In this study, well-known commercial software that is capable of modeling fully transient multiphase flow in wellbore and pipeline has been used to characterize the fluid-hammer effects of well shut-in and startup on the coupled subsurface and surface systems. The original work was performed by applying sensitivity analysis to a typical production system, including well completion, wellbore, downhole equipment (e.g., packer), and the associated surface equipment (i.e., flowline, riser, and valves). This study summarizes the general course of key factors that worsen the fluid-hammer effects. Fluid hammer is also known as water hammer, a shock wave produced by the sudden stoppage of, or reduction in, fluid flow.
Field operations, such as pressure-transient analysis, facility maintenance, and workover, require a well shut-in process. For a typical production system, the resultant sudden rises in pressure can be critical because they have a direct impact on equipment (i.e., unsetting of the packer) and may cause damage to instrumentation. This paper provides estimates of the typical ratio of transient shock in pressure and flow rate to preconditional values, and the duration of such pressure shocks. It also proposes the best location for the shut-in valve and the length of flowline needed to reduce the fluid-hammer effects.
This is a pioneering approach to integrate multiphase-flow modeling of transient fluid-hammer effects by targeting flow-assurance issues. The software used in the study is a fully transient, commercial flow-assurance simulator, and it has been used extensively for well-dynamics studies. The selected tool enables the integrated approach [i.e., from sandface (bottomhole) to wellhead and topside platform, accordingly], which can be applied to surface-facility design and can serve as guidance in field operations to avoid hydrocarbon leakages.