Rock Petrophysics Experiment In Medium-deep Gas Reservoirs

The medium-deep layer gas reservoirs are mostly low porous and low permeable. These reservoirs have the characteristics of complex pore structures, heterogeneity of lithology and physical property, complex distribution law of oil, gas and water, which make identifying and evaluating reservoirs more challengeous. The main reason of difficulties in evaluation is that there is not enough study and experiments on the mechanism of medium-deep gas reservoirs. The physical property parameters, rock-electro parameters and acoustic velocities of upper Paleozoic gas reservoirs in Gubei area were measured in the paper, which were in the conditions of different salinity and formation factors. The results showed that the porosity and permeability decreased with the increase of pressure, but the decrease of porosity was less than the decrease of permeability. The values of m deserved in formation conditions were smaller than deserved in room temperature and ambient pressure, and the difference was smaller with the increase of salinity.The experiment showed that the value of n was small in real formation conditions, the influence of salinity can be eliminated and the velocity of P-wave increased with the increase of water saturation, especially when water saturation was larger than 80%. The velocity of S-wave didn't change with the variance of water saturation. The velocities of P-wave and S-wave in real formation conditions were larger than in room temperature and ambient pressure. The influence of formation factors on parameters were analyzed from the mechanism of rock. On the basis of rock mechanism, the relations between the lithology, electric property, oil-bearing property and physical property were also analyzed in real formation conditions. Several logging interpretation models and evaluation charts were deserved by lithology. Deep study on the petrophysical experiments can provide technical guarantee for the evaluation of such reservoirs.