RE: Overdue RNS9 Oct 2021 13:15
Snaffleman
I’d like to know precisely the nature of the ‘formation damage’ at WN-B because surely it is a clue to the technology needed to produce gas from the Kirkham Abbey Formation. Anyone who can make this work will have the run on the existing discoveries in this part of UK land, and perhaps others offshore.
As Grey Panther noted, the moment gas and condensate separate there are two fluids in the reservoir pores and capillary forces come into play. In very tight dolomitic carbonates like WN the pore throats connecting the pore spaces are very small and flow is much easier if a single phase fluid is present. But the moment a liquid and a gas phase are present, flow is dominated by capillary pressures. The condensate becomes the ‘wet’ phase and ‘wetting’ describes the molecular bonding of the condensate liquid to the rock matrix. Wetting, and the surface forces that control wetting, are absolutely fundamental to reservoir engineering, mainly due to capillary effects. This is why a tight rock ‘wet’ with condensate can become a barrier to the passage of gas.
Conversely, in an oil reservoir saturated with dissolved gas, if gas is allowed to ‘bubble’ in the pores, when pressure is reduced by too much drawdown, the gas bubbles create a barrier to oil flow.
In the case of WN-B it could be that the spent acid - essentially water - became the (un-intended) wet phase deep into the near well-bore zone, which effectively became a barrier to both condensate and gas inflow from the reservoir itself. In Sachin’s words ‘formation damage’.
Overall, it appears the Kirkham Abbey Formation at WN is no more friendly to the reservoir engineer than the many similar, but non-commercial discoveries in the area. Acidisation hasn’t worked.
So, question for Raithlin/Reabold specialist advisors - What is the plan for WN-A?
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