JPS6143669B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used in wells with borehole water.
Regarding the vibration source for PS well logging, in more detail, by combining a hollow vibrating body and a driving body located inside it and moving them in relative opposite directions, it is possible to prevent negative effects from reaction from appearing on the outside. This is related to the source of the vibration.

PS logging is a method of directly measuring underground elastic wave velocities, that is, P wave (longitudinal wave) velocity and S wave (transverse wave) velocity, in a wellbore and investigating the elastic properties of the underground from these values.

In recent years, highly accurate elastic wave data deep underground has been required from fields such as earthquake engineering and resource engineering. However, as a device for measuring elastic waves deep underground, only the P-wave logging device is in widespread use. This is because P waves propagate at the fastest speed among elastic waves, so it is relatively easy to confirm, whereas S waves have a distinct waveform due to waves that propagate faster (mainly P waves). This is because it is easily detected and difficult to confirm.

On the other hand, as a method for suppressing the radiation of P waves and effectively radiating only S waves, we can create a vibration source in one direction perpendicular to the hole axis by operating a motion mechanism inside the vibration source. A method has been proposed in which force is applied to the hole wall surface as positive and negative indirect pressure via the water in the hole, thereby radiating S-waves with excellent directivity in the direction orthogonal to the source force. 1977-
(See Publication No. 107401). Certainly, this method is an excellent method.

However, the principle of this kind of conventional vibration source is schematically shown in FIG. This is a combination with the probe 4, and the driver 3 is configured to drive the vibrating body 2, so the vibrating body 2
When a force F ₁ is applied to the hole wall 5, a force F ₂ of opposite direction and equal magnitude is applied to the drive body 3 and the probe 4 that is integrated with it.
always acts (reaction), and even with that force F ₂ ,
Force F ₃ acts on the hole wall 5 through the water. In other words, this force F ₃ will act to reduce the effect of F, and will have an adverse effect on the sound source F.

In addition, in order to actually accurately investigate the elastic properties of the underground, it is necessary to observe P waves and S waves at the same location, but using conventional equipment, it is difficult to It is necessary to provide separate sources for P waves and P waves, and in that case, there is no guarantee that P waves and S waves can be excited at the same location in the hole, especially as the depth increases. It is difficult to do so, and since a different vibration source is used, there remain problems with the reliability and error evaluation of data of different physical quantities obtained by combining both observed values.

The present invention was made in view of the actual state of the prior art, and its purpose is to completely eliminate the generation of harmful force due to reaction, and to eliminate the generation of harmful force by external control. , P waves and S
The object of the present invention is to provide an oscillation source for well logging that can also selectively measure waves.

Hereinafter, the present invention will be explained in detail based on the drawings.
FIG. 2 schematically shows the vibration source according to the present invention, and the basic configuration and operating principle will first be explained using it. The source is used in a borehole with borehole water. The probe 14 has a hollow vibrating body 12 that is movable in one direction, and a driving body 13 that is movable in the same direction as the hollow vibrating body 12 is provided inside the probe 14, and both are free from external interference. It is possible to move in relative opposite directions by command. For example, this movement can be realized by disposing a coil winding on the driving body 13 and a magnetic yoke on the hollow vibrating body 12, and utilizing the electromagnetic attractive force between the two.

Suppose now that a force F ₄ is applied from the driving body 13 to the hollow vibrating body 12 and a force F is applied to the hole wall 5 through the water 1 in the hole. At this time, a force F ₅ (=F ₄ ) of equal magnitude and opposite direction is also applied to the driving body 13, but as is clear from FIG. Since it is provided and is not in contact with the borehole water 1, no force harmful to F, such as F ₃ of the prior art, acts on the bore wall 5. In other words, the influence of the reaction is absorbed inside the vibrator, the probe 14 remains stationary, and no disturbance waves are radiated to the hole wall.

In this case, the driving source may be located on either side of the hollow vibrating body 12 or the driving body 13, as long as the force acts on both of them relatively. Further, by controlling the stroke and causing the hollow vibrating body 12 and the driving body 13 to collide, the radiation of P waves can be easily performed. In other words, if driven in a non-colliding manner, the generation of P waves can be suppressed and pure S waves can be radiated (this is based on the same principle as the conventional technology), and if they are caused to collide, this will cause an impulsive pressure change. , P waves can also be observed.

With such a configuration, the first effect is caused by a reaction. It is possible to eliminate the generation of force that is harmful to the sound source, and secondly, by controlling the stroke of the motion between the hollow vibrating body and the driving body, it is possible to radiate only S waves or P waves as well. It is expected that effects such as the ability to selectively measure P waves and S waves are expected.

An embodiment of the vibration source according to the present invention is shown in FIGS. 3 and 4. A cylindrical outermost case 15 is coupled to the probe 14 in a direction perpendicular to its central axis, and the hollow vibrator 12 and the like are housed inside the outermost case 15 . The hollow vibrating body 12 is movably supported in a non-contact manner along the central axis of the outermost case 15 by a spiral leaf spring 16, and the spiral leaf spring 16 is
It is fixed by a ring 17. Now, this hollow vibrating body 12 has a protrusion 20a inwardly at the center and a protruding ring inwardly at the periphery via O-ring seals 19 on both end faces of the cylindrical vibrating body case 18. It has a structure in which a magnetic plunger 20 is screwed in, a vibrating plate 21 is placed on the outside of the plunger, and a non-magnetic set screw 22 is screwed.

Driving body 13 located inside the hollow vibrating body 12
is similarly supported by a spiral leaf spring 23 so as to be movable in a non-contact manner along the central axis of the hollow vibrating body 12 . The driver 13 includes a non-magnetic block 24 located in the center and separating the two magnetic circuits.
, a cup-shaped yoke 26 and a central yoke 27 attached to it by magnetic screws 25, an annular coil 29 wound around a bobbin 28 that is fitted into the gap formed by them, and a holding yoke 30. Become. The yokes surrounding the annular coil 29 (the cup-shaped yoke 26, the central yoke 27, the magnetic screw 25, and the holding yoke 30) have an open magnetic path structure, and the hollow excitation is applied to the open portion of the magnetic path. The shape is such that the central protrusion 20a of the magnetic plunger 20 of the body 12 can be inserted therein. In other words, the drive source in this embodiment is the annular coil 2
9, yokes 25, 26, 27, 30, and a magnetic plunger 20. Therefore, in FIG. 3, if the coil 29 on the right side of the drawing is energized, the hollow vibrator 12 can be driven to the left, and conversely, if the coil 29 on the left side is energized,
The hollow vibrating body 12 can be driven in the right-hand direction. Of course, at that time, the driving body 13 moves in the opposite direction to the hollow vibrating body 12. Further, in order to prevent muddy water from entering the device, it is preferable to cover the end opening of the outermost case 15 with a waterproof sealing material.

Such sources, along with geophones and the like, are inserted into the borehole as a series of sondes. In fact, P waves, S
Figure 5 shows an example of application to wave logging. A weight 40 for facilitating the insertion of the sonde from below, and two stray geophones 41 and 4 each incorporating a vertical motion receiving element for P waves and a horizontal motion receiving element for S waves.
2, a filter tube 43 for blocking in-hole sound waves that interfere with the reception of S waves, and a preamplifier section 4
4. A damper 45 for preventing interference waves propagating through the sonde body, a vibration source 46 according to the present invention, and a vibration source driver 47 for driving the vibration source 46 are successively arranged in this order, and the winch is connected via a sheave 49. Kōi 1 at 50
It is raised and lowered to a predetermined position within 0. Further, a control recording device 52 and a battery 53 are installed on the ground surface.

A block diagram of the measurement system is shown in Figure 6. The transmission of signals and energy between the sonde assembly 54 and the control recording device 52 is performed by a logging cable 55. A measurement mode selection circuit 60 controls the vibration direction N or R and input switches 61 and 62. Power is supplied from the DC high voltage source 64 to the vibration source driver 47 . A shot pulse is applied to the vibration source driver 47 by the shot pulse generator 65 to drive the hollow vibrator 12 in a predetermined N or R direction. By controlling the width of the shot pulse and driving the driving body 13 and the hollow vibrating body 12 so that they do not collide, it is possible to radiate the S wave. If driven, P waves can also be radiated. For reference, FIG. 5 shows the radiation pattern of P waves with the symbol "P" and the radiation pattern of the S waves with the symbol "S". At the same time, the 6-channel waveform storage device 66 is started using the shot pulse. The radiated S waves or P waves are detected by stray geophones 41 and 42, amplified by a preamplifier 44, and then sent to a 6-channel waveform storage device 66 on the earth's surface where they are temporarily stored. A channel electromagnetic oscillograph 67 records on recording paper along with time marks. The S wave can be reliably confirmed because the waveform is reversed by changing the direction of vibration (N and R). Analyzing the velocity distribution of P waves and S waves from these data is performed using the same conventional method.

As described above, the present invention is configured to combine a hollow vibrating body and a driving body housed inside the hollow vibrating body and drive the hollow vibrating body by applying a force between the two. The reaction of the force acting on the body acts on the driving body, and since the driving body is not in contact with the water in the hole, no harmful force based on the reaction acts on the hole wall, and therefore, vibration is not generated. Not only can the efficiency be increased, but also the generation of interference waves can be suppressed.Furthermore, by controlling the excitation stroke, only S waves can be radiated, and the hollow vibrating body and the driving body can collide. For example, P-wave radiation can be easily performed, and P-wave and S-wave selective measurements can be performed using the same oscillation source, providing excellent effects not found in the prior art.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the operating principle of the prior art, Fig. 2 is an explanatory diagram showing the operating principle of the vibration source according to the present invention, and Fig. 3 is a sectional view showing an embodiment of the vibration source according to the present invention. , FIG. 4 is a partially cutaway perspective view thereof, FIG. 5 is an explanatory diagram showing an example of a usage state, and FIG. 6 is an explanatory diagram showing an example of a measurement system. DESCRIPTION OF SYMBOLS 1... Water in the hole, 5... Hole wall, 12... Hollow vibrating body, 13... Drive body, 14... Probe.

Claims (1)

[Claims] 1. In a vibration source that is inserted into a borehole containing water in the borehole and applies an vibration source force to the borehole wall surface in one direction perpendicular to the borehole axis by instantaneously driving a movable body provided inside, The movable body consists of a hollow vibrating body and a driving body housed inside the hollow vibrating body. P waves and S waves without reaction are supported in the hollow vibrating body so as to be movable in the same direction as the hollow vibrating body, and the hollow vibrating body and the driving body are driven in relatively opposite directions. Wave source.