LONDON, Aug 13 (Reuters) - Differentials for Nigerian crude neared their lowest in six weeks for some major grades, as an abundance of unsold cargoes around the Atlantic Basin weighed on prices, traders said.
* For the past week, North Sea prices in particular have slid as major traders struggle to sell crude from floating storage.
* Around 40 cargoes of Nigerian crude for loading in August and September are still up for sale, which is around two-thirds of the originally planned amount for the two months, traders said.
* Forcados was offered at $1.30 a barrel above dated Brent, down from an offer from Shell at $1.35 late last week, while Bonny Light was said to be holding at $1.35 a barrel. Both grades were closer to $1.50 just two weeks ago.
* About half a dozen cargoes of Angolan crude are still up for sale from the 47-strong September loading programme. Some sellers are offering cargoes on a delivered basis in Shandong, which can be a sign that holders of physical barrels are having more difficulty in placing their oil.
* OPEC on Monday forecast lower demand for its crude next year as rivals pump more and said top oil exporter Saudi Arabia, eager to avoid a return of oversupply, had cut production.
* The head of Royal Dutch Shell's global refining operations Lori Ryerkerk will step down at the end of the month after five years in a job where she oversaw a vast overhaul of the business, according to an internal memo seen by Reuters.