Method for liquid carbon dioxide fracturing stimulation of natural gas hydrate reservoir

Abstract

The invention provides a liquid carbon dioxide fracturing reconstruction method for natural gas hydrate reservoirs, which effectively utilizes the cooling effect of liquid nitrogen on the strata, performs cooling pretreatment on the strata near the wellbore before fracturing, and increases the natural gas hydrate storage capacity. The brittleness of the stratum reduces the fracture initiation pressure of the formation; and then utilizes the unique physical properties of liquid carbon dioxide. During the fracturing process, the fracturing fluid enters the formation and exchanges heat with the latter, and the phase of the liquid carbon dioxide changes when it is heated. Converted into supercritical carbon dioxide and gaseous carbon dioxide, supercritical carbon dioxide has the fluidity of gas and the density of liquid, and can flow to the deep part of natural gas hydrate reservoirs with low permeability, and undergo fracturing to greatly increase the volume; At the same time, when liquid carbon dioxide and supercritical carbon dioxide phase change into gaseous carbon dioxide, the volume increases rapidly and the pressure rises, increasing the complexity of fracturing to form fractures.

Description

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

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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