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Integrating Fluid Migration Interpretation with High-Resolution 3-D Seismic: Application for Miocene CO2 Storage Prospects, Inner Texas Shelf


The tremendous volumes (Megaton/yr) of anthropogenic CO2 ultimately anticipated for industrial-scale carbon capture and storage (CCS) suggest that basin-scale perspectives are needed. Geologic fluid histories at a basin scale are likely to provide exceptional insight relevant for evaluating regional CO2 storage opportunities. An ongoing study characterizing prospective CO2 storage sites in the inner Texas shelf (focused on the Texas State waters off southern Galveston Island) utilizes such an approach by integrating historical hydrocarbon accumulation information with fluid inclusion data from well cuttings and regional structural mapping using 3D seismic data. The region has both commercial gas accumulations and abundant dry holes in a complex structural setting involving salt diapirs and growth faults. A novel aspect of the study is the targeted acquisition of high-resolution 3D (HR3D) seismic data of the interval overlying storage prospects. HR3D seismic data complement existing commercial 3D data by linking the shallow and deep geologic systems for unified interpretation. We have acquired HR3D data over both deep and shallow salt bodies off San Luis Pass, Texas, where two key wells provide fluid inclusion stratigraphy via processed cuttings. Interpretation of the shallow seismic data has focused on the identification of potential gas migration pathways, faulting, stratigraphic complexities in the overburden, as well as any indications of shallow re-accumulation or natural seafloor seepage. Any identification of prior geologic seepage or potential migration pathways is valuable for risking long-term containment of engineered CO2 storage prospects. This multi-year project utilizes the novel “P-Cable” acquisition system (twelve 25-m long streamers with 12.5 m spacing), targeting the upper 1 sec TWTT using sources ranging from 90 to 210 cubic inches. One survey was conducted in 2012, one in 2013, and one is planned for 2014. Survey areas are approximately 50 sq. km. with dominant frequencies typically 100-150 Hz providing vertical resolution of perhaps 2-3 meters. Such HR3D data can be used to: 1) characterize shallow storage formations prior to initiating a storage project; 2) characterize he overburden by providing stratigraphic and structural information for risking long-term storage and avoiding unintended migration, and 3) may also serve as a baseline for future time-lapse (4D) surveys to demonstrate containment or identify non-containment.