STOMP-CO2 Simulator Development, Applications, and Enhancements
Advanced features of STOMP-CO2
Modeling efforts at PNNL have focused on developing and maintaining a state-of-the-art tool for field-scale simulation. PNNL’s code STOMP (Subsurface Transport Over Multiple Phases), developed over the past two decades, has been applied to a wide range of subsurface problems. These problems include groundwater contaminant transport and remediation, evaluation of the long-term fate of alternative waste disposal forms and integrity of waste disposal facilities, subsurface migration of non-aqueous phase liquids, and development of engineered barriers to limit subsurface recharge at contaminated sites. In the past several years a new operational mode of STOMP—STOMP-CO2—was developed to simulate the subsurface injection and long-term storage of carbon dioxide (CO2) in deep subsurface reservoirs (see carbon storage applications and capability enhancements ). The STOMP family of codes is subject to rigorous quality assurance control processes and is approved by the U. S. Department of Energy to support environmental management decisions. A number of short courses have been conducted around the country and internationally to train users in the correct application of the software system.
Because of its powerful capabilities, STOMP-CO2 is now being used in a variety of application contexts related to carbon storage. Under the National Risk Assessment Partnership, it is being used to gain an understanding of the potential risks of leakage of injected CO2 through the caprock formations that separate underground reservoirs from groundwater aquifers and the ground surface. The code is also being used to support design and interpretive analyses for pilot-scale CO2 injection tests at a number of field sites around the nation. Finally, the U.S. Environmental Protection Agency has selected STOMP-CO2 (within the Geologic Sequestration Software Suite [GS3] environment) to support its regulatory evaluation of Class VI well permit applications which govern the deep injection of CO2.
PNNL’s Laboratory Directed Research and Development (LDRD) investment to expand the capabilities of the STOMP-CO2 code has resulted in several key capability enhancements: 1) the ability to simulate the reactive flow of subsurface fluids including multiple gas phases (co-sequestration), 2) the incorporation of models of coupled fluid flow and reservoir mechanical response (geomechanics), and 3) the simulation of CO2 and brine injection for conventional and unconventional enhanced-oil-recovery (EOR) techniques.
Another version of STOMP was also recently developed to simulate the production of methane hydrates—a vast and largely untapped potential source of natural gas—using a gas-molecule exchange concept that originated at PNNL, whereby a mixture of CO2 and nitrogen is injected into the subsurface to release the methane.