Papers by Keyword: In Situ Stress

Abstract: Modern buildings erected on bedrock or is to be equipped directly in an array (in particular hydroelectric power stations, underground storage facilities and soon), are technically complex, often unique objects construction. At the same time, the cost of design and construction of such facilities is very high. In this context, particular relevance is the question of stable and safe operation of facilities. Now, generally recognized that the study of the functioning of large technical systems (such as the base - structure) with a randomly varying characteristics most adequately carried out was done by different types of complex modeling, particularly mathematical, simulation, and in some cases - physical modeling [3]. However, before moving to a system of «building/foundation» is necessary to examine the massif in situ. Modern software systems (such as Plaxis, ZSoil, Comsol, Abaqus, and soon) have are significant opportunities that allow to make calculations with high accuracy. In particular, implemented a specialized model of soils, such as models of Hoek-Brown, Jointed Rock and others [5]. They allow you to get a more objective picture of the state stress of the array according to the degree of fracturing and anisotropy properties. They allow you to get a more objective picture of the state stress of the array according to the degree of fracturing and anisotropy properties. In addition, is possible a reflection of the detailed features of the geological structure in the 3D calculation that gives an idea of the influence of the field to an array of building/foundation. But, it is necessary to understand that the simulation is based on idealization and averaging the physical and mechanical properties of the medium under study. The inevitable errors and inaccuracies in the calculations. As a real rock massif is a complex system, in the work showed of drawing up an analysis of structural models and their implementation using conventional concepts and a more detailed study. The isolation of the structural elements and boundaries in an array of rocky soils should be approached with special attention. This is due, primarily, with the features of the geological structure of the study area: for example, improperly allocate lithological boundaries as in the case of consideration arrays dispersed soils, because rocky soils is a monolithic solid. Select elements should be performed in accordance with the characteristic feature, such as a fracture, blocking and so on. Besides the issue of numerical modeling of rock masses, in the issues of verification data obtained by numerical method. With the increasing complexity of the technical constructions, increasingly there is a need to verify the results of numerical simulations with actual operating voltage value in the array. Since the field of stress research methods is very expensive and labor-intensive, trade-off seems logical to use in the verification of the results of numerical modeling of acoustic emission (AE) [6]. This method may be used in combination of laboratory tests. With this approach, it is possible to achieve significant improvements in the quality of the received information.

Abstract: In our country there is plenty of CBM (coalbed methane), but the state of CBM itself, unique output mechanism and low saturation, low permeability, low reservoir pressure and high gas content, et al. determine the low efficiency of it, so in order to improve CBM recovery, combined with the successful experience of north American shale gas reservoir by SRV(stimulated reservoir volume), the writer summarizes the implementation of SRV, deeply analyzes effectiveness and limitations of this new technology in CBM development. The results of practical research and theoretical analysis show that SRV in the coal reservoir can achieve the desired effect on the condition that there are great quantity of natural fractures, joints and bedding, weak structure surface development in the reservoir, the rock brittleness index is greater than 40 and horizontal principal stress difference is relatively smaller. Finally, simulating a well’s condition by the MEYER software, the result shows that SRV is feasible in coal reservoir, which will create important guiding significance and practical value for the exploration of CBM.

Abstract: Nowadays, hydraulic fracturing has become the mainly treatment in low permeability reservoirs, but the hydraulic fracturing design technology in different reservoirs still use common methods. Natural fracture reservoirs mainly include granite reservoir, basalt reservoir and igneous rock reservoir which its hydrocarbon pore volume is fracture system. As the existing of natural fracture, hydraulic fracturing treatment always counting some problems, such as difficult sand pumping, easily screen-out and limited scale. In this paper, from the point of the reservoir characteristics, the mainly problems were analyzed and the corresponding methods were put forward .the core technique in this kind reservoir include communicating the distance nature fracture and meanwhile protecting the conductivity nature fracture. Production can reach 90% from natural fractures using numerical simulation.

Abstract: Based on the measurement of in-situ stress and engineering-geological conditions, we built computing models with pre-exerting boundary loads and simulated the regional stress field involved. Boundary loads can be approximately determined by use of the multiple linear regressions, and be further optimized with the artificial neural network. By calculation, the corresponding initial in-situ stress field can reach ideal accuracy. As an example, we inversely analyzed an engineering problem in Chinese Wo-bei mine. The results shows that the simulation can meet the point measurement very well, and the regional-stress estimation may play an important role in engineering.

Abstract: Gaoligong Mountain tunnel is the key project in the Dali-Ruili Railway. In order to optimize the design and guide construction, In-situ stress has been conducted in five boreholes using hydraulic fracturing method, the current shallow crustal in-situ stress state at the project area are obtained according to the measurements results, and deep in-situ stress is predicted using lateral pressure coefficient. The test results show that at depths ranging from 299-979m, the maximum horizontal principal stress is 5.33-30.12Mpa, the minimum horizontal principal stress is 4.94-23.11Mpa, the horizontal principal stress reach 30Mpa at maximum the depth of burial, indicating that the engineering stress filed is dominated by horizontal stress. Based on the In-situ stress data and different distinguish methods, rockburst and large deformation are predicted. The results show that In-situ stress magnitude in this area is classified as high level, and the direction of the maximum horizontal stress is NEE, In-situ stress orientation is conductive to stable of the tunnel. When the tunnel passes through the deep-burial and hard rock, the wall rock may happen rockburst; and the large deformation may happen when the tunnel pass through the weak rock. In order to avoid the disadvantage conditions, reasonable excavation method and safety support method should be adopted during tunnel excavating.

Abstract: The frequency of fracturing practice in glutenite reservoir has increased gradually with the progress of exploration and development technology. Glutenite, which has properties like fast transformation in phase, great change in lithology, permeability and dip angle, irregular fracture face, disturbed flow phenomenon, severity in heterogeneity and complex pressure system,explains the low efficiency and success rate of hydraulic fracture's utilization in glutenite reservoir exploration and development. This paper features the glutenite reservoir in Songnan area, using PT software, with data of artificial fracture monitoring and well temperature etc. combined, to deal with construction curve, further explores the artificial fracture propagation mechanism. What's more, effect of in-situ stress on fracture propagation mechanism is determined and the fracturing technical measures in glutenite reservoir is also proposed with acoustic emission Kaiser experiment, both of which can effectively channel fracturing well and layer selection and design optimization, improve efficiency and success rate of hydraulic fracturing.

Abstract: For mine mining, In-situ stress is the fundamental force that causes the deformation and failure of surrounding rock in the mining engineering and supporting, and produces mine dynamic phenomena. Among many factors which affecting the stability of mining engineering, In-situ stress is the main and one of the most fundamental factors. According to the In-situ stress monitoring method some coal mine adopted, this paper introduces the concrete principle and working process.

Abstract: The impact disasters of rock burst and pressure bump are common problems of underground construction and deep mining ^[1-. This paper selected the typical mine based on the work of field crustal stress measurement, indoor rock mechanical experiment, parameter calculation, numerical analysis and field disaster investigation, etc,. Deeply analysed the basic types and potential laws of possible impact disaster after a mines main tunnel excavation based on the study idea of experimental rock mechanics and computational rock mechanics co-ordination and additional verification.

Abstract: In view of the low pressure tight gas reservoir in Songnan block, the comprehensive experiment of in-situ stress is carried out. Firstly, the tuffaceous breccia of Longshen 301 and 307 has been cored and the flag line is depicted. Through the viscous remanence experiment, the secondary viscous remanence component at 0°C~200°C is gradually separated, and the average direction of the two groups core flag line are obtained, which are 92.0° and 114.7°. Then to mark the flag line as the baseline, using the wave velocity anisotropy experiment to measure the acoustic wave velocity under different phase angle, the minimum wave velocity phase angle of the two groups core are achieved, which are 23° and 44° . And combined with the direction of the flag line, the direction of maximum horizontal principal stress are determined for N69o E and N70.7o E. Finally, using DSA (differential strain) experiment, the strain recovery of 9 direction under hydrostatic pressure are measured, and the three principal strain, the magnitude and direction of the principal stress are obtained through the inversion, the maximum principal stress direction of which are N70.8o E and N71.7o E. Compared the wave velocity anisotropy experiments and DSA experimental results, both close, the direction of the regional maximum horizontal in-situ stress is determined for N70.5° E ± 1.5°. According to the above research results, the basis for the engineering design of Songnan block such as oil and gas exploration, development, drilling and production is provided.

Abstract: This paper focuses on the research of the vertical and regional distributions of stress characteristics in the Shizhuangnan coalbed methane field, southeastern Ordos basin. The minimum and maximum horizontal stresses were firstly calculated by the breakdown pressure, closure pressure and tensile strength of the fracturing data of key wells. Then the calculated results are compared with the results calculated from the natural gamma-ray, density and acoustic logging data and Anderson’s Model. Based on the comparison, the residual stress in the Anderson’s Model is corrected. By adding the residual stress data in the Anderson’s Model, the modified model can be well used for evaluating the stress characteristics in the area with complex structure types. Finally, the distribution of stress characteristics in the Shizhuangnan coalbed methane field were evaluated by using the modified Anderson model.