Frio Brine Sequestration Pilot in the Texas Gulf Coast
Dr. Susan D.
Hovorka and Paul R. Knox
The purpose of the project described here is to develop a suitable site and conduct initial experiments. We have designed a project that will quickly produce information and experience by (1) recycling existing infrastructure, (2) building on known technologies and regulatory processes for deep-well waste disposal and CO2-enhanced oil recovery (CO2-EOR), (3) selecting a geologically isolated injection site suitable for experiments with small volumes of injected CO2 without risk of impact to adjacent properties, and (4) building on the earlier phase of our projects and of the GEOSEQ project. This site complements and extends the results of other planned and ongoing sequestration experiments in EOR settings or future large-scale settings by providing a site for initial experiments in a typical high-injectivity sandstone area of high emissions.
The Bureau of Economic Geology at The University of Texas at Austin is leading a research team to create an onshore U.S. CO2 sequestration field demonstration in a brine formation setting. The selected site is in Liberty County northeast of Houston, Texas. Texas American Resources Company, our field partner, is providing access to several idle wells in a 50-year-old oil field that will be recompleted in a nonproductive Frio sandstone interval. CO2 will be trucked to the site and injected into a high-permeability upper Frio sandstone. Sandia Technologies and Transpetco will provide waste and CO2 injection expertise. Team partners from the GEOSEQ project, including researchers from Lawrence Berkeley National Lab, Lawrence Livermore National Lab, and Oak Ridge National Lab, will conduct a series of field monitoring experiments before, during, and after CO2 injection. These experiments will test the effectiveness of a spectrum of CO2 monitoring techniques and compare results to validate the methods.
The project includes a planning phase, preinjection field activities, injection experiments, postproject synthesis, reporting, technology transfer, and stakeholder involvement. Planning phase characterization and modeling are currently under way. Permitting and preinjection field activities, including well workovers, recompletions, hydrologic characterization of the injection interval, and baseline preinjection monitoring, will begin during late 2002. Injection will be completed within 100 days, followed by a year of monitoring and assessment.
Figure 1. Within a 7-county area (16,700 km2) centered on Houston, Texas, 10 power plants released an estimated 32 million metric tons of CO2 in 1996. In addition, more than 100 chemical manufacturing plants and refineries in the same area continue to release an unknown additional volume of CO2. Directly beneath most of these emitters are high-capacity sandstones that are most likely a suitable site for sequestration of CO2.
The study site provides for a rapid start-up using existing infrastructure and low risk of adverse impacts because the injection will be made into a hydrologically isolated reservoir compartment of a well-known geologic structure. Injection will occur in the Frio Formation beneath the thick Anahuac shale (fig. 2), and lateral migration of CO2 will be limited by structural compartmentalization along faulting associated with the setting on the flank of a salt dome. Idle wells will be recompleted in a brine-bearing interval 1,000 m above the oil reservoir. A small volume of CO2 will be trucked to the site and injected into a 10-m-thick transmissive sandstone. An updip well will also be completed for monitoring CO2 migration. Response will be monitored both within the injection sandstone bed and in overlying thin sandstone separated from the injection sandstone by a few meters of shale. Safety is implicit in the experiment design, which is focused on intensive monitoring. Additional safety will be provided by using contractors experienced in CO2 injection and hazardous waste disposal. An existing 3-D seismic survey and wireline well logs are providing input data for planning phase modeling. Extensive field-scale data, brine chemistry, and core available for the Frio Formation in the region are being collected and used to guide the study.
Figure 2. The experiment will use a fault compartment adjacent to a salt dome to limit the potential for CO2 escape.
Analytical tools being evaluated for use include construction of a geologic and geotechnical database and 3-D realization; modeling of plume geometry using TOUGH2 code2,3; pressure buildup and falloff analysis of data collected in the injection and observation wells; single-well, crosswell, tomographic, and crosswell downhole seismic imaging to characterize the injection interval and to monitor plume geometry; electrical resistance tomography (ERT) to monitor plume geometry; downhole logging; reactive transport modeling; assessment of compartmentalization from production history; monitoring CO2 phases with natural stable isotopes; monitoring using introduced tracers SF6, perfluorocarbons (or PFC's), and noble gases; modeling of geophysical response; and geochemical modeling.
2. Pruess, K., and Garcia, J. (in press). Env. Geol.
3. Pruess, K., Oldenburg, C., and Moridis, G. (1999). TOUGH2 user's guide, version 2.0: Berkeley, CA, Lawrence Berkeley National Laboratory Report LBNL-43134, November.