PHYSICAL SIMULATION EXPERIMENT AND EXPLANATION OF GAS ACCUMULATION MECHANISM IN THE DEEP BASIN GAS ACCUMULATION REGION AND ITS HIGH-PERMEABILITY SAND BLOCK

Physical simulation experiment indicates that,pressure of the deep basin gas accumulation and its high-permeability gas-rich zone are not invariable,but change periodically with the geologic conditions (gas providing intensity and quantity).During the construction period of deep basin gas accumulation,the high-permeability gas-rich zone of deep basin gas accumulation and the compact sand body around form 2 independent positive pressure systems respectively,due to the permeability difference between them.During the dispersing period of deep basin gas accumulation,both pressure system decrease to negative pressure state and become an united pressure system.The evolution is of the characteristics of sinusoidal curve.Negative pressure is not the basic charateristic of deep basin gas accumulation,but one characteristic of the dispersing period during the formation and evolution of deep basin gas accumulation.The formation and evolution of deep basin gas accumulation experience 6 stages:gas entrance,critical touching time,"dessert" fornning,connection of 2 gases,expansion of gas accumulation,and adjust-mix.The controlling forces include gas expanding force,capillary pressure and buoyancy,which play different roles during different stages.Thus,relatively complete accumulation succession and mechanism model of deep basin gas accumulation and its high-permeability gas-rich zone under physical laboratory condition are established.