Analyses of Influences on Shale Reservoirs of Wufeng-Longmaxi Formation by Overpressure in the South-eastern Part of Sichuan Basin

Key words: 
• overpressure /
• Wufeng-Longmaxi Formation /
• shale reservoirs /
• porosity /
• organic matter pores /

Abstract: There commonly exists overpressure in Wufeng-Longmaxi shales in the area with favorable preservation conditions in the south-eastern part of Sichuan Basin and the porosity of reservoirs with overpressure is higher than that of reservoirs with common or lower pressure. The studies show that during the course of evaluation, a great deal of hydrocarbons generated in organic-rich shales led to the development of overpressure system: on one side a great deal of hydrodarbons are generated and a great deal of organic pores are formed to increase the reservoir space; on the other side the overpressure system due to a great deal of hydrodarbons generated is favorable to preserve the reservoir space. The pores of shale reservoirs of Wufeng-Longmaxi Formation are dominated by plastic pores such as organic pores, clay mineral pores etc., which are easy to be compacted by overlying strata. It is considered that the existence of overpressure system can partially resist the mechanical compaction from the overlying strata to protect shale reservoirs and preserve the storage space. It is important to study the mechanism and mode of pores in shale reservoirs in Wufeng-Longmaxi Formation in Sichuan Basin for shale gas exploration and development.