Patent Publication Number: US-11021910-B2

Title: Sealing assembly and related methods

Description:
TECHNICAL FIELD 
     The present disclosure relates to an assembly and method for pressure control across a sealing system. 
     BACKGROUND 
     Underground drilling, such as gas, oil, or geothermal drilling, generally involves drilling a bore through a formation deep in the earth. Such bores are formed by connecting a drill bit to long sections of pipe, referred to as a “drill pipe,” to form an assembly commonly referred to as a “drill string.” Rotation of the drill bit advances the drill string into the earth, thereby forming the bore. Directional drilling refers to drilling systems configured to allow the drilling operator to direct the drill bit in a particular direction to reach a desired target hydrocarbon that is located some distance vertically below the surface location of the drill rig and is also offset some distance horizontally from the surface location of the drill rig. Steerable systems use bent tools located downhole for directional drilling and are designed to direct the drill bit in the direction of the bend. Rotary steerable systems use moveable blades, or arms, that can be directed against the borehole wall as the drill string rotates to cause directional change of the drill bit. Finally, rotary steerable motor systems also use moveable blades that can be directed against the borehole wall to guide the drill bit. Directional drilling systems have been used to allow drilling operators to access hydrocarbons that were previously un-accessible using conventional drilling techniques. 
     In order to lubricate the drill bit and flush cuttings from its path, a fluid, referred to as “drilling mud,” is directed through an internal passage in the drill string and out through the drill bit. The drilling mud then flows to the surface through the annular passage formed between the drill string and the surface of the bore. Since the drilling mud must be highly pressurized, the drill string is subjected to a large pressure gradient in the radial direction, as well as high axial and torque loading due to the forces associated with rotating and advancing the drill bit and carrying the weight of the drill string. 
     Sealing is used to keep lubricated fluids in, while preventing the addition of contaminants, such as mud and water. Sealing around rotating shafts is performed in numerous ways. Sealing moving shafts is difficult in high pressure, dynamic operations, such as at high differential pressures and relatively high shaft rotational speeds typical in drilling operations. In general, the contact stress between the seal and shaft increases with increasing differential pressure. As the pressure differential across the seal increases, the differential pressure acts on the unsupported area of the sealing element to create a high force, especially a high radial force, on the stationary sealing element acting against the rotating shaft. At some point, the seal can deform, extrude, or heat up to the point of leakage or failure. 
     SUMMARY 
     There is a need to provide better pressure control for a sealing system that limits the pressure differential across a sealing element. An embodiment of the present disclosure is a sealing assembly. The sealing assembly includes a housing having an outer surface, an inner surface, a main cavity defined by the inner surface, a first end and a second end spaced from the first end along a central longitudinal axis. The sealing assembly further includes a sealing unit mounted to the inner surface. The sealing unit includes an internal passage configured to receive a rotatable shaft, a first sealing element, and a second sealing element positioned uphole with respect to the first sealing element along the central longitudinal axis. The sealing assembly further includes a first valve carried by the housing and hydraulically coupled to the first sealing element and the main cavity. The first valve is configured to open at a first pressure level. The sealing assembly further includes a second valve carried by the housing and hydraulically coupled to the second sealing element and the main cavity. The second valve is configured to open at a second pressure level that is higher than the first pressure level. The sealing assembly is configured such that when the pressure exceeds the first pressure level and the second pressure level, the first relief valve and the second relief valve open sequentially so as to distribute pressure across the first sealing element and the second sealing element sequentially. 
     Another embodiment of the present disclosure is a sealing assembly configured for a pressurized sealing environment. The sealing assembly includes a housing having an outer surface, an inner surface, a main cavity defined by the inner surface, a first end and a second end spaced from the first end along a central longitudinal axis. The sealing assembly further includes a sealing unit mounted to the inner surface. The sealing unit includes an internal passage configured to receive a rotatable shaft, and at least two sealing elements positioned along the central longitudinal axis and in contact with the rotatable shaft. The sealing assembly further includes at least two valves carried by the housing and hydraulically coupled to the at least two sealing elements and the main cavity. The at least two valves are configured to transition from a closed configuration into an open configuration when the pressure exceeds different respective pressure levels. The sealing assembly is configured such that as the pressure exceeds the two different respective pressure levels and the at least two relief valves transition from a closed configuration into an open configuration, the pressure is distributed across the at least two sealing elements sequentially. 
     A further embodiment of the present disclosure is a method that includes causing drilling fluid to flow through an internal passage of a drill string carrying a tool assembly having a sealing unit comprising a first sealing element and a second sealing element each in contact with the shaft. The method further includes causing a shaft to rotate within the tool assembly, wherein the first and second sealing elements are in contact with the shaft. The method further includes opening a first valve of the tool assembly corresponding to the first sealing element when a pressure exceeds a first pressure level so as to distribute pressure across the first sealing element. The method further includes opening a second valve corresponding to the second sealing element when the pressure exceeds a second pressure level that is higher than the first pressure level, such that, the pressure is distributed is across the first sealing element and the second sealing element. 
     Another embodiment of the present disclosure is a sealing assembly. The sealing assembly includes a housing having an outer surface, an inner surface, a main cavity defined by the inner surface, a first end and a second end spaced from the first end along a central longitudinal axis. The sealing assembly further includes a sealing unit mounted to the inner surface. The sealing unit includes an internal passage configured to receive a rotatable shaft, a first sealing element, a second sealing element positioned uphole with respect to the first sealing element along the central longitudinal axis, a third sealing element positioned uphole with respect to the first sealing element and the second sealing element along the central longitudinal axis, and a fourth sealing element positioned uphole with respect to the first sealing element, the second sealing element, and the third sealing element along the longitudinal axis. The sealing assembly further includes a first valve carried by the housing and hydraulically coupled to the first sealing element and the main cavity. The first valve is configured to open at a first pressure level. The sealing assembly further includes a second valve carried by the housing and hydraulically coupled to the second sealing element and the main cavity. The second valve is configured to open at a second pressure level that is higher than the first pressure level. The sealing assembly further includes a third valve carried by the housing and hydraulically coupled to the third sealing element and the main cavity. The third valve is configured to open at a third pressure level that is higher than the first pressure level and the second pressure level. The sealing assembly further includes a fourth valve carried by the housing and hydraulically coupled to the fourth sealing element and the main cavity. The fourth valve is configured to open at a fourth pressure level that is higher than the first pressure level, the second pressure level, and the third pressure level. The sealing assembly further includes a compensation piston disposed in the main cavity. The compensation piston is movable relative to the sealing unit in response to an increase in pressure, wherein when the pressure exceeds the first pressure level, the second pressure level, the third pressure level, and the fourth pressure level, the first valve, the second valve, the third valve, and the fourth valve open sequentially so as to distribute pressure across the first sealing element, the second sealing element, the third sealing element, and the fourth sealing element sequentially. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description, will be better understood when read in conjunction with the appended drawings. The drawings show illustrative embodiments of the disclosure. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is a schematic side view of a drilling system according to an embodiment of the present disclosure; 
         FIG. 2  is a perspective view of a tool assembly according to an embodiment of the present disclosure; 
         FIG. 3  is a cross-sectional view of the tool assembly shown in  FIG. 2  taken along line  3 - 3 ; 
         FIG. 4  is a detailed cross-sectional view of a portion of the tool assembly shown in  FIG. 3 ; 
         FIG. 5  is another detailed cross-sectional view of a portion of the tool assembly shown in  FIG. 3 ; 
         FIG. 6  is another cross-sectional view of the tool assembly taken along line  3 - 3  shown in  FIG. 3 , illustrating an initial position of a compensation piston; 
         FIG. 7  is a cross-sectional view of the tool assembly shown in  FIG. 6 , illustrating the compensation piston in an intermediate position; 
         FIG. 8  is a cross-sectional view of the tool assembly shown in  FIG. 7 , illustrating the compensation piston in a terminal position; and 
         FIG. 9  is a process flow diagram illustrating a method for controlling pressure in the tool assembly shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     As shown in  FIGS. 1 and 2 , embodiments of the present disclosure include a pressure control tool assembly  100  configured for use in a downhole drilling environment in a drilling system  1 . The pressure control tool assembly  100  is used to reduce the differential pressure across sealing elements of a rotating shaft used in a downhole tool assembly of the drilling system  1 . “Tool assembly” and “sealing assembly” may be used interchangeably in the present disclosure. 
     Referring to  FIG. 1 , the drilling system  1  includes a rig or derrick  5  that supports a drill string  6 . The drill string  6  is elongate along a longitudinal central axis  27  that is aligned with a well axis E. The drill string  6  further includes a first end  8  and a second end  9  spaced from the first end  8  along the longitudinal central axis  27 . A downhole or downstream direction D refers to a direction from the surface  4  toward the second end  9  of the drill string  6 . An uphole or upstream direction U is opposite to the downhole direction D. Thus, “downhole” and “downstream” refers to a location that is closer to the drill string second end  9  than the surface  4 , relative to a point of reference. “Uphole” and “upstream” refers to a location that is closer to the surface  4  than the drill string downstream end  9 , relative to a point of reference. 
     Continuing with  FIG. 1 , the drill string  6  includes a bottom hole assembly (BHA)  10  coupled to a drill bit  15 . The drill bit  15  is configured to drill a borehole or well  2  into the earthen formation  3  along a vertical direction V and an offset direction θ that is offset from or deviated from the vertical direction V. The drilling system  1  can include a surface motor (not depicted) located at the surface  4  that applies torque to the drill string  6  via a rotary table or top drive (not depicted), and a downhole motor  18  disposed along the drill string  6  that is operably coupled to the drill bit  15  for powering the drill bit  15 . Operation of the downhole motor  18  causes the drill bit  15  to rotate along with or without rotation of the drill string  6 . In this manner, the drilling system  1  is configured to operate in a rotary drilling mode, where the drill string  6  and the drill bit  15  rotate, or a sliding mode where the drill string  6  does not rotate but the drill bit does rotate. Accordingly, both the surface motor and the downhole motor  18  can operate during the drilling operation to define the well  2 . The drilling system  1  can also include a casing  19  that extends from the surface  4  and into the well  2 . The casing  19  can be used to stabilize the formation near the surface. One or more blowout preventers can be disposed at the surface  4  at or near the casing  19 . During the drilling operation, in a drilling operation, the drill bit  15  drills a borehole into the earthen formation  3 . A pump  17  pumps drilling fluid downhole through an internal passage (not depicted) of the drill string  6  out of the drill bit  15 . The drilling fluid then flows upward to the surface through the annular passage  13  between the bore hole and the drill string  6 , where, after cleaning, it is recirculated back down the drill string  6  by the mud pump. 
     Referring to  FIGS. 2 and 3 , an exemplary downhole tool assembly  100  for pressure control includes a housing  102 , a sealing unit  110 , a valve assembly  112 , and a compensation piston  118  located inside of the housing  102 . The tool assembly  100  is elongated along a central axis A and has a first end  104 A and a second end  104 B opposite the first end  104 A along the central axis. The housing  102  has a body  108  that defines an outer surface  106 A, an inner surface  106 B, and an internal passage (not numbered) that extends from the first end  104 A to the second end  104 B along the inner surface  106 B. The internal passage is sized to permit a rotatable shaft S to pass therethrough. The body  108  has a length that extends from the first end  104 A to the second end  104 B along the central axis A. In the present disclosure, the length of the body  108  is approximately six inches. In alternative embodiments, the length of the body  108  may vary. 
     Referring to  FIG. 3 , the housing  102  carries the sealing unit  110  and the valve assembly  112 . The housing  102  includes a main cavity  114  defined by the inner surface  106 B. In the illustrated embodiment, the main cavity  114  is located at the second end  104 B of the tool assembly  100 . The main cavity  114  is located downhole of the valve assembly  112  and the sealing unit  110 . In alternative embodiments, the components of the downhole tool assembly  100  may be flipped such that the main cavity  114  is located uphole of the valve assembly  112  and the sealing unit  110 . The main cavity  114  includes an uphole portion  115 A and a downhole portion  115 B opposite the uphole portion  115 A. The main cavity  114  is open to an internal passage defined by the body of the housing. The internal passage receives therethrough the rotatable shaft S. The main cavity  114  carries the compensation piston  118 . The main cavity  114  is sized and shape to slidingly mate with an outer surface of the compensation piston  118 . However, the main cavity  114  is also sized to permit the compensation piston  118  to move along the central axis A in response to pressure changes in the downhole environment. The compensation piston  118  is configured to move towards the sealing unit  110  to the first end  115 A of the main cavity  114  as pressure increases. 
     The sealing unit  110  is also configured to slidingly receive the rotating shaft S. As shown, the sealing unit  110  may be mounted to the inner surface  106 B, yet is located downhole with respect to the valve assembly  112 . The sealing unit  110  may include one or more separate sealing elements  116  supported by one or more carriers  117 A- 117 D. In the illustrated embodiment, the sealing unit  110  includes four sealing elements  116 A,  116 B,  116 C, and  116 D and four respective carriers  117 A,  117 B,  117 C, and  117 D, respectively. In the present disclosure, the reference number  116  and  116 A though  116 D are used interchangeably to refer to similar configured sealing elements. As shown, the sealing unit  110  includes a first sealing element  116 A and a second sealing element  116 B located uphole relative to the first sealing element  116 A. The sealing unit  110  further includes a third sealing element  116 C located uphole relative to the first sealing element  116 A and the second sealing element  116 B. The sealing unit  110  also includes a fourth sealing element  116 D located uphole relative to the first sealing element  116 A, the second sealing element  116 B, and the third sealing element  116 C. The sealing elements  116 A- 116 D are lined up next to each other. An internal passage (not numbered) extends through each sealing element and is configured to receive the rotatable shaft S. In the illustrated embodiment, the sealing unit  110  includes four sealing elements. However, the sealing unit  110  may include more than four sealing elements, or less than four sealing elements may be used. For example, each sealing unit may include a first sealing element  116 A and a second sealing element  116 B. 
     Each sealing element  116 A- 116 D is defined by a seal that is in sealing contact with the rotatable shaft S. The sealing elements  116 A- 116 D are configured to compress against the inner surface  106 B of the pressure control tool assembly  100 , forming a seal against the inner surface  106 B. The seal divides a high pressure side located downhole relative to the sealing elements  116 A- 116 D and a lower pressure side located uphole relative to the sealing elements  116 A- 116 D. In this regard, the sealing elements  116 A- 116 D function as differential pressure sealing elements. Each sealing element  116 A- 116 D can define a ring shape that seats into respective annular grooves defined by the housing  102  (not depicted). In the illustrative embodiment, the sealing elements  116 A- 116 D are annular rings that form a seal with the rotating shaft S. In one example, the sealing elements  116 A- 116 D are T-seals. In another example, the sealing elements  116 A- 116 D are O-rings. In yet another example, the sealing elements  116 A- 116 D are quad seals. In another example, the sealing elements  116 A- 116 D are packing material. In yet another example, the sealing elements  116 A- 116 D may be comprised of metal and polished to form a seal with the rotating shaft S. Each of the sealing elements  116 A- 116 D are held by a respective carrier  117 A- 117 D. 
     The valve assembly  112  is configured to help distribute pressure across the different sealing elements. As shown, the valve assembly is located uphole relative to the main cavity  114  and the sealing unit  110 . The valve assembly  112  may include at least two separate valves. In the illustrated embodiment, the valve assembly  112  includes four valves: a first valve  120 A, a second valve  120 B, a third valve  120 C (not depicted), and a fourth valve  120 D (not depicted). The number of valves generally correspond to the number of sealing elements. For clarity in illustration and description, only the first valve  120 A and the second valve  120 B are illustrated in the figures. Each of the valves  120 A- 120 D are positioned such that the valves  120 A- 120 D generally surround the central axis A of the tool assembly  100 . The valves  120 A- 120 D are configured to open as pressure increases inside the pressure control tool assembly  100 . Each valve  120 A- 120 D can be rated to transition from a closed configuration into an open configuration at a predetermined pressure level. In one example, the predetermined pressure level can be about 3000 psi. In such an example, with four valves as described, a total pressure of 12,000 psi can be distributed across four sealing elements. The sequential distribution of pressure along pressure increases reduces contact stresses and the likelihood of heel extrusion of sealing elements and wear. 
     The first valve  120 A includes a first input passageway  122 Ai that is hydraulically coupled to the main cavity  114 . In particular, the first input passageway  122 Ai extends from the first valve  120 A to the main cavity  114  through the housing body  108 . The first valve  120 A further includes a first output passageway  122 A 2  that is hydraulically coupled to the first sealing element  116 A of the sealing unit  110 . Similarly, the second valve  120 B includes a second input passageway  122 Bi hydraulically coupled to the main cavity  114 , and a second output passageway  122 B 2  hydraulically coupled to the second sealing element  116 B of the sealing unit  110 . The first output passageway  122 A 2  extends from the first valve  120 A to a location between the first sealing element  116 A and the second sealing element  116 B. The second input passageway  122 Bi extends from the second valve  120 B to the main cavity  114 . The second output passageway  122 B 2  extends from the second valve  120 B to a location between the second sealing element  116 B and the third sealing element  116 C. As can be seen in the drawings, each input and output passageway described above does not define a linear path through the housing body  108 . More specifically, each passageway has one or more deviations to direct fluid from the valve to its outlet point. As used herein, a deviation may be a curve or bend in the passageway. 
     In the illustrative embodiment, the third valve  120 C and the fourth valve  120 D each include an input passageway (not depicted) coupled to the main cavity  114 , and an output passageway (not depicted) coupled to the third sealing element  116 C and the fourth sealing element  116 D of the sealing unit  110 , respectively. The third input passageway extends from the third valve  120 C to the main cavity  114 . The third output passageway extends from the third valve  120 C to a location between the third sealing element  116 C and the fourth sealing element  116 D. The fourth input passageway extends from the fourth valve  120 D to the main cavity  114 . The fourth output passageway extends from the fourth valve  120 D to a location between the fourth sealing element  116 D and the end of the sealing unit  110 . As described above, each input and output passageway for the third and fourth valves do not define a linear path through the housing body. More specifically, each passageway has one or more deviations to direct fluid from the valve to its outlet point. As used herein, a deviation may be a curve or bend in the passageway. 
       FIG. 4  is a side view of a cross section of the first valve  120 A of valve assembly  114  in  FIG. 3 . The first valve  120 A includes a plug  126  and springs  128 . The first valve  120 A is configured to carry lubricant. In one example, the lubricant is a de-aired oil that fills the cavities and passageways of the valve assembly. In the illustrated embodiment, the plug  126  is made of metal. In an alternative embodiment, the plug  126  may be a diaphragm plug. In the illustrated embodiment, the springs  128  may be Belleville springs. In alternative embodiments, the springs  128  may be any type of spring known in the art. The springs  128  are configured to deform as pressure increases inside the pressure control tool assembly  100 , via the first input passageway  122 Ai. When the springs  128  deform, the first valve is pushed open, directing the pressure out via the output passageway  122 A 2  and across the first sealing element  116 A. 
     The valves  120 A- 120 D are configured to transition from a closed configuration into an open configuration when the pressure exceeds a predetermined pressure level. The open configuration is when the pressure in the input passageway exceeds the predetermined pressure level, causing the plug  126  to compress the spring and separate from the valve wall to allow fluid to enter the output passageway. In this manner, fluid can be directed toward the sealing element and pressure is therefore distributed across that sealing element. As pressure increases, the second valve  120 B transitions into the open configuration when pressure exceeds a predetermined level. This continues until each valve transitions from the closed configuration into the open configuration. In one example, the predetermined pressure level for each valve can be about 3000 psi. In such an example, with four valves as described, a total pressure or 12,000 is psi can be distributed across four sealing elements. The sequential distribution of pressure along with increase in pressure reduces contact stresses and the likelihood of heel extrusion of the sealing elements. 
     Referring to  FIG. 5 , the main cavity  114  carries the compensation piston  118 . The compensation piston  118  is configured to move in the main cavity  114  relative to the sealing unit  110  in response to an increase in pressure. In the illustrative embodiment, the compensation piston  118  is an annular piston. The compensation piston  118  may be shaft-guided by a journal bearing relationship with the shaft. This configuration may minimize the compression changes and the lateral sliding motion that the sealing elements  116 A- 116 D experience due to lateral shaft movement. A clearance (not numbered) is provided between the compensation piston  118  and the housing  102 , to accommodate lateral shaft misalignment and deflection without binding the compensation piston  118 . The compensation piston  118  is configured to partition the lubricant from the drilling fluid environment, balance the lubricant pressure to the drilling fluid environment, and limit the deflection and stress of the rotatable shaft S. 
       FIGS. 6-8  illustrate the tool assembly  100  shown in  FIG. 3 , as the compensation piston  118  moves uphole toward the sealing unit  110  from an initial position to a terminal position. Referring to  FIG. 6 , when differential pressure is below a predetermined value or is at or near zero pressure differential, the compensation piston  118  is positioned at the second end of the main cavity  114  in a first or initial position P 1 . Upon application of pressure or an increase in pressure, as illustrated in  FIG. 7 , the compensation piston moves toward the sealing unit  110  into an intermediate position P 2 . When the pressure exceeds a first pressure level, the first valve  120 A opens. The pressure is then distributed across the first sealing element  116 A through the first output passageway  122 A 2  to a location between the first sealing element  116 A and the second sealing element  116 B. When the pressure continues to exceed a second pressure level, which is generally higher than the first pressure level, the second valve  120 B opens. The pressure is then distributed across the second sealing element  116 B through the second output passageway  122 B 2  to a location between the second sealing element  116 A and the third sealing element  116 B. This mechanism is repeated for the third valve  120 C and fourth valve  120 D as pressure increases past a third pressure level and a fourth pressure level. Accordingly, as pressure continues to increase, the piston  118  moves into a final or terminal position P 3  in the main cavity  114 , as shown in  FIG. 8 , causing the pressure to distribute across all the sealing elements  116 A- 116 D as described above. 
     The practical result is that relatively equal pressure differentials across each of the sealing elements  116 A- 116 D is obtained. For example, in an alternative embodiment where the pressure control tool assembly has five sealing elements, if a 15,000 psi pressure was applied to the pressure control tool assembly, then the mechanism described would provide a differential pressure of 3,000 psi across each of the five sealing elements. In the illustrated embodiment, the pressure levels which cause the valves to open vary depending on the application. For example, in an alternative embodiment where the pressure control tool assembly has 15 sealing elements, if a 15,000 psi pressure was applied, then the pressure level that each seal would withstand would be 1,000 psi. If pressure begins to decrease, the valves will close, and a higher level of pressure will be trapped within each sealing element. This pressure will remain in each sealing element but will likely decay with time as each sealing element repositions itself. 
     Now referring to  FIG. 9 , a method  900  for controlling pressure in the pressure control tool assembly  100  shown in  FIG. 3 , will be described. In step  902 , the drilling commences. The drill string  6  is rotated by the drive system and drilling fluid is pumped through the drill string  6  and along the downhole tool assembly  100 . In step  904 , as the drill string progresses through the formation, pressure within the tool assembly  100  generally increases, applying pressure to the compensation piston  118  in the main cavity  114  of the housing  102  which, in turn, moves the compensation piston  118  from an initial position toward the sealing unit  114 . In step  906 , the first valve  120 A transitions from a closed configuration into an open configuration when the pressure exceeds a first pressure level, distributing pressure across the first sealing element  116 A via the first output passageway  122 A 2 . In step  908 , as the pressure continues to increase, the second valve  120 B transition from the close configuration into the open configuration when the pressure exceeds a second pressure level, which is higher than the first pressure level. At this point, pressure is distributed across the second sealing element  116 B via the second output passageway  122 B 2 . In step  910 , as the pressure continues to increase, the third valve  120 C transitions from the closed configuration into the open configuration when the pressure exceeds a third pressure level. When the third valve is in the open configuration, pressure is distributed across the third sealing element via the third output passageway. Finally, in step  912 , as pressure continues to increase, the fourth valve  120 D transitions from the closed configuration into the open configuration when the pressure exceeds a fourth pressure level. When the fourth valve is in the open configuration, pressure is distributed across the fourth sealing element via the fourth output passageway. 
     Accordingly, the tool assembly configuration limits the pressure differential that occurs across any one sealing element by relieving some of the working pressure to a location between the respective sealing element and the adjacent downhole sealing element. As described above, each valve can be rated to open at the predetermined pressure level, e.g. 3000 psi. With four valves as described, a total pressure of 12,000 psi can be distributed across the four sealing elements, at a differential pressure of 3,000 psi per sealing element. The sequential distribution of pressure as the pressure increases reduces contact stresses and the likelihood of heel extrusion. 
     The present disclosure is described herein using a limited number of embodiments, these specific embodiments are not intended to limit the scope of the disclosure as otherwise described and claimed herein. Modification and variations from the described embodiments exist. For example, the terms “uphole” and “downhole” are only meant to describe the ends of the tool assembly. The tool assembly may be completely inverted. In addition, in alternative embodiments, the valves may be electrically or pneumatically controlled. Further, while embodiments of the present disclosure are shown and described with reference to oil and gas drilling systems, the sealing system and assembly as described herein may be used anywhere a high pressure seal is required, including environments involving a rotating shaft or a feature that compromises a standard static seals capability. 
     More specifically, the following examples are given as a specific illustration of embodiments of the claimed disclosure. It should be understood that the invention is not limited to the specific details set forth in the examples.