Flagship explorer Oil and Natural Gas Corporation (ONGC) could be looking at roping in other shipping companies for a joint venture to manage offshore support operations as its talks with state-owned Shipping Corporation of India (SCI) has hit choppy waters over valuation of its vessels for the purpose of transferring them to the proposed joint venture. Public sector company ONGC has been discussing the formation of a joint venture, proposed to be christened ONShip, with Shipping Corporation of India for forming a joint venture to help it outsource peripheral support services that require operating various kinds of vessels for its operations. Though executives from both companies deny any deadlock, saying talks are going on, sources say, differences remain on the valuation issue.