Completion methodology for unconventional well applications using multiple entry sleeves and biodegradable diverting agents

A heel-to-toe method and system for horizontal well treatments incorporates use of frac ball and sleeve in conjunction with biodegradable diverting agents.

BACKGROUND OF THE INVENTION

1. Field of Technology

Unconventional/horizontal wells may be stimulated using plug-and-perf methods and ball-activated frac sleeves methods. These two methodologies are alternatives to one another and each comes with its own costs and benefits.

2. Background of Invention

During either multi-stage plug-and-perf or multi-stage frac sleeve completion methods, reservoir entry points placed in treatment stages in the well may not be fully stimulated and/or uniformly broken down. As a result, the reservoir entry points treated by these methods remain under-stimulated.

The aforementioned illustrative representations inFIGS. 1 through 5should be understood to be interrelated, and their components, methods of operation, and results may be interchangeable.

DETAILED DESCRIPTION

The following description provides details of particular embodiments of the invention and is not intended to be exhaustive or limited to the invention in the form disclosed. The described embodiments are intended to explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand and practice the claimed invention. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The scope of the claims may be intended to broadly cover the disclosed embodiments and any such modifications.

As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise be. It will be further understood that the terms “comprise” and/or “comprising,” when used in this specification and/or the claims, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.

The disclosed embodiments and additional advantages thereof are best understood by referring toFIGS. 1-5of the drawings, like numerals being used for like and corresponding parts of the various drawings. Other features and advantages of the disclosed embodiments will be or will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It may be intended that all such additional features and advantages be included within the scope of the disclosed embodiments. Further, 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 embodiments may be implemented.

In the illustrative embodiment ofFIG. 1, an exemplary work site10may operate over a production string11in a subterranean formation5below the surface S. In the production string11, a string or series of strings13, which may comprise one or more layers of a composite (e.g., cement), a metal (e.g., steel), conductive casing, and/or casing packers, may be placed to allow for drilling, fracturing, and other well-operations known to those skilled in the art. In a substantially horizontal portion of a well, which may be formed by means and methods known to those skilled in the art, e.g., plug-and-perf type completions, frac sleeve completions, a constructed lateral wellbore section12may comprise one or more frac sleeves located through the horizontal well length. The specific area of the well that may be treated is referred to as a “stage” or “zone” in the well. In an exemplary horizontal well, the horizontal well may have a heel “H” and a toe “T” between which multiple frac sleeves may be located to provide entry points to the reservoir. An exemplary frac sleeve may be comprised of a fixed outer housing15and an inner shiftable sleeve16. An exemplary frac sleeve may use a combination of graduated ball and baffle sizes to allow the inner sleeve to shift to an “open” position to allow for fluid to flow out of the wellbore and into the formation. These sliding sleeves can be used in conjunction with the next adjacent frac sleeve to provide a conduit for received fluids, e.g., F, to flow into the reservoir at multiple entry points simultaneously. It should be apparent to one skilled in the art, that this is just one variation of a subterranean oilfield tool that can provide entry points from the inner casing to the reservoir.

For example, in plug-and-perf completion method, a bottom-hole assembly (BHA) consisting of a frac plug and perforating gun(s) may be pumped downhole using wireline deployment methods known to those skilled in the art. The plug may be set using a setting tool that may be activated via electrical signal sent down the wire/e-line. Once set, the BHA may be moved up-hole to the desired location and the perforating gun may be fired to perforate the tubular casing/production. The BHA may be pulled out of hole (POOH) and then a proppant-laden fluid and/or other appropriate treatment fluid, F, may be pumped downhole to fracture and stimulate the formation5. The fluid may be pumped out the perforations at high rates.

In an exemplary frac sleeve completion method, a fixed outer housing of the frac sleeve15may comprise one or more reservoir entry ports15alocated about the outer housing of the frac sleeve. In an exemplary embodiment, reservoir entry ports15amay operate as a multiple entry sleeve (MES) for a frac sleeve system in which they are found. Alternatively, an exemplary inner shiftable sleeve16may comprise one or more reservoir entry ports16alocated about the inner shiftable sleeve16. In an exemplary embodiment, reservoir entry ports16amay operate as an MES for a frac sleeve in which they are found. In combination the reservoir entry ports15aand16aof the outer housing and inner shiftable sleeves, respectively, may work together to serve as an MES. Those skilled in the art would understand that a multi-entry frac sleeve may be interchanged with a frac sleeve or other comparable subterranean frac tools known to one skilled in the art.

Those skilled in the art would also be familiar with frac sleeve completions, including those which make use of an inner stage sleeve16and a baffle17for catching and dampening movement of a ball14. The seating of ball14on baffle17may restrict the ability of fluid F allow flow14throughout the length of the production string12by way of obstructing the pathway of the fluid through the baffle17, by abutting a stop18, which may be a mechanical construct found on outer stage sleeve15or be part of a separate component that interacts with the frac sleeve (e.g., the next adjacent frac sleeve).

In the illustrative embodiment ofFIG. 2, a ball14may engage a baffle17affixed to the inner sliding sleeve of the frac sleeve16, thereby sliding the inner sleeve to align the reservoir entry points16awith the reservoir entry points15aof the outer sleeve housing15. In an exemplary embodiment, alignment of reservoir entry points16aand15amay allow fluid F to pass from the inside of the production casing and into the formation5to create fractures30having fracture openings31aand31b, and propagation regions32a. In an exemplary embodiment, use of frac sleeve may create numerous fractures30about the circumference of the frac sleeve. As illustrated, ball14has landed in its position in baffle17while fluid F is used to propagate fractures30in the formation5. Ball14may not move until baffle17yields to the force of fluid F against ball14. An exemplary baffle17may yield in plastic deformation, open in response to pressure changes, or hinge/latch/slide/rotate parts and/or components, or by an alternative mechanical/physical means to allow passage of ball14to the next part of the production string.

In the illustrative embodiment ofFIG. 3, ball14may be propelled by fluid F past one baffle17of an inner sliding sleeve16of a frac sleeve and into the next inner sliding sleeve16of the adjacent frac sleeve. As ball14displaces inner sliding sleeves16so that their reservoir entry points16aalign with the corresponding reservoir entry points15aof outer sleeve housing15, fluid F exits there through to create additional fractures30in formation5. Fluid streams F1may therefore create a fracture30having fracture propagations32awhile fluid stream F2may create a fracture30having fracture propagations32b. Adjacent the reservoir entry ports15a/16aof an exemplary frac sleeve a fracture opening31a,31b,31c, and31dmay grow and expand into the formation5to allow expulsion of fluids otherwise trapped thereinAs multiple frac sleeves are opened, the ball14may stall due to the lack of rate as fluid streams F1and F2are primarily flowing into the reservoir. As ball14progresses deeper into the horizontal well, the pressure and amount of fluid necessary to cause sufficient stimulation of formation5may increase and, therefore, less pressure will be available in the fluid F to cause ball14to progress further through the production string12.

In the illustrative embodiment ofFIG. 4, a biodegradable diverting agent (BDA)20may be introduced into the well bore in the stream of fluid F so as to enter into and bridge off flow to the initiated fractures and/or openings in the frac sleeves that are present after the alignment of the reservoir entry ports15aand16aof the outer frac sleeve housing15and inner shiftable sleeve16, respectively. BDA particles21may be shown to obstruct the inner stage sleeve16at reservoir entry ports16a. Alternatively or additionally, BDA particles22may obstruct the entry ports15aof outer stage sleeve15. Alternatively or additionally, BDA particles22may also obstruct fluid F passage into fracture opening31a. In an exemplary embodiment, BDA may be flowed into the openings with the fluid treatment flow into the fracture, where it is compacted and held in place by the differential pressure that exists between the wellbore and the reservoir and fracture. The BDA is of any type known to those skilled in the art.

As further illustrated inFIG. 4, BDA may be used to close off fluid F passage to a substantially empty fracture35, e.g., a fracture that is completely or substantially stimulated. By limiting points of egress for fluid F, BDA prevents loss of pressure in the fluid F to these regions, thereby allowing for increased pressure flows, F2+, at adjacent fractures40, or increased pressures on ball14, flow F+. Adjacent fractures40may grow as compared to their preexisting state, e.g., as a fracture30, due to higher pressure fluid, e.g., F2+, at the fracture entry31c. By using BDA as described, the frac sleeve may further stimulate already existing fractures in the formation5, or, as may be illustrated inFIG. 5, stimulate new fractures further downstream (see fluid stream F3stimulating new fracture40). Thus, the use of BDA in combination with frac sleeves as illustrated may result in increased and/or substantially complete fracture propagation and well treatment while ensuring ball14does not stall in response to losses in rate into the formation5.

The disclosed treatment methodology may allow for increased number of frac sleeves used in a horizontal well due to the fact that a single ball could be utilized for each sleeve while using a BDA to keep the ball from stalling as the ball is pumped through the sleeves. Once a frac sleeve would be installed in the casing/production string as designed, one ball and baffle size may be used throughout the entire length of the wellbore.

In accordance with disclosed embodiments, a well may be treated heel-to-toe instead of the traditional toe-to-heel. Ball14may be dropped from surface S and pumped down to activate the first frac sleeves in the wellbore11. As the frac sleeves are opened, the flowrate pumping the ball14down will decrease due to fluid F being pumped out into the formation5. Once this occurs, ball14will stall. Upon completion of a fracturing treatment sequence, the BDA20can be pumped into the well11. The BDA may serve to more effectively stimulate the wellbore, plug off the treatment ports (e.g., reservoir entry points15a/16a, fracture entries31a,31b,31c,31d), and/or allow fluid to continue to push ball14downhole to activate subsequent frac sleeves until flowrate F diminishes and ball14stalls again. This process may be repeated until the entire wellbore has been stimulated and all of the frac sleeves have been opened. Once all frac sleeves have been opened, and since only one baffle and ball size may be used, the wellbore may not require coiled tubing to mill out baffles of descending sizes. Additionally and alternatively, utilizing a dissolvable ball14may allow for a completely intervention-less completion method.

While the disclosed embodiments may be amenable to being used as a one-ball-and-baffle frac sleeve/heel-to-toe type of application, it is also contemplated that the disclosed embodiments may be used to break the wellbore into large segments of the same ball/baffle sleeve and treated in a more traditional toe-to-heel method. For example, a plurality of horizontal well portions may be divided and completed using sets of frac sleeves, that utilize the aforementioned ball and baffle system. For example, a horizontal portion of a well may be 8,000 ft, which may be broken into four 2,000 ft. segments. A first 2000 ft. segment may be the portion at the toe of the well and may have the smallest ball and baffle combination of the four segments (although, the baffle inner diameter (ID) may still be a large baffle ID to minimize wellbore restrictions). In accordance with the disclosed embodiments, the first 2000 ft. segment may be completed using the MES/BDA methodology to activate all of the sleeves located in that segment of the well. Once that segment was completed, a different size ball and baffle sleeve could be used to stimulate the next 2,000 ft. segment of the horizontal well in the same manner.

A method for completion of a horizontal well in a subterranean formation, the horizontal well having a heel and a toe, may comprise the steps of: pumping fluid into a first frac sleeve proximal to the heel of the horizontal well, pumping fluid through at least one opening in the first frac sleeve into contact with the formation, providing a BDA to interact with the at least one opening in the first frac sleeve, restricting the fluid from flowing into the at least one opening in the first frac sleeve after the BDA interacts with the at least one opening in the first frac sleeve, and pumping fluid into a second frac sleeve more proximal to the toe of the horizontal well than the first frac sleeve. Such a method may further include fracturing the formation in a second stage located distal to the heel and proximal to the toe of the horizontal well, and pumping fluid into a second frac sleeve more proximal to the toe of the horizontal well than the first frac sleeve, pumping fluid against a ball traversing the inside of the second frac sleeve, pumping fluid against a ball to permit fluid through the at least one opening into contact with the formation, and pumping fluid into a second frac sleeve more proximal to the toe of the horizontal well than the first frac sleeve, and/or propelling a ball disposed within the first frac sleeve that is stalled following a fracture in the formation adjacent the at least one opening in the first frac sleeve. Alternatively and additionally, where a ball disposed within the first frac sleeve stalls following a fracture in the formation adjacent the at least one opening in the first frac sleeve, the ball may be pumped through the second frac sleeve after the BDA interacts with the at least one opening in the first frac sleeve.

In any of the foregoing methods, the first frac sleeve may be directly or indirectly coupled to the second frac sleeve, one of the first frac sleeve and the second frac sleeve is an MES, and/or both the first frac sleeve and second frac sleeve is an MES.

A system for horizontal well completion comprises: a plurality of frac sleeves arranged in a horizontal well, the horizontal well having a heel and a toe and being located in a subterranean formation, a BDA disposed on at least one of the plurality of frac sleeves at a location more proximal to the heel of the horizontal well and disposed proximal to a fracture in the formation, and a ball disposed within at least one of the plurality of frac sleeves and separating the BDA from the terminal portion of the horizontal well.

A system for horizontal well completion that comprises: a plurality of frac sleeves arranged in a horizontal well, the horizontal well having a heel and a toe and being located in a subterranean formation, a BDA disposed on at least one of the plurality of frac sleeves at a location more proximal to the heel of the horizontal well and disposed proximal to a fracture in the formation, and a ball disposed within at least one of the plurality of frac sleeves and separating the BDA from the terminal portion of the horizontal well, may also comprise at least one of the plurality of frac sleeves being a multiple entry sleeve, each of the plurality of frac sleeves being a multiple entry sleeve, a dissolvable ball, and/or each of the plurality of frac sleeves have substantially the same inner diameter.

A system for horizontal well completion that comprises: a plurality of frac sleeves arranged in a horizontal well, the horizontal well having a heel and a toe and being located in a subterranean formation, a BDA disposed on at least one of the plurality of frac sleeves at a location more proximal to the heel of the horizontal well and disposed proximal to a fracture in the formation, and a ball disposed within at least one of the plurality of frac sleeves and separating the BDA from the terminal portion of the horizontal well, may also comprise at least one of the plurality of frac sleeves being a multiple entry sleeve, each of the plurality of frac sleeves being a multiple entry sleeve, a dissolvable ball, and/or each of the plurality of frac sleeves have substantially the same inner diameter. Such a system may also comprise a substantially completed fracture proximal to the BDA, a further fracture in the formation distal to the location of the BDA and proximal to and before the ball that may be substantially completed.

The above detailed description may be of a small number of embodiments for implementing the invention and may be not intended to limit the scope of the following claims.