Curious well control situation (using Water based KCL mud).

Good Day.

I have a question for any folks on drilling fluids or drilling through coal stringers. On a current well we are drilling we are using a water based drilling fluid with a minimum of 3-4% KCL. There are some polymer additives as well but essentially this is a water based mud. There are several coal stringers at a depth of 8300' and we have a shoe depth of 8100'. There was an influx a few days ago and the mud density was increased from 10.9 ppg to 11.4 ppg and well was killed with no issue. We suspect that the influx came from the coal zone after a wiper trip but the strange part is that the influx is acting like it is in Oil based Mud and not water based. An influx can be taken and only a very minor gain is noticed (0.2 bbls)but when it gets close to surface is when it really starts breaking out just like a gas influx in OBM. I have taken numerous kicks with both water based mud and OBM and am aware how gas reacts in each type of fluid. But in this case, we have what we suspect is gas coming from a coal stringer and even though utilizing a water based mud, it is acting like a gas influx would in OBM. Also when we trip out of the hole, gas seems to migrate into the annulus and our hole fill displacement is over what is calculated when we trip out but once we trip back in the hole we've had to shut in the well and circulate out gas. Obvious solution would be to increase mud density but we will incur losses with a higher mud density. I was just wondering if anyone has ran into this before because it's the first time I have seen this. Any info would be a great help.

Thanks.

Thanks. 

4 Answer(s)

Support Spread

We need the support of our members to keep our forum online. If you find the information on spread useful please consider a donation

Donate