Patent Application
20190153797
In the drilling of oil and gas wells, a downhole drilling motor and a drill bit are attached to the end of a drill string. Most downhole drilling motors include a rotor rotating within a stator. The rotation of the rotor provides a vibration to the adjacent drill bit as it cuts through the subterranean formation to drill the wellbore. The drill string slides through the higher portions of the wellbore as the drill bit at the end of the drill string extends the wellbore deeper into the formation. A vibration tool is sometimes attached to the drill string a distance above the drill bit (e.g., 800-1,500 feet above the drill bit). The vibration tool provides vibration to the portions of the drill string above the vibration tool, thereby facilitating the movement of the drill string through the wellbore.
Conventional vibration tools include a power section made of a rotor rotating within a stator and a valve positioned below the rotor. As the rotor rotates, the valve periodically restricts fluid flow through the vibration tool, which creates a pressure pulse or waterhammer that is transmitted through the power section and up through the portion of the drill string above the vibration tool.
A vibration assembly of the present disclosure may be attached to a drill string and lowered into a wellbore. The vibration assembly may include a valve positioned above a power section. The power section may be a positive displacement power section, a turbine, or any other hydraulic motor mechanism for generating torque with a fluid flow. In one embodiment, the power section is a positive displacement power section including a rotor disposed at least partially within a stator. The rotor is configured to rotate within the stator as a fluid flows through the vibration assembly. The valve may include a rotating valve segment and a stationary valve segment each including at least one fluid passage. The rotating valve segment is configured to rotate with rotation of the rotor, while the stationary valve segment remains fixed (i.e., does not rotate). In an open position, the fluid passage of the rotating valve segment is aligned with the fluid passage of the stationary valve segment, and the fluid flows through these fluid passages of the valve. In a restricted position, the fluid passage of the rotating valve segment is not aligned with a fluid passage in the stationary valve segment (e.g., at least partially unaligned), thereby temporarily restricting the fluid flow through the valve. The flow restriction creates a pressure pulse or waterhammer that is transmitted upstream thereby stretching and retracting a drill string or coiled tubing line above the vibration assembly. Because the valve is positioned above the power section, the vibration assembly of the present disclosure transmits a pressure pulse to the drill string above more efficiently than conventional vibration tools. In certain embodiments, the vibration assembly may also include a shock assembly disposed at an upper end of the vibration assembly. When present, the shock assembly facilitates relative axial movement of the drill string above the vibration assembly relative to the drill string below the vibration assembly thereby vibrating the drill string above the vibration assembly.
In some embodiments, a flex shaft or stiff cable may interconnect the valve and the power section. An upper end of the flex shaft or cable may be attached to the rotating valve segment, and a lower end of the flex shaft or cable may be attached to the rotor. In this way, the flex shaft or cable transmits torque from the rotor to the rotating valve segment to rotate the rotating valve segment with the rotation of the rotor.
With reference to
In other embodiments, rotating and stationary valve segments 20, 22 include no central passages. Instead, the fluid passages of valve segments 20, 22 are arranged such that at least one fluid passage of rotating valve segment 20 is partially aligned with a fluid passage of stationary valve segment 22 in the restricted position to guarantee a minimum fluid flow to drive rotor 16 in stator 18.
Referring now to
Housing 60 may include inner bore 61. Housing 60 may be formed of housing segments 62, 64, 66, and 68, each including an inner bore. Nut 50 may be threadedly connected to the inner bore of housing segment 64. Radial bearings 48 may engage a shoulder of housing segment 64 to support thrust bearings 46, compression sleeve 52, and stationary valve segment 22, thereby operatively suspending flex shaft 14 and rotor 16 within inner bore 61 of housing 60. Stator 18 may be secured within the inner bore of housing segment 66. Housing segment 68 may include safety shoulder 70 designed to catch rotor 16 if rotor 16 is disconnected from flex shaft 14 or if flex shaft 14 is disconnected from housing segment 64. Housing segment 68 may further include fluid bypass 72 to allow a fluid flow through inner bore 61 if rotor 16 engages safety shoulder 70.
Referring still to
As the fluid flow through stator 18 rotates rotor 16, flex shaft 14 and rotating valve segment 20 are rotated as torque is transmitted to these elements. Rotating valve segment 20 rotates relative to stationary valve segment 22, which cycles valve 12 between the open position and the restricted position in which fluid flow is limited to central passages 28, 34 of rotating and stationary valve segments 20, 22. The fluid flow restriction generates a pressure pulse or waterhammer that is transmitted upstream to the drill string above vibration assembly 10. The repeated pressure pulse generation causes a stretching and retracting in the drill string above vibration assembly 10, thereby facilitating vibration and easing the movement of the drill string through a wellbore. The vibration may reduce friction between an outer surface of the drill string and an inner surface of the wellbore.
In an alternate embodiment, the power section is formed of a turbine or any other hydraulic motor mechanism for generating torque with a fluid flow. The power section includes at least one rotor element configured to rotate with the fluid flow through the power section. The rotor element is operatively connected to the rotating valve segment, such that the rotating valve segment rotates with a rotation of the rotor.
In the embodiment illustrated in
Referring now to
With reference again to
Vibration assembly 130 may be secured within a drill string by threadedly connecting housing segment 62 to a first drill string segment and connecting housing segment 68 to a second drill string segment. A fluid may be pumped through an inner bore of the first drill string segment and into inner bore 61 of housing 60. With valve 132 in the open position, the fluid may flow through fluid passage 156 of rotating valve segment 146 and fluid passage 152 or 153 of stationary valve segment 148. The fluid flow may continue into inner bore 61 of housing 60 around flex line 138, around adapter 135, and around upper end 56 of rotor 16. As the fluid flow through stator 18 rotates rotor 16 (as described above), adapter 136, flex line 138, and rotating valve segment 146 are rotated as torque is transmitted to these elements. Rotating valve segment 146 rotates relative to stationary valve segment 148, which cycles valve 132 between the open position and the restricted position in which fluid flow through valve 132 is restricted. The fluid flow restriction generates a pressure pulse or waterhammer that is transmitted upstream to the drill string above vibration assembly 130. The repeated pressure pulse generation causes a stretching and retracting of the drill string initiating vibration in the drill string above vibration assembly 130, thereby facilitating and easing the movement of the drill string through a wellbore. The vibration may reduce friction between an outer surface of the drill string and an inner surface of the wellbore.
In one embodiment, vibration assembly 130 further includes a shock assembly, such as shock assembly 82. The shock assembly facilitates axial movement (in both directions) of the drill string above vibration assembly 130 relative to the drill string below vibration assembly 130.
In conventional vibration tools, a valve is positioned below a positive displacement power section. A pressure pulse generated in the valve of conventional vibration tools must be transmitted through the positive displacement power section before being transmitted to the drill string above. Because power sections are designed to convert hydraulic energy into mechanical energy, the positive displacement power sections of conventional vibration tools use a portion of the hydraulic energy of the pressure pulse generated by the valve below by converting an amount of the hydraulic energy into mechanical energy to overcome friction between the rotor and the stator, which is defined by the mechanical efficiency of the positive displacement power section itself. Additionally, the rubber or other flexible material of the stator in conventional vibration tools is compressed when in contact with the rotor, which dampens the magnitude of the pressure pulse as the pressure pulse is forced to travel through the positive displacement power section before being transmitted to the drill string above.
In the vibration assembly of the present disclosure, a valve is disposed above a power section. The pressure pulse generated by the valve is transmitted to the drill string above without traveling across the power section. In other words, the vibration assembly of the present disclosure transmits an unobstructed pressure pulse or waterhammer to the drill string or coiled tubing above. Accordingly, the vibration assembly of the present disclosure transmits the pressure pulse or waterhammer and vibration energy to the drill string above more efficiently than conventional vibration tools.
As used herein, “above” and any other indication of a greater height or latitude shall also mean upstream, and “below” and any other indication of a lesser height or latitude shall also mean downstream. As used herein, “drill string” shall include a series of drill string segments and a coiled tubing line.
While preferred embodiments have been described, it is to be understood that the embodiments are illustrative only and that the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalents, many variations and modifications naturally occurring to those skilled in the art from a review hereof.
