Liwei Zhang, Ph.D.

Institute of Rock and Soil Mechanics
Chinese Academy of Sciences

Thurs., Sept. 26, 3:45 pm
Sidney & Marian Green Classroom (3550 MEK)

Free and open to the public

ABSTRACT: This presentation demonstrates a CT scanning and image analysis workflow to characterize wellbore cement degradation under geologic CO2 storage (GCS) conditions. The workflow includes acquisition of raw CT images of the cement sample (before and after exposure to CO2); application of 3D rigid registration to align all CT image frames; acquisition of grayscale intensity difference images; application of noise filtering technique on grayscale intensity difference images to obtain images with good quality; acquisition of 3D pore structure change of the cement sample after CO2 exposure from grayscale intensity difference images, showing degradation of wellbore cement. To demonstrate an application of the workflow, an experiment of reaction between CO2 and wellbore cement under GCS conditions was conducted and the wellbore cement samples used in the experiment went through aforementioned CT scanning and image analysis procedures. CT image analysis results demonstrate a region with increased porosity in the exterior of the cement sample (Zone 1) and a region with decreased porosity next to Zone I due to CaCO3 precipitation (Zone 2). Next to Zone 2, a region with increased porosity due to Ca(OH)2 and C-S-H dissolution (Zone 3) was observed. In summary, this study proves feasibility to use 3-D CT scanning and CT image analysis techniques to investigate CO2-induced degradation of wellbore cement.

BIO: Dr. Rekha Liwei Zhang is a professor at Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. He received his M.S. degree from Duke University in 2010 and his Ph.D. degree from Carnegie Mellon University in 2013. From 2013 to 2017, he was a postdoctoral research associate at National Energy Technology Laboratory, U.S. DOE. In July 2017, he was recruited by Institute of Rock and Soil Mechanics, Chinese Academy of Sciences as a full professor. Prof. Liwei Zhang’s research has been focused on experimental and numerical studies on reactive transport of fluid in porous media and mineral dissolution/precipitation processes. Specific research areas include subsurface mineral dissolution and precipitation under geologic carbon storage conditions, leaching behavior of metal ions from ores and fly ash under high concentration CO2, and evolution of pore structure of wellbore cement under corrosive environment. His research activities have resulted in 1 book, 4 book chapters and more than 60 journal articles and conference proceedings.