The invention discloses an ultra-deepwater offshore oil-gas
engineering developing
system and a mounting method thereof. The ultra-deepwater offshore oil-gas
engineering developing
system comprises a water-surface floating production device, a stand
pipe supporting pontoon, an
underwater oil extraction device, an upper part flexible
jumper pipe, a lower part rigid stand
pipe and a
seabed well mouth device; the
underwater oil extraction device is arranged on the stand pipe supporting pontoon; and benthonic oil-gas resources finally reach the water-surface floating production device through the
seabed well mouth device, the lower part rigid stand pipe, the stand pipe supporting pontoon, the
underwater oil extraction device and the upper part flexible
jumper pipe. According to the ultra-deepwater offshore oil-gas
engineering developing
system disclosed by the invention, the huge weights of underwater stand pipes and an oil extraction device are borne by the stand pipe supporting pontoon, and the dynamic load to be borne by the water-surface floating production device is reduced, thus the design requirements on the water-surface floating production device are reduced; in addition, the underwater oil extraction device is arranged on the stand pipe supporting pontoon, thus the ultra-deepwater oil-gas extraction operation can be carried out by the mesopelagic water-surface floating production device and the oil extraction device, the
investment cost is rather largely reduced, and the installation and the maintenance are facilitated.