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Lateral flow assay (LFA) has firmly established itself as a prominent technique for qualitative assessments. However, its potential in quantitative analysis remains limited. In this study, we adapted the laser-assisted absorption measurement of LFA for quantitative detection. LFA assay relies on immobilization of colloidal gold nanoparticles conjugated to the target analyte on the test strip. The abundance of these gold nanoparticles can be quantified by absorption measurement, allowing to determine the concentration of analytes. Rigorous experimental validation of the laser-assisted technology was performed by testing a cohort of 20 patients for hepatitis B surface antigen (HBsAg). Notably, our results show that the laser-assisted LFA and the gold standard technique like enzyme-linked immunosorbent assay are similar statistically.

Abstract Background Natural life systems can be significantly modified at the genomic scale by human intervention, demonstrating the great innovation capacity of genome engineering. Large epi-chromosomal DNA structures were established in Escherichia coli cells, but some of these methods were inconvenient, using heterologous systems, or relied on engineered E. coli strains. Results The wild-type model bacterium E. coli has a single circular chromosome. In this work, a novel method was developed to split the original chromosome of wild-type E. coli. With this method, novel E. coli strains containing two chromosomes of 0.10 Mb and 4.54 Mb, and 2.28 Mb and 2.36 Mb were created respectively, designated as E. coli 0.10/4.54 and E. coli 2.28/2.36. The new chromosomal arrangement was proved by PCR amplification of joint regions as well as a combination of Nanopore and Illumina sequencing analysis. While E. coli 0.10/4.54 was quite stable, the two chromosomes of E. coli 2.28/2.36 population recombined into a new chromosome (Chr.4.64MMut), via recombination. Both engineered strains grew slightly slower than the wild-type, and their cell shapes were obviously elongated. Conclusion Finally, we successfully developed a simple CRISPR-based genome engineering technique for the construction of multi-chromosomal E. coli strains with no heterologous genetic parts. This technique might be applied to other prokaryotes for synthetic biology studies and applications in the future.

Abstract Synthetic biology has been represented by the creation of artificial life forms at the genomic scale. In this work, a CRISPR‐based chromosome‐doubling technique is designed to first construct an artificial diploid Escherichia coli cell. The stable single‐cell diploid E. coli is isolated by both maximal dilution plating and flow cytometry, and confirmed with quantitative PCR, fluorescent in situ hybridization, and third‐generation genome sequencing. The diploid E. coli has a greatly reduced growth rate and elongated cells at 4–5 µm. It is robust against radiation, and the survival rate after exposure to UV increased 40‐fold relative to WT. As a novel life form, the artificial diploid E. coli is an ideal substrate for research fundamental questions in life science concerning polyploidy. And this technique may be applied to other bacteria.

On the basis of analyzing the fluid phase behavior during the transformation from gas reservoir to gas storage, a mathematical model and an experimental simulation method are established to describe the oil-gas phase behavior during the whole injection- production process of gas storage. The underground gas storage in the Liaohe Shuang 6 gas reservoir with oil rim is taken as a typical example to verify the reliability and accuracy of the mathematical model and reveal characteristics and mechanisms of fluid phase behavior. In the gas injection stage of the gas storage, the phase behavior is characterized by mainly evaporation and extraction and secondarily dissolution and diffusion of gas in the cap to oil in the oil rim of the reservoir; the gas in gas cap increases in light component content, decreases in contents of intermediate and heavy components, and increases in density and viscosity. The oil of the ring decreases in content of heavy components, increases in contents of light and intermediate components, decreases in density and viscosity, and increases in volume factor and solution gas oil ratio. In the stable operation stage of periodic injection-production of gas storage, the phase behavior shows that the evaporation and extraction capacity of injection gas in the cap to oil rim is weakened step by step, the phase behavior gradually changes into dissolution and diffusion. The gas in gas cap decreases in content of intermediate components, increases in content of light components slowly, and becomes lighter; but changes hardly in density and viscosity. The oil in the oil rim increases in content of heavy components, decreases in content of intermediate components, rises in density and viscosity, and drops in volume factor and solution gas oil ratio.

The geological body management of gas storage is essential for the integrity management of Underground Gas Storage (UGS). However, the integrity management of geological body of gas storage is unclear in concept with fuzzy interface and incomplete system at present, and it is also limited to the integrity evaluation of gas reservoir UGS. Therefore, the concept of geological body of salt-cavern gas storage was defined based on the analysis of research results related to the geological body of gas reservoir UGS, and an integrity management system for geological body of salt-cavern gas storage was established. The results indicate that (1) the integrity management system for geological body of gas storage comprises 4 items, which are based on the hazard identification and data analysis and centered on the risk evaluation and integrity evaluation. (2) The risk analysis for geological body of salt-cavern gas storage focuses on the analysis of the 3 indicators, i.e., salt cavern shrinkage, gas leakage and land subsidence. (3) The salt-cavern storage integrity evaluation is composed of 3 major evaluation technologies, i.e., stability evaluation of salt cavern and surface, fault stability evaluation, and integrity evaluation of interbed and caprock. In conclusion, the establishment of the integrity management system for geological body of salt-cavern storage complements the shortage of geological body management in UGS integrity management, and also provides technical support and new application direction for the safe operation management.

The temperature change under alternating injection-production conditions of underground gas reservoir storage is a key factor for permeability and even deliverability. To explore the temperature-sensitivity of sandstone reservoir permeability and its effect on the deliverability of gas well, experimental studies at multiple rounds were carried out within the realistic temperature range of underground gas storage to simulate more accurately. Results show that: (1) Reservoir permeability negatively correlates with temperature. Permeability exhibits a hysteresis effect under cyclic alternating temperature, and the hysteresis effect gradually weakens with the variation of temperature. (2) Permeability and temperature are linearly correlated, and the hysteresis effect does not change with temperature, which is different from stress-sensitivity. (3) Based on the experimental results, a deliverability equation modified with temperature-sensitivity was established. Calculation shows that, ignoring the temperature-sensitivity of permeability will underestimate the performance of gas well, and its effect will aggravate with the increasing elevation and injection flowrate.

A dynamic transient flow analysis method considering complex factors such as the cyclic injection and production history in a gas field storage facility was established in view of the limitations of the existing methods for transient flow analysis and the characteristics of the injection-production operation of strongly heterogeneous gas reservoirs, and the corresponding theoretical charts were drawn. In addition, an injection-production dynamic transient flow analysis model named “three points and two stages” suitable for an underground gas storage (UGS) well with alternate working conditions was proposed. The “three points” refer to three time points during cyclic injection and production, namely, the starting point of gas injection for UGS construction, the beginning and ending points of the injection-production analysis stage; and the “two stages” refer to historical flow stage and injection-production analysis stage. The study shows that the dimensionless pseudo-pressure and dimensionless pseudo-pressure integral curves of UGS well flex downward in the early stage of the injection and production process, and the dimensionless pseudo-pressure integral derivative curve is convex during the gas production period and concave during the gas injection period, and the curves under different flow histories have atypical features. The new method present in this paper can analyze transient flow of UGS accurately. The application of this method to typical wells in Hutubi gas storage shows that the new method can fit the pressure history accurately, and obtain reliable parameters and results.

In order to provide effective guidance for optimizing and adjusting the maximum operation pressure and dynamic monitoring well pattern of underground gas storages (hereinafter referred as gas storages) and ensure the operation safety of gas storages, this paper takes Xinjiang H gas storage whose storage capacity and peak shaving capacity are the highest in China as the research object to establish a 3D fine geological model and a 3D dynamic geomechanical model in the regional scale of H gas storage based on the alternating change characteristics of geostress field during the high-speed cyclic injection and production of gas storage, combined with the geological, seismic, logging and various laboratory core experiment results. Then, the trap dynamic sealing capacity of H gas storage under the action of alternating stress after 14 years of depletion development of its original gas reservoir and long-term high-speed injection and production after its reconstruction from the gas reservoir was evaluated comprehensively. And the following research results were obtained. First, the change of the formation pressure in H gas storage has a significant effect on the regional geostress field. Second, after the development of the original H gas reservoir, the geostress on the two sides of the fault are greatly different, but the cap rock is not deformed and failed and the reservoir controlling fault as the gas bearing boundary doesn't glide, which ensures the safety of reconstructing H gas reservoir into gas storage. Third, due to the high-speed injection and production of H gas storage, the geostress field becomes more uneven, which has a potential negative impact on the integrity of the injection and production wells of the gas storage. Fourth, during the long-term high-speed injection and production operation of H gas reservoir, the cap rock does not undergo shear and tensile failure, but the numerical simulation of geomechanics shows that the long-term high-speed injection and production of the gas storage results in the relative sliding deformation (maximum about 5 cm) on both sides of H fault in the south of the reservoir, so the sealing capacity of H fault is a weak point impacting the integrity of the gas storage. Fifth, it is recommended to deploy monitoring wells at the upper block of H fault in the south of the gas storage to strengthen the injection and production dynamic monitoring. In conclusion, this study performs a qualitative and quantitative evaluation on the trap dynamic sealing capacity of gas storages rebuilt from gas reservoirs under the action of alternating stress, and it plays an important guiding role in ensuring the long-term injection and production safety of H gas storage.

With the ever-increasing demand for energy, energy mining is developing in the deep underground. In this paper, a conventional triaxial test and a triaxial test at different temperatures (45 MPa confining pressure) have been carried out for sandstone in Hutubi gas storage, and the mechanical properties of the sandstone at different temperatures are analyzed. Based on the damage theory, the damaged relationship of sandstone under thermal-mechanical coupling is deduced, and the damage evolution law of sandstone in gas storage is analyzed. The results show that: 1) In the conventional triaxial test, as the confining pressure increases, the peak strength and elastic modulus of the sandstone are higher, and the specimen is partially sheared and damaged. 2) In the triaxial test under the effect of temperature, the peak strength of the sample decreases with the increase of temperature. Compared with the four stages of the conventional triaxial test, the stress-strain curve adds a ductility stage. The failure mode of the sample is mainly micro-cracks extended ductile destruction. 3) Under the thermal-mechanical coupling of sandstone, the higher the test temperature, the greater the initial damage of the sample. With the joint action of axial force and temperature, the damage of specimen becomes more obvious. This research results can provide the experimental basis and mechanism understanding for the analysis of mechanical properties of gas storage sandstone and the application of deep underground engineering.

By conducting relative permeability experiments of multi-cycle gas-water displacement and imbibition on natural cores, we discuss relative permeability hysteresis effect in underground gas storage during multi-cycle injection and production. A correction method for relative permeability hysteresis in numerical simulation of water-invaded gas storage has been worked out using the Carlson and Killough models. A geologic model of water-invaded sandstone gas storage with medium-low permeability is built to investigate the impacts of relative permeability hysteresis on fluid distribution and production performance during multi-cycle injection and production of the gas storage. The study shows that relative permeability hysteresis effect occurs during high-speed injection and production in gas storage converted from water-invaded gas reservoir, and leads to increase of gas-water transition zone width and thickness, shrinkage of the area of high-efficiency gas storage, and decrease of the peak value variation of pore volume containing gas, and then reduces the storage capacity, working gas volume, and high-efficiency operation span of the gas storage. Numerical simulations exhibit large prediction errors of performance indexes if this hysteresis effect is not considered. Killough and Carlson methods can be used to correct the relative permeability hysteresis effect in water-invaded underground gas storage to improve the prediction accuracy. The Killough method has better adaptability to the example model.

Whole-life-cycle integrity management of underground gas storages (UGSs) has been an important link to ensure its long-term safe and efficient operation. At present, the integrity of UGSs in oil/gas fields and its evaluation techniques focus on surface facilities and injection/withdrawal wells, but its geological integrity lacks clear definition and evaluation object and systematic evaluation techniques. In this paper, relevant research achievements were firstly summarized. Then, the concept of geological integrity with the gas-storage geological body as the evaluation object was put forward, and the evaluation system for the geological integrity of such UGSs was established. Finally, UGS geological integrity evaluation was carried out with the Hutubi Underground Gas Storage in Xinjiang as an example. And the following research results were obtained. First, UGS geological integrity is defined as the integrity degree of each component of a gas-storage geological body to meet operation requirements and fulfill seasonal and emergency peak shaving safely and economically during the operation of a UGS. Its connotation is that reservoir of geological body, caprock, fault and trap can supply the customers with gas continuously and stably and ensure the safe operation of the UGS in its service life. And its core lies in keeping the reliability, safety and economy of natural gas storage in the service life of a UGS. Second, the geological integrity evaluation system is composed of four evaluation techniques, including trap effectiveness, caprock integrity, fault stability and reservoir stability. Third, the evaluation results show that the Hutubi Underground Gas Storage has the potential of peak-shaving capacity enhancement by increasing the maximum operation pressure. In conclusion, the establishment of the geological integrity evaluation system for such UGSs improves the UGS integrity evaluation technique system and plays an instructive and practical role in ensuring the long-term safe and efficient operation of UGSs, increasing the maximum operation pressure and improving the peak shaving capacity.

In order to investigate the influence of water content on the damage and degradation characteristics of Hutubi sandstone, different saturation experiments and laboratory mechanical experiments were carried out on Hutubi sandstone. The experimental results show that under uniaxial and triaxial conditions, with the increase in water content, the axial, lateral, and volume deformations gradually increase, and the deformation shows obvious dilatancy characteristics. The deviator stress and elasticity modulus of the sandstone decreased exponentially with the increasing water content. Confining pressure has a significant effect on the strength improvement of sandstone under the constant water content. Based on lognormal distribution, the damage constitutive model of sandstone which can reflect both uniaxial and triaxial condition with different water contents was proposed. The theoretical curves were compared with the experimental curves, and it was found that the theoretical curves and the experimental curves have similar changing trends. It shows the rationality of the statistical damage constitutive model.

Underground gas storages (UGSs) rebuilt from gas reservoirs is the most popular UGS type in the world. It accounts for 75% of the total active gas of all gas storages. In order to design more scientific and reliable geological schemes for constructing the underground gas storages rebuilt from gas reservoirs and optimize the UGS operation parameters, we analyzed the UGS basic characteristics of multi-cycle high-rate injection and production. Then, the dynamic sealing capacity of traps and the water–gas high-speed interactive flow mechanism of UGSs rebuilt from gas reservoirs with complex geological conditions were investigated by both physical simulation and numerical simulation. Finally, the key technologies for evaluating the dynamic sealing capacity of caprocks and faults and the storage capacity parameters were developed. Some results were obtained. First, the alternating stress in the process of UGS injection and production weakens the original static capillary sealing capacity and mechanical integrity of caprocks to different extents, and the trap sealing capacity can be quantified and evaluated comprehensively by using dynamic breakthrough pressures, shear safety indexes and other indicators. Second, a UGS capacity design method based on effective gas-bearing pores was developed according to the local pore-based recovery mechanism revealed in the high-speed gas–water mutual flooding test. Field application in the multi-layer UGS of H shows that these technologies provide an effective guidance for the design of geologic schemes. After five cycles of injection and production, its ramp-up ratio reached 91.8% and the peak shaving capacity increased quickly to 36.3 × 108 m3 from 2.7 × 108 m3 in the early stage of production. Moreover, the operation indicators matched well with the design. Keywords: Underground gas storage rebuilt from gas reservoir, Production mode, Operation law, Dynamic sealing capacity of trap, Evaluation index, Injection–production mechanism, Injector–producer flow, Storage capacity parameter

Abstract: In view of complex geological characteristics and alternating loading conditions associated with cyclic large amount of gas injection and withdrawal in underground gas storage (UGS) of China, a series of key gas storage construction technologies were established, mainly including UGS site selection and evaluation, key index design, well drilling and completion, surface engineering and operational risk warning and assessment, etc. The effect of field application was discussed and summarized. Firstly, trap dynamic sealing capacity evaluation technology for conversion of UGS from the fault depleted or partially depleted gas reservoirs. A key index design method mainly based on the effective gas storage capacity design for water flooded heterogeneous gas reservoirs was proposed. To effectively guide the engineering construction of UGS, the safe well drilling, high quality cementing and high pressure and large flow surface injection and production engineering optimization suitable for long-term alternate loading condition and ultra-deep and ultra-low temperature formation were developed. The core surface equipment like high pressure gas injection compressor can be manufactured by our own. Last, the full-system operational risk warning and assessment technology for UGS was set up. The above 5 key technologies have been utilized in site selection, development scheme design, engineering construction and annual operations of 6 UGS groups, e.g. the Hutubi UGS in Xinjiang. To date, designed main indexes are highly consistent with actural performance, the 6 UGS groups have the load capacity of over 7.5 billion cubic meters of working gas volume and all the storage facilities have been running efficiently and safely. Key words: gas field storage, trap dynamic sealing capacity, key index design, effective storage volume, drilling and completion in ultra-deep and ultra-low pressure formation, alternating load, surface engineering, core equipment, risk assessment and control

Abstract: Due to the significant differences in development modes and operation rules of underground gas storage (UGS) and gas reservoir, the design of UGS construction has its own particularity and complexity. Key evaluation techniques in the process of gas reservoir being converted into underground gas storage were proposed and field application was analyzed. The construction and operation experience of the first batch commercial UGS in China was summarized, the mechanisms of multi-cycle injection and production with large flux in short-term was examined and some concepts were proposed such as the dynamic sealing of traps, the effective pore volume of UGS and the high velocity unstable seepage flow with finite supply. Four key technologies of UGS, i.e., trap sealing evaluation, gas storage parameter design, well pattern optimization and monitoring programs design were created. Preservation condition, storage capacity, effective injection & production and safe operation technology problems of UGS were solved respectively. The geological program design technology system of UGS construction in a gas field was gradually enriched and improved. These technologies have successfully guided geological plan design and implementation of UGS construction in a gas reservoir, the effects of gas storage and peaking capacity of the ramp-up cycles were great, and the actual dynamic was very consistent with design indicators. Key words: underground gas storage in gas field, dynamic sealing, gas storage parameter, productivity evaluation, injection-production well pattern, monitor scheme

Compared with the line-of-sight (LOS) condition, the multipath effect is more serious in the non-line-of-sight (NLOS) condition. Therefore, the LOS and NLOS identification is necessary for the multipath analysis of signal propagation. The commonly used method is the support vector machine (SVM) method with high computational complexity. To tackle this problem, this paper adopts the SVM classifier based on fewer selected features of the normalized power delay profile (PDP). Therein, the PDP can be obtained using the sliding correlation method. The results show that the SVM-based classifier can achieve high accuracy on LOS and NLOS identification. We then analyze the impact of the signal-to-noise ratio (SNR) and transmitting-receiving (Tx-to-Rx) distance on distinguishable multipaths under LOS and NLOS conditions. According to statistical measurement results, a function of distinguishable multipath numbers is established. Finally, we investigate the multipath power and delay parameters of average delay spread and root mean square (RMS) delay spread based on multipath results. The outcomes of this paper provide a useful support for analyzing signal propagation characteristics.

Abstract: In view of the gap between the inflow-performance forecasted by the traditional equation and the actual inflow-performance, experiments of gas-gas alternating seepage flow and gas-water alternating seepage flow were carried out, and a modified equation of inflow-performance relationship considering gas permeability change due to water invasion was established. This equation was verified by example analysis. The experimental results show that: gas permeability of net pay, when water-invaded reservoirs are converted into underground gas storage, is different from that during actual gas field development, in that the value of permeability decreases gradually in gas-water zone while the value increases gradually and even higher than that of original gas field in gas zone as a result of gas water alternative flooding in gas storage. Then one parameter describing the extent of permeability change when gas reservoirs are converted into gas storage was defined based on the result of the experiments, and eventually the traditional equation of inflow-performance relationship was modified to forecast inflow-performance in gas storage based on data from field development. Example analysis result shows that: the modified equation considers the effect of changing permeability, its results agree with the actual inflow-performance, while the result of traditional equation differs greatly from the actual inflow-performance. Key words: underground gas storage, well inflow-performance, percolation experiment, permeability change, gas-water zone, gas zone