Numerical Simulations of High CO2 Content Flows in Production Wells, Flowlines and Risers

Abstract

Abstract There are several challenges associated to the pre-salt development at the Santos basin, such as long distances from the coast, low temperature reservoirs, high pressures, high water depth, among others. Additional aspects contributing to the complex production scenario are related to fluid characteristics and flow assurance. In particular, the high CO2 content in the dissolved gas is an important characteristic that should be also analyzed, because CO2 is not only a heavy component, when compared to lighter components present in the gas phase, but has also a high Joule-Thomson coefficient. This affects pressure drop and specially the mixture cooling behavior during decompression. The cooling effect is expected to be strong at high production rates. Thus, the objective of the present work is to evaluate these effects under present and future production scenarios, taking into account increasing CO2 contents due to re-injection strategies. Two different field configurations were investigated and a variety of operating conditions was used, along with real and model fluids ranging from 5% to 50% CO2 content (molar basis). PVT data for the model fluids with high CO2 content were generated by a simulated swelling test with CO2 of an existing mixture with lower CO2 content. A parametric study was carried out aiming at investigating primarily the total pressure and temperature drop in the pipeline when the total CO2 content of the mixture is increased. Furthermore, variation of the fluid properties along the well, flowline and riser was evaluated. Results are also discussed in view of the impact of increasing CO2 contents and the challenges experienced during simulation of such flows.