Parameter Prediction Method for Submarine Cuttings Piles in Offshore Drilling

Abstract

Summary The cost of offshore drilling operations can be significantly reduced by discharging drilling cuttings into the seabed. However, this leads to accumulation of cuttings piles on the seabed near the drilling site. A certain thickness of cuttings piles changes the original trend of the seabed terrain undulation condition, thus bringing potential safety hazards to the underwater installation of production manifolds. Moreover, the interaction between cuttings and ocean currents near the cuttings piles causes the geometric shape of cuttings piles to evolve over time, which makes it more difficult to accurately predict their characteristics. On the basis of the force analysis of cuttings, considering the effects of cuttings properties (cutting size, density) and ocean-current velocity on the geometric characteristic evolution of the formed cuttings piles, a continuous model for describing the evolution of the returned cuttings piles is established in this study. This model can quantitatively characterize the functional relationship between characteristics of cuttings piles and relevant parameters (current velocity, cutting size, evolution time), and predict the location and geometry characteristics of the cuttings piles evolving into a stable state in ocean currents. Comparing the measured data in laboratory experiments and at an offshore drilling field, the relative error of the model amounts to less than 10%, which demonstrates its rationality. Simulation results show that there will be significant changes in the geometry of cuttings piles before and after the evolution, in which the intensity is correlated with current velocity and cuttings size, and cuttings piles might even split into several parts under certain conditions. The simulation and analysis of the transport and deposition of cuttings returned from the wellhead on the seabed is highly significant for the guide and optimal design of underwater production manifolds.