Optimal Drilling Parameters Design Based on Single Drilling Depth Indicator in Controlled Gradient Drilling
Controlled gradient drilling technology was put forward to solve the problem of narrow pressure margins in deep water drilling. In this paper, an optimization model for optimal drilling parameters design is established for controlled gradient drilling. The established optimization model aims at achieving the longest single drilling depth, while reducing pressure difference between wellbore pressure and formation pore pressure as much as possible. It is beneficial to increase the ROP and reduce formation damage. The SQP (sequential quadratic programming) algorithm is presented to solve the optimization model. Simulation results indicate that longer single drilling depth and better drilling parameters (control variables) can be obtained by use of optimization model when the range of control variables widens. Furthermore, in case study, small bottom-hole pressure difference can be obtained by use of optimization model. In addition, the established optimization model ensured the dynamic wellbore pressure within narrow pressure margins during optimization process. It is conducive to safe and efficient drilling.
KeywordsNarrow pressure margins Controlled gradient drilling Optimization model Optimal drilling parameters Safe and efficient drilling
Project supported by the Key Program of National Natural Science Foundation of China (Project No. 51734010).
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