Apparatus and method for CO2 microbubble flooding

A method for using an apparatus for CO2 microbubble flooding, wherein

• the apparatus comprises:
• a liquid flow path, a gas flow path and a microbubble generating device (5), wherein the liquid flow path is connected to a first passage of a gas-liquid mixer (3) through an injection pump (2) by adopting a stirring and liquid storage device (1), the gas flow path is connected to a second passage of the gas-liquid mixer (3) by adopting a gas compressor (4) and a pressure stabilizing system (6), and a third passage of the gas-liquid mixer (3) is connected to a threaded connection port (5d) of the microbubble generating device (5), the microbubble generating device (5) adopts a metal powder-sintered integrated multilayer cylindrical arc-shaped porous plate, the metal powder-sintered integrated multilayer cylindrical arc-shaped porous plate includes an inner layer porous plate (5a), a middle layer porous plate (5b) and an outer layer porous plate (5c), the inner layer porous plate (5a), the middle layer porous plate (5b) and the outer layer porous plate (5c) are sequentially arranged from inside to outside, a diameter of a microchannel on the outer layer porous plate (5c) is smaller than 0.5 μm, a diameter of a microchannel on the middle layer porous plate (5b) is smaller than 2 μm, a diameter of a microchannel on the inner layer porous plate (5a) is smaller than 3 μm, and the metal powder-sintered integrated multilayer cylindrical arc-shaped porous plate is fixed through a stainless-steel structure and connected with an inflow port of the gas-liquid mixer (3) through a thread structure, and
• the method comprises the steps of:
• S1, injecting an aqueous solution containing xanthan gum and sodium dodecyl sulfate into a liquid storage tank, and then stirring at a speed of 500 r/min-1000 r/min for at least two hours, wherein the foregoing uniformly stirred solution is used as a base solution comprising 3% of xanthan gum and 0.05% of sodium dodecyl sulfate;
• S2, injecting stirred base solution into a gas-liquid mixer (3) at a certain flow rate through an injection pump and pumping the base solution into a stratum to allow the base solution to saturate a bubble generating structure and the stratum around a wellhead in advance so as to provide a proper environment for subsequently injecting a CO2 gas and generating stable microbubbles;
• S3, pumping the carbon dioxide gas compressed by a gas compressor (4) into the gas-liquid mixer (3) through a gas injection pump at a pressure of 4 MPa;
• and
• S4, enabling the gas to pass through a three-layer metal-sintered porous plate under the action of pressure difference to generate microbubbles in situ;
• and after the microbubbles enter into the stratum, a Jamin effect is generated, and larger bubbles block a macroporous throat such that a flow direction of follow-up flow changes, the base solution for flooding is capable of entering into small pores, with an increased flooding sweep rate, thereby storing carbon dioxide in the stratum while completing the flooding.