Abstract: With respect to the problem of starting pressure gradients during the low-speed flow of a gas from low-permeability gas reservoirs, a flow model was constructed, solved, and qualitatively analyzed. Using a low-speed non-Darcy flow mechanism, a model of the unstable flow in fractured low-permeability gas reservoir horizontal wells was constructed with the starting pressure gradient taken into account. The mathematical model was solved and a typical curve of production decline in the horizontal wells was plotted. The last solution of this flow model, that is, the unstable production of low-permeability gas wells under constant pressure production conditions was used to provide the theoretical basis for the use of graph fitting methods to assess the reservoir parameters. Analysis of the effects of the starting pressure gradients and other related parameters on the production- decline curve showed that as the starting pressure gradient increased, the storage properties became poorer, the flow became more difficult, the horizontal well production decreased, and the production decline curve shifted downward. With the decrease in the elastic storage ratio, the matrix channeling occurred earlier, the concave down portion of the production derivative curve increased in duration, and the degree of the downward concavity increased. When the channeling coefficient decreased, the concave down portion of the production-derivative curve shifted later and the channeling occurred less easily.

Key words: low-permeability gas reservoirs, binary medium, horizontal wells, production decline, starting pressure gradient