Output does not increase beyond certain point despite increased fracture area?

[softwareengineerprogrammer]

Question submitted by user via email:

I'm continuing to play around with the frac area with the Fervo example attempting to quantify the effect on output. I've tried all sorts of combinations (see my quick excel screenshot) and no matter the increase beyond a certain point I get the same output ~2.15MW (and heat extraction from the reservoir ~24.5 MW). So my question is, shouldn't the output increase with an increase in the available frac area? Even if the flow rate remains the same in all cases I'd think there would be more heat extraction with the increase in heat transfer surface area. I feel like I'm either missing something that is limiting the output or it is as simple as the frac area isn't tied to the production flow rate in the calcs so heat extraction and avg output remain the same (and frac area would then just affect the reservoir volume and heat content available?). I'm thinking the latter but would appreciate an explanation.

[softwareengineerprogrammer]

Answer from @kfbeckers:

The heat extraction (and corresponding power production) depends on flow rate and production temperature. In your case, increasing the fracture area no longer results in an increase in production temperature as there is sufficient heat transfer area already and the fluid heats up to the reservoir temperature (which is the maximum you can get to).

Hence, the only way to further increase power production would be to increase flow rate or increase the reservoir temperature.

Increasing the fracture area can help with preventing thermal decline but in your scenario you have sufficient area already allowing for constant production temperature over the lifetime.

In the 160 m by 160 m fracture area we included as example, you will see thermal decline after a few years.