Ann: Cuba, Block 9 - Mobilisation Commenced, page-234

@Vince120 thx for the pick up. This was at the Amistad objective depth (>1500mD). And going by what @afawcett father said (which i agree with) - it means the API of the oil in this (Amistad) section is likely to be higher than 15deg API.

The samples i was referring to in my post were above the Amistad - in the Bonus section. I could only go by my own observations of weathered oil/petroleum on drill cuttings and settling tanks and that stuff to me looked medium to light API (think of weathered diesel). They showed us some pictures of what in my opinion looked like heavier oils, emulsified with drill mud, when they were in the Marti and had to flare off...

As for weathering. imo heavy oils are the result of degradation of the light ends in the original oil accumulation. but my thoughts on oil genesis differ from most. I am in agreement however that the key to preservation of light fractions is the ability for the formation to "hermetically seal" the oil from biologic and chemical/physical degradation of the light ends. Whilst logic dictates hermetic sealing is more likely to happen deeper down, there is nothing to say that you wont find lighter HCs higher up...as in the bonus section...esp in karst reservoirs such as this where permeability is a lot more haphazard and does not follow laminar, sedimentary layer cake patterns.

The other thing to remember is that Cuba is a seismically active area. If you think fraccing is "disruptive " and can enhance permeability and create new flow paths in the sub surface, multiply that by 10 million when it comes to earthquakes.

And lastly, in karst reservoirs, net pay imo is a number to which i attach "secondary" importance from the point of view of how much oil is present. The number that interests me more is the oil column and the reservoir rock type.