WELLBORE LANDING METHODS FOR RESERVOIR STIMULATION

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present document is based on and claims priority to US Provisional

Application Serial No.: 62/393,327, filed September 12, 2016, which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] In various well applications, the subterranean formation is stimulated to enhance recovery of hydrocarbon fluids such as oil and gas. One form of well stimulation is hydraulic fracturing which may be conducted in a wellbore following a drilling operation and an optional casing operation. Hydraulic fracturing operations initially were performed in single stage vertical or near vertical wells. To further improve productivity, however, hydraulic fracturing operations have trended toward use in generally horizontal wells. Although horizontal fracturing operations have improved productivity, current methods have limitations with respect to productivity and efficiency in certain types of subterranean environments and operations.

SUMMARY

[0003] In general, the present disclosure provides a methodology and system for enhancing hydrocarbon fluid production. A well is formed in a subterranean region by drilling a borehole, e.g. a wellbore, which has a lateral section. The lateral section may be located at least in part in a non-productive zone of the subterranean region. In cooperation with the lateral section, at least one tunnel is formed which intersects the lateral section and penetrates a productive zone containing hydrocarbon fluid. In various embodiments, a plurality of tunnels may be formed to extend from the lateral section outwardly into the productive zone. A well stimulation, e.g. hydraulic fracturing, may be performed through the tunnel(s) to stimulate a desired stimulation zone or zones within the productive zone.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate various

implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0005] Figure 1 is a schematic illustration of an example of a well system having a borehole with a lateral section and a plurality of tunnels extending from the lateral section, according to an embodiment of the disclosure;

[0006] Figure 2 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure;

[0007] Figure 3 is a schematic illustration of an example of a borehole having one type of lateral section, according to an embodiment of the disclosure;

[0008] Figure 4 is a schematic illustration of another example of a borehole having a different type of lateral section, according to an embodiment of the disclosure; [0009] Figure 5 is a schematic illustration of another example of a borehole having a different type of lateral section, according to an embodiment of the disclosure;

[0010] Figure 6 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure;

[0011] Figure 7 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure;

[0012] Figure 8 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure;

[0013] Figure 9 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure;

[0014] Figure 10 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure;

[0015] Figure 1 1 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure; and

[0016] Figure 12 is a schematic illustration of another embodiment of the well system with a lateral section and a plurality of tunnels, according to an embodiment of the disclosure. DETAILED DESCRIPTION

[0017] In the following description, numerous details are set forth to provide an understanding of some illustrative embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or

methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0018] The disclosure herein generally relates to a methodology and system for enhancing hydrocarbon fluid production. According to an embodiment, a well may be formed in a subterranean region by drilling a borehole, e.g. a wellbore, which has a lateral section. For example, the wellbore may be drilled from the surface along a generally vertical section and then turned laterally and drilled to form a lateral section in the subterranean region. In some applications, the lateral section may generally be a horizontal section although the horizontal section may have undulating, e.g. sinusoidal, or inclined/declined sections of wellbore.

[0019] According to an embodiment of the methodology, the lateral section may be located at least in part in a non-productive zone of the subterranean region. The nonproductive zone is a zone which contains limited amounts of hydrocarbon fluid or is less desirable with respect to production of hydrocarbon fluid. For example, the nonproductive zone may be in a zone of the subterranean region which has a substantially higher minimum in situ stress in the rock compared to a desirable productive zone.

[0020] To facilitate production, at least one tunnel is formed which intersects the lateral section and penetrates a productive zone containing hydrocarbon fluid. Often, a plurality of tunnels may be formed to extend from the lateral section outwardly into the productive zone. In some applications, the lateral section of the wellbore may be entirely outside of the productive zone and a plurality of tunnels may be formed in a desired direction, e.g. upwardly and/or downwardly, to reach the productive zone. In other applications, however, the lateral section of wellbore may extend into or through the productive zone.

[0021] Once the tunnel or tunnels are formed, a well stimulation may be performed through the tunnel(s) to stimulate a desired stimulation zone or zones within the productive zone. The well stimulation may comprise a hydraulic fracturing of the stimulation zone or zones. Hydraulic fracturing may be achieved by pumping a fracturing fluid down through the wellbore and out through the tunnels to fracture the subterranean formation at the stimulation zones adjacent the tunnels. The fracturing of the stimulation zones within the productive zone enhances production of hydrocarbon fluid from the productive zone to the wellbore and ultimately to the surface.

[0022] According to one type of embodiment, the lateral section of wellbore is drilled as a horizontal section of the well outside of a target zone, e.g. above or below the target zone. The target zone may be a productive zone of the subterranean region containing desired hydrocarbon fluid. In this example, more than two substantially vertical tunnels are formed to extend from the horizontal section so as to penetrate the target zone. A stimulation procedure is then performed through the vertical tunnels. Depending on the characteristics of the subterranean region, the horizontal section of the well may be landed in a nonproductive rock and/or in a region with petrophysical and geo-mechanical properties different from the properties of the target zone, e.g. a substantially higher minimum in situ stress relative to that of the target zone. It should be noted the substantially vertical tunnels may be used in certain types of formations, e.g. laminated formations, to facilitate flow of fluid to the tunnels even in the presence of pinch points between formation layers.

[0023] If the stimulation procedure comprises a hydraulic fracturing procedure, the general methodology comprises initially drilling a borehole with a lateral section in a subterranean region. A plurality of tunnels may be formed so as to extend outwardly, e.g. upwardly and/or downwardly, from the lateral section. A fracturing fluid may then be pumped down through the borehole, into the lateral section, and out through the plurality of tunnels. The fracturing fluid is forced under pressure from the tunnels out into the surrounding subterranean region, e.g. into the surrounding oil bearing formation, to fracture the surrounding subterranean region. For example, the surrounding subterranean region/formation may be fractured at a plurality of stimulation zones within the overall productive zone or zones. It should be noted the fracturing fluid also may comprise propping agent for providing fracture conductivity after fracture closure. In certain embodiments, the fracturing fluid may comprise acid such as hydrochloric acid, acetic acid, citric acid, hydrofluoric acid, other acids, or mixtures thereof.

[0024] Referring generally to Figure 1, an embodiment of a well system 20 is illustrated as extending into a subterranean region 22. The well system 20 enables a methodology for enhancing recovery of hydrocarbon fluid, e.g. oil and/or gas, from a well. In this embodiment, a borehole 24, e.g. a wellbore, is drilled down into the subterranean region 22 and includes a lateral section 26. By way of example, the lateral section 26 may be generally horizontal although the horizontal section may comprise inclines, declines, and undulations formed intentionally or resulting from drilling through the rock of subterranean region 22.

[0025] At least one tunnel 28 and often a plurality of tunnels 28 may be formed to intersect the lateral section 26. The tunnels 28 provide fluid communication with an interior of the lateral section 26 to facilitate flow of the desired hydrocarbon fluid from tunnels 28, into lateral section 26, and up through wellbore 24 to, for example, a surface collection location 30.

[0026] The tunnels 28 may be oriented in various directions depending on the material forming subterranean region 22 and on the location of desired hydrocarbon fluids. In some embodiments, the tunnels 28 may be formed in a generally vertical orientation to extend upwardly from lateral section 26 as illustrated in Figure 1. The tunnels 28 also may be formed in a generally vertical orientation to extend downwardly from lateral section 26, as illustrated in Figure 2. [0027] In some subterranean regions 22, the structure of the rock formation may create flow pinch points 32 (see upper left diagram in Figure 1 and lower left diagram in Figure 2). The flow pinch points 32 effectively may be stacked above each other even after performance of a hydraulic fracturing operation. The substantially vertical orientation of tunnels 28 facilitates the flow of hydrocarbon fluid past these pinch points and into the tunnels 28 for delivery to lateral section 26. It should be noted other embodiments may utilize tunnels 28 extending in different directions and/or in multiple directions from the lateral section 26.

[0028] As further illustrated in Figure 2, a stimulation operation may be performed via tunnels 28 to create stimulation zones 34 which facilitate flow of fluid into the corresponding tunnels 28. By way of example, hydraulic fracturing operations may be performed to fracture the subterranean region 22, e.g. oil bearing formation, to facilitate flow of the desired fluid into the corresponding tunnels 28. If the stimulation operation is a hydraulic fracturing operation, fracturing fluid may be pumped from the surface, down through wellbore 24, through lateral section 26, into tunnels 28, and then into the stimulation zones 34 surrounding the corresponding tunnels 28. In some applications, a perforating operation may be performed in tunnels 28 to facilitate fracturing of the desired zones 34 in subterranean region 22. According to an

embodiment, the tunnels 28/zones 34 may be fractured sequentially. For example, the fracturing operation may be performed through sequential groups of tunnels 28 or sequentially through individual tunnels 28 to cause sequential fracturing of the stimulation zones 34.

[0029] The tunnels 28 may be formed via a variety of techniques, such as various drilling techniques. For example, drilling equipment may be deployed down into lateral section 26 and used to form the desired number of tunnels 28 in appropriate orientations for a given subterranean environment and production operation. However, the tunnels 28 also may be formed by other suitable techniques, such as jetting techniques, laser techniques, or other available tunnel formation techniques. [0030] Depending on the parameters of the given subterranean environment and production operation, the wellbore 24 may be completed with various types of equipment and procedures. By way of example, a casing 36 may be deployed along at least a portion of the wellbore 24, e.g. along a generally vertical portion 38 of wellbore 24. However, the casing 36 also may be deployed along lateral, e.g. horizontal, section 26 which may be completed as a cased or open hole section. A cementing procedure may then be performed to place a cement 40 along the casing 36. Other completion equipment may comprise various sand screen assemblies, packers, sleeves, control valves, and other suitable equipment to facilitate stimulation and/or production.

[0031] In the illustrated example, the completion equipment comprises a plurality of packers 42, e.g. open hole packers, deployed along lateral section 26. Additionally, flow control devices 44, e.g. frac sleeves, may be positioned to enable selective control of flow between individual tunnels 28 and the interior of lateral section 26. Many other types of equipment may be used to control flow and to facilitate aspects of the injection and/or production operations.

[0032] Referring generally to Figures 3-5, different configurations of wellbore 24 are illustrated as having lateral section 26 disposed in slightly different orientations and configurations. Depending on the configuration of lateral section 26, the movement of hydrocarbon fluid and thus the efficiency of production may be affected. However, the formation of tunnels 28 and stimulation zones 34 facilitate improved and more efficient hydrocarbon production with several types of configurations of lateral section 26.

[0033] In the example illustrated in Figure 3, the well and well system 20 may demonstrate a "slugging" behavior due to the undulating or serpentine configuration of lateral section 26. The "sinusoidality" of lateral section 26 may lead to repetitive accumulation of liquid 46, e.g. oil, in lower portions of the lateral/horizontal section 26. The portions of liquid 46 may be separated by gas 48 disposed between portions of liquid 46. Such a configuration could lead to decreased production performance, but the formation of tunnels 28 and stimulation zones 34 enhance the production capability. It should be noted the oil 46 and/or gas 48 may be the desired hydrocarbon fluid produced to surface location 30.

[0034] In some applications, the liquid unloading efficiency of the wellbore 24 may be improved by reducing or eliminating the wellbore "sinusoidality" by drilling the lateral section 26 at a slight decline such that liquid/oil 46 collects in a toe 50 of the lateral section 26, as illustrated in Figure 4. Similarly, the liquid unloading efficiency may be improved by drilling the lateral section at a slight incline such that the liquid/oil 46 collects in a heel 52 of the lateral section 26, as illustrated in Figure 5. Regardless of the specific configuration of lateral section 26, the tunnels 28 may be formed to facilitate production when the lateral section 26 is located in a productive zone, partially in a productive zone, or outside of a productive zone containing the desired hydrocarbon 46/48. Stimulation of zones 34, e.g. fracturing of zones 34, also may be used to facilitate production by increasing the flow of hydrocarbon fluid into tunnels 28 and thus into lateral section 26.

[0035] Referring generally to Figures 6-9, various wellbore geometries are illustrated to facilitate production of a hydrocarbon fluid, e.g. oil and/or gas, from a productive zone 54 in subterranean region 22. In the embodiment illustrated in Figure 6, the lateral section 26 of wellbore 24 is drilled generally horizontally but with an incline such that the toe 50 is higher than the heel 52 similar to the configuration illustrated in Figure 5. As illustrated, the plurality of tunnels 28 may be constructed to intersect lateral section 26 and to extend downwardly such that the tunnels 28 penetrate the productive zone 54. For example, the tunnels 28 may extend into or through the productive zone 54.

[0036] For some types of subterranean regions 22, the tunnels 28 may be oriented generally vertically and may extend at least partially through a nonproductive zone or zones 56 as well as productive zone 54. In this particular example, the lateral section 26 may be located entirely in a nonproductive zone 56. The tunnels 28 are formed, e.g. drilled, from lateral section 26, through the initial nonproductive zone 56, and into the productive zone 54 to facilitate production of the desired hydrocarbon fluid. Within the productive zone 54, stimulation treatments may be performed through the tunnels 28 to create the stimulation zones 34. With a hydraulic fracturing treatment, for example, fracturing fluid may be pumped down through wellbore 24, through lateral section 26, through tunnels 28, and into the surrounding formation of productive zone 54 to create stimulated/hydraulically fractured zones 34.

[0037] In another embodiment, the wellbore geometry may be selected such that a similarly inclined lateral section 26 of wellbore 24 extends through the productive zone 54, as illustrated in Figure 7. In this type of embodiment, the tunnels 28 may be appropriately oriented in the downward direction and upward direction as illustrated, such that they penetrate the productive zone 54. The tunnels 28 may again be used to form the stimulation zones 34 so as to facilitate enhanced production of hydrocarbon fluids 46/48 from the productive zone 54.

[0038] According to the embodiment illustrated in Figure 8, the lateral section 26 of wellbore 24 may be drilled generally horizontally but with a decline such that the toe 50 is lower than the heel 52 similar to the configuration illustrated in Figure 4. As illustrated, the plurality of tunnels 28 may be constructed to intersect lateral section 26 and to extend downwardly such that the tunnels 28 penetrate the productive zone 54, e.g. extend into or through the productive zone 54. In this example, the lateral section 26 may again be located entirely in a nonproductive zone 56. The tunnels 28 may be formed, e.g. drilled, from lateral section 26, through the initial nonproductive zone 56, and into the productive zone 54 to facilitate production of the desired hydrocarbon fluid. Stimulation treatments may be performed through the tunnels 28 to create the stimulation zones 34 within productive zone 54.

[0039] In another embodiment, the wellbore geometry may be selected such that a similarly declined lateral section 26 of wellbore 24 extends through the productive zone 54, as illustrated in Figure 9. In this type of embodiment, the tunnels 28 may be appropriately oriented in the downward direction and upward direction, as illustrated, such that they penetrate the productive zone 54. The tunnels 28 may again be used to form the stimulation zones 34 so as to facilitate enhanced production of hydrocarbon fluids 46/48 from the productive zone 54.

[0040] The particular geometry of wellbore 24 and lateral section 26, as well as the number and orientation of tunnels 28, may be selected according to various considerations. For example, the geometry may be based on considerations of flow performance of the wellbore, e.g. flow performance in productive zone 54, and on the accessibility of the productive zone 54 via, for example, tunnels 28. Additionally, a variety of stimulation techniques other than or in addition to hydraulic fracturing may be used via tunnels 28 to create stimulation zones 34. Examples of such other stimulation techniques include matrix acidizing, acid fracturing, propellant treatment, injection of chelating agents, or other suitable stimulation techniques. The lateral section 26 as well as other portions of wellbore 24 may be formed within, through, or outside of the productive zone 54.

[0041] Referring generally to Figures 10 and 11, additional examples of wellbore geometries are illustrated. These wellbore geometries are able to similarly facilitate production of a hydrocarbon fluid, e.g. oil and/or gas, from productive zone 54 in subterranean region 22. In the embodiment illustrated in Figure 10, the lateral section 26 of wellbore 24 is drilled generally horizontally but with an undulating configuration to follow a certain formation layer. The sinusoidal lateral section 26 may be oriented at a general incline, as illustrated, or a general decline. Similar to other embodiments, the plurality of tunnels 28 may be constructed to intersect lateral section 26 and to extend downwardly such that the tunnels 28 penetrate the productive zone 54.

[0042] For example, the tunnels 28 may extend into or through the productive zone 54. For some types of subterranean region 22, the tunnels 28 may be oriented generally vertically and may extend at least partially through a nonproductive zone or zones 56 as well as productive zone 54. The lateral section 26 may be located entirely in a nonproductive zone 56, as illustrated, or the lateral section 26 of wellbore 24 may enter the productive zone 54. The tunnels 28 may be formed, e.g. drilled, from lateral section 26, through the initial nonproductive zone 56, and into the productive zone 54. Within the productive zone 54, stimulation treatments may be performed through the tunnels 28 to create the stimulation zones 34 as with other embodiments described herein.

[0043] In another embodiment, lateral section 26 may be disposed in a nonproductive zone 56 below the productive zone 54, as illustrated in Figure 11. With this type of wellbore geometry, the tunnels 28 again intersect the lateral section 26 but extend generally upwardly to penetrate the productive zone 54. For example, the tunnels 28 may be formed to terminate within the productive zone 54 or to extend through the productive zone 54 as with other embodiments described herein.

[0044] Referring generally to Figure 12, another embodiment is illustrated in which the lateral section 26 is disposed between two productive zones 54. The lateral section 26 may follow a desired formation layer, as illustrated, or may have other substantially horizontal configurations. In this example, the tunnels 28 may be formed in a substantially vertical orientation extending both upwardly into the first productive zone 54 and downwardly into the second productive zone 54. As with other embodiments, stimulation zones 34 may be formed to facilitate hydrocarbon production, and those stimulation zones 34 may be located in both productive zones 54.

[0045] The lateral section 26 may be drilled in productive zone 54 and/or nonproductive zone 56. The specific configuration of the wellbore 24 and the location of lateral section 26 in one or more productive zones 54 and non-productive zones 56 may depend on the type of environment found in subterranean region 22. For example, the lateral section 26 of wellbore 24 may be landed in zones having properties which minimize the likelihood of creating hydraulic fractures in those zones.

[0046] In such an embodiment, the lateral section 26 may be landed in a nonproductive zone 56 having, for example, a higher minimum in situ stress than the productive zone 54. The lateral section 26 also may be landed in a non-productive zone 56 which has a higher density of natural fractures which, when hydraulically fractured, conform initially complex fracture networks having low fracture width. In this latter type of fracture network, propagation of the fracture network can be stopped via bridging solid particles in created fractures. However, the use of tunnels 28 obviates this type of problem by ensuring fracturing occurs in the desired productive zone 54. By way of further example, the lateral section 26 may be landed in a non-productive zone 56 which has high poroelasticity or pseudo-poroelasticity.

[0047] Wellbore landings in which the lateral section 26 is placed in one of these types of non-productive zones 56 may be especially beneficial in open-hole completions. In such applications, the tunnels 28 may be formed to extend from the open hole lateral section 26; and open hole packers 42 may be used to provide isolation between various wellbore zones. If the lateral section 26 is placed in a non-productive zone 56 with relatively higher stress, the productive zone 54 may be fractured or otherwise stimulated through the tunnels 28 - thus minimizing the likelihood of creating fractures extending from the open hole portion of the lateral section 26 but not connected to tunnels 28.

[0048] Placement of the lateral section 26 in such non-productive zones 56 also may be used to facilitate acidizing treatments and other chemical treatments. For example, lateral section 26 may be located in a zone which is not reactive to the pumped chemical agents. However, tunnels 28 may be used to enable transfer of the chemical agents to the desired zone, e.g. productive zone 54.

[0049] Because of the characteristics of many subterranean regions 22, the production of hydrocarbon fluids from productive zones 54 may be increased greatly by utilizing a substantially horizontal lateral section 26 and substantially vertical tunnels 28. For example, the rock in a given subterranean region 22 may be layered to effectively create a laminated formation and such a formation can create stacked pinch points 32 which restrict flow if fracturing is performed from a horizontal section of the wellbore. Accordingly, the use of wellbore geometries having a substantially horizontal lateral section 26 and substantially vertical tunnels 28 (with appropriate stimulated regions 34) can substantially reduce the impact of pinch points and enhance production of hydrocarbon fluids 46, 48 through the wellbore 24.

[0050] It should be noted, however, the orientation of the lateral section 26 and the tunnels 28 may be changed to accommodate different types of formations, environmental conditions, and production equipment. For example, references to substantially vertical tunnels 28, extending upwardly or downwardly, may be considered as tunnels 28 oriented at an angle less than 45° from vertical. In some embodiments, tunnels 28 are oriented at an angle less than 20° from vertical. However, the tunnels 28 may be formed with other orientations and configurations, e.g. various serpentine configurations, lateral orientations, or other configurations and orientations suited for the parameters of a given application. Similarly, references to substantially horizontal lateral section 26 may be considered lateral sections inclined/declined less than 45° from horizontal. In some embodiments, the substantially horizontal lateral section 26 is inclined/declined less than 20° from horizontal. However, lateral section 26 may be formed at other angles and with other configurations selected according to the parameters of a given environment and operation.

[0051] The wellbore geometries described herein also may be used to reduce the amount of sand and material used in a variety of fracturing operations while still enhancing production of the desired hydrocarbon fluids. In various geographies worldwide, records indicate that approximately 2000 wells, including those of the Barnett Shale reservoir, were arranged vertically and stimulated with approximately 100,000- 500,000 pounds of sand and approximately 5000-20,000 bbls of fluid, e.g. water. In new horizontal wells, stimulation occurred in 5-10 stages with approximately 100,000- 500,000 pounds of sand and approximately 5000-20,000 bbls of fluid per stage. These volumes of sand and water would be sufficient for stimulation of 5-10 vertical wells which would result in a 5 to 10 times production increase for the same amount of sand and fluid. [0052] From the statistical data, however, we see that using these volumes for stimulating horizontal wells actually provides approximately a two-fold production increase. This effectively translates to an approximately 2.5-5 times decrease in production per pound of sand and bbl of fluid pumped for horizontal wells compared to vertical wells. Possible explanations of lower stimulation efficiency with respect to horizontal wells may relate to conversion of flow in a near wellbore zone or loss of connectivity of created fractures or portions of fractures with the wellbore as a result of, for example, pinch-pointing in laminated formations.

[0053] There also may be connectivity loss between created fractures and the wellbore as a result of near wellbore complexity or over flushing of the near wellbore zone during the fracturing treatment or other treatments. The wellbore geometries described herein increase efficiency with respect to use of sand and fluid by employing substantially vertical tunnels 28 in combination with a substantially horizontal lateral section 26. The substantially vertical tunnels 28 enhance production from one or more productive zones 54 while limiting the inefficient use of sand/proppant associated with hydraulic fracturing from horizontal wellbores.

[0054] Depending on the parameters of a given application, the wellbore geometries described herein may be adjusted according to the type, size, orientation, and other features of the productive zone or zones 54. Additionally, the location of the lateral section 26 as well as the tunnels 28 may be affected by the type of non-productive zones 56 adjacent the productive zone(s) 54 containing desired hydrocarbon fluids. Similarly, many different types of equipment, e.g. packers, valves, sleeves, sand screens, and/or other types of equipment may be used in completing the lateral section 26 as well as the overall wellbore 24. Various sections of the wellbore 24, including the lateral section 26, may be cased or open-hole depending on the parameters of the specific application.

[0055] Although a few embodiments of the system and methodology have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.