This U.S. patent application claims priority under 35 U.S.C. 119 (a) through (d) from a Russian Federation patent application RU201258380 filed 28 Dec. 2012.
The proposed invention relates to the field of survey geophysics, in particular, to the equipment for multi-component seismic measuring at the sea bottom for prognosis of hydrocarbon deposits and study of the structure of sedimentary layer.
Nowadays the seismic survey with the use of bottom systems, is rapidly developing, which allows for measuring not only longitudinal seismic waves, but also transversal seismic waves.
There is known a bottom seismic system designed by a Russian state scientific-production enterprise <<Sevmorgeo>> (advertisement booklet of “Sevmorgeo”). The system is encapsulated in a spherical hermetic case, containing geophones, a power source, a registration unit, and a control unit of an acoustic circuit breaker of the electrochemical type. The hermetic case ensures positive floatation of the system. For placing the system on the sea bottom, it is fastened with elastic (rubber) braids to a concrete load of a rectangular shape via the circuit breaker. Such design of the bottom system ensures a high technological suitability of the submerging—emerging operations, possibility of work at the depths up to 6000 meters, however, high positioning of transverse shear wave sensors relative to the bottom and elastic fastening of the system to the load reduces the system's sensitivity for the transversal waves.
A bottom system taught in a published patent application US20130028047 (herein also called a ‘prototype bottom system’) is considered a related art closest to the present invention. The prototype bottom system comprises: a cylindrical case with a rounded bottom and a convex lid; the case contains a registration unit with flash-memory, a compass, a power source, and a geophone block; a hydrophone mounted outside the case; a vacuum-port, a condition indicator, and a hermetic connector, covered with an elastic protector. The system structure ensures recharging of feeding elements and re-recording information from the flash-memory to an external data carrier via a hermetic connector without opening the system. The published patent application US20130028047 is hereby entirely incorporated by reference.
Design of the prototype bottom system allows for increasing the productivity of operation, ensures obtaining information through four channels. However, it has a number of disadvantages, diminishing its efficiency. Exemplarily, the rounding shape of cylindrical case reduces the area of contact with the sea bottom that affects accuracy of registration of transversal seismic waves. Further, the prototype structure doesn't ensure minimization and correction of influence of magnetic masses of the bottom system's units on the compass' indications. Another disadvantage of the aforementioned bottom system is absence of an acoustic system for determination of the system's coordinates on the seabed, which necessitates the use of an external acoustic navigation system.
The primary aim of the present invention is the designing of a sea bottom seismic system (it can also be called a ‘bottom station’) being free of the aforementioned disadvantages, i.e. providing for minimum impact of magnetic masses of the system's elements on the compass' output indications (orientation in the Earth's magnetic field), and increasing the sensitivity of the bottom system. Other aims of the invention can be identified by a person skilled in the art upon learning the present disclosure. Without further analysis, the present disclosure will so fully reveal the gist of the invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitutes essential characteristics of the generic or specific aspects of this invention.
In preferred embodiments, the inventive sea bottom seismic system (station) features:
The aforementioned angle-detector, used for measuring of pitch, roll, and magnetic azimuth, is placed coplanar to the plane of the case's bottom (with is also the plane of the geophones), in such a way that the compass' indicating direction essentially coincides with the axis of one pair of the geophones, and the compass' center is located on the vertical axis of the bottom system. The angle-detector is capable of internal calibration for taking into account the influence of magnetic masses of the bottom system's elements.
The aforementioned vacuum sensor is intended for control of the system's water-tightness in the process of its preparation for operation, and during exploitation thereof. The aforementioned external pressure sensor is intended for control of the depth of the bottom system placement on the seabed, and registering of changes of the sea level during operation, especially, in tidal zones.
In preferred embodiments of the present invention, the following units are located on the outer surface of the case: a hydrophone; a vacuum-port; a connector socket serving for the bottom system initialization, data transferring from a flash-memory, and recharging the power supply unit; a LED sensor for control of the functional condition of the bottom system. All of the above enumerated units, except for the hydrophone, are provided with hermetical plugs, placed prior to submerging of the bottom system onto the seabed to prevent water leakage inside the case.
Preferably, the bottom system may include two connector sockets used for separation of data transferring and batteries charging to essentially prevent their interference. The bottom system preferably includes a sensor for functional control thereof; the functional control sensor can be represented by a multi-colored LED, connected via the main digital data processor with the vacuum sensor, the power supply unit, and the registration unit's processor.
All the elements mounted on the outer surface of the case are protected with a protector layer, preferably made of compound material, for example polyurethane or polyethylene, and having radial junction with the upper lid and the bottom of the case.
BRIEF DESCRIPTION OF DRAWINGS OF THE INVENTION
a illustrates a schematic plan view of location of essential units of the bottom system, according to the embodiment of the present invention shown in
b illustrates a schematic side view of location of essential units of the bottom system, according to the embodiment of the present invention shown in
While the invention may be susceptible to embodiment in different forms, there are shown in the drawings, and will be described in detail herein, specific embodiments of the present invention, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.
An exemplary preferred embodiment of the present invention is illustrated in
As shown in
In the preferred embodiment shown in
The following steps are recommended to deploy a number of the bottom stations (systems) for seismic survey (see also U.S. Pat. No. 8,076,941, hereby incorporated by reference):
If the sea depth in the region of operation is greater than a half of distance between two neighbor bottom stations, then at least each tenth bottom station should be equipped with the aforementioned acoustic system having the board 10 and antenna 11 for control of positioning the bottom station on the seabed.
After the setting up the bottom stations on the seabed, the survey of the profile is provided and the bottom stations are then lifted on a vessel's board, wherein the synchronization clock of each bottom station is synchronized, via the connector socket 13, with the pps channel of the GPS system. Data from the flash memory of the registration unit 5 is transmitted to a base station. Based on the indication of the LED sensor 15, the hermetic condition and the extent of discharging the power supply unit are evaluated. Thereafter, the bottom station can be prepared to the next cycle of operation.
The bottom system allows registering different parameters of the seabed strata. The bottom system can operate within the sea depth range from 0 to 500 meters. The specific manner of setting the bottom stations on the seabed is determined based on the sea depth in the region to be surveyed, and on a predetermined distance between two neighbor bottom stations. Where the depth ranges from 20 to 100 meters, the bottom stations can be individually placed on the seabed, while each bottom station should be furnished with its own releasable load and a float for ascending the bottom station after operation. When the predetermined distance between the bottom stations is less than 20 meters, the bottom stations can be set by a chaplet with the help of halyard having a negative floatation.
Number | Date | Country | Kind |
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RU201258380 | Dec 2012 | RU | national |