Fluid flow control during well treatment

A method can include positioning a flow restrictor in a wellbore that penetrates a formation interval, then displacing the flow restrictor along the wellbore away from the surface, thereby permitting flow into an interval section from a wellbore section between the flow restrictor and the surface, blocking the flow from the wellbore section into the interval section, and displacing the flow restrictor away from the surface, thereby permitting flow from the wellbore section into another interval section farther along the wellbore from the surface. A system can include a flow restrictor that restricts flow through an annulus surrounding the flow restrictor, and plugging devices disposed in a wellbore section positioned between the flow restrictor and a surface of the well. Flow from the wellbore section into a formation interval section is permitted prior to being blocked by the plugging devices.

BACKGROUND

This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in examples described below, more particularly provides for controlling fluid flow during well treatment operations.

In well treatment operations, fluids, gels, slurries, proppant, etc., may be flowed from a wellbore into an earth formation. The treatment of the earth formation is typically most effective if the treatment is performed uniformly across a desired interval along the wellbore.

Therefore, it will be appreciated that improvements are continually needed in the art of treating earth formations. These improvements can result in enhanced uniformity of treatment or control over the treatment (in some circumstances it may be desired to treat one section of an interval more extensively than another section of the interval).

DETAILED DESCRIPTION

Representatively illustrated inFIGS.1-6is a well treatment system10for use with a subterranean well, and an associated method, which can embody principles of this disclosure. However, it should be clearly understood that the system10and method are merely one example of an 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 at all to the details of the system10and method described herein and/or depicted in the drawings.

In the example depicted inFIG.1, a wellbore12extends through an earth formation zone or interval14penetrated by the wellbore. The wellbore12is generally vertical, but in other examples the wellbore could be horizontal or otherwise inclined from vertical, and different sections of the wellbore could have respective different orientations.

The wellbore12as depicted inFIG.1is lined with casing16and cement18. In other examples, the wellbore12may not be lined, cased or cemented in the interval14. The casing16may be any type of wellbore lining, such as, liner, casing, tubing or other types of tubulars.

Perforations20extend outward through the casing16and cement18, and into an earth formation22. The perforations20provide for fluid communication between the formation22and the wellbore12(in this example, an interior flow passage24of the casing16). If the wellbore12is not lined with casing16, then the formation22can be in fluid communication with the wellbore12without use of the perforations20.

The methods described herein can be used with various types of treatment operations, including but not limited to matrix treatment (such as matrix acidizing, conformance treatment, permeability modifying, etc.), fracturing and re-fracturing the formation22. The methods can be especially advantageous in situations where the interval14is relatively long and/or sufficient pumping capacity is not available to perform the treatment on the entire interval at the same time.

It will be appreciated by those skilled in the art that, in the case of a relatively long interval, a small number of the perforations20may take an inordinately large proportion of fluid flow during the treatment, which can cause problems, such as, lack of sufficient flow into other perforations (thereby hindering effective treatment of the entire interval), sanding-out (if fracturing or re-fracturing), etc. Thus, in methods described herein, the interval14is divided into multiple sections14a-c, which are individually treated, so that the entire interval14is effectively treated. In theFIGS.1-6example, the interval14is divided into three sections14a-c, but in other examples other numbers of sections may be used.

Referring additionally now toFIG.2, a downhole tool assembly26has been conveyed into the wellbore12. A conveyance28(such as, a wireline, slick line, e-line, coiled tubing, etc.) is secured to a flow restrictor30. Additional, fewer or different tools may be included in the tool assembly26in keeping with the principles of this disclosure.

The tool assembly26may be lowered into the wellbore12using the conveyance28and/or flow of a fluid32through the wellbore may be used to “push” the tool assembly along the wellbore. In other examples, a tractor device could be included in the tool assembly26to displace the tool assembly through the wellbore12. Thus, the scope of this disclosure is not limited to any particular means of conveying the tool assembly26into or through the wellbore12.

The flow restrictor30is configured such that a pressure differential is created across the flow restrictor in response to the flow of the fluid32or application of fluid pressure to the wellbore12between the flow restrictor and the surface (e.g., at or near the earth's surface, such as, at a land- or water-based well site). For example, the flow restrictor30may have an outer diameter that is a close sliding fit in an inner diameter of the casing16, so that flow through an annulus formed between the flow restrictor and the casing is significantly restricted, thereby causing pressure in the wellbore12between the flow restrictor and the surface (on an uphole side of the flow restrictor) to increase relative to pressure in the wellbore on an opposite downhole side of the flow restrictor. As another example, the flow restrictor30may sealingly engage the inner diameter of the casing16, thereby preventing flow through the annulus between the casing and the flow restrictor, so that pressure applied to the wellbore12between the flow restrictor and the surface results in the pressure differential being created across the flow restrictor.

The pressure differential across the flow restrictor30may be used to convey the tool assembly26through the wellbore12. The conveyance28may be used to limit displacement of the tool assembly26, so that it is eventually conveyed to a desired position in the wellbore12. Thus, the conveyance28can exert a force on the flow restrictor30that is directed opposite to a force due to the pressure differential across the flow restrictor, in order to control a position of the flow restrictor along the wellbore12.

As depicted inFIG.2, the flow restrictor30is positioned in the wellbore12between the interval section14aand the interval section14b. The fluid32flows into the wellbore12between the flow restrictor30and the surface. If the flow restrictor30does not seal against the casing16, some of the fluid32may flow into the wellbore12below the flow restrictor. However, a substantial majority of the fluid32preferably flows into the interval section14a, whereby the interval section is treated (e.g., matrix treatment, fracturing, re-fracturing, etc.).

The same fluid32may be used to convey the tool assembly26through the wellbore12and to treat the interval section14a. Alternatively, different fluids may be used to convey the tool assembly26and to treat the interval section14a. Note, however, that it is not necessary for any fluid to be used to convey the tool assembly26through the wellbore12since, as discussed above, other means may be used to convey the tool assembly.

Referring additionally now toFIG.3, at or near a conclusion of the interval section14atreatment, diverters or plugging devices34are used to prevent flow from the wellbore12into the interval section14a. In this example, individual plugging devices34sealingly engage and prevent flow through the perforations20. In other examples, diverter in the form of particulate matter (such as, calcium carbonate, poly-lactic acid, poly-glycolic acid, etc.) may be used to prevent flow through the perforations20(or into a wall of the wellbore12if the wellbore is uncased). As used herein, the term “plugging device” is considered to include a diverter that prevents flow from a wellbore into an earth formation.

The diverter or plugging devices34may be conveyed through the wellbore12by the flow of the fluid32(or another fluid). The diverter or plugging devices34may be released into the wellbore12at the surface, or they may be released from a container or dispensing device that is part of the tool assembly26, or they may be otherwise included or conveyed with the tool assembly as described more fully below. Thus, the scope of this disclosure is not limited to any particular means for displacing the diverter or plugging devices34into the wellbore12above the flow restrictor30.

In some examples, the diverter or plugging devices34may be degradable downhole. In this manner, after the entire interval14has been treated, the diverter or plugging devices34can eventually degrade (e.g., dissolve, disintegrate, melt, corrode, etc.) and thereby re-establish fluid communication between the formation22and the flow passage24. The diverter or plugging devices34may degrade due to contact with a particular degrading substance (such as acid or a fluid having a particular pH range), passage of time, exposure to heat or radiation, etc.

However, it is not necessary for the diverter or plugging devices34to degrade in keeping with the principles of this disclosure. For example, the diverter or plugging devices34could be dislodged from the perforations20or from a wall of the wellbore12by production flow from the formation22or by mechanical means (such as, a casing scraper or reamer, etc.).

The plugging devices34may be similar to, or the same as, any of the plugging devices described in US Publication Nos. 2016/0319628, 2017/0260828 and 2018/0163504, the entire disclosures of which are incorporated herein by this reference.

Referring additionally now toFIGS.4&5, the steps described above for treatment of the interval section14aare essentially repeated for treatment of the interval section14b. As depicted inFIG.4, the flow restrictor30is displaced to a position between the interval sections14b,cand the fluid32is flowed into the interval section14bto treat the interval section14b.

The fluid32that may be used to displace the flow restrictor30to the position between the interval sections14b,cor to treat the interval section14bis not necessarily the same fluid as used to displace the flow restrictor to the position between the interval sections14a,b, or the same fluid as used to treat the interval section14a. Different fluids may be used in any of the respective different steps of the method described herein.

Note that the previously placed diverter or plugging devices34prevent flow of the fluid32into the interval section14awhile the interval section14bis being treated. Thus, all (or substantially all, if some of the fluid is permitted to flow through the annulus between the flow restrictor30and the casing16) of the fluid32flows into the interval section14b, and not into the interval section14aor the interval section14c(although a small amount of the fluid may flow into the interval section14cif some of the fluid is permitted to flow through the annulus between the flow restrictor30and the casing16).

InFIG.5, additional diverter or plugging devices34are used to block flow through the perforations20at or near conclusion of the treatment of the interval section14b. The diverter or plugging devices34used to prevent flow into the interval section14bmay be the same as, or different from, the diverter or plugging devices34used to prevent flow into the interval section14a.

Referring additionally now toFIG.6, the steps described above for treatment of the interval sections14a,bare essentially repeated for treatment of the interval section14c, except that diverter or plugging devices34are not used to prevent flow of fluid into the interval section14cafter treatment of the interval section14c(since it is the only remaining interval section to be treated). However, if additional interval sections were to be treated, then diverter or plugging devices34could be used to prevent flow of fluid into the interval section14cafter treatment of the interval section14c.

As depicted inFIG.6, the flow restrictor30is displaced to a position below the interval section14cand the fluid32is flowed into the interval section14cto treat the interval section14c. The fluid32that may be used to displace the flow restrictor30to the position below the interval section14cor to treat the interval section14cis not necessarily the same fluid as previously used to displace the flow restrictor, or the same fluid as used to treat either of the interval sections14a,b.

Note that the previously placed diverter or plugging devices34prevent flow of the fluid32into the interval sections14a,bwhile the interval section14cis being treated. Thus, all (or substantially all, if some of the fluid is permitted to flow through the annulus between the flow restrictor30and the casing16) of the fluid32flows into the interval section14c, and not into the interval sections14a,b.

After all of the interval sections14a-chave been treated, the tool assembly26may be retrieved from the wellbore12. Alternatively, the conveyance28may be separated from the flow restrictor30, so that the conveyance may be retrieved from the wellbore12and the flow restrictor can remain in the wellbore. The flow restrictor30could be made of a material (such as aluminum or poly-lactic acid, etc.) that will eventually degrade in the wellbore12.

The diverter or plugging devices34may eventually degrade to thereby permit unrestricted fluid communication from the interval sections14a,bto the flow passage24. Alternatively, the plugging devices34may be mechanically removed, or they may be displaced by production flow from the interval sections14a,binto the wellbore12.

Referring additionally now toFIG.7, a more detailed representative example of the tool assembly26is depicted in the casing16and connected to the conveyance28. In this example, the conveyance28is a wireline or slick line connected to the remainder of the tool assembly26using a cable head36of the type known to those skilled in the art.

The cable head36is connected (such as, by threading) to an elongated mandrel38. The mandrel38is, in turn, connected to the flow restrictor30. In this example, shear pins40are used to releasably secure the flow restrictor30to the mandrel38. In this manner, the conveyance28, cable head36and mandrel38can be retrieved from the wellbore12separately from the flow restrictor30(for example, in the event that the flow restrictor becomes stuck in the casing16).

In theFIG.7example, the flow restrictor30does not sealingly engage the inner diameter of the casing16. Instead, an outer diameter of the flow restrictor30is a close sliding fit within the inner diameter of the casing16, so that fluid flow through an annulus52between the flow restrictor and the casing (seeFIG.7A) is significantly restricted. However, the flow restrictor30could seal against the inner diameter of the casing16in other examples.

A body of the flow restrictor30example ofFIG.7comprises oppositely facing truncated cones. In other examples, other shapes may be used, and the body may be configured or provided with appropriate structures (such as, tortuous passages, flow obstructions, etc.) configured to increase the restriction to fluid flow through the annulus52between the flow restrictor30and the casing16.

Referring additionally now toFIG.8, another example of the tool assembly26is representatively illustrated. In this example, the mandrel38is in tubular form, with ports42formed through side walls of the mandrel, in order to allow the fluid32to flow through an interior of the mandrel.

A plugging device retainer44is connected between upper and lower sections of the mandrel38. The retainer44prevents plugging devices34from displacing downward to the flow restrictor30. Thus, the plugging devices34can be conveyed with the tool assembly26through the wellbore12.

The plugging devices34will engage open perforations20above the retainer44(in the presence of fluid32flow) and, as the tool assembly26is conveyed downward through the wellbore12, the plugging devices will engage additional open perforations as the retainer displaces past the open perforations. The retainer44may be degradable in the well.

Note that it is not necessary for the plugging devices34to be positioned above the retainer44when the tool assembly26is deployed into the wellbore12. In some examples, the plugging devices34could be introduced into the wellbore12above the tool assembly26after the tool assembly is deployed into the wellbore. For example, the plugging devices34could be introduced into the wellbore12above the tool assembly26after each of the interval sections14a,bis treated, or near the conclusion of each interval section treatment.

The tubular mandrel38and the ports42provide for pressure equalization in the wellbore12across the retainer44and any plugging devices34that may accumulate in the wellbore above the retainer. The retainer44may comprise a screen or another structure (such as, similar to a bow-spring type centralizer or an umbrella) capable of preventing the plugging devices34from displacing downward to the flow restrictor30. The retainer44can (but does not necessarily) retain an excess number of the plugging devices34(greater than the number of open perforations20) above the retainer, and can maintain open perforations20between the retainer and the flow restrictor30.

The flow restrictor30in this example includes a resilient or deformable seal element46that sealingly engages the inner diameter of the casing16. A spring or other biasing device48may be used to maintain longitudinal compression of the seal element46, so that the seal element is continuously biased radially outward into engagement with the casing. The seal element46can also deflect radially inward, for example, to pass through reduced inner diameters, obstructions, etc., as needed.

Note that the cable head36is connected to the upper mandrel38using the shear pins40in this example. Thus, the conveyance28and the cable head36can be retrieved from the wellbore12separately from the remainder of the tool assembly26(which may eventually degrade in the wellbore), if needed.

Referring additionally now toFIG.9, another example of the tool assembly26as used in the system10is representatively illustrated. In this example, the steps of the method may be performed concurrently and continuously.

As depicted inFIG.9, the tool assembly26includes two flow restrictors30spaced apart by the tubular mandrel38. The flow restrictors30may be the same as, or similar to, any of the flow restrictors described herein. The conveyance28in this example is of the type known to those skilled in the art as coiled tubing, although other types of tubulars may be used in other examples.

A fluid32ais pumped into an annulus50formed between the casing16inner diameter and the conveyance28in order to displace the tool assembly26along the wellbore. A fluid32bis pumped through an interior of the conveyance28to the tool assembly26.

The fluid32bis a treatment fluid and may be the same as, or different from, the fluid32a. The fluid32bexits the mandrel38via the ports42and flows into the perforations20between the flow restrictors30(or into a wall of the wellbore12if it is uncased).

Different fluids may be used in respective different steps of the method, or the same fluids may be used in all of the steps of the method. The fluids32a,b(or either of them) may be the same as, or different from, the fluid32described above.

As depicted inFIG.9, the fluid32ais being used to displace the tool assembly26along the wellbore12, and the fluid32bis being used to treat the interval section14bbetween the flow restrictors30. The interval section14ahas already been treated, and plugging devices34are being used to block flow into perforations20extending into the interval section14a. The plugging devices34are conveyed in the annulus50to the perforations20above the upper flow restrictor30by the flow of the fluid32a. The interval section14cwill be treated when the tool assembly26is displaced further through the wellbore12.

However, it should be understood that the interval sections14a-care not necessarily separately or individually treated using theFIG.9method. Instead, the interval sections14a-ccan be gradually and continuously treated as the tool assembly26displaces along the wellbore12.

The plugging devices34may be continuously deployed into the annulus50, so that they engage or otherwise block flow into the perforations20above the upper flow restrictor30as it displaces along the wellbore12. Alternatively, a sufficient number or volume of diverter or plugging devices34could initially be disposed in the annulus50above the upper flow restrictor30prior to the treatment operation. The retainer44described above may be used to prevent the diverter or plugging devices34from contacting the upper flow restrictor30.

In some examples, the interval sections14a-ccould be separately treated by displacing the tool assembly26so that the flow restrictors30straddle the perforations20of each interval section in succession. In this manner, greater control over treatment pressures and flow rates may be obtained for each of the individual interval sections14a-c, if desired.

In the examples described above, the tool assembly26is described as being displaced along the wellbore12by flow of the fluid32or32ainto the wellbore above the tool assembly. Alternatives, such as, use of a tractor device or use of the conveyance28to push or pull the tool assembly26along the wellbore12are also described. In another alternative, a weight of the tool assembly26and/or the conveyance28may be sufficient to displace the tool assembly along the wellbore12. Thus, the scope of this disclosure is not limited to any particular means of displacing the tool assembly26along the wellbore12.

It may now be fully appreciated that the above disclosure provides to the art a well treatment system10and method, in which a first flow restrictor30is positioned in a wellbore12below a first interval section14ato be treated, the first interval section14ais treated by flowing a fluid32into the first interval section14a, diverter or plugging devices34are used to block flow of the fluid32into the first interval section14a, and then the first flow restrictor30is positioned in the wellbore12below a second interval section14bto be treated.

The second interval section14bis treated by flowing a fluid32into the second interval section14b, and diverter or plugging devices34may be used to block flow of the fluid32into the second interval section14b.

The fluid32may be used to displace the first flow restrictor30along the wellbore12.

The first flow restrictor30may be included in a tool assembly26secured to a conveyance28that limits displacement of the tool assembly26along the wellbore12.

The tool assembly26in one example includes a second flow restrictor30longitudinally spaced apart from the first flow restrictor30. The fluid32bis flowed into the first interval section14astraddled by the first and second flow restrictors30in this example.

The first interval section14aand a second interval section14bmay be treated while the tool assembly26displaces along the wellbore12.

The first flow restrictor30may restrict or prevent flow of the fluid32through an annulus52formed between the first flow restrictor30and an inner diameter of the wellbore12.

The diverter or plugging devices34may be conveyed along the wellbore12with a tool assembly26that includes the first flow restrictor30, such as, above a retainer44of the tool assembly26.

The above disclosure provides to the art a method of treating a subterranean well. In one example, the method can include: positioning a first flow restrictor30in a wellbore12that penetrates an interval14of an earth formation22; then displacing the first flow restrictor30along the wellbore12away from a surface of the well, thereby permitting flow into a first section14aof the interval14from a section of the wellbore12between the first flow restrictor30and the surface; blocking the flow from the wellbore12section into the first interval section14a; and displacing the first flow restrictor30along the wellbore12away from the surface of the well, thereby permitting unrestricted flow from the wellbore12section into a second section14bof the interval14. The second interval section14bis farther along the wellbore12from the surface than the first interval section14a.

In any of the examples described herein:

The step of permitting flow into the first section14aof the interval14may include the first flow restrictor30restricting fluid32flow from the wellbore12section into the second interval section14b.

The blocking step may include plugging devices34preventing the flow into the first interval section14a.

The plugging devices34may be disposed in the wellbore12section during the step of permitting flow into the first section14aof the interval14.

The plugging devices34may be released into the wellbore12section after the step of permitting flow into the first section14aof the interval14and prior to the step of permitting unrestricted flow from the wellbore12section into the second section14bof the interval14.

The first flow restrictor30may be positioned between the first and second interval sections14a,bduring the step of permitting flow into the first section14aof the interval14and prior to the step of permitting unrestricted flow from the wellbore12section into the second section14bof the interval14.

The second interval section14bmay be positioned between the first interval section14aand the first flow restrictor30during the step of permitting unrestricted flow from the wellbore12section into the second section14bof the interval14.

The step of displacing the first flow restrictor30along the wellbore12away from the surface of the well, thereby permitting unrestricted flow from the wellbore12section into the second section14bof the interval14, may include displacing the first flow restrictor30by the flow.

The first flow restrictor30may be included in a tool assembly26secured to a conveyance28that limits displacement of the tool assembly26along the wellbore12.

The tool assembly26may include a second flow restrictor30longitudinally spaced apart from the first flow restrictor30. The step of permitting flow into the first section14aof the interval14may include permitting flow into the first interval section14afrom the wellbore12between the first and second flow restrictors30.

The tool assembly26may displace along the wellbore12during the step of permitting flow into the first section14aof the interval14.

The first flow restrictor30may restrict or prevent flow through an annulus52surrounding the first flow restrictor30. The annulus52may be formed between the first flow restrictor30and an inner surface of the wellbore12.

The plugging devices34may be conveyed along the wellbore12with a tool assembly26that includes the first flow restrictor30during the step of permitting flow into the first section14aof the interval14.

A system10for treating a subterranean well is also provided to the art by the above disclosure. In one example, the system10can include a first flow restrictor30that restricts flow through an annulus52surrounding the flow restrictor30, and plugging devices34disposed in a section of a wellbore12positioned between the first flow restrictor30and a surface of the well. Flow from the wellbore12section into a first section14aof an interval14of an earth formation22is permitted prior to being blocked by the plugging devices34.

In any of the examples described herein:

The first flow restrictor30may be connected to a conveyance28that restricts displacement of the first flow restrictor30along the wellbore12. The displacement may be due to a pressure differential across the first flow restrictor30.

Displacement of the first flow restrictor30along the wellbore12away from the surface of the well may permit unrestricted flow from the wellbore12section into a second section14bof the interval14.

The second interval section14bmay be farther along the wellbore12from the surface than the first interval section14a.

The first flow restrictor30may restrict flow from the wellbore12section into the second interval section14b.

The plugging devices34may be released into the wellbore12section after flow is permitted into the first interval section14aand prior to unrestricted flow being permitted from the wellbore12section into the second interval section14b.

The first flow restrictor30may be positioned between the first and second interval sections14a,bwhile flow is permitted into the first interval section14aand prior to unrestricted flow being permitted from the wellbore12section into the second interval section14b.

The second interval section14bmay be positioned between the first interval section14aand the first flow restrictor30when unrestricted flow is permitted from the wellbore12section into the second interval section14b.

The plugging devices34may be disposed in the wellbore12section while flow into the first interval section14ais permitted.

The first flow restrictor30may be displaced along the wellbore12away from the surface by flow through the wellbore12.

The first flow restrictor30may be included in a tool assembly26secured to a conveyance28that limits displacement of the tool assembly26along the wellbore12.

The tool assembly26may include a second flow restrictor30longitudinally spaced apart from the first flow restrictor30. Flow into the first interval section14amay be permitted from the wellbore12between the first and second flow restrictors30.

The tool assembly26may displace along the wellbore12while flow into the first interval section14ais permitted.

The plugging devices34may be conveyed along the wellbore12with a tool assembly26that includes the first flow restrictor30while flow is permitted into the first interval section14a.

The term “above” is used in the above description to indicate a direction toward the surface along the wellbore12(which is not necessarily vertical at any particular section), and the term “below” is used to indicate a direction away from the surface along the wellbore.

In the above description of the representative examples, directional terms (such as “above,” “below,” “upper,” “lower,” “upward,” “downward,” etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein.

Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa.