Preparation method of carboxymethyl guar gum

Abstract

The invention relates to a preparation method of carboxymethyl guar gum. The method comprises the steps of: alkalization of guargum raw powder: conducting alkalization at a temperature of 60-70DEG C for 90min, with the guargum raw powder and sodium hydroxide in a mass ratio of 1:0.3, and the guargum raw powder and a bactericide in a mass ratio of 1:0.02; etherification of guargum raw powder: adding chloroacetic acid at a temperature of 50DEG C, with the guargum raw powder and chloroacetic acid in a mass ratio of 1:0.5, carrying out etherification at a temperature of 60-70DEG C for 15min, then adding epoxypropane for thermostatic reaction at a temperature of 60-70DEG C for 2h, with the guargum raw powder and epoxypropane in a mass ratio of 1:0.1; and when the reaction is over, performing washing for 3 times with a washing medium at a mass concentration of 80%, then implementing centrifugation and drying at a temperature of 85DEG C, with the washing medium chosen from methanol, ethanol or isopropanol. The carboxymethyl guar gum prepared by the solvent method of the invention has good fracture-making and sand-carrying functions, and has low broken gum residual content in a fracturing fluid system of the densifier as well as less damage to stratums.

Description

technical field [0001] The invention relates to a method for preparing a thickener used in a production stimulation process for oil and gas reservoir fracturing, in particular to a physical and chemical modification of guar gum, and the prepared carboxymethyl guar gum It can be cross-linked under acidic conditions to form a gel fracturing fluid system. Background technique [0002] At present, most of the water-based fracturing fluids used in the fracturing of oil and gas fields use hydroxypropyl guar gum as the thickening agent, which has good fracture-making and sand-carrying functions, but the system has the following shortcomings: [0003] ①The fracturing fluid system using guar gum and hydroxypropyl guar gum as thickeners can only be cross-linked under alkaline conditions, and the pH value is high (about pH 10), and the clay minerals in the reservoir are easy to swell , and there is potential formation damage when the fracturing fluid meets formation ions; [0004] ②B...

AI Technical Summary

Problems solved by technology

[0003] ① The fracturing fluid system using guar gum and hydroxypropyl guar gum as thickeners can only be cross-linked under alkaline conditions, the pH value is high (pH value is about 10), and the clay minerals in the reservoir are easy to swell , and the encounter between the fracturing fluid and formation ions has potential formation damage;

[0005] The above factors affect the effect of fracturing to a certain extent.