Numerical Simulation of Gas Injection for CBM Openhole Cavity Completion Considering the Coal Vertical Fracture System

2011 ◽  
Vol 101-102 ◽  
pp. 298-301
Author(s):  
Xiao Yi Li ◽  
Zhi Ming Wang ◽  
Xin Wan ◽  
Yang Cao
Keyword(s):  
Coalbed Methane ◽  
Displacement Vector ◽  
Fluid Velocity ◽  
Stress Gradient ◽  
Fracture System ◽  
Vertical Fracture ◽  
Matrix Deformation ◽  
Vector Distribution ◽  
Tensile Fractures ◽  
Coal Reservoir

A discrete element numerical model simulating the process of gas pressurization in coalbed methane wells is built based on UDEC software. The model considers the unique vertical fracture system of the coal. Simulates the distribution of effective stress, pore pressure and the node displacement vector around the wellbore in the process of pressurization under different terrestrial stress conditions. The analysis shows that, reservoir fluid flow and matrix deformation in the pressurization of cavity completion can be better represented by taking coal's unique fracture system into consideration. Coal reservoir with anisotropic stress is more prone to rupture and collapse than that under isotropic condition. In the vertical fracture system, the discrepancy of the fluid velocity will lead to differences in formation stress gradient and help generate shearing fracture. Tensile fractures’ formation and growing trend can be reflected by nodal displacement vector distribution.

The Development of Coal Reservoir Fracture and its Geological Controls in Zhengzhuang Block, Southern Qinshui Basin, China

2014 ◽  
Vol 962-965 ◽  
pp. 147-151 ◽  
Author(s):  
Lu Cai ◽  
Song Bin Xie ◽  
Qiu Xia Huang
Keyword(s):  
Coalbed Methane ◽  
Large Scale ◽  
System Development ◽  
Fracture System ◽  
Key Factors ◽  
Factors Influencing ◽  
Reservoir Permeability ◽  
Coal Rock ◽  
Southern Qinshui Basin ◽  
Coal Reservoir

Coal reservoir system is the key factors influencing the permeability of coal seam, the study of the development extent of the fracture is very beneficial for the large-scale commercial exploitation of coalbed methane. From the metamorphic degree of coal rock, maceral, coal characteristics and mineral filling these aspects ,this article discusses the control mechanism of the fracture system development. It is pointed out that the development degree of system is the direct factors influencing the coal reservoir permeability and fracture system development is influenced by many factors. The fillings in crack can block the fracture and reduce the permeability of coal reservoirs.

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

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 644 ◽  
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.

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 Quantitative optimization of drainage strategy of coalbed methane well based on the dynamic behavior of coal reservoir permeability

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xinlu Yan ◽  
Songhang Zhang ◽  
Shuheng Tang ◽  
Zhongcheng Li ◽  
Qian Zhang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Dynamic Behavior ◽  
Water Flow ◽  
Coalbed Methane ◽  
Single Phase ◽  
Reservoir Permeability ◽  
Geological Conditions ◽  
Cbm Production ◽  
Coal Reservoir ◽  
Flow Stage

AbstractThe development of coalbed methane (CBM) is not only affected by geological factors, but also by engineering factors, such as artificial fracturing and drainage strategies. In order to optimize drainage strategies for wells in unique geological conditions, the characteristics of different stages of CBM production are accurately described based on the dynamic behavior of the pressure drop funnel and coal reservoir permeability. Effective depressurization is achieved by extending the pressure propagation radius and gas desorption radius to the well-controlled boundary, in the single-phase water flow stage and the gas–water flow stage, respectively, with inter-well pressure interference accomplished in the single-phase gas flow stage. A mathematic model was developed to quantitatively optimize drainage strategies for each stage, with the maximum bottom hole flow pressure (BHFP) drop rate and the maximum daily gas production calculated to guide the optimization of CBM production. Finally, six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were used as a case study to verify the practical applicability of the model. Calculation results clearly indicate the differences in production characteristics as a result of different drainage strategies. Overall, if the applied drainage strategies do not achieve optimal drainage results, the coal reservoir could be irreversibly damaged, which is not conducive to expansion of the pressure drop funnel. Therefore, this optimization model provides valuable guidance for rational CBM drainage strategy development and efficient CBM production.

Microstructure of Mid and High Rank Coals from Qinshui Basin, North China and its Contribution to Coalbed Meathane

2012 ◽  
Vol 616-618 ◽  
pp. 201-207
Author(s):  
Zhi Hua Liu ◽  
Jun Gang Liu ◽  
Yi Guo Dong ◽  
Yang Chen ◽  
Li Ren Xing ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Vitrinite Reflectance ◽  
Mercury Porosimetry ◽  
Nitrogen Adsorption ◽  
Isothermal Adsorption ◽  
Qinshui Basin ◽  
Coal Macerals ◽  
Coal Reservoir ◽  
Micro Structures ◽  
Adsorption Capability

To better understand the relationship between micro-structures and coalbed methane(CBM), characterisation methods including microscopic photometer, scanning electron microscopy (SEM), mercury porosimetry, nitrogen adsorption at 77K and methane isothermal adsorption were introduced into investigating the adsorption capability of coal reservoir. The results reveal that the micropores volume has a increasing trend with increased vitrinite reflectance. The most favorable pore type is to have good connectivity, very good micro-pores porosity and good adsorption capability. Statistical analysis shows that endo-microfractures are the main type microfractures of Qinshui basin. Based on the results of coal macerals, coal lithotypes, it is found that the bright coal and telocollinites are favorable for endo-fractures formation. Obviously different from the formation of endo-microfracture, exo-microfracture strongly relates to the coal structure. A good match between the fractures and the pores is needed for a favorable CBM reservoir. Based on the evaluation of pore-fracture system, Yangquan is the second CBM commercial area of Qinshui basin.

Influence of Engineering Measurements on the Desorption and Production of CBM Wells by Eclipse

2013 ◽  
Vol 868 ◽  
pp. 700-704 ◽  
Author(s):  
Rui Wang ◽  
Fan Dong ◽  
Qing Zhong Zhu ◽  
Yan Hui Yang ◽  
Tian Peng Yao
Keyword(s):  
Coalbed Methane ◽  
Production Capacity ◽  
Gas Production ◽  
Simulation Software ◽  
Stage Of Development ◽  
Cbm Production ◽  
Stable Yield ◽  
Yield Time ◽  
Coal Reservoir ◽  
The Impact

Desorption of Coalbed Methane is one of the key controls to CBM recovery ratio and production capacity. This paper discusses the impact of engineered measures on CBM overall desorption and production capacity with CBM model of Eclipse numerical simulation software. The simulation results show that: with the extension of hydraulic fracture half-length, overall desorption of coal reservoir increased and CBM production capacity improved, daily gas production, maximum gas production and stable yield time increased correspondingly; in different deployment of spacing and well network, the smaller spacing is beneficial to the overall desorption of coal reservoir, but its production can not keep stability because of the serious decline in the late stage of development, while the larger spacing shows in the opposite way.

Mineral Characteristics of Low-Rank Coal and the Effects on the Micro- and Nanoscale Pore-Fractures: A Case Study from the Zhundong Coalfield, Northwest China

2021 ◽  
Vol 21 (1) ◽  
pp. 460-471 ◽  
Author(s):  
Sandong Zhou ◽  
Dameng Liu ◽  
Yidong Cai ◽  
Yingjin Wang ◽  
Detian Yan
Keyword(s):  
Adsorption Capacity ◽  
Coalbed Methane ◽  
Mineral Content ◽  
Northwest China ◽  
Low Rank ◽  
Low Rank Coal ◽  
Mineral Characteristics ◽  
Type D ◽  
Coal Reservoir ◽  
Nuclear Magnetic

The mineral characteristics (occurrence, type, and content) of low-rank coal and their influence on coalbed methane (CBM) reservoirs are investigated at the micro- and nanoscales. Six coal samples of three representative coalmines were used to demonstrate the uniform tectonization from the Zhundong coalfield, NW China. Based on optical microscopy and scanning electron microscopyenergy dispersive spectrum (SEM-EDS) analysis, the mineral composition and occurrence characteristics were discussed. The micro- and nanoscale reservoir characteristics in low-rank coal (pore size distribution and adsorption capability) were studied by diverse methods, including lowtemperature N2 adsorption/desorption, mercury intrusion porosimetry and CH4 isotherm adsorption analysis. The coal reservoir nuclear magnetic T2 spectra of porosity and movable fluid were obtained by combining low-field nuclear magnetic resonance (NMR) analysis, which has an advantage of determining pore fluid technology. The mineral content is highly variable (4˜16 vol.%) in the Xi Heishan prospecting area of the Qitai region. Kaolinite, goyazite, ankerite and anorthosite were microscopically observed to be filling in coal pores and microfractures, and the minerals are given priority to silicate minerals. There is a greater content of mesopores (100–1000 nm) and transition pores (10–100 nm), and they are well connected. The micropores (0–10 nm) are dominated by parallel plate, closed or wedge-shaped pores. Furthermore, the microfractures are mainly observed for types B (width ≥ 5 μm and length≤ 10 mm) and D (width<5 μm and length<300 μm). The results show that microfractures B and C (width< 5 μm and length ≥ 300 μm) are better connected, but the orientation and connectivity of type D are worse. The Langmuir volume and mesopore content decreased with increasing mineral content, which shows that the low-rank coal minerals filled some adsorption space; the reduced CBM adsorption capacity and cellular pore and intergranular pore filled with minerals affect the mesopore content. Therefore, mineral characterization significantly influences methane adsorption capacity and pore structure.

Structure Design of Coal Particle Washing Jet Pump Used in Coalbed Methane Wells and Basic Parameters Determination

2013 ◽  
Vol 365-366 ◽  
pp. 82-85
Author(s):  
Bing Liu ◽  
Yao Guang Qi ◽  
Shang Zhi Meng ◽  
Ri He Mo ◽  
Ji Yun Du ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Coal Particle ◽  
Structure Design ◽  
Coal Bed ◽  
Jet Pump ◽  
Method Of Calculation ◽  
Basic Parameters ◽  
Working Principle ◽  
Coal Reservoir ◽  
Working Efficiency

In view of the characteristic that the bottom pressure of Coalbed Methane Wells (CBM wells) is low and the structure of coal bed could be easily destructed, the author designed a kind of jet pump. The jet pump could improve efficiency of washing bottom-hole coal particle in condition of protecting the structure of coal reservoir. In this paper, we have analyzed the structure of jet pump and working principle; and given the method of calculation the basic parameters of jet pump on the basis of calculating the working efficiency of jet pump from the point of cavitation.

Sign in / Sign up

Export Citation Format

Share Document