Methods and apparatus for creating wellbores

Abstract

A method of creating a horizontal wellbore section comprises drilling the section in at least two stages. The method comprises drilling a first horizontal bore section. The first horizontal bore section is then provided with a first liner having a wall including initially-closed flow ports. The first liner isolates the wall of the first bore section. A second horizontal bore section is then drilled beyond the first horizontal bore section. The second horizontal bore section is provided with a second liner. Stimulation fluid is then directed into the first and second liners so that the stimulation fluid passes through the wall of the second liner to stimulate the second horizontal bore section. The flow ports in the wall of the first liner are then opened so that the stimulation fluid passes through the wall of the first liner to stimulate the first horizontal bore section.

Claims

1. A method of creating a horizontal wellbore section, the method comprising: drilling a first horizontal bore section with a bore wall having a first bore diameter; lining the first horizontal bore section with a first liner having a wall, the wall of the first liner comprising initially closed flow ports; isolating the wall of the first bore section with the first liner, without the use of cement, to minimize the pressure differential during drilling the second horizontal bore section by isolating a first annulus between the wall of the first horizontal bore section and the first liner; subsequently drilling a second horizontal bore section beyond the first horizontal bore section which includes the first liner therein, the second horizontal bore section having a bore wall with a second bore diameter; lining the second horizontal bore section with a second liner; directing stimulation fluid into the first and second liners so that the stimulation fluid passes through the wall of the second liner to stimulate the second horizontal bore section; and opening flow ports in the wall of the first liner so that the stimulation fluid passes through the wall of the first liner and through the first annulus to stimulate the first horizontal bore section.

2. The method of claim 1, wherein one or both of the first horizontal bore section and the second horizontal bore section are drilled until a predetermined differential pressure over a length of the bore section is reached.

3. The method of claim 2, wherein the predetermined differential pressure over the length of the bore section is 800 psi.

4. The method of claim 1, comprising initially closing the flow ports in the wall of the first liner with plugs that are at least partially soluble in the stimulation fluid.

5. The method of claim 1, wherein the stimulation fluid comprises an acid.

6. The method of claim 1, comprising flowing fluid from the formation and into the well through the flow ports.

7. The method of claim 1, wherein bore fluid is isolated within the first annulus.

8. The method of claim 1, comprising activating at least one barrier provided on the first liner to engage with the wall of the first bore section.

9. The method of claim 8, wherein the at least one barrier is provided at a distal end of the first liner.

10. The method of claim 9, wherein at least two barriers are provided towards the distal end of the first liner.

11. The method of claim 8, wherein the at least one barrier is provided towards a proximal end of the first liner.

12. The method of claim 1, wherein the first liner has a first liner diameter and the second bore diameter is smaller than the first liner diameter.

13. The method of claim 1, wherein the second liner is provided with flow ports.

14. The method of claim 13, wherein the flow ports in the second liner are open when the second liner is installed in the second horizontal bore section.

15. The method of claim 1, wherein at least one of the first liner and the second liner is a controlled acid jetting (CAJ) liner.

16. A wellbore-lining apparatus for lining a horizontal wellbore section comprising first and second bore sections, the apparatus comprising: a first wellbore liner, comprising initially closed flow ports, having a wall and an isolation barrier towards a distal end of the wall, wherein the first wellbore liner extends through the first bore section and the isolation barrier is configurable to engage a wall of the first bore section, without the use of cement, to isolate the first bore section to minimize the pressure differential during drilling the second bore section by isolating a first annulus between the wall of the first horizontal bore section and the first liner; and a second wellbore liner for lining the second bore section beyond the first bore section.

17. The wellbore-lining apparatus of claim 16, wherein the first and second wellbore liners are configured to be installed in the wellbore separately.

18. The wellbore-lining apparatus of claim 17, wherein the first wellbore liner is configured to be installed in the first bore section and permit the second bore section to be drilled beyond the first bore section with the first wellbore liner installed therein.

19. The wellbore-lining apparatus of claim 17, wherein the second wellbore liner is configured to be installed through the first lined bore section and into the second bore section.

20. The wellbore-lining apparatus of claim 16, wherein the first wellbore liner has at least two isolation barriers towards the distal end of the wall.

21. The wellbore-lining apparatus of claim 16, wherein the first wellbore liner has at least one isolation barrier towards a proximal end of the wall.

22. The wellbore-lining apparatus of claim 16, wherein the flow ports are closed by plugs dissolvable by stimulation fluid.

23. The wellbore-lining apparatus of claim 16, wherein the second liner comprises flow ports.

24. The wellbore-lining apparatus of claim 23, wherein the flow ports in the second liner are initially open.

25. The wellbore-lining apparatus of claim 16, wherein the first liner has a first liner diameter and the second bore diameter is smaller than the first liner diameter.

26. The wellbore-lining apparatus of claim 16, wherein at least one of the first and second liners is a fixed diameter liner.

27. The wellbore-lining apparatus of claim 16, wherein at least one of the first liner and the second liner is a controlled acid jetting (CAJ) liner.

28. A wellbore-lining apparatus for lining a horizontal wellbore section comprising first and second bore sections, the apparatus comprising: a first wellbore liner having a wall including initially-closed flow ports for isolating the wall of the first bore section, without the use of cement, to minimize the pressure differential during drilling of the second bore section, by isolating a first annulus between the wall of the first bore section and the first the flow ports being closed by plugs dissolvable by stimulation fluid; and a second wellbore liner for lining the second bore section beyond the first bore section, wherein, in use, stimulating fluid directed into the first and second wellbore liners passes through the second wellbore liner to stimulate the second horizontal bore section, and the stimulation fluid dissolves the plugs in the first wellbore liner to open the flow ports in the wall of the first wellbore liner so that the stimulation fluid passes through the wall of the first wellbore liner to stimulate the first horizontal bore section.

29. The wellbore-lining apparatus of claim 28, wherein at least one bore wall-engaging barrier is provided on the first liner.

30. The wellbore-lining apparatus of claim 29, wherein at least one bore wall-engaging barrier is provided at a distal end of the first liner.

31. The wellbore-lining apparatus of claim 30, wherein at least two bore wall-engaging barriers are provided towards the distal end of the first liner.

32. The wellbore-lining apparatus of claim 29, wherein at least one bore wall-engaging barrier is provided towards a proximal end of the first liner.

33. The wellbore-lining apparatus of claim 28, wherein the plugs are acid soluble.

34. The wellbore-lining apparatus of claim 28, wherein the second liner comprises flow ports.

35. The wellbore-lining apparatus of claim 34, wherein the flow ports in the second liner are initially open.

36. The wellbore-lining apparatus of claim 28, wherein the first liner has a first liner diameter and the second bore diameter is smaller than the first liner diameter.

37. The wellbore-lining apparatus of claim 28, wherein at least one of the first and second liners is a fixed diameter liner.

38. The wellbore-lining apparatus of claim 28, wherein at least one of the first liner and the second liner is a controlled acid jetting (CAJ) liner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic representation of a wellbore;

(3) FIGS. 2 to 7 illustrate stages in the creation of a horizontal wellbore section; and

(4) FIG. 8 illustrates the pressure differential along the length of the horizontal sections during the drilling of the respective sections.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) Reference is first made to FIG. 1 of the drawings, which is a schematic representation of a wellbore 10, in accordance with an embodiment of the disclosure, the wellbore 10 providing access to a hydrocarbon-bearing formation 12. The wellbore includes a substantially vertical section 14 and a substantially horizontal section 16 which extends through the formation 12. The vertical section 14 and the initial part of the horizontal section 16 are lined with metal casing and liner 18, 20. The remainder of the horizontal section 16 features two lengths of controlled acid jetting (CAJ) liner 22, 24, as will be described below.

(6) It will be noted that the description below includes references to, for example, wellbore sections of particular lengths and diameters and liners of particular diameters. The skilled person will appreciate that these dimensions are provided merely by way of example and that the disclosure has utility in wellbores of any appropriate dimensions and may utilise liners and other apparatus of any appropriate dimensions.

(7) The creation of the horizontal section 16 will now be described with reference to FIGS. 2 to 7. The horizontal section 16 is drilled in two stages. Initially an 8½ inch diameter 10,000 feet first horizontal bore section 26 is drilled as illustrated in FIG. 2. During the drilling operation, the differential pressure between the distal and proximal ends of the annulus between the drill string and the wall of the bore section 26 may be up to, for example, 800 psi.

(8) As illustrated in FIG. 3, a 7 inch diameter liner 22 is installed in the section 26. The liner 22 has a wall 30 provided with acid-soluble plugs 32 and external annular barriers 34 are provided towards the ends of the liner 22 (two barriers 34 towards the distal end of the liner 22 and one barrier 34 towards the proximal end of the liner 22). The barriers 34 may take any appropriate number and form and may be, for example, mechanically expandable metal barriers; the liner 22 is run into the section 26 with the barriers 34 in a retracted configuration. The expanded barriers 34 engage with the wall of the bore section 26 (or a proximal barrier 34a may engage a wall of an existing casing or liner). The installed liner 22 thus isolates the wall of the first bore section 26, and in particular protects the formation surrounding the bore section 26 from high pressure fluid in the bore section 26.

(9) As illustrated in FIG. 4, a 6 inch diameter 10,000 feet long bore 36 is then drilled out of the distal end of the 7 inch liner 22 to create a second horizontal bore section 38 beyond the first horizontal bore section 26. During the drilling operation the differential pressure between the distal and proximal ends of the annulus between the drill string and the wall of the bore 36 may be up to, for example, 800 psi.

(10) A 4½ inch diameter controlled acid jetting (CAJ) liner 24 is then installed in the bore section 38, as illustrated in FIG. 5. The proximal end of the CAJ liner 24 is sealed and secured to the distal end of the 7 inch liner 22 using a liner hanger 42. The CAJ liner 24 has a pervious wall; typically, a CAJ liner will have a limited number of unevenly spaced pre-drilled holes in the wall of the liner, the hole pattern being chosen to facilitate diversion of stimulation fluid evenly along the respective horizontal bore section, as described below.

(11) Stimulation fluid 44 is then pumped into the horizontal section 16, as illustrated in FIG. 6. In the illustrated embodiment the stimulation fluid 44 comprises hydrochloric acid (HCl). The holes in the wall of the CAJ liner 24 permit the stimulation fluid to contact the wall of the second bore section 38.

(12) After a time, the acid-soluble plugs in the 7 inch liner 22 are dissolved by the stimulation fluid 44, permitting the fluid 44 to contact the wall of the first section 26, as illustrated in FIG. 7.

(13) The horizontal section 16 has thus been drilled, lined and stimulated without cementing. In particular, the first liner 22 isolates the wall of the first bore section 26 and protects the formation surrounding the bore section 26 while the second bore section 38 is drilled. FIG. 8 of the drawings illustrates the pressure differential along the length of the horizontal sections 26, 38 during the drilling of the respective sections. Without the requirement to cement the first bore section and then perforate and complete a cemented section, the extended horizontal section 16 may be drilled and be ready for production relatively quickly and inexpensively.

(14) The skilled person will of course understand that the particular parameters and dimensions utilised in the illustrated example are merely provided by way of example.

(15) The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason, the following claims should be studied to determine the true scope and content of this invention.