Jihed,
I remember they have some tugs used in the caspian for very shallow water, I'm not in office now and don't have details of the bollard pull, but was enough to move the anchors of the barge during the pipelay.
Also, as GregLamberson pointed out, several method are used in the very shallow water of caspian: onshore fabrication and then pull or towing, offshore fabrication and pull to shore, conventional S-lay.
Sorry, I don't know of other Company/ Vessel specifically, as I only come across some study developed for Saipem in the Caspian sea using both Castoro12 and Ersai as construction barges.