Lining of well bores with expandable and conventional liners

Abstract

Reducing the diameter of a well bore has many advantages. To achieve this a subsurface well bore is provided comprising one or more expandable sleeve components, preferably expandable liners, each expandable sleeve component being fully overlapped by one or more non expandable sleeve component, preferably conventional liners, such that the interior of the well bore is cased entirely by non expandable sleeve components. In addition the through holes for downhole lines can be provided within the well head rather than the tubing hanger. As the tubing hanger does not need to provide space for through holes and associated mounting couplings, its diameter can be reduced, thus reducing the internal diameter of the well bore by several inches.

Claims

1. A method of drilling a subsurface well bore comprising the steps of drilling a well section, casing said well section with an expandable sleeve component, such that the expandable sleeve component forms an intermediate, temporary support of the well bore, drilling a further well section, and casing said further well section with a non expandable sleeve component which fully overlaps the expandable sleeve component and the further well section.

2. A method as claimed in claim 1, wherein the non expandable sleeve component is conventional liner.

3. A method as claimed in claim 2, wherein the expandable sleeve component is an expandable liner.

4. A method as claimed in claim 2, wherein no casing hanger is placed within a well head.

5. A method as claimed in claim 1, wherein the expandable sleeve component is an expandable liner.

6. A method as claimed in claim 5, wherein a well head is installed together with or after insertion of a surface casing, and wherein all further sleeve components are inserted into the bore hole through said well head.

7. A method as claimed in claim 6, wherein the method further comprises passing downhole lines through the well head and not a tubing hanger.

8. A method as claimed in claim 5, wherein no casing hanger is placed within a well head.

9. A method as claimed in claim 1, wherein no casing hanger is placed within a well head.

10. A method as claimed in claim 9, wherein the method further comprises passing downhole lines through the well head and not a tubing hanger.

Description

(1) Embodiments of the present invention shall now be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 shows a schematic representation of a prior art casing system;

(3) FIG. 2 shows a bore hole cased in accordance with the present invention; and

(4) FIG. 3 shows an improved well head in accordance with one aspect of the present invention.

(5) FIG. 1 shows the construction of a well bore 10 in which traditional casing methods are used. At the surface 1, a conductor 12 is inserted into the first drilled section and cemented into place. This conductor 12 typically has a diameter of between 30 and 36 inches and acts as a support for drilling equipment during the rest of the bore hole creation. In addition this also serves to conduct drilling mud from the bottom of the hole to the surface once drilling starts. Situated within the conductor 12 is the surface casing 16. This is narrower in diameter than the conductor 12, typically approximately 20″, and is intended to isolate fresh water zones such that these are not contaminated during drilling. The length of the surface casing 16 therefore depends on the area in which the well bore is being drilled.

(6) Positioned on the surface casing 16 within the conductor 12, is the well head 14. The well head 14 extends above the ground, or seabed, in order to connect the well bore to a number of external components such as the Xmas tree and marine riser. The oil or gas retrieved from the reservoir will be transported through the marine riser from the well head 14 to a storage container on the ship or rig to which the riser is connected. The Xmas tree provides means for injecting chemicals or fluids into the well bore as well as valves and gauges for monitoring and controlling oil or gas extraction.

(7) In order to drill further sections of the well bore the drill bit and drilling string are lowered into the bore 10 and drill through the surface casing 16 deeper into the ground. Drilling mud is pumped down through the drill string to the drill bit and up the annulus between the drill string and the bore hole in order to carry cuttings to the surface. Due to changes in formation pressure as the depth of the well is increased, it is normally necessary to case sections of the well as drilling progresses such that the hydrostatic pressure of the drilling fluid can be maintained between the formation pore and fracture pressures.

(8) For example, an initial section of well bore may be drilled having a 13⅜″ diameter. This is then cased by casing 17. After casing of this section drilling can now continue with a different hydrostatic pressure, but the newly drilled well bore must have a smaller diameter and hence this next section of the well bore will be cased with a narrower casing. In FIG. 1 second casing 18 has a first internal diameter of 10¾″ and a second, main internal diameter of 9⅝″. The part of the casing which provides support to the well bore has the second diameter whereas the wider section of casing 18 is located in the well head 14. This widened portion of casing 18 provides slightly more room within the well head for, e.g. downhole lines and valves. Casings 17, 18 extend into the bore hole from well head 14, where they are hung on casing hanger 15. Further, narrower sleeve components may be added as required until the oil reservoir is reached. All the casings located radially within the well head 14 are hung from casing hanger 15. The final section of well bore 10 is cased by liner 19. This is hung from the previous casing 18 by liner hanger 19a. After drilling and casing is complete, production tubing 191 is run through the well bore to the liner 19. This tubing 191 is typically around 7″ in diameter with a 6″ inner diameter. This width is necessary in order to allow reasonable extraction times. A production packer (not shown) seals the end of production tubing 191 and liner 19 from the annulus between tubing 191 and casing 18. In a similar way to casings 17, 18 the production tubing 191 extends to the well head 14 where it is hung from tubing hanger 13. Downhole safety valve (DHSV) 11 forms part of the production tubing 191 and is used to close this tubing in the event of a blow out.

(9) In the conventional systems of the type illustrated by FIG. 1, the inner diameter of the well head 14 is dictated by casing hanger 15. All the casings 17, 18 passed through the well head during bore hole construction must be attached to this hanger 15 and therefore this has an outer diameter similar to that of the widest casing hung from it.

(10) FIG. 2 shows a bore hole 20 cased according to an embodiment of the present invention.

(11) As is the case with prior art systems, a conductor 22 is initially installed and cemented. This conductor 22 has a standard width of 30 to 36″. The diameter of the conductor 22 is not altered by the present invention and can vary depending on the requirements of the well.

(12) A hole is then drilled through the base of the conductor 22 with a width suitable for housing surface casing 26 having an 11¾″ diameter. Attached to this surface casing 26 is well head 24. The internal diameter of well head 24 is 11″. This reduction in diameter enables a smaller marine riser to be used and hence provides great benefits in relation to high pressure systems as well as reducing mud volumes, drill cuttings and liner volumes.

(13) This reduction in well head diameter is enabled firstly by removing the need for a casing hanger. After installation of the well head 24, all further sleeve components are liners. Liners, like casings, seal and support the bore hole and prevent liquid and gases from seeping into or out of the rock formations in which the bore hole 20 is drilled. However, unlike casings liners do not extend to the surface 2 of the bore hole 20 and instead extend to just above the base of a previous sleeve component, to which they are fastened.

(14) Furthermore, in order to maintain the necessary diameter of the bore hole, expandable liners are used. Although, due to the deformable nature of expandable liners, these cannot be rated to full pressure integrity, these liners are useful during well bore construction. An expandable liner can be used to temporarily case a section of well bore during drilling of a later section, after which a conventional liner can be placed within the expandable liner to increase the pressure integrity of the well bore.

(15) This is shown in FIG. 2. Surface casing 26 includes a pre-made recess shoe 26a. This shoe 26a is slightly wider in diameter than the remainder of the surface casing 26. After the next section of well bore has been drilled an expandable liner 27 is inserted. This liner 27 has an initial outer diameter of 9⅝″. However, once this has been positioned within the well bore the liner 27 is expanded to a final diameter of 11¾″, i.e. the same diameter as the surface casing 26. The expandable liner 27 expands into and forms an interference fit with recess shoe 26a of casing 26. However, in the Figure a slight gap has been shown between these two components for clarity. The expandable liner 27 is therefore held in position within the well bore 20.

(16) Following the insertion and expansion of expandable liner 27 the next section of well bore can be drilled. As the liner has been expanded to the same diameter as surface casing 26, no change in drill bit size is required. After the next section of well is drilled a conventional liner 28 is hung from liner hanger 28a. This liner hanger 28a is located on surface casing 26, above the recess shoe 26a. Therefore, liner 28 extends from above expandable liner 27 to below this.

(17) Liner 28 therefore cases the newly drilled well section and entirely overlaps the expandable liner 27. The expandable liner 27 can therefore be seen as a temporary liner as, after installation of conventional liner 28, expandable liner 27 no longer forms part of the active casing.

(18) Liner 28 can have a pre-made recess shoe or its base can be widened once in position downhole to create an expanded recess shoe 28b. Drilling then continues and a further expandable liner 271, having an initial diameter of 8″, is inserted into the bore hole and expanded into recess shoe 28b of liner 28. The expanded diameter of liner 271 is 9⅝″. Following the expansion of this liner 271 drilling can again continue and a liner 29 having a diameter of 7″ or 7⅝″ can be hung from lining hanger 29a from liner 28 such that this fully overlaps and extends past expandable liner 271.

(19) Liner 29 is not uniform in diameter. The top section of this liner is slightly enlarged to allow production tubing 291 to enter the liner 29. This enlargement is exaggerated in FIG. 2 for clarity. The diameter then decreases to 7″ or 7⅝″, the same diameter as the production tubing 291. Production packer 25 is located above this interface to seal this against any potential leakage. Alternatively designated sealing can be positioned between the enlarged section of liner 29 and production tubing 291.

(20) This allows a five string well bore to be created having a well head 24 with an internal diameter of 11″ while still providing a 7″ diameter production tubing 291. This production tubing 291 extends down the length of the well bore to liner 29. The production tubing 291 is hung within well head 24 by tubing hanger 23. By casing the well bore using liners no casing hanger is required and so the downhole safety valve 21 of production tubing 291 can be located inside the 11¾″ surface casing 26. This increased room allows the DHSV 21 to be larger and for more downhole control lines to be inserted and potentially also a small bore line for gas lift purposes.

(21) FIG. 3 shows a preferred embodiment of the present invention in which well head 34 comprises through holes 34a through which downhole control lines can be fed.

(22) Although only two holes are shown in FIG. 3, more can be positioned at angular intervals around the central bore. In conventional systems these control lines are fed through the tubing hanger 33 into the annulus between the casing wall 36 and production tubing 391. This requires the tubing hanger 33 to have a suitably wide diameter to enable machining of through holes and the attachment to the associated Xmas tree couplings. By removing this requirement from the tubing hanger 33, the diameter of this component can be reduced, allowing a similar reduction in the internal diameter of the well head 34. The increased thickness of the well head 34 increases the strength of this component and hence its structural integrity is maintained despite through holes 34a. Removing the through holes from the tubing hanger 33 and placing these within well head 34 allows the internal diameter of the well head 34 to be reduced to 9″.

(23) The downhole lines are fed through holes 34a and connected to the tubing hanger 33 by penetrater couplings 35. At the surface of the well head 34 vertical couplings can connect the exiting downhole lines to the Xmas tree in a similar way as was previously achieved between the Xmas tree and the tubing hanger 33.

(24) The surface casing 36 has a diameter of 11¾″ and therefore the downhole sections of the well bore (not shown) can be identical to that shown in FIG. 2.

(25) However, narrower liners can also be used in certain situations.

(26) Two casing methods are outlined below.

(27) 7″ Completion

(28) A 36″ or 42″ hole is drilled on the seabed and a 30″ or 36″ conductor is installed and cemented. A suitable hole is then drilled for 11¾″ surface casing with a pre-made recess shoe. The 11¾″ surface casing and attached 11″ well head is installed and cemented.

(29) A hole is drilled out of the surface casing and reamed up to the necessary diameter for installing a 9⅝″×11¾″ expandable liner. The liner is run and expanded out of the recess shoe of the surface casing. The expandable liner is cemented if necessary. A hole is then drilled out of the expanded 9⅝″×11¾″ section and reamed up to a suitable diameter for installing a 9⅜″ liner. The 9⅜″ liner is run and hung off in the lower end of the surface casing, above the recess shoe, thus overlapping (covering) the 9⅝″×11¾″ expandable liner. This is then cemented and the lower end of the 9⅜″ liner is expanded downhole to create a recess shoe.

(30) A hole is drilled out of the 9⅜″ liner and reamed to a suitable size for a 7⅝″×9⅜″ expandable liner. The 7⅝″×9⅜″ expandable liner is run and expanded out of the recess shoe of the previous 9⅜″ liner. A hole is drilled and reamed (if necessary) up to a suitable dimension for installing a 7″ or 7⅝″ liner. This liner is run and hung off in the lower end of the first (conventional) 9⅜″ liner, above the expanded recess shoe, thus overlapping (covering) the 7⅝″×9⅜″ expandable liner. This final liner is cemented if necessary.

(31) The well is now ready for completion with 7″ production tubing. The DHSV is located in the 11¾″ surface casing.

(32) 5½″ Completion

(33) This follows the same steps as above until the installation of the 7″ or 7⅝″ liner. After installation, a hole is drilled out of this liner and reamed to a suitable size for a 5″ or 5½″ liner. The liner is run and hung off in the lower end of the previous liner section and cemented if applicable. This well is now ready for completion with 5½″ production tubing. Once again the DHSV is located in the 11¾″ surface casing.

(34) By using a 9″ improved well head comprising through holes the well bore and sleeve component diameters could be reduced further.

(35) Therefore, the present invention enables small bore wells to be created without reducing production tubing diameter. It will be appreciated that the embodiments described above are preferred embodiments only of the invention. Thus various changes could be made to the embodiments shown which would fall within the scope of the invention as defined by the claims. For example, the bore hole casing could consist of only one expandable liner or the improved well head shown in FIG. 3 could be used in a casing system which does not involve expandable liners.