Texas Offshore Miocene Project, Task 3

Capacity Estimates

Task 3 provides improved capacity estimates both for regionally prospective Miocene sequestration targets (i.e., the sandstone reservoirs most likely to receive CO₂ in the near-term). Based on our previous experience providing the Department of Energy's National Carbon Sequestration Database and Geographic Information System (NATCARB) with regional capacity data, we are providing NATCARB with updated capacity estimates for the offshore State lands. This work includes data from Task 2.

The basin-scale static capacity estimation process identifies target geologic storage units (GSU), and then quantitatively integrates porosity over unit thickness and GSU area to calculate fluid-filled pore-volume. Estimated efficiency of occupancy and CO₂ density at reservoir conditions are used to calculate the static CO₂ storage capacity. CO₂ densities were calculated from compiled pressure and temperature data (example shown below) to constrain expectations for CCS.

Basin-scale static capacity is analogous to a ‘resource estimate’ used to estimate in-place hydrocarbon volume in petroleum basins, and represents ‘high-side’ potential that will likely shrink with further geological characterization. Our estimates show that The Gulf of Mexico Basin has world-class geological sequestration potential. Cenozoic rocks have best potential. Using NATCARB assumptions, the total capacity is 559 Gt (left). Using NATCARB assumptions, the Gulf of Mexico Offshore Texas Miocene has a total capacity of 86 Gt (right). We are adding detail to this estimate by calculating capacity in several Lower and Middle Miocene stratigraphic intervals that are the most likely CCS candidates. This effort is part of a ‘CO₂ Play Atlas’ for the Miocene in offshore Texas State waters detailed under Task 2.

In order to improve static estimates, we are streamlining workflows, improving GIS-to-workstation compatibility, refining and simplifying CO₂ density calculations, creating workstation grid math models, and adding a dissolution factor to capacity estimate workflows. Work has just been completed on updates to the 2001 brine database with these new data in current ACRGIS formats. Click here to link to the updated brine database.

The next step will be to compare static capacity estimates to dynamic capacity estimates. The dynamic estimates will result from dynamic models for CO₂ injection (i.e., a geologic model that considers the fluid flow dynamics and pressure evolution with CO₂ injection over a given time). Dynamic models differ most significantly from static models in that they consider the dimension of time.

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