Administrator Andrew Andronikou has begun the paperwork after a possible buy-out by four consortia failed to materialise by Thursday afternoon's deadline.
Chainrai's spokesman Phil Hall said: "We have started the process of putting the club into administration and this is due to be completed at the High Court in London first thing tomorrow (Friday). The administrator has begun work immediately on the paperwork and this should be completed by tomorrow."
Pompey will become the first Premier League club to go into administration and will be docked nine points as a result, which virtually ensures relegation from the top flight.
Hall said talks had not broken down with the four interested groups but the club had not been attractive enough to them in its current financial state.
He added: "Once the club is in a more viable state it may become more attractive to them in terms of a takeover."
Chainrai, who is looking to recover a £17million loan he made to the previous owners, has moved to prevent the club from being wound up in the High Court on Monday over £7.5million owed to HM Revenue and Customs.
The automatic nine-point penalty will leave Pompey on just seven points, 16 behind their nearest rivals.
There is now the prospect of a continuing player exodus and a long period of rebuilding in the Championship.
Source: PA
Source: PA