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Absolutely nailed it RNSTranslater. Couldnât have put it better myself ;)
RNSTranslator
Thanks for that detailed explanation.
Found it very interesting as I am sure some other posters will.
thanks for taking the time.
Ron
"I remember Dr.Trice saying oil could not be fed from below in an F.B. reservoir so it is hard to see how you could have a low zone of oil then a zone of water then oil in the main reservoir?"
As usual its the casual use of words that leads to misunderstandings.
Yes that is true that in fractured basement reservoirs the oil cannot come from DIRECTLY below, there is no source rock below to provide the oil. It can and does come from a depth deeper than the reservoir, as oil is lighter than water and finds its way to the shallowest accumulation point. In this case the source rock is deeper but its on either side of the basement ridge so it has to travel both laterally and upwards. The reason for CA talking about the thickness is that they are referring to what is often called the Transition Zone, that is the zone where the oil goes from a high saturation say 90% plus oil and 10% or less water over a distance to to a place where the saturation of oil is much lower or the oil is completely absent. In a Sandstone reservoir this transition zone can be from a few feet to 10's of feet depending on the reservoir type and quality, a long transition zone in a sandstone reservoir can mean a few things, either a poor reservoir or perhaps a reservoir that has subsequently leaked and so the OWC has moved higher, leaving behind some residual oil.
In basement reservoirs its a function of the interconnectivity of the fractures in the rock, this is not easily predictable nor easily measurable. So the migrating oil coming in from the sides and travelling upwards can get caught in "dead end fractures" that don't actually connect up into the main reservoir fracture network (think of a cul de sac). These will still show oil beneath the main OWC but are likely to be minor , indeed this is perched oil (!) within what is essentially the acquifer, just as the so called perched water was supposedly a small volume of water trapped within the oil column. Perched water is far more difficult to explain as the oil being lighter that water would in effect displace the water downwards through bouyancy.. perched water is not impossible, just unusual. The other explanation for oil below the contact is that the trap has at some point leaked and the OWC has risen leaving behind some residual or locally trapped oil. My view is that CA are confusing what they think is a long transition zone (unusual) with oil shows from either perched oil or a paleo oil column. Either way the evidence is pretty strong that the OWC is at the new level and the stuff below is really just "noise". They are entitled to their opinion of course, but I'm not sure many professionals would agree or bet money on their case being correct.
Exerts from Energy Voice 21/09/2020
One of Hurricane Energyâs institutional investors has said the oil firmâs recent technical review, which included a huge downgrade to reserves and resources, was âpersuasive but not conclusiveâ.
Guernsey-based Crystal Amber said it believed âsignificant volumesâ may be present below the revised oil-water contact and that rapid initial pressure decline was âcommonly exhibitedâ in fractured basement reservoirs like Hurricaneâs Lancaster field.
Earlier this month, Hurricaneâs technical committee revealed phase one of the Lancaster development, west of Shetland, would only produce 16 million barrels of oil, of which 9.4m remained, down from initial forecasts of 37.3m.
The company also reset total remaining resource estimates for Lancaster and the adjacent Lincoln field to about 100m barrels of oil, from more than 1 billion stated in a competent personâs report by RPS Energy in 2017.
Crystal Amber, which describes itself as an AIM-listed activist fund, claimed: âThe zone now believed to contain residual oil below the oil water contact is very thick, whereas we would have expected an abrupt change in oil saturation at the free water level.
âTherefore, the fund believes that significant volumes of oil may be present below the revised oil water contact at 1,330 metres.â
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C.A. are saying that they believe a significant oil volume may exist below the revised oil water contact level.
They would hardly be saying this if they did not have good reason to believe it to be likely.
I remember Dr.Trice saying oil could not be fed from below in an F.B. reservoir so it is hard to see how you could have a low zone of oil then a zone of water then oil in the main reservoir?
Does this mean that C.A. are inferring that the revised OWC level has been estimated at too high a level. They would also be inferring that the oil resources estimate is too low.
It raises the question of how C.A. obtained the information to come to these possible scenarios. I do not think they have been mentioned elsewhere.
The comment âwe would have expected an abrupt change in oil saturation at the free water levelâ is beyond me. Maybe someone can expand on this.
Now we have the sudden departure of a main shareholder with board members Kerogen.
Could there be some kind of connection in these events? Who knows but we may soon find out.
Ron