Fluid Performance in Coal Reservoirs: A Comprehensive Review

The fluids in coal reservoirs mainly consist of different gases and liquids, which show different physical properties, occurrence behaviors, and transport characteristics in the pore-fracture system of coal. In this study, the basic characteristics of fluids in coal reservoirs are firstly reviewed, consisting of coalbed methane (CBM) components and physical properties of CBM/coalbed water. The complex pore-fracture system mainly provides the enrichment space and flow path for fluids, which have been qualitatively and quantitatively characterized by various methods in recent years. Subsequently, this study has summarized CBM adsorption/desorption behaviors and models, the CBM diffusion-seepage process and models, and gas-water two-phase flow characteristics of coal reservoirs. Reviewed studies also include the effects of internal factors (such as coal metamorphism, petrographic constituents, macroscopic types, and pore structure) and external factors (such as pressure, temperature, and moisture content) on CBM adsorption/desorption and diffusion behaviors, and the relationship between three main effects (effective stress, gas slippage effect, and coal matrix shrinkage effect) and the CBM seepage process. Moreover, we also discuss in depth the implication of fluid occurrence and transport characteristics in coal reservoirs for CBM production. This review is aimed at proposing some potential research directions in future studies, which mainly includes the control mechanism of the microscopic dynamics of fluids on CBM enrichment/storage; enhancing CBM desorption/seepage rate; and the synergistic effect of multiple spaces, multilevel flow fields, and multiphase flow in coal reservoirs. From this review, we have a deeper understanding of the occurrence and transport characteristics of fluids in pore-fracture structures of coal and the implication of fluid performance for CBM production. The findings of this study can help towards a better understanding of gas-water production principles in coal reservoirs and enhancing CBM recovery.

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A Discrete Fracture Modeling Approach for Analysis of Coalbed Methane and Water Flow in a Fractured Coal Reservoir

Geofluids ◽

10.1155/2020/8845348 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Tianran Ma ◽

Hao Xu ◽

Chaobin Guo ◽

Xuehai Fu ◽

Weiqun Liu ◽

...

Keyword(s):

Water Flow ◽

Coalbed Methane ◽

Fluid Transport ◽

Fracture Model ◽

Phase Flow ◽

Two Phase ◽

Discrete Fracture Model ◽

Discrete Fracture ◽

Fractured Coal ◽

Cbm Production

As a complex two-phase flow in naturally fractured coal formations, the prediction and analysis of CBM production remain challenging. This study presents a discrete fracture approach to modeling coalbed methane (CBM) and water flow in fractured coal reservoirs, particularly the influence of fracture orientation, fracture density, gravity, and fracture skeleton on fluid transport. The discrete fracture model is first verified by two water-flooding cases with multi- and single-fracture configurations. The verified model is then used to simulate CBM production from a discrete fractured reservoir using four different fracture patterns. The results indicate that fluid behavior is significantly affected by orientation, density, and fracture connectivity. Finally, several cases are performed to investigate the influence of gravity and fracture skeleton. The simulation results show that gas migrates upwards to the top reservoir during fluid extraction owing to buoyancy and the connected fracture skeleton plays a dominant role in fluid transport and methane production efficiency. Overall, the developed discrete fracture model provides a powerful tool to study two-phase flow in fractured coal reservoirs.

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Preliminary Evaluation on Physical Properties of Coal Reservoirs in Boli Basin, Northeastern Heilongjiang Province, China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.356-360.2963 ◽

2011 ◽

Vol 356-360 ◽

pp. 2963-2969

Author(s):

Yu Ji Zhao ◽

Jun Qian Li ◽

Yi Dong Cai ◽

Da Meng Liu ◽

Yan Bin Yao

Keyword(s):

Physical Properties ◽

Coalbed Methane ◽

Vitrinite Reflectance ◽

Mercury Porosimetry ◽

Preliminary Evaluation ◽

Coal Quality ◽

Isotherm Adsorption ◽

Porosity And Permeability ◽

Adsorption Desorption ◽

Coal Petrography

The Boli basin has coalbed methane (CBM) resource of 57×108m3 at a coal-bearing area of about 7200km2. Although the basin has huge CBM development potential, the study on the characteristics of coal reservoirs is still deficient. In the paper, the physical properties (including coal petrography, rank, quality, porosity and permeability) of the coals were studied by: (1) measuring vitrinite reflectance, coal maceral composition and coal quality; (2) quantitatively counting microfractures; (3) porosity and permeability tests; and (4) low-temperature N2 isotherm adsorption/desorption and mercury porosimetry analyses. Results show that: (1) coal maceral composition is dominated by vitrinite (77.0-95.1 %); (2) the maximum vitrinite reflectance of coals ranges from 0.48 to 1.76 % Ro, max; (3) coal is composed of high carbon content (63.43-85.14%), low hydrogen content (3.23-4.56%), extremely low moisture content (0.18-1.18%) and widely varied ash yield (7.54 to 29.23%); (4) Coal pores are dominated by micropores (40.6-69.3%), and the pores with a diameter of 0-10nm are dominant (59.6-80.9%); (5) coal permeability values vary from 0.04 to 3.92mD with an average of 1.98mD. In addition, according to the mercury porosimetry analysis, pore-fractures size distribution was summarized as four types: Types Ⅰ and Ⅲ are favorable for developing CBM and represent good pore-fracture structures.

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Productivity Prediction of Coalbed Methane Considering the Permeability Changes in Coal

10.2118/spe-169922-ms ◽

2014 ◽

Author(s):

H.. Chen ◽

M.. Li ◽

Y.. Zhang ◽

C.. Liu ◽

Y.. Li

Keyword(s):

Numerical Model ◽

Coalbed Methane ◽

Field Data ◽

Gas Production ◽

Phase Flow ◽

Two Phase ◽

Gas Desorption ◽

Permeability Changes ◽

Cbm Production ◽

Production Period

Abstract This paper describes a three-dimensional numerical model for predicting the coalbed methane (CBM) production. The model describes single phase gas desorption from coal matrix, diffusion to the fracture and two-phase flow of gas and water in the natural fracture system as well as the permeability changes in coal which result from effective stress changes and matrix shrinkage due to gas desorption. The model was discretized by a finite difference method. The implicit pressure-explicit saturation (IMPES) method was used to solve the two-phase flow equations and gas desorption equation was solved implicitly. The numerical model was validated by the field data from Qinshui basin in China. Based on the model, the impact of various reservoir and Langmuir isothermal adsorption parameters on the gas production was investigated. The results show that the gas production rate of the coalbed methane predicted by this model is in good accordance with the field data. The permeability near the wellbore dramatically decreases as the reservoir pressure drops at the early production period while at the later production period, the permeability near the wellbore increases because of the matrix shrinkage. The permeability changes far away from the wellbore are not so remarkable. In addition, the gas production rate increases with the increased permeability, seam thickness and Langmuir pressure constant while it decreases with the increased porosity and Langmuir volume constant. The numerical model can be used to predict and analyze the production performance of CBM reservoirs and the research results provide theoretical support for CBM production.

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INVESTIGATION OF STRATIFIED WAVY TWO-PHASE FLOW CHARACTERISTICS

Equipment ◽

10.1615/ihtc13.p12.130 ◽

2006 ◽

Author(s):

Marijus Seporaitis ◽

S. Gasiunas ◽

Raimondas Pabarcius

Keyword(s):

Two Phase Flow ◽

Flow Characteristics ◽

Phase Flow ◽

Two Phase

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METGLAS MBF-30/30A

Alloy Digest ◽

10.31399/asm.ad.ni0273 ◽

1981 ◽

Vol 30 (12) ◽

Keyword(s):

Stainless Steel ◽

Metallic Glass ◽

Physical Properties ◽

Flow Characteristics ◽

High Strength ◽

Thin Foil ◽

Heat Treating

Abstract METGLAS MBF-30A is a brazing foil in ductile, flexible metallic-glass form (a similar grade, MBF-30, is identical except that it has larger dimensional tolerances). This foil provides an alloy with high strength at both elevated and room temperatures. It can be used to join highly stressed stainless steel and heat-resisting alloy components. The excellent flow characteristics of this alloy recommend it for assemblies with good fit-up and tight-tolerance joints. It works well on thin-foil, honeycomb designs and on fairly heavy components. This datasheet provides information on composition, physical properties, and microstructure. It also includes information on heat treating. Filing Code: Ni-273. Producer or source: Allied Corporation.

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UNILOY 326

Alloy Digest ◽

10.31399/asm.ad.ss0241 ◽

1970 ◽

Vol 19 (7) ◽

Keyword(s):

Stainless Steel ◽

Corrosion Resistance ◽

Physical Properties ◽

Stress Corrosion ◽

Tensile Properties ◽

High Strength ◽

Heat Treating ◽

Distinct Advantage ◽

Two Phase ◽

Stress Corrosion Resistance

Abstract UNILOY 326 is a two-phase, ferromagnetic stainless steel characterized by high strength and very good general and stress corrosion resistance. It has distinct advantage for the fastener industry. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-241. Producer or source: Cyclops.

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