The invention relates to an underground real-
time control system for the density of
drilling fluid. The underground real-
time control system for the density of the
drilling fluid comprises a drilling rig, an
air compressor, a
slurry pump, an intermediate transmission device, an
electromagnetic valve, a packer, a
wireless receiver and a ground
control system, wherein the intermediate transmission device consists of an inner
barrel and an outer
barrel, which are coaxially arranged; the
air compressor is connected to an air inlet of the inner
barrel; the
slurry pump is connected to a fluid inlet of the outer barrel; the
tail end of the inner barrel is connected with an inner
drill rod; the
tail end of the outer barrel is connected with an outer
drill rod; the
tail end of the outer
drill rod is connected with a drill collar; the tail end of the inner drill rod is fixedly arranged at the bottom of the drill collar; the tail end of the inner drill rod is connected with the
electromagnetic valve; the packer is arranged on the outer drill rod; a
wireless density sensor and a
wireless pressure sensor are arranged at the bottom of the drill collar; the wireless
receiver is connected with the ground
control system. According to the
system, the advantages of three drilling technologies, i.e. an overbalance drilling technology, an under-balanced drilling technology and a managed pressure drilling technology, are fully utilized, so that an underground
pressure difference can be switched between an overbalanced state, an under-balanced state and a near-balanced state, the drilling rig can safely and efficiently reach a destination layer, the non-production time can be reduced, and the drilling cost can be lowered.