FAR SP, page-46

Q#1) you r correct there. Such is the beauty/challenge of these fan plays, the sands could suddenyl pinch out a few kms away &/or appear. So the best way to identify them is on a high res seis & once a field is producing u could shoot 4D (time lapse) to see which part is starting to deplete & may need reinjection (gas/water). The first well simply serves as a proff of concept, ie drilled & encountered all targets (+/- any surprises) as well presence of HC's.

Q#2) Change in API: I believe the oil quality isn't from a single unit within a sand packages encountered. One could still blend the end product or isolate a low API zone behind the casing, when they go to production.

Jubilee field has 2 sands Upper Mahogany & Lwr Mg'ny Sandstone (UMSST & LMSST) currently producing from 9 oil wells, 8 water wells & 2 gas injectors. The net thickness is different in all the wells. Avg is 48m with a low-high of 23-98m in 2 diff wells. So the same will apply at Fan-1. A future well drilled up/down dip will have diff net pay. Funnily the M#1 well was the only one with a high net of 95m, the others r in the 40's. Still no issues with production (bar sand finings & acid jobs to imprv flowrates). Besides these 2 sands at Jubilee, there's the deeper play in the undevelpd sector where M#3, M#4, MD1, MD2 were drilled. So the net:gross component varies vastly across the field as does the oil quality, average API is betwn 36-37 there. The deeper sand was 18-23 API. U could chk this on the KOS releases all crystal clear.
As for Beer, I cant come up with a depositional model (as WhiteNoise pointed out as well). I believe that's where they think the entire kitchen is located. A fan usually has a channel, terrace, multiple lobes & Beer sands must b sitting in a very old cut channel/canyon. Hope this helps.