GENERATION OF FLUID PULSES IN UNDERGROUND WELLS

Abstract

A fluid pulse generator may include a fluid motor comprising a rotor that rotates in response to fluid flow, a variable flow restrictor positioned upstream of the fluid motor comprising a restrictor member that can rotate relative to a member with openings and is longitudinally displaceable relative to the rotor. Another fluid pulse generator may include a flexible joint or a constant velocity joint connected between the restrictor member and the rotor.In another fluid pulse generator, the variable flow restrictor may include a valve and a fluidic restrictor element. The valve is operated in response to the rotation of the rotor, the fluidic restrictor element is configured to generate fluid pulses in response to fluid flow through one flow path, and the valve is configured to control fluid flow through another flow path connected in parallel with the first flow path.

Description

GENERATION OF FLUID PULSES IN UNDERGROUND WELLS FIELD OF INVENTION This disclosure relates in general to equipment used and operations performed in conjunction with an underground well and, in an example described below, provides more particularly the generation of fluid pulses in wells. BACKGROUND OF THE INVENTION It can be advantageous in some situations to be able to periodically or intermittently restrict or block the flow of fluid through a tubing string in a well. Such fluid flow restrictions can result in corresponding fluid pulses being produced in the coupled tubing string. In some examples, these fluid pulses can help advance the coupled tubing string through the well, for example, by causing vibration of the coupled tubing string, producing a water hammer effect, and / or reducing friction between the coupled tubing string and the wellbore wall. Therefore, it will be appreciated that continuous improvements in the technique of generating fluid pulses in underground wells are necessary. Such improvements can be useful in a variety of different well operations (e.g., drilling, completion, stimulation, injection, production, etc.) and for a variety of different purposes. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially representative cross-sectional view of an example of a well system and the associated method that can materialize the principles of this disclosure. FIG. 2 is a representative cross-sectional view of an example of a fluid pulse generator and fluid motor that can be used with the system and method of FIG. 1. FIG. 3 is a representative cross-sectional view of an example of a section of a flexible joint section and a fluid motor bearing section. FIG. 4 is a representative cross-sectional view of an example of the fluid pulse generator. FIG. 5 is a representative perspective and partially cross-sectional view of the fluid pulse generator. FIG. 6 is a representative perspective and partially cross-sectional view of the fluid pulse generator. FIG. 7 is a representative perspective view of an example of a fluid pulse generator member with openings. uooo FIG. 8 is a representative top view of an example of a restraining member and the member with openings in a partially restrained configuration. FIG. 9 is a representative top view of the restraining member and the member with openings in a substantially restrained configuration. FIG. 10 is a representative top view of a restraining member and the member with openings in a substantially restrained configuration. FIG. 11 comprises representative top views of the restricting member and the member with openings in a succession of configurations that make a complete cycle. FIG. 12 is a representative cross-sectional view of another example of the fluid pulse generator and an upper portion of the fluid motor. FIG. 13 is a representative cross-sectional view of the fluid pulse generator of FIG. 12. FIG. 14 is a cross-sectional and perspective view representative of the fluid pulse generator of FIG. 12. FIG. 15 is a partially cross-sectional and perspective view representative of the fluid pulse generator of FIG. 12. FIG. 16 is a representative perspective view of a restrictor member, a member with openings, a bearing assembly, and a flexible joint of the fluid pulse generator of FIG. 12. FIG. 17 is a representative perspective view of the restrictor member, the member with openings, the bearing assembly, and the flexible joint of the fluid pulse generator of FIG. 12. FIG. 18 is a representative perspective and partially cross-sectional view of another example of the fluid pulse generator and an upper portion of the fluid motor. FIG. 19 is a representative cross-sectional view of the fluid pulse generator of FIG. 18 and the upper portion of the fluid motor. FIG. 20 is a representative cross-sectional view of another example of the fluid pulse generator and an upper portion of the fluid motor. FIGS. 21 and 22 are representative cross-sectional views of the fluid pulse generator of FIG. 20 in substantially unconstrained and substantially constrained configurations, respectively. FIGS. 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 are representative side and perspective views of a restrictor member of the fluid pulse generator of FIG. 20. FIG. 33 is a representative schematic view of another example of the system and method. FIGS. 34 and 35 are perspective and partially cross-sectional views representative of another example of the fluid pulse generator and an upper portion of the fluid motor. FIG. 36 is a representative cross-sectional view of a rotary valve assembly, an inner mandrel, and a constant velocity joint used with the fluid pulse generator of FIGS. 34 and 35. FIG. 37 is a representative perspective view of the rotary valve assembly, inner mandrel, and constant velocity joint used with the fluid pulse generator of FIGS. 34 and 35. FIG. 38 is a representative exploded perspective view of the rotary valve assembly and the inner mandrel used with the fluid pulse generator of FIGS. 34 and 35. FIGS. 39, 40 and 41 are representative top, bottom and top perspective views respectively of a fluid pulse generator bearing assembly of FIGS. 34 and 35. FIGS. 42 and 43 are representative top views of the rotary valve assembly of the fluid pulse generator of FIGS. 34 and 35 in substantially restricted and substantially unrestricted respective configurations. FIGS. 44 and 45 are representative perspective views of an example of a fluidic restrictor element that can be used with the fluid pulse generator of FIGS. 34 and 35. FIG. 46 is a representative side view of the fluidic restrictor element. FIG. 47 is a representative cross-sectional view of the fluidic restrictor element. FIGS. 48 and 49 are representative perspective and cross-sectional views of the fluidic restrictor element. FIGS. 50, 51 and 52 are representative side and cross views of another example of the fluidic restrictor element. FIGS. 53, 54 and 55 are representative perspective and cross-sectional, lateral and cross-sectional views, respectively, of another example of the fluidic restrictor element. FIGS. 56 and 57 are representative side and cross views of another example of the fluidic restrictor element. FIG. 58 is a representative cross-sectional view of another example of the rotary valve assembly. FIG. 59 is a representative side perspective view of an example of the bearing assembly of the rotary valve assembly of FIG. 58. uooo FIG. 60 is a representative cross-sectional view of another example of the fluid pulse generator and an upper portion of the fluid motor. FIGS. 61A and 61B are representative perspective views of the fluid pulse generator restrictor member of FIG. 60 in substantially restricted and substantially unrestricted configurations respectively. FIG. 62 is a representative schematic view of another example of the fluid pulse generator. FIG. 63 is a representative cross-sectional view of the fluid pulse generator of FIG. 62. DETAILED DESCRIPTION OF THE INVENTION It is illustrated representatively in the FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61A, 61B, 62, 63 a generator of Fluid pulse generator 10, system 12, and the associated method can materialize the principles of this disclosure. However, it should be clearly understood that pulse generator 10, system 12, and the method are merely one example of the practical application of the principles of this disclosure, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited to all the details of the specific pulse generator 10, system 12, and method of the examples described herein and / or depicted in the drawings. In one example, the fluid pulse generator 10 may include a fluid motor and a variable flow restrictor. The fluid motor includes a rotor configured to rotate in response to the fluid flow through the motor. The variable flow restrictor is positioned upstream of the fluid motor and includes a restrictor member that the rotor can rotate relative to a member with openings, thereby variably restricting the fluid flow. The restrictor member can be displaced longitudinally relative to the rotor. In another example of a fluid pulse generator 10, the system 12 and method described below, as a fluid motor rotates a rotary valve element, the resistance to fluid flow increases when a bypass flow path is blocked, and the resistance to fluid flow decreases when the bypass flow path is unblocked. In some examples, the same fluid motor can be used to rotate a drill bit and drive the fluid pulse generator. The fluid motor can rotate a rotary valve element uphill. In some examples, a flexible joint or constant velocity joint can be connected between a fluid motor rotor and a rotary valve element or restrictor member. The fluid flow through the fluid pulse generator can be substantially restricted only during a minority of a rotational cycle of a rotary valve element or restrictor member. A rotary valve element or restrictor member can be connected to a fluid motor rotor, and the rotary valve element or restrictor member can rotate relative to a fluid pulse generator member with openings. In another example described below, a fluid pulse generator 10, a system 12, and a method may include a fluid restrictor element connected in parallel with a rotary valve assembly. The fluid restrictor element and the rotary valve assembly may be upstream of a fluid motor. A rotary valve element of the rotary valve assembly may be rotated by a fluid motor. The fluidic restrictor element may include a vortex chamber. A restriction to fluid flow through the vortex chamber may alternately increase and decrease in response to the fluid flow through the chamber. The formation of a vortex in the vortex chamber can be prevented by unblocking the flow through a bypass flow path. With reference to FIG. 1, an example of system 12 used with an underground well is illustrated. In this example, the pulse generator 10 is connected to a drill string 14 used to drill a well 16 in an earth formation 18. For this purpose, the drill string 14 has a drill bit 20 connected at its distal end. Although well 16 is depicted in FIG. 1 as vertical, in other examples, the principles of this disclosure could be applied to generally horizontal or inclined sections of the well. Although pulse generator 10 is depicted connected to drill string 14, in other examples the pulse generator could be connected to other types of coupled pipe strings (such as an injection string, a production string, a completion string, etc.). Although fluid motor 22 is depicted in FIG. 1 as being connected between and adjacent to pulse generator 10 and drill bit 20, in other examples there could be other well tools (such as logging tools, telemetry tools, stabilizers, centralizers, etc.) connected between these components.Thus, the scope of this disclosure is not limited to any particular detail of system 12 as depicted in FIG. 1. In example FIG. 1, drill bit 20 is rotated to advance well 16 into formation 18. For this purpose, drill string 14 includes fluid motor 22 connected between pulse generator 10 and drill bit 20. The fluid motor 22 in this example is a Moineau-type fluid motor, also known as a drilling motor or mud motor. In other examples, other types of fluid motors (such as a turbine) may be used. The fluid motor 22 rotates the drill bit 20 in response to the flow of a fluid 24 through the drill string 14. The fluid 24 exits the drill string 14 through nozzles (not shown) in the drill bit 20 and then returns to the surface through an annulus 26 formed between the well 16 and the drill string. In addition to rotating the drill bit 20, in this example the fluid motor 22 also rotates a restricting member of the pulse generator 10, so that the flow of fluid 24 through the pulse generator is periodically obstructed or restricted. When the flow of fluid 24 through the pulse generator 10 is substantially restricted, a portion of the momentum of the fluid 24 above the pulse generator is converted into elastic deformation of the drill string 14 above the pulse generator, resulting in elongation of that section of the drill string. When the flow of fluid 24 through the pulse generator 10 is not substantially restricted, the section of the drill string 14 above the pulse generator contracts longitudinally.This alternating lengthening and contraction of the drill string 14 can be used to facilitate the advancement of the drill string through well 16, and may be particularly useful for advancing the drill string through highly deviated wells, although the scope of this disclosure is not limited to any particular purpose or function for which the pulse generator 10 is used. In example FIG. 1, it is desired that the drill bit 20 rotate continuously as well 16 advances through formation 18, and fluid flow 24 through fluid motor 22 is required to produce the fluid motor's rotation. Therefore, pulse generator 10 is designed to continuously allow at least some fluid flow through it, even when the fluid flow is substantially obstructed or restricted. Furthermore, the rate of penetration is improved by allowing substantially unrestricted or unobstructed fluid flow 24 through pulse generator 10 most of the time. With additional reference now to FIGS. 2, 3, 4, 5, 6, 7, 8, 9, 10, representative examples of the pulse generator 10 and the fluid motor 22 are illustrated. The pulse generator 10 and the fluid motor 22 can be used in system 12 and the method of FIG. 1, or they can be used with other systems and methods. In FIG. 2, the pulse generator 10 is shown connected to an upper end of the fluid motor 22. In this example, the fluid motor 22 is provided with a flexible joint section 28 and a bearing section 30. An example of the flexible joint and the bearing sections 28, 30 is illustrated representatively in FIG. 3. The flexible joint section 28 includes an elongated flexible rod or flexible joint 32 positioned in a generally tubular outer housing 34. An upper end of the flexible joint 32 is connected to a lower end of a rotor 36 of the fluid motor 22. The rotor 36 is positioned in an outer housing of the stator 38 of the fluid motor 22. The bearing section 30 includes a generally tubular outer housing 40, bearings 42, and an inner mandrel 44 having a connector 46 at its lower end. The bearings 42 support the inner mandrel 44 for rotation in the outer housing 40. An upper end of the inner mandrel 44 is connected to a lower end of the flexible joint 32. The connector 46 extends outward from the outer housing 40 and, in this example, is configured to connect to the drill bit 20 (see FIG. 1). The flow of fluid 24 through the fluid motor 22 passes between an outer helical profile of the rotor 36 and an inner helical profile of the stator housing 38. This flow causes the rotation of the rotor 36, as well as the flexible joint 32 and the inner mandrel 44 connected to it. As the rotor 36 turns, it also rotates around a central longitudinal axis 48 of the fluid motor 22. The upper end of the flexible joint 32 rotates and turns with the rotor 36 (a type of motion known as hypocyclic or epicyclic), but the lower end of the flexible joint is restricted by its connection to the inner mandrel 44, so that the lower end only rotates around axis 48. Thus, the flexibility of the flexible joint 32 allows its upper end to rotate and turn around axis 48, while its lower end is restricted to rotating only around axis 48. Figures 4, 5, and 6 illustrate representative views of the pulse generator 10 connected to an upper end of the fluid motor 22. In these views, it can be seen that the pulse generator 10 includes an internal mandrel 50 rigidly connected to an upper end of the rotor 36. In this way, the internal mandrel 50 rotates and turns with the rotor 36 around the central axis 48. In some examples, the internal mandrel could be formed entirely from the rotor 36. An upper end of the inner mandrel 50 is internally splined. A shaft 52 of a restrictor member 54 is externally splined and slides into the upper end of the inner mandrel 50. The longitudinally splined, variable-length connection 98 between the inner mandrel 50 and the shaft of the restrictor member 52 allows rotation and torque to be transmitted from the rotor 36 to the restrictor member 54, while also providing a variable longitudinal distance between the rotor and the restrictor member. IVIA / a / ZUZZ / UI UOOO Other types of variable-length connections can be used to transmit rotation and torque from the rotor 36 to the restraining member 54. For example, a key carried on the shaft 52 or the inner mandrel 50 could be slidably engaged in a longitudinally extending groove formed in the other of these. Thus, the scope of this disclosure is not limited to the use of any particular type of variable-length connection. The restrictor member 54 is a component of a variable flow restrictor 56 of the pulse generator 10. The variable flow restrictor 56 variably restricts or obstructs the flow of fluid 24 through the pulse generator 10. The variable flow restrictor 56 in this example includes the restrictor member 54 and a member with openings 58. The variable-length connection 98 between the inner mandrel 50 and the shaft of the restrictor member 52 allows the flow of fluid 24 to be diverted by the restrictor member 54 against an upper face of the perforated member 58. This surface contact between the restrictor member 54 and the perforated member 58 facilitates the generation of desired variations in the flow of fluid 24 by restricting fluid leakage between the contact surfaces of the restrictor member and the perforated member. The pulse generator 10 includes an outer housing assembly 60 containing the variable flow restrictor 56 and an upper portion of the inner mandrel 50. The outer housing assembly 60 is connected to the stator housing 38 of the fluid motor 22. Rotation of the restrictor member 54 relative to the perforated member 58 by the rotor 36 causes the restriction of fluid flow 24 through the pulse generator 10 to vary repeatedly between substantially unrestricted and substantially restricted configurations. In other instances, the perforated member 58 could be rotated relative to the restrictor member 54 to vary the restriction to fluid flow. Therefore, the scope of this disclosure is not limited to the rotation of any specific variable flow restrictor member 56 by the rotor 36. Figures 7, 8, 9, and 10 illustrate representative examples of the restrictor member 54 and the perforated member 58, separated from the rest of the pulse generator 10. In these views, it can be observed that this example of the restrictor and the perforated members 54 and 58 are uniquely configured to provide substantially unrestricted flow of fluid 24 through the pulse generator 10 for most of a rotational cycle, and to provide substantially restricted flow only for a small minority of the rotational cycle. In FIG. 7, it can be seen that the member with openings 58 has an outer rim 62 formed on it. The rim 62 engages an inner rim in the outer housing assembly 60, thus preventing the member with openings 58 from moving longitudinally beyond the inner rim. In some examples, the member with openings 58 could be press-fitted or otherwise secured in the outer housing assembly 60 to prevent relative rotation between the member with openings and the outer housing assembly. An upper face 58a of the member with openings 58 has a semicircular notch or cavity 58b formed therein. In some examples, the cavity 58b may extend more than 180 degrees around a central inner diameter 58c formed through the member with openings 58. Multiple openings 58d extend between the cavity 58b and a lower face 58e (see FIG. 6) of the member with openings 58. The openings 58d allow fluid communication between the cavity 58b in the pulse generator 10 and the fluid motor 22 below (downstream of) the variable flow restrictor 56. In FIG. 8, it can be observed that the restrictor member 54 only partially overlaps the upper face 58a of the member with openings 58. When none of the cavities 58b are blocked by the restrictor member 54, the cavity allows fluid 24 to flow through all the openings 58d. Thus, the restriction to the flow of fluid 24 through the variable flow restrictor 56 depends on how much of the cavity 58b is blocked by the restrictor member 54. Figure 8 also illustrates an example of how the restrictor member 54 rotates and turns relative to the opening member 58. The restrictor member 54 rotates clockwise about its longitudinal axis 66 when viewed from above, as indicated by arrow 64. The rotor 36 and inner mandrel 50 also rotate in this direction. The restrictor member 54 rotates counterclockwise about the central axis 48 when viewed from above, as indicated by arrow 68. The rotor 36 and inner mandrel 50 also rotate about axis 48 in this direction. In other examples, the restrictor member 54 could rotate counterclockwise about its longitudinal axis 66, and the restrictor member could rotate clockwise about the central axis 48. An upper section of the restraining member 54 is generally cylindrical in shape, but has a circumferentially extending cavity 70 formed in a section of its outer circumference. In this example, the cavity 70 extends less than 180 degrees around the outer circumference of the restraining member 54. In Figures 9 and 10, the variable flow restrictor 56 is shown in its maximum and minimum restricted or obstructed configurations, respectively. In Figure 9, the restrictor member 54 is in a position where it obstructs most of the flow area through the upper face 58a of the member with openings 58. In this position, the flow of fluid 24 through the variable flow restrictor 56 is at a minimum. In FIG. 10, it can be observed that the restrictor member 54 is in a position where most of the flow area across the upper face 58a of the member with openings 58 is not obstructed by the restrictor member. In this position, the flow of fluid 24 through the variable flow restrictor 56 is at its maximum. With further reference to FIG. 11, a sequence of positions of the restrictor member 54 with respect to the opening member 58 is representatively illustrated for a complete 360-degree rotation of the restrictor member. It should be noted that the restrictor member 54 in this example moves from the maximum restricted configuration to the minimum restricted configuration, and then back to the maximum restricted configuration, during a complete cycle comprising 360 degrees of rotation. It should be noted that in this example it is desirable that the lower face 54a of the restrictor member 54 (see FIG. 4) be in contact with the upper face 58a of the member with openings 58 for the effective variation of the restriction to flow through the variable flow restrictor 56. Preferably, the restrictor member 54 and the member with openings 58 are made of durable materials resistant to erosion and wear, or at least the lower face 54a and the upper face 58a comprise such materials. It should also be noted that the flow of fluid 24 through the variable flow restrictor 10 tends to deflect the restrictor member 54 against the member with openings 58, thereby increasing the bearing stress between the lower face 54a and the upper face 58a. The splined connection 98 between the shaft 52 and the inner mandrel 50 allows the restrictor member 54 to move in the direction of the flow. In example Figures 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11, the restraining member 54 includes a lower portion 54b made of a carbide material. An upper portion of the member with openings 58 could be similarly made of a carbide material. Alternatively, the lower and upper faces 54a and 58a could have a hard coating applied using any of a variety of different processes. Any technique may be used to prevent or reduce wear between faces 54a and 58a while adhering to the principles of this disclosure. Alternatively, one of the faces 54a, 58a could be made of a material designed to wear gradually as the variable flow restrictor 56 operates downhole. In this alternative, face 54a or 58a could be replaced after it is sufficiently worn (perhaps after each use). With additional reference now to FIGS. 12, 13, 14, 15, 16, 17, another example of the impulse generator 10 is illustrated in a representative manner. In this example, the restricting member 54 rotates about the central axis 48, but does not rotate about the central axis (e.g., in a hypocyclic or epicyclic motion) as in example FIGS. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. In example FIGS. 12, 13, 14, 15, 16, and 17, a flexible joint 72 is used instead of the inner mandrel 50. The flexible joint 72 is connected at its upper end to the restrictor member 54 using a longitudinally splined or variable-distance connection 98, and at its lower end to the upper end of the rotor 36. The flexible joint 72 in this example may be made of a titanium material with pressed steel end portions. However, the scope of this disclosure is not limited to the use of any particular material for any particular component of any of the variable-flow restrictor examples described herein. The lower end of the flexible joint 72 rotates and turns with the rotor 36 around the central shaft 48. However, the flexibility of the flexible joint 72 allows the upper end of the flexible joint to be constrained by a bearing assembly 74, so that it only rotates around the central shaft 48. It should be noted that the openings 74a are formed through the bearing assembly 74 to allow fluid 24 to flow through the bearing assembly. In Figures 16 and 17, it can be seen that the restrictor member 54 has a cavity 54c formed in its lower face 54a, and multiple openings 54d extending through the restrictor member. In this example, the cavity 54c extends more than 180 degrees around the shaft 52, while the cavity 58b in the upper face 58a extends less than 180 degrees around the center diameter 58c. The restriction to the flow of fluid 24 through the variable flow restrictor 56 is determined by the degree to which the cavities 54c and 58b overlap as the restrictor member 54 rotates with respect to the member with openings 58. With reference now to FIGS. 18 and 19, another example of the pulse generator 10 is illustrated representatively. In this example, a universal joint or constant velocity joint assembly 76 is connected between the rotor 36 and the restricting member 54 instead of the flexible joint 72 of example FIGS. 12, 13, 14, 15, 16, 17. The lower end of the joint assembly 76 rotates and turns with the rotor 36 around the central shaft 48. However, the joint assembly 76 allows the upper end of the joint assembly to be restricted by the bearing assembly 74, so that it only rotates around the central shaft 48. The operation of example FIGS. 18 and 19 is substantially similar to the operation of example FIGS. 12, 13, 14, 15, 16, 17. ινΐΛ / a / zuzz / u ι uooo With reference now to FIGS. 20, 13, 14, 15, 16, 32, another example of the pulse generator 10 is illustrated in a representative manner. In this example, the variable flow restrictor 56 is configured so that the restrictor member 54 rotates within the member with openings 58. The restricting member 54 is press-fitted or otherwise secured to an upper end of the flexible joint 72, which is connected between the restricting member and the rotor 36. In other examples, the constant velocity joint 76 may be used instead of or in addition to the flexible joint 72. As depicted in FIGS. 20-22, the restrictor member 54 is received into the perforated member 58. An upper end of the perforated member 58 is closed, except that a passage and / or opening 58d extends through a side wall of the perforated member. The opening 58d allows fluid 24 to flow into the perforated member 58. The restrictor member 54 periodically obstructs the opening 58d, thereby restricting the flow of fluid 24 through the variable flow restrictor 56. As shown in FIG. 21, the restrictor member 54 is rotated to a position where the opening 58d is not obstructed by the restrictor member, thus allowing maximum flow of fluid 24 through the variable flow restrictor 56. In FIG. 22, the restrictor member 54 is rotated to a position where the opening 58d is most obstructed by the restrictor member, thus allowing minimum flow of fluid 24 through the variable flow restrictor 56. Figures 23-32 depict various views of the restrictor member 54. In these views, it can be observed that the restrictor member 54 is configured to allow relatively unobstructed flow of fluid 24 through the variable flow restrictor 56 during most of the rotation of the restrictor member. The flow of fluid 24 is substantially restricted by the variable flow restrictor 56 only during a small portion of the rotation of the restrictor member 54 with respect to the member with openings 58. A relatively small cavity or channel 100 formed in an upper portion of the restrictor member 54 allows a small amount of fluid to flow through the fluid pulse generator 10, even when the restrictor member obstructs the opening 58d. It should be noted that the splined connection 98 is not used in the example FIGS. 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32. However, the restricting member 54 can be displaced somewhat longitudinally with respect to the member with openings 58, for example, to accommodate the longitudinal displacement of the rotor 36 with respect to the stator housing 38. Another example of the fluid pulse generator 10 is illustrated representatively in FIGS. 60, 61A, 61B. In this example, the restrictor member 54 is rotated externally (e.g., circumferentially around) the member with openings 58. The restrictor member 54 includes an extension 54e that obstructs or blocks flow through the opening 58d in the member with openings 58, but only in a minority of a rotation cycle of the restrictor member. The extension of the restrictor member 54e periodically obstructs the opening 58d, thereby restricting the flow of fluid 24 through the variable flow restrictor 56. As shown in FIG. 61A, the restrictor member 54 is rotated to a position where the opening 58d is obstructed by the extension of the restrictor member 54e, thus allowing minimum flow of fluid 24 through the variable flow restrictor 56. In FIG. 61B, the restrictor member 54 is rotated to a position where the opening 58d is not obstructed by the extension of the restrictor member 54e, thus allowing maximum flow of fluid 24 through the variable flow restrictor 56. With additional reference now to FIGS. 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, another example of the fluid pulse generator 10 and system 12 is representatively illustrated. In this example, the fluid motor 22 drives a valve 80 that alternately prevents and permits flow through a bypass flow path 82. The bypass flow path 82 is parallel with a flow path 84 through a fluid restrictor element 86. The fluidic restrictor element 86 may comprise any fluidic device capable of restricting fluid flow in response to fluid flow through the fluidic device. Examples of suitable fluidic devices are described in U.S. Patent Nos. 8381817, 8439117, 8453745, 8517105, 8517106, 8517107, 8517108, 9212522, 9316065, 9915107, 10415324, and 10513900. The full disclosures of these U.S. patents are incorporated herein by reference. As depicted in FIG. 33, fluid 24 can flow to valve 80 and fluid restrictor 86. When valve 80 is open, fluid 24 will preferentially flow through the bypass flow path 82, since it presents less resistance to the flow of fluid 24. When valve 80 is closed, fluid 24 is forced to flow through fluid restrictor 86, thereby variably restricting the flow of fluid 24 through the fluid restrictor 86. It should be noted that the flow of fluid 24 is continuously allowed through the fluid restrictor element 86 and, therefore, even when valve 80 is closed, fluid 24 still flows through fluid motor 22. In this way, fluid motor 22 can continue to drive valve 80, whether the valve is open or closed. In FIGS. 34 and 35, it can be observed that the valve 80 is driven in a manner similar to example FIGS. 18 and 19, with the constant velocity joint assembly 76 used to transmit rotation from the rotor 36 to an internally splined mandrel 50 rotatably supported in the bearing assembly 74. The flexible joint 72 may be used instead of the constant velocity joint assembly 76 in other examples. An externally splined shaft 52 is received in the inner mandrel 50 and connected to a rotary valve element 88. The splined inner mandrel 50 and shaft 52 are the same as or similar to the variable length connection 98 described above. Figures 36 and 37 illustrate a representative valve assembly 90 of the fluid pulse generator 10. The rotary valve assembly 90 can be used for the valve 80 of Figures 33 and 62, although other types of valves can be used for the valve 80 in other examples. The rotary valve assembly 90 can be used alternatively for the variable restrictor 56, for example, in the fluid pulse generator configurations of FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 and 60, 61 A, 61B. In that case, the rotary valve element 88 corresponds to the restrictor member 54 and the bearing assembly 74 corresponds to the member with openings 58. The rotary valve assembly 90 in example FIGS. 36 and 37 includes the inner mandrel 50, the bearing assembly 74, and the rotary valve element 88. The rotary valve element 88 includes a central internal flow passage 88a and a radially off-center flow passage 88b that intersect. The off-center flow passage 88b also extends through a portion of a bearing wear element 88c. In this example, the wear element 88c may comprise a relatively ductile bearing material selected for sliding coupling with a top face 74b of the bearing assembly 74. Although the wear element 88c may undergo significant wear during operation of the fluid pulse generator 10, the wear element can be conveniently replaced during routine maintenance between jobs. The wear element of bearing 88c is in sliding contact with the upper face 74b of the bearing assembly 74. The openings 74a extend longitudinally through the bearing assembly 74, and at least one of the openings is open to flow at all times, so that fluid communication is continuously permitted longitudinally through the bearing assembly 74. In FIG. 38, it can be seen that a cavity extending circumferentially 74c is formed on the upper face 74b of the bearing assembly 74. The cavity 74c does not extend a full 360 degrees on the upper face 74b. The cavity 74c allows fluid communication between all openings 74a in the bearing assembly 74, so that flow is always permitted through all openings. A portion of the upper face 74b, positioned between opposite ends of the cavity 74c, serves to block flow through the flow passage 88b in the rotary valve element 88, as described in more detail below. In this way, the circumferential distance between opposite ends of the cavity 74c can be varied to correspond to the degree of rotation of the rotary valve element 88 during which the flow passage 88b is blocked by the upper face 74b of the bearing assembly 74. It should be noted that the variable-length connection 98 between the shaft 52 and the inner mandrel 50 allows the rotary valve element 88 to be deflected in contact with the bearing assembly 74 by the flow of fluid 24. Preferably, the rotary valve element 88 is configured so that the bearing stress between the wear element 88c and the upper face 74b of the bearing assembly 74 is acceptably low to reduce wear at this interface, while allowing flow through passages 88a, b to be blocked circumferentially by the upper face 74b between the ends of the cavity 74c. Figures 39, 40, and 41 illustrate representative views of the pulse generator 74. In these views, it can be clearly seen how the circumferential cavity 74c allows fluid communication between the upper ends of the openings 74a. Figures 42 and 43 show top views of the rotary valve element 88 in different rotational positions with respect to the bearing assembly 74. In Figure 42, the rotary valve element 88 is in a rotational position in which the flow passage 88b is blocked by the upper face 74b of the bearing assembly 74. In Figure 43, the rotary valve element 88 is in a rotational position in which the flow passage 88b is not blocked by the upper face 74b of the bearing assembly 74. It should be noted that, regardless of the rotational position of the rotary valve element 88, flow is always permitted through the openings 74a. Another example of the rotary valve assembly 90 is illustrated representatively in FIGS. 58 and 59. In this example, the upper face 74b of the bearing assembly 74 has a concave truncated conical shape. A lower face 88d of the rotary valve element 88 has a complementary shape (e.g., convex truncated conical). In Figures 58 and 59, the rotary valve assembly 90 functions similarly to that in example Figures 34, 35, 36, 37, 38, 39, 40, 41, 42, and 43. Furthermore, the truncated conical shapes of the upper and lower faces 74b and 88d help to align the rotary valve element 88 with respect to the bearing assembly 74. Figures 44, 45, 46, 47, 48, and 49 illustrate representative views of the fluid restrictor element 86. In this example, the fluid restrictor element 86 does not comprise separate moving parts; instead, the fluid restrictor element is capable of producing variable flow resistance in response to fluid flow through it. The bypass flow path 82 also extends through the fluid restrictor element 86 in this example. The bypass flow path 82 is in fluid communication with the flow passages 88a, b in the rotary valve element 88 (see FIGS. 34 and 35). An upper end of the rotary valve element 88 can, for example, be received at a lower end of the fluid restrictor element 86, so that fluid 24 flowing from the bypass flow path flows into flow passage 88a of the rotary valve element. In this example, the fluid restrictor element 86 includes a vortex chamber 92 having a central outlet 94. When flow through the bypass flow path 82 is blocked (such as when the rotary valve element 88 is in the rotary position depicted in FIG. 42), fluid 24 will flow through the vortex chamber 92 to the outlet 94, then through the openings 74a in the bearing assembly 74, and subsequently through the fluid motor 22. As fluid 24 flows through the vortex chamber 92, the fluid flow resistance will alternately increase and decrease as the rotational flow of the fluid in the vortex chamber alternately increases and decreases. The operation of the fluid restrictor element 86 is described more specifically in the U.S. patents cited above. When flow through the bypass flow path 82 is unblocked (such as when the rotary valve element 88 is in the rotating position depicted in FIG. 43), fluid 24 will flow through the bypass flow path, through flow passages 88a, b in the rotary valve element 88, then through openings 74a in the bearing assembly 74, and then through fluid motor 22. It should be noted that flow through the vortex chamber 92 is allowed continuously in this example, but fluid 24 preferentially flows through the bypass flow path 82 when it is unblocked, since the bypass flow path has less resistance to fluid flow. Figures 50, 51, and 52 illustrate another example of the fluidic restrictor element 86. In this example, the fluidic restrictor element 86 includes the bypass flow path 82, the vortex chamber 92, and the outlet 94, but the bypass flow path is in communication with the vortex chamber, so that when the flow through the bypass flow path is unblocked, the creation of a vortex in the vortex chamber is prevented. In FIG. 51, the flow of fluid 24 through the bypass flow path 82 is blocked (such as when the rotary valve element 88 is in the rotating position shown in FIG. 42, downstream of the bypass flow path shown in FIGS. 50, 51, 52). As a result, fluid 24 flows into the vortex chamber 92 and then through the outlet 94. A vortex is created in the vortex chamber 92, thereby increasing the resistance to flow through the vortex chamber. In FIG. 52, the flow of fluid 24 through the bypass flow path 82 is unblocked (as when the rotary valve element 88 is in the rotating position shown in FIG. 43). As a result, fluid 24 can flow unimpeded through the bypass flow path 82 and can also exit the vortex chamber 92 without creating a vortex within it (through a flow path 96 connected to the bypass flow path 82, as well as through the outlet 94). Thus, the resistance to the flow of fluid 24 through the fluidic restrictor element 86 is much lower in FIG. 52 compared to FIG. 51. Figures 53, 54, and 55 illustrate representative views of the fluidic restrictor element 86. In this example, fluid 24 preferentially flows through the bypass flow path 82 when it is unblocked, but the fluid is forced to flow through the vortex chamber 92 when the bypass flow path is blocked. In FIG. 54, the flow of fluid 24 through the bypass flow path 82 is blocked (just as when the rotary valve element 88 is in the rotating position shown in FIG. 42). As a result, fluid 24 flows into the vortex chamber 92 and then through the outlet 94. A vortex is created in the vortex chamber 92, thereby increasing the resistance to flow through the vortex chamber. In FIG. 55, the flow of fluid 24 through the bypass flow path 82 is unblocked (as when the rotary valve element 88 is in the rotating position shown in FIG. 43). As a result, fluid 24 can flow unimpeded through the bypass flow path 82. Thus, the resistance to the flow of fluid 24 through the fluidic restrictor element 86 is much lower in FIG. 55 compared to FIG. 54. Figures 56 and 57 illustrate another example of the fluidic restrictor element 86. In this example, the fluidic restrictor element 86 includes the bypass flow path 82, the vortex chamber 92, and the outlet 94, but the bypass flow path is in communication with the vortex chamber, so that when the flow through the bypass flow path is unblocked, the creation of a vortex in the vortex chamber is prevented. In FIG. 56, the flow of fluid 24 through the bypass flow path 82 is blocked (just as when the rotary valve element 88 is in the rotating position shown in FIG. 42). As a result, fluid 24 flows into the vortex chamber 92 and then through the outlet 94. A vortex is created in the vortex chamber 92, thereby increasing the resistance to flow through the vortex chamber. In FIG. 57, the flow of fluid 24 through the bypass flow path 82 is unblocked (as when the rotary valve element 88 is in the rotating position shown in FIG. 43). As a result, fluid 24 can flow unimpeded through the bypass flow path 82 and can also exit the vortex chamber 92 without creating a vortex within it (via outlet 94 and flow path 96, which is connected to the bypass flow path 82). Thus, the resistance to the flow of fluid 24 through the fluidic restrictor element 86 is much lower in FIG. 57 compared to FIG. 56. In the examples in FIGS. 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, the fluid motor 22 rotates the rotary valve element 88 through the constant velocity joint assembly 76, the inner mandrel 50, and the shaft 52. The flexible joint 72 can be used instead of the constant velocity joint assembly 76 in other examples. As the rotary valve element 88 rotates, flow through the bypass flow path 82 is unblocked for most of each rotation. However, when the flow passage 88b is positioned between the circumferential ends of the cavity 77c, flow through passages 88a and 88b and the bypass flow path 82 is blocked by the upper face 77b of the bearing assembly 77, so that all of the fluid 24 is forced to flow through the vortex chamber 92 of the fluid restrictor element 86. In the example shown in Figures 44, 45, 46, 47, 48, and 49, a vortex is alternately created and collapsed in the vortex chamber 92, such that the flow resistance of fluid 24 through the vortex chamber alternately increases and decreases. A frequency and amplitude of this alternating flow resistance can be selected by the appropriate configuration of the vortex chamber 92 and the associated flow paths communicating with the vortex chamber. In the examples in FIGS. 50, 51, 52, 53, 54, 55, 56, 57, a vortex is created in the vortex chamber 92 when the flow through the bypass flow path 82 is blocked. This increases the flow resistance of fluid 24 through the vortex chamber 92. An amplitude of this increased flow resistance can be selected by appropriately configuring the vortex chamber 92 and the associated flow paths in communication with the vortex chamber. When the flow through the bypass flow path 82 is unblocked, the flow resistance of fluid 24 decreases substantially. In the examples in FIGS. 44, 45, 46, 47, 48, 49 and 53, 54, 55, the flow is preferentially through the bypass flow path 82, so that only a minimal amount of fluid 24 flows through the vortex chamber 92, although a vortex can still be created in the vortex chamber. In the examples in FIGS. 50, 51, 52, 56, and 57, the creation of a vortex in the vortex chamber 92 is prevented when the bypass flow path 82 is unlocked. This is due to the flow path 96 connecting the vortex chamber 92 to the bypass flow path 82. Thus, as the fluid motor 22 rotates the rotary valve element 88, the resistance to fluid flow 24 increases (alternating as in example FIGS. 44, 45, 46, 47, 48, 49, or steady-state as in example FIGS. 50, 51, 52, 53, 54, 55, 56, 57) when the bypass flow path 82 is blocked, and the resistance to fluid flow decreases when the bypass flow path is unblocked. With further reference now to FIG. 62, another example of the fluid pulse generator 10 is illustrated representatively. The example FIG. 62 is very similar to the example FIG. 33. However, in FIG. 62 the fluid pulse generator 10 includes an additional bypass flow path 102 connected in parallel with the bypass flow path 82 and the flow path 84. The bypass flow path 102 allows fluid 24 to flow past valve 80 and fluid restrictor 86. This can be useful when it is not desired for the fluid pulse generator 10 to generate fluid pulses, for example, when hauling drill string 14 into or out of a vertical section of well 16 (see FIG. 1). When it is desired to generate fluid pulses, the bypass flow path 102 can be blocked, thereby forcing the fluid 24 to flow through the bypass flow path 82 and flow path 84, as described above for example FIG. 33. In order to block the bypass flow path 102, a plug 104 (such as a ball, dart, etc.) can be deployed into the bypass flow path 102, such that the plug engages with a seat 106 therein, as shown in FIG. 63. In example FIG. 63, the fluid pulse generator 10 includes an excluder 108 that prevents the plug 104 from entering the bypass flow path 82 or the flow path 84, but allows the plug to enter the bypass flow path 102. A filter or slot 110 in the excluder 108 allows fluid 24 to flow into the bypass flow path 82 and the flow path 84 at all times, but the slot is narrower than one width of the plug 104, so that the plug is excluded from passing through the slot. It will now be fully appreciated that the foregoing disclosure provides significant advances to the technique of generating fluid pulses in underground wells. In several examples described above, a fluid pulse generator 10 generates fluid pulses in response to fluid flow 24 through the fluid pulse generator and a fluid motor 22 connected downstream of the fluid pulse generator. The preceding disclosure provides the art with a fluid pulse generator 10 for use with an underground well. In one example, the fluid pulse generator 10 may include a fluid motor 22 comprising a rotor 36 configured to rotate in response to fluid flow 24 through the fluid motor 22, a variable flow restrictor 56 positioned upstream of the fluid motor 22, the variable flow restrictor 56 comprising a restrictor member 54 rotatable by the rotor 36 relative to a member having openings 58 to thereby variably restrict the fluid flow 24. The restrictor member 54 may be longitudinally displaced with respect to the rotor 36. A variable length connection 98 for transmitting rotation and torque from the rotor 36 to the restricting member 54. The variable length connection 98 may comprise a splined connection. The fluid flow 24 can deflect the restricting member 54 against the member with openings 58. A bearing stress between the surfaces 54a, 58a of the restricting member 54 and the member with openings 58 can increase in response to the fluid flow 24. The surfaces 88d, 74b of the restricting member (e.g., the rotary valve element 88) and the member with openings (e.g., the bearing assembly 74) can have a truncated conical shape, e.g., as depicted in FIG. 58. A flow area for fluid flow 24 through the variable flow restrictor 56 may be open by more than fifty percent in most of each rotation cycle of the restrictor member 54. A flow area for fluid flow 24 through the variable flow restrictor 56 may be open by less than fifty percent in a minority of each rotation cycle of the restrictor member 54. At least one flexible joint 72 and one constant velocity joint 76 may be connected between the restricting member 54 and the rotor 36. The restricting member 54 can rotate and turn around a central longitudinal axis 66 of the fluid motor 22. A bearing section 30 can be connected to the rotor 36 on one side of the rotor 36 opposite the variable flow restrictor 56. ινΐΛ / a / zuzz / ui uooo Another example of the fluid pulse generator 10 may comprise a fluid motor 22 including a rotor 36 configured to rotate in response to fluid flow 24 through the fluid motor 22, a variable flow restrictor 56 positioned upstream of the fluid motor 22, the variable flow restrictor 56 including a restrictor member 54 rotatable by the rotor 36 relative to a member having openings 58 to thereby variably restrict the fluid flow 24, and at least one of a flexible joint 72 and a constant velocity joint 76 connected between the restrictor member 54 and the rotor 36. A splined connection 98 can be connected between the restricting member 54 and the flexible joint 72 or the constant velocity joint 76. A variable length connection 98 is used to transmit rotation and torque from the rotor 36 to the restricting member 54. The fluid flow 24 can deflect the restricting member 54 against the member with openings 58. A bearing stress between the surfaces 54a, 58a of the restricting member 54 and the member with openings 58 can increase in response to the fluid flow 24. The element with holes 58 can surround the restricting member 54 on the outside, for example, as shown in FIGS. 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32. The restricting member 54 can be circumferentially rotated around the member with openings 58, for example, as shown in FIGS. 60, 61 A, 61B. The restrictor member 54 can periodically block the flow of fluid 24 radially through the member with openings 58. The restrictor member 54 can be displaced longitudinally within the member with openings 58. The restrictor member 54 can block an opening 58d formed through the member with openings 58 for less than fifty percent of a rotational cycle of the restrictor member 54. Fluid flow 24 can be allowed continuously through the variable flow restrictor 56. Another fluid pulse generator 10 may comprise a fluid motor 22 including a rotor 36 configured to rotate in response to fluid flow 24 through the fluid motor 22, and a variable flow restrictor 56 positioned upstream of the fluid motor 22. The variable flow restrictor 56 includes a valve 80, 90 and a fluidic restrictor element 86, and the valve 80, 90 is operated in response to the rotation of the rotor 36. The fluidic restrictor element 86 is configured to generate fluid pulses in response to fluid flow 24 through a first fluid flow path 84, and the valve 80, 90 is configured to control fluid flow 24 through a second flow path 82 connected in parallel with the first flow path 84. The first and second fluid paths 84, 82 can be connected upstream of the fluid motor 22. The rotor 36 can be connected to a rotary valve element 88 of the valve ινΐΛ / a / zuzz / ui uooo 80, 90. The rotor 36 can rotate the rotary valve element 88 relative to a bearing assembly with openings 74 in response to fluid flow 24. At least one flexible joint 72 and one constant velocity joint 76 may be connected between the rotor 36 and the rotary valve element 88. A splined connection 98 may be connected between the rotary valve element 88 and either the flexible joint 72 or the constant velocity joint 76. A variable length connection 98 may transmit rotation and torque from the rotor 36 to the rotary valve element 88. The second flow path 82 can extend through the fluidic restrictor element 86. Fluid flow 24 can enter the second flow path 82 upstream of a vortex chamber 92 of the fluidic restrictor element 86, and fluid flow 24 can exit the second flow path 82 downstream of the vortex chamber 92. Fluid flow 24 through the second flow path 82 can avoid the generation of fluid pulses by the fluidic restrictor element 86. A third flow path 102 can be connected in parallel with the first and second flow paths 84, 82. The fluid flow 24 through the third flow path 102 can prevent the generation of fluid impulses by the fluidic restricting element 86. A seat 106 can be formed in the third flow path 102. The seat 106 can be blocked by a plug 104 to prevent fluid from flowing 24 through the third flow path 102. Although several examples have been described above, each with its own specific characteristics, it should be understood that a particular characteristic of one example need not be used exclusively with that example. Instead, any of the characteristics described above and / or depicted in the drawings may be combined with any of the examples, in addition to or in place of any of the other characteristics of those examples. The characteristics of one example are not mutually exclusive of those of another. Rather, the scope of this disclosure covers any combination of any of the characteristics. Although each example described above includes a specific combination of features, it should be understood that it is not necessary to use all the features in an example. Instead, any of the features described above can be used, without also using any other particular feature or features. It should be understood that the various modalities described in this document can be used in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without deviating from the principles of this disclosure. The modalities are described simply as examples of useful applications of the principles of this disclosure, which is not limited to any specific details of these modalities. In the preceding description of representative examples, directional terms (such as “up,” “down,” “superior,” “inferior,” “upward,” “downward,” etc.) are used for convenience when referring to the attached drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any of the particular directions described herein. The terms “including,” “comprising,” “comprising,” and similar terms are used in a non-limiting sense in this descriptive report. For example, if a system, method, apparatus, device, etc., is described as “including” a particular feature or element, the system, method, apparatus, device, etc., may include that feature or element, and may also include other features or elements. Similarly, the term “comprising” is understood to mean “comprising, but not limited to.” Of course, a person skilled in the art, upon careful consideration of the foregoing description of representative embodiments of the disclosure, will readily appreciate that many modifications, additions, substitutions, deletions, and other changes can be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being formed separately may, in other instances, be formed integrally, and vice versa. Accordingly, the preceding detailed description should be clearly understood as being given by way of illustration and example only, the spirit and scope of the invention being limited solely by the appended claims and their equivalents.

Claims

NOVELTY OF THE INVENTION Having described the present invention as above, the following is considered novel and is therefore claimed as property: CLAIMS 1. A fluid pulse generator for use with a subsurface well, the fluid pulse generator being characterized in that it comprises: a fluid motor including a rotor configured to rotate in response to the flow of fluid through the fluid motor; a variable flow restrictor positioned upstream of the fluid motor, the variable flow restrictor including a restricting member which the rotor can rotate with respect to a member having openings to thereby variably restrict the fluid flow; and the restricting member can be displaced longitudinally with respect to the rotor.

2. The fluid pulse generator according to claim 1, characterized in that a variable-length connection transmits rotation and torque from the rotor to the restricting member.

3. The fluid pulse generator according to claim 2, characterized in that the variable length connection comprises a grooved connection.

4. The fluid pulse generator according to claim 1, characterized in that the fluid flow deflects the restricting member against the member with openings.

5. The fluid pulse generator according to claim 1, characterized in that a bearing stress between the surfaces of the restricting member and the member with openings increases in response to fluid flow.

6. The fluid pulse generator according to claim 5, characterized in that the surfaces of the restrictor member and the member with openings have a truncated conical shape.

7. The fluid pulse generator according to claim 1, characterized in that a flow area for fluid flow through the variable flow restrictor is more than fifty percent open in a majority of each rotation cycle of the restrictor member.

8. The fluid pulse generator according to claim 1, characterized in that a flow area for fluid flow through the variable flow restrictor is less than fifty percent open in a minority of each rotational cycle of the restrictor member. IVIA / a / ZUZZ / UI UOOO 9. The fluid pulse generator according to claim 1, characterized in that at least one of the group consisting of a flexible joint and a constant velocity joint is connected between the restricting member and the rotor.

10. The fluid pulse generator according to claim 1, characterized in that the restricting member rotates and turns around a central longitudinal axis of the fluid motor.

11. The fluid pulse generator according to claim 1, characterized in that a bearing section is connected to the rotor on one side of the rotor opposite the variable flow restrictor.

12. A fluid pulse generator for use with a subsurface well, the fluid pulse generator being characterized in that it comprises: a fluid motor including a rotor configured to rotate in response to fluid flow through the fluid motor; a variable flow restrictor positioned upstream of the fluid motor, the variable flow restrictor including a restricting member which the rotor can rotate with respect to a member having openings to thereby variably restrict the fluid flow; and at least one of the assembly consisting of a flexible joint and a constant velocity joint connected between the restricting member and the rotor.

13. The fluid pulse generator according to claim 12, characterized in that a splined connection is connected between the restricting member and at least one of the group consisting of the flexible joint and the constant velocity joint.

14. The fluid pulse generator according to claim 12, characterized in that a variable length connection transmits rotation and torque from the rotor to the restricting member.

15. The fluid pulse generator according to claim 12, characterized in that the fluid flow deflects the restricting member against the member with openings.

16. The fluid pulse generator according to claim 12, characterized in that a bearing stress between the surfaces of the restricting member and the member with openings increases in response to fluid flow.

17. The fluid pulse generator according to claim 16, characterized in that the surfaces of the restrictor member and the member with openings have a truncated conical shape.

18. The fluid pulse generator according to claim 12, characterized in that the member with openings surrounds the restricting member on the outside.

19. The fluid pulse generator according to claim 12, characterized in that the restricting member is circumferentially rotatable around the member with openings.

20. The fluid pulse generator according to claim 12, characterized in that the restricting member periodically blocks the flow of fluid through the member with openings.

21. The fluid pulse generator according to claim 12, characterized in that the restrictor member is longitudinally displaced within the member with openings.

22. The fluid pulse generator according to claim 12, characterized in that the restricting member blocks an opening formed through the member with openings in less than fifty percent of a rotational cycle of the restricting member.

23. The fluid pulse generator according to claim 12, characterized in that the fluid flow is continuously allowed through the variable flow restrictor.

24. A fluid pulse generator for use with a subsurface well, the fluid pulse generator being characterized in that it comprises: a fluid motor including a rotor configured to rotate in response to fluid flow through the fluid motor; and a variable flow restrictor positioned upstream of the fluid motor, the variable flow restrictor including a valve and a fluidic restricting element, the valve being actuated in response to rotation of the rotor; wherein the fluidic restricting element is configured to generate fluid pulses in response to fluid flow through a first flow path, and the valve is configured to control fluid flow through a second flow path connected in parallel with the first flow path.

25. The fluid pulse generator according to claim 24, characterized in that the first and second fluid paths are connected upstream of the fluid motor.

26. The fluid pulse generator according to claim 24, characterized in that the rotor is connected to a rotary valve element of the valve.

27. The fluid pulse generator according to claim 26, characterized in that the rotor rotates the rotary valve element with respect to a bearing assembly with openings in response to fluid flow.

28. The fluid pulse generator according to claim 26, characterized in that at least one of the group consisting of a flexible joint and a constant velocity joint is connected between the rotor and the rotary valve element.

29. The fluid pulse generator according to claim 28, characterized in that a splined connection is connected between the rotary valve element and at least one of the group consisting of the flexible joint and the constant velocity joint.

30. The fluid pulse generator according to claim 26, characterized in that a variable length connection transmits rotation and torque from the rotor to the rotary valve element.

31. The fluid pulse generator according to claim 24, characterized in that the second flow path extends through the fluidic restrictor element.

32. The fluid pulse generator according to claim 24, characterized in that the fluid flow enters the second flow path upstream of a vortex chamber of the fluid restricting element, and the fluid flow exits the second flow path downstream of the vortex chamber.

33. The fluid pulse generator according to claim 24, characterized in that the fluid flow through the second flow path prevents the generation of fluid pulses by the fluidic restricting element.

34. The fluid pulse generator according to claim 24, characterized in that a third flow path is connected in parallel with the first and second flow paths, and the fluid flow through the third fluid path prevents the generation of fluid pulses by the fluidic restricting element.

35. The fluid pulse generator according to claim 34, characterized in that a seat is formed in the third flow path, and the seat is blocked by a plug to prevent fluid flow through the third fluid path.

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