Shell is from Oil & gas background, so they are implementing same Safety and security in IT as well. They pay well in papers but no tax saving components, as a result take home salary will be very less.
HR Can fire any employee at any time, they don't listen to anyone. Indian HRs are misusing zero tolerance policy, so they can fire employee even for not wearing seatbelt/helmets or for submitting handwritten bills etc.. there is no job security, they may ask you to leave company within hours.