The invention discloses a slow blockage removing agent for an
oil well and a blockage removing method, and belongs to the technical field of
oil field exploitation. The slow blockage removing agent is prepared from prepad fluid, main fluid and post-pad fluid, the prepad fluid and the post-pad fluid both take
hydrochloric acid as the main component of acid fluid for removing inorganic scale
precipitation and dissolving reaction residues, and the main fluid takes glacial
acetic acid and
fluoboric acid as the main components of acid fluid for stabilizing clay mineral of a reservoir stratum, decreasomg the acid rock
reaction speed, enlarging the blockage removing
radius and increasing the blockage removing depth. For a fracturing production horizontal well, the treatment fluid is injected into the reservoir stratum in the former stage, the
intermediate stage and the later stage, and
liquid nitrogen is simultaneously injected, so that residual reaction fluid can be quickly drained after blockage removing construction is performed;
pollution blockage near a well bore of the
oil well can be effectively removed, the effective permeability near the well bore is increased, the individual-well producing rate is increased, damage caused by excessive
acid corrosion to the rock framework of the reservoir stratum can be avoided, and therefore the reservoir stratum can be prevented from being subjected to secondary damage.