Eagle Ford SuperEORTM
The Eagle Ford shale play of south Texas has varying production, from dry gas in the deeper south to black oil in the north. The majority of shale oil development has been focused in the volatile oil window and the rich gas condensate area of the play.
The 33 EOR projects are almost all located in the volatile oil areas.
The SuperEORTM shale oil EOR process can be applied in the volatile oil, black oil and rich gas condensate areas of the Eagle Ford, to provide increased oil recoveries of more than 350% of primary EUR. Greatest oil increases will be achieved in the volatile oil and black oil areas, where the amount of oil in place per acre-foot of shale is greatest.
Extensive modeling of SuperEORTM has been conducted in the volatile oil portion of the western Eagle Ford shale play. The modeling was conducted on wells that had been operated under both primary (pressure depletion) and natural gas HnP. The natural gas HnP project had been conducted for more than one year, following more than 3 years of primary production. The natural gas HnP project experienced problems with injected gas migrating through fractures and away to offset wells, precluding design pressure buildup. Offset well water injection pressure maintenance was projected to mitigate gas migration and improve EOR oil recovery to 20-30% more than primary.
The graph below compares the recovery of oil from a single stage of one of the Eagle Ford shale wells that had been operated under natural gas HnP EOR. The projected oil recovery via SuperEORTM was based on a maximum injection BHP of 6000 psig, which is about 300 psi below initial reservoir pressure and below the pressure where injected gas began to migrate to offset wells.
Modeling of the SuperEORTM process was then conducted at a range of lower maximum bottomhole injection pressures to determine the ability of the SuperEORTM process to recover oil. As shown in the graph below, there is little loss in oil recovery with lower maximum bottomhole injection pressures, even as low as 1500 psig.
Core testing of the SuperEORTM process on Eagle Ford shale core was conducted, and compositional simulation modeling of the core tests confirms key well compositional modeling parameters. The Eagle Ford shale core used has two distinct mineralogies with different porosities and permeabilities.
The core tests were conducted at two maximum injection pressures, 3000 psig and 5000 psig, with nearly identical results. One of the graphs from the core tests, showing cumulative oil recovery versus injection cycle, is shown below.
The core tests confirm the ability of the SuperEORTM process to rapidly and efficiently recover large amounts of oil from the low permeability, low porosity Eagle Ford shale.