The Approach of Pressure Enthalpy Phase Diagram in Supercritical CO2 Pipeline Design

Abstract

Abstract The numerical modeling of carbon capture, utilization and storage (CCUS) systems can present a large amount of challenges. Mixtures with high CO2 content demand special attention regarding the thermodynamic and hydrodynamic modeling, especially if the system’s pressure and temperature operational conditions reach values below the critical point, leading to a two-phase flow. In this paper, a base case for a typical onshore injection well was proposed to numerically investigate different operational conditions, including steady-state and transient scenarios. Different analyses have been made using ALFAsim, a 1D multiphase flow simulator developed by ESSS (ESSS, 2019). Parametric analyses were performed on steady-state scenarios to investigate the optimum pipeline and wellbore diameters respecting the erosional velocity of American Petroleum Institute (API). Also, a transient scenario was simulated using a formulation based on pressure-enthalpy (PH), leading to an energy conservation equation with enthalpy as primary variable, and the use of PH fluid properties table, generated in RF-DAP FASE, a fluid analysis and simulation software (ESSS, 2022). The objective of these analyses is to show that high CO2 content mixtures add complexity to the simulations, mainly if the operational conditions lead to the development of a second phase. The parametric study could address the optimum pipeline and wellbore diameters design with respect to the system’s regulation requirements. Furthermore, the transient analysis shows a formation of vapor and liquid phases on a CO2 mixture during a shut-in, which could be considered crucial information to properly design the materials and equipment of the system.