Characterization of wellbore asphaltene deposition in well Gaotan-1 in Junggar Basin, China

Abstract

Gaotan-1 is the first high-yield well explored in the southern margin of Junggar Basin, China, which is a major breakthrough in the oil exploration for Xinjiang Oilfield Company. The well produced high-quality light crude oil with very low sulfur content and total acid number. However, serious sedimentation occurred in the wellbore during production, which seriously affects production. In this paper, the sediments from Gaotan-1 were separated into organic soluble and inorganic solid fractions. The organic compounds were characterized by high resolution mass spectrometry and high temperature gas chromatography. It was found that the organic matter was rich in asphaltenes with very high molecular condensation. The high condensation compounds should be formed in the high temperature reservoir environment, which was extracted by the supercritical fluid formed by the light hydrocarbons under the ultra-high temperature and pressure. Due to its super-dissolving ability, the high-condensation hydrocarbons and asphaltenes are brought out of the reservoir, and deposit gradually mixed with silty sand on the wall of the wellbore as the temperature and pressure dropped in the process of oil exploitation.