川东北地区致密碎屑岩动静弹参数实验研究

利用“MTS系统”对四川盆地东北部上三叠统和中侏罗统致密碎屑岩进行了模拟地层条件下的波速及力学参数同步测试,并讨论了弹性参数的变化规律以及动静态参数间的关系。随着岩石中泥质含量和孔隙度的增加,波速和杨氏模量均降低。多数情况下,平行层理方向样品的波速、动态杨氏模量和体积模量大于垂直层理方向。随着温度的升高,波速、动态杨氏模量和体积模量都呈下降趋势。随着有效围压的增加,波速、动态杨氏模量和体积模量均呈现增加趋势,而泊松比在饱水时降低、干燥时增加。随着轴向差应力的增加,波速先增后降;对于砂岩,纵横波峰值速度大致在极限强度的80%和50%处。饱水样品的纵波速度和动弹模量明显大于干燥样品,而横波速度与饱水与否无关。动杨氏模量大于静杨氏模量,而动静泊松比间的相对大小关系不明显。 

AN EXPERIMENTAL INVESTIGATION OF DYNAMIC AND STATIC ELASTIC PARAMETERS OF COMPACTED CLASTICS,THE NORTHEAST SICHUAN BASIN, CHINA

The ultrasonic wave velocities and mechanical parameters of compacted clastics of Upper Triassic and Middle Jurassic in the northeast Sichuan Basin,with current burial depths ranging from 320 0 m to 420 0 m,aremeasured simultaneously under simulated formation conditions(including temperature,pore pressure,confining pressure,air-dried or saturated by water,and different directions of samples).The composition and structure of rock are the inherent factors determining the velocities and mechanical parameters,with the velocities and Young's modulus decreasing along with the increases in clay content and porosity.Generally,the velocities and dynamic elastic moduli of samples parallel to bedding are greater than those perpendicular to bedding,while the Poisson's ratio is an exception.The velocities,dynamic Young's modulus and bulk modulus increase along with the decrease in temperature and increase in effective confining pressure,while the Poisson's ratio shows no evident rule to the changing of temperature,and increase for air-dried samples and decrease for samples saturated with brine as the effective confining pressure increases.Both P-wave and S-wave velocities increase firstly and then decrease along with the increase in additional axial stress,with the maximum velocities corresponding respectively to 80% and 50% ultimate compressive strength of sandstones.The P-wave velocity and dynamic elastic moduli of samples saturated by brine are greater than those of air-dried samples,with the exception of(S-wave).The dynamic Young's moduli of all samples are greater than the static Young's moduli,but the dynamic and static Poisson's ratios show no such rule.