关键词: 致密砂岩气藏, 自支撑裂缝, 导流能力, 损伤机理, 裂缝壁面特征

Abstract: For the change in unpropped fracture conductivity after fracturing in tight sandstone gas reservoirs, an experimental method for unpropped fracture conductivity evaluation with fracture wall simulation was established to investigate the damage mechanism of conductivity in terms of the microscopic morphology, roughness, strength and other aspects of the fracture wall, and to clarify the variation law of fracture conductivity. The study shows that after the fracture was exposed to water, the wall clay was hydrated and compacted under stress, and the average height of the wall was decreased by 8.5%; meanwhile, the fracture wall was softened and the average hardness decreased by 34.3%. The more frequent the change in production nozzle size, the higher the conductivity of the unpropped fracture under high stress; the fracture conductivity of the third well opening was 91.7%-98.5% lower than that of the first well opening; the conductivity of misaligned fractures was 18.1-140.4 times that of non-misaligned fractures. With the formation water displacing fracturing fluid after fracturing, the conductivity of the final fracture was 3.45 times that of the original fracture. In this paper, the conductivity damage mechanism in the production of tight gas reservoirs was defined, and the variation law of unpropped fracture conductivity under the action of different factors was clarified, which provides a basic theoretical basis for the protection of unpropped fractures in tight sandstone gas reservoirs.

Key words: tight sandstone gas reservoir, unpropped fracture, conductivity, damage mechanism, fracture wall characteristics