Coring the Gulf

October 22, 2015

In February 2015 the Bureau of Economic Geology’s Tip Meckel led a coring operation to the inner Texas shelf off the shore of Galveston Island.

Meckel’s team previously imaged the site in 2013 using the bureau’s high-resolution 3-D seismic technology (P-Cable). Seismic interpretations indicated a deep-seated gas chimney and identi­fied a suite of shallow seismic anomalies 10 to 40 meters below the seafloor, interpreted to be shallow free-gas accumulations.

The goal of February’s core sampling was to determine if the gas anomalies can be resolved with the fine spatial detail that is imaged in the seismic data. Twenty-three piston cores were located on and off the shallow seismic anomalies, with an average penetration depth, limited by the presence of a stiff clay layer, of 1.85 meters. The lowermost sediments from piston cores will be processed for any gas content.

Six cone penetrometer (CPT) profiles were obtained at similar depths for a subset of the piston-coring sites. CPT data provide tip resistance and friction, which can be used to infer fine-scale stratigraphy. The data set also provides important informa­tion for developing monitoring strategies for potential offshore storage of CO2 beneath state waters.