Apparently drugs effect oil rig staff drastically, send a circ asking all drug taking staff to rehab.
Check activity on all staff.
If one of your staff in production is slacking in some way you may not be producing enough barrels check your production to see where the problm may lie.
Once you have done this give us a shout if nothing changes iover the next week
Drugs affect everyone drastically. They're just more prominent in rigs because the workers are generally much much closer to the extremely high stat cap or are slightly underneath it.
The higher on the cap you are the more drugs you'd be able to take before having a more negative effect. Drugs still = very bad, but they're even worse relatively when players with 'low' stats use them (again, 'low' here being relative to the position they are working... due to drugs giving a passive reduction to work stats)
Also, one thing to bear in mind... popularity isn't a factor in profit... it's a comparative stat to how well you're performing relative to the top company. My popularity has been down this week (Even though my profits are currently going up) just because the rig in the #1 spot has profits that are increasing faster than mine, so relative to them I am not performing as well (hence lower popularity).
Another thing to note with rigs is that not all positions are independent of each other (bug?), if your salesmen are inactive then for whatever reason your oil production will decline, and also if your producers are inactive then sales go down. All employees need to be continuously active for the others to perform at their best. (It's not as bad as it was in the old system where it used to be damn near 100% losses due to single inactives, but I have noticed production/profit losses near 5-10% when a single employee is inactive, even in areas that shouldn't relate to them)
Also... NET income 40m+ WITH advertising? Do you mean gross? As not even I get 40m net profit daily with the best 18 man rig, paying 0 on advertising, did you even pay your employees?