Detecting and Measuring Gas Seepage

Deep coalbed methane (CBM) is widely distributed in China and is mainly commercially exploited in the Qinshui basin. The in situ stress and moisture content are key factors affecting the permeability of CH4-containing coal samples. Therefore, considering the coupled effects of compressing and infiltrating on the gas permeability of coal could be more accurate to reveal the CH4 gas seepage characteristics in CBM reservoirs. In this study, coal samples sourced from Tunlan coalmine were employed to conduct the triaxial loading and gas seepage tests. Several findings were concluded: (1) In this triaxial test, the effect of confining stress on the permeability of gas-containing coal samples is greater than that of axial stress. (2) The permeability versus gas pressure curve of coal presents a ‘V’ shape evolution trend, in which the minimum gas permeability was obtained at a gas pressure of 1.1MPa. (3) The gas permeability of coal samples decreased exponentially with increasing moisture content. Specifically, as the moisture content increasing from 0.18% to 3.15%, the gas permeability decreased by about 70%. These results are expected to provide a foundation for the efficient exploitation of CBM in Qinshui basin.

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Gas seepage laws based on dual porosity and dual permeability: Numerical simulation and coalbed methane extraction practice

Energy Science & Engineering ◽

10.1002/ese3.871 ◽

2021 ◽

Author(s):

Chao Xu ◽

Liangliang Qin ◽

Kai Wang ◽

Haoshi Sun ◽

Mingyue Cao

Keyword(s):

Numerical Simulation ◽

Coalbed Methane ◽

Dual Porosity ◽

Methane Extraction ◽

Gas Seepage

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Coupling Law of Mixed Gas Seepage Field and Concentration Field in Goaf

10.1063/1.3651972 ◽

2011 ◽

Author(s):

Q. Che ◽

X. Q. Zhou ◽

H. Y. Wang ◽

Jiachun Li ◽

Song Fu

Keyword(s):

Concentration Field ◽

Mixed Gas ◽

Seepage Field ◽

Gas Seepage

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Thermos-Solid-Gas Coupling Dynamic Model and Numerical Simulation of Coal Containing Gas

Geofluids ◽

10.1155/2020/8837425 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9

Author(s):

Xiao Fukun ◽

Meng Xin ◽

Li Lianchong ◽

Liu Jianfeng ◽

Liu Gang ◽

...

Keyword(s):

Principal Stress ◽

Dynamic Model ◽

Gas Flow ◽

Flow Behavior ◽

Coupling Model ◽

Gas Pressure ◽

Permeability Model ◽

Gas Seepage ◽

Coupling Dynamic ◽

Coupling Dynamic Model

Based on gas seepage characteristics and the basic thermo-solid-gas coupling theory, the porosity model and the dynamic permeability model of coal body containing gas were derived. Based on the relationship between gas pressure, principal stress and temperature, and gas seepage, the thermo-solid-gas coupling dynamic model was established. Initial values and boundary conditions for the model were determined. Numerical simulations using this model were done to predict the gas flow behavior of a gassy coal sample. By using the thermo-solid-gas coupling model, the gas pressure, temperature, and principal stress influence, the change law of the pressure field, displacement field, stress field, temperature field, and permeability were numerically simulated. Research results show the following: (1) Gas pressure and displacement from the top to the end of the model gradually reduce, and stress from the top to the end gradually increases. The average permeability of the Y Z section of the model tends to decrease with the rise of the gas pressure, and the decrease amplitude slows down from the top of the model to the bottom. (2) When the principal stress and temperature are constant, the permeability decreases first and then flattens with the gas pressure. The permeability increases with the decrease of temperature while the gas pressure and principal stress remain unchanged.

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Computational fluid dynamics optimization of gas drainage technology in gas-mining areas

Energy Exploration & Exploitation ◽

10.1177/01445987211063586 ◽

2021 ◽

pp. 014459872110635

Author(s):

Wei Zhao ◽

Wei Qin

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Coal Seam ◽

Field Tests ◽

Mining Area ◽

Engineering Practice ◽

Horizontal Distance ◽

Gas Drainage ◽

Working Face ◽

Gas Seepage

Coal mining results in strata movement and surrounding rock failure. Eventually, manual mining space will be occupied by the destructed coal rock, making it difficult to conduct field tests of the coal seam to explore gas seepage and transport patterns. Therefore, computational fluid dynamics (CFD) numerical computation is an important tool for such studies. From the aspect of gas pre-drainage, for layer-through boreholes in the floor roadway of the 8,406 working face in Yangquan Mine 5 in China, reasonable layout parameters were obtained by CFD optimization. For effectively controlling the scope of boreholes along coal seam 9 in the Kaiyuan Mine, CFD computation was performed. The results revealed that the horizontal spacing between boreholes should be ≤2 m when a tri-quincuncial borehole layout is used. Optimization of the surface well position layout for the fault structure zone in the Xinjing Mine of the Yangquan mining area indicated that the horizontal distance between the surface well and the fault plane should be <150 m. From the aspect of gas drainage with mining-induced pressure relief, CFD computation was performed for pressure-relieved gas transport in the K8205 working face of Yangquan Mine 3. The results showed that forced roof caving should be used before the overhang length of hard roof reaches 25 m in the K8205 working face to avoid gas overrun. From the aspect of gas drainage from the abandoned gob, surface well control scopes at different surface well positions were computed, and an O-ring fissure zone is proposed as a reasonable scope for the surface well layout. CFD computation has been widely applied to coal and gas co-extraction in the Yangquan mining area and has played a significant role in guiding related gas drainage engineering practice.

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Complex Subsurface Well Abandonments Using Relief Well Methodologies

10.2118/206311-ms ◽

2021 ◽

Author(s):

Jamie Dorey ◽

Georgy Rassadkin ◽

Douglas Ridgway

Keyword(s):

Case Studies ◽

Best Practice ◽

Oil And Gas ◽

Oil And Gas Industry ◽

Gas Industry ◽

Gas Seepage ◽

Cost Efficient ◽

Well Abandonment ◽

Efficient Option ◽

Practice Methods

Abstract The field experience in the continental US suggests that approximately 33% of plug and abandonment operations are non-routine, and 5% require re-entry (Greer C.R., 2018). In some scenarios, the most cost-efficient option for the intervention is drilling an intercept well to re-enter the target well or multiple wells externally using advanced survey management and magnetic ranging techniques. This paper presents the methods applied of relief well methodologies from the planning to execution of a complex multiple-well abandonment project. Improvements in Active Magnetic Ranging sensor design and applications have improved the availability of highly precise tools for the purpose of locating and intercepting wellbores where access is not possible. These instruments were commonplace on relief well interventions, however, have found a new application in solving one of the major issues facing the oil and gas industry. Subsurface abandonments are a complex task that requires a robust methodology. In this paper, we describe the techniques that have been built upon the best practices from industry experience (ISCWSA WISC eBook). This paper also illustrates how the combination of advanced survey management, gyro surveying, and magnetic ranging can be used following the best industry practices for fast and cost-efficient non-routine plug and abandonment. Case studies of several abandonment projects are presented showing the various technical challenges which are common on idle and legacy wells. The projects include wells that are currently under the ownership of an operator and orphaned wells that have been insufficiently abandoned and left idle over many decades. The case studies outline how the application of relief well methodologies to the execution of complex sub surface interventions led to the successful outcomes of meeting environmental and government regulations for wellbore abandonment. This includes performing multiple zonal isolations between reservoirs, water zones and preventing oil and gas seepage to the surface. The projects and their outcomes prove economically viable strategies for tackling the growing issue of idle and orphaned wells globally in a fiscally responsible manner. Combining industry best practice methods for relief well drilling, along with the technological advancements in magnetic ranging systems is a solution for one of the largest dilemmas facing the oil and gas industry in relation to idle and orphaned wellbores. These applications allow previously considered impossible abandonments to be completed with a high probability of long-term success in permanent abandonment.

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