Dynamic equations for nonassociated gas accumulation

Nonassociated gas can be classified as conventional gas accumulation with displacement migration, source-contacting gas accumulation with piston-type migration, and shale gas accumulation with the displacement and piston-type migrations. Nonassociated gas accumulation can be described by using the continuous but universal dynamic equation. The accumulation of conventional trap gas is controlled by buoyancy and capillary pressure, and the accumulation dynamic equilibrium is influenced by the height of the continuous gas column and the physical properties of seal rocks. Source-contacting gas accumulation is associated with gas-generating intensity of source rocks, physical properties of reservoirs, and accumulation depth, and the accumulation dynamic equilibrium is constrained mainly by the effectiveness of gas generation and the physical properties of tight sand reservoirs. In complicated geologic settings of shale gas accumulation, effectiveness of gas generation, physical properties of reservoirs, height of continuous gas column, and buried depth are the conditions influencing the accumulation of nonassociated gas.