What Is Seismic Acquisition?

Seismic data acquisition is the first and most important process in oil and gas seismic exploration engineering. In this process, an essential device is used, that is, the seismic signal receiving and recording system. Conventionally, the device that senses seismic signals is called a geophone, and the device that collects and records seismic signals is called a seismic survey instrument (also called a seismic (recording) instrument), which is the key equipment of seismic instruments. Seismic geophones and seismic survey instruments always need to work together to achieve a complete seismic data acquisition function. That is, geophones and instruments are inseparable in function. From the perspective of the system, and in order to meet the needs of development, the seismic signal sensing and acquisition devices mainly including geophones and seismic survey instruments are collectively referred to as seismic data acquisition systems (referred to as acquisition systems).

Seismic data acquisition parameters mainly involve three aspects, namely excitation parameters, permutation parameters, and reception parameters. The analysis of the excitation parameters includes the determination of the depth of the excitation well; the arrangement parameters include the minimum reception arrangement, the maximum gun offset, the panel size, the reception track distance, and the offset aperture; the reception parameters include the calculation of the reception combination distance and the analysis of the combination characteristics. These parameters are the key to seismic data collection. The choice of good or bad will directly determine whether good original single shot seismic data can be obtained. Therefore, the analysis of acquisition parameters is a very important task, and it must be demonstrated scientifically and systematically in order to obtain the best acquisition parameters.

The main characteristics of the development of seismic survey instruments and their technology are also the general laws of their development and change, mainly as follows:

The strategic position of oil and gas resources in the national economy and people s livelihood determines the importance of seismic exploration work to find oil and gas resources most effectively, which also determines that the seismic exploration instrument has a broad market space, which is the fundamental driving force for the sustainable development of seismic exploration instruments .

Advances in geophysical methods and technologies have proposed goals for the development of seismic exploration instruments. For example, geophysical exploration technology has developed in the direction of high resolution, high signal-to-noise ratio, high fidelity, multi-wave multi-dimensional multi-channel and other technical directions. The direction of low distortion, wide frequency response, high speed, and real-time 10-channel acquisition capability is developing.

The inherent defects of the previous generation of instruments provided space for the improvement and development of the next generation of instruments. For example, the problem of analog light spot recording seismic instruments cannot achieve data sharing and reuse, which is for the development of long-term memory and reproducible seismic data. The tape recorder provided the opportunity for seismic instruments.

The user's pursuit and hope clarified the specific and specific physical characteristics for the development of seismic survey instruments. For example, the user always requires the instrument to be lightweight, durable, stable and inexpensive. The seismic survey instrument strives to be lightweight and sturdy. , Maintenance-free, low power consumption, wide operating temperature range, low cost, etc.

New technology, new materials, and new technologies are the foundation and basis for the development and progress of seismic exploration instruments. All the seismic exploration instruments of each era have tracked and applied the most advanced computer technology, electronic engineering technology, data transmission technology, and signal sensing at that time. Technology, etc., also used the highest quality materials and the most advanced technology at the same time.

The standardization and standardization of global electronics industry manufacturing technology and the personalized development of software technology make the hardware composition of seismic survey instruments more general and simple. At the same time, the characteristics of the system and the core technology are increasingly dependent on the function and application software. performance. In a certain sense, the key technology of seismic survey instruments is the reproduction of the latest technologies such as electronic engineering, computer software, and hardware ^[2]

Seismic instruments are the core equipment for truly recording returned ground seismic signals. They are required to not only lose useful seismic signals, but also to fully sample the interference signals to facilitate suppression in the field or indoors.

For low-permeability layers, deep layers, deep oceans, unconventional exploration targets, the core equipment of seismic exploration is required to have the characteristics of avenue number, large dynamic range, wide frequency response, and high data collection efficiency. Therefore, seismic instruments must be flexible, adaptable, and manageable. The ability to operate large amounts of data over channels, and the detector has high-fidelity, large dynamic range, and wide-band response performance. The excitation equipment can be environmentally friendly and meet the requirements of efficient acquisition and wide-band excitation ^[3]

Seismic instruments have been continuously developed along with the development of the basic electronics industry. They have undergone seven generations of development, including light spot, analog, digital, early telemetry, late telemetry, full digital recording, and node to real-time wireless Wandao network telemetry.

(1) The first generation was an analog light spot recording seismic instrument. The 51-type instrument is used as a representative, and light-point light-sensitive photo paper records are used as the original data for seismic exploration. The dynamic range of the signal is small, the frequency band is narrow, and the number of receiving channels is small.

(2) The second generation is an analog tape recording seismic instrument. Take CGG59 as a representative and tape as the medium. The first and second phases mentioned above represent the simulated earthquake phase.

(3) The third generation is a digital magnetic tape recording seismic instrument. Take DFS-V and SN338 as representatives, adopting pre-amplification, instantaneous floating-point amplification and A / D conversion technology to realize the transformation from analog recording to digital recording. There has been a significant increase. This stage represents the digital stage.

(4) The fourth generation is a telemetry digital seismic instrument. SN368, OPSEIS5586 and other representatives are used to realize the serial transmission of seismic trace information on cables in the form of digital signals. The host is fully simplified. The system's acquisition capability and anti-interference capability have been significantly improved, and the band capacity has reached 1000 channels. This stage promoted the advent of 3D earthquakes.

(5) The fifth generation is a multi-channel telemetry digital seismic instrument. Represented by SN388, ARIES, BOX, SYSTEM II, etc., the integrated instantaneous floating-point amplifier and 16-bit A / D converter are replaced by the integrated 24-bit A / D converter. It has been greatly improved, and the track capacity has reached 5000.

(6) The sixth generation is an all-digital seismic instrument. Represented by the original I / O company's VECTORSEIS and Sercel's DSU series, the acceleration digital detector with MEMS technology as the core enables the dynamic range of the entire receiving system to be greater than or equal to aB

Figure 1.Comparison of main performance indicators of previous seismic instruments

, Realizing full digital real-time collection of more than 10,000 channels.

(7) The field operation method of the seventh-generation seismic instrument is more flexible, and it is suitable for the operation of more than 100,000 roads. It is represented by wired U system, real-time wireless instrument RT2, node instrument UNITE, HWAK, etc. The field deployment is flexible, and it has strong networked data management capabilities, which promotes the popularization and application of "two-width and one-high" seismic acquisition technology and efficient acquisition technology. At present, the seventh-generation seismic instruments launched by various manufacturers have different technical characteristics and applicable capabilities. There are generally three types of systems, namely wired transmission systems, node systems, and real-time wireless transmission systems.

The main performance of historical seismic instruments is shown in Figure 1 ^[3] .