The oil from the 2010 Deepwater Horizon spill in the Gulf of Mexico was documented by shoreline assessment teams as stranding on 1,773 km of shoreline. Beaches comprised 50.8%, marshes 44.9%, and other shoreline types 4.3% of the oiled shoreline. Shoreline cleanup activities were authorized on 660 km, or 73.3% of oiled beaches and up to 71 km, or 8.9% of oiled marshes and associated habitats. One year after the spill began, oil remained on 847 km; two years later, oil remained on 687 km, though at much lesser degrees of oiling. For example, shorelines characterized as heavily oiled went from a maximum of 360 km, to 22.4 km one year later, and to 6.4 km two years later. Shoreline cleanup has been conducted to meet habitat-specific cleanup endpoints and will continue until all oiled shoreline segments meet endpoints. The entire shoreline cleanup program has been managed under the Shoreline Cleanup Assessment Technique (SCAT) Program, which is a systematic, objective, and inclusive process to collect data on shoreline oiling conditions and support decision making on appropriate cleanup methods and endpoints. It was a particularly valuable and effective process during such a complex spill.
the program were to (1) determine the feasibility of gas injection into hydrate-bearing sand reservoirs and (2) observe reservoir response upon subsequent flowback in order to assess the potential for CO 2 exchange for CH 4 in naturally occurring gas hydrate reservoirs. Initial modeling determined that no feasible means of injection of pure CO 2 was likely, given the presence of free water in the reservoir. Laboratory and numerical modeling studies indicated that the injection of a mixture of CO 2 and N 2 offered the best potential for gas injection and exchange. The test featured the following primary operational phases: (1) injection of a gaseous phase mixture of CO 2 , N 2 , and chemical tracers; (2) flowback conducted at downhole pressures above the stability threshold for native CH 4 hydrate; and (3) an extended (30-days) flowback at pressures near, and then below, the stability threshold of native CH 4 hydrate. The test findings indicate that the formation of a range of mixed-gas hydrates resulted in a net exchange of CO 2 for CH 4 in the reservoir, although the complexity of the subsurface environment renders the nature, extent, and efficiency of the exchange reaction uncertain. The next steps in the evaluation of exchange technology should feature multiple well applications; however, such field test programs will require extensive preparatory experimental and numerical modeling studies and will likely be a secondary priority to further field testing of production through depressurization. Additional insights gained from the field program include the following: (1) gas hydrate destabilization is self-limiting, dispelling any notion of the potential for uncontrolled destabilization; (2) gas hydrate test wells must be carefully designed to enable rapid remediation of wellbore blockages that will occur during any cessation in operations; (3) sand production during hydrate production likely can be managed through standard engineering controls; and (4) reservoir heat exchange during depressurization was more favorable than expectedmitigating concerns for near-wellbore freezing and enabling consideration of more aggressive pressure reduction.
In STOMP V4.0, a separate mode containing an evaporation model as a boundary condition on the upper surface of the computation domain has been included. This mode, STOMP-WAE-B (Water-Air-Energy-Barriers) can be viewed as an extension of the STOMP-WAE (Water-Air-Energy) mode. The extension provides the needed scientific tool to design and evaluate barriers. The model calculates water mass, air mass, and thermal energy across a boundary surface and water transport between the subsurface v and atmosphere. The STOMP-WAE-B addendum (Ward et al. 2005) provides a detailed description of this mode. This version of STOMP includes the recently Pacific Northwest National Laboratory developed batch geochemistry solution module ECKEChem (Equilibrium-Conservation-Kinetic Equation Chemistry). The ECKEChem batch chemistry module was developed in a fashion that would allow its implementation into all operational modes of the STOMP simulator, making it a more versatile chemistry component. Additionally, this approach allows for verification of the ECKEChem module against more classical reactive transport problems involving aqueous systems. Currently, the ECKEChem package has been implemented in the STOMP-W-R and STOMP-WCS-R modes. The fundamental objective in developing the ECKEChem module was to embody a systematic procedure for converting geochemical systems for mixed equilibrium and kinetic reactions into a system of non-linear equations. This objective has been realized through a recently developed general paradigm for modeling reactive chemicals in batch systems, which has been coded into a preprocessor for BIOGEOCHEM. To couple this processor to the STOMP simulator a conversion program, BioGeoChemTo, was written in Perl that reads the preprocessor output and converts it into STOMP simulator input format. Details of the ECKEChem module can be found in White and McGrail (2005). A third major addition to this version of the simulator is the potential to conduct parallel simulations. These versions of the simulator are written in pure FORTRAN 90 with imbedded directives that are interpreted by a FORTRAN preprocessor. vi This work was partly supported by the Remediation and Closure Science Project funded through the U.S. Department of Energy's (DOE's) Richland Operations Office. The continued development of the STOMP simulator in its sequential and parallel implementations has been funded by the Laboratory (PNNL) Directed Research and Development (LDRD) program at the PNNL. In particular, development of a scalable implementation has been funded through the Computational Science and Engineering Initiative and development of new operational modes for modeling carbon dioxide sequestration has been supported through the Carbon Management Initiative. The LDRD at the PNNL is a productive and efficient program that develops technical capabilities for solving complex technical problems that are important to DOE and to the nation. DOE Order 413.2A sets forth the DOE's LDRD policy and guidelines for DOE multiprogram laboratories and author...
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