ABSTRACT: X-Ray Tomographic Imaging of Gassy Marine Sediments

ORSI, THOMAS H., AUBREY L. ANDERSON, WILLIAM R. BRYANT, and CARL M. EDWARDS, Texas A&M University, Department of Oceanography, College Station, TX

Of all the possible constituents of marine sediments, few have attracted more interdisciplinary study or are of greater practical importance than gas bubbles. The key missing element in the study of gassy marine sediments, however, has been information about the characteristics of gas present in the sea floor: neither the amounts of gas nor details of its distribution within the sea floor are known. The primary obstacle has been an inability to obtain sea-floor samples that are representative of in-situ conditions.

Release of hydrostatic pressure during core retrieval permits expansion and effervescence of bubbles that alter original structures significantly. Clearly, quantitative study of gassy marine sediments requires a technique to examine their internal structure either in situ or nondestructively in the laboratory under in-situ conditions. Formidable technical difficulties, however, make in-situ investigations impractical at this time. Therefore, a major emphasis of this study will be to evaluate the usefulness of x-ray computed tomography, a powerful nondestructive diagnostic technique used extensively by the medical field, to address the latter case.

Adaptation of x-ray computed tomography to the quantitative study of marine sediments will create exciting new avenues in which to examine the geotechnical characteristics of sediment structure. Due to the nondestructive nature of CT, investigations of the structure of gassy marine sediments will be possible, a feat that previously has been unattainable. Further, CT can guide sample selection for traditional analytical methods, such as geotechnical testing and electron microscopy. The strong geological foundation established for the structural characteristics of gassy marine sediments can guide development of numerical models commonly used in offshore engineering, underwater acoustics, and marine geochemistry.

AAPG Search and Discovery Article #91014©1992 AAPG GCAGS and GC-SEPM Meeting, Jackson, Mississippi, October 21-23, 1992 (2009)