Dual Crosslinked Poly(acrylamide-co-N-vinylpyrrolidone) Microspheres With Re-crosslinking Ability For Fossil Energy Recovery

Microspheres have been proposed to be applied in controlling wastewater production for mature oilfields and migrating leakage for gas and nuclear waste storage. However, it remains challenging for stacked microspheres to maintain strong blocking ability in micron-sized small pores or fractures. In this study, a novel microsphere was developed with comprehensive properties including high deformability and long re-crosslinking time upon tunable swelling ratio for the applications. A dual covalent and physical crosslinking strategy was used to develop novel microspheres reinforced by a hydrogen bond (H-bond, between pyrrole ring and amide group) and coordination bond (between chromium acetate (CrAc) and carboxyl group via hydrolysis process). The microspheres were fabricated via radical suspension copolymerization of acrylamide (AM) and N-vinylpyrrolidone (NVP) in the presence of N, Nʹ-methylene-diacrylamide (MBA) with subsequent introduction of CrAc. MBA induced the strong crosslinking through a chemical covalent bond and H-bond triggered the weak crosslinking which was anticipated to prohibit the hydrolysis of the amide group. The H-bond delayed the formation of CrAc coordination bond by delaying the formation of carboxyl groups, resulting in achieving the re-crosslinking of the microspheres. As a result, the microspheres exhibit the tunable initial size (8–165 μm) and swelling ratio (30–630 μm), with controllable network parameters. The microspheres showed high migration ability (can transport through pores with 1/16 size of microsphere itself), and long re-crosslinking time (up to 16.5 days). The re-crosslinked gel demonstrated dual network structure with districted mesh size ζ distribution

High Resolution Genome Wide Association Studies Reveal Rich Genetic Architectures of Grain Zinc and Iron in Common Wheat (Triticum aestivum L.)

Biofortification is a sustainable strategy to alleviate micronutrient deficiency in humans. It is necessary to improve grain zinc (GZnC) and iron concentrations (GFeC) in wheat based on genetic knowledge. However, the precise dissection of the genetic architecture underlying GZnC and GFeC remains challenging. In this study, high-resolution genome-wide association studies were conducted for GZnC and GFeC by three different models using 166 wheat cultivars and 373,106 polymorphic markers from the wheat 660K and 90K single nucleotide polymorphism (SNP) arrays. Totally, 25 and 16 stable loci were detected for GZnC and GFeC, respectively. Among them, 17 loci for GZnC and 8 for GFeC are likely to be new quantitative trait locus/loci (QTL). Based on gene annotations and expression profiles, 28 promising candidate genes were identified for Zn/Fe uptake (8), transport (11), storage (3), and regulations (6). Of them, 11 genes were putative wheat orthologs of known Arabidopsis and rice genes related to Zn/Fe homeostasis. A brief model, such as genes related to Zn/Fe homeostasis from root uptake, xylem transport to the final seed storage was proposed in wheat. Kompetitive allele-specific PCR (KASP) markers were successfully developed for two major QTL of GZnC on chromosome arms 3AL and 7AL, respectively, which were independent of thousand kernel weight and plant height. The 3AL QTL was further validated in a bi-parental population under multi-environments. A wheat multidrug and toxic compound extrusion (MATE) transporter TraesCS3A01G499300, the ortholog of rice gene OsPEZ2, was identified as a potential candidate gene. This study has advanced our knowledge of the genetic basis underlying GZnC and GFeC in wheat and provides valuable markers and candidate genes for wheat biofortification

Preparation and Salt-Insensitive Behavior Study of Swellable, Cr³⁺-Embedded Microgels for Water Management

The microgels have been used in the oilfield for water management and enhanced oil recovery (EOR). Fully swollen size of the microgels is very sensitive to salt, which brings uncertainties on the performance of microgel treatments. Herein, a Cr3+-embedded polyacrylamide based microgel, synthesized via a free-radical suspension polymerization, is described which could significantly weaken the salt-sensitivity of the microgels. Embedment of Cr3+ in the polymeric networks of microgels crosslinked through covalent bonds has been studied using the scanning electron microscopy (SEM), FT-IR, and dialysis analysis. The effects of crosslinker concentration, initiator concentration, and the stirring rate during polymerization on the size of the microgels have been characterized. In addition, contrary to the commercial microgels, the fully swollen size of the Cr3+-embedded microgels performed insensitivity to the salts, such as sodium chloride (NaCl), calcium chloride (CaCl2), and aluminum chloride (AlCl3). Moreover, the pore occlusion experiments demonstrated the Cr3+-embedded microgels also have the same viscoelasticity at different salt concentrations, resulting in the similar plugging performance. The Cr3+-embedded microgel shows a great potential for improving the microgel plugging for water management and enhanced oil recovery

Effect of the Chromium Ion Diffusion in Polyacrylamide/Chromium Acetate Gelation System with Surrounding Water on Gelation Behavior

The diffusion of Cr3+ from the Cr3+/HPAM system is simulated by quantifying the entrapment ability of the Cr3+ after dialysis analysis through a dialysis bag method to study the Cr3+ diffusion effect on the gelation types. After the gelant is put in the dialysis bag surrounded by the solvents, only the diffusion of the aqueous ions are allowed, which eventually can be detected in the dialysate. By monitoring the gelants with varying initial contents, we find that the Cr3+ dialysis kinetics and total dialyzed amount are changed. In this particular experiment, the gelation types are classified and the classification result differences for the same gelant with or without dialysis process are investigated and compared. In this study, we assess the gelant contents in terms of possible limiting scenarios for successful gelation and discuss their gelation results influenced by the Cr3+ diffusion The results demonstrate that Cr3+ diffusion, in different extent, influences the gelation types and gelation time of the Cr3+/HPAM systems with varying HPAM molecular weight (MW), the Cr3+ initial concentration, the initial HPAM polymer concentration, or the degree of initial HPAM hydrolysis. Along with the gelation types and the accompanying morphological study, determine the relationships between the initial Cr3+ concentration and the true Cr3+ concentration entrapped on the polymers are possible, which are pretty distinct from each other. Neglecting to consider such diffusion effects will lead to overestimating of the crosslinking results. In addition, a sorption model is used to demonstrate the sorption trend changes before and after the gelation time

Systematic Evaluation of a Novel Self-Healing Poly(acrylamide-co-vinyl acetate)/Alginate Polymer Gel for Fluid Flow Control in High Temperature and High Salinity Reservoirs

Preferential fluid flow often occurs when water and CO2 is injected into mature oilfields, significantly reducing their injection efficiency. Particle gels have been evaluated and applied to control the short circulation problems. This study systematically investigated a novel poly(acrylamide-co-vinyl acetate)/alginate-based interpenetrated gel system (Alg-IPNG) which is designed to control the preferential fluid flow problems in high-temperature reservoirs. Chromium acetate was incorporated into the gel system to provide the delayed crosslinking feature of the particle gels. The alginate polymer system can also take advantage of the Ca2+ ions in the formation water, which exist in most reservoirs, to reinforce its strength by capturing the Ca2+ to form Ca–alginate bonds. In this paper, various characterizations for the Alg-IPNGs before and after the self-healing process were introduced: (1) the elastic modulus is set at up to 1890 Pa, and (2) the water uptake ratio is set at up to 20. In addition, we also discuss their possible self-healing and reinforcement mechanisms. In particular, the self-healing starting time of the Alg-IPNG particles are modified between 38 to 60 h, which is related to the water uptake ratio, Ca2+ concentration, and temperature. The reinforced Alg-IPNG gel has an enhanced thermal stability (180 days) at the temperature up to 110 °C

Systematic Evaluation of a Novel Self-Healing Poly(acrylamide-co-vinyl acetate)/Alginate Polymer Gel for Fluid Flow Control in High Temperature and High Salinity Reservoirs

Preferential fluid flow often occurs when water and CO2 is injected into mature oilfields, sig-nificantly reducing their injection efficiency. Particle gels have been evaluated and applied to control the short circulation problems. This study systematically investigated a novel poly(acrylamide-co-vinyl acetate)/alginate-based interpenetrated gel system (Alg-IPNG) which is designed to control the preferential fluid flow problems in high-temperature reservoirs. Chromium acetate was incorporated into the gel system to provide the delayed crosslinking feature of the particle gels. The alginate polymer system can also take advantage of the Ca2+ ions in the formation water, which exist in most reservoirs, to reinforce its strength by capturing the Ca2+ to form Ca-alginate bonds. In this paper, various characterizations for the Alg-IPNGs before and after the self-healing process were introduced: (1) the elastic modulus is set at up to 1890 Pa, and (2) the water uptake ratio is set at up to 20. In addition, we also discuss their possible self-healing and reinforcement mechanisms. In particular, the self-healing starting time of the Alg-IPNG particles are modified between 38 to 60 h, which is related to the water uptake ratio, Ca2+ concentration, and temperature. The reinforced Alg-IPNG gel has an enhanced thermal stability (180 days) at the temperature up to 110 ⁰C

Mineral Dissolution and Fine Migration Effect on Oil Recovery Factor by Low-Salinity Water Flooding in Low-Permeability Sandstone Reservoir

The latest oil price decline simply increases the demand for enhanced oil recovery (EOR) and pushes research developers to keep improvements in oil recovery. The goal is always to recover as much oil as possible at the lowest possible cost. Low-salinity water flooding (LSWF) is an EOR method that operates at a lower cost than other EOR methods. The objective of this study was to test the ability of low salinity waterflooding to improve oil recovery from low permeability sandstone reservoirs. Four types of tests were conducted: imbibition, core flooding, zeta potential and scanning electron microscopy (SEM) tests. Two key factors were studied: salinity of the injected water and aging time. Their influence on the amount of oil recovery, stabilized injection pressure, pH, and permeability reduction was determined. The results showed that injected low brine concentration resulted in improving oil recovery. The oil recovery factor results during the second water flooding cycle (after aging for 24 h) showed more oil recovered during low water salinity injections. The zeta potential results showed that decreasing the salinity of injected water resulted in a decrease of the zeta potential value for both injection cycles, before and after aging for 24 h. Results also imply Low-salinity water flooding redistributes the flowing paths by releasing sand particles and some fine minerals causing the flow path to narrow. Thus, low salinity water flooding can create a new streamline (fluid flow diversion) and improve both displacement and sweep efficiency

Experimental Evaluation of Oxidizing Breakers for a Polyacrylamide-Based Re-Crosslinkable Preformed Particle Gel

Re-crosslinkable preformed particle gel (RPPG) is a newly developed conformance control agent that can reassemble as an integrity after swelling in water. However, the RPPG has the potential to plug the injection facilities or wellbore if a treatment is not properly designed. This study focuses on selecting and evaluating the oxidizing breakers that can effectively degrade the RPPG. Bottle tests were conducted by immersing the re-crosslinked RPPG in the breaker solutions. The RPPG weight change was measured with time to analyze the breaking process. Four types of oxidizing breakers, NaClO, Ca(ClO)2, heat-activated Na2S2O8, and NaOH-activated Na2S2O8 were examined. The effect of factors, including breaker concentration, temperature, RPPG concentration on the gel breaking rate and completeness, was investigated. According to the results, three of the breakers were proven effective, excluding the Ca(ClO)2, which impaired the breaking process by generating a compact cover on the surface of RPPG. The NaOH-activated Na2S2O8 was the most effective breaker benefitting from its wide practical temperature range and effectiveness at the conditions of low breaker concentration or high RPPG concentration. More generally, the RPPG breaking was faster and more complete with a higher breaker concentration or a higher temperature. However, the increment of the RPPG concentration significantly increased the breaking time and the percentage of residue weight to the RPPG original weight