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The term crude slate appeared twice in the following paragraph, what does it mean?

Refineries in Atlantic Canada and Quebec are dependent on imported crudes and tend to process a more diverse crude slate than their counterparts in Western Canada and Ontario. These refiners have the capacity to purchase crude oil produced almost anywhere in the world and therefore have incredible flexibility in their crude buying decisions. Approximately 1/3 of crude processed in Eastern Canada and Quebec is conventional, light sweet crude and another 1/3 is medium sulphur, heavy crude oil. The remaining 1/3 is a combination of sour light, sour heavy and very heavy crude oil. The crude slate in Eastern Canada is expected to remain much more static than that in Western Canada and Ontario, as these refiners are not constrained by the quality or volume of domestic crude production.