JP2875172B2 - Multi-stage downhole hypocenter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies an impact force to a laminated portion in which a large number of plate members and elastic members are alternately laminated, and discharges water in a hole between the plate members outward by deformation of the elastic members. The present invention relates to a high-power downhole hypocenter that generates elastic waves on a hole wall. More specifically, the present invention provides:
The present invention relates to a multi-stage type downhole hypocenter in which a plurality of the above-mentioned stacked portions are arranged in the stacking direction, and a striking force is applied to each of the stacked portions at the same time to improve the excitation force. This wellbore hypocenter is an effective device for tomography for three-dimensional analysis of ground vibration characteristics over a wide area, in addition to a velocity logging system in a borehole.

[0002]

2. Description of the Related Art In order to investigate the elastic properties and the like of an underground ground, a PS velocity logging system that directly measures an elastic wave (P wave or S wave) propagation velocity in a borehole drilled in the ground is used. Have been. This velocity logging is a technique for obtaining the arrival time of an elastic wave from a hypocenter to a geophone as a waveform record.

[0003] Conventionally, various downhole hypocenters have been developed. These are basically structures having a movable body (hammer) movable in a direction perpendicular to the hole axis and a drive mechanism for driving the movable body. The hypocenter is installed in a borehole having water in the borehole, and the movable body is instantaneously driven to apply an exciting force to the wall surface of the borehole in one direction perpendicular to the borehole axis. Usually, an electromagnetic solenoid is used as the drive mechanism.

However, this type of conventional electromagnetic hammer-type downhole hypocenter is driven by an electromagnetic solenoid, and generally has a relatively small boring hole diameter, so that the outer diameter of the hypocenter cannot be increased. Limited scope. For example, it is effective when a hypocenter and a geophone are incorporated in a series of probes, and this probe is inserted into a borehole without being fixed to a hole wall to perform PS logging at each depth. However, in the case of an inter-hole velocity measurement using two boring holes, the propagation range of vibration is narrow and it is difficult to apply.

In recent years, a technique of tomography which measures elastic wave velocity between two boreholes and three-dimensionally expresses vibration characteristics (tomographic imaging) over a wide range of the underground ground by making full use of data processing by a computer. Is being introduced. In this case, first, one boring hole is used as an exciter hole, the other boring hole is used as a receiving hole, an epicenter is installed in the exciting hole, and a multiple-type geophone is inserted into the receiving hole, and the location of the epicenter ( While changing the depth, the exciter hole and the receiver hole are exchanged, and the elastic wave velocity is measured. However, with the conventional electromagnetic hammer-type downhole source as described above, signals can only reach when the distance between boring holes is about 10 m or less. I can't.

The inventor of the present invention has previously laminated a large number of metal annular plates and elastic members such as rubber O-rings and wave washers alternately, and dropped a weight toward the laminated portion to strike. By applying force, the elastic member is deformed and water in the hole between the annular plates is discharged outward, and a weight falling downhole hypocenter that can generate elastic waves on the hole wall was developed ( Japanese Patent Laid-Open No. 5-
203759). The hypocenter in the wellbore can increase the fall energy by increasing the weight and fall distance of the weight or by driving it with a spring, etc., and as a result, a relatively large vibration force can be generated even with a small casing diameter,
Further, since the generated vibration contains many high frequency components, there is an advantage that the resolution is improved.

[0007]

This hypocenter is very effective. However, in fields such as petroleum exploration, there is a demand to further increase the vibrating force. Therefore, in order to further increase the vibrating force, the number of stacked annular plates was increased, and as a result of studying the prototype, as a result, when the number of stacked annular plates became a certain number or more, even if the number of stacked annular plates was further increased, the vibration was increased. It was found that the generation efficiency did not improve. In other words, in the downhole hypocenter of the above-mentioned weight falling type, although the excitation force is remarkably improved as compared with the conventional hypocenter, there is a certain limit. As a result of various studies on the cause, it is considered that since the elastic member is interposed between the annular plates to be laminated, when the number of laminated layers increases, the impact force is attenuated while being transmitted.

By the way, there is a gunpowder as a conventionally known epicenter having a large vibrating force. When gunpowder is used, elastic waves reach even when the distance between the boring holes is about several hundred meters. However, the use of gunpowder has a problem of causing collapse of the borehole wall. Although it is possible to move the exciter point sequentially from the deeper part to the shallower part of the boring hole, when exchanging the excitable hole and the receiving hole for measurement, the excitable hole has already collapsed Therefore, it cannot be used for the receiving hole, and as a result, necessary measurement cannot be performed. In addition, explosives have many restrictions on use, and it is almost impossible to use explosives, especially in urban areas.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to obtain an extremely large vibrating force even with a small bore diameter, and to include a high-frequency component to provide high resolution.
It is to provide a safe and easy to use downhole hypocenter.

[0010]

An underground seismic source according to the present invention has a laminated portion in which a number of plate members are laminated via an elastic member, and applies a striking force to the laminated portion in the laminating direction. It is premised on a method of causing vibration. The feature of the present invention is that a plurality of the above-mentioned laminated portions are arranged in the laminating direction via a connection portion having an air pocket, and a striking plate is provided on one end face of each of the laminated portions, and between each striking plate. Are connected by a striking rod. For example, it is possible to assemble the plate member and the elastic member in a ring shape, and insert the support column through the center hole so as to restrict the movement in the plane. The number of stacked parts is two (2
Step) The above is optional, but preferably about 7 steps.

The elastic member is made of, for example, a ring made of a rubber-like substance (for example, an O-ring having a circular cross section or a rubber bush having a rectangular cross section), a wave washer having a spring property (wave washer), or the like. A structure in which about ten metal annular plates are laminated via an elastic member. The connecting portion between the laminated portions is formed of a covered cylindrical member whose inside is an air reservoir, and has a structure in which the covered cylindrical member is fixed to the column. Above the stacking part, pull up and hold the weight
A release mechanism is provided. Although a method using a natural fall may be used, it is preferable to incorporate a spring mechanism for imparting a downward elastic force to the weight and forcefully drop the weight to further increase the vibrating force.

[0012]

The striking force due to the falling of the weight is directly transmitted to the next striking plate by the striking rod, so that the striking force is simultaneously applied to each laminated portion. The striking force causes the elastic member to be rapidly deformed, and each laminated portion including the plate member and the elastic member contracts in the laminating direction. As a result, water in the holes existing between the plate members is rapidly pushed outward, and elastic waves are generated on the hole walls.
By limiting the number of laminated plate members in each laminated portion to such a degree that the impact force is effectively transmitted, the entire laminated portion effectively contributes to vibration generation. The total vibrating force is improved by the presence of a plurality of such laminated portions.

[0013] The air pocket provided at the connection between the laminated portions facilitates movement of the striking plate therebelow, and serves to prevent a drop in striking efficiency. If there is no air pocket, water in the hole is drawn in from the outside by the displacement of the striking plate, and the displacement of the striking plate is hindered, and the striking efficiency is reduced.

[0014]

FIG. 1 is an explanatory view showing the basic configuration and operation of a hypocenter within a wellbore according to the present invention. This embodiment is a two-stage type, in which two laminated portions 10a and 10b are arranged in the axial direction. The lower stacked portion 10a has a configuration in which a large number of metal annular plates 12a and rubber O-rings 14 are alternately stacked, and the upper stacked portion 10b also has the same configuration as the metal annular plate 12b. In this configuration, rubber O-rings 14 are alternately stacked. A connecting portion 18 having an air reservoir 16 is interposed between the lower and upper stacked portions 10a and 10b. An upper striking plate 20 and a lower striking plate 21 are located at the upper ends of both laminated portions 10b and 10a, respectively, and are connected by a plurality of lower striking rods 22 having high rigidity. Striking plate 2 for laminated portions 10a, 10b or upper and lower stages
With respect to 0, 21 and the like, the movement of the in-plane direction is performed by the column 24 penetrating through the center hole thereof, and is held on the support body 26 at the lower end. Although not shown, a mechanism for applying a striking force to the upper striking plate 20 is provided.
This may use, for example, the fall of a weight.

When a striking force is applied in the outline arrow direction by dropping a weight or the like from the state shown in FIG. 1A, not only the upper striking plate 20 but also the lower striking plate 21 is struck by the lower striking rod 22. At the same time, the impact force is transmitted. Then, as shown in FIG. 1B, each of the laminated portions 10a, 1
0b of the rubber O-ring 14 is rapidly deformed,
Each of 0a and 10b contracts entirely in the laminating direction (the direction of arrow b). As a result, the water in the holes existing between the annular plates 12 is pushed outward (in the direction of the white arrow c),
An elastic wave will be generated on the hole wall (not shown).

FIG. 2 is a detailed view showing an embodiment of the multi-stage downhole hypocenter according to the present invention. Since the basic configuration is substantially the same as that of FIG. 1, corresponding portions are denoted by the same reference numerals for easy understanding. In this downhole hypocenter, a support 26 is fixed to the lower end of a column 24 located at the center, and the lowermost stacked portion 10a, the connecting portion 18, and the second stacked portion 10b are sequentially arranged thereon. The upper layered portion has the same configuration as the second layered portion 10b. The number of layers in the laminated portion is, for example, seven. A striking plate 21 is placed on the upper end of each of the laminated portions 10a and 10b, and three striking rods 22 are symmetrically arranged therebetween. Therefore, these three striking rods 22 penetrate through the laminated portion 10b and the connecting portion 18.
The laminated portion 10a is formed by laminating ten metal annular plates 12a via a rubber O-ring 14.
Similarly, 0b is obtained by laminating ten metal annular plates 12b via rubber O-rings 14. The lamination state is shown in FIGS. 3A and 3B as exploded perspective views. The annular plate 12a constituting the lowermost laminated portion 10a may be a simple annular shape, but the annular plate 12b constituting the uppermost laminated portion 10b is penetrated by the three striking rods 22 as described above. For this reason, three holes 40 are formed at symmetrical positions. The inner diameter of each hole 40 is slightly larger than the outer diameter of the striking rod 22, so that each annular plate 12b can be freely displaced in the stacking direction.

The connecting portion 18 is formed of a cylindrical member having a lid, and has three holes formed in the lid, and small cylinder portions extend downward from the periphery of each hole. 22 is penetrated. With such a covered cylindrical structure, the inside upper part of the connecting part 18 becomes a sealed space, and the inside is an air reservoir 16. This connecting portion 18 is
Is fixed by a copper ring 19 at a predetermined position. The inner diameter of the small cylindrical portion is slightly larger than the outer diameter of the striking rod 22, so that the striking rod 22 can be freely displaced in the axial direction.

The upper end of the center support post 24 is
And a cap member 32 is attached to the upper holding body 30. Above the uppermost striking plate 20, striking rods 34 are respectively arranged at positions corresponding to the striking rods 22. The striking rods 34 penetrate the upper holding body 30 to regulate the position in a plane perpendicular to the axis. Have been. A common hitting body 36 is mounted on the upper end of each hitting rod 34, and is held by the upper holding body 30 and the cap member 32. The upper holder 30 and the cap member 32
O-ring seals are arranged at necessary places, such as between the striker 36 and the striking body 36, to maintain watertightness.

In this apparatus, when a striking force in the direction of the outline arrow a is applied to the striking body 36, the striking force is simultaneously transmitted to all the striking rods 34, and further, all striking rods 32 through the uppermost striking plate 20. It is transmitted to at the same time. As a result, in each of the laminated portions 10a and 10b, the rubber O
The ring 14 is rapidly deformed and contracts simultaneously in the stacking direction. As a result, the water in the holes existing between the annular plates 12a and between the annular plates 12b is rapidly pushed outward, and elastic waves are generated on the hole walls.

The results of various basic experiments for finding the optimal structure of the downhole hypocenter of the present invention will be described. FIG.
The figure shows the relationship between the number of circular plates and the relative amplitude for a single-stage epicenter. From this result, the number of annular plates is 1
If the number is zero or more, the relative amplitude is saturated, and the effect of increasing the number of sheets is not produced. This is presumably because the elastic member is interposed between the annular plates, so that when the number of laminations increases, the impact force is attenuated during transmission. Therefore, although the optimum number of sheets is considered to vary depending on the size and shape of the annular plate and the material and structure of the elastic member to be interposed, the relative amplitude hardly changes even if the number of laminated sheets is increased from the optimum number. Next, FIG. 5 shows the relationship between the number of stages of the laminated portion and the amplitude ratio. The amplitude ratio increases as the number of stages increases.
However, as the number of steps increases, the length of the epicenter increases, so that the location of the epicenter has a certain range, which causes a problem that measurement accuracy is reduced. Therefore, in practice, the number of the annular plates in each laminating portion is set to 10, and a structure in which the circular plates are stacked in seven stages is practically used.

FIG. 6 shows an example of the generated vibration waveform. FIG. 6A shows a vibration waveform obtained by the apparatus according to the present invention, in which three stacked layers in which ten annular plates are arranged at an interval of 2.4 mm are arranged in three stages, and a 3.3 kg weight is dropped freely by 70 cm. It is the observation data at the time. One scale on the horizontal axis corresponds to 5 msec. For comparison, FIG. 6B shows a vibration waveform obtained by a one-stage type downhole hypocenter (therefore, the number of layers is 30) under the same conditions. The intensity of the vibration generated by the apparatus of the present invention in which the laminated portion composed of ten annular plates is stacked in three stages is higher than the intensity of the vibration obtained by the device of one laminated portion composed of 30 annular plates. 1.
It was about eight times larger, and the vibration generation efficiency was greatly improved.

In the present invention, the elastic member constituting the laminated portion may be a rubber O-ring (circular in cross section) or a rectangular cross section such as a rubber bush. Any material can be used as long as it can be contracted and deformed by the impact and then returned to the original shape. Such a rubber ring is easy to be laminated because its height is constant over the entire circumference. A metal spring material or the like can be used instead of the rubber ring. For example, a wave washer may be used. Wave washer is a mechanical part which is effective for buffering small space because it has an elastic thin-walled annular plate with corrugated shape and receives axial load on the circumference in average.It is widely used as spring for spacer in general. Is what it is. Such commercially available products can be used as they are. Alternatively, a leaf spring or the like may be used. However, when a wave washer is used, in order to maintain a clean lamination state, it is necessary to provide a guide member or the like for position regulation in a plane perpendicular to the lamination direction.

Usually, above such a downhole hypocenter,
A hoisting mechanism equipped with a motor and the like is provided, a wire with an openable / closable hook attached to the lower end is lowered, and a weight dropping mechanism is provided with which the upper end gripping portion of the weight can be grasped and released by the hook. In this case, a coil spring or the like for giving a downward elastic force to the weight may be provided. This causes the weight to fall (free fall or forced fall utilizing the resilience of a spring) to impart a necessary impact force to the impacting body.

Although the preferred embodiment of the present invention has been described in detail, the present invention is not limited to only such a configuration. The number of the laminated portions may be set to two or more.
It is preferable that the number of laminated plate members in one laminated portion is about 10 and that the laminated portion is provided in about 7 steps. The shape of the plate material, the shape of the striking plate and the striking rod, the arrangement position and the number of striking rods, and the like may be appropriately changed. Further, the structure of the connecting portion may be appropriately changed as long as an air reservoir is provided therebetween so as not to hinder the displacement of the lower striking plate.

[0025]

As described above, according to the present invention, a plurality of laminated portions in which a large number of plate members and elastic members are alternately laminated are arranged in a laminating direction via a connecting portion having an air pocket. The striking plate is provided on one end face of each of the striking plates, and the striking plates are connected by striking rods. , The water in the hole existing between the plate members is discharged outward, and a large elastic wave can be generated on the hole wall. The number of laminated sheets in each laminated portion is limited to such a degree that the impact force can be effectively transmitted, and a plurality of such laminated portions can be arranged. Becomes larger. In addition, since air pockets exist between the respective stacked portions so as not to hinder the shrinkage and deformation of the stacked portions, the vibration generation efficiency is significantly improved as a whole.

Due to the above-mentioned effects, the downhole hypocenter according to the present invention can obtain an extremely large vibrating force even with a small bore diameter, and has a high resolution because it contains high frequency components. Therefore, when an elastic wave propagates far and the speed between holes is measured, the distance between holes can be increased, and the ground vibration characteristics over a wide ground can be accurately measured by excavating only a few boring holes. It becomes possible to grasp. Further, since explosives and the like are not used, it is safe and easy to use, and there is no danger of destroying the hole wall. For example, it is an optimal downhole hypocenter for tomography techniques.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration and operation of a wellbore hypocenter according to the present invention.

FIG. 2 is a partial cross-sectional view showing one embodiment of a downhole hypocenter according to the present invention.

FIG. 3 is an exploded perspective view showing a state of lamination of the annular plate and a rubber O-ring.

FIG. 4 is a graph showing the relationship between the number of annular plates and relative amplitude.

FIG. 5 is a graph showing a relationship between the number of stages of a laminated portion and an amplitude ratio.

FIG. 6 is an explanatory diagram showing an example of a vibration waveform caused by a downhole hypocenter.

[Explanation of symbols]

 10a, 10b Laminated part 12a, 12b Ring plate 14 Rubber O-ring 16 Air pocket 18 Connecting part 20, 21, Striking plate 22 Striking rod

Claims (3)

(57) [Claims] 1. A downhole hypocenter having a laminated portion in which a large number of plate members are laminated via an elastic member, and applying a striking force to the laminated portion in a laminating direction to cause vibration.
A plurality of laminated portions are arranged in the laminating direction via a connecting portion having an air pocket, a striking plate is provided on one end surface of each laminated portion, and the striking plates are connected with each other by a striking rod. Multi-stage type downhole hypocenter. 2. Each of the laminated portions includes a metal annular plate and a rubber O
It is a structure in which rings and rings are alternately laminated, and a column vertically penetrates the center of each laminated portion, and the connecting portion is formed of a covered cylindrical member whose inside becomes an air reservoir, and the covered cylindrical member is fixed to the column. 2. The hypocenter in a downhole according to claim 1. 3. Each laminated portion has a structure in which ten metallic annular plates are laminated, and the laminated portions are arranged in seven stages.
The wellhole hypocenter described.