Gas sand distribution prediction by prestack elastic inversion based on rock physics modeling and analysis

Seismic inversion is one of the most widely used technologies for reservoir prediction. Many good results have been obtained but sometimes it fails to differentiate the lithologies and identify the fluids. However, seismic prestack elastic inversion based on rock physics modeling and analysis introduced in this paper is a significant method that can help seismic inversion and interpretation reach a new quantitative （or semi-quantitative） level from traditional qualitative interpretation. By doing rock physics modeling and forward perturbation analysis, we can quantitatively analyze the essential relationships between rock properties and seismic responses and try to find the sensitive elastic properties to the lithology, porosity, fluid type, and reservoir saturation. Finally, standard rock physics templates （RPT） can be built for specific reservoirs to guide seismic inversion interpretation results for reservoir characterization and fluids identification purpose. The gas sand distribution results of the case study in this paper proves that this method has unparalleled advantages over traditional post-stack methods, by which we can perform reservoir characterization and seismic data interpretation more quantitatively and efficiently.

宁夏红柳井田延安组煤层对比研究

本文采用煤层间距、煤层自身特征、煤层组合、地震物性特征并结合沉积特征进行了了各主要煤层的对比,对延安组8层主要煤层进行了对比,对比结果可靠。

Brittleness index and seismic rock physics model for anisotropic tight-oil sandstone reservoirs

Brittleness analysis becomes important when looking for sweet spots in tightoil sandstone reservoirs. Hence, appropriate indices are required as accurate brittleness evaluation criteria. We construct a seismic rock physics model for tight-oil sandstone reservoirs with vertical fractures. Because of the complexities in lithology and pore structure and the anisotropic characteristics of tight-oil sandstone reservoirs, the proposed model is based on the solid components, pore connectivity, pore type, and fractures to better describe the sandstone reservoir microstructure. Using the model, we analyze the brittleness sensitivity of the elastic parameters in an anisotropic medium and establish a new brittleness index. We show the applicability of the proposed brittleness index for tight-oil sandstone reservoirs by considering the brittleness sensitivity, the rock physics response characteristics, and cross-plots. Compared with conventional brittleness indexes, the new brittleness index has high brittleness sensitivity and it is the highest in oil-bearing brittle zones with relatively high porosity. The results also suggest that the new brittleness index is much more sensitive to elastic properties variations, and thus can presumably better predict the brittleness characteristics of sweet spots in tight-oil sandstone reservoirs.

Property Identification of Anomalous Seismic Bodies by GMES Techniques, A Case History

What are the anomalous seismic reflection bodies at depths of over 6000m？Are they reefs or igneous rock？This is a difficult problem for seismic techniques,but the GMES technique can handle it .The GMES technique is a joint exploration technique combining gravity,magnetic,electrical,and seismic techniques.The specific procedure is to conduct a 2D interface-constrained CEMP inversion using 2D seismic and log data followed by a property parameter inversion of the anomalous bodics using gravity and seismic data by the stripping technique.We then estimate the physical properties ofthe anomalous bodies,such as density,susceptibility,resistivity,velocity,and etc.to deduce the geological features of the bodies and provide a basis for drilling decisions.The work in the TZ area reported in this paper shows the applicability of the technique.

Lamé parameters inversion based on elastic impedance and its application

The Connolly （1999） elastic impedance （EI） equation is a function of P-wave velocity, S-wave velocity, density, and incidence angle. Conventional inversion methods based on this equation can only extract P-velocity, S-velocity, and density data directly and the elastic impedance at different incidence angles are not at the same scale, which makes comparison difficult. We propose a new elastic impedance equation based on the Gray et al. （1999） Zoeppritz approximation using Lamé parameters to address the conventional inversion method＇s deficiencies. This equation has been normalized to unify the elastic impedance dimensions at different angles and used for inversion. Lamé parameters can be extracted directly from the elastic impedance data obtained from inversion using the linear relation between Lamé parameters and elastic impedance. The application example shows that the elastic parameters extracted using this new method are more stable and correct and can recover the reservoir information very well. The new method is an improvement on the conventional method based on Connolly＇s equation.

Anti-seismic behavior of HRB400 reinforced steel bars

The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing with HRB335 steel bars, i.e. coordination of strength and ductility, strain-aging sensibility, low temperature impact toughness, weld ability and high strain low cycle fatigue. The ductile-brittle transit temperatures of hot-rolled and strain-aged steel bars were evaluated as –17 °C and ?8 °C respectively, and the low temperature impact toughness of HRB400 steel bars remains to be improved. Transmission electron microscopy (TEM) and electron diffraction showed little vanadium existed in ferrite as VN, most of which existed in pearlite as alloy cementite which resulted in the declination of impact toughness. Methods were suggested to improve the anti- seismic properties of steel bars.

Feasibility study using simulation mode for offshore field SZ36-1

Field SZ36-1 is a water-flooded heavy oil reservoir with high porosity and unconsolidated sand. The recovery rate is low so that it becomes a challenge for production. Time-lapse seismic data is studied to improve the oil recovery for this field, This feasibility study analyzes the possible time-lapse seismic attribute spatial distribution using dynamic data and the reservoir model to determine the optimum time to acquire a new seismic survey. Based on the study, it is found that the time-lapse seismic response for this unconsolidated sand has a strong signature due to solution gas when the reservoir pressure is below the bubble point. This indicates that acquiring a new survey after 10 years of production is appropriate for a time-lapse seismic application.

Seismic force modification factor for ductile structures

The earthquake forces used in design codes of buildings should be theoretically determinable. This work examines the seismic force modification factor R based on elastic-plastic time-history earthquake analysis of SDOF systems, wherein the hys-teresis models are elastic-perfectly-plastic (EPP), elastic-linearly-hardening (ELH), shear-slipped and bilinear-elastic. The latter two models are analysed for separating the effect of the ductility and the energy-dissipating capacity. Three-hundred eighty-eight earthquake records from different site conditions are used in analysis. The ductility is taken to be 2, 3, 4, 5 and 6, with the damping ratio being 0.02, 0.035 and 0.05 respectively. The post-yield stiffness ratios 0.0, 0.1 and 0.2 are used in the analysis. The R spectra are standardized by the characteristic period of the earthquake records, which leads to a much smaller scatter in averaged numerical results. It was found that the most important factor determining R is the ductility. R increases more than linearly with ductility. The energy-dissipating capacity, damping and the post-yield stiffness are the less important factors. The energy dissipating capacity is important only for structures with short period and moderate period (0.3≤T/Tg<5.0). For EPP and ELH models, R for 0.05 damping is 10% to 15% smaller than for 0.02 damping. For EPP and ELH models, greater post-yield stiffness leads to greater R, but the influence of post-yield stiffness is obvious only when the post-yield stiffness is less than 10% of the initial stiffness. By means of statistical regression analysis the relation of the seismic force modification factor R with the natural period of the system and ductility for EPP and ELH models were established for each site and soil condition.

Estimation of reservoir porosity using probabilistic neural network and seismic attributes

Porosity is one of the most important properties of oil and gas reservoirs. The porosity data that come from well log are only available at well points. It is necessary to use other method to estimate reservoir porosity.Seismic data contain abundant lithological information. Because there are inherent correlations between reservoir property and seismic data,it is possible to estimate reservoir porosity by using seismic data and attributes.Probabilistic neural network is a powerful tool to extract mathematical relation between two data sets. It has been used to extract the mathematical relation between porosity and seismic attributes. Firstly,a seismic impedance volume is calculated by seismic inversion. Secondly,several appropriate seismic attributes are extracted by using multi-regression analysis. Then a probabilistic neural network model is trained to obtain a mathematical relation between porosity and seismic attributes. Finally,this trained probabilistic neural network model is implemented to calculate a porosity data volume. This methodology could be utilized to find advantageous areas at the early stage of exploration. It is also helpful for the establishment of a reservoir model at the stage of reservoir development.

AVO Character Research of Natural Gas Hydrates in the East China Sea

Natural gas hydrates are considered as strategic resources with commercial potential in the 21st century. Obvious BSR characteristics will be shown on seismic profiles, if there exist natural gas hydrates. The AVO method is one of the methods which can be used to identify and forecast lithologic characteristics and fluid properties by using the relationship between Amplitude and Offset. AVO anomaly is one of the significant signs to check out whether or not there is free gas below the BSR, so it can be used to detect natural gas hydrates from the seismic profile. Considering the geological and geophysical characteristics of the Okinawa Trough and making use of the techniques mentioned above, we can conclude that the conditions there are favorable for the formation and concentration of natural gas hydrates. By analyzing the data collected from the study area, one can discover many different anomalous phenomena on the seismic profile which are related to the existence of natural gas hydrates. Preliminary estimation of the natural gas hydrates in the Okinawa Trough shows that the trough is rich in natural gas hydrates and may become a potential important resources exploration area.

变形组构引起的超高压榴辉岩地震波速各向异性

超高压榴辉岩通常显示了强塑性变形和地震各向异性特征.对实验和天然变形超高压榴辉岩中主要矿物的地震波速性质及其变形晶格优选方位(CPO)与榴辉岩地震波速和各向异性之间的成因关系研究结果表明:(1)除石榴石表现为近地震波速各向同性外,榴辉岩中其他矿物都具有强地震各向异性(AVp=23.0%～40.9%,Max.AVs=18.5%～47.1%),是造成榴辉岩地震各向异性的主要来源矿物,石榴石和金红石的平均地震波速相对较高,绿辉石和柯石英中等,石英最小;(2)变形榴辉岩最大纵波波速(8.33～8.75km/s)方向近平行变形线理或面理,最小纵波波速(8.25～8.62km/s)近垂直线理或面理,纵波波速各向异性1.0%～1.7%,平均横波波速4.93～4.97km/s,其各向异性在同时与线理和面理成近45°方位接近最大(0.73%～1.78%),在面理面上接近垂直线理方位达到最小,横波快波极化取向近平行面理.超高压峰值变质条件(3～5GPa,900～1100℃)下榴辉岩地震纵波和横波波速预计比常温常压下分别高出3.4%～7.2%和6.3%～12.1%;(3)绿辉石矿物组分主导了榴辉岩各向异性基本特征,而石榴石矿物组分则起到了降低榴辉岩各向异性程度和增加地震波速的作用,石英矿物组分对榴辉岩地震各向异性影响不大但可以一定程度上降低榴辉岩的地震波速,金红石矿物组分的作用基本可以忽略;(4)榴辉岩地震波速在纯石榴石岩中最大但各向异性接近于零,随绿辉石含量的增加,地震波速逐步降低,各向异性逐步升高,纯绿辉石岩比纯石榴石岩地震波速低6%～8%,而各向异性则达到3%～4%.根据榴辉岩组成矿物的单晶弹性性质和变形CPO计算的榴辉岩地震物性与前人实测结果基本相当.研究成果获得了超高压变形榴辉岩的三维地震物性资料和相关的矿物物理成因解释.

Experiment Study and Interpretation on Relation between Modulus of Rock and Strain Amplitude

Nonlinear elastidty of the earth medium produces a numerical difference between the dynamic and the static modulus of rock. The dynamic modulus is calculated with the ultrasonic velocity measurement, the small-cycle modulus is calculated with small cycles in the load-unload experiment, the static modulus is calculated from the slope of the stress-strain curve in the large cycle, the Young＇ s modulus is obtained from the ratio of stress to strain in the measured point. The relationship between the modulus and the strain amplitudes is studied by changing the strain amplitude in the small cycles. The moduli obtained from different measuring methods are thus compared. The result shows that the dynamic modulus is the largest, the small-cycle modulus takes the second place, the static modulus of bigger-cycle is the third, and finally the Young＇s modulus is the smallest. Nonlinear modulus of rock is a function of the strain level and strain amplitude. The modulus decreases exponentially with the ascending of the strain amplitude, while increases with the ascending of the strain level. Finally, the basic concept of the P-M model is briefly introduced and the relationship between the modulus and strain amplitude is explained by the rock having different distribution densities and the different openand-close stresses of the micro-cracks.

A Preliminary Study on Seismicity and Stages of Seismic Energy Accumulation in Seismotectonic Regions of Tianshan

Using seismic parameters, the characteristics of the seismic activity in various seismotectonic regions of Tiaushan were studied in this paper. These regions are going through different stages of seismic energy accumulation. Current seismic risk levels of these areas were analyzed synthetically by the tectonic movement rates, as well as the characteristics of the seismic activity and the recurrence intervals of strong earthquakes. We preliminarily studied the characteristics of seismic activity in different seismic energy accumulating stages. The result shows that the characteristics of the seismic activity in various seismotectonic regions of the Tiaushan area are influenced, not only by the regional tectonic movement, but also by the energy accumulating stage of various seismic tectonics. In the intense tectonic movement areas, it is important to estimate its stage of energy accumulating in order to predict the upper limit of the potential earthquake magnitude. In the less intense tectonic movement areas, the estimating of the stage of energy accumulation will help us recognize the dangerous level of the potential strong earthquake. The study shows that the seismotectonic regions in southern Tiaushan have reached the mid-stage and late-stage of energy accumulation, with a higher seismic activity and thus a higher seismic dangerous level than those in the northern and middle Tiaushan. The earthquake risk of southern Tianshan is up to Ms7.0, while that of the middle Tiaushan is up to Ms6.0 and that of northern Tiaushan is only around Ms5.0 - 6.0.

Reducing of Seismic Vulnerability ＆ Short-Time Earthquake Prediction： Methods and Instruments of Nonlinear Seismology

Elimination of human losses is the main and immediate task in the seismic vulnerability problem.The authors suggest the ways of development of seismic research and discussion of defense problems for reducing of seismic vulnerability. It is the ways of nonlinear seismology region. Unconditionally seism zoning and the theory of catastrophes allow reduce human losses and building destruction. But well-known isoseists are the private case of caustic catastrophe theory or seismo-acoustics, so seism zoning can be amounted to 6 elementary catastrophe forms. It will better help to predict seismic actions. The short-time local prediction of seismic events is general method for strong reducing of human losses. This method takes into account chaotic properties of stress fields and waves and the peculiarities of urban area. It bases on the natural seismo-emission phenomenon and is realized by long-time monitoring, which gives statistically and geographically continuous picture （chart） of seismic noise level inside geologic media. The instruments of this strategy are shock and pressure-proofed seismometers for long-time monitoring and control the state of geological media including underwater shelf areas. The authors think that the active protecting for cities and buildings as the best modem form of people safety consists in stress discharge of geologic media. Ultrasonic wave defense includes and bases on strong interaction between powerful waves from earthquake and ultrasonic wave train. The authors want to point out that the technical objects may be used lbr the investigation of earthquakes induced and some reasons of seismic vulnerability. Also reducing of seismic vulnerability contains as component kinetic acting on volcano at the pre-explosive stage. The interesting and important aspect of defense problem is observation of the inharmonic wave processes in the soil and quasi-constant forces as the nearest seismic analogue of radiation forces in nonlinear acoustics under powerful earthquake seismic tremor.

Risk Analysis of Historic Urban Areas： A Case Study of the Salerno City, Italy

The preservation of historical and cultural heritage from seismic risk is a question of interest in Italy. However, too little has been done to deal with this problem. First of all, the seismic safety of cultural heritage should be a topic of prevention. The research described in the paper presents a multi-approach procedure to address risk assessment of large-scale urban systems with the aim to contribute at the development of risk mitigation policies for historical centers buildings. The observation of the earthquakes effects in Italy clearly highlights the role of the high vulnerability of the existing building on the consequences in terms of casualties and damage, rather than the severity of seismic events, especially in historical contexts. Unlike the new buildings which should be planned and designed to respect seismic safety requirements, existing buildings require a careful safety assessment on the basis of their susceptibility to damage which depends on building techniques, past damage events, maintenance, changes, etc.

Safety analysis of building foundations over old goaf under additional stress from building load and seismic actions

Additional displacement of the building foundations over old goaf are prone to happen under the addi- tional loads induced by new buildings, weakening-rock mass by mining and seismic actions, which will cause serious damage to the buildings. In order to analyze the safety of the building foundations safety over the old goaf. the structure characteristics of the strata over the old goaf was investigated and the instability conditions of overhanging rocks upon old goaf were also analyzed in this paper. The results indicate that the stability of overhanging rocks is remarkably decreased by the interactions of mining fractures, earthquake force and building load, in addition, the settlement of the foundations over old goal is increased by the instability of overhanging rocks. According to the location of a new power plant in Yima Mine and its ambient conditions, we defined the influence scope of old goal via resistivity tomography. Based on the seismic parameters of the construction site, a numerical FLAC3d model of the building foundation under the seismic actions and building load was developed. The numerical results are obtained as follows： the foundation of the main power house meets the requirement of 6° seismic fortification intensity： however, under 7° seismic fortification intensity, the maximum differential settlement of foundation between the neighboring pillars is close to the maximum allowable value, while the seismic fortification intensity reaches 8°, but the safety requirements will not be satisfied.

Determination of Water Saturation （SW%） by Using P-wave Velocities for Saturated Sandstone

The seismic velocities are strongly influenced by porosity and degree of water saturation, as well as other petrophysical properties, such as density and elastic properties of the rocks. In this paper, the saturation of water percentage for sandstones （SW%） has been calculated by mathematical equation, which is based on the relation between the seismic velocity of water to the seismic velocity obtained in the field （for p-wave velocity only）. The results of this equation which ranged between （30% to 100%） are connected with the results of seismic velocity-porosity relation for saturated sandstone through model, this model can be used for determining the porosity （Φ） and water saturation percentage （SW%） of the sandstones in the same time.

The Role of Architectural Considerations in Seismic Performance of Buildings： A Case Study in Iran

Experience from recent earthquakes such as Gilan, Zanjan, Bam and Lorestan earthquakes in Iran indicated that the constructed buildings are vulnerable against earthquake. Vulnerability of these structures is due to various reasons such as designing without considering seismic regulations, problems of regulations （design goals）, implementation problems, changing of the building occupancy class, increasing the weight of building stories, adding new stories to the building and changing in architecture of building without considering structural system. So the main objective of this research is to examine the features of building configuration and their effects as for the damages to buildings in past earthquakes. For this purpose, initially four occurred earthquakes in Iran are selected as case study. Then three types of buildings （steel structure, concrete structure and masonry buildings） are analyzed with details. Results showed that the most of damages are occurred in the old steel structures and masonry buildings which their ages are more than 25 years. The study showed that most of the buildings in the study area are steel structure and masonry buildings while concrete structures are infrequent which most of them had no or slight damages. Therefore, the importance and need to enhance the performance of available buildings against earthquake forces by rehabilitating methods would be more important than before. Also results indicated that the decisions related to architectural plan which have significant effect on seismic performance of buildings, can be divided into three categories： configuration of building, restrictive formal architectural plan and dangerous structural components, as these categories are not obstacle of each other, it is possible that each category has an influential effect on others. So organizing the design decisions in this way is very important so as to manage their effects and interdependencies.

Evaluation of the Policies for Seismic Retrofit of Buildings

The Japanese government has established a law to Hanshin-Awaji Earthquake in 1995. This paper evaluates the incentives of the policies related to the law. The data shows achieved in 2018 if the current trends of improvement will supports the school retrofit works that are carried out by the promote seismic retrofitting of buildings immediately after the Great effectiveness, efficiency, administrative feasibility and technological that the policy target of seismic safety of existing buildings will be be continued. In the field of school buildings, national government local governments, using the guideline for school retrofit. However, there are still significant issues to make all buildings safe. One of the key challenges is how to persuade the elderly who would not invest their money to improve their old houses. Another challenge is to make owners understand the importance and have priority in improving the seismic safety of buildings. Currently many efforts are taken by the local governments, such as holding seminars for local communities, preparing financial support schemes, providing consultancy for seismic assessment and making earthquake hazard maps. This paper also provides comments on the improvement of the current policies for promoting seismic retrofit based on some international experiences in retrofit of buildings.

Study of the approximate approaches to the POD based spectral representation method

The spectral representation method (SRM) is most widely used in simulating the stochastic field.The proper orthogonal decomposition (POD) based SRM is an important form.This paper investigates the approximate approaches to the POD-based SRM in simulating two typical problems,i.e.,the seismic ground motion and wind velocity fields simulations.Then,the accuracy resulting from the power spectral density matrix-based POD method (PSRM) is compared to that of the coherency matrix-based POD method (CPSRM).It is concluded that the CPSRM maintains a much higher accuracy than the PSRM.In the CPSRM,the linear interpolation of eigenvectors and third-order polynomial interpolation of eigenvalues can be accepted to attain high accuracy;the linearly distributed interpolation nodes are effective in the ground motions simulation;however,the exponentially distributed interpolation nodes are effective in the wind velocity simulation.