VIENNA, March 4 (Reuters) – North Sea Forties crude differentials were unchanged on Wednesday after Total offered cargoes on a cost, insurance and freight (CIF) basis but no buyers emerged. PLATTS WINDOW * Forties: Total offered a cargo CIF Rotterdam for March 29-April 2 at dated Brent plus $1.90, down 30 cents from a similar offer on Monday. * Ekofisk: Total offered a cargo CIF Rotterdam for March 16-20 at dated Brent $2.95. * Troll: Total offered a cargo CIF Rotterdam for March 18-22 at dated Brent plus $4.10. (Reporting by Alex Lawler. Editing by Jane Merriman)