Review on the progress for physical simulation for gas reservoirs co-production in multi-pressure system

The gas reservoirs co-production in multi-pressure system is one of the important measures to improve the development efficiency of the superposed gas-bearing systems. However, the co-production effect is not ideal due to the special reservoir forming background. The mechanism of co-production and high-efficient development of the multi-pressure system has become an key scientific problem, which restricts the efficient exploration and development of superposed gas-bearing systems. This paper focuses on the gas reservoirs co-production in multi-pressure system, and divides the physical simulation types of co-production into two separate fields: coalbed methane and non coalbed methane. It clarifies the current research status of gas reservoirs co-production in multi-pressure system from the aspects of device functions and characteristics, understanding of co-production, and existing problems. Firstly, the large-scale physical simulation test device can effectively eliminate or weaken the problems of homogeneous single-type reservoir samples, single monitoring data means and single stress loading form caused by paralleling multiple core grippers to build the physical simulation model. The development direction of the physical simulation for co-production in multi-pressure system should be to achieve true three-dimensional heterogeneous complex in-situ stress state of large-scale heterogeneous multi-type reservoir samples. The characteristics of fluid pressure transmission between adjacent reservoirs, the inter-layer crossflow, the multi-phase natural gas symbiosis should be considered. On this basis, the sensitivity of co-production of multi-pressure system to reservoir physical properties was deeply summarized. The differences in inter-layer pressure difference, permeability, effective stress, water saturation and other factors may induce the fluid interference and reservoir gas production damage, and optimizing co-production style may be a way to reduce the fluid interference and reservoir gas production damage. In totally, the next research should focus on exploring the influence of the coupling effect of low porosity and low permeability, gas water two-phase flow, multiphase gas symbiosis and coexistence of multiple types of reservoirs on the dynamic evolution law of reservoir-wellbore flow field induced by co-production fluid interference, clarifying the reservoir damage and its mechanism of different phase fluid intrusions on the reservoir, and revealing the coupling flow characteristics of inter-layer crossflow and wellbore pipe flow considering the fluid interference effect

Influence of coupled effect among flaw parameters on strength characteristic of precracked specimen: Application of response surface methodology and fractal method

Hydraulic slotting is an effective method for enhanced coalbed methane (ECBM) recovery, and it has been widely employed in China. Although there have been many studies of this technique, the influence of slot parameters on the strength characteristic of the coal, which is an important factor that affects the permeability enhancement effect, has rarely been studied. Thus, only limited information is available regarding the pressure relief and permeability enhancement mechanisms of this technique. In the current study, the influence of flaw parameters on the compressive strength of a precracked sample under biaxial compression is discussed. The results indicate that an increase in the flaw length and width has a negative effect on the compressive strength, whereas an increase in the flaw inclination angle has a positive effect on the compressive strength. The results of the response surface methodology (RSM) indicate that the interactions among the flaw parameters have a significant influence on the compressive strength. The propagation patterns of cracks are quantified by the fractal dimension, which is used to explore the mechanism of compressive strength variation with changes in the flaw parameters. The study results indicate that the variation in the flaw parameters changes the propagation pattern of cracks, resulting in different compressive strengths. In addition, an opposite variation trend of the compressive strength and fractal dimension with flaw parameters is also observed. The research results are expected to guide the field application of hydraulic slotting

Novel integrated techniques of drilling-slotting-separation-sealing for enhanced coal bed methane recovery in underground coal mines

Coal bed Methane (CBM), a primary component of natural gas, is a relatively clean source of energy. Nevertheless, the impact of considerable coal mine methane emission on climate change in China has gained an increasing attention as coal production has powered the country's economic development. It is well-known that coal bed methane is a typical greenhouse gas, the greenhouse effect index of which is 30 times larger than that of carbon dioxide. Besides, gas disasters such as gas explosive and outburst, etc. pose a great threat to the safety of miners. Therefore, measures must be taken to capture coal mine methane before mining. This helps to enhance safety during mining and extract an environmentally friendly gas as well. However, as a majority of coal seams in China have low-permeability, it is difficult to achieve efficient methane drainage. Enhancing coal permeability is a good choice for high-efficiency drainage of coal mine methane. In this paper, a modified coal-methane co-exploitation model was established and a combination of drilling–slotting-separation–sealing was proposed to enhance coal permeability and CBM recovery. Firstly, rapid drilling assisted by water-jet and significant permeability enhancement via pressure relief were investigated, guiding the fracture network formation around borehole for high efficient gas flow. Secondly, based on the principle of swirl separation, the coal–water–gas separation instrument was developed to eliminate the risk of gas accumulation during slotting and reduce the gas emission from the ventilation air. Thirdly, to improve the performance of sealing material, we developed a novel cement-based composite sealing material based on the microcapsule technique. Additionally, a novel sealing–isolation combination technique was also proposed. Results of field test indicate that gas concentration in slotted boreholes is 1.05–1.91 times higher than that in conventional boreholes. Thus, the proposed novel integrated techniques achieve the goal of high-efficiency coal bed methane recovery

Experimental method for optimizing the molding conditions of hot-pressed briquette

In response to the problems of low strength and high permeability of coal materials in the current physical simulation test of coal mine gas dynamics, a set of experimental research methods for optimizing the molding conditions of hot-pressed briquette. Firstly, a hot-pressed briquette test system was independently established and the advantages and future improvement directions of the test system were summarized. At the same time, based on the Horsfield dense stacking theory, the optimal preparation plan for coal briquette materials was formulated. Finally, a molding condition optimization method was developed that combines the Markov distance measurement method and the golden section method. To verify the effectiveness of the experimental method, the secondary carbonization experiments of briquette were conducted under different molding pressure conditions by controlling the molding temperature to 311.8 ℃, heating rate to 5 ℃/min, and holding time to 5.3 h. The response characteristics of the microstructure, physical and mechanical properties, and permeability characteristics of the hot-pressed briquette under different molding pressure conditions were studied. The results show that with the increase of molding pressure, the total porosity gradually decreases, and the uniaxial compressive strength shows a trend of first increasing and then decreasing. The main forms of failure are block spalling and longitudinal fracture. The initial permeability shows a trend of first decreasing and then increasing, while the minimum permeability shows a trend of first decreasing, then increasing and then decreasing. Using the specific values of each molding condition as the test points, and the key parameters of hot-pressed coal and raw coal as the evaluation parameters, a sample matrix was constructed to calculate the Mahalanobis distance between hot-pressed briquette and raw coal under each molding condition, and then optimize the experimental interval using the golden section method. The optimized final molding pressure is 80 MPa. Under these molding conditions, the density, uniaxial compressive strength, and initial permeability of the hot-pressed briquette produced are 1.137 g/cm3, 12.21 MPa, and 1.32 × 10−15 m2, respectively. They are highly similar to the 1.132 g/cm3, 12.83 MPa, and 1.08 × 10−15 m2 of the raw coal, achieving the goal of improving the strength of the briquette and reducing the permeability of the briquette

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

Variation in the Pore Structure of Coal after Hydraulic Slotting and Gas Drainage

The integration of hydraulic slotting and gas drainage techniques has become a mainstream technique for enhancing permeability in coal seams with low permeability. However, the mechanism of action of this process is unclear. In this paper, field experiment and laboratory tests are described that aim at elucidating this process. Given the sensitivity and accuracy of test methods and their corresponding determination principles, a combination of mercury intrusion porosimetry and nitrogen gas adsorption was proposed as a complementary technique and the pore-size distribution (PSD) was obtained. It is shown that the proportion of minipores decreases remarkably, whereas that of the macropores gradually increases with the decrease in the distance from the slotted borehole. By contrast, the mesopores and micropores present insignificant changes. Meanwhile, the adsorption pore and the seepage pore show a similar variation in tendency with the minipores and macropores, respectively. Moreover, the specific surface area decreases substantially with the decrease in borehole distances. The integration of hydraulic slotting and gas drainage can lower the gas-adsorption properties and enhance the gas-seepage capacity within the disturbed zone significantly. The paper highlights the guiding factors for improving the enhanced coal bed methane recovery

Cyber security detection and monitoring at IHEP private cloud for web services

To improve hardware utilization and save manpower in system maintenance, most of the web services in IHEP have been migrated to a private cloud build upon OpenStack. However, cyber security attacks becomes a serious threats to the cloud progressively. Therefore, a cyber security detection and monitoring system is deployed for this cloud platform. This system collects various security related logs as data sources, and processes them in a framework composed of open source data store, analysis and visualization tools. With this system, security incidents and events can be handled in time and rapid response can be taken to protect cloud platform against cyber security threats