First round interview was an on-campus interview, with some general personality questions. A few weeks later I was invited to a 2-day second-round interview. On the first day we were taken to one of the refinery sites where we just toured the area and were treated to dinner. The next day was a day-long interview at their headquarters in Houston. The interview consisted of about 7 one-on-one interviews, which were with people from various divisions in the company (VP of marketing, control systems, etc.) I think most of the questions were geared towards personality really, there weren't any technical questions.