Phone Interview which questioned basic principles of a drilling fluid. If you pass the phone interview, you show up to office to take a written exam; math and chemistry questions. After passing the exam with an 80 percent or better, you do a drug test; hair and urine. If you pass everything, you're hired. You are sent to a rig prior to mud school; mud school is drilling fluids training. Mud school takes about 2 months and you learn calculations, chemistry, and company products.