Dynamic Underbalanced Drilling technique

摘要: Overbalanced drilling (OBD) is known to be cheap and simple but formation damage reduced rate of penetration (ROP) are some its disadvantages. However, underbalanced (UBD) minimizes achieve high ROP, it expensive, complex can't applied in many cases. This application introduces a new technique that incorporates the advantages avoids disadvantages these systems referred as Dynamic Underbalanced Drilling (DUBD). In DUBD pressure drop at environ bit, below around, created restored normal above bit such conditions requires minor modifications design drill bit. Thus zone located around underbalance dominated while rest hole overbalanced. The anticipated cost this nearly zero expected save much costs. provide higher ROP may exceed ordinary UBD cases, so saves time, reduce damage, costs (cheaper than OBD) enables gathering information about reservoir drilling. can logging testing addition, problems, particularly time sensitive overcome problems UBD. Furthermore, used safely over pressurized shale salt formations, where not recommended.