Conventional well test analysis methods and software are difficult to
accurately interpret hightemperature and highpressure (HTHP) gas reservoirs, thus affecting the decisionmaking of gas field exploration and
development. Based on the HTHP experiment of natural gas, the PVT fluid analysis method of hightemperature and highpressure gas reservoir was
formed in this paper. In addition, the percolation model of HTHP gas reservoirs was established and solved considering the startup pressure
gradient and stress sensitivity. A new generalized binomial productivity equation was established considering the formation pressure change during
the HTHP gas well testing. The software of well test analysis for HTHP gas wells in the west of South China Sea was formed by programming the
research results. The application shows that the accuracy of well test interpretation and productivity analysis can be ensured when the content of
nonhydrocarbons such as temperature, pressure and CO2 was high, and the problem of negative slope anomaly in traditional binomial analysis can
be also solved, so that the absolute open flow potential can be obtained. The software can be used to accurately interpret HTHP gas reservoirs and
provide technical support for exploration and development in the western South China Sea.