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Abstract The development of coalbed methane (CBM) in China is susceptible to the influence of microstructure. Therefore, it is crucial to understand the extension laws of hydraulic fractures and engineering responses in coal reservoirs affected by microstructure development. Utilizing the Dahebian block in western Guizhou as the study area, this investigation examines the coal reservoir characteristics, fracturing, and drainage engineering analysis of the well DC1 group in the region. The aim is to discuss the spatial distribution characteristics of hydraulic fractures, geological controlling factors influenced by microstructure, and their corresponding engineering responses. The results indicate that, for coal reservoirs unaffected by microstructure, the extension laws of the fracture network in both longitudinal and planar directions are influenced by burial depth and the regional stress field. In the microstructural belt, tectonic stress dominates, causing changes in the ground stress field. Consequently, the hydraulic fracture network deviates from the direction of the maximum principal stress during the extension process. When a secondary fracture is nearby, the hydraulic fracture network extends towards the shortest path radial secondary fracture direction, leading to a rapid increase in fracture width per unit length until it intersects with the secondary fracture. Additionally, the presence of secondary joints near the microfault structure decreases fracturing pressure and results in a dense distribution of the fracture network. This promotes the formation of a complex fracture network, favorable for fracturing. The extension of the fracture network in complex structural development areas is influenced by the microfault structure between wells, which is reflected in the fracturing construction pressure and fluid output. This accounts for the significant variations in the early drainage performance of CBM wells.

The Xinjiang Uygur Autonomous Region has presented the expected resource conditions and work foundations for a large-scale coalbed methane (CBM) exploration and development, which shows that its CBM resources below the depth of 2000 m are 7.5 trillion m3, 450 CBM wells have been constructed, and the annual gas production has approached to 80 million m3. Xinjiang has put forward the goal of the annual CBM production of 2.5 billion m3 in 2025. Therefore, the large-scale and efficient development of CBM in Xinjiang has become an urgent and significant demand. In this paper, the main research progresses of Xinjiang CBM made in five key technical fields have been systematically summarized, including the CBM enrichment model and area optimization technology, the prediction and detection technology for sweet spot distribution, the technological strategy of the accelerated rolling development and rapid increase of reserves and productions, the geological adaptation technology system, and the cooperative exploration and development of CBM with coal, oil and gas. Then, the potential breakthrough directions have been analyzed and proposed. Research has shown that the coal reservoirs in Xinjiang show the unique geological characteristics of CBM, including widely developed multi-thick coal seams, low rank coal development, the frequent occurrence of steep coal seams, the significant deformation and structural control of coal bodies, complex hydrologic and outcrop conditions, and the gas-bearing and physical properties with three “low” (low gas content, methane concentration, and gas saturation) and five “high” (high gas intensity, porosity, stress change, reservoir pressure change, and permeability change). The Xinjiang CBM has multiple genetic types and enrichment models, including biogenic mechanism, thermogenic mechanism, and biogenic-thermogenic composite genetic mechanism, etc., and their corresponding enrichment models. Biogenic gas reservoirs or biogenic gas contribute widely. The distribution and occurrence patterns of CBM in Xinjiang show some significant differences between foreland basin and intermountain basin. Therefore, the first breakthrough direction is to innovate and form the scientific evaluation based on the principle of “two separation” (low-rank and middle- and high-rank; shallow and deep coal) and “two combination” (geological and engineering evaluation; multivariate data) and the precise target optimization technology based on “machine learning + three-dimensional geological modeling”. The sweet spot of deep CBM/CMG (coal measure gas) in Xinjiang is mainly the uplift of the depression in the basin, the depression of the uplift in the basin, and the slope around the basin margin. The potential well location is the structurally high position, and the potential reservoir is the fissure-developed primary structure coal seam or pore and fissure-developed coal bearing sand conglomerate reservoir. Then, the second breakthrough direction is the sweet spot prediction and exploration technology for deep CBM/CMG based on “new method of geophysics, rock physics and rock mechanics stratigraphy” and “new concept of geological and engineering sweet spot”. The basic principles of the accelerated rolling development are low-risk, short-cycle, high-efficiency, and multi-batch project deployment. The technical strategies of the rapid increase of CBM reserves and productions in the middle and shallow coal seams include the new well layout and construction in the new optimized block and the old well reconstruction for the increase of CBM production in the mature block. While this strategy for the deep coal seam is to give priority to deployment and development in the sweet spot in the deep but gentle slope in the large basin and the uplift in the basin. Then, the third breakthrough direction is the engineering deployment methods and technical strategies for the scientific accelerated rolling development, and efficient and rapid increase of the gas reserves and productions. The important progresses have been made in the engineering technologies of Xinjiang CBM, such as the differential optimization and deployment of the well type and pattern, the drilling and cementing with a low reservoir damage, the high reliability logging and well testing, the efficient staged fracturing with the multi-well types, and the drainage control with the low casing pressure and controlled pressure. The fourth breakthrough direction is to develop and construct a geological adaptability technology system for a large-scale and efficient exploration and development of CBM in Xinjiang. For the middle and shallow CBM and coal cooperative exploration and development, the gas extraction followed by coal mining, the co-extraction of CBM and coal, and the co-extraction of CBM and in-situ oil-rich coal should be conducted. For the deep CBM, oil, and gas cooperative exploration and development, the development of coal measure superimposed gas reservoir, the co-exploration and co-extraction of CBM and CMG, and the exploration and development of the whole petroleum system in coal-bearing sequence should be conducted. These cooperative exploration and development of deep CBM, oil, and gas is the fifth breakthrough direction, whose developments have been considered and explored. The results of this study are expected to provide the technical support and engineering decision reference for a large-scale and efficient exploration and development of CBM in Xinjiang.

Guizhou Province has many multi-layer, thin-thick coal seams; however, complex geology, incomplete reservoir characterization, and sweet-spot selection technology prevent large-scale coalbed methane (CBM) development. This study evaluates the CBM reservoir properties within the Dahebian block using logging data, coal sample analysis, and well-testing data and develops a 3D static reservoir properties model to analyze their spatial and vertical propagation. A sweet spot evaluation model was established using a multi-level fuzzy method based on 9 parameters extracted from a 3D static reservoir properties model. The coal measure has 22 coal seams, and seams >2 m thick have 2 or 3 thin non-coal layers intercalated. Coal seams 1#, 7#, and 11# are thin to thick, deeply buried, widely distributed, and have high gas content and saturation. Undeformed and cataclastic coal predominates the coal seam 1# and 7#, whereas coal seam 11# is dominated by cataclastic and granulated coal. The southern and central parts of coal seam 7# and 11# have less tectonically deformed coal (TDC). Coal seams 1# and 7# have low permeability relative to seam 11# and are localized, while coal seams 11# have high permeability, are extensively distributed, and contain substantial gas concentrations. Comparative analysis of evaluation scores and CBM production statistics shows that high scores indicate sweet spots for CBM development. Sweet-spot potential was classified as high, medium, and low. Scattered sweet spots are found in single layers, while combined development (1# + 7#+11#) reveals a wider high-potential area in the south-central region. This area, featuring deep, thick coal seams, high permeability, gas saturation, reservoir pressure, and low TDC proportion, indicates significant development potential. This study validates CBM development statistics, identifies future development areas, and guides the development of geologically complex Guizhou CBM.

Broken soft and low permeability (BSLP) coal reservoirs are widely distributed in China. However, due to its soft and broken structure and low permeability, the conventional vertical/horizontal well direct fracturing technology is not ideal for the enhancement of BSLP coal seams and the surface development of coalbed methane (CBM). The efficient development of CBM in BSLP coal reservoirs has been an important technical bottleneck restricting the large-scale development of CBM industry and the efficient treatment of coal mine gas control in China. Based on the systematic analysis of the characteristics of BSLP coal reservoirs and the problems existing in the surface development of CBM, the current technological progress in the enhancement of BSLP coal reservoirs and surface development of CBM were reviewed by taking horizontal well as the base well type and focusing on three different technical directions: indirect fracturing, stress relief and consolidation before fracturing. The CBM development technologies of indirect fracturing, including roof indirect fracturing, gangue indirect fracturing and hard coal stratification indirect fracturing were summarized. The stress release CBM development technologies using different stress release methods, such as hydraulic jet cavitation, gas dynamic cavitation, mechanical + hydraulic + induced instability coupling cavitation and hydraulic slit, were reviewed. Furthermore, the CBM development technology of first consolidation and then fracturing of BSLP coal reservoirs induced by microorganisms was also summarized. The exploration of indirect fracturing technology has accumulated a lot of engineering practice, and has achieved a good effect on enhancing the BSLP coal reservoirs in areas with suitable geological conditions. The exploration of new technology for enhancing BSLP coal reservoir represented by stress release has also made great progress, and has entered the stage of engineering tests and verification. According to the characteristics of BSLP coal reservoir and the new development principle, the horizontal well stress release technology has greater potential for reservoir reconstruction and better effect for CBM development. Based on the horizontal well stress release method, the development trend of BSLP coal reservoir enhancement and surface CBM development technology was forecasted in three aspects: expanding the stress release range, improving the development effect of CBM and achieving the co-production of coal and CBM. It is expected to provide reference for improving the stimulation effect of BSLP coal reservoir and increasing the production of CBM well in China.

In the process of CO2-ECBM, the tectonic fractures developed in the coal may become the preferential channels of gas-water seepage under the impact of injection pressure, and then influence the recovery of coalbed methane (CBM) and CO2 storage. Based on the theoretical analysis, the displacing profile of CO2-ECBM is established. A numerical model is constructed referring to the TS-634 field trial, and the influence of the tectonic fractures on CH4 recovery and CO2 storage is investigated. The CBM recovery and CO2 storage in the TS-634 trial are evaluated, the mechanism of the rapid breakthrough of CO2 is revealed, the enlightenment of the rapid breakthrough on the optimization of the injection-drainage process is dissected, and the proposals for the injection-drainage process in reservoirs with tectonic fractures are put forward. The results show that CO2 enriched zone, CH4-CO2 mixed zone, CH4 enriched zone, and water enriched zone can be formed among injection-production wells successively. With an injection, the zones affect the producers after their formation and evolution. The difficulty of water seepage determines the level of CH4 output inhibition and then controls the CBM recovery and CO2 storage. The producer along tectonic fracture can achieve an efficient recovery of CH4, but a high permeability often leads to apparent CO2 channeling which causes the loss of cumulative CH4 production and CO2 storage. During the trial period, the strong-breakthrough producer attains a remarkable increase in gas output, with the actual cumulative gas production increasing by 10.4% and bottomhole-pressure-equivalent cumulative gas output increasing by 92.3%. Tectonic fractures provide potential preferential channels for the CO2 rapid breakthrough and become real preferential channels mainly induced by injection pressure. The existence of fracturing affected areas and liquid CO2 phase transformation-induced expansion and energization accelerate the CO2 breakthrough, but the coal matrix expansion-induced permeability decrease is expected to delay the breakthrough. To achieve a better displacement, enhancement, and sequestration, it is necessary to boost the bottomhole pressure in the early injection stage, fine-tune the pressure of the injector or increase the bottomhole pressure drop of producers in the inhibition stage, and maintain the pressure lower than the minimum principal stress of the reservoir in the whole stage. After the breakthrough, the exposure time between CO2 and coal matrix can be increased by irregularly shutting down/restarting the producers or reducing the pressure of the injector, which is expected to further improve the CH4 recovery.

Large-scale cluster deployment is the development direction of the CCUS (Carbon Capture, Utilization and Storage) technology and the national major demand of fossil energy low-carbon utilization. The synergistic relationship and mechanism between CO2 geological storage potential and energy resources are the theoretical basis of the CCUS large-scale cluster deployment. In this study, the major progress in the fields of CO2 geological storage potential and its evaluation methods, the CCUS source-sink matching and pipe network design model, the synergistic relationship between CO2 geological storage potential and energy resources, and the technical basis and mode of the CCUS cluster deployment are systematically reviewed. The research ideas on the theoretical methodology of synergy between CO2 geological storage potential and energy resources in China are discussed and envisioned. The main conclusions of the research are as follows. The CO2 geological storage potential restricts the development potential and application scale of the CCUS technology. The evaluation method system of CO2 geological storage potential is preliminarily established, which is composed of suitability evaluation method, storage capacity evaluation method, and storage site selection method. However, the evaluation method system of CO2 geological storage potential urgently needs to be improved and developed in future research. Source-sink matching is the important direct basis for the CO2 transportation pipeline network design and the CCUS large-scale cluster deployment. The improvement and establishment of the optimization model between the CCUS source-sink matching and the CCUS cluster pipe network model is the key technology for the CCUS source-sink matching, and the transformation from single-stage static planning model to multi-stage dynamic planning model is the development direction. The synergy between CO2 geological storage potential and energy resources constitutes the constraint condition of the CCUS technology. The synergy between the CCUS technology and new energy technology, e.g., renewable energy, hydrogen energy, energy storage, etc. will be expected to form a new path, new mode, and new direction to achieve energy system decarbonization. The synergistic relationships between CO2 geological storage potential and biomass and water resources restrict the large-scale deployment area of the CCUS technology and the application potential of the BECCS (Bioenergy with Carbon Capture and Storage) technology. Therefore, the research on the optimization model of energy and resources system based on the CCUS source-sink matching model will be a new technical requirement. The CO2 geological storage potential, energy-system constrained CCUS source-sink matching optimization scheme, and full flowsheet CCUS technology constitute the key technical basis for the CCUS cluster deployment. The CCUS cluster deployment mode of onshore storage with near-source transportation should be the priority development direction in China. The CCUS cluster deployment mode of onshore storage and offshore storage with remote-source transmission also have development prospects in Yangtze River Delta and Great Bay Area.

CO2 geological sequestration-enhanced coalbed methane (CO2-ECBM) strengthens the development of coalbed methane (CBM) and realizes the stimulation of coalbed methane wells. At the same time, CO2 is stored in deep coal seams. This technology has some great development prospects. Relying on the demonstration project, numerical simulation based on geological modeling is still an important path for its technological development. Based on the analysis of the characteristics for the corner grid geological model and the geological modeling ability of COMSOL Multiphysics, a geological model that can clearly display the three-dimensional spatial morphology and heterogeneity distribution of gas content, adsorption time, porosity, permeability, elastic modulus and Poisson’s ratio of the No. 3 coal in the Shizhuang South Block of Qinshui Basin was established in COMSOL Multiphysics using the split-reconstruction method. On this basis, the numerical simulation of CO2-ECBM for controlling gas injection pressure was carried out in combination with the adsorption-hydraulic-thermal-mechanical-chemical (AHTMC) multi-field coupling mathematical model, and the impact of CO2 injection pressure on CH4 stimulation, CO2 storage and the geochemical environment of coal reservoir were analyzed. Moreover, two kinds of shut-in modes, namely, simultaneous shut-in and sequential shut-in, and four CO2-ECBM engineering objectives, namely, time saving, CH4 stimulation, CO2 storage and comprehensive consideration of the three, were proposed. In addition, the CO2 injection pressures were optimized according to the two shut-in modes with the four objectives. The results show that: ① Under the limit of 15-year and the injection pressure of 5.50−9.50 MPa for the CO2-ECBM project, with the increase of CO2 injection pressure, the CH4 production rate of CBM wells and the CO2 storage capacity of coal reservoir increase, with the maximum of 14.39% and 8.31×107 m3 respectively, the area of coal reservoir containing acid fissure water expands. The CO2 storage rate decreases due to the large output of CO2 from CBM wells with the increase of gas injection pressure, but remains above 95%. ② The heterogeneity of coal reservoirs has a great impact on the production of CBM wells. The higher the CH4 content and the greater the porosity and permeability of the coal reservoirs around the CBM wells, the more significant the CH4 stimulation effect. The stronger the CO2 adsorption capacity of the coal reservoirs surrounding CBM wells, the lower their CO2 production rate. ③ Under the simultaneous and sequential shut-in, CO2 injection pressure has a significant impact on the CO2 concentration and CH4 production rate of gas produced by well group, and the CH4 recovery of coal reservoir decreases with the increase of injection pressure at the end of CO2-ECBM project with 33.28% and 41.63% for 3.50 MPa, 18.90% and 28.03% for 6.50 MPa and 12.81% and 23.01% for 9.50 MPa, respectively. ④ The optimal injection pressure of CO2 for the engineering objectives of time saving, CH4 stimulation, CO2 storage and comprehensive consideration of above three are 8.05, 3.50, 6.35 and 6.25 MPa for the simultaneous shut-in, respectively, and 9.50, 9.50, 3.50 and 9.50 MPa for the sequential shut-in, respectively. ⑤ Compared with simultaneous shut-in, the sequential shut-in can achieve better CH4 stimulation and CO2 storage effects by extending the engineering time when using the optimal CO2 injection pressure.

During the hydraulic fracturing of coalbed methane (CBM) well, the deposition of coal fines in propped fractures and the migration of coal fines in cleats will damage the permeabilities of propped fractures and cleats, consequently affecting the hydraulic fracturing and the subsequent drainage of CBM well. For the purpose of dredging propped fractures and avoiding the clogging of cleats effectively, a novel method for the control of coal fines in propped fractures and cleats during hydraulic fracturing was proposed by optimizing the salinity of fracturing fluid. With the salinity decreasing stepwise, the experiments on the migration of coal fines in propped fractures and cleats were conducted on quartz sand-packed columns and anthracite coal plugs, respectively, to investigate the response characteristics of the migration of coal fines to the change of salinity. Additionally, the migration of coal fines was simulated by using the extended DLVO method, to elucidate the influence mechanisms of salinity on the migration of coal fines. On this basis, the optimal salinity range that takes into account the control of coal fines in propped fractures and cleats was explored. The results indicated that there existed a critical salt concentration (CSC) for the migration of coal fines in both propped fractures and cleats. When the salinity was lower than the CSC, the permeability of propped fractures abruptly increased while that of cleats decreased sharply, accompanied by a large amount of coal fines produced. The value of the CSC for the migration of coal fines in propped fractures was higher than that in cleats, which can be attributed to the fact that the surface electronegativity of proppants was stronger than that of cleats, while the hydrophobicity was weaker than that of cleats. With the gradual decrease of salinity, the electric double layer (EDL) repulsive force between coal fines and channel increased continuously. When the salinity decreased to the CSC, the EDL repulsion started to be greater than the sum of Lifshitz-van der Waals attraction and Lewis acid-base attraction, resulting in the migration of coal fines. Both the values of the predicted CSCs for the migration of coal fines in propped fractures and cleats were consistent with experimental data, indicating the effectiveness of the model. During hydraulic fracturing, the salinity of fracturing fluid can be designed between the CSCs for the migration of coal fines in propped fractures and cleats. In that case, the production of coal fines in propped fractures is promoted while the migration of coal fines is inhibited in cleats, so as to achieve the dual purposes of coal fines control in propped fractures and cleats.

As an important component of coal structure, the macropores have a great influence on CBM recovery. In this paper, the macropores characteristic of two coal samples collected from 3# coal seam in the south of Qinshui Basin, China was analyzed on the basic of mercury intrusion porosimetry, and a fully coupled triple-porosity/double permeability mathematical model for CBM recovery was established according to the physical structure of coal and the non-Darcy flow of methane in macropores. Then, the various factors affecting the macropores permeability were discussed and the influence of size distribution and connectivity of macropores on CBM recovery was investigated. The following conclusions have been drawn from these efforts: (1) in 3# coal seam of the south of Qinshui Basin, the macropores have an extremely heterogeneous pore size distribution with the high variation, and their connectivity is not good because they are mainly composed of the conical and cylindrical pores with one dead end and the open pores, the structure characteristics of macropores are not conducive to CBM recovery; (2) the fully coupled triple-porosity/double permeability mathematical model containing the non-Darcy flow of methane in the macropores includes the methane occurrence-migration field, hydraulic field, thermal field and stress field as well as the complex intercoupling between them, and the model was verified by the fitting of methane production history, with an average error of 3.24%; (3) the macropores permeability is closely related to the Knudsen number controlled by methane pressure and temperature in macropores and the intrinsic permeability which is an internal attribute of macropores affected by size distribution and connectivity of pore; (4) the pressure drop of reservoir plays a major role in the macropores permeability, which promotes the increase of macropores permeability with time, and the high intrinsic permeability of macropores corresponding to the good pore size distribution and connectivity is more conducive to the improvement of fracture permeability and methane production rate of coal reservoir during CBM recovery. It is recommended that coal seams including the macropores with uniform size distribution and good connectivity should be preferentially used for the development of CBM.

The macroscopic structural fractures (joints) and geostress distribution characteristics of coal reservoirs are important factors affecting the exploitation of coalbed methane (CBM). In this study, the joints in the sedimentary strata of the Dahebian block in Liupanshui area, Guizhou Province were investigated. Directional coal samples were collected for observation and statistical analysis of coal microfractures, the paleotectonic stress fields of the study area were reconstructed, and the tectonic evolution was elucidated. The geostress distribution characteristics of the target coal seam (coal seam No. 11, P3l) in the study area were analyzed using the finite element numerical simulation method. The results indicate that the structural evolution of the Dahebian syncline in the study area can be divided into two stages. The Late Jurassic–Early Cretaceous stage (Early Yanshanian) is the first stage. Affected by the sinistral strike slip of the Weining–Ziyun–Luodian (WZL) fault zone, the derived stress field in the study area exhibits maximum principal stress (σ1) in the NEE–SWW direction. The Late Cretaceous stage (Late Yanshanian) is the second stage. Affected by the dextral strike slip of the WZL fault zone, the derived stress field exhibits σ1 in the NNW–SSE direction. The folds and faults formed in the first stage were modified by the structural deformation in the second stage. The dominant strikes of joints in the sedimentary strata are found to be in the NW–NNW (300°–360°) and NE (30°–60°) directions, with dip angles mostly ranging from 60° to 90°. The dominant strikes of coal microfractures are in the NW (285°–304°) and NE (43°–53°) directions. The distribution of geostress in the study area is characterized by high levels of geostress in the syncline center, decreasing towards the surrounding periphery. The overall trend of the geostress contour line is similar to the shape of the syncline and is influenced by folds and faults. The σ1 of coal seam No. 11 is vertical stress. The prediction results show that the joint density of coal seam No. 11 in the block is 36–50 joints/m, and the shape of the joint density contour line is also affected by the axial direction of the Dahebian syncline and the surrounding faults. The variation in coal seam joint density and the control effect of geostress on joints opening or closing affects the permeability of coal reservoirs. The study results provide significant guidance for the exploitation of CBM.

Cork spot is a common physiological disorder in pear fruits, which has been found in some pear cultivars. Mineral nutrition imbalance in fruit is regarded as the principal influence factor for disorder incidence, with some ongoing confusion and controversy. In our research, we explored the cork spot characteristics in Japanese pear ‘Akizuki’ (Pyrus pyrifolia Nakai), adopted metabolome and mineral content analysis for healthy and disordered fruits, and made a correlation analysis of mineral and metabolites. Cork spots are mainly distributed on the outer flesh beneath the fruit peel. In cork spotted tissues, superoxide (SOD) and peroxidase (POD) activities, as well as malondialdehyde (MDA) content, increased. A total of 1024 known metabolites were identified from all the samples and more changes in metabolism were detected between normal and cork spotted flesh tissues. Correlation analysis displayed that Ca, especially the Mg/Ca in fruits, could be used to predict whether an orchard will develop cork spot disorder; Mg and B were associated with the appearance of symptoms, and the contents of Zn, Fe, and Mg, as well as Mg/B and Zn/B, might be strongly tied to the formation of cork spots in pears. This research provides insights into the occurrence of pear cork spot disorder and clarifies the role of minerals.

Abstract The coal seam gas development in closed gob zone is still in the exploratory stage in China, and potential evaluation and sweet spots selection are the key issues. This paper establishes a complete evaluation system for selecting sweet spots for closed gob methane extraction with surface wells in the Tiefa mining area to reduce the blindness of area selection. The one‐vote veto system, the comprehensive evaluation index system, and the AHP‐entropy combined weight model are used to screen and evaluate the closed gob zones in the Tiefa mining area. A total of twenty evaluation units are evaluated and the development potential of which is classified as three levels by the optimal segmentation method. The relationship between the results of the assessment and the closed gob methane resource is also discussed, as well as the combined weight distribution coefficient. The results show that the development potential of the block cannot be estimated simply by the closed gob methane resource because the consistency between the comprehensive evaluation value and the closed gob methane resource is poor. The size of the combined weight distribution coefficient has little effect on the comprehensive evaluation values and only affects the ranking of evaluation units in a small range.

In order to explore the influences of effective stress change on gas adsorption–desorption behaviors, primary undeformed coal (PUC) and tectonically deformed coal (TDC) from the same coal seam were used for adsorption–desorption experiments under different effective stress conditions. Experimental results showed that gas adsorption and desorption behaviors were controlled by the coal core structure and the pore-fissure connectivity under effective stress. The coal matrixes and fissures were compressed together under effective stress to reduce connectivity, and it was difficult for gas to absorb and desorb as the stress increased in primary undeformed coal. The loose structure of tectonically deformed coal cores can help gas to fully contact with the coal matrix, resulting in higher adsorption gas volumes. The support of coal particles in tectonically deformed coal cores weakens the compression of intergranular pores when effective stress increases, which in this study manifested in the fact that while the volumetric strain of the coal matrix change rapidly under low effective stress, but the adsorbed gas volume did not decrease significantly. The reduction in effective stress induced the rapid elastic recovery of the coal matrix and the expansion of cracks, and increased desorption gas volumes. The stress reduction significantly increased the initial gas volume of the tectonically deformed coal, while promoting slow and continuous gas desorption in primary undeformed coal. Therefore, the promotion effect of the reservoir pressure reduction on gas desorption and coal connectivity enhancement can help to improve coalbed methane recovery in primary undeformed coal and tectonically deformed coal reservoirs.

Indentifying reservoir characteristics of coals and their associated shales is very important in understanding the co-exploration and co-production potential of unconventional gases in Guizhou, China. Accordingly, comprehensive experimental results of 12 core samples from well LC-1# in the northern Guizhou were used and analyzed in this paper to better understand their vertical reservoir study. Coal and coal measured shale, in Longtan Formation, are rich in organic matter, with postmature stage of approximately 3.5% and shales of type III kerogen with dry gas generation. All-scale pore size analysis indicates that the pore size distribution of coal and shale pores is mainly less than 20 nm and 100 nm, respectively. Pore volume and area of coal samples influenced total gas content as well as desorbed gas and lost gas content. Obvious relationships were observed between residual gas and BET specific surface area and BJH total pore volume (determined by nitrogen adsorption). For shale, it is especially clear that the desorbed gas content is negatively correlated with BET specific surface area, BJH total pore volume and clay minerals. However, the relationships between desorbed gas and TOC (total organic carbon) as well as siderite are all well positive. The coals and shales were shown to have similar anoxic conditions with terrestrial organic input, which is beneficial to development of potential source rocks for gas. However, it may be better to use a low gas potential assessment for shales in coal-bearing formation because of their low S 1 +S 2 values and high thermal evolution. Nevertheless, the coalbed methane content is at least 10 times greater than the shale gas content with low desorbed gases, indicating that the main development unconventional natural gas should be coalbed methane, or mainly coalbed methane with supplemented shale gas.

Introduction: Patient self-management skills are an important part of heart failure (HF) management. However, there is a lack of knowledge about the effectiveness of nurse-led education on patient self-management and the associated clinical outcomes of rural Chinese patients with chronic heart failure (CHF). As such, this study was designed to evaluate the impact of a nurse-led education program on patient self-management and hospital readmissions in rural Chinese patients with CHF. Methods: Ninety-six patients in the eastern Chinese province of Shandong with CHF were randomly divided into intervention and control groups. A structured education program was delivered to the intervention group during hospitalization and after discharge. Control group patients were managed as per clinical guidelines without structured education. Medication adherence, dietary modifications, social support, and symptom control were assessed 12 months after the educational intervention. Results: The mean score of medication adherence, dietary modifications, social support and symptom control in the intervention group was higher than in the control group at the end of the study (p<0.01). The readmission rates for HF in the intervention and control group were 10.4% and 27.1%, respectively (p=0.036). Conclusions: This study has demonstrated that a structured education program was associated with a significant improvement in medication adherence, dietary modifications, social support, and symptom control in rural CHF patients. Furthermore, this program was associated with a significant reduction in hospital readmission. This study indicates that implementation of a nurse-led education program improves self-management and clinical outcomes of rural CHF patients, who may not have regular access to cardiac management services as per metropolitan populations. [ABSTRACT FROM AUTHOR]