Differential pressure sectional plugging process for bittern natural gas waste well

Abstract

The invention discloses a differential pressure segmented plugging process for a bittern natural gas waste well. The process comprises the steps that A), a sleeve and a blowout preventer are installedat a well mouth, and drifting is carried out; B), logging is carried out, the diameter of a wellbore and stratum fracture development data are obtained; C) a tough plug is pushed to a position belowthe lowermost stratum fracture for positioning; D) first-time front-section cement paste is injected in the portion above the plug, a drilling tool is lifted out of the cement paste liquid level, a well is closed for waiting on cement setting, the remaining front-section cement paste is injected after the first-time front-section cement paste is initially set, the front-section cement paste contains a coagulant and a lightening agent, so that the drilling tool is lifted out of the liquid level of a cement paste column, grouting channels in the wellhead blowout preventer and the drilling tool are closed, and the top surface of the front-section cement paste is positioned below all stratum fractures; and E), the drilling tool is taken out, rear-section cement paste containing a fluid loss agent, a dispersing agent and an anti-gas channeling agent is injected, and all the stratum fractures are covered. According to the differential pressure segmented plugging process for the bittern natural gas waste well, influence of a lower part dissolving cavity on plugging can be avoided, it can be guaranteed that the cement paste can be extruded into the stratum fractures, all gas and liquid channels are sealed, the expected effect is achieved, and the cement paste is saved.

Description

technical field [0001] The invention relates to a plugging process for abandoned old wells with brine. Background technique [0002] At present, after the old brine natural gas wells are abandoned, the harmful gases and liquids such as hydrogen sulfide and brine in the brine natural gas remaining in the well reach the ground through the wellbore and the cracks on the well wall, polluting the soil, surface water and air, and causing harm to the environment and people's health. Therefore, it is necessary to carry out plugging and treatment of these old wells. In the geological disaster control construction of old brine and natural gas wells, some old wells are completed with wooden casings due to their long construction time. Irregular open hole state, there is no liquid in the well or the liquid level is very low, and the well wall is extremely broken and irregular, the formation fractures are developed, the collapse is serious, and the lower dissolved cavity is large. There...

AI Technical Summary

Problems solved by technology

In the geological disaster control construction of old brine and natural gas wells, some old wells are completed with wooden casings due to their long construction time. Irregular open hole state, there is no liquid in the well or the liquid level is very low, and the well wall is extremely broken and irregular, the formation fractures are developed, the collapse is serious, and the lower dissolved cavity is large. Therefore, conventional cementing is used to seal the wellbore and shallow fractures. The well fluid enters but does not exit, not only requires a large amount of cement, but also the cement slurry cannot fill the wellbore, cracks, and dissolved cavities, which may lead to the failure of the plugging construction and fail to achieve the expected effect

Images