Seyyed A. Hosseini

Analytical Model for CO2 Injection into Brine Aquifers-Containing Residual CH4

During CO2 injection into brine aquifers-containing residual and/or dissolved CH4, three distinct regions develop: (1) a single-phase, dry-out region around the well-bore filled with pure supercritical CO2; (2) a two-phase, two-component system containing CO2 and brine; and (3) a two-phase, two-component system containing CH4, and brine. This article extends an existing analytical solution, for pressure buildup during CO2 injection into brine aquifers, by incorporating dissolved and/or residual CH4. In this way, the solution additionally accounts for partial miscibility of the CO2–CH4–brine system and the relative permeability hysteresis associated with historic imbibition of brine and current drainage due to CO2 injection and CH4 bank development. Comparison of the analytical solution results with commercial simulator, CMG-GEM, shows excellent agreement among a range of different scenarios. The presence of residual CH4 in a brine aquifer summons two competing phenomena, (1) reduction in relative permeability (phase interference), which increases pressure buildup by reducing total mobility, and (2) increase in bulk compressibility which decreases pressure buildup of the system. If initial CH4 is dissolved (no free CH4), these effects are not as important as they are in the residual gas scenario. Relative permeability hysteresis increased the CH4 bank length (compared to non-hysteretic relative permeability), which led to further reduction in pressure buildup. The nature of relative permeability functions controls whether residual CH4 is beneficial or disadvantageous to CO2 storage capacity and injectivity in a candid brine aquifer.

A model comparison initiative for a CO2 injection field test: an introduction to Sim-SEQ

Because of the complex nature of subsurface flow and transport processes at geologic carbon storage (GCS) sites, modelers often need to implement a number of simplifying choices while building their conceptual models. Such simplifications may lead to a wide range in the predictions made by different modeling teams, even when they are modeling the same injection scenario at the same GCS site. Sim-SEQ is a new model comparison initiative with the objective to understand and quantify uncertainties arising from conceptual model choices. While code verification and benchmarking efforts have been undertaken in the past with regards to GCS, Sim-SEQ is different, in that it engages in model comparison in a broader and comprehensive sense, allowing modelers the choice of interpretation of site characterization data, boundary conditions, rock and fluid properties, etc., in addition to their choice of simulator. In Sim-SEQ, 15 different modeling teams, nine of which are from outside the USA, are engaged in building their own models for one specific CO2 injection field test site located in the southwestern part of Mississippi. The complex geology of the site, its location in the water leg of a CO2-EOR field with a strong water drive, and the presence of methane in the reservoir brine make this a challenging task, requiring the modelers to make a large number of choices about how to model various processes and properties of the system. Each model team starts with the same characterization data provided to them but uses its own conceptual models and simulators to come up with model predictions, which can be iteratively refined with the observation data provided to them at later stages. Model predictions will be compared with one another and with the observation data, allowing us to understand and quantify the model uncertainties.

The Sim-SEQ Project: Comparison of Selected Flow Models for the S-3 Site

Sim-SEQ is an international initiative on model comparison for geologic carbon sequestration, with an objective to understand and, if possible, quantify model uncertainties. Model comparison efforts in Sim-SEQ are at present focusing on one specific field test site, hereafter referred to as the Sim-SEQ Study site (or S-3 site). Within Sim-SEQ, different modeling teams are developing conceptual models of

Static and dynamic reservoir modeling for geological CO2 sequestration at Cranfield, Mississippi, U.S.A.

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Complex fluid flow revealed by monitoring CO2 injection in a fluvial formation

CO2 injection at the S-3 site. In this paper, we select five flow models of the S-3 site and provide a qualitative comparison of their attributes and predictions. These models are based on five different simulators or modeling approaches: TOUGH2/EOS7C, STOMP-CO2e, MoReS, TOUGH2-MP/ECO2N, and VESA. In addition to model-to-model comparison, we perform a limited model-to-data comparison, and illustrate how model choices impact model predictions. We conclude the paper by making recommendations for model refinement that are likely to result in less uncertainty in model predictions.

Simulating the Cranfield geological carbon sequestration project with high-resolution static models and an accurate equation of state

Geopressured–geothermal aquifers of the US Gulf Coast contain a significant amount of geothermal energy and dissolved methane. This study investigates the effect of brine reinjection on the production of heat and methane from these aquifers. First, the range of uncertainty of aquifer properties was inspected to build the reservoir model of typical aquifers. A sensitivity analysis was then performed to find favorable conditions for production with and without reinjection, and the economic criteria for both scenarios were defined. This study concludes that reinjection has several advantages, such as increasing the sustainability of production, reducing reservoir connectivity risk, and disposing of produced brine in the same formation.