• Volume 37,Issue S2,2015 Table of Contents
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    • >地震工程
    • Wave Localization in a Disordered Periodic Viaduct Undergoing Out-of-plane Vibration

      2015, 37(S2):127-130. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0127

      Abstract (947) HTML (0) PDF 1.09 M (930) Comment (0) Favorites

      Abstract:Wave localization in a disordered periodic viaduct(DPV) undergoing out-of plane vibration is investigated.To this end, each span of the viaduct is simplified as a unit composed of a pier and two longitudinal beams.To investigate the wave localization in the disordered periodic viaduct, first the transfer matrix for the junction connecting two beams and one pier in one span of the viaduct is derived. Based on the transfer matrix for each span of the viaduct, the wave transfer matrix for each span is then constructed. By using the wave transfer matrices and Wolf's algorithm, the Lyapunov exponents for the wave localization in the viaduct can be determined. Using the proposed model, the influences of the pier-height and beam-length disorders on the wave localization are examined. In addition, the interactive effect of the damping in the pier and beam materials and the pier-height and beam-length disorders on the wave localization in a disordered viaduct are analyzed. Numeric results show that when pier-height and beam-length disorders occur, the Lyapunov exponents are almost unaffected by the lower frequency disorders. However, at increasing frequencies, the influences of the pier-height and beam-length disorders on the Lyapunov exponents becomes more significant. For the assumed parameters of the viaduct, in pass-bands, the damping of the piers and beams has a larger influence on the wave localization than the pier-height and beam-length disorders, while in the stop-bands, the disorders have a more pronounced influence on the wave localization than the damping.

    • Test Study on the Dynamic Behavior of Dry Sands Subjected to Impact Loading

      2015, 37(S2):131-136. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0131

      Abstract (734) HTML (0) PDF 2.98 M (794) Comment (0) Favorites

      Abstract:A split Hopkinson pressure bar(SHPB) was appropriately modified to study the dynamic behavior of dry sand. A stable, incident, reflective, and transmitted waves under the strain rates of 102~103 s-1 were obtained and a rubber membrane barrier was found to facilitate transmission of the pressure wave. The results showed that strain rate effect can be ignored for dry sand at high strain rate. For sand samples of the same thickness, the strain rates were increased as the load increased. The experimental results suggested an upward trend in strain rate. Under the identical loading conditions, as the thickness of sand samples was increased, the resulting strain rate decreased.

    • Seismic Stability Analysis of High Earth-Rock Dams Based on Improved Dynamic Distribution Coefficients and a Modified Drucker-Prager Model

      2015, 37(S2):137-141. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0137

      Abstract (807) HTML (0) PDF 1.92 M (1067) Comment (0) Favorites

      Abstract:The seismic acceleration dynamic distribution coefficient suggested in the current code for seismic design of hydraulic structure(DL5073-1997) is suitable for earth-rock dams that are below a height of 150 m. However, currently, most earth-rock dams being designed are higher than 150 m. Compared with low-height dams, tall dams have less constraint from the stiffness of their foundation and the self-vibrating period of the high dam is prolonged under cyclic loading. During the seismic response of the dam body, the high order self-vibrating period has more opportunities to coincide with the seismic predominant period and high order vibrations are easily activated and amplified, which causes the seismic acceleration distribution to be dissimilar to that in short dams. Using the finite element method, the seismic acceleration distribution of high earth-rock dams can be analyzed. The analytical results allow for the determination of the seismic acceleration dynamic distribution coefficient of earth-rock dams 250 m level in height. On the basis of these results, employing a modified Drucker-Prager model and strength reduction technique, further research on the slope seismic stability analysis of earth-rock dams 250 m level in height was made. The conclusion of this analysis was that a decrease of the seismic acceleration dynamic distribution coefficient in the dam body causes an increase in the critical value of safety factor of the dam slope.

    • Research on the Deformation Characteristics of Typical Accumulative Landslides in the Three Gorges Reservoir under Earthquakes

      2015, 37(S2):142-146. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0142

      Abstract (648) HTML (0) PDF 6.58 M (1294) Comment (0) Favorites

      Abstract:Seismic actions in the head region of the Three Gorges Reservoir(TGR) have increased significantly since the beginning of dam impoundment. Coupled with cyclical water level fluctuation, the deformation mechanism of landslides beside TGR are worthy of research. A typical accumulative landslide located in Xingshan County was selected as a case study in this paper. Three typical adverse conditions were determined by monitoring relationship between the water level fluctuation and time of seismic occurrence. Then, using a seismic intensity of V degree, a multi-field coupling numerical simulation was conducted to determine the deformation mechanism of the landslide. The results of the simulation afford the following conclusions:(1) Seismic action is closely related to water fluctuation, while superposition of adverse flow conditions and seismic load, the coupling effect of the seepage field and dynamic field causes a landslide deformation.(2) The structure of the debris landslide is relatively homogeneous, except for the region close to the free face of body of debris. There are no significant undesirable geologic elements and seismic amplification is not reflected in the debris. Furthermore, the mechanical parameters of debris and bedrock are quite different, thus the boundary of debris and bedrock is also a deformation border.(3) When the seismic intensity attains the V degree, a deformation landslide caused by continual earthquakes is limited and convergent, but long-term deformation monitoring for landslides is necessary.

    • Nonlinear Characteristics and Sensitivity Analysis of Slope under Earthquakes

      2015, 37(S2):147-151. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0147

      Abstract (750) HTML (0) PDF 3.36 M (716) Comment (0) Favorites

      Abstract:Using a time history analysis method the nonlinear characteristics of the response of slope dynamics were studied, employing criteria such as the safety factor of the soil strength, ground peak acceleration, and earthquake energy with a threshold based on the influence of these parameters on the nonlinear slope dynamics characteristics. The study results showed that for some rock and soil materials, displacement, velocity, and acceleration of the slope dynamic response which are strongly correlated show obvious nonlinear characteristics. It was found that each study particle had a unified waveform and there was a significant displacement lag and velocity variation in the relative seismic acceleration. Particle acceleration was synchronous with the seismic acceleration. The peak ground acceleration, input direction, and duration threshold variations were within the slope safety coefficient, and the distribution of plastic zone appeared to have an influence on slope safety.

    • >地震科学技术
    • Case Study of Impending Strong Earthquake Prediction Combining the Rhythm of Multiplied Nine Days in Different Years and Double Magnetic Storm Time Method

      2015, 37(S2):152-156. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0152

      Abstract (743) HTML (0) PDF 858.21 K (1073) Comment (0) Favorites

      Abstract:The rhythm of multiplied nine days in different years is one method for predicting an imminent earthquake on the basis of the occurrence time of strong earthquakes in a certain region. In this study, we analyzed the predictions of four famous earthquakes in China by combining this method and the double magnetic storm time method, and the results show that the combination of these two methods better predicts the imminent occurrence time of strong earthquakes.

    • Tracking Analysis of Focal Mechanisms and Stress Field of Small Earthquake Concentrating Area in Puyang, Henan Province

      2015, 37(S2):157-163. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0157

      Abstract (739) HTML (0) PDF 6.40 M (1155) Comment (0) Favorites

      Abstract:In the border area of Hebei, Shandong, and Henan provinces in north China, moderate-to-strong earthquakes have occurred frequently including the Cixian ML7.5 earthquake of 1830 and the Heze ML7 earthquake of 1937. In recent years, moderate earthquakes have occurred frequently in this region, especially at the border area of Puyang, Henan Province and Juancheng, Shandong Province. Clusters of small-to-moderate earthquakes in this region have been referred to as "small earthquake concentrating area in Puyang". Four earthquakes of ML≥3 have occurred in this area since the 2011 Fanxian earthquake(Oct. 13, ML4.3) with a frequency of 1, thus indicating a significant in decrease in seismicity in this area. Earthquakes of ML≥2 have occurred more frequently since Nov. 2013, including the two Fanxian earthquakes(Nov. 20, 2013ML3 and Aug. 5, 2014ML3), thus indicating increased seismicity. These frequent small and moderate earthquakes provide primary information of regional tectonic stress field. In this study, we evaluated the stress field of this area from focal mechanism solutions obtained by applying Snoke's algorithm to the data collected from the Seismic Network Centers of Shandong, Hebei, and Henan provinces. We can better understand the Liaokao fault zone by analyzing pre-earthquake characteristics, such as spatio-temporal variation of principal compressive stress axis(especially P axis) and the consistent parameters of focal mechanism solutions of moderate-strong earthquakes, as well as the background and the seismogenic structure of this region. These results are also valued as a good reference for earthquake risk estimation, rapid earthquake damage assessment, and determination of correlation between characteristic variation of tectonic stress field and earthquakes in this area. The results show that the focal mechanisms are predominantly strike-slip fault solutions, and tectonic stress features horizontal or near horizontal torsion. Further, the azimuth of the P axis is related to seismic activity, and the temporal variations of P axis can be used as a reference for predicting small and moderate earthquakes in this region. Pre-earthquake spatio-temporal variation is a complex process that varies between different regions; therefore, further research is required on more cases to obtain more effective solutions for earthquake disaster prevention.

    • Analysis of Interference in Geoelectric Observations in Shandong Province

      2015, 37(S2):164-169. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0164

      Abstract (796) HTML (0) PDF 3.67 M (632) Comment (0) Favorites

      Abstract:In this study, we analyze the natural and anthropogenic interference on geoelectric observations in Shandong based on data tracking and analysis of the geoelectric observation data. Results show that(1) when the observation system receives strong interference, the observation data is synchronized with noise or missed entirely; this was easier to distinguish.(2) The geoelectric observation data is strongly distorted by lightning; amplitude reaches tens(or even hundreds) kV/km. This phenomenon is observed several times.(3) Abrupt rainfall causes data inconsistencies. Above-average rainfall affects the normal diurnal variation form; the correlation coefficient, between the geoelectric data and the diurnal cycle, is reduced from 0.8 to 0.6, or even lower.(4) The HVDC effect is significant. When the current is injected, the output is significantly higher. When the injected current falls to zero, the output is a straight line.(5) Human interference produces data discontinuities and changes in long and short-distance reception. However, the same measurement channel is almost the same.(6) The results of six tests on the variation of geoelectric storm produce consistent results; the maximal amplitude direction is the same in all cases, despite the fact that the different circumstances were expected to produce different amplitudes.

    • A Preliminary Study on the Medium Term Anomalies of Groundwater Level of Luzhou Well and the Tentative Index for Earthquake Prediction

      2015, 37(S2):170-176. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0170

      Abstract (763) HTML (0) PDF 2.06 M (904) Comment (0) Favorites

      Abstract:The seismic behavior monitoring of groundwater in China has over 40 years history. Cooperated with other precursor means, it has become one important means of all means for earthquake prediction. But the earthquake-reflecting condition of each well and the evaluation of them is different. People have different views on the revocation of Luzhou well in recent years. This paper selects historical target earthquakes based on the earthquake cycle and magnitude in Sichuan and Yunnnan area. We use the method combining qualitative(monthly average method) and quantitative(23 points smoothing method and subordinate function method) approaches to make a systematic analysis on monthly observation data of Luzhou well groundwater level from 1982 to 2014. We found 6 middle-term anomalistic changes, respectively, corresponding to one MS6.6 earthquake occurred at Batang in 1989 and five strong earthquakes including Wenchuan MS8.0 earthquake. Among these 6 middle-term anomalies, 2 anomalies belong in the Wenchuan MS8.0 earthquake. Also, these anomalies were tested by R value. Compared with other wells in Sichuan and Yunnan Province, facts have proved that the middle-term anomalies of Luzhou well water level are obvious, and are not unique case. In addition, the particularity of anomaly before the Wenchuan earthquake and post the Wenchuan earthquake is discussed. That is, second anomaly, and post the Wenchuan earthquake effect is remarkable and lasting. We use the statistical data and the subordinate function of the water level of Luzhou well to calculate the tentative index for middle-term prediction on the occurrence of earthquake. The index can be used to predict the period when a strong earthquake can most likely occur in Sichuan and Yunnan area. Finally, we come up a conclusion that Luzhou well can be used to perform a study on middle-term anomaly and prediction on strong earthquakes while there need to strengthen the management and study of the well. Also, we suggest waterfall can be used as a observed item since waterfall is relevant to the groundwater.

    • >土力学与地基基础
    • The Growth in Strength of Dry Jet Mixing Pile Composite Foundations over Time

      2015, 37(S2):177-180. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0177

      Abstract (733) HTML (0) PDF 1.68 M (745) Comment (0) Favorites

      Abstract:According to the experimental analysis of the strength of dry jet mixing(DJM) pile and the soil between piles of differing age, it was found that the strength of the DJM pile grew over time. The strength of the soil between the piles was also obviously improved over time.

    • Numerical Analysis of Stiffness Degradation of a Rigid Short Pile in Clay under Horizontal Dynamic Loads

      2015, 37(S2):181-184. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0181

      Abstract (688) HTML (0) PDF 2.69 M (1152) Comment (0) Favorites

      Abstract:The horizontal response of a loaded pile under the sea has attracted more and more attention in recent years. The ultimate horizontal capacity and stiffness of the horizontal response are two principal aspects of a pile response to a horizontal load that require assessment by the designer. This paper is based on the cyclic mobility model and soil-water coupled FEM, reports a study of the relationship of the horizontal load and displacement and the regulation of the stiffness degradation of a rigid pile under horizontal dynamic load. It also accounted for the difference of the horizontal ultimate pile capacity between dynamic and static horizontal load and conclusions are made that may assist in future design and investigation of this phenomenon.

    • Numerical Simulation of Direct Shear Tests on Standard Sand

      2015, 37(S2):185-190. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0185

      Abstract (823) HTML (0) PDF 4.74 M (1925) Comment (0) Favorites

      Abstract:By indoor direct shear tests, we acquired quantitative results from different sides of standard sand structures. The increasing complexity of the test method and a growing number of structural elements compelled people to consider the mesoscopic structural elements in combination with the macro mechanical properties. Currently, parameter analysis relies mainly on the numerical simulations of this method. The PFC(Particle Flow Code) is the commonly used simulation software. PFC takes the internal structure of the medium as the basic unit(particle and contact) and studies the mechanical characteristics and mechanics of the medium system's response from the perspective of the media structure's mechanical behavior. This study discusses the influence of particle friction coefficient, particle stiffness, particle shape, the porosity of sample to direct shear macroscopic mechanical behavior, and compares the simulation results and laboratory soil test results. The resulting numerical model mainly recreates the direct shear test of standard sand. Results show that the PFC process simulation standard for the basic mechanical behavior of sand is feasible, and the results provide reference for future numerical simulation experiments for standard sand.

    • Numerical Simulation of the Saturated Silt Composite Foundation

      2015, 37(S2):191-196. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0191

      Abstract (823) HTML (0) PDF 4.67 M (1437) Comment (0) Favorites

      Abstract:Using numerical analysis and comparison of three types of composite foundations used to treat liquefied saturated silt, a summary of the anti-liquefaction performance of the three types of composite foundation was determined. The experimental results showed that:(1) the development trend of excess pore pressure of natural saturated silt was the same at different depths, but the pore pressure of the shallow layer is lower. The distribution of the pore pressure ratio is small in the shallow layer and high in the middle and deep layers.(2) In terms of reducing the pore pressure, the multi-pile(gravel pile + cement, fly-ash gravel(CFG) pile) composite foundation and the gravel pile, both have little effect on the pore pressure of the shallow and middle layers, but the gravel pile has better effects on the deep layer.(3) In terms of reducing vertical deformation, multi-pile(gravel pile + CFG pile) and CFG pile are more effective than the gravel pile, but the multi-pile foundation offers the most pronounced effect.

    • >岩土工程
    • Application of the FCEC Fully-revolving Pile Pulling Method in Underground Obstruction Cleaning of the Longyao Road Cross-river Tunnel Project

      2015, 37(S2):197-200. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0197

      Abstract (1048) HTML (0) PDF 2.05 M (1171) Comment (0) Favorites

      Abstract:The Longyao road cross-river tunnel will undercross the wharf piles foundation of the Yaohua glass factory, so some of the existing piles should be pulled out of the soil before the shield tunneling. After comparison of all pile pulling methods, considering the characteristics of this project, the FCEC method was selected. The basic principle, advantages, and construction flow are introduced, as well as the background of the project. During the process of pile pulling, the maximal settlement of the flood-control wall was 6 mm and the differential settlement was 5 mm, which met the security requirements. This construction practice provides reference to similar projects.

    • Discussion of the Composition and Division of a Prestressed Anchor Structure

      2015, 37(S2):201-206. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0201

      Abstract (820) HTML (0) PDF 1.95 M (1099) Comment (0) Favorites

      Abstract:The method that anchor structure is divided into fixed length, free length, and anchor head using industry standards and engineering practices, but it has been found that this approach cannot meet the requirements of anchor technology development. Therefore, another method is suggested in this study that employs a body rod as the anchor will be divided into bond, non-bond and tension lengths. Erroneously employing in the bond length as the fixed length has been the rule in numerous engineering projects. The functions between the fixed length and bond segment are different, so the free and non-bond segments cannot be confused. The packer is the key physical element that distinguishes the fixed length from the free length, the start-stop position and fixed length are unknown without a top-grouting plug, so that the fixed length is often not accurately designed or calculated. The tension-type anchor is partially characterized by a tension-compression anchor and, in practice, is the actual position of the packer. To ensure the fixed length of the anchor outside of the assumed stability slip surface and within the stability of the soil layer, the packer should be set outside of the assumed stability slip surface at 1~2 m.

    • Application and Recent Research Progress of Vibratory Probe Compaction Method

      2015, 37(S2):207-213. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0207

      Abstract (690) HTML (0) PDF 1.43 M (926) Comment (0) Favorites

      Abstract:The vibratory probe compaction method is a deep dynamic compaction method that offers numerous merits without packing. Its simplicity offers advantages to the construction industry, including convenient construction, a short construction period, which is economical and effective. Consequently, this technique has been widely used in the treatment of foundations abroad and now its development and application has begun in China. The current research in this technique is summarized in this review. Topics include a review of the applicability of the technique, the compaction effect and the reinforcement mechanism of the vibratory probe compaction method. The state of the art of three key factors in the vibratory probe compaction method is summarized. Finally, the outstanding issues and the direction of development of the technology are detailed.

    • Preliminary Analysis of Underwater Vibrating Compaction Technology for Scattering-Filling Rubble Stone Layer

      2015, 37(S2):214-217. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0214

      Abstract (802) HTML (0) PDF 1.29 M (948) Comment (0) Favorites

      Abstract:At the site of the Hong Kong-Zhuhai-Macao bridge project, the underwater stone bed needed compaction. However, conventional underwater dynamic compaction could not be used to tamp the scattering-filling rubble stone layer with no dead angle over a short period of time. Thus, vibrating compaction technology was used underwater for the first time in China. Owing to the scarcity of engineering examples, theoretical analysis was needed prior to field application. In this study, rubble stone layers and vibration systems were simplified to a mechanical model. The vibration equation was established, and through strict mathematical deduction, the vibration system's work on the rubble stone was obtained. The results show that the weakening effect of water on vibration compaction is very poor.

    • Quantitative Analysis of the Evaluation of the Reinforcement Effect of Dynamic Compaction Using a Rayleigh Surface Wave

      2015, 37(S2):218-222. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0218

      Abstract (680) HTML (0) PDF 1.44 M (821) Comment (0) Favorites

      Abstract:A quantitative evaluating technique was employed to determine the accuracy and efficiency of dynamic compaction. The shear wave velocity of a foundation at different depths was obtained by inverting the dispersion curve of the Rayleigh wave. Using laboratory compaction and shear wave velocity testing of the soil samples from selected sites, the relationship between the void ratio and shear wave velocity was raised. This relationship was based on a wave velocity measurement reference standard at this site. A quantitative parameter δ was used to evaluate the dynamic compaction effect. On the basis of the calculation of this parameter and employing Rayleigh surface wave test evaluation, the effect of dynamic compaction was quantitatively evaluated. The relative quality of the soil and dynamic compaction effect was successfully determined using the proposed Rayleigh wave quantitative analysis technology.

    • >技术交流
    • Combined Use of Matlab and GMT Software to Draw High-accuracy Topographic Maps

      2015, 37(S2):223-229. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0223

      Abstract (798) HTML (0) PDF 4.18 M (2989) Comment (0) Favorites

      Abstract:The digital elevation model(DEM) is a new technology, which developed rapidly in recent years. It is widely applied in the surveying and mapping. Terrain analysis related to elevation using DEM is the main means of tectonic-activity and Neotectonic research. The analysis of geomorphological attributes can effectively provide important information on the geological structure and its evolution. Currently, there are many software applications that can be used to draw DEM topographic map, such as Mapsis, DEM, Global mapper, Arcgis, Surge with Topo Plug-in. In many cases, these applications are used to complete map drawing and data analysis However, these methods are deficient, when referring to new methods and innovative ideas. GMT is an outstanding common drawing software application that is widely used by many customers. It can produce beautiful graphics and has a flexible organization, while offering powerful data processing and analysis capabilities. The user can customize the maps for analysis according to their own research ideas and better display the results. It is a great professional drawing software and the ideal choice for high quality. In recent years, many researchers tried to solve specific GMT problems, such as GMT Chinese characters display function realization, special data input, and GMT interface visual operation. In this paper, we choose Matlab for visualization of GMT data processing and the command input to separate the GMT from the text command pattern and achieve simple operation and flexible application. This approach offers very important applications for many geological researchers and can help the users to improve the ability to display high-quality research results.

    • Application of ArcGIS Advanced Mapping Technology in Earthquake Emergency Thematic Map

      2015, 37(S2):230-235. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0230

      Abstract (1273) HTML (0) PDF 15.64 M (2496) Comment (0) Favorites

      Abstract:Computer mapping has largely replaced traditional cartographic methods because of the continuous developments and upgrades in geographic information system(GIS) mapping technology. ArcGIS, a software suite released by ESRI, can conduct high quality mapping, display the desired information, and improve the expressiveness of maps. ArcGIS also satisfies the requirements for the production of thematic maps for earthquake emergencies. In this study, we discuss the application of ArcGIS advanced mapping technology to thematic mapping for earthquake emergencies and produce as an example a template of a Qinghai thematic map for earthquake emergency response. Our study results provided solutions to several problems encountered in traditional GIS mapping, such as non-standard processes, unclear thematic elements, and overlapping labels, thus improving mapping efficiency for earthquake emergency response applications.

    • A Rapid-Transmission System for Earthquake Information Based on Web Service

      2015, 37(S2):236-239. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0236

      Abstract (793) HTML (0) PDF 3.67 M (673) Comment (0) Favorites

      Abstract:The current SMS system of the Liaoning Seismic Network can only send messages to China Mobile users; in addition, there are too many manual operations during the process of sending short messages, which affects the transmission efficiency and accuracy. To solve these problems, we developed a new seismic short message fast-transmission system based on Web Service and PyQt. The system can automatically generate seismic short messages and select the receiving personnel, and can be flexibly modified according to special circumstances. In addition, viewing the status of the sent messages is easy. The system configuration is straightforward and the system can automatically generate a running log, which assists with maintenance of and fault-finding for the system.

    • >其他
    • Discussion of Several Conductive Models Based on the Complex Resistivity of Organic-Rich Shale

      2015, 37(S2):240-245. DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0240

      Abstract (708) HTML (0) PDF 2.75 M (1130) Comment (0) Favorites

      Abstract:Recently, shale gas entered our exploration area as an unconventional energy source.Geological study has shown that the shale in southern China has good qualities for exploration.Because of the unique storage conditions and continuous complicated accumulation patterns of shale gas, it is difficult to use conventional geophysical methods to predict sweet spots.According to geological deposition theory, the total organic carbon(TOC) is the basic element that controls the formation of pyrite in marine sediment under a deep water deposition environment.There is a close relationship between the TOC and pyrite in such deep water deposition environments.In this paper we have found that pyrite plays an important role in the prediction of TOC.Through laboratory measurement analysis and joint inversion of the complex resistivity and phase, the marine organic-rich shale samples showed low resistivity and high polarizability.We think that the induced polarization(IP) electromagnetic exploration method can evaluate shale gas formation effectively, and application has shown that IP results are in good agreement with the seismic prediction for sweet spots.With the growth in global demand for oil and gas resources, conventional oil and gas exploration and development potential is very narrow, but unconventional reservoirs are open.Recently, shale gas has become the new target of global oil and gas exploration and development.Exploitation of shale gas and tight oil has brought a major change to the world which is gradually affecting the pattern of world energy supply and demand.It is estimated that there are rich marine shale gas resources in the south of China.Geologically, there are six sets of marine shale formations in Proterozoic-Paleozoic strata in southern China.Specifically, in the Silurian Longmaxi group(S1l) and the Cambrian Qiongzhusi group(∈ln), the shale has a good quality of TOC and thickness, which indicate the huge potential reserves of unconventional gas.The seismic method is certainly the first choice to predict sweet spots, but unfortunately, it has run into difficulties in southern China because of rugged tomography and complicated geology.Because of the low resistivity and strong polarization of marine organic-rich shale compared with the surrounding rock, the IP electromagnetic exploration method, which has been considered as an effective supplementary method, can be used to do that. At room temperature and atmospheric pressure, the complex resistivity sweep measurement is obtained for a saturated shale core by the SI1260 impedance analyzer.Finally, the joint inversion of complex resistivity amplitude and phase is conducted using single Cole-Cole, double Cole-Cole, Cole-Cole multiply Brown, and Dias models.Inversion results indicate that the double Cole-Cole and Cole-Cole multiply Brown models can describe shale cores' complex resistivity and phase curves with smaller fitting errors than the other models. We can get accurate spectral parameters from each inversion.It is useful to find shale reserves by the IP method and to realize shale gas complex resistivity logging.

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