RE: Stu29 Jul 2020 19:18
Branson,
"As I've continued to assert, I don't see how it can be coning from the aquifer, so it can only be perched, but as to the volume.... I have no idea. But by producing from 7z it will (should) allow 6 to produce from the other direction (i.e towards the sealing fault adjacent to Lincoln), which is of course a limited distance, compared to the potential of extending all the way to Halifax from the 7z, although I would hope it's not perched water all that way... Really, I'm just thinking aloud..."
I agree, that using ESP - you have more control over the reservoir around 7z. E.g. you can control the fluids from affecting 6 by controlling the pump pressure.
The explanation that the 7 ESP allows 6 to pull from the "other direction" is false. The 6 will still pull radially. But the ESP on 7 limits the flow of the fluids (or the fluid dynamics) from affecting the pull around the 6 well.
Regarding the volume, I'm not too sure either. I haven't looked into it in depth of the distance and length. But Hurricane have stated that the Lancaster reserves could be connected to 500 mmboe.. and that's bound to have huge amounts of trapped water in as well. How much of it is connected to the current 7z and 6 wells? Who knows. At some point, the productivity of these wells will deplete and new wells will have to be drilled - targetting new fractures within the connected network.
"I dont see how it can be coning from the aquifer either. As we have been told by HUR the water rate is higher when the well is restarted after having bern stopped. If there was coning from below this could not happen as the cone would drop down away from the wellbore when flow is stopped due to gravity as the viscous forces holding it up in the first place greatly reduces and water is heavier than oil. Also as I understand coning is more of a problem with highly viscous oils (which Lancaster oil is not)! Not an expert so just my take on it (an honest opinion)."
Okay so if Lancaster was conventional well, the above is true. When the well is shut in, the cone will drop down and the aquifer would be flat, or would form a meniscus with the well walls. As the poster clarified, water is more dense than oil so due to gravity (Stokes' Law), the water will "sink" below the oil given time to settle. So when you do restart the flow, the coning would not take place immediately, and you will produce almost 100% oil. And afterwards coning will slowly take effect - pulling water along with oil as oil is extracted.
In fractured basement, it's completely different. The whole basement will have some sort of pressure differential (as opposed to a conventional well where the pressure is all the same) throughout the whole network.
Think of it like a straw, when you're slurping fanta, the fanta is drawn up the straw. Until you reopen your mouth, that fanta will stay siphoned up the straw (due to the pressure difference between your mouth and the atmosphere where the fanta is).
Sli
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