Q4. A well 10000 ft deep is completed with a 7 casing 32 lb/ft. The well was produced with a 27/8 EUE 6.5 lb/ft, N-80 tubing string into a packer (polished bore 3.25) at a depth of 10000 ft. Initially, the tubing and casing were filled with 9 ppg brine with a surface pressure of 500 psi for both tubing and casing. During the production, tubing is displaced with 30 oAPI oil with a surface pressure of 1000 psi and casing pressure of 500 psi.