Study on estimate method of wave velocity and quality fac-tor to fault seals

Based on ultrasonic test of fault rocks, the re-sponses for wave velocity and quality factor (Q value) to lithology, porosity and permeability of fault rocks and me-chanical property of faults are studied. In this paper, a new quantitative estimate method of fault seals is originally of-fered. The conclusions are as follows: (1) Wave velocity and Q value increase and porosity decreases with the increase in stress perpendicular to joint; (2) In compressive and com-presso-shear fault rocks that are obviously anisotropic com-pared with their original rocks, the wave velocity and Q value are greater in the direction parallel with foliation, and usually less perpendicular to it. In tensile and tenso-shear fault rocks that are not obviously anisotropic, the wave ve-locity and Q value are under that of original rocks; (3) In foliated fault rocks, the direction with minimal wave velocity and Q value is the best direction for sealing; on the contrary it is the best for flowing; (4) Structural factures develop mainly along foliation, the minimal wave velocity and Q value reflect the flowing capacity in parallel direction to fo-liation, and the maximal wave velocity as well as Q value reflect the sealing capacity in normal direction to foliation. The new estimate method is based upon contrast of wave velocity and Q value between fault rocks and their original rocks, and is divided into three parts that are respectively to identify rock’s lithology, to judge mechanic property of faults and to Judge sealing capacity of faults. Although there is vast scale effect between ultrasonic wave and seismic wave, they have similar regularity of response to fabric and porosity of faults. This research offers new application for seismic data and petrophysical basis for seismological estimation of fault seals. The estimate precision will be improved with the en-hancement of three-dimensional seismic prospecting work.