Liquefaction test and seismic load simulation of saturated sand subgrade with different salt contents

On the basis of the highway subgrade construction of North Hobson Salt Lake mining area in Qinghai Province, the soil samples of high saline saturated sand adjacent to the salt lake were remolded, and four types of saturated sand containing 0%, 10%, 20%, and 30% salt were configured respectively, so as to explore the liquefaction effect of saline saturated sand under seismic load. After the indoor geotechnical test, the soil samples were reshaped, The liquefaction test of saline saturated sand was carried out by using the GDS dynamic triaxial device to simulate seismic load to investigate the liquefaction mechanism of saturated sand under different salt contents and verify the liquefaction discrimination standard, then based on the data of dynamic elastic modulus, dynamic shear modulus, damping ratio coefficient, and soil density obtained from previous soil tests and dynamic triaxial tests, four subgrade models with different salt contents were constructed using ANSYS simulation software according to actual engineering, and the settlement and deformation of the subgrade were analyzed by inputting EL-concrete seismic waves. The results show that the maximum value of axial stress of saturated sand decreases with the increase of salt content; the load vibration times of saline saturated sand reaching the initial liquefaction state are more than that of common saturated sand; the higher the salt content, the weaker the liquefaction resistance of saturated sand; when the pore pressure ratio coefficient reaches 1, the axial double amplitude strain εd of the soil also reaches 5%, and the soil reaches the initial liquefaction state; the area of shear stress and strain hysteresis curve increases with vibration load, and the elastic modulus decreases gradually; the shear dilation and compaction effects occur in each hysteresis cycle, and the former is greater than the latter, the research results have guiding significance for similar studies in highly saline saturated sand areas

Key parameters forecast model of injector wellbores during the dual-well sagd process

Based on parameters forecast model of conventional horizontal injector wellbore, combined with coupling calculation of dual-tubing steam mass flow, the mass conservation equation, energy conservation equation and momentum conservation equation of steam flow within injector wellbore under different tubing combinations in preheating and production phases are formulated and the key parameters calculation model of dual-tubing injector wellbore is established. The temperature and pressure along the injector wellbore during the steam-assisted gravity drainage (SAGD) preheating phase of a SAGD well are calculated and compared with the downhole monitored data, which shows good match and verifies the accuracy of the model. Meanwhile, the model calculates that the minimal steam injection rate during SAGD preheating phase is 60 t/d, the longest horizontal length is 564 m under current configuration. Considering the current configuration has disadvantages of two sections of steam imbibition that may result in risk of section/point steam breakthrough at Point A during SAGD production phase, the combination of long tubing and short tubing is optimized: the short tubing is relocated 150 m from Point A and long tubing is located at Point B. Consequently, three sections of steam imbibition could be realized, and the risk of section/point steam breakthrough at Point A is effectively reduced. Key words: dual horizontal wells, SAGD, parallel-tubing, wellbore, temperature, steam quality, pressur

Physical simulation of improving the uniformity of steam chamber growth in the steam assisted gravity drainage

In steam assisted gravity drainage (SAGD) process, there is an uneven distribution of steam chamber growth along the whole length of the horizontal well. In order to solve this problem, a three-dimensional high-pressure physical model of a SAGD well pair was built. Several significant reservoirs and operation parameters for SAGD were also scaled in the model size, which was based on SAGD pilot development of a typical reservoir in China. Three experiments were conducted using the above-mentioned high-temperature and high-pressure physical model. Test 1 simulated the slow steam chamber growth at the toe end and uneven distribution of steam chamber growth. Test 2 tested the regulation strategy with dual tubing strings to adjust the steam chamber based on Test 1-combining the long and short tubing strings for injection well and production well. Test 3 tested the regulation strategy with U-shape wellbore to adjust the steam chamber. The results showed that the two regulation strategies were effective for recovering steam chamber growth at the toe end and making steam chamber growth uniform along the length of SAGD wellbore. After regulating, the oil rate increased significantly. Key words: steam assisted gravity drainage (SAGD), high-pressure and high-temperature, 3-D scaled physical simulation, steam chamber growt

A new technology of 3D scaled physical simulation for high-pressure and high-temperature steam injection recovery

In order to solve the problems of existing physical simulation experiment device for thermal recovery, such as great heat loss, low precision in internal pressure control of physical model and insufficient process monitoring, a new experiment device for high-pressure and high-temperature (HPHT) 3D scaled physical simulation is developed independently, and the relevant experiment technical route is presented. By using thermal fluid simulation, PID auto-control and 3D graphics, the following problems are solved: (1) the heat loss scaled simulation technology is applied for HPHT thermal recovery model, to control the heat dissipating capacity of the model top and bottom and realize the continuous growth of the steam chamber; (2) HPHT 3D formation temperature/pressure simulation technology is applied to keep the model pressure and temperature stable, ensuring temperature difference at each point in high-pressure chamber less than ± 2 °C; (3) 3D data field on-line monitoring and visual analysis technology is applied to monitor and control the reservoir performance at real time. By using this experiment device, 3D scaled physical simulation experiment is performed for commingled thermal recovery of extremely heavy oil by horizontal/vertical wells as well as SAGD of super heavy oil by dual horizontal wells. The evolution of steam chamber is depicted and the knowledge on SAGD mechanism by dual horizontal wells and the production performance is deeply studied. 摘要: 为了解决现有热采物理模拟装置模型热损失大、模型内压控制精度低、实验过程监控不足等问题 自主研制成功了新型高温高压三维比例物理模拟实验装置并提出了注蒸汽采油高温高压三维比例物理模拟实验技术路线。该装置采用热流数值模拟、PID自动控制及三维数据场平面设计方法 重点解决了以下难题并形成特色技术°采用高温高压热采模型热损失比例模化技术 比例控制模型顶底散热量 实现汽腔持续发育 °采用高温高压三维地层温/压模拟技术 实现模型压力均匀稳定控制 高压舱内各点温差小于±2 ࠓ °采用模型三维数据场在线监测与可视化分析技术 实时监测与调控油藏动态。利用该实验装置开展了特稠油水平井与直井组合热采及超稠油双水平井SAGD 蒸汽辅助重力泄油三维比例物理模拟实验研究 完整刻画了汽腔发育规律 深化了对双水平井SAGD开采机理和生产动态规律的认识。图5参13 关键词注蒸汽采油 比例物理模拟 三维模型 高温高压 蒸汽辅助重力泄油-图分类号TE345 文献标识码A Key words: steam injection recovery, scaled physical simulation, 3D physical model, high-pressure and high-temperature, steam assisted gravity drainage (SAGD