Preparation of reduction complexing type polymer chromium cross linker

Abstract

The invention relates to a preparation method of a cross linker of reducing-complex polymer chrome. (1), water and sodium acid chromate are added into a reactor; (2), oxalic acid is added in batches under stirring; (3), the temperature is raised between 60 and 80 DEG C and then a stirring reaction with a constant temperature is carried out for 1 to 2 hours; (4) aqueous alkali is slowly added under stirring and reacted for 1 hour; the mol ratio of Cr(III) to the oxalic acid is 1:7 to 9; the mass ratio of the sodium acid chromate to water is 1:2 to 4.8; the aqueous alkali is the water liquor of sodium hydroxide or potassium hydroxide with a concentration of 10 to 50 percent and the dosage of the aqueous alkali is 2.2 to 11.3 percent of the mass of the oxalic acid; the material varieties are less; the preparation process is simply operated; the cross linker has no pungent smells and has the advantages of gelatinizing performance delaying, adjustable gelatinizing time, large scale of the gelatinizing concentration, low using amount and low polymer consumption; the lowest gelatinizing concentration of HPAM can achieve 600mg / L; a formed gelatinizing system is stable in performance which can be stable for more than 60 days under the oxygen exposure condition of 60 DEG C.

Description

technical field [0001] The invention relates to a preparation method of a chromium cross-linking agent for polymer gel used in oil fields to enhance oil recovery. Background technique [0002] High-valent metal chromium is one of the crosslinking agents commonly used in oilfield polymer gel technology. The main products used are redox system chromium and organic complex chromium. The redox system is mainly a mixture of dichromate and reducing agent. The disadvantages of this system are: it does not have the characteristic of delaying crosslinking, the redox reaction will have a certain impact on the polymer, and hexavalent chromium is highly toxic. Organic complexed chromium is mainly trivalent chromium complexed with acetic acid (salt), propionic acid (salt), and lactic acid (salt). Patent CN200410023616.7 provides a preparation method of slow cross-linking agent for polyacrylamide gel, which uses sodium dichromate, concentrated sulfuric acid, sodium sulfite, humic acid, a...

AI Technical Summary

Problems solved by technology

The redox system is mainly a mixture of dichromate and reducing agent. The disadvantage of this system is that it does not have the characteristics of delayed crosslinking, the redox reaction will have a certain impact on the polymer, and hexavalent chromium is highly toxic.

Patent CN200410023616.7 provides a preparation method of slow cross-linking agent for polyacrylamide gel, which uses sodium dichromate, concentrated sulfuric acid, sodium sulfite, humic acid, acetic acid, citric acid, 40% sodium hydroxide, water as A compound organic complex chromium is prepared by using the reduction method as the raw material, but there are many kinds of raw materials, the preparation process is complicated, and the product has the pungent smell of acetic acid

Literature reports: Tian Yuqin, Zheng Yancheng, Wang Lushan, Duan Hongdong, etc. prepared the crosslinking agent by reacting dichromate with reducing agent to form trivalent chromium, and then complexing with organic acid. The preparation process of this method is relatively complicated. , the reduction of hexavalent chromium is not complete, and the use of sodium nitrite as a reducing agent can produce nitrogen dioxide and toxic gases.

Ye Bo, Gan Xuhong and others used an organic acid and chromium trichloride at a molar ratio of 5:1 as a crosslinking agent, but it was inconvenient to use and high in cost.

[0003] Li Yongtai, Peng Zhigang and others have prepared an organic chromium complex crystal crosslinking agent, but the preparation process is complicated and the content of effective substances is low