Innovative CO 2 Injections in Carbonates and Advanced Modelling for Numerical Investigation
Abstract: CO2 geological storage in deep saline aquifers was recently developed at industrial scale mainly in sandstone formations. Experiences on CO2 injections in carbonates aquifers for permanent trapping are quite limited, mostly from US projects such as AEP Mountaineer, Michigan and Williston Basin. The behavior of fractures in carbonates plays a key role in those reservoirs in which porous matrix permeability is very poor, which drives the CO2 plume migration through the fracture network where hydromechanics and geochemical effects take place due to injection. Hontomín (Spain) is the actual on-shore injection pilot in Europe (EP Resolution of 14 January 2014), whose reservoir is comprised of fractured carbonates. Existing experiences from field scale tests conducted on site have supported to better understand the behavior of this type of reservoirs for CO2 geological storage. Innovative CO2 injection strategies are being carried out in ENOS Project (EU H2020 Programme, http://www.enos-project.eu). First results based on field tests conducted at Hontomín, and the advanced modelling developed so far will be analyzed and discussed in this article, as well as, the description of future works. The evolution of operating parameters such as flow rate, pressure and recovery term during the tests confirm the CO2 migration through the fractures.
Summary (1 min read)
- Hontomín is the actual on-shore injection pilot in Europe (EP Resolution of 14 January 2014), whose reservoir is comprised of fractured carbonates.
- The design of safe CO2 injection strategies and the understanding of trapping mechanisms in carbonates with poor matrix porosity and fluid transmissivity through the fractures are challenging matters so far.
- Initial and final values of referred parameters during CO2 injection are shown in table 1. BHP in HA well remains constant along the test what proves there is not fluid transmissivity through the seal.
- The modelling followed a sequential approach: first matching the single phase parameters such as fracture permeability during the brine injection periods and then matching the two-phase parameters such as fracture relative permeability during the brine and CO2 injection periods.
- Results from first injection tests conducted at Hontomín site within ENOS project confirmed the singularity of this reservoir where CO2 migration is through the carbonate fractures.
- On the other hand, when flow value is constant during injection the well head pressure highly increases as much CO2 is injected on site.
- As regards the period of time necessary for pressure recovery on the bottom hole during the fall-off phase, it depends on the injected fluid due to different hydraulic properties, and the cumulative amount of CO2 existing on site.
- Regarding the thermal profiles corresponding to injections, liquid CO2 phase is ensured along the tubing which corresponds with an efficient operation, reaching fluid density values close to 0,83 t/m3 at the bottom hole.
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Cites methods from "Innovative CO 2 Injections in Carbo..."
...As the approaches to elaborate and calibrate the DFN are statistically based, the results presented in this paper shall only be considered as initial and it will serve as the basis to the future full-field history matching of the CO2 and brine injection tests which will be performed within the ENOS project ....
Frequently Asked Questions (2)
Q1. What are the contributions in "Innovative co2 injections in carbonates and advanced modelling for numerical investigation" ?
First results based on field tests conducted at Hontomín, and the advanced modelling developed so far will be analyzed and discussed in this article, as well as, the description of future works.
Q2. What have the authors stated for future works in "Innovative co2 injections in carbonates and advanced modelling for numerical investigation" ?
The future modelling work shall focus upon the pressure fall-off periods which appears faster in the model than in the field.