On electro-acoustic characteristics of a marine broadband sparker for seismic exploration

The construction of major marine infrastructure projects and the exploration and development of deep-sea mineral resources require fine imaging of seabed strata and structures.The highresolution marine seismic exploration based on a high broadband sparker source is an important approach to reveal seabed stratum and reservoir structure,and identify geohazard.To optimize the performance of sparker seismic source,we investigated the electro-acoustic characteristics of spark discharge under conditions of different charging voltages and electrode numbers.Results show that the sound source level increased with the increase of the charging voltage,whereas the main frequency decreased when the charging voltage increases.In addition,it was found that the charging capacitance had more obvious influence on the main frequency than the sound source level did.Although the load energy decreased with increasing electrode number,the sound source level still increased but the main frequency decreased.Meanwhile,the primary to bubble(P/B)ratio increased with the increase of the electrode number.To gain a deeper insight into the electro-acoustic characteristics,we investigate the relationship between sound source level and power peak,from which a good correlation was observed.A more practical statistical analysis on the rise rate of current was processed,and a perfect logarithmic function was derived.Furthermore,we found that the main frequency was most possibly subjected to the electrical energy,especially the charging energy per electrode.The results indicate that the charging energy per electrode less than 10 J could increase the main frequency to above 300 Hz.At last,the main frequency could be reduced to 20 Hz when the charging energy of a single-electrode discharge was enhanced to over 4 kJ.This study shall be helpful in developing a sparker seismic source and improving the performance for marine engineering exploration and geohazard assessment.

Accurate Source-Receiver Positioning Method for a High-Resolution Deep-Towed Multichannel Seismic Exploration System

The near-seabed multichannel seismic exploration systems have yielded remarkable successes in marine geological disaster assessment,marine gas hydrate investigation,and deep-sea mineral exploration owing to their high vertical and horizontal resolution.However,the quality of deep-towed seismic imaging hinges on accurate source-receiver positioning information.In light of existing technical problems,we propose a novel array geometry inversion method tailored for high-resolution deep-towed multichannel seismic exploration systems.This method is independent of the attitude and depth sensors along a deep-towed seismic streamer,accounting for variations in seawater velocity and seabed slope angle.Our approach decomposes the towed line array into multiline segments and characterizes its geometric shape using the line segment distance and pitch angle.Introducing optimization parameters for seawater velocity and seabed slope angle,we establish an objective function based on the model,yielding results that align with objective reality.Employing the particle swarm optimization algorithm enables synchronous acquisition of optimized inversion results for array geometry and seawater velocity.Experimental validation using theoretical models and practical data verifies that our approach effectively enhances source and receiver positioning inversion accuracy.The algorithm exhibits robust stability and reliability,addressing uncertainties in seismic traveltime picking and complex seabed topography conditions.

Review of Artificial Intelligence for Oil and Gas Exploration: Convolutional Neural Network Approaches and the U-Net 3D Model

Deep learning, especially through convolutional neural networks (CNN) such as the U-Net 3D model, has revolutionized fault identification from seismic data, representing a significant leap over traditional methods. Our review traces the evolution of CNN, emphasizing the adaptation and capabilities of the U-Net 3D model in automating seismic fault delineation with unprecedented accuracy. We find: 1) The transition from basic neural networks to sophisticated CNN has enabled remarkable advancements in image recognition, which are directly applicable to analyzing seismic data. The U-Net 3D model, with its innovative architecture, exemplifies this progress by providing a method for detailed and accurate fault detection with reduced manual interpretation bias. 2) The U-Net 3D model has demonstrated its superiority over traditional fault identification methods in several key areas: it has enhanced interpretation accuracy, increased operational efficiency, and reduced the subjectivity of manual methods. 3) Despite these achievements, challenges such as the need for effective data preprocessing, acquisition of high-quality annotated datasets, and achieving model generalization across different geological conditions remain. Future research should therefore focus on developing more complex network architectures and innovative training strategies to refine fault identification performance further. Our findings confirm the transformative potential of deep learning, particularly CNN like the U-Net 3D model, in geosciences, advocating for its broader integration to revolutionize geological exploration and seismic analysis.

Two stages power generation test of the hot dry rock exploration and production demonstration project in the Gonghe Basin,northeastern Qinghai-Tibet plateau,China

The Hot Dry Rock(HDR)is considered as a clean and renewable energy,poised to significantly contribute to the global energy decarbonization agenda.Many HDR projects worldwide have accumulated valuable experience in efficient drilling and completion,reservoir construction,and fracture simulation.In 2019,China Geological Survey(CGS)initiated a demonstration project of HDR exploration and production in the Gonghe Basin,aiming to overcome the setbacks faced by HDR projects.Over the ensuing four years,the Gonghe HDR project achieved the first power generation in 2021,followed by the second power generation test in 2022.After establishing the primary well group in the initial phase,two directional wells and one branch well were drilled.Noteworthy progress was made in successfully constructing the targeted reservoir,realizing inter-well connectivity,power generation and grid connection,implementing of the real-time micro-seismic monitoring.A closed-loop technical validation of the HDR exploration and production was completed.However,many technical challenges remain in the process of HDR industrialization,such as reservoir fracture network characterization,efficient drilling and completion,multiple fracturing treatment,continuous injection and production,as well as mitigation of induced seismicity and numerical simulation technology.

Field Test Summary of Two Kinds of Electronic Detonator for Seismic Exploration

Electronic detonators are widely used because of their advantages in real-time supervision of the whole life cycle (Zang, 2022). Due to the high requirements of the time difference synchronization between the electronic initiation system and the seismic wave recording system, the Electronic detonator has not been widely used for Seismic exploration (Yang, 2020). This paper expounds the systematic and scientific test method from the aspects of the comprehensive performance of electronic detonators for exploration, the compatibility between the electronic detonator initiation system and the geophysical blasting machine system, the constraints of the geophysical explosion-related collaborative Danling managment cloud platform, and the quality of data collected by electronic detonator blasting in wells., and based on the analysis of the test results, the problems that need to be improved in the application of electronic detonators and detonation systems in the large-scale production of geophysical prospecting industry are put forward. .

Application Results of 3-D Seismic Exploration Technology in Coal Mines

This paper briefly introduces the development and present situation of China's coal seismic exploration. It focuses on analyzing the important functions of 3-D seismic exploration technology in the designing and production of coal mines, and also the results of its application.

Active Fault Exploration and Seismic Hazard Assessment in Fuzhou City

It has been proven by a number of earthquake case studies that an active fault-induced earthquake beneath a city can be devastating. It is an urgent issue for seismic hazard reduction to explore the distribution of active faults beneath the urban area and identify the seismic source and the risks underneath. As a pilot project of active fault exploration in China, the project, entitled “Active fault exploration and seismic hazard assessment in Fuzhou City”, started in early 2001 and passed the check before acceptance of China Earthquake Administration in August 2004. The project was aimed to solve a series of scientific issues such as fault location, dating, movement nature, deep settings, seismic risk and hazard, preparedness of earthquake prevention and disaster reduction, and etc. by means of exploration and assessment of active faults by stages, i.e., the preliminary survey and identification of active faults in target area, the exploration of deep seismotectonic settings, the risk evaluation of active seismogenic faults, the construction of geographic information system of active faults, and so on. A lot of exploration methods were employed in the project such as the detection of absorbed mercury, free mercury and radon in soil, the geological radar, multi-channel DC electrical method, tsansient electromagnetic method, shallow seismic refraction and reflection, effect contrast of explored sources, and various sounding experiments, to establish the buried Quaternary standard section of the Fuzhou basin. By summing up, the above explorations and experiments have achieved the following results and conclusions ：

A Case History of Secondary 3D Seismic Exploration in the Liaohe Basin: An Example from the Rongshengpu–Qianjin Area

The working area is located in the industrially developed region of Rongshengpu-Qianjin, where a surface water system is developed, surface-layer lithology is complicated, and various kinds of hydrocarbon traps are buried at depth. The seismic data acquired previously couldn＇t be interpreted due to the complex surface and geological conditions. Taking secondary 3D seismic from the Rongshengpu-Qianjin area as an example, this paper describes a set of techniques designed to overcome these difficulties and improve the quality of seismic data. The applied techniques included flexible acquisition geometry, low-noise receiver conditions, quantitative quality control, and so on.

China Seismic Experimental Site(CSES): Challenges of Deep Earth Exploration and Practice(DEEP)

Since May 2018,the planning,construction and functioning of China Seismic Experimental Site(CSES)has attracted much attention in earthquake science(CSES,2020 a,b,c;Wu,2020;Li et al.,2021).Different from traditional earthquake prediction experiment projects,such as the Parkfield earthquake prediction experiment(Roeloffs,2000).

Seismic fine imaging and its significance for natural gas hydrate exploration in the Shenhu Test Area, South China Sea

Shenhu area in South China Sea includes extensive collapse and diapir structures,forming high-angle faults and vertical fracture system,which functions as a fluid migration channel for gas hydrate formation.In order to improve the imaging precision of natural gas hydrate in this area,especially for fault and fracture structures,the present work propose a velocity stitching technique that accelerates effectively the convergence of the shallow seafloor,indicating seafloor horizon interpretation and the initial interval velocity for model building.In the depth domain,pre-stack depth migration and residual curvature are built into the model based on high-precision grid-tomography velocity inversion,after several rounds of tomographic iterations,as the residual velocity field converges gradually.Test results of the Shenhu area show that the imaging precision of the fault zone is obviously improved,the fracture structures appear more clearly,the wave group characteristics significantly change for the better and the signal-to-noise ratio and resolution are improved.These improvements provide the necessary basis for the new reservoir model and field drilling risk tips,help optimize the favorable drilling target,and are crucial for the natural gas resource potential evaluation.

Preface to the Special Issue on Advances in Seismic Exploration and Monitoring with Active Sources in China

Analyzing the information carriede by seismic waves is a major means for human beings to have an insight into the structure of the earth’s interior,and by using artificial seismic sources to excite seismic waves,we can obtain high-resolution images for the crustal and smaller scale medium.Artificial seismic exploration methods have been widely applied to fields such as

Method of high-density seismic imaging exploration and application samples

The paper introduces the method of high-density seismic imaging exploration, discusses its features different from conventional shallow seismic reflection wave technique, and illustrates the application effect of the method using three samples of engineering geological explorations on land and in water exploration of underground cavity, location survey of sunk ship and investigation of channel silt depth.

Full wave seismic exploration technology

Reflected wave seismology has the following defects:the acquisition design is based on the assumption of layered media,the signal processing suppresses weak signals such as diffracted wave and scattered wave,and the seismic wave band after the image processing is narrow.They limit the full utilization of broadband raw data.The concept of full wave seismic exploration is redefined based on the idea of balanced utilization of reflected wave,diffracted wave and scattered wave information,its characteristics and adaptive conditions are clarified.A set of key technologies suitable for full wave seismic exploration are put forward.During seismic acquisition period,it is necessary to adopt multi geometry,i.e.embed small bin,small offset and small channel interval data in conventional geometry.By discretizing of common midpoint(CMP)gathers,small offset with high coverage,the weak signals such as diffracted wave and scattered wave in the raw seismic data can be enhanced.During seismic processing,the signal and noise in the original seismic data need to be redefined at first.The effective signals of seismic data are enhanced through merging of multi-geometry data.By means of differential application of data with different bin sizes and different arrangement modes,different regimes of seismic waves can be effectively decomposed and imaged separately.During seismic interpretation stage,making the most of the full wave seismic data,and adopting well-seismic calibration on multi-scale and multi-dimension,the seismic attributes in multi-regimes and multi-domains are interpreted to reveal interior information of complex lithology bodies and improve the lateral resolution of non-layered reservoirs.

New Progress in High-Precision and High-Resolution Seismic Exploration Technique in Coal Industry of China

In the past twenty years, the proportion of coal in primary-energy consumption in China is generally between 71.3% and 76.5%. The output of coal was 1.374 billion tons in 1996, and 1.21 tons in 1998, which ranked first in the world. Now coal is mined mainly with mechanization in China, which is planned to reach 80% in major State-owned coal mines in 2000 according to the planning of the government (Li et al., 1998; Tang Dejin, 1998).

Applying Non-Local Means Filter on Seismic Exploration

The seismic reflection method is one of the most important methods in geophysical exploration.There are three stages in a seismic exploration survey:acquisition,processing,and interpretation.This paper focuses on a pre-processing tool,the Non-Local Means(NLM)filter algorithm,which is a powerful technique that can significantly suppress noise in seismic data.However,the domain of the NLM algorithm is the whole dataset and 3D seismic data being very large,often exceeding one terabyte(TB),it is impossible to store all the data in Random Access Memory(RAM).Furthermore,the NLM filter would require a considerably long runtime.These factors make a straightforward implementation of the NLM algorithm on real geophysical exploration data infeasible.This paper redesigned and implemented the NLM filter algorithm to fit the challenges of seismic exploration.The optimized implementation of the NLM filter is capable of processing production-size seismic data on modern clusters and is 87 times faster than the straightforward implementation of NLM.

Application of High-Density Seismic Image in Nondestructive Exploration of Cut-off Cement-Soil Wall in Earth Dam

In order to quickly explore the quality of cut-off wall in dams, a new method of high-density seismic image was adopted and estimated by model and in-situ wall tests.The vibration exciter was employed and several parameters such as hypocentral distance, length of signal record and sampling space in signal collection were determined, which are 8 m, 0.25 ms and 128 ms respectively. Through time and frequency field signal analyses, it is concluded that, the smaller arrival times of reflected longitudinal and surface waves, and the higher their main frequencies, the higher the strength of the wall, vice versa. Accordingly the construction quality of the wall can be evaluated quickly by high-density seismic image.

Inverse gaussian beam stack imaging in 3D crosswell seismic exploration of deviated wells and Its application

In crosswell seismic exploration,the imaging section produced by migration based on a wave equation has a serious arc phenomenon at its edge and a small effective range because of geometrical restrictions.Another imaging section produced by the VSP-CDP stack imaging method employed with ray-tracing theory is amplitude-preserved.However,imaging 3D complex lithological structures accurately with this method is difficult.Therefore,this study proposes inverse Gaussian beam stack imaging in the 3D crosswell seismic exploration of deviated wells on the basis of Gaussian beam ray-tracing theory.By employing Gaussian beam ray-tracing theory in 3D crosswell seismic exploration,we analyzed the energy relationship between seismic wave fields and their effective rays.In imaging,the single-channel seismic wave fi eld data in the common shot point gather are converted into multiple effective wave fields in the common reflection point gather by the inverse Gaussian beam.The process produces a large fold number of intensive reflection points.Selected from the horizontal and vertical directions of the 2D measuring line,the wave fi elds of the eff ective reflection points in the same stack bin are projected onto the 2D measuring line,chosen according to the distribution characteristics of the reflection points,and stacked into an imaging section.The method is applied to X oilfi eld to identify the internal structure of the off shore gas cloud area.The results provided positive support for the inverse Gaussian beam stack imaging of 3D complex lithological structures and proved that technology is a powerful imaging tool for 3D crosswell seismic data processing.

Deep Seismic Exploration in the Taiwan Straits: The HX9 Survey Line Experiment and Preliminary Results

By using an offshore large volume air-gun seismic source, onshore seismic stations( including mobile stations and permanent stations) and ocean bottom seismometers,a deep seismic exploration experiment was carried out for the first time in the Taiwan Straits. Results show that seismic stations can receive seismic signals from the air-gun arrays of the "YANPING Ⅱ"scientific investigation ship from as far as 280 km away.Tens of thousands of high quality seismic data items were obtained successfully and different types of P-wave seismic phases were identified. A one-dimensional crustal structure model of the survey profile HX9 shows that the crustal structure,which is reflected by Pc and Pm P reflection waves from two velocity discontinuities and basement refraction wave( Pg) constitutes the basic characteristic of the crustal structure in this region. The depths of Conrad discontinuity and Moho discontinuity are respectively16. 0km- 17. 5km and 28. 0km- 29. 5km.

Non-PLL high-precision synchronous sampling method among lots of acoustics acquisition channels for underwater multilinear array seismic exploration system

Synchronous sampling is very essential in underwater multilinear array seismic exploration system in which every acquisition node(AN)samples analog signals by its own analog-digital converter(ADC).Aiming at the problems of complex synchronous sampling method and long locking time after varying sampling rate in traditional underwater seismic exploration system,an improved synchronous sampling model based on the master-slave synchronous model and local clock asynchronous drive with non phase locked loop(PLL)is built,and a high-precision synchronous sampling method is proposed,which combines the short-term stability of local asynchronous driving clock with the master-slave synchronous calibration of local sampling clock.Based on the improved synchronous sampling model,the influence of clock stability,transmission delay and phase jitter on synchronous sampling error is analyzed,and a high-precision calibration method of synchronous sampling error based on step-by-step compensation of transmission delay is proposed.The model and method effectively realize the immunity of phase jitter on synchronous sampling error in principle,and compensate the influence of signal transmission delay on synchronous sampling error.At the same time,it greatly reduces the complexity of software and hardware implementation of synchronous sampling,and solves the problem of long locking time after changing the sampling rate in traditional methods.The experimental system of synchronous sampling for dual linear array is built,and the synchronous sampling accuracy is better than 5 ns.

Study on Anti-Disturbance and High-Resolution Shallow Seismic Exploration of Active Faults in Urban Regions

The significance of detection of urban active faults and the general situation concerning detection of urban active faults in the world are briefly introduced. In a brief description of the basic principles of anti-disturbance and high-resolution shallow seismic exploration, the stress is put on the excitation of seismic sources, the performance of digital seismographs, receiving mode and conditions, geometry as well as data acquisition, processing and interpretation in the anti-disturbance and high-resolution shallow seismic exploration of urban active faults. The study indicates that a controlled seismic source with a linear or nonlinear frequency-conversion scanning function and the relevant seismographs must be used in data acquisition, as well as working methods for small group interval, small offset, multi-channel receiving, short-array and high-frequency detectors for receiving are used. Attention should be paid to the application of techniques for static correction of refraction, noise suppressing, high-precision analysis of velocity, wavelet compressing, zero-phasing of wavelet and pre-stacking migration to data processing and interpretation. Finally, some cases of anti-disturbance and high-resolution shallow seismic exploration of urban active faults are present in the paper.