Transcriptome expression profiles reveal response mechanisms to drought and drought-stress mitigation mechanisms by exogenous glycine betaine in maize.

Drought stress is one of the major abiotic stresses that limit growth, development and yield of maize crops. To better understand the responses of maize inbred lines with different levels of drought resistance and the molecular mechanism of exogenous glycine betaine (GB) in alleviating drought stress, the responses of two maize inbred lines to drought stress and to the stress-mitigating effects of exogenous GB were investigated. Seedling morphology, physiological and biochemical indexes, root cell morphology and root transcriptome expression profiles were compared between a drought-tolerant inbred line Chang 7-2 and drought-sensitive inbred line TS141. Plants of both lines were subjected to treatments of drought stress alone and drought stress with application of exogenous GB. The results showed that with the increase of drought treatment time, the growth and development of TS141 were inhibited, while those of Chang 7-2 were not significantly different from those of the control (no drought stress and GB). Compared with the corresponding data of the drought-stress group, every index measured from the two inbred lines indicated mitigating effects from exogenous GB, and TS141 produced stronger mitigating responses due to the GB. Transcriptome analysis showed that 562 differentially expressed genes (DEGs) were up-regulated and 824 DEGs were down-regulated in both inbred lines under drought stress. Due to the exogenous GB, 1061 DEGs were up-regulated and 424 DEGs were down-regulated in both lines. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify 10 DEGs screened from the different treatments. These results showed that the expression of 9 DEGs were basically consistent with their respective transcriptome expression profiles. The results of this study provide models of potential mechanisms of drought tolerance in maize as well as potential mechanisms of how exogenous GB may regulate drought tolerance.

Mutant lpa1 Analysis of ZmLPA1 Gene Regulates Maize Leaf-Angle Development through the Auxin Pathway.

Maize plant type is one of the main factors determining maize yield, and leaf angle is an important aspect of plant type. The rice Loose Plant Architecture1 (LPA1) gene and Arabidopsis AtIDD15/SHOOT GRAVITROPISM5 (SGR5) gene are related to their leaf angle. However, the homologous ZmLPA1 in maize has not been studied. In this study, the changing of leaf angle, as well as gene expression in leaves in maize mutant lpa1 and wild-type 'B73' under different IAA concentrations were investigated. The regulation effect of IAA on the leaf angle of lpa1 was significantly stronger than that of the wild type. Transcriptome analysis showed that different exogenous IAA treatments had a common enrichment pathway-the indole alkaloid biosynthesis pathway-and among the differentially expressed genes, four genes-AUX1, AUX/IAA, ARF and SAUR-were significantly upregulated. This study revealed the regulation mechanism of ZmLPA1 gene on maize leaf angle and provided a promising gene resource for maize breeding.

Rational design and fabrication of an alkali-induced O/W emulsion stabilized with cellulose nanofibrils (CNFs): implication for eco-friendly and economic oil recovery application.

In this work, an alkali-induced oil in water (O/W) emulsion stabilized with cellulose nanofibrils (CNFs) was proposed to advance the development of enhanced oil recovery (EOR) approaches. The reactive species in the crude oil were first determined by FT-ICR MS. Subsequently, direct measurements of emulsion rheology, morphology, drop size distribution, and interfacial tensions (IFTs) were performed. Particular interest was placed on the stability and variation of the average drop diameter of the emulsions to reveal the underlying stabilizing mechanisms. The results showed that the introduction of L-CNFs (containing lignin segment) and CNFs could significantly prohibit the coalescence of drops and thus improve the stability of the emulsions. L-CNFs and CNFs were irreversibly absorbed at the oil-water interface forming a solid "armor" on the drops with 63.1% of the oil-water interface being covered by CNFs. This finally led to the generation of highly stable O/W emulsions. This work demonstrated the potential of CNFs as promising "green" interface stabilizers for emulsion flooding EOR particularly for in situ surfactant generation scenarios.

Influence of Mineral Composition on Initiation Pressure of Waterflood-Induced Fractures in Tight Sandstone Reservoir.

Revealing the impact of core mineral composition on the initiation pressure of waterflood-induced fractures (WIFs) in tight sandstone reservoirs is a crucial aspect of studying the initiation mechanism of WIFs. In this paper, through quantitative characterization of the core mineral composition from six samples of the Chang 6 reservoir in the Wuqi oilfield, western Ordos Basin, and modified experimental cores and displacement equipment for WIF experiments, the influence of the core mineral composition on the initiation pressure of WIFs in tight oil reservoirs is investigated. The conclusions are as follows. (1) The rock mineral composition of the Chang 6 reservoir in the Wuqi oilfield, western Ordos Basin, includes quartz, feldspar calcite, and clay, characterizing it as a typical feldspar sandstone reservoir. Quartz and calcite are considered as brittle minerals, while feldspar and clay are categorized as lithologic minerals. (2) For feldspar sandstone reservoirs, including quartz, feldspar, calcite, and clay minerals, when the combined content of quartz and feldspar exceeds 600% of the total mineral content, the changes of quartz and feldspar content will affect the initiation pressure of WIFs. As the ratio of the quartz content to feldspar content Rqf increases, the initiation pressure of WIFs exhibits a logarithmic function decrease. (3) Considering the contribution of diagenetic minerals to rock brittleness, the calculation method for the brittleness index of feldspar tight sandstone reservoirs is improved. (4) The relationships between Rqf, brittleness index, and initiation pressure of induced fractures suggest that an increase in Rqf leads to a power-law increase in the brittleness index, while the initiation pressure of WIFs relative to the brittleness index shows a power-law decrease. This phenomenon indicates an increased likelihood of WIFs occurring during the long-term water injection process in feldspar sandstone reservoirs. This work contributes to understanding how core minerals affect the initiation pressure of WIFs in tight sandstone reservoirs.

Analysis of the Distribution Pattern of Remaining Oil and Development Potential after Weak Gel Flooding in the Offshore LD Oilfield.

The LD oilfield is one of the representative offshore oilfields. After weak gel flooding, the recovery rate is significantly improved. However, the oilfield is then in a medium- to high-water content stage, presenting a complex distribution of the remaining oil. The measures for further enhanced oil recovery (EOR) are uncertain. As a result, it is necessary to clarify the distribution pattern and development potential of the remaining oil during the high-water content period after weak gel flooding. In this study, an online nuclear magnetic resonance (NMR) oil displacement experiment and microscopic oil displacement experiment were conducted, and the mechanisms of weak gel flooding and the distribution pattern of the remaining oil were clarified in the LD oilfield. Additionally, high-multiple water flooding and numerical simulation experiments were conducted to analyze the development potential after weak gel flooding. The results show that the effect of weak gel flooding was more significant in the core of 1500 mD, with an increase in oil recovery of 9% compared to 500 mD. At a permeability of 500 mD, the degree of crude oil mobilization in micropores and small pores caused by weak gel flooding was improved by 29.64% and 23.48%, respectively, compared with water flooding. At 1500 mD, the degree of crude oil mobilization in small pores caused by weak gel flooding was increased by 37.79% compared to water flooding. After weak gel flooding, the remaining oil was primarily distributed in medium and large pores. Microscopically, the remaining oil was dominated by cluster residual oil, accounting for 16.49%, followed by columnar, membranous, and blind-end residual oil. High multiple water flooding experiments demonstrated that weak gel flooding could significantly reduce development time. The ultimate oil recovery efficiency of 500 mD and 1500 mD reached 71.85% and 80.69%, respectively. Numerical simulation results show that the ultimate oil recovery efficiency increased from 62.04% to 71.3% after weak gel flooding. This indicated that the LD oilfield still had certain development potential after weak gel flooding. The subsequent direction for enhanced oil recovery focuses mainly on mobilizing oil in medium pores or clustered remaining oil. This will play a crucial role in further exploring methods for utilizing the remaining oil and increasing the recovery rate.

Research on the Enhanced Oil Recovery Technique of Horizontal Well Volume Fracturing and CO2 Huff-n-Puff in Tight Oil Reservoirs.

The low oil productivity of tight oil reservoirs is mainly caused by poor reservoir physical properties such as low porosity and permeability, a small pore and throat ratio, and bad well connectivity, which lead to bad water injection capability and rapid pressure decline for the reservoir. In this paper, an enhanced oil recovery technique for tight oil reservoirs is proposed by combination of horizontal well volume fracturing and CO2 huff-n-puff to improve the reservoir physical properties and increase the flow capability of crude oil. In the initial reservoir development stage, the precise horizontal well trajectory and reservoir volume fracturing scale are designed by analyzing the distribution of sand body thickness and the oily sedimentary facies. The micro-seismic tracking technique is also used to monitor the fracture elongation. When the reservoir energy cannot satisfy the economic limit of oil productivity, the CO2 huff-n-puff technique is applied to increase the reservoir energy quickly. After the precise fracturing technique is used in tight oil Block X, the average oil production rate of six fractured horizontal wells increases by 5 ton (1 ton = 7.33 bbl) at the initial production stage, and the effective oil production increase life lasts for 32 months. When the reservoir energy is supplemented using the CO2 huff-n-puff technique, the oil production rate of pilot experiment well SP-1 increases from 1.9 to 12.8 ton with a cumulative oil increase of 1333.8 ton.

Network Analysis of Different Exogenous Hormones on the Regulation of Deep Sowing Tolerance in Maize Seedlings.

The planting method of deep sowing can make the seeds make full use of water in deep soil, which is considered to be an effective way to respond to drought stress. However, deep sowing will affect the growth and development of maize (Zea mays L.) at seedling stage. To better understand the response of maize to deep sowing stress and the mechanism of exogenous hormones [Gibberellin (GA3), Brassinolide (BR), Strigolactone (SL)] alleviates the damaging effects of deep-sowing stress, the physiological and transcriptome expression profiles of seedlings of deep sowing sensitive inbred line Zi330 and the deep-tolerant inbred line Qi319 were compared under deep sowing stress and the conditions of exogenous hormones alleviates stress. The results showed that mesocotyl elongated significantly after both deep sowing stress and application of exogenous hormones, and its elongation was mainly through elongation and expansion of cell volume. Hormone assays revealed no significant changes in zeatin (ZT) content of the mesocotyl after deep sowing and exogenous hormone application. The endogenous GA3 and auxin (IAA) contents in the mesocotyl of the two inbred lines increased significantly after the addition of exogenous GA3, BR, and SL under deep sowing stress compared to deep sowing stress, while BR and SL decreased significantly. Transcriptome analysis showed that the deep seeding stress was alleviated by GA3, BR, and SLs, the differentially expressed genes (DEGs) mainly included cellulose synthase, expansin and glucanase, oxidase, lignin biosynthesis genes and so on. We also found that protein phosphatase 2C and GA receptor GID1 enhanced the ability of resist deep seeding stress in maize by participating in the abscisic acid (ABA) and the GA signaling pathway, respectively. In addition, we identified two gene modules that were significantly related to mesocotyl elongation, and identified some hub genes that were significantly related to mesocotyl elongation by WGCNA analysis. These genes were mainly involved in transcription regulation, hydrolase activity, protein binding and plasma membrane. Our results from this study may provide theoretical basis for determining the maize deep seeding tolerance and the mechanism by which exogenous hormones regulates deep seeding tolerance.

Relative Permeability Characteristics During Carbon Capture and Sequestration Process in Low-Permeable Reservoirs.

The injection of carbon dioxide (CO2) in low-permeable reservoirs can not only mitigate the greenhouse effect on the environment, but also enhance oil and gas recovery (EOR). For numerical simulation work of this process, relative permeability can help predict the capacity for the flow of CO2 throughout the life of the reservoir, and reflect the changes induced by the injected CO2. In this paper, the experimental methods and empirical correlations to determine relative permeability are reviewed and discussed. Specifically, for a low-permeable reservoir in China, a core displacement experiment is performed for both natural and artificial low-permeable cores to study the relative permeability characteristics. The results show that for immiscible CO2 flooding, when considering the threshold pressure and gas slippage, the relative permeability decreases to some extent, and the relative permeability of oil/water does not reduce as much as that of CO2. In miscible flooding, the curves have different shapes for cores with a different permeability. By comparing the relative permeability curves under immiscible and miscible CO2 flooding, it is found that the two-phase span of miscible flooding is wider, and the relative permeability at the gas endpoint becomes larger.

Modified Porous SiO2-Supported Cu3(BTC)2 Membrane with High Performance of Gas Separation.

The structures and applications of metal-organic framework materials (MOFs) have been attracting great interest due to the wide variety of possible applications, for example, chemical sensing, separation, and catalysis. N-[3-(Trimethoxysilyl)propyl]ethylenediamine is grafted on a porous SiO2 disk to obtain a modified porous SiO2 disk. A large-scale, continuous, and compact Cu3(BTC)2 membrane is prepared based on a modified porous SiO2 disk. The chemical structure, surface morphology, thermal stability, mechanical stability, and gas separation performance of the obtained Cu3(BTC)2 membrane is analyzed and characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and a gas separation experiment. The results show that the prepared Cu3(BTC)2 membrane has an intact morphology with its crystal. It is continuous, compact, and intact, and has good thermal stability and mechanical stability. The result of the gas separation experiment shows that the Cu3(BTC)2 membrane has a good selectivity of hydrogen and can be used to recover and purify hydrogen.