Abstract: In order to understand the pressure sensitivity of porosity of volcanic rocks with different lithology,the representative rock samples of andesite, breccia tuff and tuff in Changling fault depression were collected to measure porosity by gas method under the overburden pressures of 3.4, 8.3, 13.1, 17.9, 22.8, 27.6, 32.4 and 37.2 MPa respectively. The results show that with the increase of pressure, the porosity of the three lithological types of  samples decreases in different ranges, and the decreasing level is tuff, breccia tuff and andesite from large to small，whichindicates that the pore stress sensitivity of tuff is the strongest, breccia tuff is in the middle, and andesite is the weakest. The analyses of whole rock X-ray diffraction, rock slice identification under polarizing microscope, high-pressure mercury porosimeter experiment and nuclear magnetic resonance experiment based on CPMG pulse sequence show that rock composition, particle sorting and pore type are the key factors affecting pore pressure sensitivity; The larger the volume fraction of plastic minerals, the smaller the particles and the smaller the pore size, the stronger the pressure sensitivity of the corresponding porosity.

Key words: volcanic rock, pressure sensitivity, porosity, mercury intrusion, rock thin section, whole rock analysis