System for generating pressure waves in an underwater environment

• US 9,733,378 B2
• Filed: 05/14/2010
• Issued: 08/15/2017
• 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: Sandroni, Stefano Carlo Luigi, Calcagni, Davide, Carcaterra, Antonio
• Primary Examiner(s): Ratcliffe, Luke
• Assistant Examiner(s): N'Dure, Amie M
• Application Number:
  US13/322,021
• Publication Number:
  US 20120113756A1
• Time in Patent Office: 2,650 Days
• Field of Search: 367144
• 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, comprising:

one or more autonomous underwater vehicles organized in swarms, the one or more autonomous underwater vehicles are configured to navigate both underwater and on a surface of the water, each of the one or more vehicles including onboard or entraining one or more seismic devices,

wherein the one or more seismic devices each include a cylinder defining an axis, the cylinder including therein a striker piston and a pump piston, each of the striker piston and the pump piston have two opposite sides with respect to the axis, one of the two sides for each piston being an impact side,

wherein the pistons are configured to slide along a direction parallel to said axis and configured to strike against each other in correspondence with the respective impact side of each piston, and

wherein the pump piston is in contact with water of a sea environment on the side opposite to the impact side such that a pressure wave generated by the impact of the striker piston and the pump piston propagates along the cylinder and is released into the sea environment,

wherein the pressure wave generated by the impact of the striker piston and the pump piston is released into the sea environment through at least one diffuser, and

wherein an axis of the at least one diffuser is oriented substantially perpendicular to the axis of the cylinder.

2. The system according to claim 1,

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 devices, and

wherein 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 claim 1 or 2 further comprising:

one or more surface stations for the supply of technical services to the vehicles, capable of being installed on ice and also floating on the surface and being moved on the surface during immersions of the underwater vehicles, said surface stations including 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,

wherein during navigation, the vehicles configured to be mechanically disconnected from the station or 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 claim 1, wherein each vehicles carries onboard or entrains one or more devices.

5. The system according to claim 1, wherein a 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.

6. The system according to claim 1, further comprising a pressure generator of a gas for thrusting the striker piston against the pump piston.

7. The device according to claim 1, further comprising generation means 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.

8. The system according to claim 1, wherein a diffuser is provided on each of a first side of the cylinder and on a second side of the cylinder opposite to the first side.

9. A method for generating pressure waves for deep seismic surveys in a sea environment, actuated by means of the system claimed in claim 1 or 2, wherein the seismic devices are activated according to a predefined scheme in order to increase energy introduced, minimizing resonance effects, reproducing an effect of a conventional air-gun array in terms of amplitude and frequency band of a signal itself.

10. A method for generating pressure waves for deep seismic surveys in a sea environment actuated by means of the device claimed in any one of claims 5, 6 and 7, the method comprising:

thrusting the striker piston against the pump piston, by the pressure action of a gas;

transmitting via the pump piston a pressure wave to the water of the sea environment by means of the side counteropposed to that against which the first piston strikes; and

the striker piston continues its run integrally with the pump piston.

11. The method according to claim 10, 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.