The optimal selection of favorable reservoir is a fundamental and necessary task after logging and before fracturing operations, which can help improve the success rate of coalbed methane exploration. The target coalbed reservoir of the first coalbed methane exploration well, Kexin1H, in the Turpan-Hami Basin is located at a depth of 3163~3350 meters. The geological characteristics analysis and optimal selection of a favorable reservoir of coalbed methane are of great significance for subsequent exploration and development. This study conducted more than 270 tests on coal quality, coal structure, in-suit gas content, as well as isothermal adsorption, porosity, permeability, stress sensitivity, rock mechanics, and other parameters, providing a comprehensive understanding on the deep coalbed methane reservoir in the Turpan-Hami Basin and a deep analysis on optimal selection of favorable reservoir. The results show that: ① coals in the Xishanyao Formation drilled by Kexin1H well have a vitrinite reflectance ranging from 0.64 % to 1.02 %, with vitrinite content ranging from 63.40 % to 89.57 %. Based on the industrial analysis results of coal-rock, it is believed that the main coal seam is a long-flame coal or non-caking coal reservoir; ② based on the measurements of closed-core and isothermal adsorption, the gas saturation of coal rock reservoir ranges from 1.47 to 1.98. The three-axis elastic modulus and Poisson's ratio of coal rock are between 3.594 GPa to 7.795 GPa and 0.17 to 0.27, respectively. The coal structure is mainly fractured coal and granular coal. The coal rock reservoir belongs to the over-saturated, medium-low rank, fractured-soft, low-permeability, and strong stress-sensitive reservoir; ③ an evaluation index system for the optimal selection of a favorable reservoir in a single well based on fuzzy analytic hierarchy process was developed, which includes three main categories of primary indicators and twelve secondary indicators. It is believed that the producibility of the coalbed reservoir in the third section of Well Kexin 1H is high in production potential. However, attention should be paid to the impact of coal fines during engineering operations.

The pore structure of coal plays a critical controlling role in coalbed methane storage and seepage. Based on constant-rate mercury intrusion porosimetry, low-temperature nitrogen adsorption, and low-field nuclear magnetic resonance tests, this study comparatively analyzes the differences in pore-throat structures between shallow and deep high-volatile bituminous coal (HVBC) samples from the foreland thrust belt of Xinjiang and their implications for coalbed methane exploration and development at varying depths. The key findings are as follows: (1) Constant-rate mercury intrusion porosimetry results indicate that, compared to shallow HVBC samples, deep HVBC samples exhibit a larger peak macropore radius, stronger heterogeneity in throat size distribution, and a higher pore-throat radius ratio. (2) Low-temperature nitrogen adsorption results reveal that deep HVBC samples have less developed micropores and mesopores than shallow's, with predominantly interconnected cylindrical pores and open slit-shaped pores. (3) Low-field nuclear magnetic resonance results demonstrate that deep HVBC samples contain more mesopores but fewer macropores and fractures compared to shallow's. (4) Shallow HVBC has better-developed micropores, mesopores, macropores, and fractures, along with a lower pore-throat radius ratio, influenced by post-coalification deep burial followed by uplift and exhumation. In contrast, deep HVBC exhibits a high pore-throat ratio under weak modification effects due to deep burial and compaction.

Fluid inclusion analysis serves as an effective tool for investigating hydrocarbon reservoir mechanisms. This study systematically reviews hydrocarbon-bearing fluid inclusions in sedimentary strata through four aspects: research targets, methodological frameworks, research advancements, and applications in hydrocarbon accumulation mechanisms. It summarizes the current research status, key achievements, and unresolved challenges in this field. The phase states, spatial distribution, and physicochemical properties of fluid inclusions in petroliferous basins constrain key parameters including hydrocarbon generation/expulsion timing, source rock maturity, migration pathways, reservoir formation timing, and paleo-reservoir identification, and provide critical constraints for hydrocarbon accumulation mechanisms. Fluid inclusion analysis in petroliferous basins is based on three fundamental assumptions: closed system, homogeneous system, and isochoric system. By reconstructing the physicochemical properties of fluid inclusions and integrating their geodynamic formation processes, this approach effectively constrains hydrocarbon accumulation efficiency and heterogeneity in enrichment degrees. The homogenization temperatures of fluid inclusions cannot independently constrain hydrocarbon accumulation timing. Integrating apatite fission-track analysis, carbonate U-Pb dating, and fluid inclusion chronology are recommended to improve temporal calibration accuracy. Homogenization temperatures of fluid inclusions in deep to ultra-deep reservoirs fail to represent minimum entrapment temperatures. Application of laser Raman spectroscopy coupled with microthermometry, integrated with PVTx modeling, is recommended to precisely constrain pressure parameters and resolve ambiguities in minimum entrapment temperatures. Laser Raman spectroscopy cannot reliably quantify the organic composition of liquid hydrocarbon-bearing fluid inclusions. It is recommended to utilize Raman spectrometers equipped with UV excitation sources or 785 nm lasers to mitigate fluorescence interference in such inclusions.

China has carried out underground coal gasification projects and coalbed methane development projects, but there are problems of low economic benefits. The inclined coal seam in Xinjiang is well developed, and it has favorable geological conditions for the coordinated development of coalbed methane and underground coal gasification. Taking the Baiyanghe mining area in Fukang of Xinjiang as an example, this paper constructs the evaluation index system of geological selection for the coordinated development of coalbed methane and underground coal gasification. The evaluation of geological selection on the basis of comprehensive consideration of the main control geological conditions of coalbed methane and underground coal gasification, is also carried out. The results are as follows: 1) A comprehensive geological selection index system for coalbed methane-underground coal gasification coordinated development has been established, consisting of 9 major categories of first-level indicators and 33 sub-categories of secondary indicators, including geological conditions for coalbed methane resources, coal quality conditions, coal reservoir conditions, rock conditions, and key geological conditions for coordinated development; 2) Based on the analytic hierarchy process-CRITIC method, the evaluation weight of each index is calculated, and it is considered that the gas content, coal seam thickness and permeability are the key indexes. 3) The total area of the favorable area and the sub-favorable area for the coordinated development of coalbed methane-underground coal gasification in the study area is 4.82 km², and it is recommended to carry out engineering deployment in the western and central parts of the demonstration area and the southeastern region.

Tar-rich coal integrates the properties of coal, oil and gas. Promoting its exploration and development has important strategic value for ensuring the supply of oil and gas resources in China, and realizing the clean and efficient utilization of coal. Therefore, based on the data of tar yield, industrial components, elemental analysis and coal petrography analysis of coal samples in Tiaohu sag of Santanghu Basin, combined with logging response, a logging prediction model of tar-rich coal tar yield is established, and the tar-rich coal resources of Badaowan formation in the study area are predicted. The results show that: the yield of coal tar is positively correlated with volatile yield, hydrogen content and vitrinite content, and negatively correlated with ash yield and inertinite content. There is a good negative correlation between volatile yield, hydrogen content, vitrinite content and acoustic time difference, compensated density logging values, and a poor correlation with natural gamma logging values. In addition, the prediction model of coal tar yield based on machine learning is established. The correlation coefficient between the predicted value and the actual value is 0.92. The relative error of tar yield prediction results of 90% coal samples is less than 20%, and the relative error of 75% coal samples is less than 15%.

In-suit stress is one of the key factors determining the success or failure of coal bed methane(CBM) development. Based on the data of well tests, in-situ stress tests, and adsorbed gas content tests of multiple coal reservoirs of the A'ai Mining Area locating in the Kuqa Depression of the piedmont flexural basin southern Tianshan Mountain, stress distribution of the A'ai Mining Area and its constrains on physical properties of coal reservoir were clarified, and the constraints of tectonic evolution of flexure basin on in-situ stress of coal reservoir were discussed. The results showed: (1) The in-situ stress state types are σ_H>σ_v>σ_h, σ_H≈σ_v>σ_h and σ_v>σ_H>σ_h when the reservoir depth is 350~500 m, 500~900 m and 900~1 200 m, respectively; (2) The depth of 900 m is not only the conversion point of the vertical principal stress and the maximum horizontal principal stress, but also the transition point of permeability trend, suggesting the control effect of in-situ stress on permeability, the critical depth of adsorbed gas conversion of the A'ai Mining Area was 900~1 000 m; (3) The fractures of the shallow(buried depth<500 m) coal reservoir were compacted and closed by structural compression and thrust nappe during Himalayan period, which reduced the permeability. Influenced by the shallow thrust nappe, the NS directional compressive stress of the middle and deep(buried depth of 500~1 200 m) coals with relative higher gas capacities released partly, leading to the permeability rebound, thus the middle and deep coals were generally conducive to the development of CBM; (4) The coal reservoir stress of the Biyoulebaoguzi compound anticline in the south of the A'ai Mining Area was less than that of the Xiakuotan syncline in the middle, resulting in the permeability of former was greater than that of the latter. Hence the Biyoulebaoguzi compound anticline was relatively more conducive to the development of CBM.

Geological storage of CO₂ in depleted oil and gas reservoirs is approved due to its advantages, such as strong storage capacity, good sealing performance, and complete infrastructure. This review clarified the existing projects, advantages, significances, influencing factors, mechanisms, and storage potential evaluation procedures of CO₂ storage in depleted oil and gas reservoirs. In this review, the storage capability of depleted oil and gas reservoirs has been confirmed, and factors affecting the CO₂ storage potential, including geological factors and engineering factors, are concluded. CO₂ trapping mechanisms of different storage processes in depleted oil and gas reservoirs are elaborated and divided into three stages. The evaluation stages of CO₂ storage potential of depleted oil and gas reservoirs are summarized as basin selection evaluation stage, oil and gas reservoir selection evaluation stage, storage security evaluation using the bowtie method, and storage capacity calculation stage. The calculation accuracy of CO₂ storage capacity in depleted oil and gas reservoirs can be optimized by determining the mineralization storage volume and the actual reservoir characteristics of the dissolution storage coefficient numerically. This work intends to provide support for the storage of CO₂ by analyzing and studying the geological theory and engineering achievements of CO₂ storage in depleted oil and gas reservoirs.