Modeling the discharge of cuttings and drilling fluids in a deep-water environment

Discharge models allow the prediction of the potential impact associated with drilling activities based on estimates of the initial spatial extent and thickness of accumulations on the seabed. As such, they are a valuable tool for both the oil industry and regulatory agencies. In this study we present the use of the Offshore Operators Committee Mud and Produced Water Discharge Model (OOC Model) in modeling the discharge of drilling activities in a deep-water environment, from a well located in the Campos Basin, offshore Brazil, at a depth of around 900 m. Field and discharge data collected during the drilling and discharge activities allowed us to carry out a modeling based on real data, that is, hindcast modeling. The verification of the model was made by comparing the hindcast modeling results with field observations. Discharges from both riserless and riser drilling were modeled. The riserless drilling was performed with seawater and water-based fluid (WBF), and riser drilling with non-aqueous fluid (NAF). According to model estimates, the deposits with greater thickness (∼66.5 cm) were those from the riserless phase. Maximum estimated thickness for the discharge of NAF cuttings was 0.76 cm. The comparison of modeling results with field observations showed that the estimates of both the area affected by the deposits and maximum thickness are satisfactory. The configuration of the affected area is harder to predict because small uncertainties, mainly related to the discharge activity itself, introduce a significant error. Thicknesses predicted from real data by hindcast modeling agree with estimates provided by forecast modeling presented by other authors. This means that, in areas where there is certain knowledge of the hydrodynamics, the OOC Model can be a valuable tool to determine the degree of potential impact associated with drilling activities.