Modeling subsea choke valve erosion with a production-driven shock-associated degradation process

Abstract

Sand erosion in subsea components can cause serious design and production problems. Choke valves are installed at the wellheads to control the reservoir outflow and protect equipment from unusual pressure fluctuations. They suffer from erosion due to continuous exposure to the abrasive mixture of oil, gas, water, and sand. Severe degradation may cause production slowdown, leading to significant financial losses. Therefore, the capability to predict erosion rates in choke valves given a pre-determined production plan is essential for determining the choke's service life and guaranteeing system integrity. We introduce a productiondriven, shock-associated degradation model to describe the choke valve erosion. The continuous wear is modeled by a Transformed Gamma process, accounting for time- and state-dependent degradation increments. External shocks, i.e., damage caused by sand bursts, are modeled by a compound Poisson process. Both wear and shock process are governed by the production rate that defines the flow velocity inside the pipelines. We derive explicit formulas for the degradation's distribution and introduce an inference procedure based on maximum likelihood estimation. Monte Carlo simulation can be used to estimate the deterioration trend and remaining useful life.