I worked in the oil industry for years before retiring and learned both of these trades as well as others. However these were in small job shops of less that 10 employees. Most everyone at these small shops in the oil field had many skills. We had to, there was no telling what would come through the door. The more you knew or learned the more job security you had. Don't count on a job requiring both skills. Having more than one skill or trade will increase your ability to find employment and is always a good idea.