* China started to build its first offshore gas storage base in northern Chinese city Tangshan near the Bohai Bay rim, the National Development and Reform Commission said in a post on its website on Tuesday
* The base, including two gas storages -- Nanpu 1-29 and Pugu-2 - has designed storage capacity of 4.1 billion cubic metres and costs 6.47 billion yuan ($995.94 million) to build
* The projects will be part of PetroChina's northern China gas storage hub to improve supply of the lower-carbon fuel to the smog-prone region as well as petrochemical plants that use gas as feedstock.
($1 = 6.4964 Chinese yuan renminbi)
(Reporting by Muyu Xu in Beijing and Chen Aizhu in Singapore) ((email@example.com; +86 10 56692117;))