Method for removing sandstone condensate gas reservoir water lock through nitrogen injection

Abstract

The invention relates to a method for removing a sandstone condensate gas reservoir water lock through nitrogen injection. The method includes the steps of the nitrogen injection initial stage, the nitrogen injection breakthrough stage, the nitrogen injection diffusion stage and the closing-in stage, wherein at the nitrogen injection initial stage, flow in a shaft and a water crest of a near-shaft region are gradually compressed through the nitrogen and are displaced towards the periphery of a well, and the injected nitrogen tongues along the top of a reservoir stratum; at the nitrogen injection breakthrough stage, the nitrogen is ceaselessly injected, and after the difference value between the pressure at the bottom of the well and the pressure of the stratum during gas injection is larger than the pressure of the water lock, the nitrogen is injected to break through a water lock barrier; at the nitrogen injection diffusion stage, the nitrogen is ceaselessly injected, the water crest on the periphery of the well is dispersed to a farther place, and the gas-phase seepage capacity is improved; at the closing-in stage, the nitrogen injection stops, the water crest is further compressed to fall, and the gas-phase seepage capacity is further improved. By injecting the high-pressure nitrogen to displace the water of the near-shaft region, communication is achieved for natural gas at a far end, and the gas-phase seepage capacity is improved; meanwhile, through the high compressibility and expansibility of the nitrogen, the good emission assisting, displacing and gas lifting effects are achieved when energy is released, and finally the gas well yield is recovered and the condensate gas reservoir recovery efficiency is improved.

Description

technical field [0001] The invention relates to a method for restoring the productivity of gas wells and improving the recovery rate of condensate gas reservoirs by injecting nitrogen into sandstone condensate gas reservoirs. Background technique [0002] Sandstone gas condensate reservoirs are vulnerable to water locking. In the process of drilling, well completion, workover and production, foreign fluids will stay in the reservoir, formation water will invade into the gas-bearing pores, etc., resulting in water lock in the reservoir. Water lock will increase the water saturation near the wellbore and increase the capillary resistance of the gas-water interface in the rock pore throat, resulting in an increase in gas phase seepage resistance and a decrease in relative permeability, resulting in a decrease in gas well productivity, or even stop blowout, which has a negative impact on condensate formation. The development of gas reservoirs has had a greater impact. [0003]...

AI Technical Summary

Problems solved by technology

Field tests have shown that the effects of acidification and surfactant injection are poor, and there are many types of dry gas, such as natural gas. The design of parameters such as the mechanism of injecting nitrogen to break water locks, injection volume, borehole time, and well opening methods in gas reservoirs is not yet clear, and there is a lack of operability in the specific implementation process

The relevant technical content of this application has not been reported

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