CN1205403C - Method for creating secondary sidetracks in a well system - Google Patents

Abstract

A method is disclosed for creating one or more secondary sidetracks in an oil and/or gas well assembly which comprises a primary wellbore (2) and one or more primary sidetracks (6) so that a root-like multilateral well structure is created. The method makes use of an expandable well liner (9) in the primary sidetracks (6) so as to create a liner having a sufficient internal width to allow sidetracking equipment to be inserted and operated in the primary sidetrack to drill and complete the secondary sidetracks (7).

Description

Method for generating auxiliary branches in a well system

field of invention

The present invention relates to a method for generating auxiliary branches in a well system comprising a main wellbore into which one or more main branches enter.

Background technique

Such a well system is known from International Patent Application WO 98/49424.

One difficulty that arises with such a well system is that conventional wells have compressive properties resulting from the insertion of a casing in the main well at various stages of the drilling process, and the later inserted casing sections need to have a smaller diameter than the previously installed casing sections. and the bushing that is subsequently inserted into the main branch needs to have an outer diameter much smaller than the inner diameter of the casing of the main wellbore at the point of branching so that the bushing can be smoothly inserted into the main branch from the main wellbore .

As a result the bushing of the main branch has a relatively small diameter, so that it is impractical and economically impractical to drill the auxiliary branch away from the main branch.

From the article "How Multilateral Wellbores Affect the Final Recovery Strategy" on July 1, 1997, No. 57, No. 7 (Vol.57, No.7) of the magazine "Offshore", it can be known that by placing auxiliary branches A multilateral well sequence with auxiliary laterals is accomplished for perforation completions, wherein the auxiliary laterals are connected to the main well laterals. This article also describes that tubular liners and Y-shaped branch point liners can be inserted into multilateral wells, but does not disclose how to insert these liners into the well. The article "Expandable Slotted Tube Provides Advantages to Well Design" in Issue 69, No. 10, October 1, 1996, of the magazine "Petroleum Engineer International" describes a multilateral well. The system can be lined with expandable slotted tubing to stabilize the wellbore and minimize the size of the wellbore. A disadvantage of using expandable grooved tubing is that they do not provide a fluid tight seal between the inside and outside of the wellbore.

It is an object of the present invention to provide a method of generating one or more auxiliary laterals in a well system in an efficient and economical manner.

Contents of the invention

According to the present invention, there is provided a method for producing an auxiliary branch in a well system producing hydrocarbon fluids, said well system comprising a main wellbore and a main branch into the main wellbore, The methods include:

- Insert an unexpanded expandable bushing in the main branch;

- Radial expansion of the liner whereby the expanded liner provides a steel wellbore;

- creates an opening in the expanded liner wall; and

- Drilling an auxiliary branch in the formation of hydrocarbons through said opening.

The preferred expandable liner is a steel liner which is expanded by pressing or pulling a mandrel and/or roller provided with a tapered wear outer surface through the liner.

The expanded bushing has an inner diameter large enough to allow drilling and/or detaching equipment to be inserted into the main branch for drilling one or more auxiliary branches which also have an internal width large enough to provide a The role of well branching, hydrocarbon fluid can flow into the well system through auxiliary branching.

Thus the method of the present invention can form a rooted well system to provide an optimal drainage of hydrocarbon fluids from hydrocarbon-rich formations even if the formation has low permeability.

In an attractive embodiment of the method of the present invention, the expandable liner is formed by a coiled tubing through which the drilling fluid is pumped to a downhole drilling assembly used to drill the main branch, and the The coiled tube expands radially after the main branch has been drilled.

Also the auxiliary branches can be drilled using a coiled tube which expands to form an expanded bushing after the drilling operation is completed.

Alternatively the secondary branch can be lined using an expandable slotted bushing whose slots are staggered and open into diamond shaped holes as the bushing expands. Such an expandable slotted liner is known from US patent 5,366,012. Such a slotted liner can be surrounded in the inflow region of the auxiliary branch by an expandable sand screen, such a sand screen being disclosed for example in International Patent Application PCT/EP96/04887.

In a suitable reservoir formation, the secondary branch may be an open uncased hole, and if the storage formation is very unstable, the secondary branch may be lined with an expanded or unexpanded liner that was initially ungrooved, Perforations are shot in the liner using a known perforation gun.

The present invention also relates to a rooted well system produced in accordance with the present invention comprising a main wellbore into which one or more main branches comprising an expanded expandable liner enter, wherein the liner provides In addition to the steel wellbore, the well system also includes one or more auxiliary branches that enter the main branch through one or more openings in the expanded liner wall.

It will be appreciated that the use of expandable tubulars in a branched well system allows the tubulars in the main or parent well and in the main and auxiliary branches or well branches to have substantially the same internal width, thus forming a single bore branched well. In such a single-hole multi-branched well, a third branch can be drilled away from the auxiliary branch, and this branching process can be repeated, resulting in a true root-like multi-branched well system.

Description of drawings

Preferred embodiments of the method and system of the present invention are described below with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic sectional view of a well system of the present invention; and

Fig. 2 is a schematic cross-sectional view of a well system according to the present invention, the well system including a main branch into which two auxiliary branches enter.

Detailed ways

Referring now to Figure 1, there is shown a well system according to the present invention comprising a vertical main well 2 extending from a wellhead 3 at or near the surface 4 into an underground formation 5. Three main branches 6 enter the main borehole 2 . An auxiliary branch 7 enters each main branch 6 through an opening 8 in the wall of the expanded expandable steel bushing 9, only the section in the area of each opening 8 being shown.

The inner width of the bush 9 is enlarged by using the expanded bush. Thus, if each branched wellbore has a width of about 10 cm, the expanded liner may have an internal width of about 7-8 cm.

Such an internal width is the minimum requirement that a drilling assembly can be inserted into the main branch 6, and the drilling assembly can be used to drill the auxiliary branch 7 with sufficient width to allow hydrocarbons to pass through the auxiliary branch in sufficient quantities. 7 flows into the master branch.

Preferably the main wellbore 2 is also lined with an expandable steel casing which covers the wellbore during expansion in a manner similar to that of the expandable liner 9 covering the wellbore of the main branch 6 superior.

This makes it possible to further increase the inner width of the bushing 9 and the auxiliary branch 7 .

Both the main and auxiliary branches 6 and 7 extend into the hydrocarbon-rich formation 10, which is shown hatched in the figure.

Referring now to Figure 2, there is shown a vertical main borehole 20 from which a main branch 21 is drilled away from the main borehole at a horizontal plane.

The main branch 21 is lined with an expandable steel bushing 22 . Preferably the liner 22 is formed from a coiled tubing that has been used during drilling to supply drilling fluid to a drill bit (not shown) and to a hydraulic downhole pumping motor (not shown) for rotating the drill bit .

After completion of drilling, the coiled tubing is expanded to cover the wellbore and then acts as a wellbore steel liner for a main branch 21 .

A 4.5 inch (about 12 cm) shoe 22 and a plug 23 are then installed in the bushing 22 near the top end 24 of the main branch 21 .

An orientator 25 is then inserted and anchored in the bushing 22, and a suspension rod 26 having an inner width of about 7 cm is inserted into the expanded bushing 22 having an inner width of about 10 cm. A drilling assembly (not shown) is then passed through boom 26 and guided by orienter 25 to machine an opening in liner 22 and subsequently drill an auxiliary branch 30 in a hydrocarbon rich formation.

In the example shown, a conventional steel liner 31 is inserted into the auxiliary branch 30, which has an outer diameter of about 7 cm, and is pierced into the well inflow zone by a piercing gun (not shown).

After forming the first auxiliary branch 30, another orientator 32 is inserted and anchored in the expanded bushing 22 close to the end of the transverse main branch 21, thereby drilling another auxiliary branch 33 and as described with reference to the first auxiliary branch. Done in the same way.

After inserting a steel bushing 34 in the second auxiliary branch, either an opening (not shown) is drilled through the wall of the bushing 34 and through the orienter 34, or an already existing fluid passage in the orienter and a suspension Fluid passages in the rod 35 are used to allow hydrocarbon fluid to flow from the first auxiliary branch 30 and through the main branch 21 into the main wellbore 20 .

Claims (13)

1. A method for producing auxiliary branches in a well system (1) for producing hydrocarbon fluids from a hydrocarbon formation (31), said well system (1) comprising a main borehole (2, 20) and a main branch (6) entering the main wellbore (2, 20), the method comprising: inserting an unexpanded expandable liner (9, 22) in the main branch (6); and radially expanding A liner (9, 22), characterized in that said expanded liner (9, 22) provides a steel shaft; on the wall of the expanded liner (9, 22) in the main branch (6) An opening (8) is created; through said opening an auxiliary branch (7, 30, 33) is drilled in the hydrocarbon-rich formation (31). 2. A method according to claim 1, characterized in that both the main wellbore (2, 20) and the main branch (6) comprise expansion bushings (9, 22) providing a steel shaft through which the An expanding mandrel having a tapered wear-resistant outer surface and/or rollers passing therethrough is pushed or pulled to wrap against the wellbore. 3. A method according to claim 1, characterized in that the expandable liner (9, 22) is formed by a coiled tube through which the drilling fluid is pumped to a downhole drilling assembly for The main branch (6) is drilled and the coiled tube expands radially after the main branch (6) has been drilled. 4. The method according to claim 1 or 3, characterized in that: the auxiliary branch (7, 30, 33) is drilled by a drilling assembly, which is connected to a coiled pipe, and the auxiliary branch (7, 33) is drilled. , 30, 33) The post coil expands to form a bushing in the auxiliary branch. 5. A method according to claim 1 or 3, characterized in that the auxiliary branch (7, 30, 33) is lined along at least part of its length by an expandable slotted bush (31, 34), the The bushings (31, 34) are expanded inside the auxiliary branches so that a series of staggered slots open into diamond-shaped holes in the bushings. 6. A method according to claim 5, characterized in that an expandable sand screen is placed around the expandable grooved liner (31, 34) in the zone where the hydrocarbon fluid flows into the well system. 7. The method according to claim 1, characterized in that a non-expandable bushing (31, 34) is inserted in the auxiliary branch (30, 33), which bushing (31, 34) Perforated in the area of the well system. 8. A method according to claim 1, characterized in that the auxiliary branches (30, 33) are unsleeved along at least part of their length. 9. The method according to claim 1, characterized in that a plurality of main branches (6) enter the main wellbore (2) and a plurality of auxiliary branches (30, 33) enter at least one main branch (6). 10. A well system comprising at least one main branch (6) and at least one auxiliary branch (30, 33), wherein the main branch (6) comprises an expandable expandable liner (9), the liner (9) A steel shaft is provided and includes an opening into which the auxiliary branch (30, 33) enters. 11. Well system according to claim 10, characterized in that the expanded liner (9) in the main branch (6) has an internal width substantially equal to a casing in the main borehole (2, 20) the inner width of the . 12. Well system according to claim 11, characterized in that one or more third branches enter at least one auxiliary branch (7, 30, 33), thereby forming a root-like multi-branched well system. 13. Well system according to claim 10, characterized in that both the main wellbore (2, 20) and the main branch comprise expansion bushings (9, 22) providing a steel wellbore against which the wellbore wraps cover.

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