The invention relates to a drilling type
underwater horizontal Christmas tree and
wellhead system. The drilling type
underwater horizontal Christmas tree and
wellhead system comprises a drilling type
underwater Christmas tree, an underwater
wellhead system and an underwater
blowout preventer unit, wherein the underwater wellhead system comprises a guide
pipe head, a high-pressure wellhead head, a drilling
type conversion connector and a
casing hanger which are arranged in sequence from outside to inside in a sleeving mode, the lower end of the guide
pipe head is connected with a guide
pipe, the lower end of the high-pressure wellhead head is connected with a surface casing, the lower end of the drilling
type conversion connector is connected with an intermediate casing, the lower end of the
casing hanger is connected with a production casing, and the guide pipe, the surface casing, the intermediate casing and the production casing are arranged in sequence from outside to inside in the sleeving mode; and the lower end of the drilling type underwater Christmas tree is connected with the upper end of the high-pressure wellhead head of the underwater wellhead system, and the upper end of the drilling type underwater Christmas tree is connected with the lower end of the underwater
blowout preventer unit. The drilling type underwater horizontal Christmas tree and wellhead system has the passing capacity of a 12-1 / 4"
drill bit, and the underwater
blowout preventer unit only needs to be installed once in the installation process, so that the installation operation efficiency and the project economy are obviously improved.