In addition, other typical responsibilities of petroleum engineers include monitoring the performance of individual wells so that necessary maintenance can be performed (usually called 'workovers'), and determining the best location for new wells in a producing field.
Petroleum engineers also work with geologists and other specialists to search for undiscovered oil and natural gas fields and evaluate the characteristics of any oil and gas fields that are found.
Another potential career path for petroleum engineers involves computer modeling and simulation of oil and natural gas fields. This involves lots of very complex mathematics and computer programming. This type of modeling is done for several reasons, including:
1) Helping guide the development of a newly discovered oil or gas field;
2) Determining how much oil and natural gas can be safely produced from an existing field without damaging the reservoir;
3) Determining the best placement for new wells, how much to produce from existing wells, and whether to close wells permanently because they are no longer worth producing from.
This is not a complete description of what kind of work is done by petroleum engineers, but I hope it gives you a better understanding of what you might do if you decide to become a petroleum engineer. Best of luck in your career choice.