干热岩储层高温条件下岩石力学特性研究

Study on rock mechanical properties of hot-dry rock reservoir under high temperature

摘要:

为了更准确掌握高温条件下干热岩储层的岩石力学性质，进一步指导干热岩钻井施工，通过室内试验进行了实时高温条件下的巴西劈裂试验、剪切试验、单轴压缩试验。单一试验采用同一钻孔同一深度采取的岩样，通过高低温箱控制器设置温度和恒温时间，以恒位移速率0.1 mm/min对试样进行加载，减少岩石宏观力学性质的离散性和试验过程偏差对试验结果的不利影响。试验样品为山东省文登—荣成—威海地区LGZK1井采取的二长花岗岩，通过获得试样破坏时的最大荷载值和变形数据，计算其抗拉强度、抗剪强度、抗压强度、弹性模量等力学性质参数，分析实时高温条件下岩石内部破坏机理和岩石强度差异。研究结果表明，在200 ℃以内，花岗岩的抗剪强度和单轴抗压强度升高、抗拉强度降低；随着温度的进一步升高，花岗岩的抗剪强度和单轴抗压强度降低，而抗拉强度持续降低；储层岩体温度和应力的升高，将使岩石的硬度增加、塑性增强。这些认识可为高热流花岗岩岩石力学性质的进一步研究提供基本参数，为高热流花岗岩型干热岩资源勘探开发过程中碎岩机具的选型、钻井工艺的选择、井壁稳定的控制等提供参考依据。

关键词:干热岩储层;花岗岩;实时高温;巴西劈裂试验;剪切试验;单轴压缩试验

Abstract:

In order to know more accurately the rock mechanical properties of hot-dry rock reservoir under high temperature， and further guide the drilling work of hot-dry rock， the real-time Brazilian splitting test， shear test and uniaxial compression test under high temperature were carried out in laboratory. In a single test， rock samples taken from the same borehole and the same depth were loaded at a rate of 0.1mm/min by setting the temperature and holding temperature time using a high-low temperature chamber， to reduce the adverse influence of the discretization of rock macro-mechanical properties and the deviation of test process on the test results. The samples are monzonitic granite taken from the Well LGZK1 in the Wendeng-Rongcheng-Weihai area of Shandong province. Through obtaining the maximum load and deformation data of the samples at failure， the mechanical properties such as tensile strength， shear strength， compressive strength and elastic modulus are calculated， and the failure mechanism and strength difference of the rock under real-time high temperature are analyzed. As a result， the shearing strength and uniaxial compressive strength of granite increased and the tensile strength decreased below 200 °C. While the shear strength and uniaxial compressive strength of the granite decreased and the tensile strength continuously decreased with the increase of temperature. The increase of temperature and stress will increase the hardness and plasticity of the rock. It provides basic parameters for the study of rock mechanical properties of the high heat flow granite， and also provides a reference for the selection of rock-crushing tools， drilling technology and wellbore stability in the exploration and development of high heat flow granite type hot-dry rock resources.

Key words:hot-dry rock resevoir;granite;real-time high temperature;Brazilian splitting test;shear test;uniaxialcompressive test