Gianluca Di Marzio of Sky Sports provided details of the contract, revealing that the Senegal international will make £160,000 per week at Stamford Bridge in addition to numerous performance-related bonuses.
The winner of the Africa Cup of Nations will sign a five-year contract, according to Di Marzio, albeit the fifth year may merely be an option.
After the player accepted the terms of a massive contract on a personal level, the deal could be closed relatively fast.
The 31-year-old will join the Blues for for £33.8 million.
Di Marzio claims that the pace of the negotiations is such that an agreement could be finalized and signed in a matter of hours.
Napoli is prepared to sign a contract for €38 million (£32.1 million), which will be paid in two payments, with an additional €2 million (£1.7 million) in bonuses.
The defender has verbally agreed to personal terms with Chelsea, and negotiations have moved rapidly. Koulibaly only has one year left on his contract with the Italian club.
Koulibaly was given permission to meet with his agent in Milan to finalize the agreement, but the arrangement is far enough along that he might not return to Napoli’s preseason training in Val di Sole.