Patent ID: 12196081

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

To form a lateral well from a main well, a wellbore liner is first lowered into and installed in the main well. The wellbore liner can include a sidetrack profile, which is positioned at a depth within the main well from which the lateral well is to be formed. The position of the sidetrack profile within the main well defines a window in a sidewall of the main well. The lateral well can formed through the window by a milling bottom hole assembly (BHA). Forming the lateral well can also involve milling through a top of the wellbore liner to access the sidetrack profile.

Wellbore liners can be made using materials which can survive wellbore conditions (e.g., high temperatures and pressures, corrosive nature of well fluids such as hydrocarbons, drilling mud, and the like). Examples of such materials include metals such as alloy steels. Milling through such materials can not only be time consuming but also result in wear of the milling tools.

This disclosure describes a wellbore liner that is made of two different axial length segments, each of which is made of a different material. A first axial length segment is made of a first material which can survive wellbore conditions such as that described above. A second axial length segment, which is axially attached to the first axial length segment, is made of a second material that is softer than the first. The sidetrack profile is formed in the second axial length segment. When such a wellbore liner is installed within a main well, the milling BHA can mill through the softer material of the second axial length segment more easily than through the comparatively harder material of the first axial length segment. Consequently, a time to form, and wear and tear of equipment used to form the lateral well can be reduced. In addition, the softer material can reduce a weight of the wellbore liner, making it easier to lift cuttings resulting from milling the softer material out of the main well.

FIGS.1A and1Bare schematic diagrams of examples of a wellbore liner100made of two different materials installed within a main well102. The main well102can be formed from a surface of the Earth through a subterranean zone (e.g., a formation, a portion of a formation, multiple formations). For example, the main well102can be formed to a subsurface reservoir in which hydrocarbons are entrapped.

The wellbore liner100includes a first length segment104aand a second length segment104b, both of which are axially attached to each other. The first length segment104ais made of a material such as hard metal such as steel. The second length segment104bis made of a comparatively softer material, e.g., a composite, aluminum, fiberglass, to name a few. Both materials can be of a type that can survive wellbore conditions. The material with which the second length segment104bis made can be easier to mill compared to the first material with which the first length segment104ais made. By easier to mill, it is meant that the time taken by a milling tool to mill the second length segment104bis less than the time taken to mill the first length segment104a. In addition, a wear and tear on the milling tool resulting from milling the second length segment104bcan be less than a wear and tear resulting from milling the first length segment104a.

Further, a length of the second length segment104bcan be selected to accommodate a window of a lateral well (described later). A length of the first length segment104acan be selected according to a well operation to be performed using the first length segment104a. The length of the first length segment104aand the second length segment104bcan be based on the formation behind the liner and target coordinates.

In some implementations, the first length segment104aand the second length segment104bare axially connected to each other by threads formed on ends of the two length segments. In some implementations, a packer106can be coupled to an end of the second length segment106bopposite from an end to which the first length segment106ais coupled. The packer106can be coupled directly to the end. Alternatively, a liner, which is shorter in length compared to the first length segment104acan be positioned between the packer106and the end of the second length segment104b.

In some implementations, the wellbore liner100can be hung within the main well102from a wellbore liner hanger108supported by an inner wall of another wellbore tubular (not shown), e.g., a casing. The packer106can be installed within the wellbore liner hanger108to isolate a portion of the main well102downhole of the packer106from a portion of the main well102uphole of the packer106. Another liner110can be connected uphole of the packer106and can be used to flow well fluids from a surface through the liner110and the wellbore liner100. The dimensions of the liner110, the packer106and the second length segment106bcan each be of a size sufficient for a milling tool (described later) to mill through.

FIGS.2A-2Fare schematic diagrams of examples of forming a lateral well202using the wellbore liner100ofFIGS.1A and1B.FIG.2Bshows the wellbore liner100installed within the main well102as described above with reference toFIGS.1A and1B. To install the wellbore liner100, the liner100is first hung from the wellbore liner hanger108. Then, the annulus between the outer surface of the liner100and the inner wall of the wellbore100is cemented. In some implementations, only the first length segment104a(i.e., the downhole length segment) can be cemented while the second length segment104b(i.e., the uphole length segment) is not cemented.

FIG.2Bshows an example of a milling bottom hole assembly (BHA)204, which includes a milling tool, being deployed to mill through the second length segment104b. The milling BHA204can be run into the main well102from a surface. The milling tool in the milling BHA204can mill through a top of the liner110, the packer106, and the second length segment104bof the wellbore liner100. Because the second length segment104bis made of a softer material compared to the first length segment104a, the milling operation takes less time, and the milling BHA204experiences less wear and tear.

FIG.2Cshows an example of the milling BHA204milling the second length segment104b. In some implementations, the milling BHA204can be deployed to mill an entirety of the second length segment104b. Alternatively, the milling BHA204can be deployed to mill less than an entirety of the second length, the milled portion being sufficient to sidetrack the lateral well202. In particular, the milling BHA204is deployed to drill the second length segment104b(or a sub-portion of the second length segment104b) without also drilling the first length segment104a.

FIG.2Dshows an example of cleaning debris resulting from the milling operations performed using the milling BHA204. The debris can be cleaned by deploying a cleaning sub-assembly206from a surface of the main well102. For example, the cleaning sub-assembly206can include a tubular208that can flow a cleaning fluid (e.g., water) or other cleaning fluid from the surface of the main well102. For example, the cleaning sub-assembly206can include flow equipment (e.g., a flow pump, a reservoir to carry the cleaning fluid) at the surface. The portion of the cleaning sub-assembly206deployed within the main well102can include ports through which the cleaning fluid is circulated (as schematically represented by the arrows210) to remove the debris from within the main well102. Upon completion of milling using the milling BHA204and cleaning using the cleaning sub-assembly206, a 360 degree sidetrack212is available to form the lateral well202. The sidetrack212occupies the space previously occupied by the portion of the second length segment104bthat was milled by the milling BHA204.

FIGS.2E and2Fshow a whipstock214being deployed in the main well102after the sidetrack212has been formed. In some implementations, the whipstock214is lowered to a depth within the main well102and more specifically into the first length segment104a. The whipstock214includes a packer216that can be set at a desired depth in the first length segment104a. In implementations in which less than an entirety of the second length segment104bhas been milled, the packer216of the whipstock214can be set in the remainder of the second length segment104b. A drilling sub-assembly218can be deployed from the surface of the main well102to form the lateral well202through the sidetrack212.

FIG.3is a flowchart of an example of a method300of forming the lateral well using the wellbore liner ofFIGS.1A and1B. The steps of the method300can be performed by a well operator using the well equipment described above with reference toFIGS.2A-2F. At302, a wellbore liner that includes a first length segment and a second length segment is formed. The first length segment is made of a wellbore liner material, e.g., steel. The second length segment is made of a material softer than the wellbore liner material, e.g., composite, aluminum. Both materials can operate under wellbore conditions. The first length segment is axially attached to the second length segment. At304, the wellbore liner is run into and installed in a main well. When installed, the second length segment is uphole of the first length segment. A window to form a lateral well is at a depth at which the second length segment is installed within the main well. At306, using a milling BHA, the second length segment is milled through to access the window. At308, after milling through the second length segment to access the window, the lateral well is formed from the window.

Thus, particular implementations of the subject matter have been described. Other implementations are within the scope of the following claims.