Downhole Tubular Section Mill

Abstract

A casing section mill has a main body with cut-outs to accommodate casing section mill blades mounted thereon, and stabilizer inserts mounted in the cut-outs below the blades. The stabilizer inserts yield an outer diameter substantially the same as the drift inner diameter of the casing being milled, thereby providing positive centralization and stabilization of the blades. The casing section mill may be rotated by a downhole positioned positive displacement motor in the drillstring, by drillstring rotation from the surface, or a combination of downhole positive displacement motor and drillstring rotation.

Description

BACKGROUND

Field of the Invention

This invention relates to apparatus for downhole cutting of tubulars in a wellbore.

Various apparatus have been developed for cutting of tubulars, downhole in a wellbore. The Applicant herein holds various patents and patent applications directed to such apparatus.

SUMMARY OF THE INVENTION

The apparatus comprises a main body designed to accommodate the linkage arms and cutter bases of Applicant's Well Bore Casing Mill, as disclosed in Applicant's U.S. Pat. No. 9,695,660, along with the internal piston operating system; however, the linkage arms and cutter bases of that apparatus may be replaced with more conventional section mill (“CSM”) blades. As disclosed in that patent, the main body has a pair of longitudinal cut-outs on either side, in which the linkage arms and cutter bases operate.

In the tubular section mill embodying the principles of the present invention, the CSM blades are rotatably mounted in the cut-outs in the main body, generally in an upper part of the main body, and rotatable from a first, substantially retracted position, to a second, substantially extended position, by the internal operating piston in response to fluid flow. Notably, a number of different types of CSM blades, configured to cut windows in the tubulars, mill sections of the tubulars, etc. may be installed as desired. Depending upon the blade configuration, cutting in either or both of a downhole and uphole direction may be done.

In the lower part of the main body, in the cut-outs in which linkage arms and cutter bases would retract (in the apparatus disclosed in U.S. Pat. No. 9,695,660), are mounted non-expanding stabilizer inserts. The overall tool diameter yielded by the stabilizer inserts is sized to substantially match the drift diameter of the tubular string, namely the casing string, internal diameter (ID) within which the tool is being run; that is, closely matched to the drift diameter of the tubular in which the stabilizer insert is positioned and (usually) that is being milled.

Downhole rotation of the apparatus can be had by surface rotation of the entire drillstring, or in some instances preferably by a downhole device, namely a positive displacement motor (“PDM”). A combination of surface rotation and downhole rotation via PDM can be used. In some settings a downhole turbine could be used.

An exemplary bottom hole assembly (“BHA”) incorporating the present apparatus would include (starting at the downhole end of the BHA) a CSM dressed with blades to suit the particular job (e.g. casing cutting, milling, etc.) and with stabilizer inserts yielding an outer diameter closely matching the drift ID of the casing being milled; a jetted top sub; a float sub with a ported float; a PDM; and drill collars as appropriate, connecting to the work string on which the BHA is lowered into the wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematical view of the apparatus embodying the principles of the present invention, along with other elements of a typical bottom hole assembly.

FIG. 2 is a perspective view of the main body of the apparatus embodying the principles of the present invention, showing more detail of the stabilizer inserts mounted in the main body, namely in the lower section of the cut-outs.

FIG. 3 is another perspective view of the apparatus, showing the CSM blades mounted in the main body and in an outwardly extended position, in addition to the stabilizer inserts.

FIGS. 4a-4c are various side views of the apparatus, with the blades in a retracted position. FIGS. 4a and 4c are views rotated 90 degrees from one another. FIG. 4b is a side view in partial cross section of the apparatus, along section line A-A in FIG. 4c, showing the blades in a retracted position and elements of the internal operating mechanism, namely the piston. Note that the stabilizer inserts are not mounted in the main body in these views.

FIGS. 5a-5c are various side views of the apparatus, with the blades in an extended position. FIGS. 5a and 5c are views rotated 90 degrees from one another. FIG. 5b is a side view in partial cross section of the apparatus, along section line A-A in FIG. 5c, showing the blades in an extended position and elements of the internal operating mechanism, namely the piston. Note that the stabilizer inserts are not mounted in the main body in these views.

FIG. 6 is a view of an exemplary placement of the casing section mill of the present invention in a downhole position in a casing string, showing the tool engaged with the casing and cutting and/or milling a window therein.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT(S)

While various downhole tubular section mills can embody the principles of the present invention, with reference to the drawings some of the presently preferred embodiments can be described.

FIG. 1 is a schematical view of a typical bottom hole assembly (“BHA”) comprising the casing section mill embodying the principles of the present invention. While various assemblies may be employed, depending upon the particular job, by way of example (starting at the downhole end) the BHA comprises a casing section mill (“CSM”) 10 dressed with blades 40 to suit the particular job, and with stabilizer inserts 30 to match tubular inner diameters; a jetted top sub (noted); a float sub, preferably with a ported float (noted); a positive displacement motor or PDM 100; and drill collars as appropriate, connecting to the work string. It is understood that different BHA components may be used depending on the job. Notably, in this exemplary embodiment, PDM 100 is used to generate downhole rotation of the apparatus. It is understood that surface rotation of the entire drillstring, in combination with downhole rotation via PDM 100 (or turbine), is encompassed within the invention.

It is understood that the CSM embodying the principles of the present invention generally comprises the main body and piston operating system disclosed in Applicant's U.S. Pat. No. 9,695,660, and the disclosure of that patent is incorporated herein by reference, to the extent needed to set out the general structure of the instant apparatus.

FIG. 2 is a more detailed perspective view of CSM 10, showing main body 20 of the apparatus without blades 40 installed. Note the uphole/downhole directions indicated. FIG. 2 shows stabilizer inserts 30 mounted in the lower section of the cut-outs 22 within main body 20. Main body 20 has a longitudinal bore 24 in at least an upper section thereof, through which fluid is pumped. Preferably, stabilizer inserts 30 are sized to yield an outer diameter of CSM 10 nearly equal or equal to the drift diameter of the tubular within which stabilizer inserts 30 are rotating, so as to minimize eccentric movement of the entire apparatus within the tubular. In addition, stabilizer inserts 30 are preferably positioned immediately below (or as close as reasonably possible) the blade location, again to assist in centralization of the overall tool. Typically, stabilizer inserts 30 are positioned in and rotating in a casing string which is being cut or milled by blades 40 positioned just uphole from stabilizer inserts 30. The diameter resulting from the stabilizer inserts 30 and the close positioning (in a downhole position) result in a very stable cutting path of blades 40, and very much increased efficiency of cutting.

FIG. 3 is another perspective view, showing main body 20 with stabilizer inserts 30 installed, and additionally with blades 40 installed. In FIG. 3, blades 40 are in a second, open position.

FIGS. 4a-4c are side views of casing section mill 10. FIGS. 4a and 4c are exterior views rotated 90 degrees apart. FIG. 4b is a section view along section line A-A of FIG. 4c. These three views show apparatus with blades 40 installed and showing some detail of operating mechanism 42. In particular, as disclosed in U.S. Pat. No. 9,695,660, operating mechanism 42 comprises a slidable piston 44, which moves in a downhole direction in response to fluid flow in that direction; piston 44 has a bore 43 and preferably a removable jet therein. In these figures, blades 40 are in a first, retracted position.

FIGS. 5a-5c are further side views of casing section mill 10, generally corresponding to the views in FIGS. 4a-4c. FIGS. 5a and 5c are exterior views rotated 90 degrees apart. FIG. 5b is a section view along section line A-A of FIG. 5c. Similar to FIGS. 4a-4c, these three views show apparatus with blades 40 installed and showing some detail of operating mechanism 42. In these FIGS. 5a-5c, blades 40 are in a second, open or extended position. A lower end of piston 44 bears on heel portions 41 of blades 40, rotating them into their second, open or extended position.

Fabrication and Materials

Casing section mill 10 is preferably formed from high strength metals and with fabrication techniques generally known in the relevant art (welding, machining, forging, etc.). Non-metal components are used as appropriate for seals, etc.

Methods of Use of the Apparatus and System

The present apparatus may be considered as part of a system, the apparatus and its methods of use embodying the present invention. The scope of the present invention encompasses not only casing section mill 10 alone, but also a system comprising casing section mill 10, along with various methods of use. As noted above, casing section mill or CSM 10 is beneficially part of a downhole tubular milling system employing PDM 100. FIG. 6 is a view of an exemplary setting of use of casing section mill 100. Casing section mill 100 is positioned at a desired location in the casing 200. As can be seen, the outer diameter of stabilizer inserts 30 closely match the inner diameter, preferably the drift diameter, of casing 200. Blades 40 are extended outwardly to an operating or cutting position, by fluid flow through the drillstring and bore 24 of casing section mill 10 acting on piston 44. As can be seen in FIG. 6, a section of casing has already been cut/milled out, and blades 40 are bearing on the uppermost cut end. Rotation of casing section mill 10, combined with weight imposed on the cutting surface by the bottom hole assembly, results in continued cutting. Use of a PDM to achieve downhole rotation of casing section mill 10 permits achieving a higher rotation speed of casing section mill 10, for example 100-200 RPM. Alternatively, a downhole rotation speed of casing section mill 10 of (for example) 60 RPM may be achieved via PDM 100, in addition to surface rotation of the entire drillstring (for example) 60 RPM, resulting in a final rotation speed of casing section mill 10 of 120 RPM. By achieving part of the overall rotation speed of casing section mill 10 via surface rotation, torque readings may be easily taken at the surface.

It is understood that methods of both cutting and milling tubulars using a system comprising casing section mill 10 are encompassed within the present invention. The method may include the steps of: lowering a bottom hole assembly comprising casing section mill 10 and a PDM to a desired depth in a wellbore, on a drillstring; commencing fluid flow through the drillstring, the PDM, and casing section mill 10, thereby moving blades 40 outwardly into contact with the casing wall or a previously cut surface, in order to continue milling, and resulting in rotation of casing section mill 10; alternatively, if desired, commencing rotation of the drillstring from the surface; monitoring string weight, weight on the tool downhole, and torque at the surface, in order to monitor and optimize the milling function.

Various types of blades 40 may be used, depending on the particular tubular cutting/milling function being performed. By way of example:

• • blades can be used which comprise multiple hardened inserts, for both cutting an initial window in a casing string, and for milling a section of the casing string
  • traditional casing section mill blades can then be substituted if desired for milling longer sections
  • if desired, both blades 40 and stabilizer inserts 30 may be removed from a given main body 20, and that same main body 20 may be “dressed” or equipped with linkage arms, cutter bases and cutters, as disclosed in Applicant's U.S. Pat. No. 9,695,660; this versatility is a significant benefit of the system
  • blades 40 can be configured to enable cutting/milling in both a downhole and an uphole direction, with uphole milling enabled with sufficient downward force applied to piston 44.

CONCLUSION

While the preceding description contains many specificities, it is to be understood that same are presented only to describe some of the presently preferred embodiments of the invention, and not by way of limitation. Changes can be made to various aspects of the invention, without departing from the scope thereof. For example, dimensions can be varied to suit particular applications; the types and configurations of blades can be varied depending upon the types and dimensions of tubulars being cut, and the length of the cuts; any combination of surface and downhole rotation (which may be by PDM or turbine) may be used; sequences of dressing the apparatus with different blades, with/without stabilizer inserts may be used to achieve different jobs.

Therefore, the scope of the invention is to be determined not by the illustrative examples set forth above, but by the appended claims and their legal equivalents.

Claims

1. A casing section mill, comprising: an elongated main body having upper and lower ends and a central bore through an uphole section thereof, with a means for connecting said upper end to a drillstring, said main body further comprising a pair of elongated cutouts extending to a position proximal said lower end;a piston slidably disposed in said central bore, said piston movable in response to fluid flow through said central bore of said main body;a pair of blades rotatably disposed in said main body, said blades comprising heel sections, wherein said piston bears on said heel sections in response to fluid passage through said bore of said main body, moving said blades from a first, retracted position to a second, extended position to engage a casing string for cutting or milling;a plurality of stabilizer inserts removably mounted in a lower or downhole portion of said elongated cutouts, in a downhole direction from said blades, said stabilizer inserts sized to yield an outer diameter across said mounted stabilizer inserts substantially equal to the inner drift diameter of the casing string being cut or milled.

2. The casing section mill of claim 1, wherein said blades comprise elongated cutters having multiple hardened inserts therein.

3. The casing section mill of claim 2, wherein said stabilizer inserts comprise elongated inserts with an upper end positioned proximal said blades when said blades are in their first, retracted position, and a lower end extending substantially to a lower or downhole end of same main body, and wherein said lower end of said stabilizer inserts comprise tapered profiles to aid in movement downhole in a wellbore.

4. An assembly for milling casing in a wellbore, comprising: a drillstring comprising a bottomhole assembly, said bottomhole assembly comprising: a casing section mill, said casing section mill comprising: an elongated main body having upper and lower ends and a central bore therethrough, said main body further comprising a plurality of elongated cutouts extending to a position proximal said lower end;a piston slidably disposed in said central bore, said piston movable in response to fluid flow through said central bore of said main body;a pair of blades rotatably disposed in said main body, said blades comprising heel sections, wherein said piston bears on said heel sections in response to fluid passage through said bore of said main body, moving said blades from a first, retracted position to a second, extended position to engage a casing string for cutting or milling;a plurality of stabilizer inserts removably mounted in a lower or downhole portion of said elongated cutouts, in a downhole direction from said blades, said stabilizer inserts sized to yield an outer diameter across said mounted stabilizer inserts substantially equal to the inner drift diameter of the casing string being cut or milled; anda positive displacement motor disposed in an uphole position from said casing section mill, whereby rotation of said positive displacement motor due to fluid flow results in rotation of said casing section mill.

5. The casing section mill of claim 4, wherein said stabilizer inserts comprise elongated inserts with an upper end positioned proximal said blades when said blades are in their first, retracted position, and a lower end extending substantially to a lower or downhole end of same main body, and wherein said lower end of said stabilizer inserts comprise tapered profiles to aid in movement downhole in a wellbore.

6. A method of milling casing, comprising the steps of: a) providing a casing section mill, comprising: an elongated main body having upper and lower ends and a central bore through an uphole section thereof, with a means for connecting said upper end to a drillstring, said main body further comprising a pair of elongated cutouts extending to a position proximal said lower end;a piston slidably disposed in said central bore, said piston movable in response to fluid flow through said central bore of said main body;a pair of blades rotatably disposed in said main body, said blades comprising heel sections, wherein said piston bears on said heel sections in response to fluid passage through said bore of said main body, moving said blades from a first, retracted position to a second, extended position to engage a casing string for cutting or milling;a plurality of stabilizer inserts removably mounted in a lower or downhole portion of said elongated cutouts, in a downhole direction from said blades, said stabilizer inserts sized to yield an outer diameter across said mounted stabilizer inserts substantially equal to the inner drift diameter of the casing string being cut or milled;b) running said casing section mill downhole into a wellbore, on a drillstring;c) positioning said casing section mill within a section of casing to be milled; andd) commencing fluid flow through said drillstring, said positive displacement motor and said casing section mill, thereby extending said blades and engaging said blades with said casing string and rotating said casing section mill.

7. The method of claim 6, comprising the further step of: e) rotating said drillstring from the surface, resulting in a rotational speed of said casing section mill from the combination of said positive displacement motor and said drillstring rotation.

8. The method of claim 7, comprising the further step of: f) monitoring torque readings on said drillstring.