Having to deal with the shale instability is the critical issue....

Having to deal with the shale instability is the critical issue. This well has a great advantage compared to M-1 because it is vertical or near vertical, whereas M-1 had about 30 degrees inclination.

if the mud weight is too low there is potential for hole collapse, especially in deviated wells, however if the mud weight is increased too much there's a real issue with formation damage as well as increasing the risk of differential sticking and in the extreme case high mud loss, which is a risk to well control. Casing the well is only way to secure hole stability, so the longer the hole is left open the more risky the situation.

I am sure that there are situations that no matter how well the mud chemistry is fine tuned to avoid shale instability, certain combinations of high wellbore stress, pore pressure, mud weight (and for deviated wells. well direction (azimuth) and deviation angle), will make it difficult to avoid hole instability issues over a prolonged period of time. Having MDT pre tests and fluid samples is important, but I hope all goes to plan.