SPECIFICATION

BACKGROUND

The invention relates generally to the oil and gas industry and more specifically to devices and methods to convert pressure pulses into axial movement of a drill string to reduce friction and drag.

Downhole static and dynamic friction can exacerbate drag and weight stacking, whether using a rotary steerable or downhole motor assembly. Drag and weight stacking can lead to tool face control issues in slide drilling, low rate of penetration, high torque, premature buckling, extensive bit wear, short lateral sections, and difficulty in running subsequent casing strings.

There are multiple challenges involved within daily dril ling operations on a global scale today that limit drilling efficiencies and increase lifting costs to the operator. Friction reduction technology has been used to reduce the negative effect of highly inter-bedded formations, ineffective weight transfer , low rate of penetration, sinusoidal and helical buckling, erratic reactive torque, poor tool face control, high tortuosity in extended reach wells and casing running, as well as objects becoming stuck in holes and needing to be fished out. An embodiment, in combination with a shock tool or sub, provides a means to reduce friction between a drill string and a formation or wellbore. Having the ability to reduce static friction negates most of the problems listed above that are widely seen in today's extended reach drilling operations around the globe. SUMMARY

An embodiment comprises a tool placed within a drill string to create a pressure pulse within a drilling fluid system when drilling fluid is being pumped through the drill string, it then converts the pressure pulse into axial movement of the drill string using a shock tool or sub. A valve system in an embodiment alternates the total flow area thereby creating high and low pressure pulses. The shock tool or sub then transforms the pressure pulses into mechanical axial motion along the axis of the drill string to facilitate friction reduction in the wellbore thus allowing the operator to drill further, faster and with more confidence. Drive mechanisms such as positive displacement motors (PDM) and turbines are known in the industry. An embodiment can comprise an axial impeller that spins at high rpm. An embodiment can comprise a cam system that spins with the axial impeller and causes the valve system's rocket to axially reciprocate. Axial reciprocation of the rocket in a venturi then varies the total flow area and generates high and low pressure pulses. Alternating high and low pressure pulses act on the pump open area of a shock tool or sub to generate axial motion along the drill string. Various impeller designs allow the tool to work at different frequencies. Impeller variation enables operation with different types of measurement while drilling tools. Additionally, a bottom sub can be changed out to convert a standard tool to one having an on/off switch. This mechanism engages or disengages the orifice from the rocket as and when required through cycling a mud pump. An increase or decrease in standpipe pressure confirms the position of the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment.

FIG. 2 is a sectional view of an embodiment.

FIG. 3 is a cross sectional view of the lower internals of an embodiment.

FIG. 4 is a cross sectional view of the upper internals of an embodiment.

FIG. 5 is a cross sectional view of an embodiment's sub 35 which turns the tool off and on.

FIG. 6 is a cross sectional view of an embodiment's sub 35 before shearing the pin.

FIG. 7 is a cross sectional view of an embodiment's sub 35 when the tool is activated with no pulsing.

FIG. 8 is a cross sectional view of an embodiment's sub 35 is in reset position.

FIG. 9 is a cross sectional view of an embodiment's sub 35 when the tool is in pulsing position. FIG. 10 is a cross sectional view of an embodiment's sub 35 when it is in reset position.

DETAILED DESCRIPTION

Reduction of friction brings substantial and valuable improvements in the quality of drilling operation. A tool in accordance with an embodiment can change total flow area to create pressure pulses. Alternate high and low pressure pulses act on the pump open area of a shock tool or sub and cause a mandrel on a shock tool or sub to extend and retract at high frequency. A mandrel's axial motion will gently oscillate a drill string and reduce friction between a drill string and a formation. Mechanical axial motion of a shock tool or sub can overcome static friction between mechanically stuck objects.

FIG. 1 is a side view of a drill string's lower end comprising a drill string component 4. Drill string component 4 can comprise a shock tool or sub, drill collar, drill pipe, downhole motor or measurement while drill ing (MWD) tool and is connected to an upper outer sub 1 via API oilfield connection. Upper outer sub 1 is connected to a mid-outer sub 2 via proprietary oilfield connection 21 as illustrated in (FIGS. 1 & 2). Mid outer sub 2 is connected to a lower outer sub 3 via proprietary oilfield connection 24 as illustrated in (FIG. 1 & 3a). Lower outer sub 3 is connected to the top of a lower string component 5 via API oilfield connection. Lower string component 5 (FIG. 1) can comprise a drill collar, drill pipe, downhole motor or MWD tool.

FIGS. 2 and 4 illustrate an embodiment's axial impeller assembly 22 in greater detail. An axial impeller assembly 22 (FIG.2) comprises an impeller sleeve 6 that houses an axial impeller 20.

Impeller sleeve's 6 upper end (FIG.2) is positioned using an upper radial bushing 19 (FIG.2) that is located in mid outer sub 2. As shown in FIG. 4, axial impeller assembly 22 is located in mid-outer sub 2 and rotates freely in mid outer sub 2 (FIG.4).

FIGS. 3a and 4 show assembly 23 comprising a barrel cam sleeve 8 (FIG.3a) that has a barrel cam 10 (FIG.3a) inserted into it and located with three barrel cam followers 17, 25, and 26 which locate into barrel cam sleeve 8. A flow restrictor assembly according to an embodiment comprises: a rocket holder; a rocket; and a venturi.

A rocket holder can be threaded to the lower inner diameter thread of a barrel cam. A rocket can be linked to a rocket holder by threaded connection, such as a male thread on a rocket engaging a female thread on the rocket holder. A venturi is located in a lower sub's hollow interior. When a rocket enters a venturi, total flow area is reduce and pressure increases. When a rocket is out of a venturi, total flow area is increased and pressure is lower. Variation of total flow area results in pressure pulses at the restrictor assembly. Depending on the restriction of the total flow area, the pulse amplitude may be varied and controlled. The rocket holder 12 (FIG.3a) is connected to the lower end of the barrel cam 10 by way of proprietary connection. The rocket 29 (FIG.3a) is then connected to rocket holder 12 (FIG.3a) through a proprietary connection. The lower part of the axial impeller 6 is connected to the upper part of the barrel cam sleeve 8 by way of a proprietary connection 9.

Base plate 14 is located into the pin connection 24 within bottom sub 3 (FIG. 4). The barrel cam retainer 13 (FIG.3a) is located into the pin of connection 24 within the bottom sub 3 (FIG.4), by way of splined keyways. These splined keyways follow through to base plate 14 (FIG.3a)

In FIGS. 1, 2, 3a, and 4 drilling fluid is pumped through the upper outer sub 1 (FIG.l) into an axial impeller sleeve 6 located in mid-outer sub 2 (FIG.4). Axial impeller sleeve 6 contains the axial impeller 20. Drilling fluid flow rotates the axial impeller 20, and thereby rotates axial impeller sleeve 6. Axial impeller sleeve 6 is connected to a barrel cam sleeve 8 via a proprietary connection 9. Barrel cam sleeve 8 rotates on top of a barrel cam retainer 13 (FIG.3a). Three barrel cam followers 17, 25, and 26 (FIG.3a) locate into the barrel cam sleeve 8 and rotate with barrel cam sleeve 8. Barrel cam follower 26 runs in barrel cam profile 11 (FIG.3a), barrel cam 17 runs in the barrel cam profile 27 (FIG.3a) and barrel cam 25 runs in the barrel cam profile 28 (FIG.3a). Cam profiles 11, 27, and 28 (FIG.3a) provide axial motion that can be adjusted to suit the axial travel distance required. The barrel cam 10 is restrained from rotating with barrel cam sleeve 8 by barrel cam retainer 13. Barrel cam 10 can only move axial ly and moves rocket holder 12 and rocket 29 axially (FIG.3a). Rocket holder 12 is connected to the lower part of barrel cam 10 by a proprietary connection. Rocket 29 is connected to the rocket holder 12 by a proprietary connection. While pumping fluid though an embodiment, rocket 29 moves axially in and out of venturi 30 of base plate 14 (FIG.3a). When rocket 29 is positioned out of the venturi 30 maximum total flow area is achieved (FIG.3b). When the rocket 29 is positioned in venturi 30 total flow is reduced (FIG.3a). The increase and decrease of total flow area as shown in FIG. 3a and FIG.3b illustrate the fluid bypass area restricting and unrestricting flow via axial movement of the rocket 29 thereby creating pressure pulses in the fluid. Frequency of pressure pulses is directly proportional to rotation of the impeller 20 which is directly proportional to fluid flow rate through outer upper sub 1. A stator 51 is housed within upper-sub 1 (FIG.4). Flow is directed through stator 51 and directed into axial impeller 20 (FIG.4). Rotation of impeller assembly 22 causes rotation of cam assembly 23 (FIG.4). An example cam assembly comprises: cam housing or sleeve having a hollow interior; a barrel cam, mounted inside the cam housing's hollow interior; one or more cam followers; one or more cam retainers which are placed in the lower sub; top inner diameter threads to connect the impeller assembly to the cam housing/sleeve; lower inner diameter thread to connect the rocket holder. An example cam assembly mounted can be mounted within said lower sub's hollow interior. Cam assembly 23 converts rotational motion to axial motion. Axial motion of cam assembly 23 moves rocket 29 axially in and out of venturi 30, and creates pressure pulses. Pressure pulses can then be used in conjunction with a pressure activated mechanical shock sub or tool. Pressure pulses act on the pump open area of a shock sub or tool creating axial vibration within a tubular string.

An alternative embodiment can comprise bottom sub 35 as shown in FIG.5, instead of bottom sub 3. Bottom sub 35 enables an embodiment to have selective pulsation by activating and de-activating pulses as required.

Sub 35 (FIG.5) is designed to switch an embodiment on or off. Sub 35 comprises a housing for a base plate 14, an indexing barrel 36, a wash pipe 37, a shear pin mechanism/housing 38 and a spring 39 (FIG.5). Base plate 14 is connected to the top of indexing barrel 36. Indexing barrel 36 is a flow or pressure activated body that comprises an indexing profile 40 with three pins 41 inserted into the indexing profile 40 via the sub's outer body 35 (FIG5). The indexing system operates with fluid flow. When pumping fluid through sub 35, fl uid exerts pressure on the upper surface 42 of an indexing system. A shear pin mechanism/housing 38 (FIG.5) is connected to the lower part of an indexing barrel 36 via a proprietary connection. Shear pin 43 is inserted into bottom sub 35 (FIG.5) with an NPT threaded port 44 that is located on the outer diameter of a shear pin mechanism and housing 38. Wash pipe 37 is connected to the lower part of the shear pin housing 38. A preloaded spring 39 is inserted into the annulus between the wash pipe 37 outer diameter and the internal diameter of the bottom sub 35. Spring 39 sits on bottom internal face 46 of bottom sub 35 (FIG.5). Indexing Pins 41 are initially placed in a position half way in profile 40 in relation to the shear pin 43 (FIG. 6). Shear pin 43 is designed to be sheared by a higher flow rate than the drilling flow rate. When shear pin 43 is sheared by a high flow rate, indexing barrel 36 will move downward axially following the indexing profile 40 until it ends in pocket 47 (FIG.7). The initial downward axial motion of indexing barrel 36, with the help of the force exerted by fluid pressure on upper surface 42, will put pins 41 at the highest point of profile 40 (FIG.7) which corresponds to the maximum distance between base plate 14 located in upper surface 42 and rocket 29. In this position, rocket 29 will not enter the venturi 30 and does not change total flow area to create a high pressure pulse. Due to the shape of indexing profile 40, indexing barrel 36 turns clockwise. Turning the pump off, will allow preloaded spring 39 to push the shear pin housing 38 and indexing barrel 36 upward. When the indexing barrel 36 moves upward and clockwise, pins 41 will reach the reset position at pocket 48 as shown in FIG. 8. In this position, indexing barrel 36, upper surface 42, and venturi 30 will be at the closest position to rocket holder 12, hence venturi 30 and rocket 29 will have maximum engagement. As shown in FIG. 9, when pumping fluid again through the string, fluid flow exerts a force on upper ring 42 which pushes indexing barrel 36 downward. While indexing barrel 36 is moving downward and clockwise following profile 40, pins 41 will end up in pockets 49. In this position indexing barrel 36, the upper ring 42, and the venturi 30 will be at an optimum position relative to the rocket holder 12, hence the venturi 30 and the rocket 29 will have an optimum engagement. In this position an embodiment will generate total flow area variation causing pressure pulses. Turning the pump off will allow the preloaded spring 39 to push the shear pin housing 38 and the indexing barrel 36 upward. When the indexing barrel 36 moves upward and clockwise, the pins 41 reach the reset position at pocket 50 as shown in FIG. 8. In this position indexing barrel 36, upper surface 42 and venturi 30 will be at the closest position to rocket holder 12, so venturi 30 and rocket 29 will have maximum engagement. As shown in FIG. 10, when pumping fluid again through the string, fluid flow exerts force on the upper surface 42 which pushes indexing barrel 36 downward. While indexing barrel 36 is moving downward and clockwise, pins 41 will end up in pockets 47 as shown in FIG. 7. In this position indexing barrel 36, upper surface 42 and venturi 30 will be at the furthest distance from rocket 29.

In the embodiment described above, the indexing mechanism will have two reset positions, one disengagement position and one engagement position. In reset positions there is no pulsation as there is no fluid passing through the embodiment. In the disengagement position, there will be no pulsation as the rocket 29 and venturi 30 will have no engagement as shown in FIG. 7. The only position in which the embodiment will start pulsing is when the rocket 29 and venturi 30 are engaged as shown in FIG. 9. In the disengaged position, the total flow area will have less surface pressure indication than when in the engaged position, thus enabling an operator to determine whether an embodiment is in the on or off position.