Insight into Parameters Influencing Wash Displacement Efficiency Through CFD Modeling

Abstract

Jet-type perforate-wash-cement (P/W/C) is a relatively new well plugging technique that is more cost effective than the traditional casing milling method. ConocoPhillips has extensively used this technique in the Greater Ekofisk Area (GEA) over the last 10 years. In this method, Tubing Conveyed Perforating (TCP) guns perforate casing in the target interval before the zone is washed and a cross-sectional cement plug is installed using a specialized Bottom Hole Assembly (BHA). The BHA has nozzles in respective zones to separately spray wash fluid and cement during the operation. Tool translational (up and down movement) and rotational speeds, nozzle diameter, number of nozzles, nozzle angle, mud and cement properties, flow rates and nozzle pressure drop are the key governing parameters. In 2014, ConocoPhillips Norway launched a project to improve quality of wash and cement processes and since 2016 utilized Computational Fluid Dynamics (CFD) for parametric optimization. The analysis significantly enhanced understanding of the fundamental processes involved, enabling improvement of the existing tool and processes. The focus of this paper is on how BHA rotational speed, nozzle diameter, and nozzle angle influence wash process efficiency. Deeper insight from CFD analysis on the influence of these parameters on the wash process is discussed in more detail in this paper. Updated wash and cement procedures and parameter values were introduced in 2017 based on CFD modeling and detailed in a best practice document. To date approximately 200 successful operations have been performed as per the best practice.