Research on detection of trace mercury in natural gas

Author of the article:HAN Zhongxi1 , ZHANG Fengqi2 , KANG Xiaoxi3 , HAN Zhaohai4 , GE Shouguo1 , CHEN Bin2 , ZHANG Lanxin2

Author's Workplace：1. China Research Institute of Petroleum Exploration and Development, Beijing, 100083, China; 2. School of Earth Sciences and Engineering, Xian Shiyou University, Xi'an, Shaanxi, 710065, China; 3. Nangong Kangli Electronics Company Limited, Xingtai, Hebei, 051800, China; 4. PetroChina Changqing Oilfield Company No.3 Oil Production Plant, Yinchuan, Ningxia, 750006, China

Key Words：Natural gas; Trace; Mercury; Detection; Method

Abstract：Under the control of natural gas reservoir formation conditions, some natural gas may contain a certain amount of mercury vapor. When the mercury content of natural gas is high, it is easy to lead to the precipitation of liquid mercury in the process of low-temperature treatment of natural gas. Mercury is toxic and corrosive, and has caused many potential safety issues. With the development of natural gas light hydrocarbon recovery and LNG industry, the demand for the detection of mercury in natural gas is increasing, especially for the detection of trace mercury in natural gas. Although standards such as ISO 6978-2:2003 Natural gas—Determination of mercury—Part 2: Sampling of mercury by amalgamation on gold/platinum alloy and ASTM D5954-98 Standard test method for mercury sampling and measurement in natural gas by atomic absorption spectroscopy have been published for many years, their application in China is not ideal, and some key issues need to be further clarified. Therefore, the necessity of key operations such as high-pressure sampling and two-times amalgamation detection was analyzed. This research concludes that high-pressure sampling, especially at pipeline operating pressure, is necessary for the detection of trace mercury in natural gas. For super dry natural gas, the influence of interfering substances is small, the one-time amalgamation detection method would be sufficient. For less super dry natural gas, the influence of interfering substances is large, and the two-times or multiple times amalgamation detection method is necessary. The number of times of amalgamation is determined by whether the interference substance is eliminated. This research is of great significance to the improved reliability of trace mercury detection results in natural gas.