Computation of Surge Pressure Wave Propagation During Cementation Process

Abstract

Abstract This paper presents a method of modelling surge pressures and wave propagation that can occur during well execution. The surge pressures have an impact on formations i.e. formation fracture resulting in mud losses and non-productive time. Knowing the amplitude of pressure surges in advance can lead to operation redesign to avoid losses. Pressure waves can occur at numerous points during well execution. For example, during liner operations, pressure waves can occur dart landing or plug shearing, liner hanger setting or clearing a plugged shoetrack component. It is possible that these pressure waves can create fractures in shale and sand layers i.e. when pressure wave amplitude exceeds formation fracturing limit. A physical model is built to compute pressure wave propagation through drill string, casing and open hole, to predict amplitude of pressure wave and to warn when a fracture may occur in formation to avoid mud losses and non-productive time. In the model, the continuity and energy partial differential equations are built for a cylindrical fluid element contained in an elastic hollow cylinder. Method of characteristic is applied to transfer the partial differential equations into ordinary differential equations. The ordinary differential equations are solved numerically to compute pressure distribution along well depth and in time. The physical model is implemented as a Graphical User Interface (GUI) tool to be used by drilling engineers at design phase of well to avoid losses. To date it has been used for cementing and perforating operations. Pressure wave computations are performed with the model for a field in Gulf of Mexico where mud losses have occurred, and results are presented in this paper.