ELECTRON MICROPROBE ANAYLSIS OF LOWER MORROW SANDSTONE, WOODWARD COUNTY, OKLAHOMA

This project was part of a course in Electron Microprobe Analysis taught at Oklahoma State University. The goal was to analyze a core plug from the Morrow sandstone, Woodward County, Oklahoma to evaluate its potential as a reservoir rock. The research was conducted by two undergraduates collaborating with a graduate student to assist with a Master's thesis. The electron microprobe was used to examine the core plug's cement, porosity, permeability, and general composition. Identifying these characteristics helps to determine if the site is a potential reservoir. With the use of an electron microprobe, we hope to find valuable information that would help in future production processes. The Morrow Sandstone is Pennsylvanian, located in the Northern shelf of the Anadarko Basin situated above the Chester Limestone and below the Atoka Limestone. The core was taken from the Lower Morrow, which is more sandstone oriented. During the class, the core was imaged using backscattered and secondary electrons. An EDS spectrum determined that the rock consisted mainly of clay minerals and quartz, and smaller amounts of pyrite and copper. X-ray element maps of Fe and Ca were generated to identify elemental distributions within the material. Zoned calcite appeared to fill pore spaces surrounding larger quartz grains. The rock in general had 9.6% porosity, but the calcite and pyrite cement affects the permeability. It was determined that there was sufficient porosity in the sample, but the permeability was not high enough to be a potential reservoir. During field trips taken in this course and discussions with industry petroleum geologists, the electron microprobe does not appear to be a regularly used tool in hydrocarbon research. However, the instrument offers the ability for compositional analyses, relative porosity measurements, and identifying minerals that could be problematic for production.