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  • Jun LI, Yang ZHAO, Zhaozhou CHEN, Lele ZHANG, Huan CAO, Shichang LI
    Advances in Earth Science. 2024, 39(11): 1196-1209. https://doi.org/10.11867/j.issn.1001-8166.2024.085

    Borehole collapse pressure prediction plays a key role in drilling safety, reducing construction costs, and realizing efficient drilling. Fracture development under complex ultra-deep geological conditions significantly affects the prediction of borehole collapse pressure. Conventional methods rely on finite element simulations for 3D geomechanical modeling and 3D collapse stress prediction, which although, highly accurate, requires substantial computational resources. To address this issue, the study proposes an efficient and rapid in situ stress modeling method driven by seismic data, utilized for 3D collapse pressure prediction. Initially, a combined spring model with curvature properties is developed using a multi-scale data of pre-stack seismic and rock mechanics logging to model a three three-dimensional in situ stress field efficiently and rapidly. Next, based on the maximum likelihood attribute, the fracture development was obtained from 3D seismic data to provide 3D weak surface attribute parameters for the study area. Finally, the collapse model of sliding along the fracture plane was calculated using the Mohr-Coulomb criterion. This enables the collapse pressure prediction of the fractured formation from one-dimensional logging data to a three-dimensional working area. This method was applied to the woodworking area of Tari, with results showing a high agreement between model predictions measured data, reaching 93.79%. The prediction results also aligned well with formation micro-resistivity scanning imaging interpretations, verifying the method’s feasibility for predicting borehole wall collapse events. This study demonstrates that rapid, high precision modeling of collapse pressure can provide an integrated geological engineering solution for drilling in ultra-deep and complex areas.

  • Zhenyang Zhao, Shuangjian Li, Genhou Wang
    Advances in Earth Science. 2020, 35(2): 137-153. https://doi.org/10.11867/j.issn.1001-8166.2020.003

    Cherts contain important information of paleogeography, paleostructure and paleo-ocean, which is the important means of studying petrotectonics. With regard to the major disputes on the sedimentary environments, origin and source of Gufeng Formation bedded cherts in the northern margin of middle-lower Yangtze area, demonstrations from both forward and reverse aspects from the perspective of the sedimentary-tectonic evolution were given. By summarizing previous views on the genesis of bedded cherts in Gufeng Formation, and extensively collecting published original geochemical data, in the forward demonstrations we created the database of the cherts about rare earth elements to systematically identify the sedimentary environments, origin and source of cherts. By sorting out the time and cause of the main geological events in the middle Permian in south China, in the reverse demonstrations we established the sequence of tectonic evolution to verify or explain the current series of disputes. The results show that: Except some areas, such as Guichi-Tangtian, Tongling-Huashupo and Chaohu-Pingdingshan in Anhui province, which were affected by volcanic activities and faults, the bedded cherts of Gufeng Formation in the northern margin of middle-lower Yangtze area are mainly of non-hydrothermal origin or biological origin, and deposited in the passive continental margin deep water environments. Paleocontinental uplift in cathaysian and sea level eustacy controlled the input of some terrestrial materials in the the Gufeng Formation bedded cherts in the study area, but the contribution of terrestrial materials to cherts is not obvious. The study of cherts in Gufeng Formation is of great significance to the eruption time and dynamic mechanism of Emeishan basalts.