SYSTEM FOR GENERATING PRESSURE WAVES IN AN UNDERWATER ENVIRONMENT

• US 20120113756A1
• Filed: 05/14/2010
• Published: 05/10/2012
• Est. Priority Date: 05/26/2009
• Status: Active Grant

• Current Assignee: Eni SPA (Eni Petroleum Company Incorporated)
• Original Assignee: Eni SPA (Eni Petroleum Company Incorporated)
• Inventors: Carcaterra, Antonio, Calcagni, Davide, Sandroni, Stefano Carlo Luigi
• Granted Patent: US 9,733,378 B2
• Time in Patent Office: Days
• US Class Current: 367/144
• CPC Class Codes: G01V 1/3843 Deployment of seismic devices, e.g. of streamers equipment for marine deployment in general B63B

Abstract

System for generating pressure waves for deep seismic surveys operating in an underwater environment below the surface, suitable for investigating subcrustal objectives for prospecting purposes in the search for hydrocarbons and/or minerals. The system comprises one or more autonomous underwater vehicles organized in swarms, independent and coordinated, each housing one or more autonomous acoustic sea sources with self-propelled striker pistons. This system is served by a system of supporting surface stations, for reprovisioning, recovery actions, checking the well-being of the single vehicles and swarms and maintenance. The system is capable of using both conventional and non-conventional self-charged acoustic sea seismic sources. The system is capable of replicating the effect of a conventional source operated from the surface. The seismic sea source of the non-conventional acoustic type, proposed herein, can release a high-intensity pressure wave produced by a system of two striker pistons, which does not consume air when operating as it does not disperse air or another gas in water and does not produce mass variations of the device during its functioning and allows the amplitude and duration of the sound wave emitted and characteristics of the emission spectrum, to be regulated.

Claims

1. A system for generating pressure waves for deep seismic surveys in an underwater environment consisting of one or more autonomous underwater vehicles organized in swarms, capable of navigating both underwater and on the surface, each containing onboard or entraining one or more seismic sources.

2. The system according to the previous claim, wherein the vehicles are equipped with an automatic navigation system, a data acquisition system onboard and reciprocal exchange means of information relating to positions, velocity, configuration, navigation data and synchronization of the acoustic emissions of the sources, wherein the data flow and control signals are transmitted via cable and/or on an acoustic support and/or on an electromagnetic support.

3. The system according to one of the previous claims comprising one or more surface stations for the supply of technical services to the vehicles, capable of being installed on ice and also of floating on the surface if there is no formation of ice and being moved on the surface itself during the immersions of the underwater vehicles, said surface stations comprising a berthing for the vehicles for the supply of electric energy, gas and technical fluids, for control operations of the state of efficiency of devices and plants onboard the underwater vehicles and a telecommunication system, during the navigation, the vehicles being able to be mechanically disconnected from the station or, if necessary and in particular cases, remain connected to it by means of an umbilical cable suitable for carrying communication cables and/or pipelines for technical fluids.

4. The system according to one of the previous claims, wherein each vehicles carries onboard or entrains one or more sources.

9. The system according to at least one of the claims from 1 to 4 comprising a device according to at least one of the claims from 5 to 8.

10. A method for generating pressure waves for deep seismic surveys in a sea environment, actuated by means of the system claimed in at least one of the claims from 1 to 4 or in claim 9, wherein the seismic sources are activated according to a predefined scheme in order to increase the energy introduced, minimizing the resonance effects, reproducing the effect of a conventional air-gun array in terms of amplitude and frequency band of the signal itself.

5. A device for the generation of pressure waves for deep seismic surveys in a sea environment comprising a cylinder, defining an axis, and in which there are a striker piston and a pump piston, each having two opposite sides with respect to said axis of which one is called an impact side, the pistons sliding along a direction parallel to said axis and being suitable for striking against each other in correspondence with said reciprocal impact sides, wherein the pump piston is in contact with the water of the sea environment on the side opposite to the impact side.

6. The device according to claim 5, wherein the run length of the striker piston before impact with the pump piston can be regulated in order to modify the acoustic emission characteristics of the same device.

7. The device according to claim 5, wherein pressure generation means of a gas are envisaged, suitable for thrusting the striker piston against the pump piston.

8. The device according to claim 5, wherein generation means are envisaged, of Lorentz electromagnetic forces for thrusting the striker piston towards the pump piston through magnetic fields generated by electric circuits integral with the cylinder and electric circuits integral with the pistons.

11. A method for generating pressure waves for deep seismic surveys in a sea environment actuated by means of the device claimed in at least one of the claims from 5 to 8, comprising the following steps:

a) the striker piston is thrust against the pump piston, by the pressure action of a gas

b) the pump piston transmits a pressure wave to the water of the sea environment by means of the side counteropposed to that against which the first piston strikes

c) the striker piston continues its run integrally with the pump piston

12. The method according to the previous claim, wherein, after undergoing expansion following the run of the pistons, the gas is recompressed

a) by means of the pressure energy accumulated in an accumulator tank containing a gas and a liquid, and wherein the energy is supplied by means of a system of pumps which inject liquid compressing the gas contained therein;

b) by means of a retrograde movement of the two striker and pump pistons, which takes place along the cylinder in the opposite direction with respect to that relating to the expansion phase of the gas of the launch tank, the movement of the pump piston being generated by the pressure action of the liquid contained in the accumulator tank, in which the pressure is maintained at higher values with respect to that in force in the launch tank by means of the action of the pumps.