A mathematical casing cutting model and operation parameters optimization of a large-diameter deepwater hydraulic cutter

An important part of subsea abandonment operations on gas and oil wellheads is the use of hydraulic cutters. To save time and guarantee security of an operation, so it is desirable to predict their operating parameters with a mathematical model. To determine the relations between cutting force, structure, and operating parameters of a hydraulic cutter to optimize its design and operation, the casing cutting mechanism of a hydraulic cutter was analyzed. Cutting parameters were analyzed based on the characteristics of real-life cutting by a hydraulic cutter, and a mathematical casing cutting model of a large-diameter hydraulic cutter in deep water was established according to the classic empirical formulas of cutting and grinding forces. The model parameters were defined, and the mathematical model was verified by combining it with site data from abandonment operations. An optimization mathematical model of cutting parameters was also established for cutting efficiency, operation parameters were optimized by particle swarm optimization, and the pump output was also optimized. Results indicate that casing cutting is a combination of cutting and grinding. Cutting forces calculated by the mathematical casing cutting model were within 7% of actual cutting forces. The requirements of engineering applications were met. We found that cutting efficiency is greatly improved by adopting an optimal speed and feed, so the research results are pertinent and important to real-life practice.