Abstract: The mobile seismic system according to the invention is made up by interconnecting reception sections (T1) and of anchoring sections (T2), and possibly emission sections, the assembly being suspended in the well by means of an electro-carrying cable (3). The first sections (T1), which are filled with liquid, are delimited at least partly by a wall transparent to acoustic waves. They contain each one or several hydrophones and an electronic module of acquisition of the signals picked up. The second sections (T2) comprise a body provided with retractable anchoring means (13) and with motor means, either autonomous, or connected, by a hydraulic line running along the reception system, to common motor means located preferably in a lower section so as to be used as a ballast weight. The reception system may be continuous or made up of several parts connected to each other by electric or electro-hydraulic linking means. The system is suitable for seismic prospecting in wells for example.

Abstract: The invention centralizes data acquired through active or passive monitoring equipments installed permanently in contact with a geologic formation and notably in wells, under the control of one or several permanent stations (PCL) comprising microcomputers. The signals collected by these stations including spontaneous or induced seismic signals, parameters measured by condition sensors, etc., are converted and transferred onto a communication network managed by a server. The signals are translated into a common format more easily accessible for a seismic laboratory taking part in the processing of the data collected by the various monitoring equipments.

Abstract: Monitoring of an underground effluent deposit (2) and the exploration thereof are performed by installing various devices or user modules : reception arrays (Ri, Rj, Rk) such as geophones or hydrophones, condition sensors (C1, C2) , tools requiring electric power supply, etc, in various locations along one or several wells (1) drilled down into a formation, behind well casings or in the annular space between these casings and tubings, and by connecting these devices to a surface station (4), by means of a particularly simple and reliable multi-channel transmission unit. The surface station adapts the commands thereof according to the device to be controlled in return, of receiving all the signals they transmit whether analog or digital and coded, and adapts to several modes of allocation of the transmission channels. With such a system, long-duration monitoring operations may be carried out on a large scale under satisfactory economic conditions.

Abstract: A process for optimizing the transmission rates of digitized signals on transmission lines in multifunction cables, such as logging cables linking well tools to surface installations. The process includes digitising of the data to be transmitted and coding thereof through voltages selected from a set of multilevel coding voltages (2 to 32 for example), and widening towards high frequencies of the passband of each transmission line used, by combination with correcting circuits selected so that the transfer function of the corrected line is substantially that of a filter of the Bessel type, at least in a given frequency range on either side of a 3-dB cut-off frequency fc which depends on the number of coding voltages and on the amplification parameters. Using this process makes it possible to exceed very easily a total flow rate higher than one Mbits/s without increasing the transmission error rate.

Abstract: In a multisource array of seismic sources, each source is associated with one or more sensors (Ci) for picking up the impulses (TB or signature) emitted by the associated source when triggered. The apparatus essentially includes one or more acquisition arrays (Ai), each one associated with a storage unit (Mi) for all the signals emitted by the pickups (Ci) under the control of a computer (10). Each memory unit includes a comparison module (19, 21, 22) for comparing the digitized samples with a threshold value. The number of each one of the channels where a threshold overrun has occurred is recorded in a reference register (24) which is systematically read by the computer. This monitoring of the level of the picked up signals is carried out outside the normal period where the sources are triggered.

Abstract: Each source of an array of seismic signal sources is associated with one or several sensors (Ci) which pick up the impulses the associated source emits at the time of triggering. The device essentially includes an apparatus (6) for the acquisition and the storage of all the signals emitted by the sensors (Ci) and a shooting control apparatus (7), having memories for reference data, for triggering the seismic sources according to these reference data. A computer (10) is programmed to determine the reference data used for the triggering, preferable according to the signals from the sensors (Ci) acquired during the previous emission cycles and validated in order to check whether their form and/or arrival times are within fixed limits. This arrangement makes it possible to take into account the real working conditions of the emission array. The invention can be utilized in marine seismic prospecting.

Abstract: A system is provided for acquiring and recording signals delivered by a set of sensors disposed in one or more probes lowered into a well at the end of a multi-function cable.The different signals to be transmitted are multiplexed before being applied to an acquisition chain adapted for amplifying them, digitizing them and coding them before applying them to a transmission channel in the form of blocks of digitized words. The multiplexing means may comprise several multiplexing units. The sampling frequency of each signal and the formation of the blocks of words are adapted to the number of units effectively used. In the surface installation, the blocks of words are dissociated and stored in a memory in a single mode suitable for all the blocks whatever their formation.

Abstract: A device is provided for acquiring data coming from sensors distributed in several probes which may be anchored in a well or borehole and transmission thereof to a central control and recording system, including a remote control assembly for checking operating parameters. An acquisition apparatus includes a main multiplexer for seismic channels and an auxiliary multiplexer. The control assembly includes different modules delivering signals indicative of the position of the anchorage arms, of the operating temperature, of the power supply voltage, etc, means for testing the sensors and the seismic channels, and means for detecting any malfunction in the advance of the probes along the borehole. Different lines connected to the auxiliary multiplexer transmit the signals delivered by the control assembly.

Abstract: A system is provided for transmitting signals between a sensor assembly contained in one or more well probes lowered into a well at the end of a cable and a surface control and recording unit. The cable includes a central line surrounded by several other lines and an external metal sheath. The transfer of data from the reception assembly to the surface installation is provided by applying suitably coded signals between the central conductor and the external sheath. A considerable increase in the transmission flow rate of the cable is obtained.

Abstract: System for interconnecting elements of a receiving device of great length, for example a seismic streamer, comprising a plurality of data aquisition apparatuses, each of which is adapted to collect 12 separate signals generated by receiver groups distributed in the different elements.The 12 groups of separate receivers (R.sub.1, R.sub.2 . . . R.sub.12) are regularly distributed in each element (T.sub.1, T.sub.2 . . . ), forming 6 pairs of groups. A first group of each pair (R.sub.1, R.sub.3, R.sub.5) is connected to an input of an acquisition apparatus (B.sub.2). The second group of each pair is connected either to an input of another acquistion apparatus, or to inactive electric connection means (B.sub.1, B.sub.3) adapted to connect in parallel the second and the first groups of each pair.This system can be used in seismic prospecting.

Abstract: A device is provided, associated with a computer, for controlling data transfers between a data acquisition device and a recorder-reader. The device comprises logic gates for the selective connection of said acquisition device with said recorder and an intermediary memory of sufficient capacity for at least one series of signals issued from the computer. The device is adapted to supply said signals to the control inputs of said logic gates.

Abstract: A device for determining the position in the water of an elongate element (a seismic streamer for example) towed while submerged, by means of measuring elements such as compasses and pressure gauges spaced apart along said elongate element. Said compasses and pressure gauges are disposed inside profiled bodies firmly secured to sleeves fixed about said elongate element and transmit the measurements, by means of a hertzian wave transmission assembly, to a sensor inside the elongate element, which is connected by a transmission cable to a reception assembly connected to a central unit installed in the towing ship.

Abstract: A device for supplying electric power to electronic apparatuses of a seismic streamer of great length, comprises an electric feeding assembly associated with each electronic apparatus and including three voltage transformers whose primary windings are respectively fed from a generator with a different phase of a three-phase current, and whose secondary windings are respectively connected to three rectifier bridges supplying the required DC voltage to the electronic apparatus.

Abstract: A device is provided for interconnecting a series of data acquisition apparatuses. Each of the apparatuses collect signals and transmit them to a remote central receiving and recording system. In order to sequentially transmit the signals thereto on reception of an order from said central system, the apparatuses are subdivided into a plurality of groups having the same number m of apparatuses. The groups comprise cable sections of substantially equal length interconnecting the acquisition apparatuses in such a manner that the apparatuses of the same rank of each group are connected in parallel by the same transmission cable to the central system.

Abstract: Water inflow inside a seismic streamer may create parasitic electric connections between lines supplying current to the electronic devices of the streamer and lines transmitting seismic informations, thus damaging the electronic apparatus and making these informations inaccurate. In accordance with the invention streamer sections including sections of supply lines and transmission lines are provided with water inflow detection assemblies, each comprising a closed circuit element surrounding the supply lines, a conducting line connected to a DC voltage generator, and means for detecting any DC voltage therebetween resulting from parasitic connections between the supply lines and the closed circuit element, created by a water inflow.

Abstract: A method for amplifying multiplexed signals including the steps of amplifying each signal in different amplifiers, each having different amplification gains, selecting the amplified signal of optimum amplitude and digitizing the selected amplified signal wherein the selection is operated by a previous measuring of the digitized value of the signal, without amplification, considered as a reference signal.

Abstract: An amplification and sampling device for multiplexed analog signals comprises a continuous chain of amplification elements, means for giving to each of said elements a gain selected from a predetermined set of values, sample-and-hold units for memorizing the amplified voltages available at the output of said elements, means for correcting the drift or noise voltage of the amplification chain and selection means for applying to the amplification chain the samples of the multiplexed analog signals or the voltages memorized in the sample-and-hold units, in accordance with the voltage level obtained at the output of the amplification chain as compared with reference voltages.

Abstract: A device for transmitting seismic data informations from acquisition devices of a seismic streamer to a central recorder an a ship, comprises at least two outward, and at least tow inward transmission lines made up of line sections interconnected by interconnection systems including means for the reconfiguration of signals, means for detecting order signals receives at said interconnection systems and switching means, and controlled by the detection means to connect different line sections, previously tested, and to by-pass faulty sections so as to form one outward and one inward continuous transmission line in good operating condition.

Abstract: The device is adapted to sample and amplify with an optimum gain multiplexed analog signals. It comprises a chain of three interconnected amplifiers, the first of which has a gain of unity, the respective gains of the two others being selected in dependence on their output voltage as compared to a reference voltage. It also comprises three memorizing capacitors each of which is adapted to memorize the output voltage of a corresponding amplifier, and switches, actuated in accordance with the gain selection for each amplifier, to make the necessary connections for operating the chain of amplifiers with the selected gain.

Abstract: A device for the sequential transmission of information elements from a sensor arrangement receiving acoustic waves at different locations and a system for recording or processing these information elements. The device includes means for generating information signals representative of the instant of reception at one of said sensor means of a directly transmitted acoustic wave emanating from a source, in the form of at least two discrete values of a continuously varying voltage which begins to be generated at the instant of reception of the direct wave, and means for determining the instant of reception from said discrete values are provided, after their transmission to the recording or processing system by a sequential transmission of the discrete values.