胡高伟, 李彦龙, 吴能友, 陈强, 刘昌岭, 刘振纹. 神狐海域W18/19站位天然气水合物上覆层不排水抗剪强度预测[J]. 海洋地质与第四纪地质, 2017, 37(5): 151-158. DOI: 10.16562/j.cnki.0256-1492.2017.05.015
引用本文: 胡高伟, 李彦龙, 吴能友, 陈强, 刘昌岭, 刘振纹. 神狐海域W18/19站位天然气水合物上覆层不排水抗剪强度预测[J]. 海洋地质与第四纪地质, 2017, 37(5): 151-158. DOI: 10.16562/j.cnki.0256-1492.2017.05.015
HU Gaowei, LI Yanlong, WU Nengyou, Chen Qiang, LIU Changling, LIU Zhenwen. UNDRAINED SHEAR STRENGTH ESTIMATION OF THE COVER LAYER OF HYDRATE AT SITE W18/19 OF SHENHU AREA[J]. Marine Geology & Quaternary Geology, 2017, 37(5): 151-158. DOI: 10.16562/j.cnki.0256-1492.2017.05.015
Citation: HU Gaowei, LI Yanlong, WU Nengyou, Chen Qiang, LIU Changling, LIU Zhenwen. UNDRAINED SHEAR STRENGTH ESTIMATION OF THE COVER LAYER OF HYDRATE AT SITE W18/19 OF SHENHU AREA[J]. Marine Geology & Quaternary Geology, 2017, 37(5): 151-158. DOI: 10.16562/j.cnki.0256-1492.2017.05.015

神狐海域W18/19站位天然气水合物上覆层不排水抗剪强度预测

UNDRAINED SHEAR STRENGTH ESTIMATION OF THE COVER LAYER OF HYDRATE AT SITE W18/19 OF SHENHU AREA

  • 摘要: 天然气水合物上覆层不排水抗剪强度是水合物试采过程中导管喷射设计、地层沉降和井壁稳定性分析的关键参数。孔压静力触探(CPTU)为地层强度参数纵向分布规律研究提供了有效途径。本文基于南海北部神狐海域W18/19站位水合物上覆层的CPTU测试结果和室内实验数据,建立了该区经验锥头系数的确定方法,并基于确定的经验锥头系数求解上覆层不排水抗剪强度。结果表明:W18/19站位水合物上覆层由上至下为强度逐渐增大的钙质黏土,基于总锥尖阻力、有效锥尖阻力、超孔隙压力求解钙质黏土不排水抗剪强度的经验锥头系数分别为13.8、4.2、14.4。水合物上覆层不排水抗剪强度随着深度的增加逐渐增大。基于CPTU建立的不排水抗剪强度计算方法能反映钙质黏土不排水抗剪强度的纵向分布规律。

     

    Abstract: Undrained shear strength of the cover layer of hydrate is the most important engineering parameter for conductor jetting design, strata settlement and well stability analysis during gas hydrate production test. The piezocone penetration test (CPTU) could provide effective data to understand the vertical change of undrained shear strength from seabed to hydrate bearing layer. In this paper, we conducted CPTU and corresponding laboratory test at site W18/19 of the Shenhu area, northern South China Sea. Based on the data, the estimation method of cone factor was developed to calculate the undrained shear strength. The result shows that the cover layer of hydrate is mainly consist of calcareous clay and the soil strength becomes harder with the increase in depth. The cone factors calculated from total cone tip resistance, effective cone tip resistance and excess pore pressure is 13.8, 4.2 and 14.4 respectively. Based on the CPTU data, the developed method was used to calculate the vertical change in undrained shear strength, which increases with depth within the W18/19 cover layer of hydrate.

     

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