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During the construction and operation of gas storage reservoirs, changes in the principal stress direction can induce fracture propagation under conditions of lower differential stress, potentially leading to failure in the surrounding rock. However, the weakening of strength due to pure stress rotation has not yet been investigated. Based on fracture mechanics, an enhanced Mohr-Coulomb strength criterion considering stress rotation is proposed and verified with experimental and numerical simulations. The micro-damage state and the evolution of the rock under the pure stress-rotation condition are analyzed. The findings indicate that differential stress exceeding the crack initiation stress is a prerequisite for stress rotation to promote the development of rock damage. As the differential stress increases, stress rotation is more likely to induce rock damage, leading to a transition from brittle to plastic failure, characterized by wider fractures and a more complex fracture network. Overall, a negative exponential relationship exists between the stress rotation angle required for rock failure and the differential stress. The feasibility of applying the enhanced criterion to practical engineering is discussed using monitoring data obtained from a mine-by tunnel. This study introduces new concepts for understanding the damage evolution of the surrounding rock under complex stress paths and offers a new theoretical basis for predicting the damage of gas storage reservoirs.

Underground salt cavern CO2 storage (SCCS) offers the dual benefits of enabling extensive CO2 storage and facilitating the utilization of CO2 resources while contributing the regulation of the carbon market. Its economic and operational advantages over traditional carbon capture, utilization, and storage (CCUS) projects make SCCS a more cost-effective and flexible option. Despite the widespread use of salt caverns for storing various substances, differences exist between SCCS and traditional salt cavern energy storage in terms of gas-tightness, carbon injection, brine extraction control, long-term carbon storage stability, and site selection criteria. These distinctions stem from the unique phase change characteristics of CO2 and the application scenarios of SCCS. Therefore, targeted and forward-looking scientific research on SCCS is imperative. This paper introduces the implementation principles and application scenarios of SCCS, emphasizing its connections with carbon emissions, carbon utilization, and renewable energy peak shaving. It delves into the operational characteristics and economic advantages of SCCS compared with other CCUS methods, and addresses associated scientific challenges. In this paper, we establish a pressure equation for carbon injection and brine extraction, that considers the phase change characteristics of CO2, and we analyze the pressure during carbon injection. By comparing the viscosities of CO2 and other gases, SCCS’s excellent sealing performance is demonstrated. Building on this, we develop a long-term stability evaluation model and associated indices, which analyze the impact of the injection speed and minimum operating pressure on stability. Field countermeasures to ensure stability are proposed. Site selection criteria for SCCS are established, preliminary salt mine sites suitable for SCCS are identified in China, and an initial estimate of achievable carbon storage scale in China is made at over 51.8–77.7 million tons, utilizing only 20%–30% volume of abandoned salt caverns. This paper addresses key scientific and engineering challenges facing SCCS and determines crucial technical parameters, such as the operating pressure, burial depth, and storage scale, and it offers essential guidance for implementing SCCS projects in China.

Utilizing standardized artificial regulatory sequences to fine-tuning the expression of multiple metabolic pathways/genes is a key strategy in the creation of efficient microbial cell factories. However, when regulatory sequence expression strengths are characterized using only a few reporter genes, they may not be applicable across diverse genes. This introduces great uncertainty into the precise regulation of multiple genes at multiple expression levels. To address this, our study adopted a fluorescent protein fusion strategy for a more accurate assessment of target protein expression levels. We combined 41 commonly-used metabolic genes with 15 regulatory sequences, yielding an expression dataset encompassing 520 unique combinations. This dataset highlighted substantial variation in protein expression level under identical regulatory sequences, with relative expression levels ranging from 2.8 to 176-fold. It also demonstrated that improving the strength of regulatory sequences does not necessarily lead to significant improvements in the expression levels of target proteins. Utilizing this dataset, we have developed various machine learning models and discovered that the integration of promoter regions, ribosome binding sites, and coding sequences significantly improves the accuracy of predicting protein expression levels, with a Spearman correlation coefficient of 0.72, where the promoter sequence exerts a predominant influence. Our study aims not only to provide a detailed guide for fine-tuning gene expression in the metabolic engineering of Escherichia coli but also to deepen our understanding of the compatibility issues between regulatory sequences and target genes.

Karst fracture-cavity carbonate reservoirs, in which natural cavities are connected by natural fractures to form cavity clusters in many circumstances, have become significant fields of oil and gas exploration and exploitation. Proppant fracturing is considered as the best method for exploiting carbonate reservoirs; however, previous studies primarily focused on the effects of individual types of geological formations, such as natural fractures or cavities, on fracture propagation. In this study, true-triaxial physical simulation experiments were systematically performed under four types of stress difference conditions after the accurate prefabrication of four types of different fracture-cavity distributions in artificial samples. Subsequently, the interaction mechanism between the hydraulic fractures and fracture-cavity structures was systematically analyzed in combination with the stress distribution, cross-sectional morphology of the main propagation path, and three-dimensional visualization of the overall fracture network. It was found that the propagation of hydraulic fractures near the cavity was inhibited by the stress concentration surrounding the cavity. In contrast, a natural fracture with a smaller approach angle (0° and 30°) around the cavity can alleviate the stress concentration and significantly facilitate the connection with the cavity. In addition, the hydraulic fracture crossed the natural fracture at the 45° approach angle and bypassed the cavity under higher stress difference conditions. A new stimulation effectiveness evaluation index was established based on the stimulated reservoir area (SRA), tortuosity of the hydraulic fractures (T), and connectivity index (CI) of the cavities. These findings provide new insights into the fracturing design of carbonate reservoirs.

Enhancing cavern sealing is crucial for improving the efficiency of compressed air energy storage (CAES) in hard rock formations. This study introduced a novel approach using a nano-grade organosilicon polymer (NOSP) as a sealant, coupled with an air seepage evaluation model that incorporates Knudsen diffusion. Moreover, the initial coating application methods were outlined, and the advantages of using NOSP compared to other sealing materials, particularly regarding cost and construction techniques, were also examined and discussed. Experimental results indicated a significant reduction in permeability of rock specimens coated with a 7–10 μm thick NOSP layer. Specifically, under a 0.5 MPa pulse pressure, the permeability decreased to less than 1 nD, and under a 4 MPa pulse pressure, it ranged between 4.5×10−6–5.5×10−6 mD, marking a 75%–80% decrease in granite permeability. The sealing efficacy of NOSP surpasses concrete and is comparable to rubber materials. The optimal viscosity for application lies between 95 and 105 KU, and the coating thickness should ideally range from 7 to 10 μm, applied to substrates with less than 3% porosity. This study provides new insights into air transport and sealing mechanisms at the pore level, proposing NOSP as a cost-effective and simplified solution for CAES applications.

While the development of wind energy presents great potential and opportunities, the high level of uncertainty inherent in wind farms also poses considerable challenges for operators, especially when it comes to participating in the energy market. The intermittent and unpredictable fluctuation characteristics of wind power generation may cause significant deviations in the frequency and voltage of the grid, which pose a certain threat to the stability of the grid and power quality and need to be mitigated by advanced energy storage solutions. Salt caverns, these geological structures deep in underground space, are widely used in oil and gas storage, compressed air energy storage(CAES), and other projects around the world. In the operation of underground salt caverns as storage, there is no effective technical means to monitor the deformation of deep caverns in real-time. Therefore, developing a high-precision real-time prediction method for cavern volume deformation is of great significance for the safety assessment during the underground salt cavern operation. In this context, this paper proposes a comprehensive technical approach to meet the needs of real-time monitoring of the cavern status, including volume changes, in the intelligent construction of underground salt cavern facilities in China. Firstly, through the shut-in pressure test of the brine well, the volume shrinkage of the cavern during the monitoring period is obtained, and the creep parameters of the salt rock strata in the regional salt mine are inversely derived. Secondly, for a typical cavern in operation in this region, the creep deformation is predicted using numerical simulation methods. By analyzing the cavern volume deformation under different pressures, an empirical equation for cavern volume deformation is established. Finally, by combining the volume changes obtained from sonar tests conducted during the operation of the cavern, the accuracy of the simulated results and the theoretical model derived from the inverted creep parameters is verified. The real-time analysis method for cavern volume deformation developed from this research will be applied to the intelligent construction of underground salt cavern facilities, ensuring safe and controllable operation management of the storage facilities.

Abstract Bedding planes are abundant in shale oil reservoirs, but the intrinsic mechanism of fracture-height containment by these weak interfaces remains unclear. To investigate the effects of interface properties, stress conditions, and fracturing fluid viscosity on the vertical propagation of fracture heights in laminated shale oil reservoirs, a three-dimensional hydro-mechanical coupling numerical model was developed. The model is based on the 3D discrete lattice algorithm (DLA), which replaces the balls and contacts in the conventional synthetic rock mass model (SRM) with a lattice consisting of spring-connected nodes, resulting in improved computational efficiency. Additionally, the interaction between hydraulic fractures and bedding planes is automatically computed using a smooth joint model (SJM), without making any assumptions about fracture trajectories or interaction conditions. The results indicate that a higher adhesive strength of the laminated surface promotes hydraulic fracture propagation across the interface. Increasing the friction coefficient of the laminated surface from 0.15 to 0.91 resulted in a twofold increase in the fracture height. Furthermore, as the difference between vertical and horizontal principal stresses increased, the longitudinal extension distance of the fracture height significantly increased, while the activated area of the laminar surface decreased dramatically. Moreover, increasing the viscosity of the fracturing fluid led to a decrease in filtration loss along the laminar surface of the fracture and a rapid increase in net pressure, making the hydraulic fracture more likely to cross the laminar surface directly. Therefore, for heterogeneous shale oil reservoirs, a reverse-sequence fracturing technique has been proposed to enhance the length and height of the fracture. This technique involves using a high-viscosity fracturing fluid to increase the fracture height before the main construction phase, followed by a low-viscosity slickwater fracturing fluid to activate the bedding planes and promote fracture complexity. To validate the numerical modeling results, five sets of laboratory hydraulic fracturing physical simulations were conducted in Jurassic terrestrial shale. The findings revealed that as the vertical stress difference ratio increased from 0.25 to 0.6, the vertical fracture area increased by 1.98 times. Additionally, increasing both the injection displacement and the viscosity of the fracturing fluid aided in fracture height crossing of the laminar facies. These results from numerical simulation and experimental studies offer valuable insights for hydraulic fracturing design in laminated shale oil reservoirs.

Enzymes play a crucial role in various industrial production and pharmaceutical developments, serving as catalysts for numerous biochemical reactions. Determining the optimal catalytic temperature (Topt) of enzymes is crucial for optimizing reaction conditions, enhancing catalytic efficiency, and accelerating the industrial processes. However, due to the limited availability of experimentally determined Topt data and the insufficient accuracy of existing computational methods in predicting Topt, there is an urgent need for a computational approach to predict the Topt values of enzymes accurately. In this study, using phosphatase (EC 3.1.3.X) as an example, we constructed a machine learning model utilizing amino acid frequency and protein molecular weight information as features and employing the K-nearest neighbors regression algorithm to predict the Topt of enzymes. Usually, when conducting engineering for enzyme thermostability, researchers tend not to modify conserved amino acids. Therefore, we utilized this machine learning model to predict the Topt of phosphatase sequences after removing conserved amino acids. We found that the predictive model’s mean coefficient of determination (R2) value increased from 0.599 to 0.755 compared to the model based on the complete sequences. Subsequently, experimental validation on 10 phosphatase enzymes with undetermined optimal catalytic temperatures shows that the predicted values of most phosphatase enzymes based on the sequence without conservative amino acids are closer to the experimental optimal catalytic temperature values. This study lays the foundation for the rapid selection of enzymes suitable for industrial conditions.

Deep underground energy storage is the use of deep underground spaces for large-scale energy storage, which is an important way to provide a stable supply of clean energy, enable a strategic petroleum reserve, and promote the peak shaving of natural gas. Rock salt formations are ideal geological media for large-scale energy storage, and China is rich in salt rock resources and has a major shortage of energy storage space. Compared with the salt domes in other countries, the salt rock formations in China are typical lacustrine bedded salt rocks characterized by thin beds, high impurity content, and many interlayers. The development of large-scale energy storage in such salt formations presents scientific and technical challenges, including: ① developing a multiscale progressive failure and characterization method for the rock mass around an energy storage cavern, considering the effects of multifield and multiphase coupling; ② understanding the leakage evolution of large-scale deep underground energy storage caverns; ③ understanding the long-term performance evolution of large-scale deep underground energy storage caverns; ④ developing intelligent construction technologies for the deep underground salt caverns used for energy storage; and ⑤ ensuring the long-term function of deep underground energy storage spaces. The solution to these key scientific and technological problems lies in establishing a theoretical and technical foundation for the development of large-scale deep underground energy storage in China.

The objective of this study was to investigate age-related changes in cashmere production and the population of active secondary hair follicles in cashmere goats across different age groups as well as to explore the association between secondary hair follicle activity and oxidative stress. A total of 104 adult Inner Mongolian ewe goats, aged between 2 and 7 years old, were randomly selected as experimental subjects. Skin samples were collected in August 2020 and cashmere samples were collected in April 2021. The cashmere fiber yield, staple length, and diameter showed age-related variations in cashmere goats aged 2 to 7 years (p < 0.05). Cashmere production was higher in goats aged 2–4 years compared to those aged 5–7 years (p < 0.05). There were no significant differences in the population of primary and secondary hair follicles among goats aged 2 to 7 years. However, the population of active secondary hair follicles varied significantly with age, with the younger group (aged 2–4 years) having a higher population than those aged 5–7 years (p < 0.05). A moderate negative correlation was observed between cashmere fiber diameter and the population of active secondary hair follicles (p < 0.05). Age-related variations in skin antioxidant capacity and oxidative damage were observed among cashmere goats aged 2 to 7 years old (p < 0.05). Goats aged 2 to 4 years exhibited higher antioxidant capacity and lower oxidative damage (p < 0.05). Interestingly, the skin’s antioxidant capacity and oxidative damage exhibited significant positive and negative correlations with the population of active secondary hair follicles (p < 0.05). This study presents a novel approach to enhance the activity of secondary hair follicles and improve cashmere production performance through the regulation of oxidative stress.

Abstract The high temperature and high in-situ stress geological environment can significantly affect the mechanical properties, failure modes, and deformation characteristics of deep shale reservoirs. In this study, real-time high temperature triaxial compressive tests simulating the deep shale formation environment (temperature: 25–150 °C, confining pressure: 0–100 MPa) are carried out. The GSI-strength degradation and constitutive models are derived based on the Hoek–Brown criterion. The results show that in low confining pressure conditions, the mechanical behavior of shale is greatly influenced by temperature. Compared with shale at 25 °C, the compressive strength of shale at 150 °C decreases by up to 13.7%, and the elastic modulus decreases by up to 36.9%. The peak strain was increased by a factor of up to 1.4, and the yield stress level was advanced by as much as 7.4%. However, in high confining pressure conditions, the shale plasticity characteristics are significantly enhanced and the failure mode is relatively single. The GSI-strength degradation model can well characterize the variation law of shale strength with confining pressure under high temperature conditions. The statistical damage constitutive model matches the actual stress–strain curve very well, and it can fully reflect the deformation and failure characteristics of deep shale. The findings of this study can help us better understand the variation of mechanical properties of deep shale.

Salt rock, renowned for its remarkable energy storage capabilities, exists in deep underground environments characterized by high temperature and pressure. It possesses advantageous properties such as high deformability, low permeability, and self-healing from damage. When establishing a cluster of salt cavern gas storage facilities, the careful selection of ore column widths between these reservoirs is crucial for minimizing the risk of structural failure, optimizing salt rock resource utilization, and enhancing the construction and operation of gas storage reservoirs. In current practices, square triangular arrangements are commonly used in designing well layouts for reservoir groups to balance stability and economic considerations. This study, conducted in the context of the Jintan salt cavern gas storage project in Jiangsu Province, employed FLAC3D to create a finite element model for proposed gas storage configurations. A comprehensive analysis of the long-term operational safety of salt cavern gas storage with triangular well layouts was carried out. Various indices were examined, covering aspects such as cavern wall displacement, characteristics of the plastic zone, volume shrinkage, safety coefficients, seepage range, pore pressure fluctuations, and seepage volume. The study also considered the mechanical behavior of hexagonal columns within the surrounding rock during extended storage operations, leading to the optimization of allowable widths for these columns. The results indicate that, at operating pressures ranging from 6.5 to 17 MPa, the permissible column width should exceed 1.67 times the maximum cavern diameter to ensure compliance with criteria for long-term stability and containment within a square triangular layout. These findings provide valuable insights into determining the optimal allowable widths of salt cavern columns for positive triangular layouts.

The utilization of sediment voids for natural gas storage represents the future direction of salt cavern underground gas storage (UGS) in China. In this study, we first analyzed the way in which the sediment interacts with the salt caverns and the equilibrium state of the process. Subsequently, a novel approach employing the Discrete Element Method (DEM) for simulating sediment-filled salt cavern UGS was introduced, successfully modeling the operational process of sediment-filled salt cavern UGS. Moreover, deformation, plastic zone behavior, effective volume shrinkage rate, equivalent strain, and safety factor were employed to assess the impact of sediment on salt cavern stability. The findings indicate a positive influence of sediment on salt cavern stability, particularly in regions directly contacting the sediment. Deformation and effective volume shrinkage of the cavern were effectively mitigated, significantly improving the stress state of rock salt. This effect is more pronounced at lower internal gas pressures. In summary, sediment enhances the stability of salt caverns, providing a long-term and stable environment for natural gas storage within sediment voids.

The objective of this study was to investigate the effects of fasted live-weight gain during the cashmere non-growing period on cashmere production performance and secondary hair follicle activity, to provide a theoretical basis for appropriate supplementary feeding of cashmere goats. Fifty Inner Mongolian cashmere goats aged 2–4 years old were randomly selected and weighed in May and September 2019, respectively. Based on fasted live-weight gain between the two weights, the experimental ewe goats were divided into two groups: 0–5.0 kg group (n = 30) and 5.0–10.0 kg group (n = 20). Skin samples and cashmere samples were collected. Results of a Pearson correlation analysis showed that fasted live-weight gain during the cashmere non-growing period had a moderate and strong positive correlation with cashmere yield (p = 0.021) and cashmere staple length (p = 0.002), respectively, but did not correlate with cashmere diameter (p = 0.254). Compared with cashmere goats with a fasted live-weight gain of 0–5.0 kg, cashmere goats with a fasted live-weight gain of 5.0–10.0 kg had a 17.10% increase in cashmere yield (p = 0.037) and an 8.09% increase in cashmere staple length (p = 0.045), but had no significant difference in cashmere diameter (p = 0.324). Results of a Pearson correlation analysis showed that there was a strong positive correlation between fasted live-weight gain and the population of active secondary hair follicles in the skin of cashmere goats (p < 0.01). Compared with cashmere goats with a fasted live-weight gain of 0–5.0 kg, cashmere goats with a fasted live-weight gain of 5.0–10.0 kg had an increase in the population of active secondary hair follicles (p < 0.05). In conclusion, the fasted live-weight gain during the cashmere non-growing period had a significant effect on secondary hair follicle activity and cashmere production performance in cashmere goats. Since fasted live-weight gain reflects nutritional level to a certain extent, this study suggests that nutritional manipulations such as supplementary feeding during cashmere non-growing periods can increase cashmere production performance. However, specific nutritional manipulations during the cashmere non-growing period need further research to increase cashmere production performance.

Increasing the allowable gas pressure of underground gas storage (UGS) is one of the most effective methods to increase its working gas capacity. In this context, hydraulic fracturing tests are implemented on the target formation for the UGS construction of Jintan salt caverns, China, in order to obtain the minimum principal in situ stress and the fracture breakdown pressure. Based on the test results, the maximum allowable gas pressure of the Jintan UGS salt cavern is calibrated. To determine the maximum allowable gas pressure, KING-1 and KING-2 caverns are used as examples. A three-dimensional (3D) geomechanical model is established based on the sonar data of the two caverns with respect to the features of the target formation. New criteria for evaluating gas penetration failure and gas seepage are proposed. Results show that the maximum allowable gas pressure of the Jintan UGS salt cavern can be increased from 17 MPa to 18 MPa (i.e. a gradient of about 18 kPa/m at the casing shoe depth). Based on numerical results, a field test with increasing maximum gas pressure to 18 MPa has been carried out in KING-1 cavern. Microseismic monitoring has been conducted during the test to evaluate the safety of the rock mass around the cavern. Field monitoring data show that KING-1 cavern is safe globally when the maximum gas pressure is increased from 17 MPa to 18 MPa. This shows that the geomechanical model and criteria proposed in this context for evaluating the maximum allowable gas pressure are reliable. Keywords: Underground gas storage (UGS) salt cavern, In situ stress testing, Maximum gas pressure, Gas penetration failure, Microseismic monitoring

The tumor mutational burden (TMB) has been reported as a predictive marker of the response to immune checkpoint inhibition (ICI) therapy in previous melanoma clinical trials. However, the TMB alone is not sufficient to accurately predict immunotherapy benefit. Additional biomarkers are needed for better stratification of immunotherapy-sensitive patients. In the present study, mutation data and survival information of patients with melanoma were collected from several immunotherapy studies, and tumor heterogeneity was estimated using mutant-allele tumor heterogeneity (MATH). The benefit score was defined as the ratio between the TMB and tumor heterogeneity, and optimal critical values were selected to group patients and evaluate their response to ICI treatment. The benefit score significantly improved the performance of stratifying the overall survival of patients compared with the TMB alone as a predictor in two independent cohorts (p = 0.0068 vs. p = 0.1 and p = 0.045 vs. p = 0.13), in which patients were treated with Ipilimumab and Nivolumab, respectively. In another cohort of patients with melanoma receiving mixed ICI treatment, the benefit score was also positively associated with higher overall survival (p = 0.022) and outperformed the TMB alone, with a significance of p = 0.089. The benefit score showed a positive correlation with clonal TMB, a reported immunotherapy marker, and exceeded it in immunotherapy response prediction. Besides, a high benefit score was found to be associated with higher proportions of natural killer cells, lower proportions of M2 macrophages and elevated CD8 T cells, all of which favor ICI therapy. In summary, tumor heterogeneity combined with the TMB showed superior efficacy in predicting the response to ICI therapy. This might further help to delineate the mechanisms of immunotherapy in patients with melanoma.

Lamin A/C has been identified as a target antigen of anti-endothelial cell antibodies in vasculitis. Behçet’s disease (BD) is a chronic vasculitis with unclear pathogenesis. Self-antibodies have been found to play an important role in the pathological process of BD. The aim of this study was to verify whether lamin A/C is an autoantigen of BD. First, the human lamin A/C protein was cloned and purified and verified by Western blotting. Next, a homemade ELISA kit was used to test the presence of anti-lamin A/C antibodies in BD patients. This is the first time it has been certified that lamin A/C is an autoantigen of BD. The reactivity of serum IgG against recombinant human lamin A/C was detected in 7 of 31 BD patients (23%) and 3 of 32 healthy controls (HC) (9%).

Different operations make the borehole temperature change and cause periodic stresses, which often cause variations in the stress state of the sheath or damage. In this paper, the effect of temperature on sheath integrity is investigated. First, the mechanical model of sheath is established and analyzed by shakedown theory. Then, compression experiments of well cement at different temperatures are carried out, and the law of mechanical properties with temperature is obtained. Finally, combining the theoretical analysis and mechanical experiments, the results show that (1) when only the temperature inside the sheath cyclically varies, the negative influence of temperature caused by the practical operations can be negligible. (2) When the internal pressure and temperature act together, the effect of temperature on the sheath is reflected in temperature stress and the change of the cement properties. (3) With the increase of temperature difference (∆T), the cohesion of cement decreases while the internal friction angle increases, and the plasticity characteristics of the cement are enhanced, and the negative effect on the Pmax ascends slowly. (4) The temperature stress is in a positive relationship with the ∆T, and its weakening on the Pmax is about 6% to 7%. (5) Combining the temperature stress and the change of the cement properties, total negative effect of temperature on the sheath accounts for 10% to 12%, when ∆T ranges from 60 to 110 °C.

Based on a brief overview on the determination methods of formation pressure and their features, the major principle of formation pressure testing while drilling (FPTWD) and existing physical simulation systems was introduced, and the deficiency of the existing physical simulation systems was also discussed. A laboratory high-precision physical simulation system was therefore developed to simulate the downhole testing environment and testing process of FPTWD. The present experimental system was designed to endure pressures up to 20,000 psi, and the relative control accuracy of pressure is approximately 0.02% FS. Two kinds of man-made specimens with the permeability of 10–110 mD were used to test the pressure response and to verify the present physical simulation system. The debugging results indicated that the variation amplitude under the stable condition is approximately 0.07 psi, 0.08 psi, 0.11 psi, and 0.11 kN for the annular pressure, pore pressure, confining pressure, and thrust force, respectively. Thus, the high control accuracy is approximately ±1.0 psi under the stable conditions. The experimental results indicated that the pressure drawdown declines rapidly in the stage of withdrawing formation fluids and then recovers slowly. The pressure drop amplitude also decreases with permeability, while the pressure buildup amplitude increases with permeability. The tendency of pressure change is nearly the same for both the present and the previous systems, and the pressure curve of the present system is much smoother and better than that of the previous system. The relative error of explaining formation pressure is less than 1% and 4% for the present and the previous systems, respectively. In addition, this physical simulation system has important applications to verify the interpretation model, to analyze pressure response recorded by FPTWD tools, to test the capability and design of FPTWD tools, and to calibrate the formation pressure, formation parameters, and instrument factors.

We investigated the mechanical properties of mature bedding shale under cyclic loading conditions, with an application to the design of hydraulic fracturing in shale gas wells. Laboratory experiments were conducted on shale samples under two principal loading orientations. Testing results showed that accumulated fatigue damage occurs in a three-stage process. Analysis of fatigue damage at different maximum stress levels shows that fatigue life increases as a power-law function with maximum stress decreasing. And the maximum stress significantly affects the fatigue life. Further, the elastic part of shale rock deformation was recovered in the unloading process, whereas the irreversible deformation remained. The irreversible deformation, growth trend, and accumulation of the total fatigue were directly related to the fatigue damage. This process can be divided into 3 stages: an initial damage stage, a constant velocity damage stage, and an accelerated damage stage, which accounted for about one-third of the fatigue damage. Shale rock is a nonhomogeneous material, and the bedding is well developed. Its fatigue life differs greatly in two principal loading orientations, even under the same loading conditions. All of these drawn conclusions are of great importance for design of hydraulic fracturing in shale gas wells.

A number of large underground oil storage spaces will be constructed in deep salt mines in China in the coming years. According to the general geological survey, the first salt cavern oil storage base of China is planned to be built in Jintan salt mine. In this research, the geological feasibility of the salt mine for oil storage is identified in detail as follows. (1) The characteristics of regional structure, strata sediment, and impermeable layer distribution of Jintan salt mine were evaluated and analyzed. (2) The tightness of cap rock was evaluated in reviews of macroscopic geology and microscopic measuring. (3) According to the geological characteristics of Jintan salt mine, the specific targeted formation for building underground oil storage was chosen, and the sealing of nonsalt interlayers was evaluated. (4) Based on the sonar measuring results of the salt caverns, the characteristics of solution mining salt caverns were analyzed. In addition, the preferred way of underground oil storage construction was determined. (5) Finally, the results of closed well observation in solution mining salt caverns were assessed. The research results indicated that Jintan salt mine has the basic geological conditions for building large-scale underground oil storage.

A linear theoretical model is established for the dynamics of a hanging vertical cantilevered pipe which is subjected concurrently to internal and reverse external axial flows. Such pipe systems may have instability by flutter (amplified oscillations) or static divergence (buckling). The pipe system under consideration is a slender flexible cantilevered pipe hanging concentrically within an inflexible external pipe of larger diameter. From the clamped end to the free end, fluid is injected through the annular passage between the external pipe and the cantilevered pipe. When exiting the annular passage, the fluid discharges in the counter direction along the cantilevered pipe. The inflexible external pipe has a variable length and it can cover a portion of the length of the cantilevered pipe. This pipe system has been applied in the solution mining and in the salt cavern underground energy storage industry. The planar motion equation of the system is solved by means of a Galerkin method, and Euler–Bernoulli beam eigenfunctions are used as comparison functions. Calculations are conducted to quantify the effects of different confinement conditions (i.e., the radial confinement degree of the annular passage and the confined-flow length) on the cantilevered pipe stability, for a long leaching-tubing-like system. For a long system, an increase in the radial confinement degree of the annular passage and the confined-flow length gives rise to a series of flutter and divergence. Additionally, the effect of the cantilevered pipe length is studied. Increasing the cantilevered pipe length results in an increase of the critical flow velocity while a decrease of the associated critical frequency. For a long enough system, the critical frequency almost disappears.

Due to the uncertainty of formation properties and improper wellbore stability analysis methods, the input parameters are often uncertain and the required mud weight to prevent wellbore collapse is too large, which might cause an incorrect result. However, the uncertainty evaluation of input parameters and their influence on safe mud weight window (SMWW) is seldom investigated. Therefore, the present paper aims to propose an uncertain evaluation method to evaluate the uncertainty of SMWW. The reliability assessment theory was introduced, and the uncertain SMWW model was proposed by involving the tolerable breakout, the Mogi-Coulomb (MG-C) criterion and the reliability assessment theory. The influence of uncertain parameters on wellbore collapse, wellbore fracture and SMWW were systematically simulated and investigated by utilizing Monte Carlo simulation. Finally, the field observation of well SC-101X was reported and discussed. The results indicated that the MG-C criterion and tolerable breakout is recommended for wellbore stability analysis. The higher the coefficient of variance is, the higher the level of uncertainty is, the larger the impact on SMWW will be, and the higher the risk of well kick, wellbore collapse and fracture will be. The uncertainty of basic parameters has a very significant impact on SMWW, and it cannot be ignored. For well SC-101X, the SMWW predicted by analytical solution is 0.9921–1.6020 g/cm3, compared to the SMWW estimated by the reliability assessment method, the reliability assessment method tends to give a very narrow SMWW of 1.0756–1.0935 g/cm3 and its probability is only 80%, and the field observation for well kick and wellbore fracture verified the analysis results. For narrow SMWW formation drilling, some kinds of advanced technology, such as the underbalanced drilling (UBD), managed pressure drilling (MPD), micro-flow drilling (MFD) and wider the SMWW, can be utilized to maintain drilling safety.

Deep carbonate reservoirs are rich in oil and gas resources. However, due to poor pore connectivity and low permeability, it is necessary to adopt hydraulic fracturing technology for their development. The mechanism of hydraulic fracturing for fracture initiation and propagation in carbonate rocks remains unclear, especially with regard to selection of the type of fracturing fluid and the fracturing parameters. In this article, an experimental study focusing on the mechanisms of hydraulic fracturing fracture initiation and propagation is discussed. Several factors were studied, including the type of injecting fracturing fluids, pump flow rate, fracturing pressure curve characteristics, and fracture morphology. The results showed the following: (1) The viscosity of fracturing fluid had a significant effect on fracturing breakdown pressure. Under the same pump flow rate, the fracturing breakdown pressure of slick water was the lowest. Fracturing fluids with low viscosity could easily activate weakly natural fractures or filled fractures, leading to open microcracks, and could effectively reduce the fracturing breakdown pressure. (2) The fluctuations in fracturing pump pressure corresponded with the acoustic emission hits and changes in radial strain; for every drop of fracturing pressure, acoustic emission hits and changes in radial strain were mutated. (3) Under the same fracturing fluid, the pump flow rate mainly affected fracturing breakdown pressure and had little effect on fracture morphology. (4) The width of the main fracture was affected by the viscosity and pump flow rate. Maximum changes in radial strain at the fracturing breakdown pressure point occurred when the fracturing fluid was guar gum. (5) With gelled acid and cross-linked acid fracturing, the main fractures were observed on the surface. The extension of the fracturing crack was mainly focused near the crack initiation parts. The crack expanded asymmetrically; the wormhole was dissolved to break through to the surface of the specimen. (6) The dissolution of gelled acid solution could increase the width of the fracturing crack and improve the conductivity of carbonate reservoirs.

Salt deposits are commonly regarded as ideal hosts for geologic energy reservoirs. Underground cavern construction-induced damage in salt is reduced by self-healing. Thus, studying the influencing factors on such healing processes is important. This research uses ultrasonic technology to monitor the longitudinal wave velocity variations of stress-damaged rock salts during self-recovery experiments under different recovery conditions. The influences of stress-induced initial damage, temperature, humidity, and oil on the self-recovery of damaged rock salts are analyzed. The wave velocity values of the damaged rock salts increase rapidly during the first 200 h of recovery, and the values gradually increase toward stabilization after 600 h. The recovery of damaged rock salts is subjected to higher initial damage stress. Water is important in damage recovery. The increase in temperature improves damage recovery when water is abundant, but hinders recovery when water evaporates. The presence of residual hydraulic oil blocks the inter-granular role of water and restrains the recovery under triaxial compression. The results indicate that rock salt damage recovery is related to the damage degree, pore pressure, temperature, humidity, and presence of oil due to the sealing integrity of the jacket material.

Natural fractures (NFs) have been recognized as the dominant factors that increase hydraulic fracture complexity and reservoir productivity. However, the interactions between hydraulic and natural fractures are far from being fully understood. In this study, a two-dimensional numerical model based on the displacement discontinuity method (DDM) has been developed and used to investigate the interaction between hydraulic and pre-existing natural fractures. The inelastic deformation, e.g., stick, slip and separation, of the geologic discontinuities is captured by a special friction joint element called Mohr-Coulomb joint element. The dynamic stress transfer mechanisms between the two fracture systems and the possible location of secondary tensile fracture that reinitiates along the opposite sides of the NF are discussed. Furthermore, the model results are validated by a series of large tri-axial hydraulic fracture (HF) tests. Both experimental and numerical results showed that the displacements and stresses along the NFs are all in highly dynamic changes. When the HF is approaching the NF, the HF tip can exert remote compressional and shear stresses on the NF interface, which results in the debonding of the NF. The location and value of the evoked stress is a function of the far-field horizontal differential stress, inclination angle of the NF, and the net pressure used in fracturing. For a small approaching angle, the stress peak is located farther away from the intersection point, so an offset fracture is more likely to be generated. The cemented strength of the NF also has an important influence on the interaction mechanism. Weakly bonded NF surfaces increase the occurrence of a shear slippage, but for a moderate strength NF, the hybrid failure model with both tensile and shear failures, and conversion may appear.

Strength anisotropy is one of the most distinct features of anisotropic rocks, and it also normally reveals strong anisotropy in Brazilian test Strength (“BtS”). Theoretical research on the “BtS” of anisotropic rocks is seldom performed, and in particular some significant factors, such as the anisotropic tensile strength of anisotropic rocks, the initial Brazilian disc fracture points, and the stress distribution on the Brazilian disc, are often ignored. The aim of the present paper is to review the state of the art in the experimental studies on the “BtS” of anisotropic rocks since the pioneering work was introduced in 1964, and to propose a novel theoretical method to underpin the failure mechanisms and predict the “BtS” of anisotropic rocks under Brazilian test conditions. The experimental data of Longmaxi Shale-I and Jixi Coal were utilized to verify the proposed method. The results show the predicted “BtS” results show strong agreement with experimental data, the maximum error is only ~6.55% for Longmaxi Shale-I and ~7.50% for Jixi Coal, and the simulated failure patterns of the Longmaxi Shale-I are also consistent with the test results. For the Longmaxi Shale-I, the Brazilian disc experiences tensile failure of the intact rock when 0° ≤ βw ≤ 24°, shear failure along the weakness planes when 24° ≤ βw ≤ 76°, and tensile failure along the weakness planes when 76° ≤ βw ≤ 90°. For the Jixi Coal, the Brazilian disc experiences tensile failure when 0° ≤ βw ≤ 23° or 76° ≤ βw ≤ 90°, shear failure along the butt cleats when 23° ≤ βw ≤ 32°, and shear failure along the face cleats when 32° ≤ βw ≤ 76°. The proposed method can not only be used to predict the “BtS” and underpin the failure mechanisms of anisotropic rocks containing a single group of weakness planes, but can also be generalized for fractured rocks containing multi-groups of weakness planes.

IgG4-related disease (IgG4-RD) is a chronic systemic disease involved in many organs and tissues. As only limited autoantigens have been found since the beginning of this century, the aim of this study was to reveal new candidate autoantigens of IgG4-RD.Multiple cell lines including HT-29, EA.hy926, HEK 293 and HepG2 were used to test the binding ability of circulating autoantibodies from IgG4-RD sera. The amino-acid sequence was then analyzed by matrix-assisted laser desorption/ionization time-of-flight tandem (MALDI-TOF/TOF) mass spectrometry. After the cloning and expression of recombinant putative autoantigen in a bacterial expression system, the corresponding immuno assay was set up and utilized to observe the prevalence of serum autoantibodies in a large set of confirmed clinical samples.One positive autoantigen was identified as prohibitin. ELISA analysis showed that a majority of patients with IgG4-RD have antibodies against prohibitin. Anti-prohibitin antibodies were present in the sera of patients with definite autoimmune pancreatitis (25/34; 73.5%), Mikulicz's disease (8/15; 53.3%), retroperitoneal fibrosis (6/11; 54.5%), other probable IgG4-RD (26/29; 89.7%) and Sjögren's syndrome (4/30; 13.3%) but not in apparently healthy donors (1/70; 1.4%).An association between prohibitin and patients with some IgG4-RD was observed, although the results were quite heterogeneous among different individuals within autoimmune pancreatitis, Mikulicz's disease and retroperitoneal fibrosis.

Behçet's disease (BD) is a chronic inflammatory disease with multisystem involvement, and it is listed as a rare disease in the United States but is common in the Middle East, China, and Japan. The aim of this study was to identify novel autoantigens in Chinese patients with BD. First, the candidate autoantigens were screened by Western blotting, and the sequences of putative antigens were identified by LC-MALDI-TOF/TOF mass spectrometry. Next, the screened protein was cloned, expressed and purified. Then, an optimized ELISA was developed, and the serological criteria were evaluated using a large number of confirmed patients. One antigen with a molecular weight of approximately 28 kDa was identified as electron transfer flavoprotein subunit beta (ETFB). Positive reactivity was detected in recombinant human ETFB sera from 38 of 92 BD patients (41 %) and 1 of 90 healthy controls (1 %).

Knowledge about the permeability of surrounding rock (salt rock and mudstone interlayer) is an important topic, which acts as a key parameter to characterize the tightness of gas storage. The goal of experiments that test the permeability of gas storage facilities in rock salt is to develop a synthetic analogue to use as a permeability model. To address the permeability of a mudstone/salt layered and mixed rock mass in Jintan, Jiangsu Province, synthetic mixed and layered specimens using the mudstone and the salt were fabricated for permeability testing. Because of the gas “slippage effect”, test results are corrected by the Klinkenberg method, and the permeability of specimens is obtained by regression fitting. The results show that the permeability of synthetic pure rock salt is 6.9 × 10−20 m2, and its porosity is 3.8%. The permeability of synthetic mudstone rock is 2.97 × 10−18 m2, with a porosity 17.8%. These results are close to those obtained from intact natural specimens. We also find that with the same mudstone content, the permeability of mixed specimens is about 40% higher than for the layered specimens, and with an increase in the mudstone content, the Klinkenberg permeability increases for both types of specimens. The permeability and mudstone content have a strong exponential relationship. When the mudstone content is below 40%, the permeability increases only slightly with mudstone content, whereas above this threshold, the permeability increases rapidly with mudstone content. The results of the study are of use in the assessment of the tightness of natural gas storage facilities in mudstone-rich rock salt formations in China.

Live bacteria and archaea have been isolated from several rock salt deposits of up to hundreds of millions of years of age from all around the world. A key factor affecting their longevity is the ability to keep their genomic DNA intact, for which efficient repair mechanisms are needed. Polyploid microbes are known to have an increased resistance towards mutations and DNA damage, and it has been suggested that microbes from deeply buried rock salt would carry several copies of their genomes. Here, cultivable halophilic microbes were isolated from a surface sterilized middle-late Eocene (38-41 million years ago) rock salt sample, drilled from the depth of 800 m at Yunying salt mine, China. Eight unique isolates were obtained, which represented two haloarchaeal genera, Halobacterium and Halolamina. We used real-time PCR to show that our isolates are polyploid, with genome copy numbers of 11-14 genomes per cell in exponential growth phase. The ploidy level was slightly downregulated in stationary growth phase, but the cells still had an average genome copy number of 6-8. The polyploidy of halophilic archaea living in ancient rock salt might be a factor explaining how these organisms are able to overcome the challenge of prolonged survival during their entombment.