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Introduction

CCSsim is an integrated simulation platform for CO₂ injection that couples a transient two-phase wellbore model with a reservoir simulator.

Why Coupled Simulation?​

During CO₂ injection, the wellbore and reservoir are tightly linked. Changes in reservoir pressure propagate back to the wellbore, altering the flowing pressure profile, phase behaviour, and injection rate. Conversely, transient events at the surface — such as a sudden valve closure or compressor trip — send pressure waves down the wellbore that reach the formation within seconds.

Simulating either domain in isolation requires assumptions about the other. A coupled approach removes these assumptions by solving both domains simultaneously, exchanging boundary conditions at the sandface at every time step.

Platform Overview​

The platform supports three simulation modes:

  • Standalone Wellbore — Full transient wellbore simulation with analytical injectivity boundary conditions
  • Standalone Reservoir — Reservoir simulation with source/sink wells
  • Coupled — Full wellbore + reservoir coupling

Physical Models​

The wellbore simulator solves a homogeneous equilibrium model (HEM) for two-phase CO₂ flow, capturing:

  • Compressible two-phase flow with phase transition
  • Thermodynamic properties from CoolProp (Span–Wagner equation of state)
  • Heat transfer between the fluid, tubing, casing, cement, and surrounding formation
  • Variable wellbore geometry (diameter changes, deviation surveys)