WO1984001834A1

WO1984001834A1 - Seismic pulse generator for a borehole

Info

Publication number: WO1984001834A1
Application number: PCT/FI1983/000068
Authority: WO
Inventors: Calin Cosma
Original assignee: Geotek Oy
Priority date: 1982-11-08
Filing date: 1983-11-07
Publication date: 1984-05-10
Also published as: SE440959B; GB2147700A; NO842724L; CA1211551A; DE3390274T1; SE8406228D0; GB8430281D0; GB2147700B; SE8406228L

Abstract

A signal device for the generation of a seismic pulse, comprising an elongated tubular unit to be fitted in a borehole and consisting of a hammer part (27) and a clamping part (16), said hammer part (27) comprising a hammer (29) for hitting a striking head (28) and said clamping part (16) comprising at least on expander plate (19) extending hydraulically from the wall of said device and serving to lock the device in a borehole at a desired level. Said hammer part (27) is provided with a double-action hydraulic piston (47) whose rod (46) has mounted on its free end a locking bell (37, 38), which during the stroke of piston (47) engages with the hammer pin (32) of said spring-loaded hammer (29) and towards the end of the piston return movement disengages from said hammer pin.

Description

Seismic pulse generator for a borehole.

The present invention relates to a seismic pulse generator for producing seismic pulses in boreholes.

Most of the present-day methods and devices for generating such seismic pulses are based on the use of explosive charges, piezo¬ electric vibrators, electric sparks and similar means which pro¬ duce a seismic signal in a borehole usually filled with water. The S-waves of thus generated signals do not pass through fluid media and therefore such prior art methods are not suitable for S-wave generation.

Borehole clamped devices which are able to produce both P- and S-waves are generally based on a mechanical impact. The prior art devices are either manually activated by means of cables or rods or electrically activated by means of solenoids and magnets However, both types are relatively bulky and require relatively large borehole diameters. They are also relatively weak which in turn means that a relatively high density of boreholes is re¬ quired. These aspects amount to the fact that the prior art equipment is uneconomical for use in preliminary geological surveys.

An object of the present invention is to provide a device which is capable of producing both P- and S-waves at a desired depth in a hole drilled in rock, soil, concrete or similar media.

A further object of the invention is to eliminate the drawbacks occurring when the device is controlled by means of cables, rods and the like from the ground, said drawbacks increasing along with the depth of a borehole.

An object is also to provide a device capable of producing just a single blow each time the device is activated.

A still further object of the invention is to provide when necessary a pulse similar to the preceding one in a manner that pulses can be repeated continuously.

A still further object of the invention is to ensure direct transmission of a produced pulse from the device to the walls of a borehole by using a clamping element that is firmly attach¬ able to the borehole walls.

An object of the invention is also to provide a pulse that is considerably more effective than those produced by manually or electrically powered devices.

The invention can also be applied in small-size boreholes, e.g. in holes whose diameter is 56 mm which is a standard borehole size in geological surveys at least in Europe.

A still further object of the invention is to provide a pulse either uphole or downhole, this feature being very important in S-wave analysis.

A still further object of the invention is to provide a device for detecting and transmitting about the blow moment up to the ground.

In addition, the device of the invention is lightweight and thus readily transportable.

A final object of the invention is to provide a device capable of preventing the water in a borehole from penetrating into the de¬ vice which would considerably cut down the power of a blow.

The above objects are accomplished by means of a seismic pulse generator according to the invention, comprising an elongated tubular unit insertable in a borehole and consisting of a hammer element and clamping element, said hammer element comprising a hammer for hitting an anvil and said clamping element comprising at least one locking or clamping means extending hydraulically from the wall of said device and serving to clamp the device in a borehole at a desired level, said device being characterized in that said hammer element is provided, with a double-action hydraulic piston whose rod has at its free end a locking bell for locking itself during the piston stroke in the clamping pin of a spring-loaded hammer and towards the end of the piston return stroke disengages its grip from said clamping pin.

In a preferred embodiment of the invention, the clamping elemen or body is provided with a wedge means mounted on a hydraulicall displaceable piston and having its wedge surfaces actively engaged with the wedge surfaces of said locking or expander plate whereby, when said wedge means is displaced in the long- itusinal direction of said clamping body, the spring-loaded expander plate moves radially outwards from the clamping part body.

Other characteristics of the invention are set forth in the annexed claims 3-7.

The invention will now be described in more detail with referenc made to the accompanying drawings, in which:

fig. 1 shows one gable of a device of the invention,

fig. 2 is a side view of the gable shown in fig. 1 ,

fig. 3 is a section along the line III-III in fig. 1,

fig. 4 is a section along the line IV-IV in fig. 2,

fig. 5 shows the central part of a device of the invention,

fig. 6 is a section along the lineVI-VI in fig. 5,

fig. 7 shows the other gable of a device of the invention,

fig. 8 shows a control cable coupling element for a device of the invention, fig. 9 is a section along the line IX-IX in fig. 8,

figs. 10-13 show in a larger scale a detail about setting up and triggering the hammer, and

fig. 14 shows a combination of figs. 1, 5 and 7 of a device of the invention.

First explained is the design of a device of the invention. A device of the invention is an elongated cylindrical element or body, comprising two connected parts or bodies, namely a clamping part body 16 and a hammer part body 27. The free end of said clamping part body is fitted with an endcap 8 provided with a waterproof electric connector 7 for a shock microswitch 9 locat¬ ed in said endcap. Endcap 8 is sealed against clamping part body 16 by means of seals 10 compressed against the body by means of its fastening bolt 11. Fastening bolt 11 is provided with a through-passage which joins a hydraulic fluid supply passage 2 in said endcap. Endcap 8 is further provided with another pass¬ age 1 for hydraulic fluid, said passages in turn being in com¬ munication with respective passages made in body 16. In endcap 8 the terminations of passages 1 and 2 have seals 22.

Endcap 8 of the above-described device is fitted with a control cable connection element 4, provided with a switch means 5 which is intended for electric connector 7 and from which an electric lead is passed up to the ground along a combined instrument cable 3. Endcap 8 is shown in cross-section in fig. 9 and it is also provided with hydraulic circuit passages 1 and 2 as well as with a fastening bolt 6 for connection element 4. At this stage we wish to point out that this connection element 4 can be alter¬ natively mounted on the other end of the device.

Clamping part body 16 is provided with a cylinder space contain¬ ing a reciprocating piston 12 and its rod 13 which extends thro¬ ugh a securing bolt 15 fitted sealing cap 14 from said cylinder space to a slide space adjacent thereto. This slide space accom¬ modates a wedge means 17 fixed to piston rod 13. The wedge surf- aces of wedge means 17 support the wedge surfaces of an associ¬ ated expander plate 19 in a manner that, when wedge means 17 slides forward (right in the fig. 2 case) in said slide space, said expander plate 19 works its way radially outwards from body 16 by the action of wedge surfaces as well as against the action of springs 18. On the opposite side to said expander plate, the periphery of said body is provided with a spacer plate 20 secure to the body by means of fastening bolts 21. Springs 18 are also secured to this spacer plate. This design is shown in more detail in fig. 4 which also illustrates hydraulic circuit pass¬ ages 1 and 2 in the side portion of body 16. The dimensions and shape of spacer plate 20 are chosen according to the size of any given hole that is surveyed.

The above-described clamping part 16 is fastened to a hammer part body 27, this joint being sealed with seals 23. The joint is further fitted with seal spacers 24 provided with apertures aligned with the mouths of said pressure fluid supply passages 1, 2. To ensure the joint, said hammer part 27 is provided with two mounting parts 25, 26 fixedly mounted on the body. Clamping part 16 is fastened to the outer mounting part 25 by means of screwthreads. This mounting part 25 is sealed against hammer part body 27 by means of seals 23 and 24. The other mounting part 26 is fitted with.-bi_.£fe£s 3Q.

One end of mounting part 26 is fitted with the striking head 28 of hammer 29. Hammer 29 comprises a relatively large hammer body, the end of which opposite to said striking head comprises a narrower rod portion terminating in a hammer locking pin 32. At the hammer neck portion there is a set of springs 31 whose one end bears upon the hammer body and the other end bears upon the front face of a locking bell 37, the latter forming one termination of the hammer displacement space. Said locking bell 37 comprises an outer part 37 which is fixed relative to body 27 and an inner part 38 which is movable thereon. The inner locking bell part -38 comprises a cavity for receiving said hammer locking pin 32. This cavity is provided with locking balls 33 squeezing behind the ridges of hammer pin 32. Said inner locking bell part 38 is further provided with a locking ■bell pin 35 against which spring 39 is supported. The outer locking bell part 37 in turn is provided with another locking bell pin 36 against which the other end of spring 39 is support¬ ed.

The termination area opposite to said locking balls 33 of inner locking bell part 38 is provided with a stopper means 40 serving to prevent the end portion of the hammer piston rod reciprocat¬ ing within said inner part 38 from coming out of said inner part 38.

Piston rod 46 travels through a stopper part 41 which forms the extension of locking bell 37. Stopper part 41 is secured to body 27 with fastening bolts 43 and by means of seals 42 as well as seal spacers 44 and their fastening bolts 45. Stopper 41 builds the other termination for the displacement area of piston 47 mounted on the free end of piston rod. In body 27, the press¬ ure fluid passages 1 and 2 are directed in a manner that passage 2 terminates in the cylinder space near said stopper part 41 and passage 1 terminates near the opposite end of said cylinder space.

The other end of said cylinder space consists of an endcap 50 mounted on said body 27. This endcap 50 is fitted with seals 48, which correspond to seals 10 of clamping part 16, as well with a fastening bolt 49 for said seals, the latter bolt in turn corresponding to bolt 11 of clamping part 16. This endcap 50 is of the same shape as the clamping part endcap 8, so both of these components can be suitably fitted with a cable connector 4. However, in the case shown in fig. 7, said endcap 50 is fitted with a blind cap 51, secured with a fastening bolt 52 to endcap 50. Said blind cap 51 is further provided with a through-hole 53 for electric connector 7 when said blind cap 51 is used as a cable termination for connection to device.

Thus, as pointed out in the above description, the device of the

OMPI invention comprises two substantially cylindrical parts, i.e. a hammer part body 27 as well as a clamping part body 16. The free ends of both parts are similarly designed so that each end of the device can be fitted with a cable connection piece 4 and a blind cap 51. Such arrangement will be capable of producing a pulse both downhole and uphole. Two hydraulic fluid passages 1 and 2 extends along the sides of both parts from part to part, the sealing being ensured at joint sections by means of a sealin system 10, 23, 48.

Cable 3 contains two hydraulic fluid supply lines as well as an electric cable for detecting a pulse as well as possible other connecting lines. The mechanical joint of hammer part 27 and clamping part 16 is accomplished with rubber buffer means 30 in a manner_^ that during the impact the hammer part mass does not affect the transmission of a pulse to the walls of a borehole.

Operation of the device of the invention proceeds as follows:

As a pressure fluid is supplied into the passages, the pressure fluid discharging from passage 1 causes the displacement of piston 12 to its leftmost position (figs. 1 and 2 ) . By the act¬ ion of piston rod 13, this displacement also moves the wedge part to its leftmost position while, at the same time, expander plate 19 pulls itself by the action of springs 18 to its inner¬ most position. At the same time, the pressure discharging from passage 1 urges piston 47 to the left, whereby said locking bell 37 moves also to the left by the action of locking bell pin 36 compressing said spring 31 (fig. 10). This leftward displace¬ ment of the locking bell proceeds thus compressing springs 31 until said hammer pin 32 meets said locking bell balls 33 in the inner locking bell part 38. After this, said inner locking bell part 38 does not continue the displacement but the outer part 37 moves to the left with respect thereto. Said spring 39 mounted between locking bell pins 35 and 36 tightens and, as the dis¬ placement continues, locking bell balls 33 meet recesses 34 made in said outer part 37 and sqeeze themselves into these recesses. Thus, said hammer pin 32 is capable of passing locking bell balls 33 towards inner locking bell pin 35. After said hammer pin 32 has passed them,- said locking bell balls drop again out of their recesses behind pin 32 at the same time causing^*inner part 38 moves to some extent along with outer part 37. At the same time, the end of pin 32 hits stopper rod 35 and the displacement stops.

As this situation is reached, pressure in the device will rise giving notice to the operator on the ground that the device is loaded. Hence, the flow in fluid passages is reversed in a man¬ ner that the fluid on the opposite side of pistons 12 and 47 will return to a pressure tank on the ground. This is followed by the pressurization of passage 2 causing pistons 12 and 47 to move simultaneously to the right. Due to this action, wedge part 17 moves rightwards in contact with expander plate , the wedging action causing said expander plate to extend radially from body 16 into engagement with the wall of a borehole. The spacer plate 20 on the opposite side of said expander plate urges against the opposite wall of said borehole. As pointed out above, the thick¬ ness and shape of spacer plate 20 are chosen according to the diameter of a surveyed borehole. Thus, the device can be readily employed in boreholes of vaious sizes.

Now, piston 47 will also move rightwards and,on reaching a stoppe 40 mounted on inner locking bell part 38, it will pull along the entire locking bell assembly 37, 38, hammer 29 as well as the compressed springs 31.

At the same time, pressure keeps increasing on the left side of piston 12 making said expander plate 19 urge still more firmly against the wall of a borehole.

As piston 47 and its rod 48 move rightwards (figs. 12, 13), the locking bell assembly meets stopper part 41. Thus, the movement of outer part 37 stops but piston 47 proceeds and so does said inner part 38 connected to the locking bell piston rod 46, said inner part pulling along hammer 29 by means of locking bell balls 33. As the displacement continues, said locking bell balls 33 meet recesses 34 and fall therein releasing their grip from hammer 29 with the result that the force of springs 31 will hurl said hammer 29 towards anvil or striking head 28 for the generat ion of a desired pulse.

To encourage its impact, said hammer 29 is provided with length¬ wise slots 54 facilitating air passage along these slots (fig. 6

The inertial mass of wedge part 17 provides a highly firm contac between expander plate 19 as well as spacer plate 20 and the walls of a borehole.

At the moment of impact, a built in shock microswitch 9 breaks the electric contact and so triggers a measuring or recording unit on the ground.

With piston 47 in its rightmost position, the movement stops and pressure increases. This indicates to the operator that the shock has taken place and pressure can be re-supplied to passage 1 and the operating cycle can be re-started from the start posit¬ ion.

The above description deals with one embodiment of the invention to which the invention is by no means limited. For example, it has been said above that the operator on the ground can conclude from the increase of pressure that the device is loaded and thus pressurize the other hydraulic circuit etc. In this respect, however, it must be appreciated that the operation may be fully automatic.

Claims

1. A signal device for the generation of a seismic pulse, comprising an elongated tubular unit to be fitted in a borehole and consisting of a hammer part (27) and a clamping part (16), said hammer part (27) comprising a hammer (29) for hitting a striking head (28) and said clamping part (16) comprising at least one expander plate (19) extending hydraulically from the wall of said device and serving to lock the device in a borehole at a desired level, c h a r a c t e r i z e d in that said hammer part (27) is provided with a double-action hydraulic piston (47) whose rod (46) has mounted on its free end a lock¬ ing bell (37, 38), which during the stroke of piston (47) en¬ gages with the hammer pin (32) of said spring-loaded hammer (29) and towards the end of the piston return movement disengages from said hammer pin.

2. A device as set forth in claim 1, c h a r a c t e r i z e d in that said clamping part (16) is provided with a wedge part (17) mounted on a hydraulically displaσeable piston (12) and having its wedge surfaces actively associated with the wedge surfaces of expander plate (19) , the displacement of said wedge part-in the longitudinal direction of clamping part (16) causing said spring-loaded expander plate (19) to move radially out¬ wards from the body of clamping part (16).

3. A device as set forth in claim 1 or 2, c h a r a c t e r ¬ i z e d in that said locking bell (37, 38) consists of an inner part (38) mounted freely on the end of a rod (46) and an outer part (37) for relative movement therewith, said inner part (38) being provided with a space receiving said hammer pin (32) and fitted with locking bell balls (33) , said outer part (37) being provided with recesses (34) for locking bell balls (33), said balls (33) being engaged behind hammer pin (32) and disengaging their grip by falling into said recesses (34) by virtue of the relative displacements outer part (37) and inner part (38) .

4. A device as set forth in claim 1, 2 or 3, c h a r a c t e r i z e d in that said clamping part (16) on the opposite side of expander plate (19) is fitted with a removable spacer plate (20)

5. A device as. set forth in any of the preceding claims, c h a r a c t e r i z e d in that said locking bell (37, 38) consists of an outer part (37) movable inside said hammer part (27) and having its inner wall near its hammer facing end provided with recesses (34) for locking bell balls (33) and spaced from these recesses with a fixed locking bell pin (36) , said inner part (38) beingmovably mounted inside said outer part (37 whereby, spaced from the locking bell balls, said inner part (38 is provided with a locking bell pin (36) for blocking the insert ion of hammer pin (32) , with recesses for said locking bell pin (36), as well as with a stopper (40) at the end opposite to said balls for preventing the pullout of piston rod (46).

6. A device as set forth in any of the preceding claims, c h a r a c t e r i z e d in that the bodies of both clamping part (16) and hammer part (27) are provided with combined supply passages (1, 2) of a hydraulic fluid, said passages being in communication with the supply passages of a connector element (4

7. A device as set forth in any of the preceding claims, c h a r a c t e r i z e d in that the free ends of both clamp¬ ing part (16) and hammer part (27) are provided with mountings of equal shape, and that the device connector element (4) can be coupled to either one of said free ends.

8. A device as set forth in any of the preceding claims, c h a r a c t e r i z e d in that the joint section between clamping part (16) and hammer part (27) is fitted with buffer means (30) .