A Cementing Slurry Preservative Applicable to Sour Oil and Gas Reservoirs

Abstract

The invention discloses an oil well cement slurry antiseptic suitable for acidic oil and gas reservoir. The oil well cement slurry antiseptic is synthesized by the following steps: (1) heating a water bath to a temperature of 40 DEG C, adding formaldehyde F and polyvinyl alcohol, then adding NaOH (10%) to adjust the pH of the solution to 8-9, then adding a first batch of urea U1, heating to a temperature of 75 DEG C, and carrying out reactions for 30 minutes; (2) adding a HCl solution (10%) to adjust the pH value of the reaction liquid to 4.5-5.5, and maintaining the temperature for 15 minutes; (3) adjusting the pH value of the reaction liquid by a HCl solution (10%), adding a second batch of urea U2, and carrying on reactions for 10 minutes; and (4) after the reaction liquid is crosslinked, adding NaOH (10%) to adjust the pH to 6.5-7.5, adding a third batch of urea U3, carrying out reactions for 10 minutes, cooling, and discharging. The antiseptic is cured to form a hard and inert coating layer after the antiseptic contacts with an acid; the solubility of the antiseptic in acid is very small; the antiseptic has very good weak acid and weak alkali properties and a strong performance on resisting corrosion of CO2 and H2S, intermiscibility between the antiseptic and cement slurry is good, the synthesis cost is low, and the antiseptic has a good market prospect.

Description

technical field [0001] The invention relates to a preservative used for improving the anticorrosion performance of cementing slurry in the cementing process of acidic oil and gas reservoirs and a synthesis method thereof. Background technique [0002] CO 2 and H 2 The corrosion of S to oil well cement has a long history. With the continuous development and utilization of oil and natural gas, the problem of acid gas corrosion of cement has attracted more and more attention from the industry. Sour oil and gas reservoirs refer to the associated H in the produced oil or natural gas 2 S, CO 2 Oil and gas reservoirs with non-hydrocarbon gases and impurities such as mercaptans and sulfides. The sour gas fields in the world are mainly distributed in China, Canada, the United States, France, Russia, Iran and other countries. Such gas fields are not only widely distributed, but most of them have been developed on a large scale. In the development process of sour oil and gas field...

AI Technical Summary

Problems solved by technology

[0004] The above anti-corrosion measures all have shortcomings: (1) research and development of new cement slurry systems, such as Halliburton's calcium phosphate cement, due to high cost and many restrictions, it is very difficult to use large-scale on-site; (2) the cement of several large companies The slurry system is aimed at preventing CO 2 corrosion, and does not involve H 2 S; (3) While the performance of the cement slurry meets the downhole conditions, its anti-corrosion performance must be increased. No matter whether the performance is improved through admixtures or the principle of particle size distribution, the deployment process will be cumbersome and complicated, and some of them meet the requirements of downhole construction. Additives such as weighting agent iron ore powder will increase the risk of cement slurry being corroded, so in complex well conditions, they generally cannot achieve good results

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