Composition and Origin of Surface Casing Fluids in a Major US Oil- and Gas-Producing Region.

Fluids leaked from oil and gas wells often originate from their surface casing─a steel pipe installed beneath the deepest underlying source of potable groundwater that serves as the final barrier around the well system. In this study, we analyze a regulatory dataset of surface casing geochemical samples collected from 2573 wells in northeastern Colorado─the only known publicly available dataset of its kind. Thermogenic gas was present in the surface casings of 96.2% of wells with gas samples. Regulatory records indicate that 73.3% of these wells were constructed to isolate the formation from which the gas originated with cement. This suggests that gas migration into the surface casing annulus predominantly occurs through compromised barriers (e.g., steel casings or cement seals), indicative of extensive integrity issues in the region. Water was collected from 22.6% of sampled surface casings. Benzene, toluene, ethylbenzene, and xylenes were detected in 99.7% of surface casing water samples tested for these compounds, which may be due to the presence of leaked oil, natural gas condensate, or oil-based drilling mud. Our findings demonstrate the value of incorporating surface casing geochemical analysis in well integrity monitoring programs to identify integrity issues and focus leak mitigation efforts.

Production, purification, and characterization of a fusion protein of carbonic anhydrase from Neisseria gonorrhoeae and cellulose binding domain from Clostridium thermocellum.

Carbon dioxide capture technologies have the potential to become an important climate change mitigation option through sequestration of gaseous CO2. A new concept for CO2 capture involves use of immobilized carbonic anhydrase (CA) that catalyzes the reversible hydration of CO2 to HCO3(-) and H+. Cost-efficient production of the enzyme and an inexpensive immobilization system are critical for development of economically feasible CA-based CO2 capture processes. An artificial, bifunctional enzyme containing CA from Neisseria gonorrhoeae and a cellulose binding domain (CBD) from Clostridium thermocellum was constructed with a His6 tag. The chimeric enzyme exhibited both CA activity and CBD binding affinity. This fusion enzyme is of particular interest due to its binding affinity for cellulose and retained CA activity, which could serve as the basis for improved technology to capture CO2 from flue gasses.