Apparatus and method for a hydraulic diaphragm downhole mud motor

A downhole motor to drill a wellbore including a pumping apparatus having a first chamber configured to receive a first fluid and a second fluid, and a first flexible diaphragm disposed with the first chamber configured to separate the first and second fluid, wherein the first flexible diaphragm is configured to transfer a hydraulic energy between the first fluid and the second fluid. In addition, the downhole motor includes a motor portion coupled to the pumping apparatus and configured to receive the second fluid and convert the hydraulic energy of the second fluid into a mechanical energy, thereby creating a torque. Further, the downhole motor includes a bit shaft coupled to the motor portion, configured to receive the torque from the motor portion and the first fluid from the pumping apparatus.

BACKGROUND OF DISCLOSURE

1. Field of the Disclosure

Embodiments disclosed herein relate generally to apparatus and methods for downhole drilling operations. More specifically, embodiments disclosed herein relate to a downhole hole mud motor.

2. Background Art

In the drilling of well bores in the oil and gas industry, it is common practice to use downhole motors to drive a drill bit through a formation. As used herein, a “downhole motor” may refer generally to any motor used in a well bore for drilling through a formation. These downhole motors may typically be driven by pumping drilling fluids (e.g., “mud”) from surface equipment downhole through the drill string. As such, this type of motor is commonly referred to as a mud motor. When in use, the drilling fluid may be forced from the surface through the motor portion of the mud motor, in which energy from the flow of the drilling fluid may be used to provide rotational force to a drill bit located below the mud motor. As used herein, a “motor portion” may refer to the portion of the downhole motor that generates torque. There are two primary types of mud motors: positive displacement motors (“PDM”) and turbine motors.

The first type of mud motor, PDM, may be used to convert the energy of high-pressure drilling fluid into rotational-mechanical energy to rotate the drill bit. An early example of a PDM is given in U.S. Pat. No. 4,187,918 (“Clark”). As shown in Clark, a PDM typically has a helical stator attached to a distal end of the drillstring. The PDM may also have an eccentric helical rotor that corresponds to the helical stator and is connected through a driveshaft to the remainder of a bottom hole assembly (“BHA”) therebelow. Drilling fluids may be pressurized to flow through the bore of the drillstring to engage the stator and rotor, thereby creating a resultant torque between the stator and the rotor. This torque may then be transmitted to the drill bit to rotate the drill bit. Historically, PDM's have been characterized as having a low-speed and high-torque when rotating the drill bit. Accordingly, PDM's may generally be best suited for use with roller cone and polycrystalline diamond compact (PDC) bits. However, the rotors of PDM's have been known to have eccentric motion, thereby creating large lateral vibrations that may damage other drill string components.

The second type of mud motor, the turbine motor, generally uses one or more turbine power sections to provide rotational force to a drill bit. Each power section may consist of a non-moving stator vane, and a rotor assembly comprising rotating vanes mechanically linked to a rotor shaft. These power sections are designed such that the vanes of the stator direct the flow of drilling fluid into corresponding rotor blades to provide rotation. The rotor shaft, which may be a single piece, or may comprise two or more connected shafts, such as a flexible shaft and an output shaft, then ultimately connects to and drives the drill bit. Thus, the high-speed drilling fluid flowing into the rotor vanes causes the rotor and the drill bit to rotate with respect to the stator housing. Historically, turbine motors have been characterized as having a high-speed and low-torque, when rotating the drill bit. Furthermore, because of the high speed, and because by design no component of the rotor moves in an eccentric path, the output of a turbine motor is typically smoother than the output of PDM's and considered appropriate for use with PDC bits drilling high compressive strength formations.

Drilling fluid, as used in oilfield applications, is typically pumped downhole through a bore of the drillstring at high pressure. Once downhole, the drilling fluid is pumped through the downhole mud motor, where the fluid is exposed to internal components of the downhole motor, such as bearings and seals. After the drilling fluid has passed through the downhole mud motor, the drilling fluid is then transferred to the drill bit and communicated to the well bore through a plurality of nozzles. Here the drilling fluid cools and lubricates the drill bit, in addition to cleaning drill cuttings away from cutting surfaces of the drill bit and the wellbore. The drilling fluid is then expelled to return to the surface through an annulus formed between the wellbore (i.e., the inner diameter of either the formation or a casing string) and the outer profile of the drillstring. Accordingly, the drilling mud returns to the surface carrying drill cuttings disposed therein. Because the drilling fluid is exposed to the internal components of the downhole motor, the chemical composition and viscosity of the drilling fluid must be carefully considered. The composition and viscosity may have a direct or indirect impact on the internal components of the downhole motor, such as reliability and maintainability.

Both the PDM and the turbine motor, discussed above, require the drilling fluid to be pumped from the surface and circulated through the motor portion of the downhole motor. Thus, the internal components of the PDM and the turbine motor are exposed to the drilling fluid and, therefore, may be affected by the viscosity and the composition of the drilling fluid. This exposure, as described above, may cause the internal components of the PDM and the turbine motor to wear down quickly. Further, this exposure may result in a less reliable and maintainable downhole motor.

Thus, there exists a need for a fluid driven downhole motor that is more reliable and maintainable.

SUMMARY OF DISCLOSURE

In one aspect, embodiments disclosed herein relate to a downhole motor for drilling a wellbore including a pumping apparatus having a first chamber configured to receive a first fluid and a second fluid, and a first flexible diaphragm disposed with the first chamber configured to separate the first and second fluid, wherein the first flexible diaphragm is configured to transfer a hydraulic energy between the first fluid and the second fluid, a motor portion coupled to the pumping apparatus and configured to receive the second fluid and convert the hydraulic energy of the second fluid into a mechanical energy, thereby creating a torque, and a bit shaft coupled to the motor portion, configured to receive the torque from the motor portion and the first fluid from the pumping apparatus.

In one aspect, embodiments disclosed herein relate to a method of operating a downhole motor including pumping a first fluid containing a hydraulic energy to the downhole motor, directing the flow of the first fluid into a first chamber of a pumping apparatus, transferring hydraulic energy from the first fluid to a second fluid through a first flexible diaphragm disposed in the first chamber, directing the flow of the second fluid from the pumping apparatus into a motor portion, allowing the second fluid to flow through the motor portion, wherein the motor portion is configured to transfer hydraulic energy of the second fluid into a mechanical energy, thereby creating torque, rotating a bit shaft with the torque generated from the motor portion, and directing the flow of the first fluid from the pumping apparatus to the bit shaft.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to a downhole drilling system. More specifically, select embodiments of the present disclosure relate to a hydraulic diaphragm downhole mud motor. The downhole motor of the present disclosure may be integrated into the downhole drilling system and driven by a fluid that is pumped therethrough. Further, the downhole motor of the present disclosure may be used to drill a wellbore by turning a drill bit.

Even more specifically, select embodiments relate to a downhole motor that is capable of using multiple types of fluids simultaneously. For example, in one embodiment a first fluid (such as drilling mud, or “mud fluid,” herein) may be used in conjunction with a second fluid (such as a hydraulic fluid).

Generally, select embodiments disclosed herein relate to a downhole motor having a diaphragm pump with at least two chambers. Each chamber has a diaphragm disposed therein configured to separate a first fluid from a second fluid. The first fluid is transferred downhole through a drill string to the downhole motor. The first fluid flows through the downhole motor to a drill bit that releases the first fluid into the wellbore. However, while flowing through the downhole motor, the first fluid does not flow through the motor portion of the downhole motor. Thus, the first fluid is not exposed to the internal components of the motor portion. As a result, the first fluid is a mud fluid or other drilling fluid known in the art that provides a means to clean the wellbore. The second fluid is disposed in the downhole motor and is circulated through the motor portion of the downhole motor. Thus, to prevent wear on the internal components of the downhole motor, the second fluid is a clean hydraulic fluid or other non-abrasive fluid known in the art. Those having ordinary skill in the art will appreciate that other fluid combinations may be used.

FIG. 1shows a cross-sectional view of a downhole motor100in accordance with embodiments of the present disclosure. Downhole motor100includes a pumping apparatus110, a motor portion140, and a bit shaft150. As shown inFIG. 1, the pumping apparatus110includes a first chamber112and a second chamber113. The first chamber112includes a first flexible diaphragm114disposed therein, and the second chamber113includes a second flexible diaphragm115disposed therein. The diaphragms114,115separate a second fluid118from a first fluid116that are both received by the chambers112,113of the pumping apparatus110.

In one embodiment, the diaphragms114,115may be cylindrical in shape and manufactured out of a flexible material, such as rubber, Teflon, or other materials known in the art. In alternate embodiments, other shapes, including regular and irregular shaped diaphragms may be used, such that the diaphragm may separate two fluids within a chamber112,113. Furthermore, the flexibility of the diaphragms114,115allows a transfer of hydraulic energy between the fluids116,118. For example, the pumping apparatus110may receive a first fluid116in the first flexible diaphragm114, while a second fluid118is disposed in the first chamber112, outside the first flexible diaphragm114. As the first fluid116fills the first flexible diaphragm114, a pressure within the diaphragm114increases, causing the diaphragm114to expand. During this expansion, the first flexible diaphragm114transfers hydraulic energy from the first fluid116to the second fluid118, while maintaining physical separation of the fluids116,118.

In the embodiment shown, the diaphragms114,115are positioned proximate a center annulus of the pumping apparatus110. This allows the diaphragms114,115to be closely aligned with the flow of the first fluid116entering the pumping apparatus110, thereby reducing hydraulic energy loss due to the redirection of the flow of the first fluid116. In an alternate embodiment, the diaphragms114,115may be positioned proximate inner circumference119of the pumping apparatus110.

In one embodiment of the present disclosure, the pumping apparatus may include an odd number of chambers and diaphragms, for example, five chambers with a diaphragm disposed in each chamber. An odd number of chambers may decrease the amount of vibrations generated by the downhole motor during operations. However, one skilled the art would appreciate that the motor may have an even number of chambers without departing from the scope of embodiments disclosed therein.

The pumping apparatus110further includes a valve system120having an upper valve122, an upper valve housing123, a lower valve124, a fluid housing130, and a shaft126. The valves122,124are coupled to the shaft126, which extends through the center annulus of the pumping apparatus110. The valves122,124may be coupled to the shaft126through the use of threads, bearings, or other attachment methods known in the art. The valves122,124are configured to control the flow of the first and second fluid116,118entering and exiting the pumping apparatus110. In one embodiment the valve system120may be directly connected to the bit shaft150or, in an alternate embodiment, the valve system120may be connected to another device (not shown) that turns the shaft126independently of the bit shaft150.

A component view of the valve system120in accordance with the embodiments of the present disclosure is shown inFIG. 6. As shown inFIG. 6, the upper valve122includes a top plate171and a bottom plate173both having a plurality of orifices175radially disposed about a central axis177. Each of the plates173,171are configured to rotate around the central axis177. As the bottom and top plate173,171rotate about the central axis177, an orifice175from the top plate171may align with an orifice175from the bottom plate173. This alignment may form a passageway allowing the first fluid116to flow through the upper valve122.

Further, the lower valve124includes a first plate172and a second plate174both having a plurality of orifices175radially disposed about the central axis177, similar to those of the upper valve122. However, the second plate174of the lower valve223also includes a plurality of bores176that are also radially disposed about the central axis177. Both plates172,174may be configured, similar to the plates171,173of the upper valve122, so as to rotate about the central axis177. An orifice175on the first plate172may be configured to align with an orifice175on the second plate174to form a passageway that will allow the first fluid116to flow through the lower valve124. Further, a bore176disposed on the second plate174may be configured to align with an opening in another component, such as the fluid housing130shown inFIG. 1, that will allow the second fluid118to flow trough the lower valve124.

As shown inFIG. 6, the valve system includes an upper and a lower valve having disk-shaped plates with a plurality of openings (e.g., orifices and bores) extending from the upper face to the lower face of each plate (e.g., top plate). In an alternate embodiment the valve system may include other type valve assemblies known in the art. For example, a cylinder type valve assembly720, as shown inFIG. 7may be used. Cylinder type valve assembly720includes an upper valve722and a lower valve724, each having a cylindrical shape and each valve having a plurality of openings extending through a wall of a cylinder. Further, the valve assembly720is configured to direct and control the flow of a first fluid and a second fluid, similar to the valve system shown inFIG. 1.

In one embodiment, the valve system120of the downhole motor100may be configured to be driven independently by, for example, a turbine blade in the first fluid116or a separate motor portion140. A sensor may be configured to transmit and receive a signal that is transferred between the sensor and a controller (not shown). The controller may be located at the surface of the well and used to control the flow rate of the first fluid116flowing through the downhole motor100. This control may result in the downhole motor100having the capability of running at a variety of torques and speeds.

Referring back toFIG. 1, the valves122,124may be configured to control which chamber (e.g., the first and second chambers112,113) the first and second fluid116,118enter and exit. For example, the upper valve122may be rotated to a position where an orifice175of the top plate171and an orifice175of the bottom plate173align above the first chamber112. While the orifices175of these plates171,173are at least partially aligned above the first chamber112, the first fluid116will flow into the first flexible diaphragm114of the first chamber112.

After the first diaphragm114fills, the lower valve124may be rotated to a position where a bore176of the second plate174aligns with a first channel of the fluid housing130below the first chamber112. While the bore176and the channel are at least partially aligned below the first chamber112, the second fluid118may flow out of the first chamber112and into the first channel of the fluid housing130.

Once the second fluid118has circulated through the motor portion140and into a second channel of the fluid housing130, the lower valve124may be rotated to a position where a bore176aligns with a second channel in the fluid housing130below the second chamber113. While the bore176is at least partially aligned with the second channel of the fluid housing130below the second chamber113, the second fluid118may flow out of the fluid housing130and into the second chamber113.

Following the second fluid118filling the second chamber113, the lower valve124may be rotated to a position where an orifice175of the first plate172and an orifice174of the second plate174align below the second chamber113. When the orifices175of these plates172,174are at least partially aligned below the second chamber113, the first fluid116will flow out of the second flexible diaphragm115and into an annular space of the fluid housing130.

The fluid housing130, as shown inFIG. 1, may be coupled to the pumping apparatus110and the motor portion140, using bolts, bearings, seals, or any other elements known in the art. As depicted inFIG. 1, the pumping apparatus110may be coupled to one end of the housing130, i.e., upper face, and the motor portion140may be coupled to the opposite end of the housing130, i.e., a lower face.

FIG. 3shows a close cross-sectional view of the housing130of the downhole motor100in accordance with the embodiments of the present disclosure. As shown inFIG. 3, the fluid housing130may include a first channel132and a second channel134. Each channel may extend the length of the housing130, thereby creating a passage way between the pumping apparatus110and the motor portion140. The channels132,134may be of various shapes and cross-sections, such as a cylindrical, square, elliptical, triangular, or others known in the art. These channels132,134are configured to transfer a second fluid118between the pumping apparatus110and the motor portion140. For example, the second fluid118exiting the first chamber112of the pumping apparatus110flows through the first channel132to the motor portion140. After the second fluid118has circulated through the motor portion140, the second fluid118exiting the motor portion140flows through the second channel134back into the second chamber113of the pumping apparatus110. One skilled in the art of drilling will appreciate that the fluid housing130may include additional fluid passages. For example, a fluid housing may include a first channel, a second channel, and a third channel, such that each channel is used to transport a fluid.

The motor portion140includes a motor valve142, and at least one thrust bearing (not shown). Additionally, the motor portion140may include, for example, a rotor and a stator, and other components known in the art. The motor valve142is coupled to the fluid housing130and controls the flow of the second fluid118entering and exiting the motor portion140of the downhole motor100. At least one thrust bearing may be disposed between the bit shaft150and the motor portion140to transfer torque from the motor portion140to the bit shaft150. The motor portion140is then driven by the second fluid118flowing therethrough. The second fluid118flows through the motor portion140, wherein hydraulic energy of the fluid118is converted into mechanical energy to turn the bit shaft150.

In an alternate embodiment, the motor valve142may be replaced with a set (2) of opposed check valves. In this embodiment, the check valves may operate independent from the valve system120, thereby allowing the valve system120to be driven independently, for example, by a separate motor portion140. At least one of the two check valves is configured to control the flow of the second fluid118entering the motor portion140, while the other check valve is configured to control the flow of the second fluid118exiting the motor portion140.

Referring back toFIG. 1, the fluid housing130also includes an annular space136. The annular space136may extend downward from the upper face some distance to a location above the lower face of the housing130. Further, the annular space136provides a passage way between the pumping apparatus110and the bit shaft150. For example, the first fluid116exiting the pumping apparatus flows into the annular space136of the fluid housing130. As the annular space136fills with the first fluid116, the first fluid116flows though an opening in the bit shaft150.

Finally, the bit shaft150, as shown inFIG. 1, includes an opening152that may be located near the upper end of the bit shaft150. The bit shaft150may extend from a location below the downhole motor100upward through the motor portion140and into the fluid housing130. More specifically, the upper end of the bit shaft150may be received by the annular space136of the fluid housing130. Further, the bit shaft150may be coupled to the motor portion140by any means know in the art, for example, at least one thrust bearing. Furthermore, the bit shaft150includes a channel154that may be configured to transfer the first fluid116to a lower distal end of the bit shaft150. For example, the first fluid116flowing out of the second chamber113may flow into the annular space136of the fluid housing130. As the annular space136fills with the first fluid, the first fluid will flow through the opening152at the upper end of the shaft into the channel154. The first fluid116may then continue to flow downward through the channel154within the bit shaft150to the lower distal end of the bit shaft150.

It should be understood that the downhole motor100, in accordance with the embodiments disclosed herein, may be incorporated into a drilling assembly. The drilling assembly may comprise of a drill string (not shown), the downhole motor100, a drill bit (not shown), and other components known in the art. Thus, the downhole motor100may be configured to be coupled to the drill string and the drill bit. One skilled in the art will appreciate that the downhole motor100may be used with pre-existing drill strings and drill bits. These pre-existing drill strings and drill bits may be coupled to the downhole motor100using attachment methods known in the art of drilling, for example, threaded connections, welding, and bearings.

During the operation of the downhole motor100, the first fluid116may be pumped downhole through the drill string to the downhole motor100. Once the fluid116reaches the downhole motor100, the upper valve122may be rotated to a position to allow the first fluid116into the first flexible diaphragm114of the first chamber112. The upper valve122is rotated at a predetermined speed. The predetermined speed may be dependent on the size of the wellbore, the type of formation, desired Rate of Penetration (ROP), and other factors known in the art.

As the first fluid116fills the first flexible diaphragm114, the first flexible diaphragm114expands. The expansion of the first flexible diaphragm114pressurizes the second fluid118also disposed in the first chamber112, thereby transferring hydraulic energy from the first fluid116to the second fluid118outside of the diaphragm114. The lower valve124may then be rotated to a position to allow the pressurized second fluid118to flow out of the first chamber112and into the first channel132of the fluid housing130.

The second fluid118may then be transferred through the first channel132to the motor portion140. The motor valve142may then allow the second fluid118from the first channel134to flow into the motor portion140. While the second fluid118flows through the motor portion140, the motor portion140converts the hydraulic energy of the second fluid118into mechanical energy, thereby creating torque. Further, the torque created by the motor portion140is transferred to the bit shaft150through at least one thrust bearing, which causes the bit shaft150to rotate.

After at least some of the second fluid118has passed through the motor portion140, the motor valve142may allow the second fluid118to flow into the second channel134of the fluid housing130. The lower valve124may then be rotated to a position to allow the second fluid118from the second channel134to flow into the second chamber113, outside the second flexible diaphragm115. As the second fluid118fills the second chamber113, the second flexible diaphragm115compresses. The compression of the second flexible diaphragm115pressurizes the first fluid116disposed in the second flexible diaphragm115, thereby transferring hydraulic energy from the second fluid118to the first fluid116. The lower valve124may then be rotated to a position to allow the pressurized first fluid116to flow out of the second flexible diaphragm115and into the annular space136of the fluid housing130. As the annular space136fills with the first fluid116, the first fluid116may be forced to flow through the opening152of the bit shaft150into the channel154. Finally, the channel154within the bit shaft150may transfer the first fluid116to the drill bit attached to the lower distal end of the bit shaft150.

The drill bit may include nozzles (not shown) or other components known in the art that will receive the first fluid116. These nozzles may release the first fluid116into a wellbore. One skilled in the art will appreciate that the first fluid116may be used to clean and cool the exterior surface of the drill bit. Further, the first fluid116may remove material, also known as cuttings, resulting from the drilling of a formation by the drill bit. The first fluid116along with the cuttings that were removed may then be transported upward through the wellbore.

Referring now toFIG. 2, the upper valve122is rotated to a position to allow the first fluid116to flow into the second flexible diaphragm115of the second chamber113. As the first fluid116fills the second flexible diaphragm115, the second flexible diaphragm115expands. The expansion of the first flexible diaphragm115pressurizes the second fluid118also disposed in the second chamber113, thereby transferring hydraulic energy from the first fluid116to the second fluid118outside of the diaphragm115. The lower valve124may then be rotated to a position to allow the pressurized second fluid118to flow out of the second chamber113and into the second channel134of the fluid housing130.

The second fluid118may then be transferred through the second channel134to the motor portion140. The motor valve142allows the second fluid118from the second channel134to flow into the motor portion140. While the second fluid118flows through the motor portion140, the motor portion140converts the hydraulic energy of the second fluid118into mechanical energy, thereby creating torque. Further, the torque created by the motor portion140is transferred to the bit shaft150through at least one thrust bearing, which causes the bit shaft150to rotate.

After at least some of the second fluid118has passed through the motor portion140, the motor valve142may allow the second fluid118to flow into the first channel132of the fluid housing130. The lower valve124may then be rotated to a position to allow the second fluid118from the first channel132to flow into the first chamber112, outside the first flexible diaphragm114. As the second fluid118fills the first chamber112, the first flexible diaphragm114compresses. The compression of the first flexible diaphragm114pressurizes the first fluid118disposed in the first flexible diaphragm114, thereby transferring hydraulic energy from the second fluid118to the first fluid116. The lower valve124may then be rotated to a position to allow the pressurized first fluid116to flow out of the first flexible diaphragm114and into the annular space136of the fluid housing130. As the annular space136fills with the first fluid116, the first fluid116may be forced to flow through the opening152of the bit shaft150into the channel154. Finally, the channel154within the bit shaft150may transfer the first fluid116to the drill bit attached to the lower distal end of the bit shaft150.

One skilled in the art will understand that the flow of the first fluid116into the downhole motor100may be alternated between the first chamber112and the second chamber113, thereby allowing the drill bit to be continuously turned. Further, one skilled in the art would understand that the operation of the downhole motor100may start with the flow of the first fluid116entering the first chamber112or the second chamber113. Furthermore, in embodiments where the downhole motor includes three or more chambers, the flow of the first and second fluid may be alternated between one or more chambers.

Referring now toFIG. 4, a cross-sectional view of a downhole motor200in accordance with embodiments of the present disclosure including a pumping apparatus210, a motor portion240, and a bit shaft250. The pumping apparatus210includes chambers212,213and flexible diaphragms214,215disposed therein. Flexible diaphragms214,215may be similar to those shown inFIG. 1and discussed above. In this embodiment the flexible diaphragms214,215of the pumping apparatus210receive the second fluid218. Further, the chambers212,213of the pumping apparatus210may include a plurality of upper openings and a plurality of lower openings that provide fluid communication between the chambers212,213and a center annulus of the pumping apparatus210.

Additionally, the pumping apparatus210may include a valve system220, similar to that shown inFIG. 1, including an upper valve222, a lower valve224and a shaft226. However, the upper and lower valves222,224may include a plurality of upper and lower openings, respectively, that extend through the shaft226. Similar toFIG. 1, the upper valve222and lower valve224may be configured to control the flow of the first fluid218entering and exiting the pumping apparatus210. However, instead of directing the first fluid216into a fluid housing230, as shown inFIG. 1, the valve system220may direct the first fluid216into the shaft226. The shaft226is configured to transfer the first fluid216to the bit shaft250. For example, as the bit shaft226rotates, an upper opening of the upper valve222aligns with an upper opening (not shown) in the chambers212,213and allows the first fluid216to alternatingly enter the chambers212,213. Furthermore, as the bit shaft226rotates, a lower opening of the lower valve224aligns with a lower opening (not shown) in the chambers212,213and allows the first fluid216to alternatingly exit the chambers212,213and flow into the a channel228of the shaft226. Finally, the channel228of the shaft226may transport the first fluid to the bit shaft250coupled to the end of the shaft226. The first fluid216transported to the bit shaft250may further be transported through the bit shaft250to a drill bit attached to the lower distal end of the bit shaft250.

The motor portion240, as shown inFIG. 4, includes a motor valve242and at least one thrust bearing (not shown). The motor portion240may be configured similar to the motor portion140discussed above with reference toFIG. 1. However, as shown inFIG. 4, the second fluid218may be transferred directly from the chambers212,213to the motor portion240, instead of flowing through a channel of a fluid housing. In addition, the second fluid218may be transferred directly from the motor portion240back to the chambers212,213, instead of flowing through a channel of a fluid housing.

The bit shaft250, as shown inFIG. 4, may be coupled to the motor portion240by means of a thrust bearing, similar to the bit shaft shown inFIG. 1. Further, like the bit shaft150shown inFIG. 1, the bit shaft250shown inFIG. 4includes a channel256that is configured to receive and transfer the first fluid216to the drill bit attached to the lower distal end of the bit shaft250. However, the channel256of bit shaft250inFIG. 4may receive the fluid216directly from pumping apparatus210, rather then from the annular space within the fluid housing, as shown inFIG. 1.

Referring still toFIG. 4, the downhole motor200is incorporated within a drilling assembly used to drill a formation, similar to the downhole motor100shown inFIG. 1. In operating this drilling assembly the downhole motor200is configured to receive a first fluid216from the drill string. The upper valve222is rotated to a position to allow the first fluid216into the first chamber212of the pumping apparatus210. The valve system220is rotated at a predetermined speed. The predetermined speed may be dependent on the size of the wellbore, the type of formation, desired Rate of Penetration (ROP), and other factors known in the art.

As the first fluid216fills the first chamber212, the first flexible diaphragm214compresses. The compression of the first flexible diaphragm214pressurizes the second fluid218disposed in the first flexible diaphragm214, thereby transferring hydraulic energy from the first fluid216outside of the diaphragm214to the second fluid218. The motor valve242may then be opened to allow the pressurized second fluid218to flow out of the first flexible diaphragm214and into the motor portion240.

While the second fluid218flows through the motor portion240, the motor portion240may convert the hydraulic energy of the second fluid218into mechanical energy, thereby creating torque. Further, the torque created by the motor portion240is transferred to the bit shaft250through at least one thrust bearing, which causes the bit shaft250to rotate.

After at least some of the second fluid218has passed through the motor portion240, the motor valve242may direct the second fluid218to flow into the second flexible diaphragm215of the second chamber213. As the second fluid218fills the second flexible diaphragm215, the second flexible diaphragm215expands. The expansion of the second flexible diaphragm215pressurizes the first fluid216disposed in the second chamber213, thereby transferring hydraulic energy from the second fluid218to the first fluid216outside the second flexible diaphragm215. The lower valve224may then be rotated to a position to allow the pressurized first fluid216to flow out of the second chamber213and into the channel228of the shaft226. The channel228of the shaft226then transfers the first fluid216to the channel256of the bit shaft250. Finally, the channel256of the bit shaft250transfers the first fluid216to the drill bit attached to the lower distal end of the bit shaft250. The drill bit may be configured similar to the drill bit discussed above with reference toFIG. 1.

Referring now toFIG. 5, the upper valve222is rotated to a position to allow the first fluid216into the second chamber213of the pumping apparatus210. As the first fluid216fills the second chamber213, the second flexible diaphragm215will compress. The compression of the second flexible diaphragm215will pressurize the second fluid218disposed in the second flexible diaphragm215, thereby transferring hydraulic energy from the first fluid216outside of the diaphragm215to the second fluid218. The motor valve242may then allow the pressurized second fluid218to flow out of the second flexible diaphragm215and into the motor portion240.

While the second fluid218flows through the motor portion240, the motor portion240may convert the hydraulic energy of the second fluid218into mechanical energy, thereby creating torque. Further, the torque created by the motor portion240is transferred to the bit shaft250through at least one thrust bearing, which causes the bit shaft250to rotate.

After at least some of the second fluid218has passed through the motor portion240, the motor valve242may direct the second fluid218to flow into the first flexible diaphragm214of the first chamber212. As the second fluid218fills the first flexible diaphragm214, the first flexible diaphragm214expands. The expansion of the first flexible diaphragm214pressurizes the first fluid216disposed in the first chamber212, thereby transferring hydraulic energy from the second fluid218to the first fluid216outside the first flexible diaphragm214. The lower valve224may then be rotated to a position to allow the pressurized first fluid216to flow out of the first chamber212and into the channel228of the shaft226. The channel228of the shaft226then transfers the first fluid216to the channel256of the bit shaft250. Finally, the channel256of the bit shaft250transfers the first fluid216to the drill bit attached to the lower distal end of the bit shaft250.

One skilled in the art will understand that the flow of the first fluid216into the downhole motor200may be alternated between the first chamber212and the second chamber213, thereby allowing the drill bit to be continuously turned. Further, one skilled in the art will understand that the operation of the downhole motor200may start with the flow of the first fluid216entering the first chamber212or the second chamber213. Furthermore, in embodiments where the downhole motor includes three or more chambers, the flow of the first and second fluid may be alternated between one or more chambers.

Embodiments of the present disclosure may include one or more of the following advantages. Downhole motors found in accordance with one or more embodiments may use combinations of fluids i.e. (drilling mud and hydraulic fluid) to increase the life and reliability of the downhole motor. While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.