Patent Description:
A mud motor can be used to produce rotation of the drill bit that is localized at the distal end of the drill string, which allows for the creation of non-vertical sections of a well. Mud motors typically rely on energy stored as pressure in the drilling mud, which the mud motors convert to mechanical rotational energy. Further, other devices are sometimes used instead of mud motors in the bottom hole assembly, such as turbines, agitators, rotary steerable systems (RSS), to provide additional or alternative functionality to rotating the drill bit without rotating the entire drill string above the device.

Some rock formations can be difficult to drill through and can cause rapid wear of the drill bit as a consequence.

<CIT> describes a drilling pressure intensifying device comprising a housing, a shaft mounted for rotation in the housing, a ring gear having ring gear teeth carried by the shaft, at least one low pressure fluid conduit and at least one high pressure fluid conduit in the shaft, the at least one high pressure fluid conduit being disposed in fluid communication with the at least one low pressure fluid conduit. The device also includes a fluid pressure intensifying assembly including a stator having a stator interior in the at least one high pressure fluid conduit and stator teeth provided on the stator for meshing with the ring gear teeth of the ring gear and being drivingly engaged for rotation by the device shaft through the ring gear. A rotor is provided in the stator interior and drivingly engaged for rotation therewith.

The present invention resides in a drilling assembly as defined in claim <NUM> and a method of delivering a pressurized drilling fluid to a drill bit as defined in claim <NUM>.

The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any possible combinations of one or more of the associated listed items. It will be further understood that the terms "includes," "including," "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, as used herein, the term "if" may be construed to mean "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context.

<FIG> illustrates a wellsite system according to an embodiment. The wellsite can be onshore or offshore. In this example system, a borehole is formed in subsurface formations by rotary drilling in a manner that is well known. A drill string <NUM> is suspended within a borehole <NUM> and has a bottom hole assembly (BHA) <NUM> which includes a drill bit <NUM> at its lower end. A surface system <NUM> includes platform and derrick assembly positioned over the borehole <NUM>, the assembly including a rotary table <NUM>, kelly (not shown), hook <NUM>, and rotary swivel <NUM>. The drill string <NUM> is rotated by the rotary table <NUM> energized by means not shown, which engages the kelly (not shown) at the upper end of the drill string <NUM>. The drill string <NUM> is suspended from the hook <NUM>, attached to a traveling block (also not shown), through the kelly (not shown) and the rotary swivel <NUM> which permits rotation of the drill string <NUM> relative to the hook <NUM>. As is well known, a top drive system could be used instead of the rotary table system shown in <FIG>.

In the illustrated example, the surface system further includes drilling fluid or mud <NUM> stored in a pit <NUM> formed at the well site. A pump <NUM> delivers the drilling fluid to the interior of the drill string <NUM> via a port (not shown) in the swivel <NUM>, causing the drilling fluid to flow downwardly through the drill string <NUM> as indicated by the directional arrow <NUM>. The drilling fluid exits the drill string via ports (not shown) in the drill bit <NUM>, and then circulates upwardly through an annulus region <NUM> between the outside of the drill string <NUM> and the wall of the borehole <NUM>, as indicated by the directional arrows <NUM> and 135A. In this manner, the drilling fluid lubricates the drill bit <NUM> and carries formation cuttings up to the surface as it is returned to the pit <NUM> for recirculation.

The BHA <NUM> of the illustrated embodiment may include a measuring-while-drilling (MWD) tool <NUM>, a logging-while-drilling (LWD) tool <NUM>, a rotary steerable directional drilling system <NUM> and motor, and the drill bit <NUM>. It will also be understood that more than one LWD tool and/or MWD tool can be employed, e.g. as represented at <NUM>. Furthermore, a mud motor may be provided in lieu of the rotary steerable drilling system <NUM>.

The LWD tool <NUM> is housed in a special type of drill collar, as is known in the art, and can contain one or a plurality of known types of logging tools. The LWD tool <NUM> may include capabilities for measuring, processing, and storing information, as well as for communicating with the surface equipment. In the present example, the LWD tool <NUM> may any one or more well logging instruments known in the art, including, without limitation, electrical resistivity, acoustic velocity or slowness, neutron porosity, gamma-gamma density, neutron activation spectroscopy, nuclear magnetic resonance and natural gamma emission spectroscopy.

The MWD tool <NUM> is also housed in a special type of drill collar, as is known in the art, and can contain one or more devices for measuring characteristics of the drill string and drill bit. The MWD tool <NUM> further includes an apparatus <NUM> for generating electrical power to the downhole system. This may typically include a mud turbine generator powered by the flow of the drilling fluid, it being understood that other power and/or battery systems may be employed. In the present embodiment, the MWD tool <NUM> may include one or more of the following types of measuring devices: a weight-on-bit measuring device, a torque measuring device, a vibration measuring device, a shock measuring device, a stick slip measuring device, a direction measuring device, and an inclination measuring device. The power generating apparatus <NUM> may also include a drilling fluid flow modulator for communicating measurement and/or tool condition signals to the surface for detection and interpretation by a logging and control unit (e.g., a "controller") <NUM>.

As discussed herein, the BHA <NUM> may have a hydraulic amplifier assembly <NUM>. The hydraulic amplifier assembly <NUM> may be configured to increase a pressure of at least a portion of the drilling fluid that is received through the drill string and provided to the assembly <NUM>. Although the hydraulic amplifier assembly <NUM> is illustrated in <FIG> as coupled to the drill bit <NUM>, it is appreciated that the embodiments below describe various arrangements of the BHA <NUM> with the hydraulic amplifier assembly <NUM> in different positions within the BHA <NUM>. The hydraulic amplifier assembly <NUM> increases the pressure of a portion of the drilling fluid downhole to pressures above about <NUM> bar, <NUM> bar, <NUM> bar, or <NUM> bar, thereby reducing the components of the drill string that convey the pressurized drilling fluid to the drill bit. Through reducing the quantity of components and the length of lines conveying the pressurized drilling fluid to the drill bit, wear from the pressurized drilling fluid through the drill string may be reduced. Additionally, pressurizing a portion of the drilling fluid above a base pressure of the remainder may facilitate use of the remainder of the drilling fluid for other purposes (e.g., tool activation, hole cleaning) with reduced or eliminated modifications to other components of the BHA <NUM>.

<FIG> illustrates a simplified, side, cross-sectional view of a high pressure drilling assembly <NUM>, according to an embodiment. The assembly <NUM> may generally include a hydraulic amplifier assembly <NUM>, a top sub <NUM>, a driver <NUM>, a transmission section <NUM>, a bearing assembly <NUM>, and a shaft <NUM>. As shown, the hydraulic amplifier assembly <NUM> may be directly coupled to an uphole end of the top sub <NUM>, which is in turn uphole of the driver <NUM>, although this is merely one example of the position of this assembly <NUM> among many contemplated herein, and several other examples are described below.

The hydraulic amplifier assembly <NUM> may be configured to increase a pressure of a portion of the drilling fluid that is received through the drill string to the assembly <NUM>. For example, the hydraulic amplifier assembly <NUM> may include a hydraulic-over-hydraulic, master-slave cylinders. As such, fluid pressure may be used to drive a relatively large, master cylinder, which may drive a relatively small, slave cylinder that increases the pressure in a portion of the drilling fluid. The pressurized drilling fluid is routed through the assembly <NUM> and delivered to a drill bit coupled to the downhole end of the shaft <NUM>. The pressurized drilling fluid may be delivered at a pressure sufficient to water-jet cut a rock formation in which the drill bit is located. For example, the pressurized drilling fluid may be delivered at a pressure of from about <NUM> bar, about <NUM> bar, about <NUM> bar to about <NUM> bar, about <NUM> bar, or about <NUM> bar.

The pressurized drilling fluid may be routed from the hydraulic amplifier assembly <NUM> through the remainder of the assembly <NUM>, in one or more of several manners. For example, as indicated by lines in <FIG>, the fluid may be routed through a line <NUM> (e.g., high pressure tubing or pipe) extending along the centerline of the top sub <NUM>. In the illustrated embodiment, the driver <NUM> is a mud motor, but in other embodiments, the driver <NUM> may be a rotary steerable system (RSS), turbine, agitator, combinations thereof, etc. In the illustrated mud-motor embodiment, the driver <NUM> includes a rotor <NUM> and a stator <NUM>. The rotor <NUM> is rotatable relative to the stator <NUM>, as well as relative to the top sub <NUM>, by converting pressure from the drilling fluid flowing therethrough into rotation. Accordingly, the line <NUM> may extend through the rotor <NUM>, and may include a hydraulic coupling <NUM> to connect the portion of the line <NUM> in the stationary top sub <NUM> with the portion of the line <NUM> in the rotating rotor <NUM>.

The line <NUM> may extend through a drive shaft <NUM> (e.g., including universal coupling(s)) of the transmission section <NUM>, and through the shaft <NUM> extending through the bearing housing <NUM>. The shaft <NUM> may be connected to the drill bit (not shown), and thus the line <NUM> may be configured to feed the drilling fluid that is pressurized in the hydraulic amplifier assembly <NUM> to the drill bit from within the shaft <NUM>. In turn, the drill bit may include nozzles that direct the pressurized drilling fluid into the rock formation.

In another embodiment, as also depicted in <FIG>, a line <NUM> may extend from the hydraulic amplifier assembly <NUM> through the remainder of the high-pressure drilling assembly <NUM>. The line <NUM> may initially extend through the outer wall <NUM> of the top sub <NUM>, and through the stator <NUM> of the driver <NUM>. The line <NUM> may then turn radially inwards from an outer wall <NUM> of the transmission section <NUM>, e.g., at the bearing housing <NUM>, and proceed through an internal wall of the shaft <NUM>. For example, a keyway slot may be formed in the outside surface of the top sub <NUM> and the driver <NUM>, and a tubing or pipe positioned therein or a cover formed thereon to provide the conduit. In another embodiment, in the driver <NUM>, the line <NUM> may extend through the rubber of the stator <NUM>, be formed as a gunhole through the stator <NUM>, or the like. Where the line <NUM> turns radially inwards at the bearing housing <NUM>, the line <NUM> may, like the line <NUM>, include a hydraulic coupling that allows the line <NUM> to extend from a relatively stationary structure (the stator <NUM>) to a relatively rotating structure (the shaft <NUM>).

<FIG> illustrate a simplified, side, cross-sectional view of another high-pressure drilling assembly <NUM>, according to an embodiment. The high-pressure drilling assembly <NUM> may be similar to the assembly <NUM>, except that the hydraulic amplifier assembly <NUM> is positioned at the downhole end of the shaft <NUM>, interposed between the shaft <NUM> and the drill bit. In some embodiments, the hydraulic amplifier assembly <NUM> is directly coupled to the drill bit <NUM>. As such, the hydraulic amplifier assembly <NUM> may deliver pressurized drilling fluid directly to the drill bit, with the pressurized fluid line <NUM> and/or <NUM> being internal to the hydraulic amplifier assembly <NUM>.

<FIG> illustrates a simplified, side, cross-sectional view of another high-pressure drilling assembly <NUM>, according to an embodiment. The high-pressure drilling assembly <NUM> may be similar to the assembly <NUM>, except that the hydraulic amplifier assembly <NUM> is not directly coupled to the uphole end of the top sub <NUM>, but rather is integrated with the driver <NUM>. The high-pressure drilling assembly <NUM> may include the line <NUM> or the line <NUM> in order to deliver pressurized fluid through a portion of the drilling assembly <NUM> to the drill bit. Accordingly, in this example, rather than directly converting pressure of a portion of drilling fluid into energy to pressurize another portion of the drilling fluid, the hydraulic amplifier assembly <NUM> may be powered mechanically via a shaft <NUM> connected to the rotor <NUM> of the driver <NUM>. Thus, the rotor <NUM> rotating may be configured, in addition to rotating the drill bit, to drive the hydraulic amplifier assembly <NUM> to increase the pressure in the drilling fluid that is routed through line <NUM> or line <NUM>. The line <NUM> may, for example, extend through the shaft <NUM>. In another embodiment, the hydraulic amplifier assembly <NUM> may use pressure in a portion of the drilling fluid to increase the pressure of the drilling fluid delivered through the line <NUM> or <NUM>, similar to the high-pressure drilling assembly <NUM> of <FIG>.

<FIG> illustrates a simplified, side, cross-sectional view of another high-pressure drilling assembly <NUM>, according to an embodiment. The high-pressure drilling assembly <NUM> may be similar to the assembly <NUM>, except that the hydraulic amplifier assembly <NUM> is not directly coupled to the uphole end of the top sub <NUM>, but rather is integrated with the driver <NUM> and positioned downhole thereof. The assembly <NUM> may include the line <NUM> or the line <NUM> in order to deliver pressurized fluid through a portion of the drilling assembly <NUM> to the drill bit.

The hydraulic amplifier assembly <NUM> may be positioned in either of two general locations, as depicted and labeled as 202A, 202B, respectively. For example, the hydraulic amplifier assembly 202A may be positioned between the driver <NUM> and the transmission section <NUM>, and/or the hydraulic amplifier assembly 202B may be positioned in or coupled to the bearing assembly <NUM>. As both of these locations may be rotated by the driver <NUM>, the hydraulic amplifier assembly <NUM> may operate using the rotational energy to pressurize the drilling fluid in the line <NUM> or <NUM>, as mentioned above, or the drilling fluid in the line <NUM> or <NUM> may be pressurized using the pressure in the remaining drilling fluid. Furthermore, in the embodiment in which the hydraulic amplifier assembly <NUM> is located in the bearing housing <NUM>, the lines <NUM> or <NUM> may omit hydraulic couplings, as the location of the hydraulic amplifier assembly <NUM> is in a rotating structure. Similarly, in an embodiment in which the hydraulic amplifier assembly <NUM> is between the transmission section <NUM> and the driver <NUM> and the line <NUM> is employed, the line <NUM> may likewise omit hydraulic couplings <NUM> shown in <FIG>.

Claim 1:
A drilling assembly, comprising:
a hydraulic amplifier assembly (<NUM>) configured to increase a pressure of a drilling fluid so as to produce a pressurized drilling fluid;
a driver (<NUM>) that is driven by the pressure of the drilling fluid;
a bearing housing (<NUM>) coupled to the driver (<NUM>); and
a shaft (<NUM>) extending through the bearing housing (<NUM>), wherein the shaft (<NUM>) is driven to rotate by the driver (<NUM>),
a drill bit (<NUM>) coupled to a downhole end of the shaft (<NUM>) and configured to be rotated by the driver (<NUM>);
characterized in that the hydraulic amplifier assembly (<NUM>) is configured to deliver the pressurized drilling fluid to the drill bit (<NUM>),_wherein the hydraulic amplifier assembly (<NUM>) is coupled to the driver (<NUM>), such that the driver (<NUM>) is configured to drive the hydraulic amplifier assembly (<NUM>).