Provided is an ultra fine bubble production device capable of causing a liquid current to flow in a helical manner without reducing a flow rate of the liquid current while reducing the number of components. The ultra fine bubble production device includes the pipe, the compression device, and the gas bubble production medium. The gas bubble production medium is formed of a carbon-based porous material, the pipe has the side surface having a cylindrical shape and the end surfaces having a circular shape, the liquid current inflow port is provided on the side surface, the cylindrical guide member is arranged so as to be connected to the liquid current inflow port, and the guide member has the guide groove having a helical shape.

A device for CO.sub.2 microbubble flooding comprises a microbubble generating device, a stirring and liquid storage device, an injection pump, a gas compressor, a gas-liquid mixer and a pressure stabilizing system, wherein the microbubble generating device adopts an integrally formed multi-layer cylindrical metal powder-sintered porous plate, and the diameters of microchannels on the porous plate are sequentially reduced from inside to outside. A solution containing additives in the storage device is stirred uniformly and then enters into a downhole gas injection base pipe through the gas-liquid mixer to be injected into a stratum, then a carbon dioxide gas compressed by the gas compressor is pumped into the downhole gas injection base pipe through the gas injection pump, and the gas generates microbubbles in situ when passing through the multi-layer porous device under the action of pressure difference.