Cross-linking agent applicable to highly-mineralized water fracturing fluid

Abstract

The invention discloses a cross-linking agent applicable to highly-mineralized water fracturing fluid. The cross-linking agent is stable complex which is formed by reaction of a zirconium compound, a boron compound with a chelating ligand and bridging ligand in aqueous liquor. The zirconium compound is zirconium acetate or zirconium oxychloride with content of 9wt%-18wt%; the boron compound is boric acid or borax with content of 3wt%-40wt%; the chelating ligand is N, N-di(2-hydroxyl ethyl) glycine with content of 9wt%-18wt%; the bridging ligand is one, two or a mixture of more than two of glycerol, mannitol, sorbitol and triethanolamine, with content of 5wt%-19wt%, and the balance of water. The cross-linking agent disclosed by the invention can be cross-linked with a thickening agent under a weakly alkaline condition, not only contains heavy metal zirconium, but also contains boron, so that damages to stratums by the fracturing fluid are effectively lowered; moreover, highly-mineralized water can be adopted to directly prepare the fracturing fluid, so that fresh water resources are saved, and expenditure cost of oilfield enterprises in treating and producing highly-mineralized water is reduced.

Description

technical field [0001] The invention relates to a cross-linking agent for preparing fracturing fluid with high salinity water in the field of oil and gas field development and production increase. technical background [0002] For the development of low-permeability reservoirs, fracturing is the best choice, but the current fracturing is mainly water-based fracturing, which requires a large amount of fresh water resources, so that the implementation of fracturing projects in water-scarce areas or offshore has certain limitations. difficulty. On the other hand, in the process of oilfield exploitation, a large amount of production layer water is produced. These waters are basically brine with high salinity, with a salinity of more than 20,000, containing a large amount of metal ions. After the water is mined to the ground , must be treated to meet the discharge standards required by the state, which increases the production cost of the oil field. If the fracturing process ca...

AI Technical Summary

Problems solved by technology

However, the cross-linking agent in the fracturing fluid system commonly used at present can only cross-link with the thickener under moderately strong alkaline conditions, and adjusting the pH of highly mineralized water to above 8 will cause It causes the precipitation of various metal ions in it, consumes the added alkali, and affects the performance of fracturing fluid

Therefore, if you want to use produced water and seawater to prepare fracturing fluid, you need a cross-linking agent that can cross-link under weakly alkaline conditions. At present, there are some cross-linking agents that can be used in weakly alkaline environments, such as aluminum salts or organic zirconium. , organic titanium cross-linking agents, but aluminum salt cross-linking agents can only be used in environments with low formation temperatures; organic zirconium and organic titanium can be used in environments with high formation temperatures (US4808739), but simple The jelly formed by organic zirconium and organic titanium cross-linking agents has poor shear resistance, resulting in weak sand-carrying ability of the jelly, especially serious damage to the formation, and the damage rate can reach more than 90%.

Images