FIELD

The present description relates to the field of providing a pressure pulse in a pipe line. In particular, the present description relates to a fluid pulse apparatus for use in down hole drilling.

BACKGROUND

The present description specifically discusses generation of a fluid pulse in a down hole drill string. However, it will be appreciated that the concept described herein may be applicable to any fluid line where it is desirable to create a fluid pulse and no limitation is intended thereby.

In the oil and gas exploration and extraction industries, a drill string is lowered into a bore. In such operations a drilling fluid known as "mud" is pumped from the surface through the drill string to exit from nozzles at the drill bit. The mud assists in dislodging and clearing material from the cutting face and carries the dislodged material through the drill bore to the surface.

It is well known in the industry that providing a pulsed fluid flow that can create a percussive or hammer effect can improve the drilling rate. The pulse of fluid flow is generated by periodically restricting the fluid flow so as to create a pressure difference. There are many different methods that have been proposed so as to restrict fluid flow. One principle is to provide turbines, rotors or other means that can be driven by the fluid to operate a valve that can restrict flow. Such valves have an axially reciprocating poppet or piston that can cooperate with a narrowed bore so as to control fluid flow. The reciprocating movement is operated by a cam assembly that is driven by the rotating turbine. Two examples of such a valve arrangement are provided in US 4830122. In the first example, a cam follower or followers are fixed to the upstream end of a turbine for rotation. The follower(s) is operatively associated with a cam that is fixed against rotation. A piston or valve member is mounted to the piston. The action of the cam follower(s) upon the cam causes cyclical reciprocating movement ot the cam and attached piston.

US 4,830,122 also describes an alternate embodiment in which the cam and follower assembly are at the downstream end of the turbine. The cam is fixed against rotation such the cam action that occurs upon rotation of the turbine causes the entire turbine to reciprocate axially. The piston valve member is mounted to the upstream end of the turbine for cooperation with an annular valve ring.

US 4,830,122 also teaches that the percussive effect caused by the pulsing action of the fluid can be further enhanced by connecting the pulse apparatus to a shock tool. A shock tool is a pressure responsive device that expands and contracts in response to varying fluid pressure. Shock tools are conventionally used to isolate the drill string from axial deflections produced by the bit during drilling operations. However, when a shock tool is operatively engaged with a fluid pulse apparatus the expansion and contraction of the shock tool can provide a percussive effect at the drill bit. Since US 4,830,122 has been published, there have been a number of different types of fluid pulse apparatus proposed for use with or without a shock tool. Such further fluid pulse tools have arrangements including rotating plates with axial flow openings that can open and close as a rotor is driven by the fluid.

US 6,279,670 describes a downhole fluid flow pulsing apparatus having a valve member driven by a fluid actuated positive displacement motor to provide a varying fluid flow and a shock tool responsive to the varying fluid flow. Positive displacement motors have a power section comprised of a stator and a rotor. The stator consists of a steel tube that contains a bonded elastomer insert with a lobed, helical pattern bore through the centre. The rotor is a lobed helical steel rod. When the rotor is installed in the stator, the combination of the helical shapes and lobes form sealed cavities between the two components. When drilling fluid is forced though the power section the pressure drop across the cavities will cause the rotor to turn inside the stator. The valve that is operated by the positive displacement motor has a stationary valve plate and a valve plate that is rotated by the motor. The valves each have slots that move in and out of alignment during rotation of the rotatable plate, thereby creating a variable fluid flow. While many of the fluid flow pulse devices described in the prior art have proven to be effective at increasing drilling penetration rates they have a number of disadvantages which has prevented their widespread adoption.

It is well known and appreciated in the drilling industry that it is difficult to design down hole tools which will operate reliably under the constantly changing properties of drilling mud and the constantly increasing hydrostatic pressure at downhole locations. This problem is exacerbated by the small space within which downhole tools must fit. In many drilling situations the downhole tools have an outside diameter of only 4¾ inches. These dimensional restraints impose onerous constraints on the design of such tools.

Further, many down hole tools have polymeric seals or elastomers. Such materials are subject to wear, abrasion by particles in the drilling fluid and can only be operated within certain temperature ranges and cannot be used with non-aqueous chemicals.

Despite the numerous prior art arrangements, there is constant desire in the oil and gas industry to provide fluid pulse apparatus that are cost effective to manufacture whilst being sufficiently robust to withstand the significant adverse operating conditions with minimal maintenance and associated down time. It will be appreciated that drill string downtime can have significant economic disadvantages.

It is therefore an object of the present disclosure to provide an alternative fluid pulse apparatus.

SUMMARY

According to one aspect, there is disclosed a fluid pulse apparatus adapted to be connected to a pipe line, the apparatus comprising; a housing defining a fluid flow passage for a flow of fluid from an upstream end towards a downstream end; a turbine assembly within the fluid flow passage, the turbine assembly having an upstream annular cam surface and a downstream annular cam surface; at least one turbine member that is operatively connected to the upstream annular cam surface and the downstream annular cam surface and that is actuated by a flow of drilling fluid in the fluid flow passage so as to cause rotation turbine assembly; a piston fixed to the upstream annular cam surface or the downstream annular cam surface; the fluid flow passage has a narrowed fluid flow passage section located upstream of the turbine assembly when the piston is fixed to the upstream annular can surface such that the piston is receivable within the narrowed fluid flow passage or the narrowed fluid flow passage is located downstream of the turbine assembly when the piston is fixed to the upstream annular can surface such that the piston is receivable within the narrowed fluid flow passage; at least one upstream cam follower fixed to the housing for cooperation with the upstream annular cam surface and at least one downstream cam follower fixed to the housing for cooperation with the downstream annular cam surface; such that when the turbine assembly is caused to rotate, there is a cam action between the upstream follower(s) and the upstream annular cam surface and between the downstream cam follower(s) and the downstream annular cam surface that causes the turbine assembly to reciprocate axially within the fluid flow passage such that the piston moves between a flow restricting position within the narrowed fluid flow passage and an open position to effect periodic flow restriction of the flow of fluid through the fluid flow passage.

The apparatus may be adapted for connection to any suitable pipe line. Suitably, the apparatus is for connection to a drill string for downhole drilling.

The fluid flow passage has a narrowed fluid flow passage section. The narrowed fluid flow passage section is suitably in the form of a plate with an aperture or orifice.

Suitably the narrowed fluid flow passage defines a venturi.

The narrowed fluid flow passage section can be either upstream or downstream of the turbine assembly. As the piston is receivable within the narrowed fluid flow passage, it follows that if the narrowed fluid flow passage is at the upstream end, the piston is fixed to the upstream annular cam surface and vice versa. Suitably, the piston is fixed to upstream annular cam surface wnich means that the piston moves upwards towards the flow restricting position and downwards towards the open position. In this case, if any debris or other particles in the fluid becomes jammed between the piston and the narrowed fluid flow passage section, the piston may be forced downwards into the open position due to the reduced flow to the turbine assembly and the downward hydraulic force on the piston. The forced downward movement of the piston would allow for the debris to clear so as the apparatus may continue to function.

On the other hand, if the piston is fixed to the downstream annular cam surface the piston moves downwards towards the fluid flow restricting position and upwards towards the open position. In this case, if there is any debris or other particles in the fluid, the piston may become jammed in the flow restricting position due to debris becoming caught between the piston and the narrowed fluid flow passage section. Unlike the situation above, the downward forces continue to force the piston into the jammed position instead of towards the open position. Such jamming may stop the tool from functioning.

Further, when the piston is fixed to the upstream annular cam surface the fluid flow into the turbine assembly is controlled. When the piston is fixed to the downstream annular cam surface the fluid flow out of the turbine assembly is controlled. Flow control into the turbine assembly may be advantageous as this may alleviate pressure build up within the turbine assembly and exposes the turbine member to less adverse forces.

Suitably, the relative dimensions of the piston and the narrowed fluid flow passage are such that the piston cannot fully close the narrowed fluid flow passage section. A complete closure of the fluid flow may cause the turbine assembly to stall.

Suitably where the narrowed fluid flow passage section includes a plate or valve ring, the plate or valve ring are adapted for easy removal and replacement with a plate or valve ring with an orifice of a different size. In this way, the dimensions of the narrowed fluid flow passage section may be tuned for different conditions such as fluid weight and viscosity. In addition to, or alternatively, the piston may be adapted for replacement with a piston of different dimensions.

The apparatus has a turbine assembly that includes at least one turbine member. The at least one turbine member may be any suitable configuration, known in the turbine arts, such as a screw, rotor or the like that can be caused to rotate axially in response to fluid flow. The at least one turbine member is actuated by the flow of drilling fluid through the fluid flow passage.

Suitably the at least one turbine member is a screw such as an Archimedes screw.

The turbine member is operatively connected to the upstream annular cam surface and the and downstream annular cam surfaces such that the respective annular cam members rotate with rotation of the turbine assembly. Such operative connection may be by any suitable means.

Suitably, outer edges of the turbine member(s) are fixed to a turbine sleeve such that the sleeve rotates with the turbine member(s). Such an arrangement is known in the turbine arts. An advantage of having the turbine members fixed to the sleeve is that the sleeve ends can define the annular cam surfaces which can avoid or limit the need for seals, bearings, locating shafts and the like.

Suitably where the turbine assembly includes a turbine sleeve, the turbine assembly does not include a central shaft. Alternatively, the turbine member(s) may be fixed to a shaft and the respective cam surfaces may be fixed to the ends of the shaft.

The present inventor's use of rotating cams acting on fixed followers is opposite to the arrangement described in US 4830122 in which the cams are fixed against rotation and the followers rotate. In the embodiment of US 4830122 when the piston is fixed to the cam, the piston does not rotate. In the apparatus as described herein, because the piston is attached to the cam, the piston rotates. A surprising and unexpected advantage of the rotating piston is that the rotating movement can disperse or cut through any dirt or debris in the fluid that may potentially block the narrowed fluid flow section. Upstream and downstream cam followers are fixed to the housing tor cooperation with the respective upstream and downstream cam surfaces. Suitably, the cam followers are designed so as to apply a symmetrical force to each cam surface.

As the cam follower are fixed and the cam surfaces rotate, the cam action between the rotating cams and fixed followers causes reciprocating axial movement to be transferred to the entire turbine assembly causing the turbine assembly to reciprocate axially.

A pulse generating arrangement described in US 4,830,122 also employs axial movement of the turbine assembly. However, this is achieved using a downstream rotating follower operating against a fixed cam. The upwards motion of the turbine is positively caused by the contact between the cam and follower and the return movement is as a result of gravity. This can generate undesirable shock and instability. It will be appreciated that these forces can be considerable under normal drilling operations in which fluid flow rate can vary significantly for example between 200 gallons per minute and 450 gallons per minute, the pressure may be between 100 psi and 1500 psi and the flow restriction may operate between open and flow restricted positions between about 1 and 3 pulses per second. It will be appreciated that for some applications, the fluid flow rate, pressure and/or periodic restriction cycles can fall outside these ranges. However, the present inventor has surprisingly and unexpectedly discovered that such axial instability can be at least partially ameliorated by providing a turbine assembly with an upstream annular cam surface at the upstream turbine assembly end in combination with a downstream annular cam surface at the downstream end of the turbine assembly. The cam action of the upstream annular cam assembly and upstream fixed cam follower(s) positively returns the turbine assembly to the lowest position rather than relying on gravity. The interaction between the upstream and downstream cams provides a very smooth reciprocating movement of the turbine assembly in which the turbine assembly is always subject to a positive axial force in both directions. Such smooth reciprocating movement reduces or minimises lateral vibration. Lateral vibration can cause damage to other components within the tool itself or other components within the drill string. The cam profiles can be designed so as to provide one or more pulses tor each revolution of the turbine assembly.

The apparatus may be used in a drill string conjunction with a pressure pulse responsive device such as a shock tool that can expand or contract in response to the fluid pressure variation to create axial movement of the drill string.

According to a further aspect, there is described an assembly for delivering a percussive effect in a down hole drill string; the assembly including a fluid pulse apparatus as described in the first aspect and a fluid actuated pressure pulse response device that is actuated in response to the fluid pulse generated by the fluid pulse apparatus.

The pressure pulse apparatus may be placed either upstream or downstream of the fluid pulse apparatus.

According to a further aspect of the invention, there is provided a method of drilling comprising operatively connecting a fluid pulse apparatus as described in the first aspect to a drill string and operating said drill string in a down hole mode.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a schematic view of the lower end of a drill string;

Figure 2 is a schematic cross sectional view of an apparatus of one aspect;

Figure 3 is a schematic cross section of the upper section of the aspect shown in figure 2;

Figure 4 is a schematic cross section of the lower section of the aspect shown in figure 2

Figure 5a is a schematic of the piston in the closed position;

Figure 5b is a schematic view of the piston in the open position; Figure 6 is a schematic cross section of the lower section of the aspect shown in figure 2; Figure 7 is a schematic cross sectional view of an apparatus ot another aspect;

Figure 8 is a schematic cross sectional view of an apparatus of a further aspect;

Figure 9 is a graph showing pulse pressure as a function of time as generated by an apparatus of the present disclosure and Figure 10 is a further graph showing pulse pressure as a function of time generated by an alternate configuration of an apparatus of the present disclosure.

DETAILED DESCRIPTION OF THE FIGURES

Figure 1 is a schematic view of the lower end of a drill string 10 that includes a fluid pulse apparatus 12 of the present invention. The drill string 10 includes a conventional drill string component 14 that may be a drill collar, a drill pipe, a down hole mud motor or a measurement while drilling tool or a shock tool.

The fluid pulse apparatus 12 comprises a housing with an upper sub 16 connected to a lower main body sub 18. The housing defines a fluid flow passage for a flow of drilling fluid from an upstream end towards a downstream end 7. The main body sub 18 is connected to a lower drill string component 20 that can also be any conventional down hole drilling component such as that may be a drill collar, a drill pipe, a down hole mud motor, shock tool or a measurement while drilling tool but not limited to.

Figure 2 shows a schematic cross section of the fluid pulse apparatus 12, with figures 3 and 4 showing details of the upper and lower sections respectively.

The upper sub 16 is connected to the lower main sub 18 through threaded connection 22. The upper sub 16 has a bore 24 defining a fluid flow passage. A bore restriction or narrowed fluid flow section 28 is located at the downstream end of the bore 24.

An orifice plate 26 inserted into the downstream end of the connection 22 down stream of the bore restriction 28.

Figures 2 and 3 show that the flow from the bore restriction 28 through the orifice 26a of the orifice plate 26 is restricted by the head 30 of a piston 32. The piston 32 is moveable between an open position (shown in detail in Fig. 5b) in which there is no fluid flow restriction through the bore restriction 28 and a fluid restricting position (shown in detail in Fig. 5a). As can be seen in Fig. 5a, the fluid flow is not restricted completely as this will cause the turbine to stall, as will be discussed further below.

The orifice plate 26 can be readily replaced with a plate having a different sized orifice. In this way, the apparatus can be adapted for different flow rates, fluid types and mud types.

The head 30 of the piston 32 piston is designed to have a taper so as to reduce the downward hydraulic force exerted on the piston 30 so as to reduce the torque required for rotation of the turbine. The tapered shape of the piston also reduces turbulent flow across the piston so as to achieve a stable and predictable pulse

The main body sub 18 has a radial bushing 40 pressed into the inner diameter. A shaft less helical screw or Archimedes screw 42 is mounted within the main body sub 18 for rotation. Archimedes screws are known to be able to operate under very low heads, are simple in construction, reliable and can tolerate debris. They can also tolerate low fluid levels. This means that an Archimedes screw may still be able to rotate under fluid flows where other types of turbine may stall. This means that the tolerance of the flow restriction may be as small as possible. The smallest possible clearance is desirable so as to maximise the water hammer effect. However, if the clearance restricts the flow completely or too much, the turbine can stall.

The turbine can be adjusted in pitch of the turbine blades so that RPM of the turbine can be tailored to the amount of fluid pumped through it. In one example, a fluid flow of 400 gallons per minute will produce 1 100 RPM but with the turbine pitch adjusted, 250 gallons per minute will produce 1 100 RPM but not limited to. The RPM of the turbine is directly related to the frequency of pulse required.

The outer edges of the screw 42 are fixed to a turbine sleeve 44. The turbine sleeve 44 is fitted into the bushing 40 with a clearance. The upstream and downstream ends of the turbine sleeve 44 are defined by respective cam surfaces 45, 47. The cam surfaces 45, 47 have orifices/apertures defining fluid inlets and outlets into the screw 42.

Opposed pairs of cam pin followers 48, 50; 52, 54 are threaded through the outer walls of the main body and project inwardly into the main body sub 18.

The upper and lower cam surfaces 45, 47 are in contact with the cam follower pins 48, 50; 52, 54 and the sleeve 44 is thereby supported by the lower cam follower pins 52, 54.

In use the fluid flows into the main sub body 18 and causes the screw 42 to rotate as per conventional pulse tools. However, contrary to conventional tools, the present apparatus includes upper and lower cam surfaces that rotate with the turbine.

The cam action of the rotating cam surfaces 45, 47 on the fixed followers causes 48, 50; 52, 54 the screw 42 and turbine sleeve 44 to reciprocate axially and the whole turbine assembly is alternatively positively pushed upwards by the lower cam action and positively pushed downwards by the upper cam action.

Such positive action in both directions imparts a high degree of axial stability to the reciprocating movement. The result is an increase in reliability and tolerance to working angles, varying fluid flows and the like.

The cam profiles can be adjusted so as to adjust the overall axial movement of the piston. This could be from 1 mm movement through to 50mm movement but not limited to. This adjustment can then be used to tune the apparatus so as to achieve a fluid pulse under different conditions.

Fig. 6 shows a schematic view of an alternative main body sub 60. The same features are those discussed above are identified by the same reference numerals. The main body sub 60 has upstream and downstream kaplin turbines 62, 64.

Each turbine 62, 64 has a shaft 66, 68 upon which helical blades 70 are mounted. The blades are fixed to a turbine sleeve 44.

Each shaft 66, 68 is mounted to a cam surface 45, 47. The upper shaft 66 is fixed to a piston 66. In use, we fluid passes from the up stream end to the downstream end, the turbines 62, 64 are caused to rotate in response to the fluid flow, thereby causing rotation of the turbine sleeve and cams 45, 47 in the same manner as discussed above with respect to figures 1 - 5. Figure 7 shows a further aspect of a main sub body 80. The body 80 is similar to that describe above with respect to figures 1 to 5 in having an Archimedes screw 42 attached to a turbine sleeve 44. Upstream and downstream cams 45, 47 are attached to the turbine sleeve 44. In this case, the screw 40 has a shaft 82.

Figure 8 shows a still further aspect of the main body sub 90. The main body sub is similar to that shown in Fig. 8 except that there is no turbine sleeve. The shaft is fixed to the cam surfaces 45, 47 and the cam surfaces are caused to rotate by rotation of the shaft rather than a turbine sleeve.

Figure 9 is a graph showing pulses per second at 700 psi that are created over one second by a fluid pulsing apparatus of the invention pumping 300 gallons per minute. There are 18 revolutions of the turbine apparatus per second and 18 pulses, representing one pulse per revolution.

Figure 10 is a graph of showing pulses per second at 400 psi that are created over one second by the same fluid pulsing apparatus as that used to generate the graph of figure 9, also pumping 300 gallons per minute. There are 9 revolutions of the turbine apparatus per second and 18 pulses, representing one pulse per revolution.

The fluid pulses may be seen to be very consistent in frequency and pulse height. This makes the pulses that this tool creates very easy to filter out so that the pulses do not interfere with other tools such as directional tools and (measurement while drilling) MWD tools. As disused above, the maximum fluid pressure is achieved when the piston is in the fluid restricting position. The narrower the restriction, the greater the increase in pressure. The graph of Figure 10 was achieved with a piston of smaller diameter than that used to generate the graph in Figure 9. It will be appreciated that by simply changing the piston and/or orifice diameter, the fluid pulse apparatus of the present invention can be easily tuned. Further adjustments may be made by adjusting the pitch of the turbine and size ot the piston while using different fluid property and pumping different gallons per minute, it is possible to adjust the frequency of pulse over a second and to adjust the pulse height to create many different configurations tailored to match different conditions. The fluid pulse apparatus does not have any roller bearings or elastomers, such as those found in positive displacement motors that are used to drive valves to produce a pressure pulse as per known devices. The lack of roller bearings and elastomers can extend the life of the apparatus while being used in hot hole conditions and when there is abrasive matter being pumped through the apparatus. Still further without elastomers, non-aqueous chemical fluids can be pumped through the apparatus.

Further, without elastomers or seals, the apparatus can tolerate higher pressures.

As a result of the double cam action, the fluid pulses are very consistent in frequency and pulse height. It is believed that this consistency is as a result of the as a result of the double cam action. This makes the pulses that this tool creates very easy to filter out so that the pulses do not interfere with other tools such as directional tools and (measurement while drilling) MWD tools.

Unlike other fluid pulse apparatus on the market, the flow control components of the present apparatus only move axially. This in turn means that there is no harmful and unwanted lateral vibration created. Those apparatus on the market that use mud motor technology do create lateral vibration that in turn causes damage to other components that make up and are included within the drill string.

The present fluid pulse apparatus can be used with or without a shock tool. An advantage of the present apparatus is that the apparatus without a shock tool can induce a hammer effect on coil tubing which in turn creates axial movement of a drill string.

When the fluid pulse apparatus is used with a shock tool the pulse will react on the pump open area of the shock tool. This will cause the shock tool to axially extend and retract with each pulse. The shock tool can be placed below the fluid pulse apparatus or above the fluid pulse apparatus. If the pump open area of the shock tool is increased, the pulse will have a larger area for the hydraulic force to act upon wnich in turn will increase the axial extend and retract the shock tool. If the pump open area of the shock tool is reduced, the pulse will have less area for the hydraulic force to act upon which in turn will reduce the axial extend and retract the shock tool. This is known as a hammer effect as described in US 4830122.

It will be appreciated that various changes and modifications may be made to the apparatus as described and claimed herein without departing form the spirit or scope thereof.