scholarly journals Influence of Extreme Temperature on the Pore and Fracture Development of High-Rank Coal

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Ming Yang ◽  
Jingcang Bi
Keyword(s):  
Temperature Stress ◽  
Pore Volume ◽  
Coal Sample ◽  
High Rank ◽  
Research Attention ◽  
Ultralow Temperature ◽  
Distribution Features ◽  
Fracture Development ◽  
Porosity And Permeability ◽  
Coal Reservoir

Pore and fracture structures in coals and their distribution features play an important role in the enrichment and osmosis migration of coalbed methane (CBM). The modification and antireflection of pore and fracture in coal reservoir through ultrahigh and ultralow temperature stress, such as liquid nitrogen frozen-induced cracking and thermal antireflection of coal reservoir, have attracted wide research attention. This study conducted a nuclear magnetic resonance (NMR) experiment of pore and fracture features of coal samples under two extreme temperatures (100°C, −196°C) using the Meso MR23-060H-I low-field NMR and imaging instrument. The influencing law of ultrahigh and ultralow temperature stress on pore and fracture development in high-rank coal was discussed. Results demonstrated that temperature can influence pore and fracture development of high-rank coal samples. The pore volume, porosity, and permeability of the coal sample increase after low-temperature (−196°C) treatment. The proportion of microspores decreases, the proportion of small pores increases, the proportion of mesopores remains the same, and the proportion of macrospores increases to some extent. The pore volume of coal sample decreases after high-temperature (100°C) treatment. Porosity and permeability decrease. The proportion of mesopores declines, the proportion of mesopores remains basically same, and the proportion of macrospores decreases.

Application of NMR in Coal Reservoir Characterization

2013 ◽  
Vol 765-767 ◽  
pp. 2168-2171 ◽  
Author(s):  
Zi Yang ◽  
Xiao Hua Pan ◽  
Sheng Qiang Yuan ◽  
Zhi Feng Ji
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Reservoir Characterization ◽  
High Rank ◽  
Low Rank ◽  
Main Peak ◽  
Low Rank Coal ◽  
Trimodal Distribution ◽  
Porosity And Permeability ◽  
Coal Reservoir ◽  
Low Rank Coals

Nuclear Magnetic Resonance (NMR) can provide information about pore and fracture structures, porosity and permeability of reservoirs. It can deep into materials without destroying samples, with advantages such as rapid, accurate and high resolution. This paper introduced the experimental principles and carried out a series of NMR experiments based on high rank coal and low rank coal samples. Results show that: the T2 spectra of high rank coal samples have an independent trimodal distribution with the main peak located at the low T2 value section, indicating that high rank coal is dominated by micropores and transition pores; while the T2 spectrum of low rank coal samples show a continuous trimodal distribution with the main peak located at the high T2 value section, demonstrating the dominance of macropores, mesopores and fractures. The pore and fracture structures of low rank coals are significantly favorable than those of high rank coals.

scholarly journals Petrophysical characterization of high-rank coal by nuclear magnetic resonance: a case study of the Baijiao coal reservoir, SW China

2018 ◽  
Vol 5 (12) ◽  
pp. 181411 ◽  
Author(s):  
Dongming Zhang ◽  
Yapei Chu ◽  
Shujian Li ◽  
Yushun Yang ◽  
Xin Bai ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coalbed Methane ◽  
High Rank ◽  
Free Fluid ◽  
Permeability Model ◽  
Cutoff Value ◽  
Coal Reservoir ◽  
Nuclear Magnetic

To better apply nuclear magnetic resonance (NMR) to evaluate the petrophysical characterization of high-rank coal, six anthracite samples from the Baijiao coal reservoir were measured by NMR. The porosity, T 2 cutoff value, permeability and pore type were analysed using the transverse relaxation time ( T 2 ) spectrum before and after centrifugation. The results show that the T 2 spectrum of water-saturated anthracite can be divided into a discontinuous and continuous trimodal distribution. According to the connectivity among pores, three T 2 spectrum peaks were identified at the relaxation times of 0.01–1.7 ms, 1.7–65 ms and greater than 65 ms, which correspond to the micropores (less than 100 nm), mesopores (100–1000 nm) and macropores (greater than 1000 nm), respectively. Based on the T 2 cutoff value, we divided the T 2 spectrum into two parts: bound fluid and free fluid. By comparing two classic permeability models, we proposed a permeability model to calculate the permeability of anthracite. This result demonstrates that NMR has great significance to the exploration of coal reservoirs and to the understanding of the development of coalbed methane.

scholarly journals A Simple Effective Method for Three-Dimensional Modelling of Cementation, Fracturing and Dissolution of Carbonate Rocks: Illustrated through Oolitic Limestone

Geosciences ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 246 ◽  
Author(s):  
James Buckman ◽  
Sean Higgins
Keyword(s):  
Network Architecture ◽  
Local Heat ◽  
Pore Network ◽  
Three Dimensions ◽  
Source Image ◽  
Particle Deformation ◽  
Simple Method ◽  
Oolitic Limestone ◽  
Fracture Development ◽  
Porosity And Permeability

Sandstones and many carbonates (e.g., oolitic limestone and other grainstones), comprise solid particulates (grains) and pores, which have a given pore network architecture relationship, and associated porosity—permeability values. Over time, through the process of diagenesis, the pore network architecture may be extensively altered. Changes can include compaction, particle deformation, cementation, dissolution and fracturing, with the pathway followed after deposition depending on factors such as the energy level, rate of burial, degree of biological activity, local heat flow, sediment composition, Eh, pH and the presence or absence of organic materials. Any method that provides a means of modelling changes is therefore highly desirable, in particular, allowing a prediction of changes in porosity and permeability with time. The current work illustrates a simple method that uses freely available open source image analysis software to model the development of cement phases within an oolitic limestone in three-dimensions. As well as cementation, it demonstrates the modelling of fracture development and dissolution processes, and records how porosity and permeability change during such processes.

Self-adjusted elastic action and its CBM pool-forming effect of the high rank coal reservoir

2005 ◽  
Vol 50 (S1) ◽  
pp. 99-103 ◽  
Author(s):  
Yong Qin ◽  
Xuehai Fu ◽  
Caifang Wu ◽  
Guoyou Fu ◽  
Yingying Bu
Keyword(s):  
High Rank ◽  
Coal Reservoir

scholarly journals The Application of Simple Controlled Pressure Drilling Technology in Yingxi Block

2018 ◽  
Vol 53 ◽  
pp. 03003
Author(s):  
ZHANG Guohui ◽  
Hugui ◽  
CHEN rong ◽  
LIU Xinyun ◽  
ZHANG Xiwen
Keyword(s):  
Oil And Gas ◽  
Gas Reservoir ◽  
Protection Effect ◽  
Fracture Development ◽  
Wellbore Pressure ◽  
Drilling Technology ◽  
Porosity And Permeability ◽  
Reservoir Protection ◽  
Oil And Gas Reservoir ◽  
Medium Type

Under the reservoir for exploration and development of Yingxi block in Qinghai oilfield, the chaigou formation is oil and gas reservoir complicated by the fault, and the exploration has been carried out over the years. The reservoir is a fracture - matrix pore dual medium type, with strong heterogeneity, fracture development degree, porosity and permeability variation range. The reservoir is very sensitive to wellbore pressure, the safety drilling density window is narrow, the conventional drilling leakage is frequent, the reservoir protection effect is poor, and the mechanical drilling rate is low. In 2016 six wells were selected for easy control and pressure drilling in the lower E23 formation. The technology experiment has obtained good application effect, which provides successful experience to solve the complex and improve the engineering quality and benefit.

Control Mechanism of the Effective Stress on Nano-Micro Pores and the Permeability of High-Rank Coals

2021 ◽  
Vol 21 (1) ◽  
pp. 484-494
Author(s):  
Xiaofeng Ji ◽  
Dangyu Song ◽  
Shaokai Yu ◽  
Kaikai He ◽  
Yunbo Li
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Gas Adsorption ◽  
Initial Permeability ◽  
High Rank ◽  
Control Factors ◽  
Reservoir Permeability ◽  
Variation Mechanism ◽  
Coal Reservoir ◽  
The Impact

To study the change and main control factors of the high-rank coal reservoir permeability in deep coal seams, permeability tests under different stresses and gas pressures were carried out in the laboratory. The development and distribution of nano-micro pores and fractures in the coal matrix were analyzed and observed by mercury intrusion porosimetry, gas adsorption, scanning electron microscope and computed tomography to reveal the permeability variation mechanism. The results showed that the initial permeability of the coal samples ranged from 0.0114 mD to 0.2349 mD when the effective stress was 0 MPa, and it clearly varied among different samples. The permeability of all the coal samples was very sensitive to the effective stress and decreased exponentially with the increase of the effective stress. The increase of the pore pressure also led to a decrease of the permeability, whereas the impact of the pore pressure on permeability was less obvious compared with the effective stress. Sub-nanopores, nanopores, micro-fractures and larger fractures are all developed in the coal samples. Connected larger fractures were the main gas migration channels in permeability determination, and the narrowing, disconnection, and closure of the fractures caused by the increase of the effective stress were the most important reasons for significant reduction of permeability.

Relationship between porosity and permeability with stress using pore volume compressibility characteristic of reservoir rocks

2012 ◽  
Vol 7 (1) ◽  
pp. 231-239 ◽  
Author(s):  
S. A. Moosavi ◽  
K. Goshtasbi ◽  
E. Kazemzadeh ◽  
H. Aloki Bakhtiari ◽  
M. R. Esfahani ◽  
...  
Keyword(s):  
Pore Volume ◽  
Reservoir Rocks ◽  
Volume Compressibility ◽  
Pore Volume Compressibility ◽  
Porosity And Permeability

scholarly journals Pore size distributions and pore multifractal characteristics of medium and low-rank coals

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Bin Sun ◽  
Qing Yang ◽  
Jie Zhu ◽  
Tangsha Shao ◽  
Yuhang Yang ◽  
...  
Keyword(s):  
Pore Size ◽  
Pore Volume ◽  
Nitrogen Adsorption ◽  
Low Rank ◽  
Size Distributions ◽  
Confining Stress ◽  
Mercury Intrusion ◽  
Pore Size Distributions ◽  
Porosity And Permeability ◽  
Low Rank Coals

AbstractIt is of great significance to study the porosity and permeability properties of medium and low-rank coal. The porosity and permeability in confining stress experiments were used to simulate the porosity and permeability variations of coal samples under different depth conditions. The pore structure of Baoqing coal samples is greatly affected by the confining pressure, and the pores and micro cracks are more easily compressed. Based on the experimental data of mercury intrusion porosimetry (MIP) and nitrogen adsorption (NA), the pore size distributions (PSDs) of medium and low-rank coals were studied. High mercury intrusion pressure would lead to coal matrix compression. Therefore, the pore volume calculated by MIP data was corrected by NA data. The PSDs characteristics of Jixi (JX) coal and Baoqing (BQ) coal samples are obtained from the revised pore volume, and the dominant pores of medium and low-rank coals are obtained. The results show that JX coal has higher spatial heterogeneity, connectivity and pore autocorrelation. Micro fractures have an influence on the autocorrelation and heterogeneity of coal samples, especially for BQ coal samples.

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