The telephonic round is to gather information about your background, why did you choose the role that you're in, what challenges do you face in it, what do you like and dislike about your current company and why did you apply to work with Shell.
Also, make sure you do your homework about Shell, their business and ask the interviewer a few questions.
The technical round is about your role repeated skills, real / hypothetical scenarios of how would you handle challenges, anything that you'd like to change about the way in which you handled a certain situation and lastly, why do you want to leave your current job and join Shell.
Again, ask them questions about role, company, their business, projects etc.
Leadership round is a standard leadership based questions and how do you react to stress / pressure situations?