Acoustics – Geophysical or subsurface exploration – Seismic wave generation
Patent
1981-02-23
1983-06-21
Buczinski, S. C.
Acoustics
Geophysical or subsurface exploration
Seismic wave generation
91 39, 91216B, 91266, 92 131, 92 136, 181114, 181120, 367189, G01V 114
Patent
active
043889816
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to seimsic energy vibrators and, more particularly, but not by way of limitation, it relates to an improved vibration apparatus having selectively controllable drive cylinder volume for frequency range adaptability.
2. Description of the Prior Art
Prior art in point is U.S. Pat. No. 4,106,586 in the name of Stafford, property of the present assignee, which teaches a hydraulic siesmic vibrator wherein the reaction mass includes an axial drive cylinder that is variable between two positions, a maximum and a minimum cylinder volume. On the order of the present invention, the Stafford vibrator utilizes movable end sleeves disposed in opposite ends of the hydraulic cylinder and these, in turn, are hydraulically controllable between two positions, simultaneously, relative to the height of the cylinder. The present invention is directed to a continuously variable cylinder volume control and the capability of achieving optimum fluid compressibility factor throughout a selected frequency range of operation, and this is particularly desirable at higher seismic frequencies on the order of 250 Hertz and up.
SUMMARY OF THE INVENTION
The present invention contemplates a hydraulic seismic vibrator having a reaction mass driven on a double rod-end piston that is frame supported to couple selected frequency vibrational energy through a suitable baseplate for propagation of seismic energy within an earth medium. The double-rod-end piston is reciprocally disposed within an internal drive cylinder within the reaction mass, and hydraulic servo control provides controlled frequency alternating fluid under pressure to drive the reaction mass. Slidable end sleeves are disposed in opposite ends of the internal cylinder and hydraulically controllable either manually or in response to sweep control input for variation of their relative positions thereby to change the internal maximum length of the drive cylinder.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an idealized view in elevation, with parts in section, of a hydraulic vibrator constructed in accordance with the present invention, a control system being shown in block diagram; and
FIG. 2 is an idealized view in elevation, with parts shown in section of an alternative form of seismic vibrator and cylinder volume control.
DETAILED DESCRIPTION
FIG. 1 illustrates a compressional wave seismic vibrator 10 placed in energy coupling engagement by a baseplate 12 for propagation of energy into an earth medium 14. The vibrator 10 is controlled as to range and sweep frequency by a hydraulic drive control system 18. While not specifically shown, the basic sweep control signal generator for the vibrator system is well-known in the art, and in this case it provides input of sweep control signal 20 for the cylinder length control as well as the control signal input to hydraulic drive control system 16.
Referring to vibrator 10, a circular top plate 22 is rigidly secured at a center recess 24 to an upper end 26 of a double-rod-end piston 28. In normal practice, top plate 22 is secured to piston rod 26 by concentric bolting. In like manner, a circular lower plate 30 is bolt-secured at central recess 32 to receive a lower end 34 of double-rod-end piston 28. A cylindrical side wall 36 is then secured as by welding to enclose a reaction mass 38, the entire housing structure providing a rigid connection between upper and lower rod ends 26 and 34, respectively, to a selected baseplate 12 that provides energy coupling function in contact with earth surface 14.
The central axis of reaction mass 38 is then formed with a central bore 40 through which the double-rod-end piston 28 is received in sealed, reciprocable relationship. The bore 40 includes a larger diameter central portion forming a drive cylinder 42, an enlarged diameter upper cylinder 44, and another enlarged diameter lower cylinder 46. Thus, upper and lower cylinders 44 and 46 are characterized by upward and downward facing shoulder
REFERENCES:
patent: 356538 (1887-01-01), Hubner
patent: 3159233 (1964-12-01), Clynch et al.
patent: 3168853 (1965-02-01), Prince
patent: 3369459 (1968-02-01), Fisher
patent: 3482646 (1969-12-01), Brown et al.
patent: 4106586 (1978-08-01), Stafford
patent: 4147228 (1979-04-01), Bouyoucous
Buczinski S. C.
Conoco Inc.
Miller William J.
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