15. EOR from depleted reservoirs through CO2 storage
The general objectives of this project were:
- to prepare an inventory of the candidate reservoirs in the North Sea region (and also Dutch reservoirs) that could be considered for a CO2 storage with an EOR objective;
- to identify and understand complex physical processes involved in multiphase fluid migration, interactions, mobilisations and displacements taking place during CO2 storage in depleted oil reservoirs.
Inventory of candidate reservoirs in the North Sea suitable for CO2-EOR: To estimate the total CO2-EOR potential in the UK and Norwegian sector of the North, a techno-economical model for CO2 injection into oil reservoirs and aquifers has been used in a scenario were many of the most feasible prospective water flooded fields are included. The techno-economical model consist of a CO2 transportation module and an EOR module that is integrated with an economical model that calculates investment costs and running costs both for injection into oil reservoirs and aquifers.
Pore-scale CO2/fluid interactions, experiments and modelling: Understanding the fluid flow and recovery mechanisms at the pore scale provides vital information needed for interpretation of core and field scales displacements. Different processes involved in EOR from depleted oil reservoirs during CO2 storage were investigated. Visualization experiments in micromodels were conducted under reservoir conditions, using dead oil and reconstituted brine: CO2 was injected into these models under various conditions.
Core-scale investigation and quantification CO2/rock/fluid interactions: Accurate interfacial tension measurement were performed up to 1400 bar by using the pendant drop experimental set-up.
Core flood experiments were then carried out to further quantify the process and to generate data for modelling and simulation purposes. The efficiency of CO2 secondary and tertiary injections has been studied, in a limestone sample (Lavoux), under in-situ reservoir conditions (oil-wet sample, 60°C, 180 bar).
CO2 injection performance and diffusion was also investigated in modelled fractured reservoirs: CO2 was injected either as pure CO2, CO2-WAG (Water Alternating Gas) or CO2-foam. In particular, the effect of foaming agent on the rate of CO2 diffusion in the matrix blocks was studied and quantified.
Effect of effective permeability on oil recovery in pure CO2 flooding and CO2-foam flooding at Swi=0.5.
Remaining oil saturation after 55.56 days with pure CO2 flooding and CO2-foam flooding in fractured models with Swi = 0.5 and Keff = 20mD.