System and method for flushing coal ash in coal-bed gas well by using nitrogen foam flushing fluid

Abstract

The invention relates to a system for flushing coal ash in a coal-bed gas well by using nitrogen foam flushing fluid. The system comprises a fluid preparation tank, a pump truck, a foam generator, a nitrogen making truck group, a command truck, a well control blowout gate valve, a blowout preventer, a fluid channel conversion device, a plug valve, a flowback pipe, a flowback fluid storage tank, acoal-bed gas well shaft and a well flushing operation pipe column, wherein the well control blowout gate valve is arranged at the top of the coal-bed gas well shaft; the pump truck is used for connecting the fluid preparation tank with the foam generator through a pipeline; the nitrogen making truck group is connected with the foam generator through a pipeline; the command truck is connected withthe pump truck and the nitrogen making truck group through cables; the foam generator is connected with the well control blowout gate valve; the blowout preventer is arranged at the top of the well control blowout gate valve; the fluid channel conversion device is arranged at the top of the blowout preventer; the plug valve is arranged at the top of the fluid channel conversion device; and the flowback pipe is arranged at the top of the plug valve. The system is high in ash fishing efficiency, low in flushing fluid stratum filtration loss, low in water consumption, high in ash carrying capacity of the flushing fluid, low in damage to a reservoir and high in blockage removal capacity.

Description

technical field [0001] The invention belongs to the field of oil and gas resources development, and in particular relates to a system and a method for flushing fly ash in coalbed gas wells with nitrogen foam flushing fluid. Background technique [0002] Coalbed methane reservoirs (coal rocks) have low strength and well-developed joints and fissures. During the drilling of coalbed methane wells, the coal rocks around the wellbore are damaged by drilling disturbances, forming a large number of coal rock particles. At the same time, drainage and drainage are required in the process of coalbed methane exploitation, which causes coal rock particles and fly ash in coal rocks formed during drilling to be carried into the wellbore. These coal rock particles and fly ash will block the seepage channels of water and coalbed methane after a large amount of accumulation in the wellbore, resulting in the decline of coalbed methane production or even stop production. Therefore, in the pro...

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Problems solved by technology

[0007] In view of the serious stratum leakage, large water consumption, poor economy, low efficiency (poor ash-carrying ability), long construction period, and Due to the shortcomings of serious reservoir pollution and incomplete ash removal, the present invention provides a method for flushing fly ash in coalbed methane wells with nitrogen foam flushing fluid, so as to overcome the above-mentioned problems in the methods of flushing with clean water, mechanical salvage, and the combined use of the two. Disadvantages, improve the efficiency of fly ash fishing and avoid secondary pollution of the reservoir by fishing ash

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