congrats to those invited for BH assessment day, here is someone's experience at d assessment:
"2 days interview. we introduced ourselves, had breakfast, then they showed us their facility center.
we had an opportunity to talk to real engineers. then we went to BH training center and there we had to do 2 tests (we had to assemble a tool and the next test was with drilling muds). then we moved to the hotel and had a case study, that was tough. then we had dinner and we had to do presentation in the night. the next morning we presented it and after breakfast we had a panel interview. then we waited about an hour and the managers told us the results."
my advice; during the presentation ensure you do well, contribute a lot and be very enthusiastic..hope this would help.