| Popis: |
A dynamic simulation model of an injection riser/pipeline/well for injection of shipped liquefied CO2 was set up using the multiphase flow simulator OLGA. Furthermore, the topside offloading process was modelled using HYSYS. The models were applied for case studies using parameters from the existing Sn∅hvit and Sleipner CO2 injection wells and reservoirs. The study quantified effects related to flow capacity (pump/compressor requirements and line sizing of the riser, pipeline and well), freezing, hydrate formation, phase change and heat transfer in the offloading and injection system. With an available injection pump discharge pressure of about 120 bar, the injection capacities were predicted to about 275 kg/s on Sn∅hvit and 400 kg/s on Sleipner when assuming 7” ID tubing size in the well and 700 m flowline length. In the base case scenario with a 700 m buried pipeline and injection temperature of -53°C (this storage temperature on the ship, at a pressure of 7-8 bar had been selected for optimum transport capacity) there is a high risk of unwanted hydrate formation and freezing in the formation and on the outer surface of the riser and pipeline. The bottomhole temperatures were predicted as low as -38 and -46°C on Sn∅hvit and Sleipner respectively when injecting at pump design rate, far beneath expected hydrate and freezing temperature of 10-12 °C and -1.9°C (in salt water) respectively. Thus heating, either by topside heat exchangers and/or by utilizing the warmer sea water (5°C) via a longer injection pipeline is required to avoid problems. An alternative storage condition at -20°C and 20 bar was proposed and simulated to reduce energy requirements due to heating and pressurization at the ship. The heating power was reduced by 18 MW while topside pumping power was reduced by 0.5 MW in this case. |
