::The Extra-heavy oil article just redirects to the Heavy oil article, and what this says is Heavy crude oil or extra heavy crude oil is any type of crude oil which does not flow easily. It is referred to as "heavy" because its density or specific gravity is higher than that of light crude oil. Heavy crude oil has been defined as any liquid petroleum with an API gravity less than 20°.[1] Physical properties that differ between heavy crudes lighter grades include higher viscosity and specific gravity, as well as heavier molecular composition. Extra heavy oil is defined with a gravity of less than 10° API(i.e. with density greater than 1000 kg/m3 or, equivalently, a specific gravity greater than 1) and a reservoir viscosity of no more than 10,000 centipoises. 
 ::Although Heavy oil is significantly less dense than Extra-Heavy, most Canadian bitumen has about the same density as Venezuelan Extra-heavy oil, so the essential difference between the Canadian oil sands and the Venezuelan oil sands is one of viscosity. From an Imperial Oil document: Bitumen has been defined by various sources as crude oil with a dynamic viscosity at reservoir conditions of more than 10,000 centipoise. Canadian “bitumen” supply is more loosely accepted as production from the Athabasca, Wabasca, Peace River and Cold Lake oil-sands deposits. The majority of the oil produced from these deposits has an API gravity of between 8° and 12° and a reservoir viscosity of over 10,000 centipoise although small volumes have higher API gravities and lower viscosities. 
 ::So in reality the quality of the oil in the Canadian and Venezuelan oil sands is about the same, it is just that Bitumen has a higher viscosity than Extra-heavy oil. The Canadians deal with this by injecting steam to reduce the viscosity in producing wells, and blending it with light oil/condensate to reduce the viscosity to move it through pipelines. The Venezuelans often do the same since, even though their oil is less viscous, it helps mitigate their production and transportation problems. 

 ::While the Orinoco Belt has its own article, so does the Athabasca oil sands. The Orinoco Belt consists of large deposits of extra heavy crude (oil sands), known as the Orinoco Oil Sands or the Orinoco Tar Sands. The Orinoco Tar Sands are known to be one of the largest, behind that of the Athabasca Oil Sands in Alberta, Canada. 
 ::Note that they call it the "Orinoco Oil Sands" or "Orinoco Tar Sands", because that it is what it is.There is far more information available. about the Canadian oil sands (especially in the Athabasca oil sands article) than the Venezuelan oil sands, but I don't think this is a good reason to delete the Venezuelan oil sands from the oil sands article. The Venezuelan information just needs to be expanded, as does the Orinoco Belt article.