EVOLUTION AND PHYSICAL PROPERTIES OF SANDSTONE RESERVOIRS:CONSTRAINTS ON HIGH-PRESSURE TIGHT GAS DEPOSITS INDONGPU DEPRESSION, NORTH CHINA

Low-permeability and tight sandstone reservoirs in the Dongpu depression, North China, arecharacterized by thin layers, fine grains and evident sedimentary heterogeneity, which are buried in depthlarger than 3700m, with strong compaction, late-phase authigenic illite-chlorite and silica cementation.Physical properties of the sandstone reservoirs show texture of small pore and very fine pore-throat withlarger surface area, lower permeability sensitive to stratigraphic confined pressure, and real porosity andpermeability in buried conditions ranging in 10%~<5%, 0. 1×10-3~ <0.001×10-3μm2 respectively.The high-pressure tight sandstone gas deposits mostly occur in sub-class deep-sags of the Dongpudepression. It is presented that these deposits are of high-pressure hydro-gas features, which arecontrolled by low-permeability, high capillary number, high saturation of irreducible water, hightemPerature and high-pressure condition of reservoirs, and, in another hand, abundant gas supply fromnear sources to a larger extent.