Liquid nitrogen fracturing transformation device and liquid nitrogen fracturing transformation method for natural gas hydrate reservoir

Abstract

The invention relates to the technical field of natural gas hydrate production and provides a liquid nitrogen fracturing transformation device and a liquid nitrogen fracturing transformation method for a natural gas hydrate reservoir. The method comprises the following steps: 1) pre-treating liquid nitrogen; 2) fracturing liquid nitrogen; 3) freezing a stratum by liquid nitrogen; 4) injecting liquid nitrogen for further fracturing; and finally, repeating the steps 3) and 4) till fracturing transformation of residual natural gas hydrate reservoir is completed to a pre-estimated fracturing scale. Compared with a conventional hydraulic fracturing mode, by taking liquid nitrogen as a fracturing fluid, the natural gas hydrate reservoir in South sea area of China is fractured by means of the special physical properties of the liquid nitrogen, so that problems that the reservoir is hard to fracture as the natural gas hydrate reservoir in South sea area of China has the characteristics of being poor in diagenetic property, weak to cement, low in permeability and the like are avoided. After liquid nitrogen transformation fracturing is finished, the stratum permeability can be improved, theability to communicate the stratum and a shaft is improved, and a guarantee for follow-up exploring continuity and high efficiency is provided.

Description

technical field [0001] The invention relates to the technical field of natural gas hydrate exploitation, in particular to a liquid nitrogen fracturing reconstruction device and method for natural gas hydrate reservoirs. Background technique [0002] Natural gas hydrate, commonly known as "combustible ice", is an ice-like crystalline substance formed by natural gas and water molecules under high pressure and low temperature conditions. Gas hydrates mostly exist in the deep waters of continental margins and high-latitude permafrost. At present, natural gas hydrates have been discovered in many exploration sites around the world. Natural gas hydrate has the characteristics of large amount of resources, wide distribution range, shallow burial depth, clean and pollution-free, etc. Converting the amount of natural gas resources contained in global gas hydrates into organic carbon content, its value is about twice the sum of the carbon content of the existing earth's fossil fuels...

AI Technical Summary

Problems solved by technology

However, since the natural gas hydrate reservoirs in the South my country Sea are mainly argillaceous siltstone reservoirs, they have the characteristics of poor diagenesis, weak cementation, and low permeability.

Traditional hydraulic fracturing is difficult to initiate fractures in such reservoirs, or the fractures close quickly after initiation, which cannot achieve the expected fracturing effect. Therefore, a fracturing technology that can meet the stimulation requirements of natural gas hydrate in the South my country Sea is needed

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