EGU24-2815, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Degradation pathways and mechanisms of oilwell cement exposed to H2S under high temperatures

Liwei Zhang1,2, Yue Yin1,2, kaiyuan Mei3,4, Xiaowei Cheng3,4, Yan Wang1,2, and Hanwen Wang1,2
Liwei Zhang et al.
  • 1State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
  • 2University of Chinese Academy of Sciences, Beijing, 100049, China
  • 3State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, 610500, China
  • 4School of New Energy and Materials, Southwest Petroleum University, Chengdu, 610500, China

The extraction of geothermal energy faces the hazard of H2S, a highly toxic and strongly corrosive gas. H2S exposure can lead to the failure of oilwell cement, decreased extraction efficiency, and even pose serious risks to operational personnels near the wellsite. High temperature is a prominent environmental feature in geothermal resource extraction. However, current research works primarily focus on the corrosion effects of H2S on cement at moderate to low temperatures. This study utilizes Class G oilwell cement to conduct corrosion experiments of cement by H2S under high temperature in a H2S-rich reaction vessel. The impact of H2S on the structure, chemical composition, and mechanical strength of oilwell cement is analyzed via SEM-EDS, XRD, nanoindentation tests, and unconfined compressive strength tests. The results indicate a reduction in compressive strength for cement samples corroded by H2S. The surface nano-hardness and elastic modulus of cement samples decrease while the internal values of nano-hardness and elastic modulus significantly increase. Under the corrosion of H2S, the structure of cement is characterized by a yellow and black surface layer and stratified cracks. The external surface of the cement exhibits a yellow color due to the formation of pyrite (FeS2), while internally, pyrrhotite (FeS) and gypsum (CaSO4.2H2O) are generated.

How to cite: Zhang, L., Yin, Y., Mei, K., Cheng, X., Wang, Y., and Wang, H.: Degradation pathways and mechanisms of oilwell cement exposed to H2S under high temperatures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2815,, 2024.