SOLVED: I had a tractor that was stuck in water and kept recording path. Deleting that tractor removed the path and got FPS back to normal.
Played the game for about 35 hours. When I started my FPS was nice above 30. As I progressed with building my factories the framerate got lower and lower, now I'm around 7 FPS. The framerate is low also far away from factories and doesn't responds much to changing graphics setting. My assumption is that the factory is consuming CPU and that in turn bounds the FPS.
Edit: Tried changing settings to low and to high (on 4K), in both cases FPS is at 7. On low the GPU usage averages around 20 % and CPU around 17 %, on high GPU avarages around 50 % and CPU around 18 %.
The FPS keeps at 7 everywhere I go.
The orange line in first graph and the highlited row on the left represents Satisfactory.
Edit 2: my specs:
CPU: Intel(R) Core(TM) i7-3770S CPU @ 3.10GHz
GPU: Radeon R9 390
Mem: 16 GB