Preparation method of drag reducing agent for shale gas fracturing and drag reducing agent for fracturing

Abstract

The invention relates to the technical field of the fracturing increase production for the exploitation of shale gas, and discloses a method for preparing a drag reducer for shale gas fracture as well as the drag reducer for the shale gas fracture prepared by the method. The method comprises the following steps: (1) mixing at least part of polymeric monomer, inorganic salt, stabilizing agent and chelating agent in the presence of water to obtain mixed solution; (2) regulating the pH value of the mixed solution to be 2-5; and (3) adding an initiating agent and the remaining part of polymeric monomer into the obtained reaction system for reaction, wherein the weight ratio of the at least part of polymeric monomer to the remaining part of polymeric monomer is 1 to (1 to 20). The drag reducer for the shale gas fracture prepared by the method disclosed by the invention has the advantages of high drag reducing efficiency, high anti-shearing performance, good stability, low viscosity, good flowability, high dissolving speed and environmental protection.

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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