I'm going to give insight into four different types of field engineers and a 30,000' view of their day-to-day duties. Halliburton has multiple PSL's (Product Service Lines) where a field engineer in each PSL will have drastically different responsibilities. You could be a frac engineer, wireline engineer, directional drilling engineer, cement engineer, or in my case, a completion tools engineer.
Frac and wireline engineers have a somewhat similar lifestyle. They usually work 12 hour shifts, day or night, for 10 days on and 4 days off. This is field work, part of their 10 day rotation will have some office work but a majority of it will be in the field. They will need to be on location at usually 5AM and will work till 5PM when the night crew comes to replace them as they usually run under 24 hour operations.
Cement is primarily office and lab work. Though they spend a lot of time in the field initially so they understand the operational side.
Completion tools is probably the most unique PSL and is what I personally recommend as it gives you exposure to every other PSL under Halliburton. I worked with engineers in several different groups and learned a ton this way. We had weeks where we were all office work and there were some rotations where I was in the field for 10 days straight. In my role I conducted a lot of meetings with customers, planning the job in advance, providing them with a variety of results from different analysis tools (usually software programs) and then going to the well site to oversee the plan carried out for more complex jobs.
While being in the field is tough, that is where you learn the most.