I wrote this just a couple of hours ago, but let me repeat it, because it is so important (one of the many untrue myths where many people will tell you nonsense!):
Whether the partners are in O&G or not is practically irrelevant for your chances of success! If you are targeting MBB, then please make sure you are not wasting your time on building up a lot of industry knowledge! On the normal consulting track, MBBs are NOT hiring for kowledge! This is one of the most fundamental principles of how McKinsey, BCG, and Bain have built their entire assessment methodology!
The reason is that MBB firms are only interested in your principle skills (such as problem solving skills, communication skills, capacity to influence, maturity etc.). If these principle skills are given, then all relevant sector or functional knowledge will be absorbed on the job and via structured training curriculums at the firms! When I recruitied for McKinsey and BCG, my guiding principle was: "I need to hire the right brains and personalities. I am not interested in their business knowlege, since if they have the right capabilities, they will be able to quickly absorb the relevant knowledge anyway". This is the reason why MBB firms insist on the point that your major doesn't play a role in whether you can get an offer or not.
Again: On the normal consulting track, MBBs are NOT hiring for kowledge! They are hiring for skills!