EA041200B1 - SYSTEM AND METHOD FOR SEISMIC SENSOR SIGNAL CORRECTION - Google Patents

Description

State of the art

Seismic survey is carried out in order to obtain a map of underground objects. For example, conducting seismic surveys allows you to determine the coordinates of oil and gas deposits. Ground-based seismic surveys may use hundreds or thousands of individual seismic sensors placed in or on the ground in a grid pattern covering an area measured in many square kilometers. An explosive charge, seismic vibrator, or other suitable source of acoustic energy generates sound waves that propagate through underground objects. The sound waves are reflected back to the surface and picked up by the network's seismic sensors. The signals from the sensors are accumulated and used to build a map of underground objects in the seismic survey area.

Brief description of the drawings

In the following detailed description of particular embodiments, reference is made to the accompanying drawings, in which FIG. 1 is a flow diagram of a method for correcting a seismic sensor signal in accordance with the principles disclosed herein;

in fig. 2 is a block diagram of a seismic data acquisition unit suitable for use in seismic sensor signal correction;

in fig. 3 is a block diagram of a device suitable for testing a seismic sensor and allowing the transfer function of the seismic sensor to be determined;

in fig. 4 is a block diagram of a seismic data acquisition system including seismic data acquisition units (SDAUs) suitable for use in seismic sensor signal correction;

in fig. 5 is a block diagram of retrieving raw (raw) seismic data and a seismic sensor transfer function from a seismic data acquisition unit for use in seismic sensor signal correction;

in fig. 6 is a block diagram of a processing system for correcting a seismic sensor signal; and in FIG. 7A-7B show, respectively, the spectral composition of a particular example of raw seismic data, the frequency response of the inverse filter used to correct the sensor signal, and the spectral composition of the filtered seismic data in accordance with the principles set forth in the disclosure.

Notes on terminology used

In the discussion and formula below, the use of the terms including and containing is not intended to be limited, and therefore should be taken to include but not be limited to .... The term bind should not be understood to limit the interaction between elements to direct interaction, and may also include indirect interaction between described elements. The term software includes any executable code that can be used by a processor, regardless of the medium used to store that software. However, code stored in memory (eg, read-only memory) and sometimes referred to as firmware is covered by the term software. An enumeration based on is intended to mean based at least in part on. So if X is based on Y, then X can be based on Y and any number of additional factors.

Detailed description of the invention

Sensors used to detect seismic energy (eg, seismic sensors) may be based on any of a wide variety of sensor technologies. For example, seismic data acquisition systems may use pressure transducers such as piezoelectric crystals, velocity sensors such as seismographs, and acceleration sensors such as accelerometers to detect seismic energy.

Traditionally, land seismic survey data has been predominantly recorded by seismographs. The seismograph includes a wire coil located in a magnetic field, which can be made either in the form of a moving magnet or in the form of a moving coil, the latter option being more preferable for seismic surveys. In a moving-coil seismograph, a magnet is attached to a housing that is rigidly fixed to the ground so that the housing and magnet move with the displacement of the earth. A movable electric coil is placed in the magnetic gap of the magnet and freely attached to the body of the seismograph by soft springs so that the coil can only move along one axis. As the coil moves along this axis relative to the fixed magnet, it traverses the magnetic flux lines in succession and generates a voltage and current at its electrical terminals in proportion to the earth's displacement rate. In a moving-coil seismograph, the coil forms an accelerated, or reactive, mass.

The coil-spring system will have a resonant frequency depending on the mass of the coil and the compliance of the springs. At frequencies well below the resonant frequency, the coil and magnet move together.

- 1 041200 stno, resulting in low sensitivity and low output voltage or current. As the vibration frequency rises to the resonant frequency of the seismograph and above, the sensitivity and output signal respectively increase, reach a peak value, and then the frequency dependence decreases. Usually the resonant frequency of seismographs is in the range from 10 to 30 Hz, with preference given to lower frequencies. Resonance at a low frequency requires high compliance of the springs. This requires soft springs, which, in turn, imposes strict requirements on the design and manufacture of the sensor to ensure the desired sensitivity, accuracy, linearity, and protection from distortion due to axis shift, which are necessary for recording seismic signals. Design trade-offs between field strength, magnet size/weight, coil geometry, and spring compliance are critical to the design and manufacture of a seismograph with sufficient sensitivity, output voltage/current, linearity, and accuracy to measure both large and small surface vibrations.

Another type of sensor used for seismic surveys uses an electrical capacitance to generate a signal. These sensors are typically implemented as microelectromechanical systems (MEMS) using micromachined silicon, where a metal coating is applied to the face components on both sides of a small accelerated mass coated and suspended by springs. The advantage of MEMS sensors over moving-coil seismographs is their small size and weight. The movement of the accelerated MEMS mass relative to other fixed plates causes a change in capacitance, which can be perceived as a vibration signal proportional to the acceleration resulting from the displacement of the sensor. The springs are formed by regions of thin-layer silicon, providing a small linear displacement with resonant frequencies above 1 kHz. The small surface area forming the capacitor, the high resonant frequency, and the limitation of the amount of linear displacement mean that the sensitivity will be quite low compared to that of a moving coil seismograph. To compensate for the low sensitivity, special electronics are used to keep the MEMS geophone in a force feedback state. This extra electronics takes up space and consumes power, which offset some of the size and weight advantages of MEMS over a passive moving coil seismograph.

The seismograph and MEMS accelerometer convert the oscillatory displacement of the earth caused by the propagation of seismic waves into a proportional signal voltage that can be registered as a function of time. The oscillatory displacement of the earth causes the body of a seismograph or MEMS, which is attached to the earth, to move in synchronism with the amplitude of the propagating seismic wave at a given point in space. Due to its inertia, the accelerated mass of the coil of a seismograph or silicon microelectromechanical system remains relatively stationary, causing the housing to move relative to the coil, or accelerated mass. This relative movement of the housing and coil, or accelerated mass, is converted into a proportional voltage fluctuation, allowing the seismic wave to be detected. To ensure effective operation of the device, its sensitivity must be sufficient to obtain an undistorted response to the smallest ground displacements. This requires a strong, heavy magnet and an expensive wound coil in the case of seismograph sensors, or expensive micromachined precision components and power-consuming electronics in the case of MEMS accelerometers. Expensive sensors provide high quality data, but unfortunately increase the overall cost of seismic data acquisition.

To reduce the cost and weight of seismic acquisition equipment, seismic sensors using piezoelectric elements have been proposed. While piezoelectric pressure transducers have been widely used in offshore exploration, sensors based on piezoelectric elements have generally been considered unsuitable for terrestrial exploration because their accuracy was assumed to be insufficient.

Embodiments of the systems and methods disclosed herein reduce the overall cost of obtaining seismic data by reducing the cost of associated equipment. As noted above, the development and testing of conventional seismic sensors maintains high accuracy and stable performance and, as a result, requires relatively expensive components that greatly increase the overall cost of seismic data acquisition. Embodiments of the present invention allow less expensive components to be used to acquire seismic data, thereby reducing the overall cost. The performance of seismic sensors used in the systems and methods described in this disclosure may be less accurate and/or stable than those of conventional seismic sensors. Accordingly, the seismic sensors used in the systems and methods disclosed herein may be less expensive than conventional seismic sensors because the design parameters and/or their testing may be less stringent. Embodiments compensate for the use of less accurate/stable seismic sensors by individually correcting the seismic data acquired by each sensor using a sensor-specific inverse filter, thereby compensating for performance differences.

- 2 041200 listings for many seismic sensors used in seismic surveys.

In FIG. 1 is a flowchart for implementing a method 100 for correcting seismic sensor sensitivity, in accordance with the principles set forth in this disclosure. The above sequence of steps is chosen for convenience and at least some of the steps shown may be performed in a different order or performed in parallel. Furthermore, in some embodiments, only some of the actions shown may be performed. In some embodiments, at least some of the steps of method 100, as well as other steps described herein, may be performed as instructions stored in computer readable memory and executed by one or more processors.

In the step indicated by block diagram element 102, the manufacture of the seismic sensor is performed. The seismic sensor may be a seismograph, a MEMS accelerometer, a piezoelectric sensor, or any other type of sensor suitable for use in obtaining seismic data. The performance requirements of a seismic sensor may be relatively loose compared to conventional seismic sensors. For example, uniformity in frequency, amplitude, and/or phase responses between sensors may not be as high as with conventional sensors. In some embodiments, the seismic sensor may be embedded in a seismic data acquisition unit including the seismic sensor and electronic circuitry for processing and/or storing seismic signals detected by the seismic sensor. In other embodiments, the seismic sensor may not be part of the seismic data recorder, but may be connected to a separate seismic data recorder.

In step 104, the seismic sensor is tested and its transfer function is determined from the test results. For example, the seismic sensor may be mounted on a vibration or shock generator, such as a shaker, which moves the seismic sensor in accordance with a predetermined oscillation law. The choice of waveform may move the seismic sensor such that the signals generated by the seismic sensor in response to this movement can be used to determine the sensitivity of the seismic sensor over a range of frequencies. Accordingly, the oscillation can have a frequency change in a given frequency range (for example, 10-200 Hz), a linear frequency modulation in a given frequency interval, an impulse or an oscillation of any other form, which makes it possible to determine the sensitivity of the seismic sensor in the frequency interval by the response of the sensors to a movement corresponding to vibration form. The sensitivity (eg, amplitude and/or phase sensitivity) of a seismic sensor as a function of frequency is referred to herein as the transfer function of the seismic sensor. In other words, the transfer function of the seismic sensor establishes the relationship between the movement of the seismic sensor and the signal generated by this sensor in response to this movement. The signals generated by the seismic sensor in response to movement of the vibrator are time domain signals, and deriving the seismic sensor transfer function may involve converting the time domain signals to frequency domain signals that determine the amplitude and/or phase of the signals generated by the seismic sensors at each frequency. in a given frequency interval.

In some embodiments, testing the seismic sensor may also include determining the movement of the shock or pulse generator by means of a reference sensor attached to the device. The reference sensor may have a known accuracy, and the output of the reference sensor can be considered to accurately represent the movement of the seismic sensor during testing and form a reference value for comparison with the signals generated by the seismic sensor.

In step 106, the seismic sensor transfer function is stored for access and use in correcting the seismic data received by the sensor. The transfer function may be stored in a ROM included in the seismic data acquisition unit that includes the seismic sensor. The transfer function may also be stored in a database or secondary storage accessible to a seismic data processing system that, after using the seismic sensor in a seismic survey, will process the seismic data signals generated by the seismic sensor during a survey.

At step 108, after the seismic sensor has been tested and its transfer function recorded, the seismic sensor is transported to the survey area for use in seismic exploration.

At step 110, the seismic sensor is in the survey area and is ready for use in seismic data acquisition. The seismic sensor can be re-tested in the field (on-site) to confirm that the sensor transfer function has not changed since production testing. Accordingly, a service site where seismic sensors are prepared and maintained (for example, repair, testing, etc.) when they are used in a seismic survey, may include a vibration generator and

- 3,041,200 shocks, suitable for seismic sensor testing as described generally in step 104. For example, a frame or fixture that houses or secures multiple seismic data recorders (each with a seismic sensor) may include a generator vibration or shock, suitable for testing a seismic sensor. In some embodiments, each seismic data acquisition unit may include electronic circuitry to allow the seismic sensor to be tested by giving it motion from an external source. For example, the test circuits in the seismic data acquisition unit may generate an electrical signal (eg, ramp, pulse, step function, etc.) that acts on a seismic sensor (eg, a seismograph coil) and registers the movement of the sensor in response to this signal and processing to determine the transfer function of the seismic sensor.

At step 112, the transfer function determined at the test site can be stored as control information for later checks. For example, the transfer function may be stored in ROM in the seismic data acquisition unit including the seismic sensor in addition to or in place of the seismic sensor transfer function obtained from production testing.

The transfer function may also be stored in a database or secondary storage accessible to the seismic data processing system which, after using the seismic sensor in a seismic survey, performs processing of the seismic data signals generated by the seismic sensor during the survey.

In some embodiments, the transfer function obtained under survey conditions may be compared to the transfer function obtained during production testing. If the comparison shows that the transfer function has changed more than allowed, the seismic sensor can be flagged for further testing or repair.

At step 114, a seismic sensor is mounted to acquire seismic data. The seismic sensor senses the movement of the earth's surface and generates signals indicative of the detected movement of the earth's surface (ie, generates seismic data/seismic signals). A seismic data acquisition unit associated with the seismic sensor performs pre-processing and storage of the seismic data (ie, raw seismic data). In some embodiments, the seismic data acquisition unit may transmit seismic data to another component of the data acquisition system for further processing and/or storage. In some embodiments, the seismic data recorder stores the seismic data in internal memory for later retrieval (eg, after the seismic data recorder is decommissioned).

In step 116, the seismic data obtained in step 114 and stored in the seismic data acquisition block is retrieved, read or received from this block. Retrieval can be done via a wired or wireless link to the seismic recorder after the recorder has been moved from the survey site to the service site, or when the seismic recorder is at the survey site.

In step 118, if the seismic sensor transfer function is stored in a seismic data acquisition block, the transfer function is extracted, read or received from this block. The transfer function may include the transfer function stored in the seismic data recorder during production testing and/or the transfer function stored in the seismic data recorder during field testing.

In some embodiments, at step 118, additional data may be retrieved, read, or received from the seismic data recorder. For example, in some embodiments, at step 118, the exemplary transfer function stored there may be retrieved from the seismic data recorder. The exemplary transfer function may be an ideal seismic sensor transfer function, a typical seismic sensor transfer function, or another transfer function to which the seismic data extracted from the seismic data recorder must be matched during processing.

In step 120, the raw seismic data and optional transfer function(s) read from the seismic data recorder are formatted for transfer or transmission to the seismic data processing center. For example, the identification code of the seismic sensor that acquired the raw seismic data and the transfer function of that seismic sensor may be recorded as header data associated with the raw seismic data. The seismic sensor identification code may include a serial number, model number, manufacturer identification code, and/or other information that uniquely identifies the seismic sensor.

At step 122, the formatted raw seismic data is transmitted to the seismic data processing center using seismic data processing algorithms. Primary dans

- 4 041200 Data may be recorded on magnetic tape, optical recording media, or other medium designed to physically transfer data to a processing center. Alternatively, the primary seismic data may be transmitted to the seismic data processing center by transmission over a public and/or private wired and/or wireless network. The seismic data processing center may not be located where the seismic survey is being conducted, but elsewhere. For example, the seismic data processing center may be located many kilometers away from the seismic survey site and seismic data acquisition equipment. Meanwhile, the seismic data processing center and the seismic data processing system of the seismic data processing center separated and remote from the seismic data acquisition system and remote from the seismic survey site may be called a remote seismic data processing center and a remote seismic data processing system.

In step 124, the raw seismic data generated by the seismic sensor during the seismic survey is accessed and converted (manipulated) by the seismic data processing system. For each raw seismic gather, the seismic data processing system identifies the seismic sensor that generated that gather. In some embodiments, the seismic data processing system may interpret the header associated with the raw seismic data gather to extract a sensor identification code. Alternatively, information relating the raw seismic data to the seismic sensor that generated the data may be provided to the processing center in another form, such as a table containing information linking the sensor identification to the seismogram identification.

In step 126, the seismic data processing system, having identified the particular seismic sensor that generated the gather of the raw data in process, extracts the transfer function of that seismic sensor. The seismic data processing system may access a database or other secondary storage system containing transfer functions of any number of different seismic data classified for access based on seismic sensor identities. In some embodiments, the seismic data processing system may extract the transfer function from a header associated with the raw data gather or other data structure including raw seismic data associated with the transfer function and the seismic sensor.

In some cases, there may be multiple transfer functions for a seismic sensor. For example, it could be a transfer function generated during production testing and a transfer function generated during field testing for a survey. The seismic data processing system may select one or more transfer functions to use in processing the raw seismic data. For example, the seismic data processing system may select the most recent transfer function received, or may select any of the transfer functions deemed to be the most accurate.

In step 128, the seismic data processing system generates an exemplary transfer function for the seismic sensor. The reference transfer function may be a seismic sensor reference transfer function provided by the seismic sensor manufacturer. For example, a reference transfer function may be derived from the displacement of a vibration or shock generator used to test a seismic sensor measured by a displacement transducer of known accuracy during the seismic sensor test. In some embodiments, the exemplary transfer function may be calculated as the average transfer function of a number of seismic sensors. For example, a seismic sensor manufacturer may generate an exemplary transfer function as the average of the transfer functions of a plurality of sensors (eg, all sensors manufactured in a given time interval) manufactured by the manufacturer.

In some embodiments, the seismic data processing system may generate an exemplary transfer function based on the transfer functions of the seismic sensors used in the seismic survey in which the primary seismograms were generated. For example, the exemplary transfer function may be generated as the average of the transfer functions of seismic sensors used in a seismic survey within a predetermined geographic proximity to the seismic sensor that generated the primary gather. Alternatively, the seismic data processing system may generate an exemplary transfer function based on another selected set of seismic sensors. For example, the seismic data processing system may generate a reference transfer function as the average of the transfer functions of all seismic sensors used in the seismic survey from which the primary gather was acquired.

At step 130, the seismic data processing system generates an inverse filter to be applied to the primary gather. The inverse filter is based on the transfer function of the seismic sensor that received the primary gather and the exemplary transfer function.

- 5 041200

The inverse filter allows the transfer function of the seismic sensor to be matched to the exemplary transfer function. When applied to the primary gather, the inverse filter corrects the spectral parameters of the primary spectrogram so that the spectral parameters of the gather after filtering by the inverse filter basically match the reference transfer function.

In step 132, the seismic data processing system applies an inverse filter to the primary gather to bring the spectral parameters of the primary gather to the reference transfer function. The application of the inverse filter may include the operation of convolution of the primary seismogram and the inverse filter. The seismic data processing system may process each primary gather, as described in steps 124-132 above, to produce gathers of data consistent with the desired seismic sensor transfer function, while the actual seismic sensor transfer functions may vary greatly. After the raw gathers have been corrected by making changes to the sensor sensitivity, the seismic data processing system can apply additional processing to the gathers to produce an image of the subsurface appropriate to the seismic survey. For example, automatic gain control, noise reduction, filtering, kinematic correction, velocity analysis, migration, and other processing operations can be applied to convert inversely filtered seismic data into a subsurface image.

In FIG. 2 is a block diagram of a seismic data recorder unit 200 for use in seismic sensor sensitivity correction, in accordance with the invention disclosed herein. The seismic data acquisition unit 200 includes a seismic sensor 202, a signal conditioning circuit 204, a timing and control circuit 206, a signal storage circuit 208, a transfer function storage circuit 210, and a communication interface 212. For clarity, seismic data acquisition unit 200 may include additional components that have been omitted in FIG. 2. For example, the seismic data recorder 200 may include batteries, power circuits, etc.

The seismic sensor 202 may be a seismograph, accelerometer, piezoelectric sensor, or other sensor suitable for use in seismic data acquisition (eg, any sensor that can detect ground movement). In some embodiments of the seismic recorder 200, the seismic sensor 202 may be housed within the same housing as the signal conditioning circuit 204, the timing and control circuit 206, the signal storage circuit 208, and other components of the seismic recorder 200. Alternatively, the seismic sensor 202 may be placed outside the seismic recorder 200 and connected to the seismic recorder 200 via a communication interface (eg, an electrical or other connection via a connector or port on the seismic recorder 200).

Signal conditioning circuitry 204 may include an amplifier, filter, analog-to-digital converter, or other circuitry that generates the output signal of seismic sensor 202. In some embodiments, signal conditioning circuitry 204 may include test circuitry for applying a test signal/signal to seismic sensor 202. Such circuitry The test may include a pulse generator, an oscillator, a variable frequency generator, etc. to generate signals used to drive the seismic sensor 202 to test the transfer function of the seismic sensor.

The timing and control circuit 206 includes a timing circuit controlling the timing of operation of the seismic data acquisition unit 200 . For example, timing and control circuitry 206 may include circuitry that controls the timing of sampling and digitizing the outputs of seismic sensor 202. Control functions may be performed by a dedicated control circuit, such as a state machine, or by a microcontroller or other programmable control element that executes commands. The control functions may include parameterization of the signal conditioning circuit 204, control of access to the memory devices 208, 219, and control of communication with external devices via the communication interface 212.

Signal storage device 208 may include volatile and/or non-volatile memories that store seismic data output from seismic sensor 202. For example, acquired seismic data may be stored in flash memory or other non-volatile memory (ROM) until the seismic data is retrieved, for example, after the seismic data recorder 200 has been decommissioned and moved to a service yard for charging and/or other maintenance.

The transfer function store 210 may include a ROM storing one or more seismic sensor 202 transfer functions. For example, flash memory or another type of ROM may store seismic sensor 202 transfer functions generated during sensor manufacture or field testing. The transfer function may be read from the transfer function store in parallel with the extraction of seismic data from the signal store 208 . The signal storage device 208 and the transmission data storage device 210

- 6 041200 functions can be in the same memory or in different memories. For example, in some embodiments, a first portion of this memory may be allocated for use as a signal store 208, and a second portion of this memory may be allocated for use as a transfer function store 210.

The communication interface 212 allows the seismic data recorder 200 to communicate with other devices via wired or wireless means. For example, the communication interface may include an electrical connector for communicating the seismic data recorder 200 with a wired communication network or other device, or may include an antenna or optical communication device for communicating the seismic data recorder 200 with a wireless communication network. The communication interface 212 may also include a transceiver for transmitting and receiving on the communication line, a modulator, a demodulator, an encoder and decoder, and other circuitry for communication between the seismic data recorder 200 and other devices. Through the communication interface 212, the seismic data acquisition unit 200 can perform loading of seismic data stored in the signal storage device 208, loading of the transfer function stored in the transfer function storage device 210, loading of the transfer function to be stored in the transfer function storage device 210, loading of commands and parameters used to control and configure the seismic data recorder 200 and/or download state information generated by the seismic data recorder 200 .

In FIG. 3 is a block diagram of an apparatus 300 for testing a seismic sensor 202 to determine the transfer function of the seismic sensor 202 in accordance with the disclosed principles of the invention. The device 300 can be used to test the sensor 202 and obtain the transfer function of the seismic sensor 202 according to step 104 of the flowchart in FIG. 1. Apparatus 300 includes a vibration generator 302, a vibration measurement and control circuit 304, a sensor transfer function determination logic 306, and a sensor transfer function database 308. The vibration generator 302 may be a shaker or other device that creates a controlled movement. The seismic sensor 202 may be attached to the shaker 302. In FIG. 3, the seismic sensor 202 is located inside the seismic data acquisition unit 200 . Accordingly, the seismic recorder 200 is attached to the shaker 302. Under such testing conditions, the resulting transfer function may be affected by parameters or circuitry features of the seismic recorder 200 (e.g., mechanical damping, signal conditioning circuitry 204, etc.) .

The vibration measurement and control circuit 304 includes circuitry that controls the movement of the vibration generator 302 in response to a predetermined waveform (e.g., pulse or frequency hop) acting on the seismic sensor 202. The vibration measurement and control circuit 304 may also include circuitry that measures and records movement. vibration generator with a given accuracy. For example, the vibration measurement and control circuitry 304 may include an accelerometer of known accuracy mounted on the vibration generator 302 and circuits for processing and storing the accelerometer output signal.

The sensor transfer function logic 306 receives the vibration generator displacement signals generated by the seismic sensor 202 and processes the signals to determine the transfer function of the seismic sensor 202. The sensor transfer function logic 306 may provide the transfer function to the seismic data acquisition unit 200 for storage in the transfer function storage device 210, and may transfer the transfer function to the sensor transfer function database 308 for storage.

The sensor transfer function database 308 receives the transfer function and the identification code of the seismic sensor 202 and/or the seismic data recorder 200 from the sensor transfer function determination logic 306 and stores the transfer function for extraction based on the identification of the seismic sensor 202 and/or the seismic recorder 200 seismic data. The sensor transfer function database 308 may include a relational database, an object-oriented database, or other data storage device that provides data access and retrieval. The sensor transfer function database 308 may be accessed by a seismic data processing system to extract the transfer function of the seismic sensor 202.

The sensor transfer function determination logic 306 and the sensor transfer function database 308 may be implemented in a computer executing instructions to obtain a transfer function from the data received from the seismic data acquisition unit 200 and to store and access the transfer function based on seismic identification. sensor 202 and/or block 200 registration of seismic data.

In FIG. 4 is a block diagram of a seismic data acquisition system 400 including seismic data acquisition units (SDAUs) 200 suitable for use in seismic sensor sensitivity correction in accordance with the invention disclosed herein. For clarity of presentation, in FIG. 4 only one subsurface boundary 406 is shown. In reality, there may be many interfaces in the subsurface caused by changes in the acoustic stiffness of the material. Changes in acoustic stiffness can be caused by changes in rock type causing changes in its acoustic hardness.

The source 402 of seismic signals is located on the surface 404 of the earth. The seismic signal source 402 generates steered seismic waves to propagate through the subsurface. Examples of seismic signal sources include explosions, auto-moving vibroseis, and drop-weight systems, also known as auto-moving vibroseis. For example, a seismic percussion rig may strike the earth's surface 404 with a weight or hammer, creating an impact that propagates through the subsurface as seismic waves 410. The seismic waves propagate downward through the subsurface from a seismic signal source 402. The seismic waves are then reflected, at least in part, from the interface 406. Reflection is caused by density and/or elastic wave velocity differences between materials above and below interface 406 . Further, reflected seismic waves 412 propagate upward from interface 406 to surface 404. At surface 404, reflected seismic waves 412 are sensed by seismic sensors 202 associated with seismic data recorders 200 . The seismic data recorders 200 store in the signal storage device 208 and/or transmit data indicative of the received seismic wave to a separate storage device. This data can then be corrected using the transfer function of the seismic sensor 202 to determine the composition and structure of the subsurface.

It should be understood that the above is only a particular example, and the subsurface may have a more complex structure or composition. As a result, the wave reflection pattern can be much more complex than shown in the diagram. For example, a portion of the downwardly propagating seismic wave 410 may not be reflected from the interface 406 and continue to move through this interface. This wave may subsequently reflect off the underlying interface, with the result that many reflections may be received by any given seismic sensor. The principle described above is not limited to receiving seismic signals at the surface and can be applied to marine seismic surveys. In this case, the interface 406 is covered by a layer of water. The seismic data acquisition unit 200 may be located on the seafloor or, alternatively, in or on the water surface. For marine seismic surveys, other seismic signal sources 402 may be used, such as air guns or plasma sounding sources.

In FIG. 5 is a block diagram of retrieving raw seismic data and a sensor transfer function from seismic data acquisition unit 200 for use in seismic sensor sensitivity correction, in accordance with the principles disclosed in the present invention. In FIG. 5, with the block 200 seismic data is connected by means of communication (for example, via the interface 212) node 502 extraction. Node 502 extraction may be located on the service site near the area of the seismic survey using block 200 seismic data. After seismic data acquisition using the seismic data acquisition unit 200, as described with reference to FIG. 4, the seismic data recorder 200 can be moved to a service site and connected to the extraction unit 502 by means of communication. An extraction node 502 extracts the raw seismic data and the sensor transfer function from the seismic data acquisition unit 200 using a wired and/or wireless communication link. Extraction node 502 may format the raw seismic data for use by the seismic acquisition system. For example, extractor 502 may attach a header to each gather of the raw seismic data. The header may include, for example, the geographic location of the sensor 202 and source 402 during acquisition of the seismogram, the identification code of the sensor 202 and/or seismic data recorder 200, the transfer function of the sensor 202, and other information necessary to process the raw seismic data gather.

Extraction unit 502 may be implemented in a computer that executes instructions to extract the raw seismic data and the sensor transfer function from the seismic data acquisition unit 200 and to format the raw seismic data and the sensor transfer function for use in a seismic data processing system.

In FIG. 6 is a block diagram of a seismic data processing system 600 for correcting seismic sensor sensitivity in accordance with the invention disclosed herein. The processing system 600 includes a processor 602, a memory 604, and a sensor transfer function database 308. Processor 602 is configured to execute instructions retrieved from memory 604. Processor 602 may include any number of cores or subprocessors. Suitable processors include, for example, general purpose processors, digital signal processors, and microcontrollers. Processor architecture usually includes functional modules

- 8 041200 (for example, fixed point, floating point, integer variable, etc.), storage device (for example, registers, memory, etc.), instruction decoding, peripheral modules (for example, interrupt controllers, timers, DMA controllers, etc.), I/O systems (eg serial ports, parallel ports, etc.) and various other components and subsystems.

The developed software, including the instructions executable by the processor 602, is stored in the storage device 604. The storage device 604 is a non-volatile computer-readable medium. The computer-readable storage medium may include volatile storage, such as random access memory (RAM), non-volatile storage (eg, read-only memory (ROM), programmable read-only memory (PROM), hard disk drive, optical storage (eg, CD or DVD) , flash memory) or combinations thereof.

Memory 604 contains commands 606 to determine the sensor transfer function, commands 608 to determine the exemplary transfer function, commands 610 to extract the inverse filter, and commands 612 inverse filtering. Memory 604 may also contain raw seismic gathers 614 and inversely filtered gathers 616, and additional instructions for converting the inversely filtered gathers 616 into a subsurface image. The sensor transfer function determination instructions 606 are executed by the processor 602 to extract the transient function of the seismic sensor 202 that generates the primary gather to be processed. To extract the transfer function, processor 602 identifies the seismic sensor that generated the primary gather. In some embodiments, processor 602 may parse a header associated with the primary gather to extract the sensor identification. Alternatively, processor 602 may access information associating the raw seismic data with the seismic sensor that generated the data sent to processor 602 in another form, such as a table containing information associating sensor identification with seismogram identification.

Once a seismic sensor has been identified that generated a gather of the raw seismic data in process, processor 602 extracts the seismic sensor transfer function. The processor 602 may access a sensor transfer function database 308 or other secondary memory system containing the transient functions of any number of different seismic sensors 202 classified for access based on the seismic sensor identification information. In some embodiments, processor 602 may extract a transfer function from a header associated with the primary gather or other structure containing raw seismic data associated with the transition function and seismic sensor 202.

If there are multiple transfer functions for seismic sensor 202, processor 602 may select one of the transfer functions to use in processing the raw seismic data. For example, processor 602 may select the last transfer function generated, or one of the transfer functions considered to be the most accurate.

Model transfer function determination instructions 608 are executed by processor 602 to generate a transfer function that the raw seismic data will correspond to after back filtering. The reference transfer function may be a reference transfer function for a seismic sensor provided by the manufacturer of the seismic sensor 202. For example, the reference transfer function may be derived from the displacement of the vibration generator 302 used to test the seismic sensor 202, determined by the displacement transducer with known accuracy when performing a seismic test. sensor 202. Such an exemplary transfer function may be stored in the sensor transfer function database 308 or the internal memory of the seismic data recorder. Accordingly, the model transfer function determination commands 608 may extract the model transfer function from the header associated in the primary gather, or refer to the sensor transfer function base 308 to extract the model transfer function.

In some embodiments, the implementation of the exemplary transfer function can be calculated as the average transfer function of a number of seismic sensors 202. For example, a manufacturer of seismic sensor 202 can generate an exemplary transfer function as the average of the transfer functions of multiple sensors (for example, all sensors 202 manufactured during a certain time interval ) issued by the manufacturer. Such exemplary transfer functions (eg, those generated by the manufacturer) may be stored in and retrieved from the sensor transfer function database 308 .

In some embodiments, the processor 602 may generate an exemplary transfer function based on the transfer functions of the seismic sensors 202 used in the seismic survey and received the raw seismograms to be processed. For example, the exemplary transfer function may be generated as the average of the transfer functions of the seismic sensors 202 used in a seismic survey within a given geographic area around the seismic sensor 202 from which the primary seismogram was acquired. Alternatively, the processor 602 may create a reference transfer function as the average of the transfer functions of all seismic sensors 202 used in the seismic survey through which the primary gather was obtained. The processor 602 may extract the transfer functions of the sensors 202 for averaging from headers or from a database of sensor transfer functions, as described above.

Inverse filter extraction instructions 610 are executed by processor 602 to obtain an inverse filter to be applied to the primary gather to match the gather to the model transfer function. The inverse filter is based on the transfer function of the seismic sensor 202 that received the primary gather and the exemplary transfer function. When applied to the primary gather, the inverse filter corrects the spectral parameters of the primary gather so that the spectral parameters of the primary gather basically match the reference transfer function.

Inverse filter instructions 612 are executed by processor 602 to apply an inverse filter to the primary gather to match the gather to the model transfer function. In FIG. 7A shows the frequency content of a raw seismic data gather acquired by a seismic sensor 202 having an appropriate transfer function. In FIG. 7B shows the inverse filter response configured to match the seismic data to the exemplary transfer function. In FIG. 7B shows the frequency content of the seismic data after applying an inverse filter to the raw seismic data.

In the drawings and in the description of the present disclosure, like parts are generally referred to throughout the description and drawings with the same reference numerals. The drawings are not necessarily drawn to scale. Some features of the invention may be highlighted by magnification or some graphic features, and many details of conventional elements may be omitted in the interests of clarity and brevity of presentation. The present disclosure is capable of being implemented in various forms. Particular embodiments are described in detail and shown in the drawings, it being understood that the present disclosure should be considered as an example of the implementation of the principles of the invention, and that it is not limited only by the description and drawings presented. It should be clearly understood that the various ideas and components of the embodiments presented below can be used individually or in any suitable combination to achieve the expected result. For example, an embodiment of the system may include a device 300, a seismic data acquisition system 400, an extraction node 502, and a seismic data processing system 600, or any combination thereof.

The above discussion is intended to illustrate the various principles and embodiments of the present invention. While some embodiments have been shown and described, modifications thereof may be made by any person skilled in the art within the spirit and principles of the invention. The embodiments described herein are presented by way of example only and do not limit the invention. Accordingly, the scope of the invention is not limited to the above description, but is defined only by the following formula, and also includes all equivalents of the subject matter of the invention according to the formula.

According to a first feature, the seismic data acquisition and processing system includes a seismic data acquisition unit, comprising a data storage device (memory) configured to store a transfer function of a seismic sensor connected to the seismic data acquisition unit; and a second storage device (memory) configured to store signals generated by the seismic sensor; a data retrieval unit configured to retrieve from the seismic data recording unit the signals stored in the data storage memory; and formatting signals for their transmission to the seismic data processing system; a sensor testing device configured to: supply a test effect to the seismic sensor during testing at the installation site; recording the response of the seismic sensor to the test action; processing the response to generate a transfer function; and storing the transfer function for use by the seismic data processing system in generating an inverse filter that, when applied to the signals, modifies the parameters of the signals to match those generated by the seismic sensor having the exemplary transfer function.

The seismic data processing system may be configured to: receive signals formatted by the data extraction node; identifying a seismic sensor connected to the seismic data recording unit that generated the signals; extracting a sensor transfer function corresponding to the seismic sensor; generating, based on the sensor transfer function and the exemplary transfer function, an inverse filter; and applying an inverse filter to the signals.

The seismic data processing system may also/alternatively be configured to generate a model transfer function that is an average of the transfer functions of a plurality of seismic sensors.

In any of the above embodiments, the test action may be in the form of a pulse or frequency sequence applied to the seismic sensor to move it.

In any of the above embodiments, the sensor test apparatus may be configured to compare the sensor transfer function generated during production testing with the sensor transfer function generated during field testing; generating a notification signal based on differences between the sensor transfer function generated during production testing and the sensor transfer function generated during field testing exceeding a predetermined value.

The sensor may include at least a piezoelectric crystal or a seismograph or an accelerometer.

The seismic data acquisition unit may comprise a transfer function memory configured to store a sensor transfer function corresponding to the seismic sensor.

The data retrieval unit may be configured to extract the transfer function from the transfer function memory; and formatting the transfer function for transmission to the seismic data processing system in parallel (in combination) with the signals.

According to the first method, a seismic data processing method is provided, wherein: receiving, by a seismic data processing system, signals representing seismic data recorded at a remote site;

receiving, by means of the seismic data processing system, together with the signals, an identification code of the seismic sensor through which the signals were received;

extracting, by means of the seismic data processing system, a sensor transfer function corresponding to the seismic sensor and relating the movement of the seismic sensor to the signals;

generating, by means of the seismic data processing system, based on the sensor transfer function and the exemplary transfer function, an inverse filter which, when applied to the signals, modifies signal parameters to conform to the exemplary transfer function;

applying by means of the seismic data processing system an inverse filter to the signals to bring the parameters of the signals in line with the exemplary transfer function.

The method further stores the transfer function of the sensor in a memory for storing data of the seismic data recorder connected to the seismic sensor before placing the seismic data recorder at the seismic survey site;

after using the seismic data recorder to record the seismic data, retrieving the signals stored in the data storage memory of the seismic data recorder; and format the signals for transmission to a remote data processing system.

The method may additionally/alternatively subject the seismic sensor to a test action during manufacturing or site testing, the test action comprising at least an impulse or frequency interval action used to move the seismic sensor;

record the response of the seismic sensor to the test action;

process the response to obtain a transfer function; and store the transfer function for use by the remote data processing system when generating the inverse filter.

The seismic sensor transfer function generated during production testing can be compared with the seismic sensor transfer function generated during on-site testing; and a notification signal may be generated based on differences between the sensor transfer function generated during production testing and the sensor transfer function generated during site testing when these differences exceed a predetermined level.

Any of the presented methods may also include generating, by the seismic data processing system, an exemplary transfer function representing the average of the sensor transfer functions of a plurality of seismic sensors.

In any of the above methods, the transfer function can be additionally extracted from the memory for the transfer functions of the seismic data recorder; and format the transfer function for transmission to a remote data processing system in parallel with the signals.

According to the second method, a seismic data processing method is provided, wherein, during production testing of a sensor to be used for seismic data acquisition, a sensor transfer function for the seismic sensor is obtained;

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Claims (17)

storing a sensor transfer function for use by the seismic data processing system when generating an inverse filter; in the seismic data acquisition process, seismic data is acquired by the seismic sensor; retrieving seismic data from a seismic data acquisition unit coupled to the seismic sensor; formatting the seismic data for transmission to a seismic data processing system located remotely from the seismic data acquisition unit, the formatting providing an identification code for transmitting it with the seismic data; during processing of the seismic data by the seismic data processing system, extracting a sensor transfer function using a seismic sensor identification code; generating, based on the sensor transfer function and the exemplary transfer function, an inverse filter that, when applied to the seismic data, changes the parameters of the seismic data to match the seismic data generated by the seismic sensor having the exemplary transfer function; applying, by means of the seismic data processing system, an inverse filter to the seismic data to match the parameters of the seismic data to seismic data produced by a seismic sensor having an exemplary transfer function. According to the first or second method, when storing the sensor transfer function, it may be stored in a data storage memory of a seismic data recorder connected to the seismic sensor, or it may be stored in a database accessible to the seismic data processing system. In embodiments, upon obtaining the transfer function of the sensor, the seismic sensor may be subjected to a test action, the test action comprising at least an impulse action or an action in the frequency range to move the seismic sensor; record the response of the seismic sensor to the test action; process the response to obtain a transfer function; and store the transfer function for use by the data processing system when generating the inverse filter. In embodiments of the first or second methods, when a test action is applied, a seismic sensor can be attached to the movable structure; and act on the movable structure by impulse movement or movement in the frequency range. Embodiments may further include when acquiring seismic data: extracting, from the memory for the transfer functions of the seismic data recording unit, the transfer function; and formatting the transfer function for transmission to the data processing system in parallel with the seismic data; or in seismic data acquisition, comparing a sensor transfer function generated during production testing with a sensor transfer function generated during on-site testing; generating a notification signal based on differences between a sensor transfer function generated during production testing and a sensor transfer function generated during field testing when these differences exceed a predetermined level. Embodiments may also include, during seismic data processing by the seismic data processing system, generating a model transfer function that is an average of sensor transfer functions over a plurality of movable sensors. CLAIM 1. A system for recording and processing seismic data, containing a) a seismic data acquisition unit including a data storage device and a second storage device configured to store signals generated by a seismic sensor connected to the seismic data acquisition unit; b) a data retrieval unit configured to extract from the seismic data acquisition unit the signals stored in the data storage device and format the signals for transmission to the seismic data processing system; c) a sensor testing device, configured to apply, using a pulse generator, a test action with a given waveform to the seismic sensor during testing at the installation site; recording the response of the seismic sensor to the test action based on the movement of the seismic sensor responsive to the test action; - 12 041200 determining the transfer function of the sensor for the seismic sensor, reflecting the response of the seismic sensor to the test action with a given waveform; and storing in the memory device of the seismic data recording unit the transfer function of the sensor, and the transfer function of the sensor is used to generate an inverse filter, which, when applied to the signals, changes the parameters of the signals, bringing them in line with the signals generated by the seismic sensor having an exemplary transfer function, correlating with known accuracy, d) a seismic data processing system configured to receive signals formatted by the data extraction node; identifying the seismic sensor connected to the seismic data acquisition unit that generated the signals; extracting a sensor transfer function corresponding to the seismic sensor; generating based on the transfer function of the sensor and the exemplary transfer function of the inverse filter; and applying an inverse filter to the signals. 2. The system of claim 1, wherein the seismic data processing system is configured to generate a reference transfer function determined as an average of the sensor transfer functions of a plurality of seismic sensors. 3. The system according to any one of the preceding claims, wherein the test action includes an impulse or multi-frequency action to move the seismic sensor. 4. The system according to any one of the preceding claims, wherein the sensor test device is configured to compare a sensor transfer function for a seismic sensor generated during production testing with a sensor transfer function for a seismic sensor generated during on-site testing; and generating a notification signal based on differences between a seismic sensor sensor transfer function generated during production testing and a seismic sensor sensor transfer function generated during on-site testing when the differences exceed a predetermined level. 5. The system according to any one of the preceding claims, wherein the sensor comprises at least a piezoelectric crystal or a seismograph or an accelerometer. 6. The system according to any one of the preceding paragraphs, in which the node data extraction is configured to extract the transfer function of the sensor from the storage device for data storage; and formatting the transducer transfer function for transmission to the seismic data processing system in conjunction with the signals. 7. The seismic data processing method carried out by the seismic data processing system of claim 1, wherein receiving signals representing seismic data recorded at a remote site; receiving, together with said signals, an identification code of the seismic sensor through which the signals were received; extracting a sensor transfer function corresponding to this seismic sensor and reflecting the response of the seismic sensor to a test action with a given mode shape, said response being based on the movement of the seismic sensor responding to the test action; generating, based on the sensor transfer function and the exemplary transfer function, an inverse filter which, when applied to the signals, modifies the signal parameters to match those generated by a seismic sensor having an exemplary transfer function related to a known accuracy; and applying an inverse filter to the signals to bring the parameters of the signals in line with the exemplary transfer function. 8. The method of claim 7, further comprising storing the sensor transfer function in a data storage device of the seismic data recorder connected to the seismic sensor before placing the seismic data recorder at the seismic survey site; after using the seismic data recorder to record the seismic data, retrieving the signals stored in the data storage device of the seismic data recorder; and format the signals for transmission to a remote data processing system. 9. The method according to claim 7 or 8, further comprising subjecting, using a pulse generator, a test action to a seismic sensor during production or on-site testing, the test action comprising at least an impulse action or an action in the frequency range for movement seismic sensor; - 13 041200 record the response of the seismic sensor to the test impact; and storing a transfer function of the sensor for use by the remote data processing system when generating an inverse filter. 10. The method of claim 9, further comprising: comparing a sensor transfer function for a seismic sensor generated during production testing with a sensor transfer function for a seismic sensor generated during on-site testing; and generating a notification signal based on differences between a seismic sensor sensor transfer function generated during production testing and a seismic sensor sensor transfer function generated during on-site testing when these differences exceed a predetermined level. 11. A method according to any one of claims 7-10, further comprising generating a reference transfer function determined as the average of the sensor transfer functions of a plurality of seismic sensors. 12. The method according to claim 7, which further extracts the transfer function of the sensor from the storage device for the transfer function of the seismic data recorder; and formatting the transfer function of the sensor for transmission to the remote data processing system in combination with the signals. 13. A method for processing seismic data using the system of claim 1, wherein during production testing of a seismic sensor to be used for seismic data acquisition, subjecting the seismic sensor to a predetermined waveform test during field testing using a pulse shaper. installations; recording the response of the seismic sensor to the test impact based on the movement of the seismic sensor responsive to the test impact; determine the transfer function of the sensor for the seismic sensor, while the transfer function of the sensor reflects the response of the seismic sensor to the test action with a given waveform; storing a sensor transfer function for use by the seismic data processing system when generating an inverse filter; in the seismic data acquisition process, seismic data is acquired by the seismic sensor; retrieving seismic data from a seismic data acquisition unit coupled to the seismic sensor; formatting the seismic data for transmission to a seismic data processing system located remotely from the seismic data acquisition unit by providing a seismic sensor identification code for transmission with the seismic data; during processing of the seismic data by the seismic data processing system, extracting a sensor transfer function using a seismic sensor identification code; generating, based on the sensor transfer function and the reference transfer function, an inverse filter that, when applied to the seismic data, modifies the parameters of the seismic data to match seismic data produced by a seismic sensor having a reference transfer function related to a known accuracy; applying an inverse filter to the seismic data to match the parameters of the seismic data with the seismic data produced by the seismic sensor having the exemplary transfer function. 14. The method of claim 13, wherein, when the sensor transfer function is stored, it is stored in a data storage device of a seismic data recorder connected to the seismic sensor, or it is stored in a database accessible to the seismic data processing system. 15. The method of claim 13 or 14, wherein upon obtaining the sensor transfer function, storing the sensor transfer function for use by the seismic data processing system in generating the inverse filter. 16. The method according to claim 15, in which when applying the test impact attach a seismic sensor to the movable structure; and act on the movable structure by impulse movement or movement in the frequency range. 17. The method according to claim 13, in which additionally when registering seismic data is extracted, from the storage device for the transfer functions of the seismic data recording unit, the transfer function of the sensor; and formatting the transfer function of the sensor for transmission to the data processing system in combination with the seismic data; or -