CN-121990644-A - Method for preparing polymer solution from purified water in oil field to inhibit viscosity loss

CN121990644ACN 121990644 ACN121990644 ACN 121990644ACN-121990644-A

Abstract

The invention relates to the technical field of oilfield polymer flooding, in particular to a method for preparing polymer solution from oilfield purified water to inhibit viscosity loss, which comprises the following steps of cleaning a polymerization preparation container and equipment by adopting a compound degradation inhibitor, and collecting the container and the equipment for later use after cleaning; the method comprises the steps of carrying out a first step of purifying oilfield produced water to obtain oilfield purified water, a second step of adding a required amount of compound degradation inhibitor into the oilfield purified water in a polymerization vessel and equipment after cleaning, stirring to obtain polymer solution for injection polymerization, and a fourth step of injecting the polymer solution for injection polymerization into a reinjection wellhead and then carrying out oil displacement. According to the invention, the compound degradation inhibitor is added into the purified water of the oil field, so that on one hand, the decomposition effect of bacteria on polymers is inhibited, various pollutants such as oil sludge which are easy to grow bacteria in a storage tank and a pipeline can be removed, and on the other hand, the influence of system pollution on the viscosity of the polymers is eliminated, and the aim of low viscosity loss in the polymer flooding process is fulfilled.

Inventors

LIU PENGFEI
ZHAI XIAOYI
YAN ZHONG
LI YUNFEI
GONG ZHAOBO
QIU TAO
DAI XINHE
LI HUAN
NI FENGPING
ZHANG LU

Assignees

新疆石油管理局有限公司
中国石油天然气股份有限公司
中国石油天然气集团有限公司

Dates

Publication Date: 20260508
Application Date: 20241108

Claims (10)

1. A method for preparing polymer solution for inhibiting viscosity loss by using purified water of an oil field, which is characterized by comprising the following steps: Firstly, preparing a compound degradation inhibitor; Secondly, cleaning the matched polymerization container and equipment by adopting a compound degradation inhibitor, and keeping the container and the equipment for later use after cleaning; thirdly, purifying the oilfield produced water to obtain oilfield purified water; Fourthly, adding a required amount of compound degradation inhibitor into the cleaned aggregation vessel and the oilfield purified water in the equipment, and stirring to obtain pretreated purified water; fifthly, adding a polymer into the pretreated purified water, stirring and dissolving to obtain a polymer solution for injection polymerization; and sixthly, injecting the polymer solution for injection into a reinjection wellhead, and then carrying out oil displacement.
2. The method for preparing polymer solution for inhibiting viscosity loss by using purified water in oil field according to claim 1, wherein in the first step, the compound degradation inhibitor comprises deoxidizer, mixed bactericide and bacteriostat, and the deoxidizer, the mixed bactericide and the bacteriostat are uniformly stirred after being mixed according to the required amount, so as to obtain the compound degradation inhibitor, wherein the deoxidizer is 10-15 parts by mass, the mixed bactericide is 10-25 parts by mass, and the bacteriostat is 1-2 parts by mass.
3. The method for preparing polymer solution for inhibiting viscosity loss by using purified water in oil field according to claim 2, wherein the oxygen scavenger is one or more of anhydrous sodium sulfite, zinc sulfate, hydrazine and acetone oxime.
4. A method for preparing polymer solution for inhibiting viscosity loss by using purified water in oil field according to claim 2 or 3, wherein the mixed bactericide is a mixed solution composed of polyaldehyde and quaternary ammonium salt, and the polyaldehyde content is 5% to 95% and the quaternary ammonium salt content is 5% to 95% by mass percent in the mixed solution.
5. The method for preparing polymer solution for inhibiting viscosity loss in oilfield purified water according to claim 4, wherein the polyaldehyde is one or more of glutaraldehyde, formaldehyde and paraformaldehyde, and the quaternary amine salt is one or more of dodecyl dimethyl benzyl ammonium chloride and ‌ tetradecyl dimethyl benzyl ammonium chloride.
6. The method for preparing polymer solution for inhibiting viscosity loss in purified water in oil field according to claim 5, wherein the polyaldehyde is glutaraldehyde and the quaternary ammonium salt is dodecyldimethylbenzyl ammonium chloride.
7. The method for preparing polymer solution for inhibiting viscosity loss of purified water in oil field according to claim 5 or 6, wherein the bacteriostatic agent is small cationic polymer, and the small cationic polymer is polydimethyldiallyl ammonium chloride.
8. The method for preparing polymer solution for inhibiting viscosity loss in purified water in oil field according to claim 2, 3, 5 or 6, wherein in the second step, the addition amount of the degradation inhibitor is 900mg/L to 1000mg/L based on the volumes of the polymerization container and the equipment when the polymerization container and the equipment are cleaned.
9. The method for preparing polymer solution for inhibiting viscosity loss according to claim 8, wherein the addition amount of the compound degradation inhibitor per liter of purified water in the fourth step is 50mg to 100mg.
10. The method for preparing polymer solution for oil field purified water according to claim 2 or 3 or 5 or 6 or 9, wherein in the fifth step, the mass concentration of the polymer solution for injection is 1000mg/L to 3000mg/L.

Description

Method for preparing polymer solution from purified water in oil field to inhibit viscosity loss Technical Field The invention relates to the technical field of oilfield polymer flooding, in particular to a method for preparing polymer solution from oilfield purified water to inhibit viscosity loss. Background After secondary oil recovery is finished, polymer flooding, binary compound flooding and ternary compound flooding are usually developed to further improve the oil reservoir recovery ratio, the viscosity of the displacement fluid is increased, the oil-water interfacial tension is reduced, the mobility of water is reduced by the displacement fluid, the water-oil mobility ratio is reduced, the fingering of water is inhibited, and the sweep coefficient is improved, so that the oil reservoir recovery ratio is improved. In general, clear water is used for preparing the polymer, and the clear water has the characteristics of high viscosity and good viscosity stability of the polymer. And a large amount of produced water is produced every day in the oil field development, reinjection is needed after purification treatment, and the reinjection pressure of the purified water is higher, so that the problem of the utilization of the purified water is solved, and purified water is needed to be matched and gathered. At present, the high-mineralization purified water is affected by various ions, dissolved oxygen, bacteria and other factors, the direct compounding viscosity is low, the viscosity stability is extremely poor, the viscosity stability requirements of polymer flooding and binary compound flooding are difficult to meet, the viscosity retention rate is only 38.34% in 30 days in the implementation process, and the wellhead viscosity standard reaching rate is only 66%. Accordingly, there is a need to develop a new method to reduce the impact of system contamination in oilfield purified water on polymer viscosity. Disclosure of Invention The invention provides a method for inhibiting viscosity loss by preparing polymer solution from oilfield purified water, which overcomes the defects of the prior art, and can effectively solve the problems that secondary pollution is easy to generate and the viscosity loss is large due to the influence of adhesion of a pipeline and a tank body when the oilfield purified water is adopted to prepare the polymer solution. The technical scheme of the invention is realized by the following measures that the method for preparing polymer solution for inhibiting viscosity loss by using purified water of an oil field is carried out according to the following steps: Firstly, preparing a compound degradation inhibitor; Secondly, cleaning the matched polymerization container and equipment by adopting a compound degradation inhibitor, and keeping the container and the equipment for later use after cleaning; thirdly, purifying the oilfield produced water to obtain oilfield purified water; Fourthly, adding a required amount of compound degradation inhibitor into the cleaned aggregation vessel and the oilfield purified water in the equipment, and stirring to obtain pretreated purified water; fifthly, adding a polymer into the pretreated purified water, stirring and dissolving to obtain a polymer solution for injection polymerization; and sixthly, injecting the polymer solution for injection into a reinjection wellhead, and then carrying out oil displacement. The following are further optimizations and/or improvements to the above-described inventive solution: In the first step, the compound degradation inhibitor comprises an deoxidizer, a mixed bactericide and a flocculating agent, and the deoxidizer, the mixed bactericide and the flocculating agent with required amounts are mixed and stirred uniformly to obtain the compound degradation inhibitor, wherein the deoxidizer is 10-15 parts by mass, the mixed bactericide is 10-25 parts by mass, and the flocculating agent is 1-2 parts by mass. The deoxidizer is one or more of anhydrous sodium sulfite, zinc sulfate, hydrazine and acetone oxime. The mixed bactericide is a mixed solution consisting of polybasic aldehyde and quaternary ammonium salt, wherein the polybasic aldehyde content is 5-95% and the quaternary ammonium salt content is 5-95% by mass percent in the mixed solution. The polybasic aldehyde is one or more of glutaraldehyde, formaldehyde and paraformaldehyde, and the quaternary ammonium salt is one or more of dodecyl dimethyl benzyl ammonium chloride and ‌ tetradecyl dimethyl benzyl ammonium chloride. The polyaldehyde is glutaraldehyde, and the quaternary ammonium salt is dodecyl dimethyl benzyl ammonium chloride. The antibacterial agent is a small cationic polymer, and the small cationic polymer is polydimethyl diallyl ammonium chloride. In the second step, when the polymerization container and the equipment are cleaned, the adding amount of the compound degradation inhibitor is 900mg/L to 1000mg/L according to the volumes of the poly