210 research outputs found
Influence of geological factors on surface deformation due to hydrocarbon exploitation using time-series InSAR: A case study of Karamay Oilfield, China
Surface deformation due to hydrocarbon extraction from buried reservoirs may gradually evolve to geological hazards, which can undermine the safety of infrastructure facilities. Monitoring the surface deformation and studying on the influencing factors of surface deformation have great significance to ensure the stability of oilfield development, and prevent geological hazards. In this study, Sentinel-1 interferometric synthetic aperture radar (InSAR) data of Karamay Oilfield acquired between January 2018 to December 2020 was used to map how the land surface has deformed in response to hydrocarbon exploitation. Based on the monitoring results of time series InSAR, geological data, and oilfield data, the correlations between the different factors and the surface deformation were analyzed. The results show that the reservoir buried depth, porosity and permeability have an impact on the surface deformation, and the influence on surface uplift is obviously greater than that on surface subsidence. Surface uplift decreases with the increasing buried depth and the decreasing porosity and permeability, and the correlation between porosity and surface uplift is the best. However, the impact is limited in the area with shallow reservoir depth, high porosity, and high permeability, such as the heavy oil blocks in the study area
Massive Access for Future Wireless Communication Systems
Multiple access technology played an important role in wireless communication
in the last decades: it increases the capacity of the channel and allows
different users to access the system simultaneously. However, the conventional
multiple access technology, as originally designed for current human-centric
wireless networks, is not scalable for future machine-centric wireless
networks.
Massive access (studied in the literature under such names as massive-device
multiple access, unsourced massive random access, massive connectivity, massive
machine-type communication, and many-access channels) exhibits a clean break
with current networks by potentially supporting millions of devices in each
cellular network. The tremendous growth in the number of connected devices
requires a fundamental rethinking of the conventional multiple access
technologies in favor of new schemes suited for massive random access. Among
the many new challenges arising in this setting, the most relevant are: the
fundamental limits of communication from a massive number of bursty devices
transmitting simultaneously with short packets, the design of low complexity
and energy-efficient massive access coding and communication schemes, efficient
methods for the detection of a relatively small number of active users among a
large number of potential user devices with sporadic transmission pattern, and
the integration of massive access with massive MIMO and other important
wireless communication technologies. This paper presents an overview of the
concept of massive access wireless communication and of the contemporary
research on this important topic.Comment: A short version has been accepted by IEEE Wireless Communication
Dark Count of 20-inch PMTs Generated by Natural Radioactivity
The primary objective of the JUNO experiment is to determine the ordering of
neutrino masses using a 20-kton liquid-scintillator detector. The 20-inch
photomultiplier tube (PMT) plays a crucial role in achieving excellent energy
resolution of at least 3% at 1 MeV. Understanding the characteristics and
features of the PMT is vital for comprehending the detector's performance,
particularly regarding the occurrence of large pulses in PMT dark counts. This
research paper aims to further investigate the origin of these large pulses in
the 20-inch PMT dark count rate through measurements and simulations. The
findings confirm that the main sources of the large pulses are natural
radioactivity and muons striking the PMT glass. By analyzing the PMT dark count
rate spectrum, it becomes possible to roughly estimate the radioactivity levels
in the surrounding environment.Comment: 10 pages, 8 figures, and 5 table
Study on the radon adsorption capability of low-background activated carbon
Radon is a significant background source in rare event detection experiments.
Activated Carbon (AC) adsorption is widely used for effective radon removal.
The selection of AC considers its adsorption capacity and radioactive
background. In this study, using self-developed devices, we screened and
identified a new kind of low-background AC from Qingdao Inaf Technology Company
that has very high Radon adsorption capacity. By adjusting the average pore
size to 2.3 nm, this AC demonstrates a radon adsorption capacity of 2.6 or 4.7
times higher than Saratech or Carboact activated carbon under the same
conditions.Comment: 21pages, 7 figure
Research on temporal−spatial relationship between ground fracturing wells and underground drilling for substitution drainage of during extraction exhaustion period
In order to make use of the favorable extraction conditions formed by ground fracturing to carry out the underground borehole replacement extraction in the drainage exhaustion period of ground fracturing wells, and form the advanced treatment of ground fracturing wells + underground borehole replacement extraction mode of underground borehole replacement extraction, the temporal-spatial relationship between ground fracturing wells and underground drilling for substitution extraction of during drainage exhaustion period was studied. Through the analysis of the distribution law of fracturing fractures, the investigation of the effect of ground fracturing on enhancing permeability and promoting extraction, and the numerical simulation of the variation law of coal reservoir parameters, the influence and effective range of ground fracturing wells in Lu ’an Mining Area are mastered. Numerical simulation method is used to analyze and determine the optimal temporal-spatial relationship between ground fracturing wells and underground drilling for substitution extraction. Based on the drainage curve of surface fractured wells and the demand of drilling in the drainage exhaustion period, the definition and division method of the drainage exhaustion period of surface fractured wells are discussed, and the discriminant indexes and key time nodes of the drainage exhaustion period of surface fractured wells are put forward. The results show : The effective influence range of ground fracturing wells is 80 m. In this area, the reservoir pressure can be decreased by about 50%, the permeability coefficient can be increased by 0.77−1.40 times, and the average pure volume of single underground drilling for substitution extraction can reach 53.68−131.67 m3/d, which improves the extraction efficiency of downhole drilling. When the position of ground fracturing wells is fixed along the axis of the underground drilling, the shorter the normal distance between the underground drilling and the ground fracturing wells, the better the extraction effect.When the normal distance between the ground fracturing wells and the underground drilling is constant, the best extraction results are achieved when the ground fracturing wells is located in the middle of the axial direction of the underground drilling.The gas production rate of ground fracturing wells is used as an indicator of drainage exhaustion period.And the critical value of the indicator of drainage exhaustion period of surface fractured wells in the Lu'an mine area is 200 m3/d, and the corresponding failure period time node is 8~10 years
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