A Stochastic Model for an Active over Passive Motion Compensator for Offshore Drilling Operations

Abstract

Abstract Active over passive motion compensators provide critical position and load control for offshore drilling operations. The larger size, high cost, and complex multiphysics of the equipment and system create significant challenges to evaluate machine performance. Empirical testing of the equipment quickly becomes cost prohibitive. This paper presents a numerical and stochastic model, which may be used to evaluate the system design, optimize the equipment setup, and predict the response of the equipment, which is useful for quantitative risk analysis. The one-dimensional multi-degree of freedom model utilizes a system of non-linear differentials equations that describe the time dependent kinematic, hydraulic, pneumatic, and electrical control aspects of the active over passive motion compensator. The equations may be solved using Runge-Kutta or Adams-Bashforth-Moulton methods. A Weibull analysis of the results reduces the time series data into a set of two coefficients, which describe the characteristic value and data spread of the probability density function. Comparison of the coefficients across different equipment designs, setups, and environments reveals valuable performance information. Knowledge of the machine performance as a function of input parameters leads to better equipment designs, optimal component setup, reduced commissioning times, forecasting of system response, and more efficient operations.