
Furthermore, the opening may have an angle in relation to a radial direction transverse to the longitudinal axis so that the hydrocarbon-containing fluid is guided into the production casing string in the angle different from 90°.
In this way, when entering the production casing string, the fluid may not be jetted directly into the wall opposite the opening, and therefore wear on the wall may be significantly reduced.
Also, the helical groove may have a cutting edge.
Further, the annular projecting element may comprise several grooves forming a helix about the longitudinal extension.
The annular projecting element described above may taper towards the second end of the production casing string.
The outer diameter of the annular projecting element may be the overall outer diameter of the production casing string.
Also, the opening may be arranged in the groove for letting fluid from the reservoir into the production casing string.
Furthermore, the production casing string may have an inner face along which a sliding sleeve may be slidably arranged for sliding between a closed position, in which the sliding sleeve may block the opening, and an open position, in which the fluid may be allowed to flow through the opening and into the production casing string.
The opening may be arranged closer to the first end of the production casing string than to the second end of the production casing string, or closer to the second end of the production casing string than to the first end of the production casing string.
Moreover, the groove may have an angle in relation to the longitudinal axis, wherein the angle may be 10-80°, preferably 25-75°, more preferably 35-55°.
Also, the groove may taper towards the first and/or second end of the production casing string.
Furthermore, the annular projecting element may have threads for being connected to the casing parts.
The invention also relates to a downhole production casing string system for completing a well downhole, comprising:
a production casing string according to any of the preceding claims, and
a rotation equipment for rotating the production casing string along the helical groove as the production casing string is inserted into the borehole.
Finally, the present invention relates to a method of implementing a production casing string according to the invention in a borehole downhole, comprising the following steps:
connecting casing parts and at least one annular projecting element for forming the production casing string,
entering the production casing string into the borehole as the casing parts are assembled, and
rotating the production casing string along the helical groove as the production casing string enters the borehole.
Said method may further comprise the step of detaching part of a wall of the borehole from the wall by cutting in or hitting against the borehole wall by means of the annular projecting element.
Moreover, the method as described above may comprise the step of allowing fluid to flow from the borehole, in through an opening in the annular projecting element and into the downhole production casing string.
The method may further comprise the step of increasing an inner diameter of the borehole as the edge of the groove hits against the borehole wall.
The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which
All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.
The downhole production casing string 1 comprises an opening 7 through which hydrocarbon-containing fluid is let into the downhole production casing string from the reservoir in order to produce oil or gas. The downhole production casing string is mounted from a plurality of casing parts 8. The casing parts have end sections 9 and a base section 10 between the end sections forming one pipe section. An annular projecting element 11 is arranged between the casing parts 8 connecting two adjacent casing parts. Each annular projecting element 11 has an outer face 12 and at least one helical groove 14a arranged in the outer face. The base section has an outer diameter Do, and each annular projecting element 11 has an overall outer diameter Doo which is larger than the outer diameter of the base section, so that when the production casing string is inserted in the borehole, the annular projecting elements 11 are the elements hitting against the wall of the borehole. The string is rotated as indicated by the arrows, and since each annular projecting element 11 has helical grooves, the annular projecting elements 11 function as a screw easing the implementation of the production casing string in the borehole. When drilling a borehole, the wall has a lot of rock projections which may prevent free passage of known production casing strings. By having annular projecting elements 11 with a helical groove, the production casing string can easily be screwed past these borehole projections, and thus the risk of the production casing string getting stuck in the borehole during insertion is substantially reduced. Furthermore, when inserting the production casing string, the annular projecting elements 11 may hit against the borehole projections and in this way release the tip of the borehole projection from the remaining part, easing the passage of the production casing string further down the borehole. In this way, the annular projecting elements function to even out some of the irregularities of the borehole during the insertion of the downhole production casing string. As the production casing string is inserted and the annular projecting elements hit against the rock projections, the annular projecting elements 11 of the production casing string also protect other completion components in the production casing string by clearing the path.
The downhole production casing string system 100 shown in
In
As shown in
As can be seen in
The annular projecting element 11 has an internal groove 31 in which a sliding sleeve 32 is arranged, as shown in
In
The angled opening may also be part of an insert 51 which is inserted in an opening in the annular projecting element 11 as shown in
As can be seen in
In
In
The annular projecting element 11 and the connection 22 or connection part 22 may also be two separate elements as shown in
As shown in the right side of
By fluid or 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 is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production.
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.
Number | Date | Country | Kind |
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13195030.5 | Nov 2013 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/075892 | 11/28/2014 | WO | 00 |