STUDY OF THE DIFFERENCES BETWEEN THE DYNAMIC AND STATIC ELASTIC MECHANICS OF TERRESTRIAL SHALE OIL RESERVOIRS AS WELL AS THEIR RESPONSE CHARACTERISTICS

The difference in rock mechanical properties is a key technology in representing mechanical properties of reservoir rock and evaluating its fracturing performance. Rock mechanics instrument GCTS-1000 from the American core incorporation has been used to test the dynamic and static elastic mechanics property of the shale rock from Chang7 member in Triassic Yanchang formation within Ordos Basin, China, under the simulation condition of reservoir temperature and pressure. By comparing the test results and quantitatively analyzing the distribution characteristics, differences, corresponding relations and the limitation of the dynamic and static elastic mechanics parameters, the fracturing performance of shale reservoir is evaluated by the simulation equation transferred from dynamic and static elastic mechanics parameters based on the numerical fractal theory. The variation trends of parameters of dynamic and static elastic mechanics are consistent, that is, the dynamic Young modulus is 0.9~1.5 times the value of the static Young modulus, and their positive correlation fitting relation is good; the dynamic poisson ratio is higher than static poisson ratio and their fitting relation shows discrete state. During the experiment of simulated changing confining pressure, with the increase of the pressure, the corresponded speed of compressional and shear wave increase, dynamic and static Young modulus increase, dynamic poisson ratio decreases and static poisson ratio increases; during the experiment of simulated changing temperature, with the increase of the temperature, the corresponded speed of compressional and shear wave decrease, dynamic Young modulus decreases, static Young modulus increases, dynamic Poisson ratio slightly decreases and static Poisson ratio deceases dramatically. The differences in the dynamic and static rock elastic mechanics have been discussed as well as its mechanism behind their corresponding characteristics. Simulation equation transferred from the response of dynamic and static parameters under the simulation condition has been built. The combination of the test of dynamic and static elastic parameters and their simulation is an effective method in understanding the mechanical attribute of shale reservoir and evaluating its fracture performance.