Preparation method of drag reducer for shale gas fracturing and drag reducer for fracturing

Abstract

The invention relates to the field of shale gas exploitation, fracturing, and yield increasing, and discloses a preparation method of a drag reducer for shale gas fracturing and a drag reducer prepared by the provided preparation method. The preparation method comprises the following steps: (1) in the presence of water, mixing at least part of polymeric monomers, inorganic salts, a stabilizer and a chelating agent to obtain a mixed solution; (2) adjusting the pH of the mixed solution to 3-7; and (3) adding an initiator and residual polymeric monomers into the reaction system obtained in the step (2) to carry out reactions; wherein the weight ratio of at least part of polymeric monomers to residual polymeric monomers is 1:1-20. The shale gas fracturing drag reducer prepared by the provided preparation method has the advantages of high drag reducing efficiency, strong shearing resistant performance, low viscosity, good fluidity, quick dissolving speed, and environment-friendliness.

Description

technical field [0001] The invention relates to the field of shale gas exploitation and fracturing stimulation, in particular to a method for preparing a drag reducing agent for shale gas fracturing and a drag reducing agent for shale gas fracturing prepared by the method. Background technique [0002] Shale gas resources are very rich. However, due to the low permeability of shale matrix (generally less than 1mD), the development technology is very difficult. More than 90% of shale gas wells need to be fractured to obtain ideal production. [0003] At present, shale gas fracturing and stimulation operations often use drag-reducing water for fracturing and stimulation operations. Drag-reducing water fracturing is a fracturing operation in which a small amount of additives such as fracturing fluid drag reducers, drainage aids, and fungicides are added to water as fracturing fluid. Different from gel fracturing fluid, drag-reducing water fracturing can significantly reduce fr...

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Problems solved by technology

[0004] Due to the degradation of natural macromolecules under acidic conditions and the loss of drag reducing properties, currently used drag reducing agents are mainly some synthetic high molecular polymers. CN103820099A discloses an acid drag reducing agent and its preparation method. It is made of propylene Amide, 2-acrylamido-2-methylpropanesulfonic acid and long-chain cationic monomers are prepared by polymerization, drying, and pulverization in aqueous solution. When applied, the drag reducer dissolves for as long as 1-2 hours, which cannot meet the requirements of the page. Rock gas fracturing requires large displacement and large flow on-line preparation

[0005] CN103694984A discloses a shale gas acidizing fracturing drag reducer and a preparation method thereof. The drag reducer is prepared by an inverse emulsion method, and the inverse emulsion contains a large amount of organic solvents and surfactants. After the resist is injected into the formation, it will cause groundwater pollution, which cannot meet the requirements of environmental protection

[0006] CN102977877A also discloses a drag reducer for shale gas fracturing and a preparation method thereof, in which acrylamide, 2-acrylamido-2-methyl A drag reducer for shale gas fracturing obtained by random copolymerization of three monomers, sodium propanesulfonate and sodium acrylate, and a preparation method thereof. The method does not contain organic solvents and is environmentally friendly, but the use concentration is low due to the low effective content It needs to reach 0.2% to have a good drag-reducing performance, and 2-acrylamido-2-methylpropanesulfonate sodium has a certain solubility in brine, resulting in a high viscosity of the prepared emulsion, which is not conducive to practical application

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