By Laura Sanicola (Reuters) -Oil prices slid after rising earlier in the session on Thursday amid uncertainty that the euro zone will be able to effectively sanction Russian energy exports, and after consuming nations announced a huge release of oil from emergency reserves. Brent crude futures were down 78 cents, or 0.8%, to $100.29 a barrel at 1:46 p.m. EDT (1746 GMT), while U.S. West Texas Intermediate (WTI) crude fell 62 cents, or 0.6%, to $95.61 a barrel. Both benchmarks had plunged more than 5% in the previous session and hit their lowest closing levels since March 16. The European Union’…