Flow Testing Methods to Detect and Characterize Partial Blockages in Looped Subsea Flowlines

Looping subsea flowlines is one method being utilized for flow assurance. Looping allows the possibility of circulating chemicals and/or tools to remediate partial flowline blockages due to wax, paraffins, asphaltenes, hydrates, sand, and scale. This study considers if flow testing can provide an a priori knowledge of the presence and/or size of the partial blockage before remedial action is taken. The techniques developed are for single-phase liquid flow and can be applied during circulation operations in looped flowlines or in single-phase oil transportation lines. Using these models, a blockage map is created to indicate what size of blockage can be detected and what size of blockage can be characterized as to length and diameter of the restriction. Field-scale verification was obtained by placing fixed length and diameter partial blockages in the 9460-ft LSU flowloop (3.64-in. i.d.). Tests were conducted with liquid rates to 11 bpm (15,840 bbl/day) and pressures to 4000 psia.