Experimental Study On Mechanism Of Supply & Exhaust In Volcanic Gas Reservoir Under Pressure

In recent years, China has successively discovered a large number of volcanic gas reservoirs in Songliao Basin, Junggar Basin, and Bohai Bay etc. With huge resource and great development potential, volcanic gas reservoirs has turned into a recent research hotspot. As a new research direction in gas reservoirs development, mechanism of supply and exhaust has rarely been researched at home and abroad. There are still many problems to be resolved. Based on the characteristic of low permeability and crack growth in volcanic gas reservoirs, this paper carried out the study on mechanism of supply and exhaust under pressure. Achieved the following results and understanding:1. Through volcanic cores seepage state experiment, the seepage state dividing has completed using Reynolds number and Knudsen number in volcanic gas reservoirs.2. The series and parallel experiment of dry crack and matrix cores showing that:(1) When crack and matrix in parallel, the supply and exhaust capacity of crack is much larger than matrix; crack is the advantage channel relative to matrix, the greater differential of crack and matrix, the more stronger capacity of supply and exhaust crack have relative to matrix; increase pressure gradient or permeability can increase the capacity of crack and matrix; increase the length of crack and matrix will weaken their capacity of supply and exhaust.(2) When crack and matrix in series, the supply and exhaust capacity of crack in the former as gas source and matrix in the post as exhaust channel is greater than matrix as gas source and crack as exhaust channel; increase pressure gradient or permeability can enhance the supply and exhaust capacity of series system; the permeability of matrix determines the supply and exhaust capacity of series system; increase the length of crack or matrix will weaken the supply and exhaust capacity for series system.3. The series and parallel experiment of water-bearing crack and matrix cores showing that:(1) Crack and matrix in parallel, when the core end have a certain flow, the crack in a low water saturation, with the time growth the crack water saturation decreased significantly, the velocity of supply and exhaust in exponential grow; the matrix in a high degree water saturation, with the time growth the matrix water saturation have less decline, the velocity of supply and exhaust in linear grow.(2) Crack and matrix in series, when the core end have a certain flow, the water saturation of crack is lower than matrix; with the time growth, the crack (matrix) which as gas source water saturation have a smaller decline, and the matrix (crack) which as exhaust channel water saturation have a larger decline; with the water saturation reducing, the supply and exhaust velocity increase linearly for series system.Mechanism of supply and exhaust has certain significance on the development of volcanic gas reservoir and the understanding of volcanic gas reservoir seepage law.