IDENTIFICATION OF GAS-WATER ZONES IN VOLCANIC RESERVOIRS IN SICHUAN BASIN BASED ON PROBABILITY DISTRIBUTION OF LOGGING CURVES

The mineral compositions of volcanic rocks are complex, including mainly quartz, orthoclase, plagioclase, mica, hornblende, pyroxene and olivine. Due to various reservoir properties and pore structure types of different lithology, it is difficult to identify gas-water zones in volcanic rocks. Based on the logging data, first, the method of neutron-density crossplot is used to calculate porosity, and then the P^1/2 probability distribution curve is constructed combined with the laboratory rock electrical parameters and logging resistivity curve to identify volcanic gas-water zone according to the distribution pattern. The method is applied to the volcanic reservoirs in Sichuan Basin to identify the gas-water zones, and the interpreting conclusion is consistent with the gas testing results, indicating that the method is feasible and effective, and can guide the identification of gas-water zones in other lithology reservoirs.