DRA Chemical - A Game Changer in Reducing GHG Emission by Reduction of Pumping Power for Long Crude Oil Pipelines

Abstract

Abstract Use of Drag Reducing Agent (DRA) chemical is well established in oil & gas industry to reduce frictional pressure drop in long pipelines thereby increasing operating capacity. In any brownfield facility, drag reduction strategy not only helps to minimize capital investment by retaining existing pumps and pipelines for increased capacities during short-term flow excursions, but also saves substantial GHG emission by reducing pumping power. The paper highlights ADNOC Offshores’ three existing main crude oil pipelines where DRA chemical is being injected to overcome hydraulic limitations while maintaining business continuity as a primary objective, but this also provides extensive benefits in terms of emission reduction. A detailed analysis on DRA performance, optimum injection rate based on operational experience, reduction in DRA efficiency experienced due to change in crude oil flow due to shear or mixing impact at downstream is included in this paper. DRA chemical is injected in an optimized manner to gain overall pressure drop benefit in three existing crude oil pipelines, 14"x10 km, 12"x18 km and 42"x65 km. The crude oil (32-34 °API, 5-10% water cut) pipelines operate in liquid phase. More than 60% drag reduction (pressure drop reduction) is achieved with 50 ppm injection rate. Efficacy of DRA injection is verified from vast experience based on last 5 years’ operating data. DRA performance based on actual operating data shows drag reduction is very high at initial concentration (around 45-50% drag reduction is possible with 15-20 ppm DRA dosage), subsequently the incremental drag reduction is at a slow rate and reaches almost saturation point at 60-70 ppm dosage rate to achieve upto 70% drag reduction. The operational findings also demonstrate that there is an efficiency drop of DRA if the chemical is injected from an upstream location where in between there is mixing of fluid and due to which the flow pattern is lost. For Pipeline-3, there is around 13-18% drag efficiency loss observed due to mixing effect because of dosing DRA from upstream Platform-1/2. The injection removes hydraulic bottlenecks to meet high production target and at the same time saving huge pumping power due to high reduction of pipeline pressure drop. Overall pumping power saving ≈ 25 to 30 MWh/day, which is equivalent to around 160 mmscf/year reduced fuel gas consumption amounting to 12,500 to 14,400 tons of CO2e saving per year. The findings demonstrate use of drag reducing chemicals not only as a tool for capacity enhancement of the existing pipelines, but also for substantial GHG emission savings. The study findings are highly encouraging, this shows that even for any greenfield project of new pipelines, proper techno-economic analysis can be conducted to consider DRA as a base case design option with reduced pipeline size/low head pumps with substantial GHG saving.