“Dual-complex areas,” characterized by drastic surface undulations, strong near-surface heterogeneity, and complex deep structures, pose significant challenges to seismic exploration data quality and imaging. This study takes the typical dual-complexity area in the southwestern Tarim Basin as an example to systematically explore the application of forward modeling technology in optimizing seismic data acquisition, focusing on geological characteristics such as thick loess layer coverage, drastic lateral variations in near-surface low-velocity zones, and deep thrust-nappe structures. Through wave equation-based forward simulation, the control mechanisms of abrupt surface topography and near-surface low-velocity zone structures on wavefield energy were revealed, clarifying the origin of strip-shaped energy distribution in loess-covered areas. Combined with seismic wave illumination technology, the study quantitatively demonstrates the illumination capability of a wide-azimuth observation system for thrust nappe structures and deep fault blocks, while optimizing imaging in shadow zones through reverse illumination. Finite element simulations further validated the effectiveness of a three-stage delayed excitation scheme in thick loess regions, confirming its effectiveness in enhancing downward-propagating energy and suppressing source-generated noise. The results demonstrate that forward modeling technology can quantitatively characterize seismic wave propagation in dual-complex areas, providing a scientific basis for optimizing observation system design and Shooting parameters, thereby enhancing seismic data quality.

The surface and underground conditions of the mountainous areas in Sichuan are extremely complex, which causes low signal-to-noise ratio of seismic data, poor imaging quality of seismic profiles and great difficulty in acquisition construction. In response to these problems, continuous efforts have been made to solve the bottleneck problem, forming a series of supporting technologies and software modules for complex mountain high-density seismic acquisition in recent years. First, the landform risk identification and hierarchical evaluation technology utilizes bidirectional intersection slope and relief amplitude to quantitatively calculate and classify terrain hazard into four levels, providing a data foundation for risk control in acquisition construction. Second, the demonstration technology of acquisition construction plans utilizes automatically quantitative evaluation of construction plans under multiple constraints to quickly seek optimization plan with high efficiency, low investment, and easy execution. Third, the intelligent deployment technology of shot points in complex mountainous utilizes intelligent extraction of obstacles and automatic avoidance of shot points, ensuring safety distance for shooting while also considering the uniformity of spatial sampling. Fourth, the intelligent detection technology for quality control videos of key construction nodes is based on computer vision analysis, which efficiently and intelligently monitors construction safety, evaluates the quality of seismic acquisition drilling and placing explosives. Fifth, the automatic evaluation technology for field seismic data acquired in mountainous regions ensures high-quality acquisition of seismic data through real-time monitoring of single shot data and three-level automatic quality evaluation. Through the application of the above technologies and software, the quality of seismic data in complex mountainous areas of Sichuan has been effectively improved, construction risks have been effectively controlled, and the production efficiency has been greatly improved.

Acquisition technology of shale gas seismic exploration in complex mountainous areas can solve a series of problems faced by shale gas seismic exploration, such as complex surface environment, strong underground heterogeneity, rapid lithological change and deep exploration horizon. Starting from the four key links of observation system design, excitation, reception and quality monitoring of shale gas seismic exploration and acquisition, targeted analysis, research and practice have been carried out, and a series of wide-azimuth and high-density 3D seismic exploration and acquisition techniques and methods suitable for complex mountain shale gas have been gradually formed. That is, observation system design demonstration based on "double complex" 3D model and remote sensing technology, geographic information system, shot point optimization, dynamic observation and data quality intelligent evaluation technology. The above technical methods have been used in the shale gas exploration project in southern marine mountains to obtain high-quality seismic data. Practice has proved that this method is feasible. It provides a reference for the subsequent research of target seismic exploration acquisition technology.

Cost, quality and efficiency are important objectives of 2D/3D seismic exploration for oil and gas. Sichuan Basin is densely populated, with a large number of cities and towns accompanied with frequent industrial production activities, which bring great challenges to seismic exploration. For the vibration generated by large-scale engineering activities, the dynamic and kinematic characteristics of induced seismic waves are similar to those of seismic waves during exploration, which are difficult to be completely eliminated by de-noising. It is not only seriously affects the quality of seismic data, sometimes causes seismic recording to be nonconforming data. Aim to hundreds to thousands of square kilometers exploration area, it is extremely important for the acquisition quality and efficiency of seismic exploration by quickly locating and identify the interference to negotiate stopping. Based on the dynamics and kinematics characteristics of seismic wave, this paper establishes a source location-velocity joint inversion method to quickly locate the interference both in and outside of the seismic exploration area. Through the location precision test of the active seismic, the location precision can reach to 10 m along the direction when the observation lines perpendicular to the source. For interference far away to the seismic exploration area, it contributes to greatly reduce the searching zone and the equivalent velocity also contributes to the classification of interference. Theoretical and actual data tests prove that it is effective to provide important technical support for identify the interference and improve the quality and efficiency of 2D/3D seismic exploration.

The practice of exploration and production has proved that explosives are excited in different surrounding rocks and the seismic wavelets collected have different characteristics. In this paper, by establishing a numerical model of the explosion in the well, using finite element analysis technology for numerical simulation, the simulation calculated the stress structure in the near-source area of the earthquake excitation, and extracted the seismic wavelet. The results show that the simulation seismic wavelet characteristics of different thin interbedded sand and mudstone structures have changed significantly. Through excitation simulation, the amplitude and spectrum information of seismic wavelets can be compared and analyzed, and the excitation parameters can be optimized.

In 2022, a 3D3C seismic exploration was conducted by CNPC for tight sand reservoir in Sichuan basin of western China, in difficult operating conditions, which delivered a high density, full azimuth, 3-component dataset. Keys to success were optimized acquisition geometry and precise testing work ahead of field operations, and the ability to effectively manage a complex project with many professional service groups involved. Data quality was excellent despite multiple source types, less than ideal operating conditions (weather) and significant disadvantage complications, such as rivers, reclaimed land, and production infrastructure. Very prudent processing was applied to the dataset in order to optimize resolution and retain robust amplitude and azimuthal information. In addition to conventional full stack seismic attributes, AVO (Amplitude with Offset) and AVOAz (AVO with Azimuth) attributes, and seismic inversion volumes have been generated and analyzed. Optimizing the image and attribute quality is a result of sustained continuity on the project from acquisition through processing to analysis and interpretation.

通过VSP、合成记录对地震剖面进行地质层位标定,是常规地震资料解释的重要环节,且已有成熟的方法和标准;对单炮记录的层位标定方法尚属空白.在地震数据采集现场,通常采用"相面法"分析评价单炮记录质量,但对单炮记录上反射层同向轴对应的地质层位并不清楚,从而影响对单炮记录质量的科学合理评价.本文通过建立"埋时Tou图、地质层位、地形、炮点坐标"四维地震数据体,应用"地震单炮记录地质层位智能快速标定方法",即依据观测系统进行地震采集,每放一炮,计算机自动输出带地质层位的单炮记录,有助于分析目的层的反射能量和信噪比,实时监控单炮记录质量,从而确保采集到高质量地震数据.

Sichuan Basin is rich in natural gas resources and is the basin with the most potential for natural gas exploration and development in China. The problems of low signal-to-noise ratio and poor imaging quality of seismic data in the eastern high and steep tectonic area of Sichuan basin have brought great challenges to the seismic exploration in this area. The outcrop lithology in this area is mainly limestone. Due to rapid dispersion of seismic wave energy excited in the rigid formations, effective down-transmitting energy of seismic waves is insufficient, resulting in a low signal-to-noise ratio of seismic raw data. Starting from the cavity excitation theory, we select parameters in the cavity excitation method. By reducing the initial pressure of the explosion and prolonging the action time, the conversion rate of excitation energy into effective elastic wave energy is improved, and the signal-to-noise ratio of seismic data in the limestone area is effectively enhanced.

页岩气藏高效开发依赖于高精度三维地震资料,而覆盖密度是决定三维地震资料品质和投资成本的关键参数.针对四川盆地泸州区块海相页岩气三维地震资料,在确保对比因素单一性的前提下,通过抽炮排列将覆盖密度由原始的52.5×104道/km2逐步退化为6种不同覆盖密度的三维观测系统,并对其叠前偏移成果进行定性、定量评价以论证和优选覆盖密度参数;同时对比了相同覆盖密度下大面元高覆盖和小面元低覆盖两种观测系统的优劣.结果表明:①叠前偏移成像效果随着覆盖密度的增大而逐渐改善,信噪比也随之提高,振幅、频率、信噪比的定量评价显示泸州区块页岩气三维地震观测系统覆盖密度选择在42.0×104道/km2较为合适;②在相同的覆盖密度下,大面元高覆盖观测系统能够提高地震资料的信噪比,有利于复杂构造的成像,而小面元低覆盖观测系统则有更高的纵横向分辨率.结论认为:开展覆盖密度参数退化试验,综合定性和定量评价结果能够获得一个兼顾成像效果和经济性的覆盖密度参数;在覆盖密度确定的前提下,对于信噪比较高地区,可以选择小面元低覆盖观测系统,而对于信噪比较低地区,可以选择大面元高覆盖观测系统.

当地腹存在高速屏蔽层时,高速层对地震波向下传播及深部地层反射信息向上传播都起到屏蔽作用,使得深部地层的反射信息难以获取.地震勘探中,当炮检距增大到一定程度或入射角到达临界角时,可接收到一种特殊的波——广角反射波,对其处理成像可以提高深层反射能量,从而提高地震资料品质.针对四川盆地震旦系等超深储层,开展了广角反射地震资料采集与处理的研究与应用.结果表明:①四川盆地寒武系、震旦系超深地层,是可以获得较好的广角反射资料的,采集中最大偏移距应在20 km左右,且要有足够的覆盖次数;②广角反射的偏移距大,受球面扩散和地层衰减的影响严重,在采集中应考虑更大激发能量;③广角反射资料的去噪处理和动校正是影响成像的关键技术,通过循序渐进的逐步去噪、分频去噪、多域去噪,可以得到高信噪比资料,利用各项异性+4次高阶动校正方法可以较好地解决动校正问题;④广角反射波与正常地震反射波存在相位变化,且相位随入射角的变化而变化,二者的有机叠加还需进行精细的相位校正.

As an important method for the reduction of multiresolution of predicting reservoirs, multi-component acquisition 3D/3C exploration on land provides a variety of valuable information about the subsurface different from that provided by conventional P-wave acquisition. Interestingly, the business objectives that motivate converted wave exploration are often derived from problems with data from conventional compressional exploration. The data prove inadequate at providing needed information because of local conditions that are problematic for the PP method. The converted wave option is investigated as a possible means to overcome those difficult problems or deficiency in PP data. The middle of Sichuan basin in china had been producing for more than 60 years. Currently, the unconventional resources of the Xujiahe Formation were the ones that are most actively explored and studied. Cores analysis, well logging and microscopic identification on thin section showed three types of reservoirs: porous, fractured-porous and fractured. Some key problems, such as gas-water identification and fracture distribution, were difficult to solve by conventional PP wave exploration. A 3D-3C seismic survey with dynamite source had been performed in the study region, taking advantage of combing P-wave and converted wave exploration. The results showed that the lithological reservoir could be characterized effectively by the combined exploration methodology. Presentation Date: Tuesday, September 17, 2019 Session Start Time: 9:20 AM Presentation Time: 9:45 AM Location: Poster Station 1 Presentation Type: Poster

PreviousNext No AccessSEG 2019 Workshop: 2nd SEG Foothill Exploration Workshop, Chengdu, China, 12–14 April 2019A case study of joint 3C3D and 3DVSP seismic exploration in carbonate area in Sichuan basinAuthors: Shuqin Li*Xiaoyang WangLiu YangFurong WuShanzheng HuMin LiJiangli ChenLongjiang JingShuqin Li*BGP of CNPCSearch for more papers by this author, Xiaoyang WangBGP of CNPCSearch for more papers by this author, Liu YangBGP of CNPCSearch for more papers by this author, Furong WuBGP of CNPCSearch for more papers by this author, Shanzheng HuBGP of CNPCSearch for more papers by this author, Min LiBGP of CNPCSearch for more papers by this author, Jiangli ChenBGP of CNPCSearch for more papers by this author, and Longjiang JingBGP of CNPCSearch for more papers by this authorhttps://doi.org/10.1190/FEW2019-14.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract As a new seismic exploration method combining surface seismic and 3D Vertical Seismic Profiling (VSP) in wells, joint 3D and VSP technique realizes the combination of surface and down-hole seismic acquisition, and can achieve the purpose of synchronous acquisition and synchronous processing, thus improves the imaging accuracy of the exploration area. A joint 3C3D surface seismic and 3DVSP exploration project has been carried out in the carbonate area in Sichuan Basin. The results show that the joint multi-component 3D and VSP technique effectively improved the exploration accuracy in the exploration area. The project realized the synchronous acquisition of 3C3D surface and down hole in mountainous area, and the acquisition cost is reduced by 33.7% compared to separate acquisitions. This project is the first joint 3C3D surface and down-hole acquisition project targeting at the middle-deep carbonate formations in China. Keywords: 3D, VSP, acquisitionPermalink: https://doi.org/10.1190/FEW2019-14.1FiguresReferencesRelatedDetails SEG 2019 Workshop: 2nd SEG Foothill Exploration Workshop, Chengdu, China, 12–14 April 2019ISSN (online):2159-6832Copyright: 2019 Pages: 79 publication data© 2019 Published in electronic format with permission by the Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 28 Aug 2019 CITATION INFORMATION Shuqin Li*, Xiaoyang Wang, Liu Yang, Furong Wu, Shanzheng Hu, Min Li, Jiangli Chen, and Longjiang Jing, (2019), "A case study of joint 3C3D and 3DVSP seismic exploration in carbonate area in Sichuan basin," SEG Global Meeting Abstracts : 51-54. https://doi.org/10.1190/FEW2019-14.1 Plain-Language Summary Keywords3DVSPacquisitionPDF DownloadLoading ...

PreviousNext No AccessSEG Technical Program Expanded Abstracts 2015Geometry optimization method based on visibility analysis: a case studyAuthors: Shanzheng HuYanXiong ChenShuQin LiLongJiang JingZhongLin CaoAiPing ChenXiaoBin ZhangShanzheng HuSichuan Geophysical Company of CNPC Chuanqing Drilling Engineering Company LimitedSearch for more papers by this author, YanXiong ChenSichuan Geophysical Company of CNPC Chuanqing Drilling Engineering Company LimitedSearch for more papers by this author, ShuQin LiSichuan Geophysical Company of CNPC Chuanqing Drilling Engineering Company LimitedSearch for more papers by this author, LongJiang JingSichuan Geophysical Company of CNPC Chuanqing Drilling Engineering Company LimitedSearch for more papers by this author, ZhongLin CaoSichuan Geophysical Company of CNPC Chuanqing Drilling Engineering Company LimitedSearch for more papers by this author, AiPing ChenSichuan Geophysical Company of CNPC Chuanqing Drilling Engineering Company LimitedSearch for more papers by this author, and XiaoBin ZhangSichuan Geophysical Company of CNPC Chuanqing Drilling Engineering Company LimitedSearch for more papers by this authorhttps://doi.org/10.1190/segam2015-5825271.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract Geometry playing a crucial role in the integrity of the seismic wave-field, and geometric parameters are therefore considered key in seismic image processing and resolution. In spite of optimization survey, the image of the target in this case study is affected by rough surface topography and poor excitation condition in the overburden. In this paper, we present a methodology of seismic visibility analysis which is applied to 2D target-oriented acquisition design for extracting optimal acquisition parameters. An analysis work flow based on a shot visibility using the full-acquisition aperture is used to guide selection of optimal 2D acquisition parameters. The primary objective of this case study is to evaluate alternative acquisition geometries for imaging a target under an unsatisfactory shot condition. The visibility studies support reasonable offset acquisition geometries to provide imaging uplift for the target under the seismic obscured zone. Keywords: optimization, survey design, wave equation, acquisition, 2DPermalink: https://doi.org/10.1190/segam2015-5825271.1FiguresReferencesRelatedDetails SEG Technical Program Expanded Abstracts 2015ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 2015 Pages: 5634 publication data© 2015 Published in electronic format with permission by the Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 19 Aug 2015 CITATION INFORMATION Shanzheng Hu, YanXiong Chen, ShuQin Li, LongJiang Jing, ZhongLin Cao, AiPing Chen, and XiaoBin Zhang, (2015), "Geometry optimization method based on visibility analysis: a case study," SEG Technical Program Expanded Abstracts : 271-275. https://doi.org/10.1190/segam2015-5825271.1 Plain-Language Summary Keywordsoptimizationsurvey designwave equationacquisition2DPDF DownloadLoading ...

Seismic exploration in the mountainous areas of western Chinese is extremely difficult because of the complexity of the surface and subsurface, which results in shooting difficulties, seismic data with low signal-to-noise ratio, and strong interference. The complexity of the subsurface structure leads to strong scattering of the reflection points; thus, the curved-line acquisition method has been used. However, the actual subsurface structural characteristics have been rarely considered. We propose a design method for irregular acquisition based on common reflection points (CRP) to avoid difficult-to-shoot areas, while considering the structural characteristics and CRP positions and optimizing the surface-receiving line position. We arrange the positions of the receiving points to ensure as little dispersion of subsurface CRP as possible to improve the signal-to-noise ratio of the seismic data. We verify the applicability of the method using actual data from a site in Sichuan Basin. The proposed method apparently solves the problem of seismic data acquisition and facilitates seismic exploration in structurally complex areas.

Complicated mountainous area is characterized for large ups and downs in landform, complicated surface structure and steep subterranean structure. The traditional method for design of observation system uses the level surface and underground level layered homogenous medium as the assumed conditions. This makes the designed observation system unsuitable for seismic data acquisition in such region, causing low signal-noise ratio, poor structural imaging quality and difficult operation for acquisition. The software for design of real surface seismic observation system enables CRP folds to be focused on the target formations, uses remote sensing information to select and adjust line collocation, optimizes shot and receiverpoints, appraises operational safety risks in the work area, and designs the seismic operational routes, thus providing more scientific solutions for mountainous seismic data acquisition. The software was put into application in a number of areas. It lowered the operational difficulty by SO percent, nearly doubled the acquisition efficiency and remarkably raised the data quality, effectively improving the imaging quality of the main position of mountainous steep structure.

该文设计了一种特殊的高码率准循环低密度校验(QC-LDPC)码,其校验矩阵以单位矩阵的循环移位阵为基本单元,与随机构造的LDPC码相比可节省大量存储单元.利用该码校验矩阵的近似下三角特性,一种高效的递推编码方法被提出,它使得该码编码复杂度与码长成线性关系.另外,该文提出一种分析QC-LDPC码二分图中短长度环分布情况的方法,并且给出了相应的不含长为4环QC-LDPC码的构造方法.计算机仿真结果表明,新码不但编码简单,而且具有高纠错能力、低误码平层.

A serial concatenated coding method is presented based on low-density parity-check (LDPC) codes and vertical single-parity-check (VSPC) product codes. By applying the decoded result of LDPC codes instead of the horizontal checks of conventional product codes, the performance of the component SPC product codes can be improved with the reduced complexity. The performance of the new concatenated codes is analyzed. Simulation results show that the proposed concatenated codes significantly outperform LDPC codes alone on AWGN channels and Raleigh fading channels, and the additional decoding complexity is very low. Moreover, the error floors of LDPC codes can be impaired effectively.