Geological Tectonics Research Articles

Structural Background of Geda Area in Tibet and Its Influence on Exercise and Training Activities

Tectonic geology is one of the most critical factors affecting geological activities in the regional geological background. By studying the structural geological environment of Geda Township and analyzing its geological units and tectonic stresses, it is concluded that: (1) Six large faults developed in the area in the near-north-south direction control the basic geological and tectonic structure of the working area and affect the spatial structure of the area; The depression of the fault is the Geda fault depression basin, and the flat valley area of the basin is relatively flat, which is conducive to the assembly and cantonment of troops. (2) The extension scale of the fault system extends a large scale, the direction of nearly north-south, in the engineering layout or field mobility, and the fault zone should be avoided as much as possible in engineering layout or field maneuvering; (3) There are many valleys, gullies and other connected landforms in the area, which are conducive to the passage of troops and logistics supplies; (4) The tectonic pattern of Geda sedimentary basin formed by the near-north-south oriented Geda sedimentary basin basin-control rupture system provides a good channel for field maneuvering; (5) The north-south fault system leads to the development of cracks and good penetration in the area, and the groundwater penetrates the surface well due to various effects such as pressure or siphon, and the entire water supply system in the area is guaranteed. Based on the combination of structural geology and military geology, this study preliminarily reviews the relationship between the two, and provides ideas for the integration of the two professional disciplines.

Mesozoic: A new interdisciplinary journal for Mesozoic Earth and life evolution

Mesozoic is an interdisciplinary journal dedicated to the study of Earth and life evolution during the Mesozoic Era. Its scope within the geosciences is broad, encompassing disciplines such as stratigraphy, palaeontology, palaeogeography, palaeoclimate, palaeoenvironment, geochronology, sedimentology, geochemistry, palaeomagnetism, and tectonic geology. We encourage interdisciplinary collaboration to explore the deep relationships between biotic evolution and Earth’s surface processes.

Edge enhancement of potential field data using the enhanced gradient (EG) filter

Potential field data play a critical role in interpreting various geologic structural features through edge detection filters that aid in mapping subsurface structural features. For this purpose, various filters have been introduced in recent years to determine lateral boundaries. However, each of these filters has its limitations and advantages. This study presents a new edge enhancement filter named “Enhanced Gradient (EG)” based on the Richards function and applies it to potential field data for structural mapping. The EG is tested on two dimensional (2D) and three dimensional (3D) synthetic magnetic models with sources buried at different depths and variable properties. The results from the EG filter provide more accurate and higher resolution horizontal boundaries and can avoid creating the false edges in the output results. In addition, the proposed filter was examined using aeromagnetic data from the Indiana region in the USA. The primary and secondary faults and geological formations are recognizable in the EG image. The results of the EG map will allow us to improve the qualitative interpretation of potential field anomalies in studying the structural and tectonic geology of the Indiana region in the USA.

Impact of tectonic deformation on shale pore structure using adsorption experiments and 3D digital core observation: A case study of the Niutitang Formation in Northern Guizhou

Tectonic deformation has an evident impact on the pore structure of organic-rich marine shale. To study the impact of tectonic deformation on the pore structure of shale, cores were taken from different tectonic regions in the Niutitang Formation. The paleotectonic stress, pore structures, mineral composition, and geochemical parameters of the shale were determined by conducting the following tests: paleotectonic stress test, core thin-section observation, focus ion beam-scanning electron microscopy (FIB-SEM) observation, vitrinite reflectivity test, low-temperature nitrogen adsorption test, total organic carbon (TOC) test, X-ray diffraction (XRD) test, and nano-CT. The results showed that the shale in the deformed region mainly developed meso-macropores, and the pores were mainly slit-type and conical. The shale in the transition and stability regions primarily developed mesopores and micropores, which were primarily elliptical, slit-type, and columnar. The pore volumes of the shale in the deformed region were 9.54 cm3/kg and 13.9 cm3/kg higher than those in the transition and stability regions, respectively. The shale in the stability and transition regions had average microporous volumes 8.67% and 7.93% higher than that in the deformed region, respectively. The shale reservoir in the stability region developed more micropores and had a higher specific surface area and microporous volume. Furthermore, the organic matter had a greater impact on the micropores than on the meso-macropores. Thermal maturity had a greater impact on the microporous volume than on the macroporous volume. The shale pore connectivity of Well TX 1 was 86.48% and that of Well FC 1 was 22.33%. The pore connectivity of the shale in the stability region was higher than that of the shale in the deformed region. The shale samples from the deformed region had larger pore volumes and primarily developed macropores. The difference in the meso-macropores is significantly greater than the difference in the microporous volume. Hence, the geological tectonism had a greater impact on the meso-macropores than on the micropores in the shale cores.

Application of Helicopter-Borne and Ground–Airborne Electromagnetic Detection to Tunnel Engineering Investigation

The Cedaya-S340 Holgutu Highway Construction Project is located in the Mongolian Autonomous Prefecture of Bayingolin in the Xinjiang Uygur Autonomous Region. It is an important traffic channel that connects Luntai County and Hejing County at the southern foot of Tianshan Mountains. As the major component of the highway project, the Huola Mountain Tunnel has a sharp topographic relief, and, therefore, commonly used land geophysical detection instruments cannot work on it. Therefore, we conducted a qualitative survey on the ground-to-air and airborne electromagnetic detection methods used at the Huola Mountain Tunnel site to provide basic data for the design of highway tunnels. The geophysical survey summarized the ground–airborne frequency-domain electromagnetic method (GAFEM) and the helicopter-borne time-domain electromagnetic method (HTEM) developed by Jilin University, and measured 15 measuring lines. Apparent resistivity imaging was performed for each section, and the results were consistent. This study comprehensively analyzed the apparent resistivity profile and geological mapping data. Then, the study inferred the major stratigraphic boundaries, fault fracture zones, rock fragmentation, weakness, karst development, and water content in accordance with background value, low-resistivity anomaly shape, low-resistivity anomaly value, and gradient value in the apparent resistivity profile. Finally, the study identified the scope of two main low-resistivity anomalies, located at the tunnel entrance and exit, respectively, which are basically consistent with the known fault location. The results of this study show that on the basis of the apparent resistivity maps of GAFEM and HTEM, the overall distribution law is basically consistent with site landform, hydrogeology, tectonic geology, and aerial image data. The results provide guidance for the construction of the Huola Mountain Tunnel and ensure the construction safety and progress of the tunnel.

Current Tectonic Stress State in an Iron Mine District, North China, Based on Overcoring, Hydraulic Fracturing, and Acoustic Emission Stress Measurements

Abstract Full knowledge of the current tectonic stress state is crucial for assessing open-pit mine slope stability and regional tectonic evolution and geodynamic processes. Overcoring, hydraulic fracturing, and acoustic emission in situ stress measurement techniques were adopted to determine the 3D stress tensor in an iron mine district, North China, and 25 sets of stress data ranging from 56 to 490 m were measured. Accordingly, the current tectonic stress state and its relationship to regional geological tectonics were investigated. The results indicated that the stress condition seemed to favor thrust and strike-slip faulting, and the stress field was particularly controlled by the horizontal tectonic stress. A high horizontal tectonic stress considerably influenced the stability of high and steep slopes in this mine district, which requires great attention. The stress directions derived from different methods were almost similar, indicating a dominant NEE–SWW stress field direction or near-E–W direction, comparable to the direction revealed by focal mechanism solutions and other stress indicators around the mine district. According to geological structure analysis, the present-day stress field in this district generally inherited the third-stage tectonic stress field while partially retaining the characteristics of the second-stage tectonic stress field, which is the result of dynamic action and tectonic movement during different geological periods, and the maximum principal stress direction of the tectonic stress field that affects the modern tectonic activity in this area is the NEE–EW direction.

An automatic modeling approach for the potential evaluation of CO2 geological storage in the deep saline aquifer

Geological storage of carbon dioxide is receiving more and more attention as one of the efficient carbon reduction technologies, as China’s carbon-neutral strategic plan moves forward. There is an increasing demand for more effective and thorough methodologies to assess the potential of CO2 storage in deep saline aquifers. This study proposes a method for evaluating the geological storage potential of CO2 in deep saline aquifers and constructs an automatic evaluation system for the comprehensive potential of CO2 geological storage using ArcGIS Model Builder visual modeling technology. The automatic evaluation system consists of four functional parts: information collating and database constructing, data pre-processing, model building evaluation and result validation evaluation. First, structured and unstructured data including underlying geology, tectonic geology, oil and gas geology, and drilling data are collated and established in a geodatabase. Second, pre-processing models of the deep saline reservoir-caprock data are established based on the analysis of the geological evolution history of the study area to determine the effective storage thickness, effective porosity, and the influence range of faults; kriging methods are then used to realize the spatial interpolation of the evaluation parameters. Third, the volume coefficient method is adopted to construct the underground storage space model and to establish the density distribution model of the supercritical CO2 with nonlinear function while taking into account four evaluation factors (i.e. area, effective porosity, effective thickness, effective coefficient) and two limiting factors (i.e. fault, burial depth). Finally, the geological storage potential of CO2 in the study area is evaluated with the classification of the potential level and compared with the numerical simulation results to verify the model’s accuracy. The model is first applied in this paper using a suitable target in China as a case study. The results show that this target area’s anticipated storage potential value reaches 52.557 Mt. The total precision error, according to a comparison of the numerical simulation results, is 8.20%. Based on the results obtained, it can be concluded that the automatic GIS-based modeling approach is suitable for a comparable study of potential evaluation of CO2 geological storage in deep saline aquifers.

Potential seismicity by impoundment of the Baihetan Reservoir, Xiaojiang Fault Zone, Southwest China

Baihetan reservoir, the second-largest hydropower station in China, is located at the east boundary of the Sichuan-Yunnan block, one of the most seismic active zones in continental China. Many studies have shown that the potential risk of reservoir-induced seismicity will ramp up when the crustal stress field is remarkably perturbed following its impoundment. In this work, based on the fully-coupled poroelastic theory, we built models with different parameters to quantitatively analyze the displacement and stress field changes caused by the Baihetan reservoir impoundment. The preliminary results show that the maximum subsidence reaches about 0.3 m, and the stress change is about 0.4 MPa at 5 km after five years of impoundment. Most strikingly, we find a significant increase of Coulomb Failure Stress Change (ΔCFS) on the fault planes at the vicinities of the surrounding Xiaojiang Fault, Daliangshan Fault, and Lianfeng Fault, suggesting high reservoir induced seismicity risks. However, the occurrence of induced/triggered earthquakes is not only related to the regional tectonic loading, but also the rock strength. Moreover, the reservoir water level rise rate will lead to different spatial–temporal patterns of the induced micro-seismicity, however, this difference will gradually disappear as the reservoir continues to operate, and the large earthquake is mainly affected by geological tectonics.

Genomic insights into zokors’ phylogeny and speciation in China

The phylogeny and speciation of subterranean zokors in China are unclear, as previous studies on morphology and limited molecular markers have generated conflicting results. This study unraveled the complex evolutionary history of eight zokor species in China based on de novo assembly at chromosome level and whole-genome sequencing of 23 populations. We found extensive phylogenetic discordances between nuclear and mitochondrial phylogenies, and different coalescent phylogenies, which could be explained by introgression and incomplete lineage sorting (ILS). The recent Qinghai-Tibet Plateau uplift (∼3.60 million y ago; Mya) drove Eospalax to speciate into clade A and clade B (∼3.22 Mya), and discordant phylogenies in this node were mainly attributed to introgression rather than ILS. Clade A rapidly diverged into three lineages due to geographical isolation and glaciation, while glaciation and C4 plant expansion contributed to the speciation of clade B. ILS contributed to the discordances of two rapidly radiated nodes rather than introgression. The effective population sizes (Ne’s) of all the species of Eospalax were affected by three glaciations. Ancient polymorphisms and divergence hitchhiking contribute to genomic islands of all the species pairs. Positively selected genes putatively related to specific inhabitation adaptations were identified, such as heart development, neurogenesis, DNA repair, and immune response. Climate, geological tectonism, and C4 vegetation shaped the adaptation and speciation of zokors in China.

What lies beneath the Deccan volcanic province? Perspective on tectonic elements and sub-trappean geology from gravity signatures

What lies beneath the Deccan volcanic province? Perspective on tectonic elements and sub-trappean geology from gravity signatures

Analytical model for tunnel face stability in longitudinally inclined layered rock masses with weak interlayer

In nature, rock masses often present non-horizontal layered characteristics due to geological tectonics. Tunnelling in such rock formations threatens and reduces the stability of the tunnel face. In addition, the existence of weak interlayer poses a potential threat to stability. In this study, an analytical model is established to comprehensively consider the influence of rock layer inclination and weak interlayer on the stability of the tunnel face. Then the virtual supporting force is obtained using the upper limit theorem of kinematic limit analysis with the nonlinear Hoek-Brown yield criterion. The optimal upper-bound solution is examined by the Genetic Algorithm. Several design charts are provided to analyze the effects of the tunnel diameter, inclination angle and weak interlayer on the stability of a tunnel face. The obtained results show that the instability of the tunnel face increases significantly due to the container of the weak interlayer. And the parameters of the lower-layer play a crucial role in the collapse of the tunnel face. Moreover, the effects of the position and thickness of the weak interlayer on the stability of tunnel face are discussed. The critical angle for the inclination of the rock layer leading to the most unstable state is remarked.

A Case Study of Thaumasite Sulfate Attack in Tunnel Engineering

There existed ever-increasing structural diseases in the Dugongling tunnel after the completion of the construction. Systematic research was carried out based on the information of tunnel engineering geology, disease development, mineral composition of surrounding rock and concrete, and laboratory tests. Results showed that (1) the concrete structure from the Dugongling tunnel suffered from a typical thaumasite sulfate attack (TSA); (2) tunnel diseases developed under the influence of multiple geological factors such as groundwater, karst, gypsum bearing stratum, and geological tectonics. Groundwater aggravated the appearance of engineering defects of various geological factors and accelerated the softening and swelling of surrounding rock. Moreover, the additional load of supporting structure increased, and the concrete structure was prone to sulfate attack; (3) the development of tunnel diseases showed long-cycle and large-scale characteristics, and the types of diseases are heterogeneous. The tunnel diseases develop rapidly in the third year after the construction. The structure collapse disease, one of the most serious diseases of tunnel lining, occurred in the fifth year after construction; and (4) according to the conditions of TSA, technical treatment measures were proposed. These measures included blocking the flow of CO 3 2 − , improving the impermeability of concrete structures, and decreasing the diffusion of external ions and groundwater. This work provides a solution for the treatment of similar tunnel disease and mechanism analysis.

Investigation on the Responses of Overburden Stress and Water Pressure to Mining under the Reverse Fault

This paper focuses on the responses of overburden stress and pore water pressure in confined aquifer to mining under the Ordovician limestone aquifer and the reverse fault. Taking 32 coal seam mining in the first eastern mining area of Qianyingzi coalmine in China as engineering background, on the basis of the mining hydrogeological and engineering geological model of the study area, a numerical calculation model considering the fluid-solid interaction is established. Simulation results indicate that the variation characteristics of pore water pressure in confined aquifer and overburden stress are affected by both mining effect and geological tectonics and are closely related to the shear failure of the reverse fault plane caused by mining effect and the failure characteristics of the overburden strata in the stope. According to the variation of pore water pressure before and after the roof water inrush, the reduction range of pore water pressure can be used as one of the early warning indicators for water inrush accidents. These new understandings are of reference value to the mining water inrush under the combined action of reverse faults and confined aquifers and to the establishment of corresponding forecasting and early warning systems.

Source Model and Simulated Strong Ground Motion of the 2021 Yangbi, China Shallow Earthquake Constrained by InSAR Observations

On 21 May 2021, an Mw 6.1 earthquake, causing considerable seismic damage, occurred in Yangbi County, Yunnan Province of China. To better understand the surface deformation pattern, source characteristics, seismic effect on nearby faults, and strong ground motion, we processed the ascending and descending SAR images using the interferometric synthetic aperture radar (InSAR) technique to capture the radar line-of-sight (LOS) directional and 2.5-dimensional deformation. The source model was inverted from the LOS deformation observations. We further analyzed the Coulomb failure stress (CFS) transfer and peak ground acceleration (PGA) simulation based on the preferred source model. The results suggest that the 2021 Yangbi earthquake was dextral faulting with the maximum slip of 0.9 m on an unknown blind shallow fault, and the total geodetic moment was 1.4 × 1018 Nm (Mw 6.06). Comprehensive analysis of the CFS transfer and geological tectonics suggests that the Dian–Xibei pull-apart basin is still suffering high seismic hazards. The PGA result demonstrates that the seismic intensity of this event reached up to VIII. The entire process from InSAR deformation to source modeling and strong ground motion simulation suggests that the InSAR technique will play an important role in the assessment of earthquake disasters in the case of the shortening of the SAR imaging interval.

Numerical simulation and analysis of complex fracture propagation during SC-CO2 fracturing using a thermal-hydro-mechanical coupling model

Supercritical CO2 has been widely used in shale fracturing due to the low interfacial tension and high diffusion characteristics. However, under the high pressure and temperature condition of shale reservoirs, the properties evolution of SC-CO2 cannot be accurately described with the cubic equations of state. And on the other hand, owing to the effects of sedimentation and geological tectonism the lamellation is commonly developed in the shale, which has a great impact on the fracture propagation. In order to explore the mechanism of complex fracture evolution during SC-CO2 fracturing of shale reservoirs, a thermal-hydro-mechanical coupling model is established with the extended finite element method, and the Span–Wagner equation of state is employed to obtain the SC-CO2 properties under high pressure. With the proposed model, a series of numerical examples are presented and discussed. It is found that fracture is inclined to propagate along the lamellation, and a complex fracture networks is easier to obtain in shale reservoirs developing complex lamellation. And in comparison with the water and oil, the fracture morphology generated by SC-CO2 is more complex than water and oil because of the high density and low viscosity.

Research on Coal Bed Methane (Gas) Occurrence Controlled by Geological Tectonics in the Southern Margin of North China Plate: A Case Study of the Pingdingshan Coalfield, China

The geological structure is complex in the plate margin zone, and the occurrence of coal bed methane (CBM) is nonuniform with an obvious zoning phenomenon. It plays an important role to reveal the spatial distribution of CBM and its influence factors in plate margin zone for CBM exploitation and gas disaster prevention in coal mines. Based on the data of gas emission during mining, CBM content, and gas pressure in the Pingdingshan Coalfield, lying on the south edge of North China plate, the distribution characteristics of CBM and its influence factors using theories of CBM (gas) geology and statistical analysis method are investigated. The research area is divided into four CBM occurrence belts. There are its own CBM occurrence feature and control structural type in each CBM belt. Likou syncline is the structure that controls the overall distribution of CBM. NW-trending fold-fault belt, Guodishan fault, and Jiaxian fault are the structures that control the CBM occurrence in CBM belt IV, CBM belt II, and CBM belt I, respectively. And the difference in structural types is the main factor of CBM zoning.

Stability analysis of open-pit gold mine slopes and optimization of mining scheme in Inner Mongolia, China

The geological structure of the Changshanhao open-pit mine in Urad Middle Banner, Inner Mongolia, China is extremely complicated, and slope instability has frequently occurred in various forms, such as wedge sliding, bedding sliding, and toppling failure. In order to study the failure mechanisms of these slopes, the geological structure and mechanical rock properties were investigated based on field investigations and laboratory tests. Numerical models for the present mining area and final mining area of the original scheme were established to analyze slope stability. The results showed that the unique geomorphological characteristics of the mining area were generated by geological tectonism, and the north side of the stope is an anti-dip layered rock slope and the south side is a dip layered rock slope. Slope failure is the consequence of endogenic and exogenic integration, including physical and mechanical properties of the rock mass, geological structures such as faults and joints, and human-caused factors such as blasting and excavation disturbances. Then the original excavation scheme was redesigned mainly by optimizing the slope angle and decreasing the final mining depth to maintain slope stability. Finally, the Monte Carlo method was used to analyze the reliability of the slope angle optimization scheme. The open-pit mine excavation plan that meets the stability requirements was obtained eventually.

Surface runoff estimation of Wadi Ba Al-Arid watershed North East Libya, using SCS-CN ,GIS and RS data

The aim of this study is to estimate runoff in Wadi Ba Al Arid watershed for a period of ten years 2009-2018 by Soil Conservation Service Curve Number (SCS-CN) method in combination with the GIS techniques using remote sensing data. The used data are the daily rainfall data from NASA Prediction of Worldwide Energy Resource (POWER), digital elevation data (DEM) from ALOS PALSAR RTC , satellite imagery from the European Space Agency (ESA) Sentinel, and soil data represented in soil maps of a scale 1: 50,000 and some local studies carried out by several Libyan institutions. The overall area of the watershed is about 136.4 km2 and perimeter107.3 Km. The watershed upstream and downstream is well recognized due to the topographical difference as a result of the tectonic geology. Soil maps were processed and classified into hydrologic soil groups (HSG), where the dominant HSG in the study area are C and D. The Landcover/Land use (LULC) was classified into five classes (forest, shrubs, agriculture, barren land) and built up. The HSG and LULC layers were intersected and the CN values and the weighted curve number for each Antecedent Moisture (AMC) condition were assigned. Furthermore, the runoff depth was estimated and the average runoff volume for ten years during 2009–2018 in the study area was estimated by 1.67 Mm3 which represents 4.6 % of the observed average annual rainfall as 264.3 mm during 2009-2018. The rainfall-runoff relationship has shown a strong correlation with the value of 0.75.

Pore structures of shale cores in different tectonic locations in the complex tectonic region: A case study of the Niutitang Formation in Northern Guizhou, Southwest China

The Cambrian Niutitang Formation shale reservoirs are widely distributed in the complex tectonic area in northern Guizhou. Fifteen organic-rich Niutitang Formation cores were selected from the tectonic deformation zones and tectonic stability zone in northern Guizhou, including the FC1 well related to fold, TM1 well related to faults, and TX1 well in the tectonic stability zone. Pore structures and reservoir physical properties of shale were tested via microphysical experiments and low-temperature nitrogen adsorption (LTNA) test. Results indicate that the thermal evolution maturity of shale is in the over mature stage, with RO distributed between 2.30 and 3.74% and the total organic carbon content (TOC) between 3.8 and 7.5%. Shale cores in the tectonic stability zone have higher TOC content (6.25%) than that of shale (5.16%) in the tectonic deformation zones. Shale cores in the tectonic deformation zones have higher thermal evolution maturity Ro (2.98%) than that of shale (2.76%) in the tectonic stability zone. The pore size of shale cores ranges from 4.15 to 15.62 nm. The total pore volume of shale cores ranges from 9.71 to 33.20 cm3/kg, and the meso-macropore volume ranges from 7.4 to 28.21 cm3/kg. Shale cores in the tectonic deformation zones have higher average pore size, total pore volume, and meso-macropore volume percentage than that of shale cores in the tectonic stability zone. Meanwhile, the specific surface area of shale cores (SBET) ranges from 7.34 to 30.37 m2/g, and the micropore volume of shale cores ranges from 2.29 to 5.82 m3/kg. Shale cores in the tectonic stability zone have higher micropore volume, specific surface area, and percentage of micropore volume than that of shale cores in the tectonic deformation zones. Shale cores in the tectonic stability zone mainly develop micropores and mesopores. Mesopores and macropores are more susceptible to geological tectonism than micropores. The pore structures of shale in the tectonic stability zone have been effectively preserved during tectonic movements. The research results have certain guiding significance for the exploration of shale gas in the complex tectonic regions.

Evaluation of permeability damage for stressed coal with cyclic loading: An experimental study

Permeability and its evolution directly control the flow behaviors of the subsurface energy fluid extractions. Coalbed is known as a fractured, dual-porous media, and whose permeability is directly related to effective stress and the manner of stress loaded and unloaded. Coal has been historically treated as a transverse isotropic media and the permeability can also be influenced by the sorption induced deformations. As a cleat-rich porous medium, coal is potentially bearing various loading paths, such as fracturing, mining and natural geological tectonics activities. The permeability variation under cyclic loading and different stress paths is crucial for the engineering design for both mining and gas extractions from coal seams. The pulse-decay method was employed to estimate the permeability of cylinder coal specimen. An average permeability damage concept with a complete loading-unloading cycle is introduced to quantify the effects of maximum stress, loading path, holding time period, and gas type on permeability evolution. It was demonstrated that the permeability hysteresis occurred during the cyclic loading-unloading, and that the average permeability damage was subject to the loading-unloading paths. The average permeability damage for the coal specimen is more sensitive to maximum loading stress and the loading-unloading path compared to gas injection pore pressure and the holding period. Gas adsorption induced swelling dramatically reduced the initial permeability and average permeability damage during cyclic loading. The permeability evolution was analyzed through poroelastic theory coupled with the matrix shrinkage concept. When applied to permeability and stress relationship, Biot's coefficient should be cautiously applied for coal reservoir because it could be larger than unity when the adsorption induced non-elastic swelling is considered, and it even could be negative when the irreversible cleats closure is considered.