Influence of Migration and Plugging of Nanoparticles on Coal Permeability in Coal Reservoirs

The plugging of nanopores in low-permeability coal reservoirs is an important factor that affects productivity reduction. However, the mechanism of plugging of the nanopores in coal reservoirs remains unclear. In this study, the coal samples from the Anze coalbed methane block of the North China Oilfield are used as the research object. Experiments are conducted on the mechanism of nanopore plugging by the variation of nanopore permeability based on the pressure oscillation method and the nanopore (scanning electron microscope) method. The research shows that the foreign working fluid invades a coal sample; the sample changes from being hydrophobic to being water absorbent within a certain period. The instability caused by the expansion of coal clay mineral particles promotes the dispersion and shedding of particles, and the migration of particles is accelerated under the shear stress of the working fluid. In addition, the viscosity and pressure difference of the working fluid are important factors that affect particle plugging. The viscosity of the fluid increased by two times, and permeability decreased by 1.21 times. As the pressure difference increases by two times, permeability can be reduced by up to two orders of magnitude. The findings of this study can help for better understanding of the mechanism of plugging of the nanopores in coal reservoirs and the reasons of production reduction in low-permeability coal reservoirs. Such findings provide theoretical support for the selection of the working fluid, and reasonable production pressure difference can effectively reduce the damage on coal permeability in a low-permeability coal reservoir.

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Study on the Coalbed Methane Development under High In Situ Stress, Large Buried Depth, and Low Permeability Reservoir in the Libi Block, Qinshui Basin, China

Advances in Civil Engineering ◽

10.1155/2020/6663496 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Jinkuang Huang ◽

Shenggui Liu ◽

Songlei Tang ◽

Shixiong Shi ◽

Chao Wang

Keyword(s):

Coalbed Methane ◽

Horizontal Wells ◽

In Situ Stress ◽

Low Permeability ◽

Qinshui Basin ◽

Hole Pressure ◽

Bottom Hole ◽

Single Well ◽

Coal Reservoir

Coalbed methane (CBM) has been exploited in the deep area of the coal reservoir (>1000 m). The production of CBM vertical wells is low because of the high in situ stress, large buried depth, and low permeability of the coal reservoir. In this paper, efficient and advanced CBM development technology has been applied in the Libi Block of the Qinshui Basin. According to the characteristics of the coal reservoir in the Libi Block, the coiled tubing fracturing technology has been implemented in four cluster horizontal wells. Staged fracturing of horizontal wells can link more natural fracture networks. It could also expand the pressure drop range and control area of the single well. This fracturing technology has achieved good economic results in the Libi Block, with the maximum production of a single horizontal well being 25313 m3/d and the average single well production having increased by more than 60% from 5000 m3/d to 8000 m3/d. Based on the data regarding the bottom hole pressure, water production, and gas production, the production curves of four wells, namely, Z5P-01L, Z5P-02L, Z5P-03L, and Z5P-04L, were investigated. Furthermore, a production system with slow and stable depressurization was obtained. The bottom hole pressure drops too fast, which results in decreasing permeability and productivity. In this work, a special jet pump and an intelligent remote production control system for the CBM wells were developed; hence, a CBM production technology suitable for the Libi Block was established. The maximum release for the CBM well productivity was obtained, thus providing theoretical and technical support for CBM development with geological and engineering challenges.

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Prediction of high-quality coalbed methane reservoirs based on the fuzzy gray model: An investigation into coal seam No. 8 in Gujiao, Xishan, North China

Energy Exploration & Exploitation ◽

10.1177/0144598720901444 ◽

2020 ◽

Vol 38 (4) ◽

pp. 1054-1081

Author(s):

Huang Bo ◽

Qin Yong ◽

Wanhong Zhang ◽

Qiming Zheng ◽

Songlin Shi ◽

...

Keyword(s):

Mechanical Properties ◽

Coal Seam ◽

Coalbed Methane ◽

Low Permeability ◽

Gray Model ◽

High Quality ◽

The North ◽

Reservoir Permeability ◽

Geological Factors ◽

Coalbed Methane Production

Coalbed methane (CBM) resources are abundant in the Gujiao block, Xishan coalfield, China. However, few studies have been conducted on the coalbed methane geology of the Gujiao block. In the present study, based on logging responses and numerical simulations, the coal structures of coal seam No. 8 of this block were identified, and the mechanical properties of the coal and its roof/floor were calculated. The geological factors influencing the coalbed methane reservoir were quantitatively characterized according to the fuzzy gray model. High-quality coalbed methane reservoirs in the No. 8 coal were predicted and classified using the model, and some suggestions on rational exploitation were determined. Reservoirs of the No. 8 coal are dominated by the III-type, followed by the II- and IV-types. The III-type reservoirs are the most common, and primarily developed at the Xiqu, Zhenchengdi, Malan, and Tunlan coal mines in the north of the studied area. The III-type reservoirs represent low coalbed methane contents, high thickness proportions of granulated-mylonitized coal, and low burial depths. The II-type reservoirs are primarily developed close to the axis of the Malan syncline and in the south and northwest of the studied area, and have low permeability, less significant differences between the mechanical properties of coals and their roofs and floors, and low reservoir pressure gradients. The IV-type reservoirs have a scattered development, dominance of granulated-mylonitized coal, and low permeability, indicating low potential to improve reservoir permeability. Targeted exploitation technology and drainage systems corresponding to the different types of coal reservoirs should be proposed to improve coalbed methane production.

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Selection of working fluid

HEDH Multimedia ◽

10.1615/hedhme.a.000314 ◽

2017 ◽

Author(s):

Donatas Mishkinis

Keyword(s):

Working Fluid ◽

Selection Of

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SISTEM PENDUKUNG KEPUTUSAN PEMILIHAN KEPALA CABANG TERBAIK BANK SUMUT DENGAN MENERAPKAN METODE VIKOR

KOMIK (Konferensi Nasional Teknologi Informasi dan Komputer) ◽

10.30865/komik.v2i1.926 ◽

2018 ◽

Vol 2 (1) ◽

Author(s):

Betrik J Hutapea ◽

Mesran Mesran ◽

Siti Nurhabibah

Keyword(s):

Decision Support ◽

Decision Support System ◽

Support System ◽

Development Bank ◽

Vikor Method ◽

The North ◽

Long Time ◽

North Sumatra ◽

Regional Development Bank ◽

Selection Of

SUMUT Bank is one of the Banks in Indonesia with the name of the company PT. Regional Development Bank of North Sumatra. The North Sumatra Bank has branches in each region in North Sumatra both in the district and in the sub-district, and each of these branches is led by a branch leader or branch head. The head of this branch is responsible for the reversal of the Bank being led. The best and most accomplished branch heads deserve more and more awards. The selection of the best branch heads is selected transparently and structured in the hope that it can be a motivation for all branch heads to be able to further improve the quality and service of the Bank they lead. Making the best branch head selection done manually will take a long time and tends to be less transparent and structured. One solution so that the implementation of the selection can be carried out easily and quickly, it requires a Decision Support System that can provide consistency of assessment. In this study the method used is the VIKOR method (Visekriterijumsko Kompromisno Rangiranje). This method makes cracking on alternatives based on criteria that have been determined with an ideal compromise solution or the best solution, so that this system can later be beneficial for the SUMUT Bank to get the title in determining the best branch head.Keywords: Decision Support System, North Sumatra Bank, Branch Head, Vikor

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Selection of china plum varieties (Prunus salicina lindl.) for use in modern plantings of the northern caucasus foothill zone

POMICULTURE & SMALL FRUITS CULTURE IN RUSSIA ◽

10.31676/2073-4948-2020-61-69-76 ◽

2020 ◽

Vol 61 ◽

pp. 69-76

Author(s):

A. E. Dedova

Keyword(s):

Northern Caucasus ◽

Seasonal Growth ◽

North Caucasus ◽

Biometric Parameters ◽

The North ◽

Prunus Salicina ◽

Breeding Station ◽

New Varieties ◽

Plum Varieties ◽

Selection Of

This paper presents the results of two years of research (2018-2019) of the most important phonological phases of seasonal growth and development, biometric parameters, productivity and economic efficiency of new varieties of Chinese plum (P. salicina Lindl.) grown in the foothill zone of the North Caucasus in the Krymsk district of Krasnodar territory on a plot of the Krymsk experimental breeding station – branch of VIR. As a result of research, the varieties Angeleno, Black Star, Byron Gold, Black Amber, Larry Ann and Sun Gold were recommended for cultivation using intensive technologies.

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A predictable smoothing evolution model for computer-controlled polishing

Journal of the European Optical Society Rapid Publications ◽

10.1186/s41476-020-00145-4 ◽

2020 ◽

Vol 16 (1) ◽

Author(s):

Jing Hou ◽

Pengli Lei ◽

Shiwei Liu ◽

Xianhua Chen ◽

Jian Wang ◽

...

Keyword(s):

Evolution Model ◽

Quantitative Prediction ◽

Theoretical Support ◽

Model Combining ◽

Process Guidance ◽

Dependent Model ◽

Computer Controlled Optical Surfacing ◽

Computer Controlled ◽

Time Dependent Model ◽

Selection Of

AbstractQuantitative prediction of the smoothing of mid-spatial frequency errors (MSFE) is urgently needed to realize process guidance for computer controlled optical surfacing (CCOS) rather than a qualitative analysis of the processing results. Consequently, a predictable time-dependent model combining process parameters and an error decreasing factor (EDF) were presented in this paper. The basic smoothing theory, solution method and modification of this model were expounded separately and verified by experiments. The experimental results show that the theoretical predicted curve agrees well with the actual smoothing effect. The smoothing evolution model provides certain theoretical support and guidance for the quantitative prediction and parameter selection of the smoothing of MSFE.

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A Comprehensive Coal Reservoir Classification Method Base on Permeability Dynamic Change and Its Application

Energies ◽

10.3390/en13030644 ◽

2020 ◽

Vol 13 (3) ◽

pp. 644 ◽

Cited By ~ 2

Author(s):

Xinlu Yan ◽

Songhang Zhang ◽

Shuheng Tang ◽

Zhongcheng Li ◽

Yongxiang Yi ◽

...

Keyword(s):

Coalbed Methane ◽

Dynamic Change ◽

Initial Permeability ◽

Gas Production ◽

Gas Desorption ◽

Reservoir Permeability ◽

Geological Conditions ◽

Production Stages ◽

Productivity Potential ◽

Coal Reservoir

Due to the unique adsorption and desorption characteristics of coal, coal reservoir permeability changes dynamically during coalbed methane (CBM) development. Coal reservoirs can be classified using a permeability dynamic characterization in different production stages. In the single-phase water flow stage, four demarcating pressures are defined based on the damage from the effective stress on reservoir permeability. Coal reservoirs are classified into vulnerable, alleviative, and invulnerable reservoirs. In the gas desorption stage, two demarcating pressures are used to quantitatively characterize the recovery properties of permeability based on the recovery effect of the matrix shrinkage on permeability, namely the rebound pressure (the pressure corresponding to the lowest permeability) and recovery pressure (the pressure when permeability returns to initial permeability). Coal reservoirs are further classified into recoverable and unrecoverable reservoirs. The physical properties and influencing factors of these demarcating pressures are analyzed. Twenty-six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were examined as a case study, showing that there is a significant correspondence between coal reservoir types and CBM well gas production. This study is helpful for identifying geological conditions of coal reservoirs as well as the productivity potential of CBM wells.

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The therapeutic mechanism of epilepsy seizures in different target areas: Research on a theoretical model

Technology and Health Care ◽

10.3233/thc-218043 ◽

2021 ◽

Vol 29 ◽

pp. 455-461

Author(s):

Bing Hu ◽

Zhizhi Wang ◽

Minbo Xu ◽

Luyao Zhu ◽

Dingjiang Wang

Keyword(s):

Pyramidal Neurons ◽

Control Mechanism ◽

Difficult Problem ◽

Calculation Model ◽

Thalamic Reticular Nucleus ◽

Reticular Nucleus ◽

Theoretical Support ◽

Therapeutic Mechanism ◽

Optimal Target ◽

Selection Of

BACKGROUND: The selection of optimal target areas in the surgical treatment of epilepsy is always a difficult problem in medicine. OBJECTIVE: We employed a theoretical calculation model to explore the control mechanism of seizures by an external voltage stimulus acting in different nerve nuclei. METHODS: Theoretical analysis and numerical simulation were combined. RESULTS: The globus pallidus, excitatory pyramidal neurons, striatal D1 neurons, thalamic reticular nucleus and specific relay nuclei were selected, we analyzed that the electrical stimulation has different effects in these target areas. CONCLUSIONS: The data selected were reasonable in study, the results may give a theoretical support for similar studies in clinical.

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