Carbon Nanofiber-Enhanced HPAM/PEI Gels for Conformance Control in Petroleum Reservoirs with High Temperatures

Abstract

Nanoparticles have recently been widely used in polymer gel systems to enhance gel strength. However, it is yet unclear how various types of nanoparticles affect the gelation characteristics of polymer gels. In addition, nanomaterials are rarely studied for enhancing the temperature resistance of polyethyleneimine (PEI) cross-linked polyacrylamide gels (i.e., HPAM/PEI gels). Under the urgent requirements of global carbon neutrality, this paper intends to use carbon nanofibers as gel performanceenhancing materials. Furthermore, the mechanism of their influence on the gelation properties and temperature resistance of HPAM/PEI gels was investigated. We evaluated the gelation time of the carbon nanofiber-enhanced HPAM/PEI gels at both 80 and 150 °C by the Sydansk method. The gelation properties and microscopic network structure of the gels were evaluated by rheometer, differential calorimetry scanning/thermogravimetry, and scanning electron microscopy. Results show that adding carbon nanofibers could delay the gelation time at 80 °C, and the gelation time of the polymer gel system reaching F was more than 6 days. On the other hand, the addition of carbon nanofibers could slightly shorten the gelation time of the polymer gel at an ultrahigh temperature of 150 °C. Moreover, the gel strength reached the highest when the addition amount of carbon nanofibers was 0.1%. The gel strength (G′) was as high as 12 Pa, and its stability was as long as 30 days, which was more temperature-resistant than that without adding nanofibers. The microstructure of carbon nanofiber-enhanced HPAM/PEI gels showed many tiny pore-like structures, which might be more conducive to heat dissipation and prevent dehydration. As a result, the carbon nanofiber-enhanced HPAM/PEI gel system had outstanding thermal stability and could be applied in ultrahigh-temperature reservoir conditions while maintaining high plugging strength. This study can present new ideas for improving the nanoparticle-enhanced HPAM/PEI gels in high-temperature petroleum reservoirs and further improving oil recovery, which has essential reference significance.

Review on Microemulsions for Conformance Improvement Technology: Fundamentals, Design Considerations, and Perspectives

“…17,18 The injection of conformance control chemicals has been applied with good results, but the application is recognized to be very challenging and dynamic in pilot-and field-scale operations. 18,19 Traditional and previously exploited methods, including polymers, gels, surfactants, foams, CO 2 thickening, bacteria, macroemulsions, exhibit distinct characteristics and performance at reservoir conditions related to salinity tolerance, thermodynamic stability, chemical degradation, and temperature resistivity. 6,20−23 Microemulsions (MEs), on the other hand, are thermodynamically stable isotropic oil−water mixtures formed by an appropriate combination of emulsifiers.…”

“…Conformance control aims to plug high-permeability regions to divert flow toward unswept low-permeability regions. − This process encompasses the use of a variety of chemical fluids or mechanical means to redistribute the water-drive streamlines. ,− A conforming drive is designed to attain enhanced recoveries for extended periods as well as reduce costs from excessive water recycling. − Chemical conformance treatment may be applied either via injector or producer wells of mature areas with the field. However, it is generally preferred to inject conformance chemicals through a producer well compared to an injector well to attain a faster response to restrict water production. , The injection of conformance control chemicals has been applied with good results, but the application is recognized to be very challenging and dynamic in pilot- and field-scale operations. , …”

Water Management and Oil Recovery Improvement Performance of High-Strength Preformed Particle Gels in Fractured Conglomerate Reservoirs

“…18,19 These methods involve injecting chemicals into the formation to adjust the water injection profile in the waterflood swept zone by the effect of either adsorption, retention, or plugging efficiency. 20,21 They can divert chase injection water toward high residual oil zones that have not been swept. 22−24 These chemicals mainly include in situ cross-linked polymer gels, particle gels, foam, etc., which have been evaluated in the laboratory and applied in the field in Xinjiang's conglomerate reservoirs.…”

“…Currently, commonly used conformance control techniques to improve oil recovery include mechanical and chemical methods. , Chemical conformance control methods are widely used due to their convenient construction and low cost. , These methods involve injecting chemicals into the formation to adjust the water injection profile in the waterflood swept zone by the effect of either adsorption, retention, or plugging efficiency. , They can divert chase injection water toward high residual oil zones that have not been swept. − These chemicals mainly include in situ cross-linked polymer gels, particle gels, foam, etc., which have been evaluated in the laboratory and applied in the field in Xinjiang’s conglomerate reservoirs. − However, their conformance control effect has become very limited after many years of waterflooding in the field. Thus, it is necessary to select chemical systems with a higher strength to plug high-conductivity channels such as fractures.…”

Insights into Polyacrylamide Hydrogels Used for Oil and Gas Exploration: Gelation Time, Gel Strength, and Adhesion Strength

“…The gel can stabilize at 90 °C for more than 30 days, and it can be used for water shutoff in fractured reservoirs. Zhu et al 24 used carbon nanofiberenhanced HPAM/PEI gel system applying for conformance control in high-temperature petroleum reservoirs. It was desirably able to be used at 150 °C, and its stability was as long as 30 days with a gel strength remaining 12 Pa. Liu et al 25 prepared a temperature-resistant gel system for water shutoff treatment in high-temperature reservoirs.…”