MXPA06008235A - System for seismic exploration of a submerged subsurface including implanted bases - Google Patents

Abstract

A system for seismic exploration of a submerged sub-surface comprises a plurality of bases (4) located at predetermined seabed positions, each base comprising an elongate stem penetrating the seabed, at least a seismic sensor (10, 12) within said stem, a radially extending support zone (19) connected to the upper end of the stem, said upper end projecting from the seabed, and a respective plurality of modules (6) each incorporating a data storage unit and a power source, each module being mechanically and electrically connected to the upper end of said stem, said module being capable of being connected to, and disconnected from, the base by an underwater vehicle.

Description

FR, GB, GR. HU, IE, IS, IT, LT, LU, MC, NL, PL, PT, RO, (88) Date of publication of the international search report: SE, SI, SK, TR), OAPI (BF, BJ, CF , CG, Cl, CM, GA, GN, 27 October 2005 GQ, GW, ML, MR, NE, SN, TD, TG). Declaration under Rule 4.17: - of invention (Rule 4.17 (iv)) for US only FOT lwo-leller codes and other abbrevialions, refer to the "Guid¬ PubUshed: ance Notes on Codes'and Abbrevialions "appearing at the begin SYSTEM FOR THE SEISMIC EXPLORATION OF A SUBMERGED SUBTERRANEAN INCLUDING IMPLANTED BASES DESCRIPTIVE MEMORY The invention relates to the seismic exploration of a submerged subway. A system for scanning a submerged subway of EP-1 217 390 is known. In said document, in the embodiment as in Figure 5, the system consists of antennas, each of which is formed on one side of a base that incorporates a geophone, and on the other of a module that incorporates means for data storage. Each antenna is released where the module is initially fixed to the base, of a ship for example, in order to be anchored in a submerged bed. This document explains that during a seismic exploration study that implements the emission of an acoustic wave, the signals transmitted in the subway to the antenna are collected by the base, and transmitted to the module which stores them in memory. The document also explains that once the module in this form has collected the data received from the base, it separates itself from said base and returns the surface of the water with the help of an inflatable buoy, where it is supposedly recovered in order to assemble the data. The proposition described in that document is full of major uncertainties, especially with regard to the position of the seabed currently reached by an antenna and the anchoring of the antenna to the seabed. In addition, the module can only be used once and it would be necessary, before each exploration study, to install a new series of antennas, making the implementation too expensive. The same document provides in Figure 6 that the antenna includes several memory cartridges which are supposed to be successively loaded with the seismic data, each associated with the buoy. The cartridges are supposed to be released individually for the recovery of the surface. However, this document fails to describe a source of energy capable of supplying the energy required for the operation of the antenna for a long period. The invention relates in particular, but not exclusively, to the monitoring of oil fields during their operation. The need of oil companies in this issue has been recognized but it is necessary to reduce costs for these purposes and also provide systems that make possible the conditions for measurement that are sufficiently stable and precise. An objective of the invention, therefore, is to allow the monitoring of a submerged subway for a very long period at a reduced cost and with good reliability in terms of measurements. With this in mind, the invention provides a seismic exploration system for a submerged subway that includes: a number of bases, each incorporating at least one sensor; and - a module associated with each base and incorporating the means for storing data, the system incorporates facilities that can be dismantled again to adjust the module on the basis. In this way the module can be adjusted on or dismantled from the base as required. In particular, whenever a study is organized to acquire data, the module can be adjusted on the basis, the study can be carried out and then the module can be removed from the database. There may therefore be very long periods separating studies of successive data acquisition on the same seabed all at a reduced cost. further, since the base can remain in the same place, the stability for the measurement conditions is preserved. The system according to the invention also has at least any of the following characteristics: the module is adjusted on the base by means of a sliding movement followed by a rotation about an axis parallel to the direction of the sliding movement, facilities to attract the module to the base and facilitate the realization of adjusting the module on the base, - includes submerged facilities for the storage of one or more modules dismantled from their bases, - the base includes a rod of the support area that is extends radially in projection from the rod in order to prevent the portion of the base located above the support zone from penetrating the ground, - the support zone has a smooth bottom face, - the support zone has orifices that they extend in a direction that is not perpendicular to the longitudinal direction of the rod, - the support zone has an upper face extending to a lower face of the support area, - the base presents a housing for the module and the installations for sealing the housing when the module is absent, - the base includes an anchoring element for a vehicle, - this includes facilities for carrying out the dismantling of the module on the basis and facilities for transporting the module away from the base, - the module has a density approximately equal to one, - the module includes a source of electrical energy, - the module includes a clock , - the module includes means for transmitting and / or receiving an acoustic signal, - the base includes at least one geophone, - the base includes an acoustic decoupler between the geophone and a suitable base zone to receive the module, - the base includes a hydrophone, - the base includes a digitizer, - the base has a height on the scale of between 1 and 40 meters, - the complementary facilities are suitable for to make an electrical connection through the contact between the base and the module, - the complementary installations are suitable to place the module on the base in order to establish a magnetic link of the parts of the base and the module without contacting the parts of one with the other, - these include several bases connected between themselves through a cable, and - they include several bases without a cable link between them. A suitable basis for being part of a system according to the invention is also provided according to the invention. Also provided according to the invention is a module suitable to be part of a system according to the invention. Finally, according to the invention, a seismic exploration procedure of a submerged subway is provided, in which at least one module includes the data storage medium fixed to a fixed base to a submerged bed and incorporating at least one sensor. The method according to the invention can also have at least any of the following characteristics: - including the previous stage consisting of fixing the base to the bed, - the base fixes the bed through the release of the base in a fall free to the bed, - the base is fixed in such a way that the area of the base suitable for receiving the module extends in projection from the bed, -in a manner concomitant with the fixing stage, a module of operation, - where the provision is made for a previous stage that consists of carrying out a seismic exploration of the subway by means of the base and the module, - the exploration is carried out by means of several bases without a cable link among them, - includes the last stage consisting of removing the module from the base and taking the module away from the base, and - several suitable bases to receive the respective modules are connected through at least a cable. Also provided in accordance with one aspect of the invention is a system for seismic exploration of a submerged subway that includes: a plurality of bases located at predetermined positions of the seabed, each base comprising an elongate rod penetrating into a seabed, at least one seismic sensor within each rod, a support zone extending radially connected to the upper end of the rod, said upper end projecting from the seabed, and a respective plurality of modules each incorporating the data storage unit and the power source, each module being mechanically and electrically connected to the upper end of said rod, said module being able to be connected to, and disconnected from, the base to through an underwater vehicle. According to another aspect of the invention, there is provided a method for seismic exploration of a submerged subway, comprising the steps of descending near a predetermined position of the seabed a base having an elongated rod and at least one seismic sensor inside. of the rod, a support zone that extends radially while being connected to the upper end of the rod, the anchor of the rod to the seabed while maintaining its upper end projecting from the seabed, connecting a module that includes the means for storing data in the source of energy for the upper end of the rod by means of an underwater vehicle, repeating the previous steps for each seabed position where the seismic data must be acquired, and disconnecting said modules from the respective bases after the completion of the seismic acquisition by means of an underwater vehicle. Other features and advantages of the invention will also appear in the following description of a preferred embodiment given in the form of a non-limiting example and with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of the components of an antenna according to one embodiment of the invention, namely a base and a module; - Figure 2 is another perspective view showing the upper part of the base together with the module of the antenna of Figure 1; - Figures 3 and 4 are two perspective views showing the upper part of the base and the module received there; - Figure 5 is a cross-sectional perspective view of the seabed showing the antenna of Figure 1 and an underwater vehicle; - Figure 6 is a global view showing a network of antennas as in Figure 1, installed on the seabed; - Figure 7 illustrates one of the antennas similar to that of Figure 6 in a modified embodiment; - Figure 8 is a larger scale view of a part of the network as in Figure 7; - Figure 9 is a perspective view of a storage medium for the system of Figure 1; - Figure 10 is a perspective view of an element for the installation of the modules of the system of Figure 1; - Figures 11 and 12 are two side views of two embodiments of a vehicle incorporating the element as in Figure 10; - Figures 13 and 14 illustrate two steps of installing a module on a base in the system of Figure 1; - Figure 15 is a diagram of the electrical connections during the step of Figure 14, - Figure 16 is a partial cross-sectional view of the upper end of a base according to a variant mode, - Figure 17 shows another variant embodiment of base. A system for seismic exploration of a submerged subway according to a preferred embodiment of the invention is illustrated in Figures 1 to 6 and 9 to 15. The system includes a series of antennas 2 each made of a base 4 and a module 6. The base 4 has a clear example of an essentially extended form of a pole or rod. It has geometrically on the largest part of its length a cylindrical shape with a circular cross section. The height of the base can be in a scale of between 1 and 40 meters according to the nature of the seabed where it is intended to be installed. The base has a lower end 8 in the shape of a sharp pointed end to facilitate penetration of the base for the purposes of anchoring it to the seabed. In a lower part of the base near the pointed end 8 the base includes a group 10 of three geophones oriented in three orthogonal directions, a hydrophone 12 together with a digitizer 14 which ensures analogous-digital conversion. Above these elements the base includes an acoustic decoupling 16. The base 4 has at its upper end a cylindrical housing 18 that opens towards the upper part and has a flashing upper part. The area 19 of the upper end of this housing has a sharp shape, the cross section of which flashes in a direction opposite to that of the pointed end 8. The base 4 includes, projecting from the circumference of this end, a circular bar 20 that extends over more than three quarters of a circle. The module 6 is generally cylindrical in shape but with little height. It is small enough to be received almost completely inside the housing 18 of the upper end of the base 4. The module 6 has an extended clamping handle 22 projecting radially from the external surface of the module parallel to the axis of the cylinder forming the module . This handle is designed to penetrate a complementary rectilinear groove 24 formed in the wall of the housing 18 and open at its upper end to receive the handle. The module 6 has a density of approximately equal to 1. It includes a battery 25 that supplies the module and the base with electrical energy and ensures autonomy for a period of between 8 and 30 days. The module 6 includes the clock 27 ensuring a lower displacement than the determined threshold. It includes a memory 29 of an appropriate capacity for the recording of seismic data. It includes a hard disk and means for the acoustic transmission of the compressed data. It also includes means 31 that allow adjustment through remote communication to synchronize the watch with a watch of an external element such as a vessel located on the surface of the water. Each antenna 4 includes means for connecting the module 6 on the base 4, whose means are capable of being eventually disconnected. These means are designed to allow the module 6 to be brought on the base 4 when the previous one is anchored to the seabed 32 and secured there. They also allow module 6 to disconnect from base 4 in the same conditions and move away from base 4 for recovery purposes. The system according to the invention includes means for bringing the module to the base 4 and vice versa to transport the module away from this base. It also includes means to connect the module on the base and to disconnect the module from the base. The means of transport and the means of connection / disconnection can be constituted by a vehicle of the ROV (remotely operated vehicle) type or the AUV type (autonomous underwater vehicle). Said vehicle 30 has been illustrated by way of example in Figure 5. It is of the type known per se and includes, in particular, means for holding and manipulating the module 6. It can be moved between the various bases 4 of the system and a present vessel Over the surface. A provision can be made, for example, for the connection of the module 6 on the base 4 that is carried out by means of two successive movements: first, as shown in Figure 3, a sliding movement of the module along the direction axial longitudinal axis 40 of the base to cause it to penetrate inside the housing 18; - then a rotation of the module relative to the base about the axis 40 in order to block it in position. In this case suitable passages are provided on the basis for the trajectory of the handle 22. These actions can be achieved for example, by means of a specific tool 44 which also serves as a beacon changer, in the form of a system of small barrel type, as shown in Figure 10. This tool in this way is capable of carrying 10 headlights 4. Said tool can be of the SKID type known per se and adjusted on vehicle 30 as shown in Figure 11. If a Standard connection for connecting the tool 44 to the vehicle 30, it is possible to use the same tool on several vehicles. Alternatively the tool 44 can be part of the vehicle 30 as illustrated in Figure 12. The tool can then be located under the vehicle and no longer on the front thereof as shown in Figure 11. This solution reduces the overall space occupied by the tool . The means for connecting the module 6 on the base 4 here are configured to establish an electrical connection through the contact between the base and the module once the previous one has been received inside the housing 18. Figure 15 shows the various classes of connections that are going to be established. The module 6 installed on the base 4 contains batteries to electrically supply it to the sensors, and to the hard disk. The data is received by the modules through the analog-digital converter of the base 4. During connection on the base, a connector 45 of the type suitable for operation in a submerged medium (called a "wet connector") connects the controller 46 of the vehicle 30 with the module 6. Another connector 48 of the same type connects the module 6 with the base 4. Auxiliary functions such as switching to standby, reactivation, and self-test are desired. It is desirable to be able to activate these functions at any time during the operation, for example by means of an acoustic signal, and for this purpose a provision is made in the appropriate form for an acoustic modem installed on the modules 6. The self-test is possible to ensure that the modules are operating correctly. A provision can be made to enable this test to be carried out at any time, and this is possible as long as a connection to the surface or to the vehicle can be established. An intermediate solution consists of completing the self-test during the installation of the module, or in relation to said installation through a link with the vehicle: when the mechanical and electrical connections from module 6 to base 4 have been achieved, the module performs a second connection 50 with the vehicle. If this connection creates problems, a message can be sent to the surface and the headlight could change. In this way, Figure 13 shows the installation of the module and Figure 14 shows the previous self-test phase. In a modified embodiment, the module is electrically connected to the base by means of a magnetic link (inductive coupling) without contact between the parts of the face of the module and the base, once the module 6 has been received at the base 4. The method according to the invention is implemented, for example, in the following manner. In a first stage, a series of bases 4 is anchored to a submerged bed 32, for example a seabed, which extends above the subway for which seismic exploration is desired. The bases are for example configured as a network that can have the shape of a grid pattern as shown in Figure 6. It is possible for example for bases 4 to be established on the submerged bed through the provision between the neighboring bases of a distance that can be between 150 and 300 meters. With reference to Figure 5, each base 4 is pushed into the seabed over the widest part of its height. However, care is taken that the upper end of the base 4 corresponds to the housing 18 which extends as a projection from the bed in order to be easily accessible.

This installation can be carried out through various techniques, such as drilling. In this clear example, preference is given to the technique of placement through free fall. To achieve this, each base 4 is weighted and placed at a defined height above the bed. Once the base is released at this height it is allowed to descend in free fall to the seabed and then partially submerged inside this bed. In order to prevent the system from going too far, a collar is suitably provided near the upper end of the base in order to limit its penetration into the ground so that the desired level is not exceeded. This is the purpose of the embodiment illustrated in Figure 16. The base has a wall 52 shown in a partial cross-section forming a support zone on the ocean floor. The wall 52 has a smooth bottom face 53 perpendicular to the axis 40 of the stem of the base. The wall 52 surrounds the housing 18 to receive the module 6. The wall has an upper face 56 that flashes from an upper end of the base 4 in the direction of the lower face 53. This shape provides an acoustic signal that facilitates the identification of the base through a sonar, such as the sonar of an underwater vehicle 30. The base has, at its upper end, an element 60 such as a ring by anchoring the vehicle 30 to the base during certain operations such as the connection or disconnection of a module. The base 4 has here an element of the flexible seal such as a flap 62 which allows the housing 54 to be sealed whenever the module is absent, in order to prevent its space from being occupied by foreign bodies, particularly organisms that could develop there. It also protects the interior of the corrosion housing, in order to allow the base to anchor to the seabed through free fall, the wall 52 has openings (not shown) extending in a direction not perpendicular to the axis 40 and for example, parallel has said axis. Figure 17 represents a modified embodiment of the base 4 wherein the interior of the base is in a pressure equilibrium with the exterior. This is obtained by means of openings 70 configured in the external wall 71 of the base, which allow water to fill the interior of the base during its descent. The sensors are placed inside a waterproof envelope 72 connected the wall of the base through the decoupling element 73. The openings 74 are configured about the upper part 75 of the base where the headlight is received, in such a way that, when the headlight penetrates the part 75, it expels the water there, as indicated by the arrow and in this way expels the deposits that have been able to be built there. Figure 17 shows the depressed base within the seabed, the level of the bed being represented by line 76. A corolla corresponding to the corolla 19 of figure 1 is shown in diagrammatic form at 77. A conductor 78 connects the sensors with the non-contact coupling device 79 provided on the inner wall of the upper part 75. As illustrated in Figure 6, the bases 4 are independent of one another and are not connected through the cables 34, the study of scanning being carried out without a cable link between the bases 4. By means of the vehicle 30, then a respective module 6 is brought to each base 4 which is installed in the housing 18 in order to ensure a mechanical and operational connection among them. Each base pair / module constitutes a scanning antenna. Once the antennas are assembled in this way, a seismic exploration study of the subway is carried out. To do this, in a manner known per se, an acoustic wave is emitted, for example, from a vessel on the surface. The acoustic wave is reflected in the underground far as the bases 4, and is detected through the geophones 10 in these bases. A fraction of the signal transmitted in the water is also detected through the hydrophone 12 of the base. The data received through these sensors is transmitted to module 6 and stored in memory 29. Finally, by means of vehicle 30, modules 6 are collected. To achieve this, the vehicle 30 successively disconnects each module 6 from the corresponding housing 18 and takes them, for example upwards to the aforementioned vessel for the exploitation of the data. Preferably the module 6 has a small size to minimize the cost of this transportation through the vehicles. This module 6 is suitably provided with location means to facilitate its remote identification through the vehicle. As a variant, the bases 4 could be installed in the bed 32 with the modules 6 already received in the housing 18. The modules are only removed after the completion of the first scanning study. In a variant embodiment illustrated in FIGS. 7 and 8, the bases are connected by means of one or more cables. These cables make it possible to connect the bases in mini-networks with a central node. In this way, the antenna of the same group is connected through the cable to a station on the seabed 35, including, for example, a unit for storing the data and / or energy. In order to reduce the volume of the modules that are to be transported through the vehicle or the total length of the trip that the vehicle has to make, a provision could be made to configure the subway with a storage element 60 for the modules and / or the batteries 62 as illustrated in Figure 9. This element will be located, for example, in an area close to the installation of the antenna, for example, 30 meters from the field. The invention allows the monitoring of a submerged bed for long periods at a relatively low cost. In addition, the bases 4 remain anchored in the bed between the various successive exploration studies during which they receive the module 6. The seismic data are therefore always collected in the same positions, which ensures the consistency in the measurement conditions, with respect to the positions of the bases 4 as well as their attachment to the submerged bed. The invention offers the measurement conditions sufficiently constant to allow the detection of subtle changes of the subway, for example in petroleum deposits, such as changes relative to pressure, saturation, permeability barriers, or superpermeability zones. The invention allows to reuse the same modules 6 during successive exploration studies. In addition, a defective module 6 can be replaced at less cost. The invention makes it possible in particular to carry out a scanning study by means of a single vessel located on the surface for collecting the data recorded by the modules 6. The invention makes it possible to use bases 4 and modules 6 that have no connection by cable, whether temporary or permanent, with the surface. Of course, many modifications can be made to the invention without thereby departing from the scope thereof. Furthermore, according to one embodiment of the invention, there is provided a system for the seismic exploration of a submerged subway that includes: a plurality of bases located at predetermined positions of the seabed, each base comprising an elongated rod penetrating the seabed, at least one seismic sensor inside said rod, a supporting zone extending radially connected to the upper end of the rod, said upper end projecting from the seabed, of a respective plurality of modules each incorporating a data storage unit and a source of energy, each module being mechanically and electrically connected to the upper end of said rod, said module being able to be connected to, and disconnected from, the base through an underwater vehicle. The base may include an anchor element for an underwater vehicle. The module can be adjusted on the base by means of a sliding movement, then through of a rotation about an axis parallel to the direction of the sliding movement. The support zone may have holes extending in a direction not perpendicular to a longitudinal direction of the rod. The upper end of the base may comprise a housing for receiving the module. The system was to understand means to seal the housing in the absence of a module. The support area can present an acoustic signal that enables the identification of the same, by means of a sonar carried by the underwater vehicle. The module may have a density of approximately equal to l The module may include a clock. The module may include means for transmitting and / or receiving an acoustic signal. The stem of the base can have a height on the scale between 1 and 40 meters. The module can be connected to the base through a non-contact coupling. The module can be coupled to the base through a magnetic link. The system may comprise additional bases connected to at least one of said bases through a cable. Also provided in accordance with one embodiment is a seismic exploration method of a submerged subway, comprising the steps of descending near a predetermined position of the seabed a base having an elongated rod and at least one seismic sensor within the rod, a radially extending support zone being connected to the upper end of the rod, anchoring the rod to the seabed keeping its upper end projecting from the seabed, connecting a module that includes data storage means and a power source for the end top of the rod by means of an underwater vehicle, repeat the previous steps for each position of the seabed where the seismic data must be acquired, and disconnect those modules from the respective bases after the completion of the seismic acquisition by means of a vehicle underwater The base can be anchored to the seabed by free fall to the seabed. The base can be anchored to the seabed through the conduction of said rod into the seabed.

Claims (17)

NOVELTY OF THE INVENTION CLAIMS

1. System for the seismic exploration of a submerged subway that includes: a plurality of bases located in predetermined seabed positions, each base comprises an elongated rod that penetrates the seabed, at least one seismic sensor inside said rod, an area of radially extending support connected to the upper end of the rod, said upper end projects from the seabed, and a respective plurality of modules each incorporating a data storage unit and a power source, each module is mechanically and electrically connected at the upper end of said rod, said module is capable of being connected to, and disconnected from, the base by means of an underwater vehicle.

2. The system according to claim 1, further characterized in that the base includes an anchoring element for an underwater vehicle.

3. The system according to claim 2, further characterized in that the module is adjusted on the base by means of a sliding movement, then through the rotation about an axis parallel to the direction of the sliding movement. The system according to claim 3, further characterized in that the support zone has holes extending in a direction not perpendicular to a longitudinal direction of the rod. The system according to any of the preceding claims, further characterized in that the upper end of the base comprises a housing for receiving the module. The system according to claim 5, further characterized in that it comprises means for sealing the housing in the absence of a module. The system according to any of the preceding claims, further characterized in that the support area has an acoustic signal that enables the identification thereof by means of a sonar carried by an underwater vehicle. The system according to any of the preceding claims, further characterized in that the module has a density of approximately equal to 1. 9. The system according to any of the preceding claims, further characterized in that the module includes a clock. The system according to any of the preceding claims, further characterized in that the module includes means for transmitting and / or receiving an acoustic signal. 11. The system according to any of the preceding claims, further characterized in that the stem of the base has a scale height of between 1 and 40 meters. The system according to any of the preceding claims, further characterized in that the module is connected to the base through a non-contact coupling. The system according to claim 12, further characterized in that the module is coupled to the base through a magnetic link. The system according to any of the preceding claims, further characterized in that it comprises additional bases connected to at least one of said bases through a cable. 15. A method of seismic exploration of a submerged subway, comprising the steps of descending near a predetermined position of the seabed, a base having an elongate rod and at least one seismic sensor within the rod, a support zone that It extends radially connected to the upper end of the rod, the anchor of the rod to the seabed while keeping its upper end projecting from the seabed, connect module that includes data storage means and a power source for the upper end of the rod by of an underwater vehicle, repeat the previous steps for each position of the seabed where the seismic data must be acquired, and disconnecting said modules from the respective bases after the completion of the seismic acquisition by means of an underwater vehicle. 16. The method according to claim 15, further characterized in that the base is anchored to the seabed through free fall to the seabed. 17. The method according to claim 15, further characterized in that the base is anchored to the seabed through the conduction of said rod into the seabed.