yes found them thanksIt's a cable laying vessel operated by the South Sea Fleet, and as far as we can tell, South Sea Fleet have at least 2 of such vessels.
Such vessel is used to lay submarine cables.
Cable laying ship Youdian 911 II at 1,350 tons and two units like you said at SSF Nan Lan 233 and 234
interestingly also at ESF Youdian 911 II Dong Lan 868, 873, 874, 882
and also at NSF Youdian 911 II Bei Lan 764, 765