The HR contacts you if you've been shortlisted for the application process. There's a written test that consists of basic arithmetic, logic, chemistry and English language questions. If you pass the written test, you'll be invited for the interview process, they never hire experienced personnel so don't bother reading up on anything associated with drilling fluids. They usually ask the typical behavioral interview questions. They are big on humility and endurance (cos the pay is poor & they want ascertain how well you'll swallow that) If you get through this successfully, your employment letter follows usually a week later.