Steady State and Dynamic Flow Assurance Model of Spiking Nafusah NGL into 16" Wafa Mellitah Pipeline

Abstract In connection with the North Hamad field development project in Libya, Nafusah Oil Operations (NOO) are investigating the option of spiking natural gas liquid (NGL) from North Hamada central production facilities (CPF) into the 16″ oil pipeline from Wafa Desert to the Wafa Coastal. OLGA simulation software was used to build a pipeline model of the planned 106km North Hamada 6" NGL export pipeline and the existing 16" Wafa-Mellitah Oil Pipeline. The aim of the flow assurance analysis was to confirm the capacity of the Wafa-Mellitah line through assessing the effect of both the additional North Hamada NGL and the impact of varying ratios of Wafa Oil/Condensate/NGL in combination with North Hamada condensate. From the steady state cases results, the hydraulic profiles confirmed that there are no operational issues expected when North Hamada production is introduced into 16" pipeline. Transient cases considering valve closures at two locations (Wafa Coastal and line valve station LVS 10) were carried out. For the transient case considering fast valve closure during peak flow the pressure spikes were found to be very low; (maximum initial spike of 2.5 bar followed by peaks and troughs of < 0.5bar). The LVS10 valve closure case showed that the pressure surge largely dissipates (reducing from 3 bar to 1 bar) before it reaches the Wafa Desert facility. In addition, the transient case considering sudden loss of production at Wafa Desert showed that pressures in the line do not drop below bubble point when the shut-off valve at Wafa Coast is tripped within 15mins.