Differential hydrocarbon accumulation and its influence on the formation of gas reservoirs in the Longwangmiao Formation, central Sichuan Basin

Abstract

The Longwangmiao gas reservoirs have significant differences in various structural positions in the Anyue gas field of the Sichuan Basin including diversities of pressure system, gas-water interface, bitumen content and charging time. By determining the diagenetic sequence of rocks and minerals, analyzing inclusion components by Raman spectrum, calculating capture temperature, and restoring regional tectonic evolution process, comparative analyses of the charging evolution process of liquid and gas hydrocarbon were carried out. Results show that (1) Three distinct pressure systems exist in gas reservoirs in the central Sichuan Basin. Gas-bearing zones and water-bearing zones separately distributed. The average pressures of gas reservoirs decrease gradually from north to south, and the three pressure systems have independent gas-water interfaces. (2) The initial charging temperatures of hydrocarbons varied in different gas bearing systems.The temperature during liquid hydrocarbon charging was higher in the west and lower in the east, and the accumulation evolution process was different from west to east. The charging temperature during liquid hydrocarbon cracking of gaseous hydrocarbon was higher in the east and west, and slightly lower in the middle. Based on the division of pressure zones of the Longwangmiao gas reservoir and the determination of gas-water boundary value, the distribution range of effective gas reservoirs was predicted for different gas-bearing systems, which provided guidance for further exploration and deployment.

Keywords

• raman component analysis of inclusion
• gas reservoir pressure
• differential accumulation
• longwangmiao gas reservoir
• anyue gas field
• central sichuan basin