Method and equipment for reducing pollution through nitrogen foam fracturing of coal-bed gas well of low-pressure and low-permeability reservoir

Abstract

The invention relates to a nitrogen foam fracturing technology of a coal-bed gas well of a low-pressure and low-permeability reservoir. In the fracturing process, the low-pressure and low-permeability reservoir is easier to damage. According to a method, high-quality and high-efficiency nitrogen foam of which the mass is 75 percent is adopted for sand-carrying fracturing, the liquid injection quantity of nitrogen foam fracturing is small, the sand-carrying capacity is high, and the de-filtration capacity is high, so that the damage to the low-pressure and low-permeability reservoir is reduced; after the fracturing is completed, an open-flow oil nozzle of which the size is 3-8mm is quickly mounted and is connected with an open-flow pipeline to perform quick pressure-control open flow, and fracturing liquid is returned and discharged to the greatest extent as quickly as possible. The conventional hydraulic fracturing liquid quantity is large, so that the low-pressure and low-permeability reservoir is polluted; the reservoir is heavily polluted by common guanidine gum fracturing; the high-quality nitrogen foam fracturing technology is small in liquid injection quantity, high in seam forming capacity, good in sand-carrying and sand-paving effect and high in after-fracturing return discharge rate, and the pollution of the reservoir is greatly reduced.

Description

technical field [0001] The invention relates to the technical field of coalbed gas exploration and development, in particular to a technology for reducing pollution by nitrogen foam fracturing of coalbed gas wells in low-pressure and low-permeability reservoirs. Background technique [0002] Coalbed methane, as an important unconventional natural gas resource, is increasingly valued by countries all over the world. Most of the coalbed methane is stored in the inner surface of coal matrix pores in the state of adsorption, and only a small amount exists in cleats and other fractures in a free state. The output of coalbed methane must go through the process of desorption, diffusion and seepage. [0003] Coal reservoir pressure refers to the pressure of the fluid in the fractures of the reservoir. Generally, the reservoir with a pressure gradient of less than 0.6MPa / hm is called a low-pressure reservoir. The pressure of my country's coal reservoirs is generally low pressure; my ...

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Problems solved by technology

Hydraulic fracturing technology is widely used in the development of coalbed methane at home and abroad as the main production stimulation measure. However, due to the serious leakage of fracturing fluid, low flowback rate, difficulty in proppant carrying, and

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