Guided wash pipe milling

Methods and apparatus for milling a window for a lateral wellbore in a casing string. An example method introduces a milling assembly into a primary wellbore, the milling assembly comprising: a whipstock, a guide bar coupled to the whipstock, and a wash pipe coupled to the guide bar. The method further includes running the milling assembly to a depth at which it is adjacent to the window in the casing string; securing the whipstock in the casing string; decoupling the wash pipe from the guide bar; guiding the wash pipe to mill the guide bar without milling the whipstock; and milling the window in the casing string with the wash pipe.

TECHNICAL FIELD

The present disclosure relates generally to wellbore operations, and more particularly, to the use of a guide bar for guiding the wash pipe milling of a lateral window in a multilateral well completion.

BACKGROUND

A multilateral well completion may include a primary wellbore extending vertically or horizontally in a subterranean formation. A casing string may be disposed in the wellbore. In some examples, a layer of cement may be disposed in the annulus between the casing string and the inside diameter of the primary wellbore. An exit window in the casing string may be used for drilling a lateral or secondary wellbore from the primary wellbore.

During the milling operation for the lateral wellbore, the deflection of the milling tool is necessary to orient the milling tool from the primary wellbore into the desired lateral window.

A whipstock may be installed within the primary wellbore at a location adjacent to the preselected exit window for the desired lateral wellbore. The surface of the whipstock is tapered toward the window to provide a transition surface to orient the milling tool toward the window for the desired lateral wellbore. Provided are improvements to wellbore milling operations, through the use of a guide bar for guiding the wash pipe milling of a lateral window in a multilateral well completion.

The illustrated figures are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different examples may be implemented.

DETAILED DESCRIPTION

The present disclosure relates generally to wellbore operations, and more particularly, to the use of a guide bar for guiding the wash pipe milling of a lateral window in a multilateral well completion.

In the following detailed description of several illustrative examples, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, examples that may be practiced. These examples are described in sufficient detail to enable those skilled in the art to practice them, and it is to be understood that other examples may be utilized, and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the disclosed examples. To avoid detail not necessary to enable those skilled in the art to practice the examples described herein, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the illustrative examples is defined only by the appended claims.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the examples of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. It should be noted that when “about” is at the beginning of a numerical list, “about” modifies each number of the numerical list. Further, in some numerical listings of ranges some lower limits listed may be greater than some upper limits listed. One skilled in the art will recognize that the selected subset will require the selection of an upper limit in excess of the selected lower limit.

Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. Further, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements includes items integrally formed together without the aid of extraneous fasteners or joining devices. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” Unless otherwise indicated, as used throughout this document, “or” does not require mutual exclusivity.

The terms uphole and downhole may be used to refer to the location of various components relative to the bottom or end of a well. For example, a first component described as uphole from a second component may be further away from the end of the well than the second component. Similarly, a first component described as being downhole from a second component may be located closer to the end of the well than the second component.

As used herein, the term “formation” encompasses the term “reservoir,” referring to a portion of the formation which has sufficient porosity and permeability to store or transmit fluids (e.g., hydrocarbons). As used herein, the term “fracturing fluid” refers generally to any fluid that may be used in a subterranean application in conjunction with a desired function and/or for a desired purpose. The term “fracturing fluid” does not imply any particular action by the fluid or any component thereof.

The examples described herein relate to the use of a guide bar for guiding the wash pipe milling of a lateral window in a multilateral well completion. The guide bar is coupled to a whipstock at the deflection surface of the whipstock. The wash pipe is coupled to the guidebar. The assembly of the guide bar, wash pipe, and whipstock are introduced into the wellbore together and run into the well in a single trip. When at the desired wellbore depth that is adjacent to the target exit window, the whipstock may be secured in the casing string. The wash pipe may then be decoupled from the guide bar and guided by the milling of the guide bar to the exit window in the desired orientation. The deflection surface of the whipstock is not milled as the guide bar guides the wash pipe to the window. The guide bar maintains its coupling to the whipstock until the guide bar is milled. Advantageously, the lateral milling operation is conducted in a single trip with the setting of the whipstock and the subsequent milling of the window occurring without the need for removal or insertion of any additional wellbore tools. As a further advantage, the wash pipe catches and retrieves the milled sections of the casing string which may greatly reduce the amount of debris left behind in the wellbore. An additional advantage is that the guide bar guides the wash pipe to cut the window straight. One more advantage is that the guide bar protects the whipstock from being milled by the wash pipe.

FIG. 1illustrates a cross-sectional view of a lateral wellbore milling assembly5. The lateral wellbore milling assembly5comprises a whipstock10, a guide bar15, and a wash pipe20. The whipstock10may be any species of whipstock useful for orienting and deflecting the drilling of a lateral wellbore off of a primary wellbore in a multilateral well completion. The whipstock10comprises a deflection surface25. The deflection surface25deflects the drilling equipment when the drilling of the lateral wellbore is to commence after the milling of the exit window30in the casing sting35. The exit window30is a window in the casing string35that may be targeted for milling and may comprise a portion of the casing string35designed to be easily milled relative to the remainder of the casing string35as would be readily apparent to one of ordinary skill in the art. For example, the exit window30portion of the casing string35may comprise materials that are easily milled. The deflection surface25of the whipstock10may guide the milling tool to the exit window30so as to be milled. The deflection surface25should not be milled as it must be intact to deflect and direct the drilling of the lateral window through the exit window30. In some examples, the exit window30portion of the casing string35is not premilled and/or does not require a pilot hole for milling.

With continued reference toFIG. 1, the lateral wellbore assembly5may be introduced into the wellbore as illustrated with the whipstock10coupled to the guide bar15, and the guide bar15coupled to the wash pipe20. When the lateral wellbore assembly5reaches the desired wellbore depth to which it will be adjacent to the target exit window30, the whipstock10may be latched or otherwise coupled and set in the casing string35via setting mechanism40. When the whipstock10is set, the wash pipe20may be decoupled from the guide bar15. The coupling mechanism between the wash pipe20and the guide bar15is designed to be easier to decouple than the coupling mechanism between the guide bar15and the whipstock10. As such, the wash pipe20may be decoupled from the guide bar15without decoupling the guide bar15from the whipstock10. In some examples, the guide bar15may be coupled to the wash pipe20with a severable connection such as shear screws, shear pins, or any such severable coupling mechanism. In other examples, the guide bar15may be coupled to the wash pipe20with an actuatable mechanism such as a hydraulic or pneumatic mechanism. If using an actuatable mechanism, the mechanism may be actuated after the whipstock10has been set in the casing string35.

After the wash pipe20has been decoupled from the guide bar15, the wash pipe20may begin the milling operation. As illustrated in the cross-section ofFIG. 1, a terminal end55of the guide bar15is chamfered and fit within the mill50of the wash pipe20. The chamfer guides the cutting surface45of the mill50and ensures that the wash pipe20slides onto the guide bar15. The cutting surface45of the mill50may rotate with the wash pipe20to begin the milling of the guide bar15. The milling of the guide bar15guides the wash pipe20milling towards the exit window30where it may mill the exit window30in the casing string35.

As the mill50mills the guide bar15, the wash pipe20is guided towards the exit window30where the mill50begins to mill the casing string35. The guide bar15is not decoupled from the whipstock10except as the mill50mills away the guide bar15. Optionally, the guide bar15is offset from the whipstock10to lift the mill50and the wash pipe20away from the whipstock10and thereby further reduce the possibility of contact between the cutting surface45of the mill50and the deflection surface25of the whipstock10. After the exit window10is successfully milled, the washpipe10may be removed if desired.

FIG. 2illustrates an isometric view of the lateral wellbore milling assembly5. As illustrated, the guide bar15is shaped so as to decrease in diameter as it extends from the terminal end adjacent to the mill50down to the opposing terminal end. The tapering of the diameter of the guide bar15allows the guide bar15to be run in the wellbore while adjacent to the whipstock10so that the entirety of the lateral wellbore milling assembly5may be run in the well in one trip.

The guide bar15may comprise any material sufficient for milling with the wash pipe20. Examples of potential guide bar10materials may include, but are not limited to, any metal or metal alloy (e.g., low alloy steel such as American Iron and Steel Institute (AISI) alloys 4140, 4130, etc.) having a material yield strength equal or less than the whipstock material. With the benefit of this disclosure, one of ordinary skill in the art will be readily able to provide a guide bar10sufficient for milling with the wash pipe20.

FIG. 3illustrates a cross-section of the washpipe20that houses the retaining mechanisms for retaining cuttings and debris within the washpipe20. The washpipe20generally comprises a tubular-shaped body60with an annulus65, and inner diameter70, and an outer diameter75. The body60comprises an opening75at the mill50end disposed adjacent to the cutting surface45. Although only one cutting surface45is depicted, additional cutting surfaces disposed around the inner diameter70may be provided in some examples.

The washpipe20further comprises a retaining element80positioned within the body60along a portion of the inner diameter70and uphole of the opening75. Although only one retaining element80is illustrated, it is to be understood that more than one retaining element80may be used in some alternative examples. Optionally, a filter85may be positioned within the body60uphole of the retaining element80and the opening75. When there is no fluid circulation through the annulus65, the retaining element80is closed. When there is fluid circulation through the annulus65, the retaining element is open. As such, the retaining element80closes and entraps cuttings and debris when said cuttings and debris pass uphole of it and fluid circulation is halted thereby closing the retaining element80. The retaining element80may be actuated by spring-loaded, hydraulic, pneumatic, electronic, or other such mechanism sufficient to force the retaining element80into a closed position when fluid circulation is halted. The retaining element80may be used to retain portions or of the casing string (i.e., casing string35as illustrated inFIG. 1) after the mill50of the washpipe20has milled an opening in the exit window and there is no longer any circulation of the fluid through the annulus65of the body60. Moreover, because of the nature of the washpipe20milling, larger-sized cuttings are generated. The larger-sized cuttings are more easily retained within the washpipe20which results in more of the cuttings being retained by the retaining element80. This also results in reduced cleanup and a reduction in the risk of cutting build-up that could potentially interfer with the cutting surface45.

In optional embodiments, the filter85may be used to trap cuttings during operation of washpipe20when there is fluid circulation through the annulus65of the body60. In further optional embodiments, openings90may be disposed within the body60at desired locations to allow fluid circulation therethrough. These openings90may be actuatable to be open and closed in some further optional examples.

It is to be understood that the lateral wellbore milling assembly5and its components as depicted inFIGS. 1-3are only one possible configuration of lateral wellbore milling assembly5. The individual pieces of wellbore equipment may be rearranged as would be readily apparent to one of ordinary skill in the art. As such, it is to be recognized that lateral wellbore milling assembly5is merely exemplary in nature, and various additional configurations may be used that have not necessarily been depicted inFIGS. 1-3in the interest of clarity. Moreover, non-limiting additional components may be present, including, but not limited to, valves, condensers, adapters, joints, gauges, sensors, compressors, pressure controllers, pressure sensors, flow rate controllers, flow rate sensors, temperature sensors, and the like. As such, it should be clearly understood that the example illustrated byFIGS. 1-3is merely a general application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited in any manner to the details ofFIGS. 1-3as described herein.

The lateral wellbore milling assembly5described herein may be used to mill an opening for a lateral wellbore. The opening for the lateral wellbore may be formed by milling and/or drilling through a section of casing string35, the cement liner (if present), and/or the formation.

Referring now toFIG. 4, a cross-sectional view of the lateral wellbore milling assembly5is illustrated as the whipstock10is set within the section of casing string35. The lateral wellbore milling assembly5may be lowered on a drilling string in a wellbore partially lined with the section of casing string35and, optionally, a cement liner. As the lateral wellbore milling assembly5is lowered, it may be rotated before or during engagement with the targeted section of the casing string35adjacent the desired exit window30. When in the desired orientation and depth, the lateral wellbore milling assembly5may be set in place by setting mechanism40which couples the whipstock10to the casing string35. The exit window30may comprise materials more desirable for milling such as aluminum in some examples. In some examples, a pilot hole is not milled before introduction of the lateral wellbore milling assembly5. In other examples, the exit window30is not pre-milled.

With continued reference toFIG. 4, the whip stock10is set in the casing string35via the setting mechanism40described above. Coupling mechanism100maintains the connection between the guide bar15and the whip stock10. Coupling mechanism105maintains the connection between the guide bar15and the wash pipe20.

With reference toFIG. 5, the coupling mechanism105(illustrated inFIG. 4) is severed and the wash pipe20has begun to mill the guide bar15with the mill50portion which comprises the cutting surface45. The coupling mechanism100between the guide bar15and the whipstock10is still intact. The guide bar15is offset from the deflection surface25of the whipstock10. The wash pipe20is rotated and the cutting surface45of the mill50begins to mill the guide bar15. During milling and/or drilling operations, a fluid (e.g., drilling fluid) may be circulated through the wash pipe20. The fluid may carry cuttings110and other debris through the wash pipe20. The fluid may carry the cuttings110past the retaining element80which may catch and retain the cuttings110when fluid circulation is lost in the wash pipe20.

With continued reference toFIG. 5, as the guide bar15is milled by the wash pipe20, the wash pipe20is guided toward the exit window30of the casing string35without the cutting surface45of the wash pipe20contacting the deflection surface25of the whip stock10.

FIG. 6illustrates the wash pipe20as it mills through the portion of casing string35comprising the exit window30. The guide bar15illustrated inFIGS. 4-5has been milled away as the wash pipe20was guided into the exit window30. In some examples, the wash pipe20may mill the casing string35, a cement sleeve (not illustrated), and/or a portion of the adjacent subterranean formation (not illustrated). After the exit window30has been milled the lateral wellbore may be further drilled and completed.

During circulation of the fluid through the wash pipe20, the cuttings110(illustrated inFIG. 5) and other debris may be filtered within the wash pipe20by the filter85described inFIG. 3above. Further, the cuttings110and other debris may be retained within the wash pipe20by the retaining element80when the retaining element80is in the closed position after the fluid stops circulating through the wash pipe20. The cuttings110and other debris may be retrieved from within the wash pipe20when the wash pipe20is removed from the wellbore.

Provided are methods for milling a window for a lateral wellbore in a casing string. An example method comprises introducing a milling assembly into a primary wellbore, the milling assembly comprising: a whipstock, a guide bar coupled to the whipstock, and a wash pipe coupled to the guide bar. The method further comprises running the milling assembly to a depth at which it is adjacent to the window in the casing string; securing the whipstock in the casing string; decoupling the wash pipe from the guide bar; guiding the wash pipe to mill the guide bar without milling the whipstock; and milling the window in the casing string with the wash pipe.

Additionally or alternatively, the method may include one or more of the following features individually or in combination. The wash pipe may be decoupled from the guide bar without decoupling the guide bar from the whipstock. The guide bar may be decoupled from the wash pipe by a severable connection comprising shear pins, shear screws, or a combination thereof. The guide bar may be decoupled from the wash pipe by a acuatable connection comprising hydraulics, penumatics, or a combination thereof. The guide bar may be offset from the whipstock. The guide bar may be coupled to the wash pipe proximate a terminal end of the guide bar, wherein said terminal end of the guide bar is chamfered. The wash pipe may comprise an internal retaining element to retain cuttings. The window may not be pre-milled and may not comprise a pilot hole. The guide bar may comprise a metal or metal alloy having a material yield strength equal or less than the whipstock material.

Provided is a lateral wellbore milling assembly. An example assembly comprises a whipstock, a guide bar coupled to the whipstock, and a wash pipe coupled to the guide bar.

Additionally or alternatively, the assembly may include one or more of the following features individually or in combination. The wash pipe may be decoupled from the guide bar without decoupling the guide bar from the whipstock. The guide bar may be decoupled from the wash pipe by a severable connection comprising shear pins, shear screws, or a combination thereof. The guide bar may be decoupled from the wash pipe by a acuatable connection comprising hydraulics, penumatics, or a combination thereof. The guide bar may be offset from the whipstock. The guide bar may be coupled to the wash pipe proximate a terminal end of the guide bar, wherein said terminal end of the guide bar is chamfered. The wash pipe may comprise an internal retaining element to retain cuttings. The window may not be pre-milled and may not comprise a pilot hole. The guide bar may comprise a metal or metal alloy having a material yield strength equal or less than the whipstock material.

Provided are systems for milling a window for a lateral wellbore in a casing string. An example system comprises a milling assembly comprising: a whipstock, a guide bar coupled to the whipstock, and a wash pipe coupled to the guide bar. The system further comprises a casing string having the milling assembly disposed therein, wherein the casing string comprises a window adjacent the milling assembly.

Additionally or alternatively, the system may include one or more of the following features individually or in combination. The wash pipe may be decoupled from the guide bar without decoupling the guide bar from the whipstock. The guide bar may be decoupled from the wash pipe by a severable connection comprising shear pins, shear screws, or a combination thereof. The guide bar may be decoupled from the wash pipe by a acuatable connection comprising hydraulics, penumatics, or a combination thereof. The guide bar may be offset from the whipstock. The guide bar may be coupled to the wash pipe proximate a terminal end of the guide bar, wherein said terminal end of the guide bar is chamfered. The wash pipe may comprise an internal retaining element to retain cuttings. The window may not be pre-milled and may not comprise a pilot hole. The guide bar may comprise a metal or metal alloy having a material yield strength equal or less than the whipstock material.

One or more illustrative examples incorporating the examples disclosed herein are presented. Not all features of a physical implementation are described or shown in this application for the sake of clarity. Therefore, the disclosed systems and methods are well adapted to attain the ends and advantages mentioned, as well as those that are inherent therein. The particular examples disclosed above are illustrative only, as the teachings of the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown other than as described in the claims below. It is therefore evident that the particular illustrative examples disclosed above may be altered, combined, or modified, and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein.