ABSTRACT
To address the problems of the conventional composite supporting structures (CCSSs) such as insufficient anti-dislocation performance and deformation capacity, this study used Engineered Cementitious Composite (ECC) lining sections instead of the traditional lining sections and optimized support design parameters, resulting in the development of novel ECC-RC composite supporting structures (ECSSs) of tunnels passing through active fault. The dislocation response characteristics and their parameter sensitivity of the ECSS was revealed by way of 1/25-scale fault dislocation model tests and finite element analysis. The test results show that the mechanical response characteristics and the failure modes of the CCSS and the ECSS are similar under reverse fault dislocation. Compared with the CCSS, the anti-dislocation performance of the ECSS is significantly improved by introducing of the ECC lining and optimizing the design parameters. The vertical deformation of the ECSS and the range of influence under the same dislocation are significantly decreased, and the strain are reduced to different degrees. This phenomenon shows that by improving the material properties, shortening the spacing of aseismatic joints and optimising the thickness of the shock absorption layer, the stress conditions and applicability under deformation of the structure are improved. The ECSS benefits from the crack resistance and toughening effect of fibres, the degree and scope of cracking of the ECSS are significantly reduced compared with those of the CCSS, and internal and external through cracks and local spalling are absent. The results of finite element analysis show that the overall damage degree of the ECSS is decreased and the damage range is increased by decreasing the strength of the surrounding rock in the fault zone. The fault dislocation response pattern of the ECSS varies depending on the fault type. The damage degree caused by different fault types follows the order of normal fault, strike-slip fault, and reverse fault from large to small. However, the damage range caused by the strike-slip fault is significantly larger compared to normal fault and reverse fault. In the design of fault resistance, the surrounding rock conditions of the fault zone and the form of fault dislocation should be considered.
ABSTRACT
The marine controlled-source electromagnetic (CSEM) method has been used in different applications, such as oil and gas reservoir exploration, groundwater investigation, seawater intrusion studies and deep-sea mineral exploration. Recently, the utilization of the marine CSEM method has shifted from petroleum exploration to active monitoring due to increased environmental concerns related to hydrocarbon production. In this study, we utilize the various dynamic reservoir properties available through reservoir simulation of the Wisting field in the Norwegian part of the Barents Sea. In detail, we first developed geologically consistent rock physics models corresponding to reservoirs at different production phases, and then transformed them into resistivity models. The constructed resistivity models pertaining to different production phases can be used as input models for a finite difference time domain (FDTD) forward modeling workflow to simulate EM responses. This synthetic CSEM data can be studied and analyzed in the light of production-induced changes in the reservoir at different production phases. Our results demonstrate the ability of CSEM data to detect and capture production-induced changes in the fluid content of a producing hydrocarbon reservoir. The anomalous CSEM responses correlating to the reservoir resistivity change increase with the advance of the production phase, and a similar result is shown in anomalous transverse resistance (ATR) maps derived from the constructed resistivity models. Moreover, the responses at 30 Hz with a 3000 m offset resulted in the most pronounced anomalies at the Wisting reservoir. Hence, the method can effectively be used for production-monitoring purposes.
