Method and Apparatus for Providing Selective Wellbore Access

The present invention relates to the field of well drilling and completion and more particularly, to methods and apparatus for drilling and completion of branching or multi-lateral wells with provisions for connectivity and isolation between the branching wellbores.

Although horizontal or lateral wells are well known in the art, horizontal well drilling and production have not been significant aspects of the industry until recently. Even though horizontal drilling is much more expensive than conventional vertical drilling, well production can be increased greatly when it is used appropriately. In general, productivity must be more or less tripled to justify the increased cost of a horizontal well. In the case of naturally fractured reservoirs and thin reservoirs, production can be increased tenfold or more, so that relative cost is not a deterrent to horizontal drilling. In many situations, the horizontal well is drilled as a lateral from a main vertical wellbore. This is an especially common practice on offshore platforms, where the increased production of a lateral well, or multilateral wells, allows a field to be developed with fewer platforms.

As a result of the increased usage of lateral wells, lateral and multi-lateral well completion and subsequent production and servicing have become an important concern. Well service operations require the ability to selectively reenter, or access subterranean wellbores to perform completion or well servicing work. It is desirable and cost effective for the system to be such that the selected wellbore can be accessed with a coiled tubing or wireline rig, so that the a full drilling rig is not required. Furthermore, it is desirable to minimize the number of trips required to access and work a selected lateral wellbore, the more cost effective a lateral well completion system will be. For example, U.S. Pat. No. 2,211,803, issued Aug. 20, 1940 to W. A. Warburton describes a selective access system, which requires multiple trips to install and remove a sleeve to selectively block access to a bore.

Only recently has the ability to access one or more lateral wellbores from a main wellbore become important within the exploration industry and present prior art devices do not address this need. Prior art multilateral wellbore completion systems presently employ sliding sleeves to open and close small ports specifically designed for circulation and production control purposes but not for providing tool access into a lateral wellbore. Consequently, these systems are ineffective for the more recent problems of completion, production and work-over of a wellbore with one or more lateral wellbores.

Therefore, the first object of the present invention is to provide an apparatus and method for main and multilateral wellbore completion and production with access capability for tools into any selected wellbore. A second object is that this system has the ability to provide connectivity and isolation as described above, so that structurally sound, hydraulically sealed junctures can be made between main and lateral wellbores. A third object is to provide tool access to such a system by coiled tubing or wireline rigs, so that the services of a full drilling rig will not be required. Yet another object is to minimize the number of trips required to access and work a selected lateral wellbore.

The present inventions contemplate improved methods and apparatus for providing main and multilateral wellbore completion and production, with access capability for tools into any selected wellbore, by providing gravity selection for main wellbore access and sliding sleeve selection for lateral wellbore access. Practice of the present inventions include some steps and apparatus well known in the oil field arts, and aspects previously discussed in pending U.S. application Ser. number 08/731,464, filed Oct. 15, 1996 now U.S. Pat. No. 5,735,350, the content of which is included herein by reference.

In the present inventions, a whipstock with a drillable center is set at the desired location for the planned lateral, a window is milled in the main wellbore casing and the lateral wellbore is drilled in accordance with the prior art. A liner for the lateral wellbore is set through the window, with a casing hanger above the window and the juncture is cemented. After completing the lateral wellbore, a smaller whipstock, referred to as a mill guide, is set in the lateral to guide a mill on a vertical path along the center of the main well bore. This operation makes a window in the liner and an opening through the drillable center whipstock for access to the main well. After this operation is complete, the smaller whipstock is pulled. Then an access sleeve housing, with a side window matching the liner window and an internal, two position, access selection sleeve is fitted into the liner. When the access selection sleeve is pulled up to a first position within the access sleeve housing, tools pass vertically downhole through its length and through the matching windows to access the main well in a gravity selection. When the access control sleeve is pushed down, to a second position, the matching windows are covered and tools are guided by the access selection sleeve directly into the lateral well.

Thus, the apparatus and method of the present invention provide direct, reliable main wellbore access downhole from the lateral wellbore as required when the matching windows are "opened" by pulling the access control sleeve to the "up" position so that the main wellbore is naturally selected and accessed by gravity. Positioning the access control sleeve includes the step of engaging a selective profile associated with the sleeve. In a preferred embodiment, there are two such profiles associated with the access control sleeve, a pushing profile for selecting lateral wellbore access and a pulling profile for selecting main wellbore access. In other embodiments, the step of positioning the access control sleeve for selective access may be accomplished by any of a number of mechanical, hydraulic or electrical systems.

The accompanying drawings are incorporated into and form a part of the specification to assist in explaining the present inventions. The drawings illustrate preferred and alternative examples of how the inventions can be made and used and are not to be construed as limiting the inventions to only those examples illustrated and described. The various advantages and features of the present inventions will be apparent from a consideration of the drawings in which:

FIG. 1 is a vertical section view showing a lateral wellbore configuration as prepared for opening a window in the lateral liner;

FIG. 2 is a vertical section view of a lateral wellbore wherein the access control sleeve assembly is configured for gravity selection of the main wellbore;

FIG. 3 is a vertical section view of a lateral wellbore wherein the access control sleeve assembly is configured for selection of a lateral wellbore;

FIG. 4 is a vertical section view of the access control sleeve assembly of the present invention; and

FIG. 5 is a view section to FIG. 1 showing a lateral wellbore configuration with the access control sleeve assembly installed therein.

The present inventions are described in the following by referring to drawings of examples of how the inventions can be made and used. In these drawings, reference characters are used throughout the several views to indicate like or corresponding parts. FIG. 1 illustrates a well with a subterranean main and lateral bore intersection wherein the methods and apparatus of the present inventions are to be applied. The details of these methods and apparatus are illustrated in FIGS. 2-4.

The terms lateral and main are used herein to identify subterranean intersecting or branching wellbores. Although these terms are used in a variety of ways in the art, as used herein "main" is defined as that well or bore which for whatever reason tools and other devices will ordinarily enter at the subterranean intersection. In other words, tools will be more likely to enter the main well or bore at the intersection. A "lateral" is a well or bore, which tools and other devices ordinarily will not enter. In other words, tools will be less likely to enter the lateral well or bore at the intersection. The ordinary selection of or entrance into the main well or bore by tools could be caused by gravitational forces or bore orientation, location, size, or the like. The modifiers "lateral" and "main" are not intended or used to identify which bore or well was formed first or which has more or less horizontal or vertical orientation. To the extent that the industry may ascribe a different, broader, or narrower meaning to these terms, it is not intended for this application.

In FIG. 1, main wellbore casing 110 is set in primary wellbore 200. Whipstock 114 is set on whipstock packer 116 at a location and orientation for use in creating a window 112 in a side wall of casing 110. Preferably, whipstock 114 has a soft, drillable core 114C for purposes to be described later. Lateral liner 120 hangs from liner hanger 118 and extends through window 112 into lateral wellbore 300 and the well juncture has been sealed, preferably by using a cementitious material by one of many processes well known to those skilled in the art. A second whipstock or mill guide 142 has been set in lateral liner 120 where it is positioned and held by whipstock packer 144. Preferably, whipstock 142 has been set after completion work in lateral wellbore 300 is substantially complete. Whipstock 142 is located and oriented to guide a conventional mill or mills (not shown) along the central axis of main wellbore casing 110 so as to create a window in a side wall of lateral liner 120.

In FIG. 2, it is seen that window 134, in alignment with main wellbore casing 110 and whipstock 114, has been created in the side wall of lateral liner 120 and that drillable core 114C has been removed by milling to leave an open center or passageway. The subsequent removal of mill guide 142 and enlargement of the window allows installation of the present inventions to be completed. Bent deflector 128, assembled on the leading end of completion tubing 122, scrubs along the inside wall of liner 120 as it is run into the hole so as not to pass through window 134. Instead, deflector 128 follows lateral liner 120 into the lateral well 300. Sleeve assembly 160 is positioned within lateral liner 120 and includes a housing 124 packed off in tubing 120 by top packer 130 and completion tube packer 126. Access sleeve housing 124 includes a window 132, proximate to and aligned with lateral liner window 134, and of substantially equal overall size to allow tool passage therethrough.

Access selector sleeve 136 is mounted to axially slide in housing 124. In FIG. 2, sleeve 136 is shown in an "up" position, wherein it is above access sleeve window 112 so that tool passage through aligned windows 132 and 134 is unobstructed. Thus, when access selector sleeve 136 is in this position, coiled tubing or wireline tools fit with suitable flexible couplings that are run downhole will select the main wellbore under the influence of gravity. Seal rings 138 and 140, on access selector sleeve 136, are not called upon to provide sealing in this position shown, and are preferably dimensioned to be lightly loaded or out-of-contact.

FIG. 3 shows the sleeve assembly installation of FIG. 2, with access selector sleeve 136 shifted into a "down" position. In FIG. 3 the aligned windows 132 and 134 are closed to provide access to the lateral well. Coiled tubing tools that are run downhole with access selector sleeve 136 in this position will be reliably guided into the lateral well completion tube. In this position, seal rings 138 and 140 are in sealing contact with the inner wall of access sleeve housing.

FIG. 4 is a detailed view of one embodiment of the access sleeve housing 124 and access selector sleeve 136. Access selector sleeve 136 is shown in the "downhole" position moved axially against shoulder 125A closing sleeve housing window 132 so as to provide guided access to lateral wellbore 300. Shoulder 125A provides a stop to limit travel of sleeve 136 in housing 124. Alternatively, access selector sleeve 136', shown in phantom lines, is in the "uphole" position moved axially against shoulder 125B, wherein sleeve housing window 132 is unobstructed or "open." Shoulder 125B provides a stop to limit travel of sleeve 136 in housing 124. It is envisioned that other forms of mechanical stops could be used such as pins, snap rings and the like to confine the travel of sleeve 136 and to provide positive locator stops and to prevent the sleeve's inadvertent dislodgment from the housing. Access sleeve housing 124 has an enlarged internal diameter 124D except at areas contacted for sealing by seal rings 138 and 140. Additionally, the internal diameter at sealing area 124B, where sealing contact is made by seal ring 138, preferably is slightly smaller than the internal diameter at sealing area 124A, where sealing contact is made by seal ring 140. The internal clearance provided between access selector sleeve 136 and the internal diameters of access sleeve housing 124A permit free movement of access selector sleeve 136 between "up" and "down" positions. The width of access sleeve housing window 132 is less than the internal diameter of sealing area 124B, so there is no possibility of losing access selector sleeve 136 as it moves across its opening. Other methods for guiding the sleeve such as mating pins and slots or the like can be used.

A releasable position lock or latch for sleeve 136 is provided by detent spring 146. Spring 146 is a discontinuous ring mounted in retaining groove 148. Detent spring 146 is compressed by the diameter of sealing area 124A and will expand to engage the lower position detent groove 150. In a similar manner, sleeve 136 is retained in the "up" position by the upper position detent groove 170. A significant axial force, in the order of 10,000-20,000 pounds, is required to override the retaining force of detent spring 146 when so engaged. Although a ring-groove assembly is shown for latching the sleeve in axial position, other mechanical locking deices could be used.

Various methods and apparatus, well known in the art, may be used to shift access selector sleeve as desired. For example, a tool, with a spring loaded profile, or key, that will only lock into the discreet profile 152, may be used to find and engage access selector sleeve 136. Position may then be shifted by jarring "up" or "down." In an alternative , discreet "down" and "up" (opening and closing) shifter profiles may be provided, together with cams that disengage the tool from the profile at the end of the stroke and engage a position retaining latch. Putting the opening and closing shifter keys at or near the bottom of the tool string gives the ability to shift access selector sleeve 136 to select the lateral well as the tool string is run in, and to return selector sleeve to its original "main well" position as the tool comes out of the hole.

FIG. 5 shows the present inventions as used to provide selective access to a previously existing lateral well installation 172. Here, lateral well 174, with lateral well liner 180, joins main well 176 with casing 178. Sleeve assembly 182 has been guided into lateral well literal 180 by tail pipe 184, so as to be installed across the wellbore juncture, extending from main well 176 into lateral well 174. Sleeve housing 186 of sleeve assembly 182 is supported at the upper end by casing hanger 188 and sealed off at the lower end, in lateral well 174, by packer 198. Tubular sliding sleeve 192, fitted within sleeve housing 186, is shown in the upper position. In this position, access is provided to the distal portion of main well 176 through alignment of the length of sleeve 192 and the opening of side window 190. Side window 190 is centrally located and vertically aligned with the center of main well 176 so that down hole tools will select main well 176 by gravity. As described in previously discussed embodiments, sliding sleeve 192 may be selectively moved to a second, bottom position, where side window 190 is covered, so as to close off access to main well 176 and sliding sleeve 192 is aligned to direct downhole tools to lateral well 174. In this bottom position, sleeve seals 194 and 196 engage sleeve housing 186, in the manner shown in FIG. 4, so that pressure in lateral well 174 is isolated from main well 176.

The embodiments shown and described above are exemplary. Many details are well known in the art and, therefore, are neither shown nor described. It is not claimed that all of the details, parts, elements, or steps described and shown were invented herein. Even though numerous characteristics and advantages of the present inventions have been described in the drawings and accompanying text, the description is illustrative only, and changes may be made in the detail, especially in matters of shape, size, and arrangement of the parts within the principles of the inventions to the full extent indicated by the broad general meaning of the terms used in the attached claims.

The restrictive description and drawings of the specific examples above do not point out what an infringement of this patent would be, but are to provide at least one explanation of how to use and make the inventions. The limits of the inventions and the bounds of the patent protection are measured by and defined in the following claims.