Enhanced oil recovery
EOR I pilot — Loudon Oil Field (Huff 'n Puff)
This immiscible CO2 EOR pilot was designed to inject CO2 into a prevalent Illinois Basin oil-bearing interval to directly measure CO2 sequestration mass, enhanced oil recovery, and CO2 injection rate.
The pilot formation was the Cypress Sandstone, a 1,500–ft deep, fine- to very fine- grained sandstone with 6–10 ft thick packages interbedded with shales. Typically this sandstone occurs as elongated bodies that may coalesce to form larger flow units; at this site, average permeability is 31 mD and average porosity is 16%. Injection and production plan follows:
- Injected CO2 as a gas into the tubing-casing annulus of an oil producing well, injection period about one week at a rate of 5–10 tons per day
- Shut in the well to allow CO2 to mix and dissolve in the oil, shut-in period one week
- Produced the well to observe CO2, hydrocarbon gas, oil, and water production; incremental oil production about 100 barrels (after two months)
Project status:
- Completed 43 tons cumulative injection
- Well returned to active oil production
Results:
- Oil production increased, rate peaked at 8 bopd with sustained oil rate of 1–2 bopd above the pre-CO2 injection rate
- Water production decreased
Monitoring, verification, and accounting:
- Conducted baseline, injection, and post-injection monitoring, including continuous in-zone pressure and temperature, gas content and liquid chemistry of the injection formation, cased-hole logging, vadose zone sampling, shallow groundwater quality monitoring, and shallow geophysical surveys
- Conducted reservoir, geochemical, and groundwater flow modeling to verify operational and field efforts
- Monitored the chemical composition of the formation brine for nearly two years after the initial injection of CO2
- Assessed the impact of the injected CO2 on the chemical and mineralogical composition of the injection formation
MVA results:
- Shallow groundwater quality has not been impacted by CO2 injection activities, based on water chemistry results
- Residential sampling was important to address concerns of an adjacent neighbor
- Vadose zone monitoring in the Illinois Basin may be limited by saturated soil conditions
- Shallow geophysical techniques may also be limited by the site infrastructure (e.g. power lines, pipelines)
