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Determination of rock stress by anelastic strain recovery measurement of an oriented core in the Nittsu region of Japan
Published in Katsuhiko Sugawara, Yuzo Obara, Akira Sato, Rock Stress, 2020
W. Lin, T. Hirono, T. Nakamura, K. Yamamoto, K. Matsuki, T. Imamura, Y. Oikawa, M. Takahashi, M. Kwasniewski
A deep well named METI (Ministry of Economy, Trade and Industry) Niitsu well was drilled in Niigata Heiya, Japan. The maximum depth of the well reached 5000 m MD with an inclination of about 20º, and the true vertical depth at the bottom of the well was 4702 m. The outline of the geological structure of the region has been given by Imamura (2003). At this site, the anelastic strain of oriented cores obtained from four depths in the range from about 2400m MD to 4500m MD was measured in six independent directions after the release of the corresponding in-situ stresses. In this paper, the anelastic strain measurement results for a core taken from the deepest location as well as the predicted orientations and magnitudes of three-dimensional principal in-situ stresses will be reported. The core of about 10cm in diameter was taken from a depth of 4544 m MD; the rock material was andesite. Major component minerals were feldspar, quartz, enstatite or hypersthene, and hematite. Dry bulk density of the rock was 2.72 g/cm3, and porosity determined using water saturation method was 0.71%. Compressional wave velocities measured in three directions on a cubic specimen obtained from the depth of 4542m MD, being macroscopically the same as the core used for ASR measurement, ranged from 4.4 km/s to 4.8 km/s, and shear wave velocities were 2.8–3.0 km/s. Although a slight difference between the velocities in different directions was revealed, distinct anisotropy of the texture of the cores could not be macroscopically observed. Poisson’s ratio calculated from compressional and shear wave velocities was equal to 0.20, approximately.
Use of risk-controlled model for predicting collapse pressure of vertical and inclined wells
Published in Heping Xie, Jian Zhao, Pathegama Gamage Ranjith, Deep Rock Mechanics: From Research to Engineering, 2018
Tianshou Ma, Tao Tang, Nian Peng, Yahui Wang, Zhaoxue Guo
To contrast the predicted results by traditional and risk-controlled method, the basic parameters are assumed and summarized in Table 3. Three kinds of typical in-situ stress state, such as normal faulting (NF), strike slip faulting (SS), and reverse faulting (RF), are considered. The other parameters are as follows: the true vertical depth of the borehole is 3000 m, pore pressure is 30 MPa, the azimuth angle of maximum horizontal in-situ stress is 90°, Biot’s coefficient is 0.8, Poisson’s ratio is 0.25, internal friction angle is 30° and cohesive strength is 15 MPa.
A model for nitrogen injection in horizontal wells of tight oil reservoirs
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Jiaxi Gao, Yuedong Yao, Zheng Liu, Jinxin Wang
Gould et al. (Gould 1974; Gould, Tek, and Katz et al. 1974) analyzed the pressure drop models of vertical and inclined pipe flow published at that time and discussed the possibility of extending these models to inclined and curved pipe flow. At the same time, a prediction model for the pressure distribution of vertical, inclined or curved two-phase pipe flow was proposed, and the model was combined with the existing pressure gradient prediction models of various flow patterns. Gould et al. believed that the flow pattern in a vertical or inclined pipe can be predicted by the single-phase flow rate, the physical parameters of the two-phase flow system, and the geometric parameters of the pipe. In a directional well, if the friction gradient is based on the length of the curved pipe rather than the true vertical depth, the two-phase pressure profile can be predicted more accurately. In the bubble flow, the total pressure gradient is mainly affected by the density gradient. In the mist flow, it is the friction gradient. If the pressure level at the pipe end is too low, it is the acceleration gradient.
Applied geophysics for cover thickness mapping in the southern Thomson Orogen
Published in Australian Journal of Earth Sciences, 2018
I. C. Roach, C. B. Folkes, J. Goodwin, J. Holzschuh, W. Jiang, A. A. McPherson, A. J. Meixner
Magnetic susceptibility data (Figure 16a) were collected using hand-held equipment at 1 m intervals from drill chips in the cover sequence, and at 0.5 m intervals in the basement diamond drill core. Magnetic susceptibility is generally subdued in the cover sequence, apart from the upper few metres, where maghemite is common in the surface lag. Below 165 m true vertical depth, many of the chip samples recovered were found to be contaminated by steel particles created during borehole casing welding and cutting operations, particularly in portions of the borehole immediately below where casing had been recently inserted. Accordingly, elevated magnetic susceptibility values in the lower portion of the Eromanga Basin cover sequence are not regarded as being reliable. The diamond drill core is not contaminated in any way by introduced magnetic particles and shows a subdued magnetic susceptibility in the paleoweathering profile, increasing below the paleoweathering front.