Abstract
This paper discusses the results of steady-state and transient flow simulators utilized in the design, operation, and troubleshooting of a complex multiphase pipeline network in a Saudi Arabian oilfield. The oilfield pipelines pass across a hilly terrain with sand dunes rising up to 200 meters, transporting wet crude from wells located on sabkhas (flat terrain) to three Gas Oil Separation Plants (GOSP). State-of-the-art transient multiphase flow model performance was also evaluated using pipeline slug flow tests measurements.
The results of various steady-state algorithms used for pressure drop and free-flow calculations in the Field's pipelines were found inaccurate and inconsistent. A comparison of these calculations and Field data demonstrates that they should not be used for predicting pressure drop, sizing multiphase pipelines, or designing production facilities over hilly terrain. Transient multiphase models can more accurately predict pipeline pressure drop, and optimize pipeline size. A transient multiphase model was used for simulating trunkline valves for slug flow control. Based on simulation results, plug valves were installed near trunkline outlets. The valves were found to be useful in mitigating effects of slugs into the receiving separators, thus eliminating the need for installing costly slug-catchers. Different free-flow alternatives, and crude pumping for transferring wet crude from satellite GOSP's to the Central Processing Facility (CPF) were examined. Crude pumping was found the most suitable and economical option due to large pipeline pressure drop resulting from slugs.
Transient multiphase flow continues to be highly complex. Its effects are hard to predict accurately. Pipeline pressure drop results from simulations using the latest commercially available flow models were about 20-30 % lower than Field measured values.
