A new Seismic Wave Attenuation Module to experimentally measure low‐frequency attenuation in extensional mode

A Seismic Wave Attenuation Module is developed to experimentally measure the attenuation in extensional‐mode Q E −1 and the Young's modulus of copper jacketed, 60 mm long and 25.4 mm in diameter samples in a gas medium (Paterson) rig. The new module is suitable for natural rock samples and was tested under confining pressure up to 50 MPa and room temperature. The module is designed to operate at a strain < 10 −6 , for which rocks behave linearly. To calculate attenuation, both the applied force and the bulk shortening of the sample are measured employing linear variable differential transformers. This technique allows measuring samples with a high degree of heterogeneity. Attenuation at low‐seismic frequencies (10 −2 –10 2 Hz) is obtained for rocks at dry and various saturation conditions. We present a series of measurements on Berea sandstone in a room‐dry condition and saturated with different fluids: water and glycerine solutions with viscosities of 10 cP and 22 cP, respectively, at a confining pressure of 10 MPa and with a pore pressure of 1 MPa. The accuracy of the attenuation data expressed as a phase shift is 0.0019 rad.