Abstract:

Overpressure plays an important role in oil and gas exploration. Pressure transfer with gas charging is a dominant overpressure mechanism in reservoirs.  Because of the tremendous difference in gas solubility and compressibility between formation water and oil, there are different pressure evolutions in the aquifer and the oil layer. In this paper pressure changes caused by methane filling in reservoirs with different kinds of initial pore were simulated.  And the quantitative relationship between volume of charged methane and overpressure was established. Then the influencing factors of pressure evolution during gas chargingwere analyzed.The results indicate the following aspects:gas charging could cause increase of pressure in reservoirs; pressue evolution paths are different with different initial pore fluids; strong overpressure is easier to form in aquifer than in oil-bearing formation; in the same sealing condition, it is easier to form ovepressure in shallow strata than in deep strata as well as in high tempeature basin than in low temperature basin.

Key words: reservoir, gas charging, overpressure, quantitative model, influencing factor