Heatproof salt-resistant cross-linking polymer system

Abstract

The invention provides a temperature resist, salt resist crosslinked polymer system with controllable crosslinking time and strength, comprising water, polyacrylamide, melamine, formaldehyde and additive, wherein the polyacrylamide 0.03-8 weight%, melamine 0.01-4 weight%, formaldehyde solution(35-38weight%) 0.03-10 weight%, additive <2 weight%. The salt content of oilfield sewage is less than 35 *104mg/L, the total content of Ca2+ and Mg2+ is less than 5000mg/L. The temperature range of reservoir bed is 30-110 degree, the crosslinking time is 6 hours-25 days, and the viscosity after crosslinking is less than 40*104mPa.s. The long-term stability is good. The viscosity is greatly increased compared to oil displacement of polymer, suitable for reducing the use concentration of polyacrylamide and the cost is reduced, at the same time the oil displacement effect is increased and the treatment difficulty of output liquid is reduced. The crosslinked polymer system can be useful for recycling the polyacrylamide output liquid of high concentration. The invention can be used in oilfield profile controlling, exclusion of water, leak stopping and oil displacement technique. The locale preparation is simple.

Description

technical field [0001] The invention relates to a cross-linked polymer system, which has the characteristics of temperature resistance, salt resistance, adjustable strength and controllable cross-linking time, and can be used in oil field profile control, water plugging, leak plugging and oil displacement technologies. Background technique [0002] Due to the heterogeneity of the reservoir itself, the crude oil in the high permeability zone is easy to be recovered. After the oilfield entered into water flooding development, the high permeability zone was scoured by the injected water for a long time, and the heterogeneity was further strengthened. The prominent feature is that the oil wells generally have high water cut, channeling or water flow channels are formed between individual oil and water wells, and some oil wells are flooded. As a result, the efficiency of water injection is getting worse, the oil recovery rate is difficult to improve, and the economic benefits are...

AI Technical Summary

Problems solved by technology

[0004] Polymer flooding has the following four problems: a) On the basis of ensuring the effect, the amount of polymer must be increased, and there is little room for further improvement of economic benefits; b) Poor salt tolerance and difficult to realize the preparation of oilfield sewage, which limits the polymerization practical application of flooding; c) due to the high-temperature hydrolysis of polymers, the application temperature range is limited; d) the polymers in the produced fluid are difficult to handle and cannot be used

[0005] Conventional profile control and water plugging only change the permeability gradient in the vicinity of the wellbore, and the injected water will quickly bypass the adjustment zone, reducing the effect of the measure and failing to greatly improve the sweep efficiency

[0006] The cross-linking agents used in the original depth control agent are generally organic chromium, organic aluminum, organic zirconium, water-soluble phenolic resin, etc., organic chromium, organic aluminum, and organic zirconium have poor heat and salt resistance, and some have lower requirements Some have lower requirements and less salt content, even if the ground can use fresh water to meet the preparation requirements, after injection into the reservoir, the complex reservoir environment will greatly reduce the performance of the control and drive agent, and even appear to be inconsistent. Linked phenomenon

The water-soluble phenolic resin has good salt resistance, but the reservoir temperature must be above 70°C, and when the concentration of the control and displacement agent is high, it is easy to shrink and dehydrate after gelling

[0007] From 1980 to 1986, foreign modulation and flooding technology achieved rapid development. At the peak, 35% of the EOR projects in the United States were polymer flooding, but from the analysis of various documents, it can be seen that 60% of these projects were gel modulation. However, because the technology used could not adapt to the harsh reservoir conditions, the success rate of the application at that time was only 50%, and most of them were plugging adjustment near the wellbore

[0008] In 1994, there were domestic reports on the application of cross-linked polymer control and flooding technology in mineral deposits. In 1995, a large number of researches on temperature-resistant and salt-resistant cross-linked polymer technology began in China, but it was still limited by formation temperature and formation water salinity.