A stimulus-responsive clean fracturing fluid and its preparation method

Abstract

The invention discloses a stimuli-responsive clean fracturing fluid and a preparation method thereof. The technical scheme is: (1) mixing long carbon chain methacrylate and dimethylamine aqueous solution at a molar ratio of 1:1-3 at 20-3 React at 60°C for 24 hours, remove excess dimethylamine by rotary evaporation, and obtain long-chain tertiary amine; (2) use 1-5% long-chain tertiary amine as thickener, add HCl to protonate long-chain tertiary amine Obtain a clear and transparent thickener solution, and then add 1 to 5% of counter ion salt, the molar ratio of thickener and counter ion salt is 1:2 to 3:1, to obtain viscoelastic surfactant cleaning fracturing fluid. The thickener is pH-responsive. After the construction, NaOH is added to the fracturing flowback fluid, and the quaternary ammonium salt thickener is deprotonated and transformed into a tertiary amine. Fracture fluid, greatly reducing the cost of cleaning fracturing fluid. The clean fracturing fluid is simple to prepare, has adjustable performance, and has broad application prospects in tight gas, coalbed methane and shale gas fracturing.

Description

technical field [0001] The invention relates to a stimulus-responsive clean fracturing fluid for natural gas wells, coalbed gas wells and shale gas well fracturing fluids and a preparation method thereof. Background technique [0002] In 1997, Schlumberger reported a clean fracturing fluid, viscoelastic surfactant fracturing fluid (VES), which can form worm-like micelles under certain conditions and intertwine to form a reversible three-dimensional network. The fracturing fluid system with special rheological properties is also called polymer-free fracturing fluid or clean fracturing fluid because of the small molecular weight of surfactants or additives in the system. [0003] This kind of fracturing fluid is composed of surfactant, isopropanol, potassium chloride, etc., because it has few types of additives (no need to add cross-linking agent or gel breaker), simple mixing on site, convenient construction, thorough gel breaking, It has the characteristics of high flowback...

AI Technical Summary

Problems solved by technology

First, the negative charge on the rock surface of the formation makes it very easy for high-concentration cationic surfactants to undergo serious adsorption and retention in the formation, causing wetting reversal and causing damage to the formation; second, the temperature resistance is poor. Most of the VES fracturing fluids used have a temperature resistance of about 70°C. In addition, they cannot form a thin filter cake on the rock surface, and the filtration loss is serious at high temperatures. Third, the flowback VES gel breaking fluid contains a large amount of cationic surface Active agent, polluting the environment; Fourth, the dosage is relatively large, and the fluid loss is strong. Compared with conventional guar gum fracturing fluid, the cost is still higher

The above problems limit the large-scale application of VES fracturing fluid in various fields of oilfields

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