Method for backfilling and reconstructing carbon storage space in abandoned main roadway and storing CO2

A method for backfilling and reconstructing a carbon storage space in an abandoned main roadway and storing CO2, comprising following steps of:

• step 1, surveying a surrounding rock of the main roadway, and analyzing a density of the surrounding rock of fractures and cavities inside the main roadway;
• step 2, reinforcing and supporting the surrounding rock of the fractures and cavities by anchor bolts or anchor cables, so as to ensure a stable operation of the main roadway;
• step 3, customizing a support formwork according to a width and a height of a roadway section of the main roadway, wherein the support formwork is spaced apart a distance of 50 cm to 80 cm from a top, two sides and a floor of the main roadway;
• step 4, constructing a first backfilling wall at a first end of the main roadway, wherein a thickness of the first backfilling wall is of 50 cm to 60 cm to ensure that the first end of the roadway is completely sealed without air leakage;
• step 5, placing the support formwork made in step 3 inside the main roadway, splicing the support formwork according to a shape of the main roadway, attaching the support formwork closely to the first backfilling wall, and temporarily fixing the spliced support formwork by the anchor bolts and the anchor cables;
• step 6, injecting backfilling slurry into a gap between the support formwork and the main roadway through a backfilling pipeline to form a backfilling thickness of 50 cm to 80 cm around the main roadway;
• injecting supercritical carbon dioxide into the backfilling slurry between the support formwork and the main roadway, and enabling the supercritical carbon dioxide to fully react with the backfilling slurry for 3 h to 5 h to solidify the backfilling slurry to reach a support strength of 1 MPa to 2 MPa, and then stopping injecting the supercritical carbon dioxide;
• step 7, dismantling the support formwork and constructing a second backfilling wall at an interval of 30 m to 40 m from the first backfilling wall, after the backfilling slurry fully reacts with the supercritical carbon dioxide and solidifies;
• step 8, injecting the supercritical carbon dioxide into an enclosed space between the first backfilling wall and the second backfilling wall through a gas injection hole reserved on the second backfilling wall, and stopping injecting the supercritical carbon dioxide when an injection pressure of the supercritical carbon dioxide is from 1 MPa to 1.5 MPa and a CO2 concentration in the enclosed space between the first backfilling wall and second backfilling wall reaches 5,000 ppm and more, and then sealing the reserved gas injection hole reserved on the second backfilling wall;
• step 9, constructing the support formwork on a side which is opposite to the first backfilling wall, of the second backfilling wall, continuing to form an other enclosed space by constructing the support formwork, repeating step 5 to step 8, injecting the backfilling slurry and the supercritical carbon dioxide to the other enclosed space outside of the support formwork, and injecting the supercritical carbon dioxide into an enclosed space between the second backfilling wall and a third backfilling wall;
• and
• step 10, when the carbon storage space of the main roadway is backfilled and sealed to the second end of the main roadway, constructing a final backfilling wall at the second end of the roadway to enclose the roadway space, injecting the supercritical oxide dioxide into the carbon storage space, and sealing the carbon storage space.