We just ran a 6'' Talon bit to drill horizontal - the formation is weak and we run highly overbalanced with MW 1.45 and Formate mud - geomechanics study advised high MW. SPP is limited and the HSI planned for the PDC is just 1.0 HP/in2.
Because we drill highly overbalanced ROP will be slowed down rapidly - cuttings will be held on bottom - "chip hold down" effect - for my understanding impact force and HSI would help to prevent drilling the same chips again and again - of cause not with significant ROP increase because overbalanced pressure effect is exponential -
But if we drill at 2.0m/h instead of 1.7m/h for 570m we will save 2 days. Are there any papers or publications showing that even with high overbalance (300 bar above pore pressure) HSI and impact force should be high as well or will better bit hydraulics not help to get better ROP in this case.
Following on from Rodman's advice, I'd talk to your Bit people. You have stated that the formation is 'weak' so I'd be wary of too much, well pretty much anything. I'd suggest that you are less cutting the formation as blowing it away, with all the potential issues that brings. It may be too late but I'd suggest you see how you can optimize the bit/formation/hydraulics to maximize ROP even if that produces some counter-intuitive answers.