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ABSTRACT: The nutritional components and quality of milk are influenced by the rumen microbiota and its metabolites at different lactation stages. Hence, rumen fluid and milk samples from 6 dairy cows fed the same diet were collected during peak lactation, early mid-lactation, and later mid-lactation. Untargeted metabolomics and 16S rRNA sequencing were applied for analyzing milk and rumen metabolites, as well as rumen microbial composition, respectively. The levels of lipid-related metabolites, l-glutamate, glucose-1-phosphate, and acetylphosphate in milk exhibited lactation-dependent attenuation. Maltol, N-acetyl-d-glucosamine, and choline, which are associated with milk flavor or coagulation properties, as well as l-valine, lansioside A, clitocine, and ginsenoside La, increased significantly in early mid-lactation and later mid-lactation, especially in later mid-lactation. The obvious increase in rumen microbial diversities (ACE and Shannon indices) were observed in early mid-lactation compared with peak lactation. Twenty-one differential bacterial genera of the rumen were identified, with Succinivibrionaceae_UCG-001, Candidatus Saccharimonas, Fibrobacter, and SP3-e08 being significantly enriched in peak lactation. Rikenellaceae_RC9_gut_group, Eubacterium_ruminantium_group, Lachnospira, Butyrivibrio, Eubacterium_hallii_group, and Schwartzia were most significantly enriched in early mid-lactation. In comparison, only 2 bacteria (unclassified_f__Prevotellaceae and Prevotellaceae_UCG-001) were enriched in later mid-lactation. For rumen metabolites, LysoPE(16:0), l-glutamate, and l-tyrosine had higher levels in peak lactation, whereas PE(17:0/0:0), PE(16:0/0:0), PS(18:1(9Z)/0:0), l-phenylalanine, dulcitol, 2-(methoxymethyl)furan, and 3-phenylpropyl acetate showed higher levels in early mid-lactation and later mid-lactation. Multiomics-integrated analysis revealed that a greater abundance of Fibrobacter contributed to phospholipid content in milk by increasing ruminal acetate, l-glutamate, and LysoPE(16:0). Prevotellaceae_UCG-001 and unclassified_f_Prevotellaceae provide substrates for milk metabolites of the same category by increasing ruminal l-phenylalanine and dulcitol contents. These results demonstrated that milk metabolomic fingerprints and critical functional metabolites during lactation, and the key bacteria in rumen related to them. These findings provide new insights into the development of functional dairy products.

As a crucial exploration technique for unconventional reservoirs, hydraulic fracturing enables the formation of complex fracture networks, thereby facilitating the flow of oil and gas. The closure of natural fractures decreases stimulation performance. Microparticle proppants are used to fill natural fractures and effectively increase the stimulation area. The 100-mesh proppant conventionally used in field operations may be insufficiently small to effectively access natural fractures. In order to effectively overcome natural fractures closure, microparticle proppants (i.e., proppants with a diameter of 75 μm (200-mesh) or less) are required. The particle size threshold test of microparticle proppants placement is conducted to determine the size threshold of proppants flowing into natural fractures. The microparticle proppants placement experiment in multi-branch fractures is conducted to investigate the volume difference of proppants in different fractures. Numerical simulations are performed to model proppant transport within fractures of actual dimensions to facilitating the optimization of stimulation parameters. The main conclusions are as follows: (1) Effective inflow of microparticle proppants requires a size threshold of proppants. For the 200-mesh proppants, the size should be less than half of natural fractures width when microparticle proppants effectively flow into natural fractures. (2) Sand concentration affects the size threshold of microparticle proppants. The size threshold should appropriately increase to ensure the inflow of proppant. (3) Difference of multi-branch fracture width has a significant effect on volume of microparticle proppants inside fractures. When the width ratio of multi-branch fractures exceeds 2, this effect becomes obvious. (4) Particle size has an effect on proppant placement. 200-mesh proppants can obtain uniform distribution of proppants among natural fractures. 140-mesh proppants can obtain maximum proppant volume among natural fractures. Sand concentration significantly affects proppant placement performance. The optimal sand concentration is 60kg/m3. The pumping rate for a single cluster fracture should not be excessively low. The pumping rate should be larger than 0.5m3/min and the optimal pumping rate 2m3/min. In this paper, the particle size and concentration of particulate proppant are optimized and the geometric characteristics of fractures are considered. These conclusions provide important practical guidance and scientific basis for the optimization and application of hydraulic fracturing technology.

Abstract Background Dairy cows’ lactation performance is the outcome of the crosstalk between ruminal microbial metabolism and host metabolism. However, it is still unclear to what extent the rumen microbiome and its metabolites, as well as the host metabolism, contribute to regulating the milk protein yield (MPY). Methods The rumen fluid, serum and milk of 12 Holstein cows with the same diet (45% coarseness ratio), parity (2–3 fetuses) and lactation days (120–150 d) were used for the microbiome and metabolome analysis. Rumen metabolism (rumen metabolome) and host metabolism (blood and milk metabolome) were connected using a weighted gene co-expression network (WGCNA) and the structural equation model (SEM) analyses. Results Two different ruminal enterotypes, with abundant Prevotella and Ruminococcus, were identified as type1 and type2. Of these, a higher MPY was found in cows with ruminal type2. Interestingly, [Ruminococcus] gauvreauii group and norank_f_Ruminococcaceae (the differential bacteria) were the hub genera of the network. In addition, differential ruminal, serum and milk metabolome between enterotypes were identified, where the cows with type2 had higher L-tyrosine of rumen, ornithine and L-tryptophan of serum, and tetrahydroneopterin, palmitoyl-L-carnitine, S-lactoylglutathione of milk, which could provide more energy and substrate for MPY. Further, based on the identified modules of ruminal microbiome, as well as ruminal serum and milk metabolome using WGCNA, the SEM analysis indicated that the key ruminal microbial module1, which contains the hub genera of the network ([Ruminococcus] gauvreauii group and norank_f_Ruminococcaceae) and high abundance of bacteria (Prevotella and Ruminococcus), could regulate the MPY by module7 of rumen, module2 of blood, and module7 of milk, which contained L-tyrosine and L-tryptophan. Therefore, in order to more clearly reveal the process of rumen bacterial regulation of MPY, we established the path of SEM based on the L-tyrosine, L-tryptophan and related components. The SEM based on the metabolites suggested that [Ruminococcus] gauvreauii group could inhibit the energy supply of serum tryptophan to MPY by milk S-lactoylglutathione, which could enhance pyruvate metabolism. Norank_f_Ruminococcaceae could increase the ruminal L-tyrosine, which could provide the substrate for MPY. Conclusion Our results indicated that the represented enterotype genera of Prevotella and Ruminococcus, and the hub genera of [Ruminococcus] gauvreauii group and norank_f_Ruminococcaceae could regulate milk protein synthesis by affecting the ruminal L-tyrosine and L-tryptophan. Moreover, the combined analysis of enterotype, WGCNA and SEM could be used to connect rumen microbial metabolism with host metabolism, which provides a fundamental understanding of the crosstalk between host and microorganisms in regulating the synthesis of milk composition.

As important components of the cosmopolitan soil biota, soil nematodes are found at multiple trophic levels of the belowground food web and play an important role in soil function. Exploring the actual patterns of soil nematodes along the altitudinal gradients helps understand the spatial soil ecology. In this study, we used molecular analysis approaches to reveal the soil nematode spatiotemporal changes on Oakley Mountain in the northern Greater Khingan Mountain Ranges Northeast China. Our results showed that although the alpha diversity of nematode communities generally decreased with the increased altitude, it did not exhibit a monotonic decrease pattern. Bacterial feeding nematodes occupied the largest proportion among all nematode feeding types. Altitude had a more significant effect than soil depth on the structure of nematode community in all seasons. Soil bulk density, moisture, dissolved organic carbon, temperature, pH, nitrate nitrogen, and total phosphorus were the significant soil variables driving the composition of nematode community. The co-occurrence networks of soil nematode communities showed a distinct seasonal pattern. The nematode community networks in May and September had more modes and links, higher average degrees, and higher average clustering coefficients than the network in July. We demonstrated that the variance of nematode community structure in different altitudes and soil depths could be well explained by edaphic factors. This study extends our knowledge of the nematode spatial ecology in cold temperate regions and contributes to further investigation of soil ecological processes in global challenges.

Abstract The gut microbiota comprises bacteria, archaea, fungi, protists, and viruses that live together and interact with each other and with host cells. A stable gut microbiota is vital for regulating host metabolism and maintaining body health, while a disturbed microbiota may induce different kinds of disease. In addition, diet is also considered to be the main factor that influences the gut microbiota. The host could shape the gut microbiota through other factors. Here, we reviewed the mechanisms that mediate host regulation on gut microbiota, involved in gut‐derived molecules, including gut‐derived immune system molecules (secretory immunoglobulin A, antimicrobial peptides, cytokines, cluster of differentiation 4+ effector T cell, and innate lymphoid cells), sources related to gut‐derived mucosal molecules (carbon sources, nitrogen sources, oxygen sources, and electron respiratory acceptors), gut‐derived exosomal noncoding RNA (ncRNAs) (microRNAs, circular RNA, and long ncRNA), and molecules derived from organs other than the gut (estrogen, androgen, neurohormones, bile acid, and lactic acid). This study provides a systemic overview for understanding the interplay between gut microbiota and host, a comprehensive source for potential ways to manipulate gut microbiota, and a solid foundation for future personalized treatment that utilizes gut microbiota.

Alternate-temperature loading can cause cyclic thermal stress; therefore complex artificial fracture networks are formed in hot dry rock owing to thermal expansion and contraction under alternating thermal loading. In this study, the heat recovery potential of hot dry rock with a complex fracture network under alternating temperature loading was simulated numerically based on the hydrothermal coupling algorithm and compared with that of hot dry rock with a single fracture. The results show that the complex fractures formed under alternate thermal loading have better heat recovery performance than a single fracture, and the heat recovery performance of a complex fracture network is closely related to the intersection angle of fractures in the network. The temperature at the fracture outlet increases with an increase in the intersection angle between the branch fractures and the main fracture. At the angle of 30° between the branch fractures and main fracture, the average temperatures at the fracture outlet were 0.031% and 0.025% higher than those at the angles of 90° and 60°, respectively. Simultaneously with the water-injection, the temperature in the branch fractures gradually increased with an increase in the angle of the crossing fractures. When the angle between the branch and main fractures was 90°, the temperature fields on the two sides of the branch fracture were symmetrical. When the angle was 60° or 30°, the temperature fields on the two sides of the branch fracture were asymmetrical. The results of this study provide theoretical and technical support for the extraction of deep geothermal energy.

ABSTRACT Enterotypes can be useful tools for studying the gut microbial community landscape, which is thought to play a crucial role in animal performance. However, few studies have been carried out to identify enterotypes and their associations with growth performance in young goats. In this study, two enterotypes were categorized in 76 goats: cluster 1 (n = 39) and cluster 2 (n = 37). Compared to cluster 2, cluster 1 had greater growth rates, the concentrations of acetate, propionate, valerate, and total volatile fatty acids (VFA) in the gut. Several serum glycolipid metabolism parameters, including glucose, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), were also increased in cluster 1, while serum IgG was decreased in cluster 1. Using α-diversity analysis, we found a microbiome with lower richness and diversity in cluster 1. Some gut bacteria, including Succinivibrio and several members of the Prevotellaceae family, were enriched in cluster 1, while Christensenellaceae R-7 group, Romboutsia, and Clostridium sensu stricto 1 were enriched in cluster 2. A co-occurrence network analysis revealed that the differential interaction patterns existed in two enterotypes, and microbial function prediction suggested that some nutrient metabolism-related pathways, including amino acid biosynthesis and starch and sucrose metabolism, were enriched in cluster 1. Furthermore, a correlation analysis showed that enterotype-related bacteria were closely correlated with gut fermentation, serum biochemistry, and growth rate. Overall, our data provide a new perspective for understanding enterotype characteristics in goats, offering insights into important microbial interaction mechanisms for improving the growth performance of ruminant animals. IMPORTANCE The intricate relationships between a host animal and its resident gut microbiomes provide opportunities for dealing with energy efficiency and production challenges in the livestock industry. Here, we applied the enterotype concept to the gut microbiome in young goats and found that it can be classified into two enterotypes which are apparently associated with divergences in gut fermentation, blood biochemistry, and goat growth rates. The microbial co-occurrence networks and function predictions differed between the two enterotypes, suggesting that the formation of host phenotype may be modified by different bacterial features and complex bacterial interactions. The characteristics of enterotypes related to growth performance in young goats may enable us to improve long-term production performance in goat industry by modulating the gut microbiome during early life.

During acid fracturing, acid-rock reaction heat has a significant influence on temperature profiles in fractures and consequently on etched fracture dimensions, but it is usually neglected or simplified in acid fracturing models. This can lead to misestimating of etched fracture dimensions. A model for calculating real-time acid-rock reaction enthalpy, which is a function of temperature, pressure and volumetric work of carbon dioxide produced by reactions, is coupled into a heat transfer model and a fracture growth model, and its effect on etched fracture dimensions is simulated. True experimental data from SL oilfield in China is used for simulation. The results show that acid-rock reaction heat reduces the effective etched fracture length by around 10%, and the effect of reaction heat on the etched fracture length in limestone is 10%–15% larger than in dolomite. Acid-rock reaction heat makes the etched width profile along a fracture more inhomogeneous. With consideration of acid-rock reaction heat, etched fracture widths are 15%–20% larger near the wellbore and over 20% narrower at fracture tip, and its effects are more intense in limestone than in dolomite. The influences of acid-rock reaction heat on etched fracture dimensions are stronger when the initial formation temperature is lower and when acid of high concentration is used. When the pump rate of acid fracturing is increased, the effect of acid-rock reaction heat on etched fracture dimensions is weakened. The new coupled models were used in carbonate reservoirs in Tarim Basin, China for acid fracturing optimization. A scenario comparison showed that the designed treatment parameters of acid fracturing should be different when acid-rock reaction heat was fully considered. The application of the optimized scenario resulted in at least three folds of production rate increase compared to that before stimulation.

The tooth arrangements of human beings are challenging to accurately observe when relying on dentists’ naked eyes, especially for dental caries in children, which is difficult to detect. Cone-beam computer tomography (CBCT) is used as an auxiliary method to measure patients’ teeth, including children. However, subjective and irreproducible manual measurements are required during this process, which wastes much time and energy for the dentists. Therefore, a fast and accurate tooth segmentation algorithm that can replace repeated calculations and annotations in manual segmentation has tremendous clinical significance. This study proposes a local contextual enhancement model for clinical dental CBCT images. The local enhancement model, which is more suitable for dental CBCT images, is proposed based on the analysis of the existing contextual models. Then, the local enhancement model is fused into an encoder–decoder framework for dental CBCT images. At last, extensive experiments are conducted to validate our method.

(1) Background: Korean pine (Pinus koraiensis) and Manchurian walnut (Juglans mandshurica) are the main tree species for plantation regeneration in Northeast China, and the mixed plantation of them is one of the typical measures adopted to address the decline in stand productivity in long-term monocultures. However, little is known about the effects of Korean pine and Manchurian walnut monocultures and mixed plantations on soil microbial diversity, composition, and functional groups. (2) Methods: We used ITS and 16S rRNA gene sequencing to detect fungal and bacterial communities and used the FUNGuild, FAPROTAX, and Bugbase databases to predict their functional groups. (3) Results: Fungal and bacterial alpha diversity were always higher in Manchurian walnut monocultures than in Korean pine monocultures. The plantation type had a greater impact on the fungal composition than the bacterial composition. The fungal functional groups were significantly affected by the plantation type (p < 0.05), while the bacterial functional groups were barely changed among all plantation types. The soil available nutrient content was the most important soil factor in shaping the microbial community structures and functional groups. (4) Conclusions: Shifts in fungal community compositions and functional groups might play a dominant role in soil nutrient cycling across the different plantation types in Northeast China.

By reviewing the development history of stimulation techniques for deep/ultra-deep oil and gas reservoirs, the new progress in this field in China and abroad has been summed up, including deeper understanding on formation mechanisms of fracture network in deep/ultra-deep oil and gas reservoir, performance improvement of fracturing fluid materials, fine stratification of ultra-deep vertical wells, and mature staged multi-cluster fracturing technique for ultra-deep and highly deviated wells/horizontal wells. In light of the exploration and development trend of ultra-deep oil and gas reservoirs in China, the requirements and technical difficulties in ultra-deep oil and gas reservoir stimulation are discussed: (1) The research and application of integrated geological engineering technology is difficult. (2) The requirements on fracturing materials for stimulation are high. (3) It is difficult to further improve the production in vertical profile of the ultra-deep and hugely thick reservoirs. (4) The requirements on tools and supporting high-pressure equipment on the ground for stimulation are high. (5) It is difficult to achieve efficient stimulation of ultra-deep, high-temperature and high-pressure wells. (6) It is difficult to monitor directly the reservoir stimulation and evaluate the stimulation effect accurately after stimulation. In line with the complex geological characteristics of ultra-deep oil and gas reservoirs in China, seven technical development directions are proposed: (1) To establish systematic new techniques for basic research and evaluation experiments; (2) to strengthen geological research and improve the operational mechanism of integrating geological research and engineering operation; (3) to develop high-efficiency fracturing materials for ultra-deep reservoirs; (4) to research separated layer fracturing technology for ultra-deep and hugely thick reservoirs; (5) to explore fracture-control stimulation technology for ultra-deep horizontal well; (6) to develop direct monitoring technology for hydraulic fractures in ultra-deep oil and gas reservoirs; (7) to develop downhole fracturing tools with high temperature and high pressure tolerance and supporting wellhead equipment able to withstand high pressure.

Polymer flooding is drawing lots of attention because of the technical maturity in some reservoirs. The first commercial polymer flooding in China was performed in the Daqing oilfield and is one of the largest applications in the world. Some laboratory tests from Daqing researchers in China showed that the viscoelasticity of high molecular weight polymers plays a significant role in increasing displacement efficiency. Hence, encouraged by the conventional field applications and new findings on the viscoelasticity effect of polymers on residual oil saturation (ROS), some high-concentration high-molecular-weight (HCHMW) polymer-flooding field tests have been conducted. Although some field tests were well-documented, subsequent progress was seldom reported. It was recently reported that HCHMW has a limited application in Daqing, which does not agree with observations from laboratory core flooding and early field tests. However, the cause of this discrepancy is unclear. Thus, a systematic summary of polymer-flooding mechanisms and field tests in China is necessary. This paper explained why HCHMW is not widely used when considering new understandings of polymer-flooding mechanisms. Different opinions on the viscoelasticity effect of polymers on ROS reduction were critically reviewed. Other mechanisms of polymer flooding, such as wettability change and gravity stability effect, were discussed with regard to widely reported laboratory tests, which were explained in terms of the viscoelasticity effects of polymers on ROS. Recent findings from Chinese field tests were also summarized. Salt-resistance polymers (SRPs) with good economic performance using produced water to prepare polymer solutions were very economically and environmentally promising. Notable progress in SRP flooding and new amphiphilic polymer field tests in China were summarized, and lessons learned were given. Formation blockage, represented by high injection pressure and produced productivity ability, was reported in several oil fields due to misunderstanding of polymers’ injectivity. Although the influence of viscoelastic polymers on reservoir conditions is unknown, the injection of very viscous polymers to displace medium-to-high viscosity oils is not recommended. This is especially important for old wells that could cause damage. This paper clarified misleading notions on polymer-flooding implementations based on theory and practices in China.

This article is about a 6-day-old male infant admitted to the hospital presented with a 2-day history of worsening widespread spitting. After a series of treatments, we found that the diagnosis was “broncho-esophageal fistula”. So he was recommended to receive surgical treatment. After preoperative preparation, thoracoscopic ligation of esophagus and bronchospasm was performed.The fistula was 1.5 cm long. The broncho-esophageal fistula was often found in adults, which was often misdiagnosed as pneumonia with bad effective treatment, especially in a newborn, but the non-invasive CT three-dimensional imaging technology can provide a reliable basis for the clear diagnosis of esophageal bronchospasm. Keywords: Neonate, Thoracoscopic surgery, Broncho-esophageal fistula

Purpose: To report a case of surgical interventions for a patient with relapsing polychondritis who presented with late ocular complications. Observations: A 44-year-old male was diagnosed to have relapsing polychondritis on the basis of recurrent acute auricular chondritis, deformity of the ear, saddle nose deformity and painful nasal chondritis, acute ocular inflammation with conjunctivitis, episcleritis and keratouveitis, laryngotracheal chondritis, erythema nodosum in the skin, a history of polyarthritis, and abnormal blood examination findings. The acute ocular and auricular inflammation was resolved with oral corticosteroid treatment. Intraocular pressure (IOP) of the left eye was 60 mmHg as measured by Goldmann applanation tonometer. Gonioscopic observation revealed the presence of peripheral anterior synechiae and plateau iris configuration. Express drainage screw implantation was applied to the left eye, because topical and systemic medicines failed to decrease the IOP. After 12 months, complicated cataract aggravated in the right eye, and phacoemulsification operation was performed with corticosteroids administered during the perioperative period. His corrected visual acuity was 20/20 for the right eye, and the IOP remained below 21 mmHg for the left eye. The patient has been healthy, without any recurrence, for 36 months. Conclusions and importance: The present case of relapsing polychondritis is the first to be reported wherein late ocular complications were alleviated by surgical interventions. Routine use of corticosteroids is necessary for successful anti-glaucoma and phacoemulsification operations.

A theoretical method for studying the behavior of magnetic field intensity inside a rectangular plate with orthotropic anisotropic conductivity was presented. Firstly, based on Maxwell’s equations, the mathematical model for the magnetic field in the plate was established. Then, the governing equation for determining the magnetic field intensity was solved by double Fourier sinusoidal transformation. Furthermore, taking graphite rectangular plate as an example, the magnetic field intensity inside the plate was simulated and the behavior of the magnetic field was introduced in detail. Lastly, the effects of the plate’s size, the external excitation frequency and the conductivity of graphite on the internal magnetic field intensity were analyzed.

In this paper, we presented a theoretical method for studying the behavior of magnetic field intensity and eddy current inside a magnetostriction based bi-layered composite. Firstly, the mathematical model for the electromagnetic field in the composite was established. Then, the governing equation for determining the magnetic field intensity and eddy current was solved. Furthermore, the effect of the composite’s conductivity on the magnetic field intensity and eddy current were discussed. Lastly, by comparing with the well known R.L. Stoll’s equation, the magnetic field intensity calculated based on our equation showed a less than 0.5% error.

Background and objective Residual carcinoma cells play an important role in the result of radiofrequency ablation (RFA) of pulmonary malignancies, and Platinum-based adjuvant chemotherapy is one of the important treatment regimen to reduce residual carcinoma cells after RFA. ERCC1 (excision repair cross-complementation group 1) is an important factor affecting Platinum-based chemotherapy effects. Residual carcinoma cells exhibit some changes of their features after RFA; however, there is no report about the change of their ERCC1 expression by now. This study focused on the change of ERCC1 expression in residual VX2 squamous carcinoma cells in rabbit lung after RFA. Methods The model of VX2 squamous carcinoma in rabbit lung was established by injection of tissue block suspension. Fifty-eight New Zealand White rabbits with VX2 squamous carcinoma were randomly devided into the control group (n=10) and the RFA group (n=48). During the RFA procedure in these models, residual carcinoma cells were achieved by controlling the range of electrode expanding, power output and treatment time. At different points of time, the positive rates of ERCC1 expression in residual carcinoma were detected by immunohistochemistry. Results Comparing with the control group, the positive rate of ERCC1 expression in residual carcinoma in RFA group increases transiently within 1 d to 5 d (53.7%±1.6% & 32.9%±2.5%), and 5 d later, it decline to the level of the control group. Conclusion The ERCC1 expression of residual pulmonary carcinoma increase within 5 d after RFA. Thus platinum-based adjuvant chemotherapy may be ineffective in this period.

Time delay due to maturation time, capturing time or other reasons widely exists in biological systems. In this paper, a predator-prey system of Leslie type with diffusion and time delay is studied based on mathematical analysis and numerical simulations. Conditions for both delay induced and diffusion induced Turing instability are obtained by using bifurcation theory. Furthermore, a series of numerical simulations are performed to illustrate the spatial patterns, which reveal the information of density changes of both prey and predator populations. The obtained results show that the interaction between diffusion and time delay may give rise to rich dynamics in ecosystems.

The novel Cr-containing low alloy steels have exhibited good corrosion resistance in CO2 environment, mainly owing to the formation of Cr-enriched corrosion film. In order to evaluate whether it is applicable to the CO2 and H2S coexistence conditions, the corrosion behavior of low-chromium steels in CO2-H2S environment with high pressure and high temperature was investigated using weight loss measurement and surface characterization. The results showed that P110 steel suffered localized corrosion and both 3Cr-P110 and 5Cr-P110 steels exhibited general corrosion. However, the corrosion rate of 5Cr-P110 was the highest among them. The corrosion process of the steels was simultaneously governed by CO2 and H2S. The outer scales on the three steels mainly consisted of FeS1−x crystals, whereas the inner scales on Cr-containing steels comprised of amorphous FeS1−x, Cr(OH)3 and FeCO3, in contrast with the amorphous FeS1−x and FeCO3 mixture film of P110 steel. The more chromium the steel contains, the more chromium compounds the corrosion products contain. The addition of chromium in steels increases the uniformity of the Cr-enriched corrosion scales, eliminates the localized corrosion, but cannot decrease the general corrosion rates. The formation of FeS1−x may interfere with Cr-enriched corrosion scales and lowering the corrosion performance of 3Cr-P110 and 5Cr-P110 steels.