In some situation, where you drill with mud weight that is very close to balance condition (near formation pressure) and you don’t have much room to weight up due to fracture gradient limitation, from the well control perspective, you may need to drill one stand, then circulate bottom up and perform flow check. If everything is static, you can go ahead and drilling. Moreover, you need to look at the peak gas after going back to drill because it indicates how well of mud weight is. If you don’t see any gas peak, it means that your mud weight at the static condition is good. However, if you see any gas peak while drilling but it does not come from formations that you are drilling, this situation indicates that you don’t have or just enough mud weight to control the well in the static condition. You can check where the gas coming from by using a lag stroke calculation.
Why do I say like this?
The reason is that when you are in the static condition, you will lose the Equivalent Circulating Density (ECD) and if you are at almost balance condition, you will possibly have a chance to let wellbore influx coming.
For this case, increasing mud weight a little bit will help you reduce risk of taking kick while drilling. However, before increasing the mud weight, you need to make sure that with new mud density, the new ECD will not cause the formation to break down.
Let’s talk further about tripping out of the hole.
In the case of drilling with near balance condition and you don’t have an option to weight up, when you trip out of hole, you may need to pumping out or backreaming out.
You may wonder why I suggest like this. The reason is that if you tripping out as per a normal practice, you create the swab effect that will reduce hydrostatic pressure of the wellbore. Since you are in near balance condition, you will have high chance to take kick while tripping.
Pumping out or backreaming out will ensure that you have hole full all the time and eliminate swabbing effect. The drawback of doing these operations are time consuming, dirty on the rig floor, etc.
This is my experience which you may or may not agree with. However, I would like to share with you. Any ideas are always welcome.
Reference book: Well Control Books