drillordrop wrote:pijoe1212 wrote:wm / dspp
just to reiterate the staring point of the "drain pipe" - i used that term to illustrate the principle only and not that i expect a drain pipe shaped feature. the starting point (which remains my concern) is a vertical fracture pinching out at the sides extending vertically below well bore with a low system resistance to vertical flow and high(er) resistance to horizontal flow. i would suggest that is perfectly feasible. we also know the well bores target fractures than can be seen on 3d - i.e. not small.
The issue of water breakthrough has already been studied in detail for fractured basement reservoirs, there is a link to a paper below which did a lot of work on the White Tiger Field in Vietnam.
QUOTE: The conclusion that can be drawn from the simulation study are as follows:.
- Increase in the vertical permeability [i.e., increase in anisotropy ratio (k v /k h )] leads to increase of water cut and water saturation at the producing interval without any significant effect on the oil production rate from the fractured reservoir.
- Decrease of oil production rate leads to decrease of produced water cut. The physics explanation is to the fact that at low rate, water cut is controlled by fast moving cone inside the fractures.
- Aquifer strength has a little effect on produced water cut.
- Investigation of the effective parameters is necessary to understand the mechanism of water coning in naturally fractured reservoirs. Simulation of this phenomenon helps to optimize the conditions in which the breakthrough time of water cone is delayed.
The full paper is here...
https://link.springer.com/article/10.10 ... 015-0185-7By the way, anyone found any documentation on the convertible bond yet?
That's a good read isn't it. Thank you very much for digging that out.
In this case we have a light oil and water is water. So the mobility ratio will be near-ish unity I think (correct me if I am wrong, see
https://petrowiki.org/Microscopic_effic ... lity_ratio).
If one looks at Fig 16 and Fig 17 in the Azim paper you give, then plot onto Fig 16 a 0% w/c that rises to 30% in 100-days or so, that is what we are dealing with.
My understanding from this is that they model the Daihung to have wellbore placed 250m above the OWC - do you read it that way ? So with 0.04mm fracture aperture at 8000bpd breakthrough occurs at 200d and reaches 30% at 350d.
An implication is that a 250m cone can develop in a fractured reservoir.
BUT we are dealing with something much faster than that in Lancaster.
When one considers the mobility ratio must be near unity, which means that per Fig 17 that can be discarded as the explanation for rapid breakthrough.
The conclusion I reach is that even 0.04mm fracture apertures can see a 250m cone. What happens when one runs this at 0.4mm fractures. Or at 4mm fractures. Set as per Lancaster seismic. And what OWC does one have to dial in to history match observed rates and timings.
It doesn't look good for Lancaster does it ? Nor does it look good for a perched water hypothesis ? But they said they were confident it was not rate-dependent, etc etc etc.
(Digging out the bond details is not top of my list though I recognise it is a threat. I think the reservoir is the more imminent danger)
regards, dspp