Patent Description:
Some embodiments disclosed herein are directed to a flow pulsing system according to the claims.

Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed embodiments.

For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:.

The following discussion is directed to various exemplary embodiments. However, one of ordinary skill in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to. " Also, the term "couple" or "couples" is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection of the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms "axial" and "axially" generally mean along or parallel to a given axis (e.g., central axis of a body or a port), while the terms "radial" and "radially" generally mean perpendicular to the given axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis.

As previously described above, a flow pulsing system, otherwise referred to herein as an agitator, may be used along a drill string to introduce a pressure pulse or pressure wave within a tubular of the drill string. A flow pulsing system may be used alone or with other components to provide drilling benefits including enhanced tool face control, improved drilling efficiency, and may be used to introduce oscillations of the drill string. More particularly, one such additional component used with the flow pulsing system, may be a shock tool, which harnesses the pressure pulses from the flow pulsing system to induce oscillations along the longitudinal axis of the drill string. In some applications, such drill string oscillations may provide reduced friction within a borehole and may allow for extended drill string lengths. To operate the flow pulsing system, pumping pressure is required from the drilling rig, to overcome pressure drops across the flow pulsing system, thus it may be desirable to provide a flow pulsing system which may be selectively activated only once the drill string encounters downhole conditions where it is needed. Additionally, it may also be desirable to operate the flow pulsing system at a frequency and magnitude which is adjustable, which then allows for less overall pressure drop. Further, it may also be desirable to have a flow pulsing system which may be deactivated when it is no longer needed or deactivated and reconfigured to provide a modified pressure pulse which is better suited for yet another section of wellbore drilling. In addition to drill strings, the flow pulsing apparatus can be used on other downhole work or tubular strings.

Accordingly, embodiments disclosed herein include systems and methods for using a flow pulsing system which may be selectively engaged after wellbore drilling has begun, and while the drill string is disposed within the wellbore. Additionally, embodiments disclosed herein include systems and methods to selectively adjust the frequency and magnitude of the flow pulsing system, as well as systems and methods to selectively disengage and/or reconfigure the frequency and magnitude of the flow pulsing system after its use within the wellbore. Further, systems and methods disclosed herein provide valve ports which may be operated between a fully open, a partially open, and a fully closed position which may provide an improved pressure pulse response. Still further, systems and methods disclosed herein resist clogging of the flow pulsing system when materials are introduced into the wellbore, such as loss circulation materials.

Referring to <FIG>, a flow pulsing system <NUM> is shown coupled to a first sub <NUM> and a second sub <NUM>, each aligned along axis <NUM>. Flow pulsing system <NUM> includes a housing <NUM> and comprises an activation section <NUM>, a rotor section <NUM>, and a valve section <NUM>. Generally speaking flow pulsing system <NUM> is a tubular assembly which may be installed along any segment of a drill string within a wellbore (not shown). Exemplary connections along a first end <NUM> of first sub <NUM> and a second end <NUM> of second sub <NUM> are shown, which may each be modified as necessary to adapt with a particular drill string. Similarly, second end <NUM> of first sub <NUM> (<FIG>) and first end <NUM> of second sub <NUM> (<FIG>) may also be modified as needed to adapt with housing <NUM> and flow pulsing system <NUM>.

Referring to <FIG>, activation section <NUM> is shown in more detail, which may be used within flow pulsing system <NUM>. Activation section <NUM> comprises an axis <NUM> which is generally aligned with axis <NUM> of flow pulsing system <NUM>, an axis <NUM> which is offset from axis <NUM>, a screen <NUM>, and a nozzle <NUM> installed within a dart <NUM>. More particularly, housing <NUM> has a first end <NUM> and a second end <NUM> (shown in <FIG>) opposite first end <NUM>, and a bore <NUM> concentric with housing <NUM>, which both extend along axis <NUM> between ends <NUM>, <NUM>. Screen <NUM> is positioned along axis <NUM> proximate first end <NUM>, while nozzle <NUM> and dart <NUM> are positioned along axis <NUM> at a position between screen <NUM> and second end <NUM>.

Referring to <FIG>, rotor section <NUM> is shown in more detail, which comprises a rotor <NUM> aligned with axis <NUM> and a stator <NUM> aligned with axis <NUM>. In general, rotor <NUM> and stator <NUM> are tubular members housed within bore <NUM> with rotor <NUM> positioned at least partially within stator <NUM>. More particularly, stator <NUM> includes a first end <NUM> and a second end <NUM> opposite first end <NUM> and includes a radially inner surface <NUM> which extends between ends <NUM>, <NUM>. Stator <NUM> is coupled to housing <NUM> within bore <NUM> at a position between ends <NUM>, <NUM> and comprises a plurality of lobe cavities <NUM> axially spaced apart along radially inner surface <NUM>. The plurality of lobe cavities <NUM> results in the diameter of inner surface <NUM> sequentially expanding and contracting along the length of stator <NUM>. Rotor <NUM> is also a tubular member comprising a first end <NUM>, a second end <NUM> opposite first end <NUM>, a body <NUM>, and a bore <NUM>. Body <NUM> and bore <NUM> are each aligned with axis <NUM>, and extend between ends <NUM>, <NUM>. Rotor <NUM> further includes a lobe <NUM> extending radially outward from body <NUM>, with lobe <NUM> arranged in a generally helical manner along axis <NUM> and extending between ends <NUM>, <NUM>. When viewed in cross-section as shown in <FIG>, the helical pitch is selected such that a full <NUM>-degree revolution of lobe <NUM> about axis <NUM> coincides with the distance between lobe cavities <NUM>. As described, a single continuous lobe <NUM> is shown in this embodiment, however other embodiments may use multiple lobes arranged helically or may use multiple separate lobes which are not formed helically. In some embodiments, rotor <NUM> may have one less lobe <NUM> than the quantity of lobe cavities <NUM> along stator <NUM>. In all instances, lobes <NUM> may be referred to as separate lobes, when viewed in cross-section as a short hand for discussing the rotor <NUM> geometry. For example, in <FIG>, rotor <NUM> includes eleven lobes <NUM>. The relative dimensions of radially inner surface <NUM>, lobe cavities <NUM>, and lobe <NUM> are selected such that rotor <NUM> may be rotatably disposed within stator <NUM>. The radial clearance between lobe <NUM> and lobe cavity <NUM> defines cavity <NUM>.

Referring to <FIG>, valve section <NUM> is shown in more detail, which comprises components aligned with axis <NUM> of rotor <NUM> and components aligned with axis <NUM> which is generally aligned with axis <NUM> of flow pulsing system <NUM>. In general, the components aligned with axis <NUM> are coupled to rotor <NUM> and thus move with rotor <NUM> within housing <NUM>, while components aligned with axis <NUM> remain stationary relative to housing <NUM> and second sub <NUM>. More particularly, valve section <NUM> components aligned with axis <NUM> comprise oscillating valve adapter <NUM> and oscillating valve port section <NUM>. Additionally, valve section <NUM> components aligned with axis <NUM> comprise stationary valve port section <NUM> and stationary valve adapter <NUM>.

Referring to <FIG>, screen <NUM> is shown in more detail and comprises axis <NUM>, first end <NUM>, and second end <NUM> opposite first end <NUM>. Additionally, screen <NUM> comprises a coupling surface <NUM> extending along axis <NUM> from first end <NUM>, a screen housing <NUM> extending along axis <NUM> from second end <NUM>, and a body <NUM> extending therebetween. In some embodiments coupling surface <NUM> includes threads and has a smaller diameter than body <NUM>, and annular shoulder <NUM> creates a radial transition therebetween. Also, flats <NUM> may be provided along body <NUM> to allow torque application to the threads of coupling surface <NUM>. Bore <NUM> extends from first end <NUM>, passing within coupling surface <NUM> and body <NUM>, while inner surface <NUM> extends from second end <NUM> and passes within screen housing <NUM> to intersect bore <NUM>. Chamfer <NUM> transitions between inner surface <NUM> and bore <NUM>, while chamfer <NUM> is included along bore <NUM> at first end <NUM>. Screen housing <NUM> and inner surface <NUM> are generally frustoconical in shape, having a larger inlet diameter <NUM> proximate first end <NUM> than an outlet diameter <NUM> at second end <NUM>. Screen housing <NUM> additionally includes screen elements or slots <NUM> which pass through screen housing <NUM>. In this embodiment, screen elements <NUM> include a plurality of elongated passages which are distributed circumferentially about axis <NUM>, the elongated passages each having a long axis which is aligned with axis <NUM>. However, other embodiments may include differently shaped passages within screen element <NUM> which are arranged differently. (e.g., for example a plurality of circular passages extending radially relative to axis <NUM>).

Referring to <FIG>, dart <NUM> is shown in more detail and is generally symmetric relative to axis <NUM>. More particularly, dart <NUM> comprises a first end <NUM>, a second end <NUM> opposite first end <NUM>, and a plurality of features extending axially along axis <NUM>, including a head <NUM> extending from first end <NUM>, a neck <NUM> extending from head <NUM>, a first radially outer guide section <NUM> proximate neck <NUM>, a second radially outer guide section <NUM> proximate second end <NUM>, and a frustoconical tip <NUM> which narrows towards second end <NUM>. In this embodiment, head <NUM> has a larger diameter than neck <NUM>, and thus creates a shoulder <NUM> therebetween. Additionally, first radially outer guide section <NUM> and second radially outer guide section <NUM> have larger diameters than the surrounding sections of dart <NUM> and thus include various diameter transitions. More particularly, in this embodiment, chamfer type transitions are used and include transitions <NUM>, <NUM>, and <NUM>. For reasons that will be more apparent in subsequent descriptions, first radially outer guide section <NUM> and second radially outer guide section <NUM> are spaced apart along axis <NUM> and a relief <NUM>, having a reduced diameter, is provided therebetween. Additionally, first radially outer guide section <NUM> further includes a gland <NUM> disposed along its outer cylindrical surface and accepts a ring <NUM> (e.g. such as an O-ring) therein.

With respect to the inner surfaces of dart <NUM>, dart <NUM> further comprises a bore <NUM> extending from second end <NUM> into neck <NUM>, an inner coupling surface <NUM> extending from first end <NUM>, and a second bore <NUM> extending therebetween. In this embodiment, inner coupling surface <NUM> is threaded and has a larger diameter than second bore <NUM>, thus a shoulder <NUM> is formed therebetween.

Referring still to <FIG>, nozzle <NUM> is shown installed within the first end <NUM> of dart <NUM>. More specifically, nozzle <NUM> is axially symmetric about axis <NUM> and comprises a first end <NUM>, a second end <NUM> opposite first end <NUM>, and an outer coupling surface <NUM> extending between ends <NUM>, <NUM>. Nozzle <NUM> further comprises drive <NUM> extending from first end <NUM> and an inner nozzle profile <NUM> which extends between ends <NUM>, <NUM>. More particularly, inner nozzle profile <NUM> includes an inlet <NUM> at first end <NUM> and an outlet <NUM> at second end <NUM>. In this embodiment, inlet <NUM> has a smaller diameter than outlet <NUM> and thus may be considered a diffusing nozzle wherein a fluid passing from inlet <NUM> to outlet <NUM> would experience a decrease in flowrate and an associated increase in pressure. However, in other embodiments inlet <NUM> may be provided with an equal or larger diameter than outlet <NUM>. The diameter of inlet <NUM>, outlet <NUM>, and the shape of inner nozzle profile <NUM> will be offered in various combinations and sizes, as the fluid flow through nozzle <NUM> will influence the flow within flow pulsing system <NUM> along various sections, as will be discussed more fully below.

When nozzle <NUM> is installed within dart <NUM>, outer coupling surface <NUM> of nozzle <NUM> couples with inner coupling surface <NUM> of dart <NUM>. Drive <NUM> may be used to apply torque to thread the segments together until second end <NUM> of nozzle <NUM> abuts with shoulder <NUM> of dart <NUM>. Seals <NUM> (e.g., such as O-ring seals) may be provided along second end <NUM> to prevent fluid leakage around the perimeter of nozzle <NUM>, and/or alternative seals <NUM> (not shown) may be provided along other sections of nozzle <NUM> as needed (e.g., proximate first end <NUM> of nozzle <NUM>).

Referring to <FIG>, activation section <NUM> is shown in the deactivated condition or position, wherein dart <NUM> is not positioned within rotor <NUM>. First sub <NUM> is shown coupled to housing <NUM> and to screen <NUM>, with each aligned along axis <NUM>. More particularly, first sub <NUM> includes an outer coupling surface <NUM> extending from second end <NUM>, which couples with inner coupling surface <NUM> of housing <NUM>. A shoulder <NUM> on first sub <NUM> abuts with first end <NUM> of housing <NUM> to limit the axial position therebetween, while a seal <NUM> provides bore sealing therebetween. First sub <NUM> further includes an inner coupling surface <NUM> which extends within first sub <NUM> from second end <NUM>. Screen <NUM> couples with first sub <NUM> as coupling surface <NUM> engages inner coupling surface <NUM>, and the axial position therebetween is established as annular shoulder <NUM> of screen <NUM> abuts second end <NUM> of first sub <NUM>. As previously described, stator <NUM> is coupled within bore <NUM> of housing <NUM> at a fixed position, while rotor <NUM> is housed within stator <NUM>. First end <NUM> of rotor <NUM> is placed proximate to second end <NUM> of screen <NUM> and in some instances makes abutting contact therewith.

Referring to <FIG> and <FIG>, oscillating valve <NUM> is shown which comprises oscillating valve adapter <NUM> and oscillating valve port section <NUM>. Generally speaking, oscillating valve port section <NUM> fits within oscillating valve adapter <NUM> to form oscillating valve <NUM>. More particularly, oscillating valve adapter <NUM> comprises a first end <NUM>, a second end <NUM> opposite first end <NUM> along axis <NUM>, a coupling surface <NUM> extending from first end <NUM>, a body <NUM> extending from second end <NUM>, and an outer shoulder <NUM> extending radially therebetween. In some embodiments, coupling surface <NUM> may include threads. Additionally, thru bore <NUM> extends along axis <NUM> from first end <NUM> to meet with a second bore <NUM> which extends along axis <NUM> from second end <NUM>. Second bore <NUM> is a blind hole which terminates within body <NUM> to form inner shoulder <NUM>.

Oscillating valve port section <NUM> comprises a first end <NUM>, a second end <NUM> opposite first end <NUM> along axis <NUM>, and a body <NUM> which extends between ends <NUM>, <NUM>. More specifically, body <NUM> extends from first end <NUM> with a constant diameter along a first region and then flares into an increased diameter proximate second end <NUM>. Oscillating valve port section <NUM> further comprises a bore <NUM> extending along axis <NUM> from first end <NUM>, which meets with central port <NUM>, which extends along axis <NUM> from second end <NUM>. Transition <NUM> is provided between bore <NUM> and central port <NUM>, and in this embodiment is formed in a frustoconical shape which reduces in diameter proximate second end <NUM>. Orifice <NUM> is formed as a through hole in body <NUM>, which extends into bore <NUM> at an angle relative to axis <NUM>. In some embodiments, orifice <NUM> will be angled towards second end <NUM> (e.g., with radially inner portions positioned closer to second end <NUM>), with portions of orifice <NUM> extending along transition <NUM>. Oscillating valve ports <NUM> extend from second end <NUM> and include an inlet <NUM> which extends to a radially outer surface of body <NUM>. In some embodiments, oscillating valve port <NUM> extends axially relative to axis <NUM>, while inlet <NUM> extends at an angle towards second end <NUM> (e.g., with radially inner portions positioned closer to second end <NUM>). As best shown in <FIG>, a plurality of oscillating valve ports <NUM> and a plurality of inlets <NUM> may be provided along second end <NUM>, and may be distributed circumferentially relative to axis <NUM>. For example, in this embodiment, four oscillating valve ports <NUM> and four inlets <NUM> are distributed at ninety degree intervals.

To form oscillating valve <NUM>, oscillating valve port section <NUM> is coupled to oscillating valve adapter <NUM>. More particularly, body <NUM> of oscillating valve port section <NUM> is fit within second bore <NUM> of oscillating valve adapter <NUM>, with first end <NUM> of oscillating valve port section <NUM> abutting inner shoulder <NUM> of oscillating valve adapter <NUM>. In some embodiments, the fit between second bore <NUM> and body <NUM> may be a press fit, which requires relative heating between the surfaces during the assembly makeup.

Referring to <FIG> and <FIG> stationary valve <NUM> is shown which comprises stationary valve port section <NUM> and stationary valve adapter <NUM>. Generally speaking, stationary valve port section <NUM> fits within stationary valve adapter <NUM> to form stationary valve <NUM>. More particularly, stationary valve port section <NUM> comprises a first end <NUM>, a second end <NUM> opposite first end <NUM> along axis <NUM>, and a body <NUM> extending between ends <NUM>, <NUM>. In the embodiment shown, body <NUM> has a constant diameter section proximate second end <NUM>, and then has an increased diameter along first end <NUM>. Additionally, central port <NUM> extends within body <NUM> from first end <NUM> and meets with taper <NUM> which extends from second end <NUM>. More specifically, taper <NUM> has a frustoconical profile which increases in diameter at positions axially away from second end <NUM>. Stationary valve ports <NUM> are provided along first end <NUM> at positions offset from axis <NUM> which are distributed circumferentially relative to axis <NUM> (as best shown in <FIG>), and extend into body <NUM> to meet with the inner cavity formed by taper <NUM>. In this embodiment, four stationary valve ports <NUM> are provided and are distributed at ninety degree intervals. Stationary valve ports <NUM> may extend into body <NUM> in a direction parallel to axis <NUM> or may extend at an angle. For example, stationary valve ports <NUM> may converge towards axis <NUM> at positions proximate to second end <NUM>.

Stationary valve adapter <NUM> comprises a first end <NUM>, a second end <NUM> opposite first end <NUM> along axis <NUM>, a body <NUM> extending from first end <NUM>, a seal receiving portion <NUM> extending from second end <NUM>, and a coupling surface <NUM> extending therebetween. More particularly, body <NUM>, coupling surface <NUM>, and seal receiving portion <NUM> are each generally cylindrical features, symmetric about axis <NUM>, which are connected with radially oriented shoulders. Shoulder <NUM> is formed between body <NUM> and coupling surface <NUM>, while shoulder <NUM> is formed between coupling surface <NUM> and seal receiving portion <NUM>. Annular grooves <NUM> (accepting seals <NUM>) are formed within seal receiving portion <NUM> proximate to second end <NUM>, and are axially spaced along axis <NUM>. In some embodiments, coupling surface <NUM> may include threads. Additionally, first bore <NUM> extends along axis <NUM> from first end <NUM> and terminates within body <NUM> to form inner shoulder <NUM>, while second bore <NUM> extends along axis <NUM> from second end <NUM> to intersect first bore <NUM>.

To form stationary valve <NUM>, stationary valve port section <NUM> is coupled to stationary valve adapter <NUM>. More particularly, body <NUM> of stationary valve port section <NUM> is fit within first bore <NUM> of stationary valve adapter <NUM>, with second end <NUM> of stationary valve port section <NUM> abutting inner shoulder <NUM> of stationary valve adapter <NUM>. In some embodiments, the fit between first bore <NUM> and body <NUM> may be a press fit, which requires relative heating between the surfaces during the assembly makeup.

Referring to <FIG> and <FIG>, valve section <NUM> houses oscillating valve <NUM> and stationary valve <NUM>, within bore <NUM> of housing <NUM>. As previously described generally, valve section <NUM> includes axis <NUM>, which coincides with the movable rotor <NUM> and a stationary axis <NUM> which is concentric with housing <NUM> and second sub <NUM>. More particularly, oscillating valve <NUM> is aligned with axis <NUM> as it couples to rotor <NUM>, while stationary valve <NUM> is aligned with axis <NUM> as it couples to second sub <NUM>. In this manner, the offset of axis <NUM> from axis <NUM>, and any other offset axes, may be referred to as "eccentric," such term also applying to components such as oscillating valve <NUM> and stationary valve <NUM> that are axially offset relative to each other. Coupling surface <NUM> of oscillating valve <NUM>, couples with oscillating valve coupling surface <NUM> of rotor <NUM> as second end <NUM> of rotor <NUM> abuts with outer shoulder <NUM> of oscillating valve <NUM>.

Stationary valve <NUM> fits partially within second sub <NUM> proximate to first end <NUM> of second sub <NUM>. More particularly, seals <NUM> of stationary valve <NUM> seal along bore <NUM> of second sub <NUM>, as stationary valve <NUM> and second sub <NUM> engage along surfaces <NUM>, <NUM> and abut along first end <NUM> and shoulder <NUM>.

The flat faces along second end <NUM> of oscillating valve <NUM> and first end <NUM> of stationary valve <NUM>, abut and generally seal during operations as rotor <NUM> applies thrust forces along axis <NUM>. Additionally, as rotor <NUM> rotates within stator <NUM>, the rotor also undergoes a nutating motion, wherein axis <NUM> moves in an elliptical or orbital pattern relative to axis <NUM> based on eccentricity of rotor <NUM> and the interacting lobes224 and lobe cavities <NUM>. Given this combination of thrust and nutating motion imparted by rotor <NUM>, sliding occurs at the flat abutting faces of valves <NUM>, <NUM> as the oscillating valve <NUM> also nutates relative to stationary valve <NUM>. As a shorthand herein, the nutating motion of components within flow pulsing system <NUM>, may alternatively be referred to as "rotating". Additionally, one having ordinary skill in the art will appreciate that the nutating motion may be modified (for example, by varying the dimensions of rotor <NUM> and stator <NUM>) without departing from the principle of operation disclosed herein. In some embodiments, the path of axis <NUM> will form a hypocycloid as rotor <NUM> rotates within stator <NUM>.

Referring to <FIG>, activation section <NUM> is shown in a deactivated condition or position, wherein dart <NUM> is not installed within rotor <NUM>. Generally speaking, in the deactivated condition, rotor <NUM> is only slowly rotating within stator <NUM>, and as a result, flow pulsing system <NUM> may only produce a small amount of pulsating flow.

During drilling operations, drilling mud may be introduced within the bore or annulus of a drill string (not shown) and impart upstream flow <NUM> which extends from first sub <NUM> into activation section <NUM>. Upstream flow <NUM> flows generally along axis <NUM> and thus tends to continue this flow direction through screen <NUM> and pass largely as bore flow <NUM> into bore <NUM> within rotor <NUM>. Due to limited flow restrictions downstream of bore flow <NUM>, relatively small back pressures occur that impede bore flow <NUM>, and in general, this deactivated condition may results in only <NUM> to <NUM> psi in pressure losses passing thorough flow pulsing system <NUM> overall. Under some flow conditions, backpressure within bore <NUM> of rotor <NUM> may occur which will bias some annulus flow <NUM> through screen elements <NUM> of screen <NUM>. Annulus flow <NUM> then progresses downstream moving between rotor <NUM> and stator <NUM>, thereby causing some rotation of rotor <NUM>, even in the deactivated condition. The gap between screen <NUM> and rotor <NUM> is shown exaggerated for clarity, and may in application approach abutting contact, such that any annulus flow <NUM> will pass through screen elements <NUM>. This configuration may be helpful in preventing particulate clogging between rotor <NUM> and stator <NUM>. For example, loss circulation materials within upstream flow <NUM>, will tend to be directed into bore <NUM>, and away from the relatively smaller passages between rotor <NUM> and stator <NUM>. Additionally, the tapered shape of screen housing <NUM> may tend to prevent clogging of screen elements <NUM>, and may in effect be "self-cleaning". Also, the close positioning of screen <NUM> may offer an additional operational benefit for rotor section <NUM>, as rotor <NUM> may be constrained from axial motion as second end <NUM> of screen <NUM> abuts first end <NUM> of rotor <NUM>. During some flow conditions, rotor <NUM> may tend to "kick back" and thus apply thrust forces against screen <NUM>, even when screen <NUM> is configured to maintain a clearance gap between ends <NUM>, <NUM>.

Referring to <FIG>, activation section <NUM> is shown in an activated condition or position, wherein dart <NUM> is installed within rotor <NUM>. In the activated condition, additional upstream flow <NUM> is directed to annulus flow <NUM> to impart increased rotation of rotor <NUM>, which causes flow pulsing system <NUM> to produce an increased pulsing flow. The pulsing frequency and magnitude are related to the flow rate of annulus flow <NUM>, which is controllable in part by selecting a particular nozzle <NUM> for dart <NUM>. More particularly, when dart <NUM> is mated along seat <NUM> of rotor <NUM>, ring <NUM> may seal along second bore <NUM> of rotor <NUM>, and substantially all bore flow <NUM> through rotor <NUM>, will pass through nozzle <NUM>, and the back pressure (e.g., head loss or pressure drop through nozzle <NUM>) will then drive larger annulus flow <NUM>, which spins rotor <NUM> at a higher frequency. By providing a variety of nozzle <NUM> configurations, users of flow pulsing system <NUM> are able to select a flow pulsing frequency and magnitude which are appropriate for the specific downhole conditions once the drill string is already in position within a partially drilled wellbore. Because the overall pressure losses through flow pulsing system <NUM> tend to increase with increased annulus flow <NUM>, users of flow pulsing system <NUM> may select a nozzle <NUM> with an inner nozzle profile <NUM> (as shown in <FIG>) that optimizes the flow pulsing frequency and amplitude while balancing the overall pressure drop across flow pulsing system <NUM>. Additionally, the diameter of orifice <NUM> (<FIG>) and the drilling mud composition (e.g. weight and viscosity) may also be varied to influence the pulsing frequency and amplitude. This ability to balance the flow pulsing system <NUM> performance against the associated pressure drop may be advantageous during operations, as the exact flow pulsing frequency and amplitude needed may not be known or predicable ahead of drilling operations. Additionally, even if the user did prospectively know what frequency and amplitude was going to be needed, the on/off selectability may allow the users to only engage flow pulsing system <NUM> once it is needed, and thus preserving the pumping pressure requirements from the surface equipment on the drilling rig.

Additionally, activation section <NUM> may be returned to the deactivated condition, as shown in <FIG>, as dart <NUM> may be selectably disengaged from seat <NUM> of rotor <NUM>. More particularly, a separate tool (e.g., a wireline tool or puller, not shown) may be used to grip dart <NUM> along shoulder <NUM> and/or neck <NUM> and apply tensile forces to retrieve dart <NUM>. In some embodiments, a close proximity between first end <NUM> of rotor <NUM> and second end <NUM> of screen <NUM> may be advantageous, as abutting contact therebetween may compressively resist the tensile forces applied to dart <NUM>. After retrieval of dart <NUM>, drilling operations may continue without operating flow pulsing system <NUM>, thus reducing the overall pressure drop across flow pulsing system <NUM>, or nozzle <NUM> of dart <NUM> may be reconfigured to select a different flow pulsing frequency or magnitude than what was initially used. This sequential retrieval and reconfiguring of dart <NUM> may be repeated as necessary during the drilling operations.

Referring to <FIG>, valve section <NUM> is shown in a deactivated condition, wherein dart <NUM> is not installed within rotor <NUM>. As previously described, in the deactivated condition, bore flow <NUM> is greater than annulus flow <NUM>, thus most of the total upstream flow <NUM> is directed between central ports <NUM>, <NUM>, which may be configured to produce only small pulsing flows. More particularly, central port flow <NUM> is defined between central ports <NUM>, <NUM> of oscillating valve port section <NUM> and stationary valve port section <NUM>, respectively. Valve port flow <NUM> is defined between oscillating valve ports <NUM> and stationary valve ports <NUM>. Downstream flow <NUM> is defined as the flow exiting stationary valve adapter <NUM> and entering into second sub <NUM> and comprises the summation of flows <NUM>, <NUM>. Flow <NUM> is also shown passing through orifice <NUM>, which in some flow configurations, may provide a flow path between bore flow <NUM> and annulus flow <NUM>. For example, as will be discussed more fully below, when nozzle <NUM> is directing flow to annulus flow <NUM> while a blockage exists between ports <NUM>, <NUM> that restricts or fully blocks valve port flow <NUM>.

Referring to <FIG>, an axial view aligned with axis <NUM> is shown to illustrate the relative positions of oscillating valve port section <NUM> and stationary valve port section <NUM>. More specifically, each figure shows the port positions along the abutting faces of sections <NUM>, <NUM> to illustrate the valve overlaps as oscillating valve port section <NUM> nutates with rotor <NUM> relative to the stationary position of stationary valve port section <NUM>. Also, point P shows where sections <NUM>, <NUM> contact, or most closely approach contact in each oscillating valve port section <NUM> position. Central port overlap <NUM> is defined as the open passage between central ports <NUM>, <NUM>, while first port overlap <NUM>, second port overlap <NUM>, third port overlap <NUM>, and fourth port overlap <NUM> are defined between the plurality of oscillating valve ports <NUM> and stationary valve ports <NUM>. As shown in <FIG>, the areas between port overlaps <NUM>, <NUM>, <NUM>, <NUM> may not be equal in some arrangements of ports <NUM>, <NUM>, and the relative magnitude of areas of port overlaps <NUM>, <NUM>, <NUM>, <NUM> may vary as a function of oscillating valve port section <NUM> position, as shown for example in <FIG>. Overall, the summation of areas of port overlaps <NUM>, <NUM>, <NUM>, <NUM> influences valve port flow <NUM> (as shown in <FIG>), while the area of central port overlap <NUM> influences central port flow <NUM> (as shown in <FIG>). Together, the change of port overlaps <NUM>, <NUM>, <NUM>, <NUM> and central port overlap <NUM>, with respect to rotor <NUM> position (e.g., with respect to time) creates periodic flow pressure pulses in downstream flow <NUM>. <FIG> shows a position having a maximum total area for port overlaps <NUM>, <NUM>, <NUM>, <NUM>, which may alternatively be referred to a "fully open position" of valve section <NUM>. <FIG> shows a "partially open position" of valve section <NUM>, wherein the total area for port overlaps <NUM>, <NUM>, <NUM>, <NUM> is less than the maximum total area of the fully open position. <FIG> shows a "fully closed position" of valve section <NUM>, wherein no port overlaps <NUM>, <NUM>, <NUM>, <NUM> are present.

Referring to <FIG>, in the deactivated condition, wherein dart <NUM> is not installed within rotor <NUM>, bore flow <NUM> is greater than annulus flow <NUM> and thus central port flow <NUM> through central port overlap <NUM> is greater than valve port flow <NUM> through port overlaps <NUM>, <NUM>, <NUM>, <NUM>. Despite comparable flow areas for central port flow <NUM> and valve port flow <NUM> through valve section <NUM> in some embodiments, central port flow <NUM> will still be larger than valve port flow <NUM> in the deactivated condition as annulus flow <NUM> has a higher pressure drop along rotor section <NUM> than does bore flow <NUM>. A small annulus flow <NUM> results in only slight rotor <NUM> rotation, only slight variations in central port overlap <NUM>, and thus only slight pressure pulses in downstream flow <NUM>. Additionally, in some embodiments, even with rotor <NUM> rotation, central port overlap may be configured to have little or no area change with respect to rotor position. Flow <NUM> may also pass out of bore <NUM> and contribute to valve port flow <NUM>, however, this flow will still not produce flow pulses, as this "bypass" flow will not rotate rotor <NUM>, and thus will not vary port overlaps <NUM>, <NUM>, <NUM>, <NUM>.

Referring still to <FIG>, after activation section <NUM> is in the activated condition, with dart <NUM> installed within rotor <NUM>, annulus flow <NUM> is increased relative to the deactivated condition. Annulus flow <NUM> leads to valve port flow <NUM> and intermittently diverts to flow <NUM> as port overlaps <NUM>, <NUM>, <NUM>, <NUM> reduce in area. The diameter of orifice <NUM> may be adjusted to provide the appropriate "bypass" flow and in some embodiments, orifice <NUM> may be fully omitted. As previously described, the magnitude of bore flow <NUM> depends on nozzle <NUM> selection and in some configurations may still be large as compared to annulus flow <NUM>, thus central port flow <NUM> will also be comparatively large. In this configuration, central port overlap <NUM> may or may not contribute to the pressure pulses, depending on the relative sizes and positions of central ports <NUM>, <NUM>.

In the manner described, embodiments disclosed herein include systems and methods for using a flow pulsing system which may be selectively engaged after wellbore drilling has begun, and while the drilling string remains disposed within the wellbore. Additionally, systems and methods disclosed herein allow selective adjustability of the flow pulsing system frequency and magnitude, as well as systems and methods to selectively disengage and/ or reconfigure the frequency and magnitude, while the flow pulsating system remains disposed within the wellbore. In this manner, the overall pressure loss through flow pulsing system <NUM> may be selectively controlled. Further, systems and methods disclosed herein provide valve ports which may be operated between a fully open, a partially open, and a fully closed position which may provide an improved pressure pulse response. As the valve port sections <NUM>, <NUM> cycle through the open, partially open, and closed positions the oscillating valve portion section <NUM> nutates relative to the stationary valve port section <NUM>. Still further, systems and methods disclosed herein resist clogging of the flow pulsing system when materials are introduced into the wellbore, such as loss circulation materials or diverter.

Claim 1:
A flow pulsing system (<NUM>) comprising:
a housing having a central axis (<NUM>), a first end (<NUM>), a second end (<NUM>) opposite the first end, and a bore (<NUM>) extending along the central axis from the first end to the second end;
a stator (<NUM>) disposed within the bore of the housing having a plurality of lobe cavities (<NUM>);
a rotor (<NUM>) disposed within the stator, the rotor comprising:
an axis (<NUM>) offset from the central axis;
a plurality of lobes (<NUM>) that mate with the plurality of lobe cavities; and
a thru bore (<NUM>) extending along the axis; and
a valve section (<NUM>), characterized in that it comprises:
a stationary valve (<NUM>) coupled to the second end of the housing, the stationary valve comprising a first face (<NUM>), a stationary central port (<NUM>), and a plurality of stationary valve ports (<NUM>);
an oscillating valve (<NUM>) coupled to the rotor, the oscillating valve comprising a second face (<NUM>) abutting the first face, an oscillating central port (<NUM>) in fluid communication with the thru bore of the rotor, and a plurality of oscillating valve ports (<NUM>) in fluid communication with the plurality of lobe cavities.