Abstract: A seismic signal reception device on land comprising a large number of sensors each associated with an adjusting means which may be remote-controlled from a central control and recording station, by means of seismic data acquisition boxes distributed in the field. It is possible to rapidly change at any time, from the central station, the number of sensors forming each seismic trace, the weighting coefficients of the various elementary signals constituting a trace and to control pre-processing of the signals picked-up before their transmission to the recording laboratory. By modeling the features of the reception device, interpretation of the recordings may be highly simplified.

Abstract: The seismic source (5) according to the invention is associated with a drill string (1) linking a drill bit to a surface installation close to the bit. It comprises a closed chamber (6) fastened inside a drill cellar (4) of the drill string. The section thereof is smaller than the inner section of the drill string, so as to allow free circulation of the drilling fluid. A reactive mass (8) may move within this chamber (6) and along the axis of drill string (1). Hydraulic or electro-mechanical means allow a strong alternating force of controlled frequency and duration to be applied to this mass. The energy necessary to the operating thereof is taken from the fluid current. This source requires no substantial modification in the usual drilling equipments. Drilling a well and performing seismic measurings may be achieved at the same time by means of the source by arranging sensors at the surface and/or in one or several adjacent wells.

Abstract: The method consists in performing seismic prospecting operations by using a drill bit (1) working at the bottom of a well (2), which generates very powerful acoustic jogs, in transmitting in real time or in delayed time reference signals representative of the jogs of the drill bit picked up in the immediate vicinity thereof by bottomhole sensors and in correlating the seismic signals picked up by a reception set with the reference signals coming from the bottom. The reference signals may be transmitted to the surface station through a line (4) included in a drill string (3). Absorbing elements are preferably interposed on the string to damp the vibrations propagating directly towards the surface along the drill string. Resonant elements and possibly acoustic discontinuity elements favouring resonances in the seismic frequency band may also be interposed.

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: Process for the detection of heterogeneities of a medium. It is defined in that logs of the attenuation of the shear waves and STONELEY waves are produced, the variations of each attenuation log in relation to a mean value are determined, and then the variations are compared with one another in such a manner as to determine the nature of the heterogeneity or of the petrophysical characteristic which has produced these variations. Application in particular in the area of oil and more particularly in the exploration of a medium. FIG. 9.

Abstract: A method of seismic prospecting with very high resolution as applicable in particular to exploitation of a productive hydrocarbon deposit essentially consists in transmitting and receiving acoustic waves, in recording shot moments, in determining average propagation velocities of refracted and reflected waves and in establishing a depth-section in order to determine the positions of interfaces located within the geological zone traversed horizontally by a horizontal borehole.

Abstract: A measuring device for a seismic profile within a well-bore includes resilient members such as springs which are flexible in at least two directions and are interposed between a geophone and a rigid arm connected to a measuring-tool body for applying the geophone against the wall of the well-bore during each detection of seismic waves generated at the ground surface. The elasticity of the resilient members is at least equal to the elasticity of the subsurface stratum through which the well-bore extends. The resonance frequency of the mass of the geophone with the resilient members is equal at a maximum to the resonance frequency defined by the geophone mass and elasticity of the subsurface stratum.

Abstract: A method for measuring vibrational stresses and velocities of waves propagated within formations surrounding a wellbore essentially consists in simultaneously measuring the vibrational stress and vibrational velocity produced by propagation of the vibration within the medium, then in establishing a ratio of magnitudes relating to the vibrational stress and velocity in respect of one and the same measuring point. The method and device provided by the invention also find applications in the separation of different types of secondary waves generated during propagation of a primary wave in a medium.

Abstract: Method of instantaneous acoustic logging within a wellbore.The method is characterized in that it consists of locating on drill-pipe and ground recordings elementary recordings corresponding to one and the same depth level of the drilling tool, in grouping these elementary recordings in pairs, then in intercorrelating said recordings of the pairs so as to produce in respect of each pair a correlated signal which is representative of the acoustic energy produced and of the difference in travel times of the waves received on sensors from which the pair of recordings has been obtained.A particular application is for the determination of a seismic wellbore profile.

Abstract: Method for the processing of recordings of signals resulting from a seismic exploration of a medium.It consists, after grouping recordings in pairs and crosscorrelation of the recordings of each pair, in grouping the elementary crosscorrelation functions thus obtained in at least one family in which the measuring spaces are included in a same predetermined reference space, in transforming the time variables of the said functions in order to bring the measuring space dimension to that of the reference, then in adding the transformed functions.Application in particular to acoustic logging seismic reflection or refraction.

Abstract: A method and device for making geophysical measurements in a wellbore comprising a measuring string of a plurality of measuring tools displaced along a borehole wall connected to a surface control unit by a traction system including a cable, guide pulley, connection head and junction box. The measuring tools are displaced at a relative velocity which is equal and opposite to the absolute velocity of the traction system in order to reduce the absolute velocity of the measuring tools to zero during measurement periods. The relative velocity of the tools is in the same direction as the absolute velocity of the traction system between measurement periods, with the result that the absolute velocity of the measuring tools during these periods is higher than the absolute velocity of the traction system.

Abstract: A measuring tool for producing geophysical measurements within a borehole comprises a crawler belt, at least a portion of which constitutes a support for a transducer. The crawler belt is continuously displaced within the bore hole by means of a suspension cable and guide pulley in cooperating relation with spiked shoes and retaining plates for maintaining at least the transducer-supporting portion of the crawler belt in a stationary position with respect to the borehole wall during each measurement stage.

Abstract: The invention relates to a method of seismic exploration by acoustic well logging.It is characterized in that in the traces recorded corresponding to each transmitter-receiver pair, each type of wave of interest is identified using the results of a velocity analysis, then the time of appearance in the trace of a characteristic event of the phase of the wave of interest is determined and the velocity of the wave is deduced from this time and from the thickness of the layer of formation studied.

Abstract: A method of seismic exploration using acoustic logging comprises transmitting and receiving sound waves, recording all of the signals received by the receivers, the respective positions of the emitter-receiver pair which give rise to each recording, grouping the recordings in pairs so that each recording of a given pair of sound paths have a common path segment and a part which is not common to both which is located facing the geological stratum of interest and the difference in time of arrival for at least one type of wave is measured for each pair.

Abstract: Seismic exploration on land and on ocean beds is performed by emitting vibrational acoustic signals of long time-duration within a desired frequency spectrum at one or a number of points, the signals corresponding to the waves received from the reflectors being then processed. The method further consists in forming the complex spectrum of the received signal corresponding to the emitted signal in respect of each frequency band, in forming the complex spectrum of a reference of the emitted signal in respect of each frequency band and in dividing the complex spectrum of the received signal by the complex spectrum of the reference of the emitted signal, at least an external portion of each complex spectrum being eliminated in the case of each complex spectrum.

Abstract: A method and apparatus for marine seismic prospecting in which a long spacing linear array of seismic detectors is spaced from a seismic source and connected to a recording apparatus on a survey ship. A short spacing linear array of seismic detectors is also spaced from the seismic source and signals thereof supplied to suitable channels of the recording apparatus in common with some of the signals from the long spacing detector array. The principal and auxiliary signals in the common channels are distinguishable as a result of relative amplitude and time separation.