Study on Mechanical Properties of Volcanic Breccia in Mahu Area, Xinjiang

The rock mechanics experiments of dynamic and static elastic parameters, brittleness index and fracture toughness of Mahu volcanic breccia in Xinjiang are carried out. The transformation relationship of dynamic and static elastic parameters, the distribution of brittleness index and the prediction model of fracture toughness are established, which is of great practical significance to the exploration and development of Mahu oilfield. The results show that: (1) The relationship between deformation characteristics of volcanic breccia and confining pressure is studied. The radial strain and transverse strain increase, and the stress at failure increases with the increase of confining pressure. The axial strain is larger than the radial strain under the same confining pressure. (2) The dynamic elastic parameters are larger than the static ones under the same confining pressure. The transverse and longitudinal wave velocity, the dynamic and static elastic parameters increase with the increase of confining pressure. (3) The brittle index distribution of breccias in Xinjiang is established, ranging from 12 to 68. Based on the fracture toughness test results, regression analysis was performed on density, tensile strength, elastic modulus, and Poisson's ratio. A prediction model for fracture toughness of the volcanic breccia in Mahu, Xinjiang was established, and its calculation results are highly correlated with the measured values. It provides basic parameters for the study of rock mechanical properties in Mahu oilfield, Xinjiang, and provides reference for the formulation of oilfield exploration and development construction scheme.