Simulation of Multiphase Fluid-Hammer Effects During Well StartUp and Shut-In

Abstract

Summary In this study, well-known commercial software that is capable of modelingfully 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 byapplying sensitivity analysis to a typical production system, including wellcompletion, wellbore, downhole equipment (e.g., packer), and the associated surface equipment (i.e., flowline, riser, and valves). This study summarizesthe general course of key factors that worsen the fluid-hammer effects. Fluidhammer 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 adirect impact on equipment (i.e., unsetting of the packer) and may cause damageto instrumentation. This paper provides estimates of the typical ratio oftransient shock in pressure and flow rate to preconditional values, and theduration of such pressure shocks. It also proposes the best location for theshut-in valve and the length of flowline needed to reduce the fluid-hammereffects. This is a pioneering approach to integrate multiphase-flow modeling oftransient 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 toolenables the integrated approach [i.e., from sandface (bottomhole) to wellheadand topside platform accordingly], which can be applied to surface-facilitydesign and can serve as guidance in field operation to avoid hydrocarbon leakages.