Deep coalbed methane（CBM） development in East China is of great significance to ensure regional energy demand, optimize regional energy structure and realize the dual carbon goal. Based on the systematic investigation and previous works, the current situations of CBM extraction in East China were summarized, and the gas-bearing attributes and resources potential of deep CBM were analyzed. Then, the applicability of existing deep CBM exploration and development technologies in East China was discussed, and the potential favorable areas of deep CBM exploration and development in East China were discussed and predicted. Finally, the advantages and challenges of deep CBM exploration and development in East China are put forward. Previous results show that: East China has a good CBM development accumulation on the tectonically deformed coal and in the coal mine area, such as “Huainan CBM extraction model” and horizontal well staged fracturing in the roof of the tectonically deformed coal. Deep coal in East China has a high gas content（greater than10 cm³/g） and gas-bearing saturation（greater than 80 %）. The predicted geological resources of deep CBM are 8 984.69×10⁸ m³ in the Huannan-Huanbei mining area, suggesting that Huainan and Huaibei coal field has an attractive deep CBM resources potential. Horizontal well development and hydraulic fracturing techniques for deep CBM have great application prospects in East China. Panxie mine area in Huainan coal field is expected to be a pilot area for deep CBM exploration and development in these areas. However, the overall exploration and development degree of deep CBM is low, so it is necessary to carry out the more detailed resource evaluation and analysis of deep CBM geological accumulation in the type area, like deep Panxie coal mine in Huainan coal field.

In order to solve the problem of frequent well laying in the coalbed methane field in south Yanchuan due to sand production（pulverized coal）, a novel drainage pump in south Yanchuan coalbed methane well has been developed. The novel drainage pump is designed as a forced pull rod hemisphere-type seal, and the plunger assembly adopts a hollow design. The pump diameter is ø38 mm, the stroke is three meters, the stroke time ranges from one to three times per minute, and the displacement is 4.8~14.6 m³/d. The novel drainage pump is used together with hollow rod and tubing, forming a dual-channel integrated pipe string for production and cleaning. It can not only meet the normal drainage gas production, but also facilitates well flushing and discharging pulverized coal. In addition, the flushing fluid does not enter the stratum during well flushing, avoiding the pollution of the flushing fluid to the stratum and preventing the failure of the fixed valve and the pump from being stuck caused by the deposition of pulverized coal or sand in the coalbed methane field drainage well. In 2022, the novel drainage pump was applied in two wells in the south Yanchuan coalbed methane field, and since then, no fixed valve failure or pulverized coal card pump has occurred. As a result the average pump inspection period of measure wells has been extended by 285 days. Field tests demonstrate that the novel drainage pump has the dual functions of normal gas drainage and coal powder discharge through well flushing, providing a new technical support for improving the overall development level of coalbed methane field in south Yanchuan.

The fracture network developed in coal rock serves as the primary channel for gas migration, significantly influencing the seepage capacity of coal reservoir. The geometric characteristics of fracture plays a crucial role on determining the flow characteristics of coal-bed methane. To study this, a two-dimensional fracture network model of coal rock was established using COMSOL Multiphysics simulation software, focusing on the coal samples of Baode block as the research subject. The effects of fracture length, density, opening degree and angle on production were investigated, providing valuable theoretical guidance for enhancing coal-bed methane production. The results indicate that fracture length, density, and opening degree have a positive correlation with the seepage capacity of coal rock, while the angle with the flow direction negatively impacts it. However, with the increase of length, density and opening degree, the improvement in flow rate slows down, and the effect of increasing single factor to improve coal-bed methane mining can be neglected, making it difficult to control the cost-benefit ratio. Among the factors influencing outlet, angle and density exert a more significant effect than length and opening degree. Considering the surface directional well plus the high pressure hydraulic cutting method, we can enhance the efficiency of coalbed methane development. This approach connects the natural fracture system using directional borehole and hydraulic slot, fully utilizing the permeability advantage of parallel surface cutting direction. The high-pressure hydraulic cutting process induces cracks in the coal seam, increasing the number and connectivity of diversion channels, thereby bolstering the production of coal-bed methane.

Coal-bed methane reservoirs are characterized by low porosity, low permeability and low pressure, making their industrial exploitation primarily reliant on techniques like hydraulic fracturing. Currently, more than 50 percent of the gas wells in the Shizhuang block in the Qinshui Basin currently produce less than 500 m³/d of coal bed methane. However, the increase in production after gas well retrofitting has not been ideal and the main factors affecting gas well productivity remain unclear, directly impacting the overall improvement. To address this, the degree of influence of geological and engineering factors on fracturing productivity in coal-bed gas wells is described using the gray correlation method, and the main factors controlling gas well productivity after fracturing are analyzed. A correlation mathematical model between the main control factors and gas well production is established using the Pearson correlation analysis method to predict gas well productivity. The reliability of the prediction model is verified through gas well data validation. Furthermore, a classification decision tree is established using the chi-square automatic interactive detection decision tree method, in conjunction with gas well productivity data, to understand the impact of geological and engineering factors on gas well productivity in fractured wells. Under high gas content conditions, engineering factors have a relatively small impact on the productivity improvement of gas wells. However, as the gas content decreases, the impact of different engineering factors on the gas well productivity gradually increases, which helps optimize the main design parameters such as displacement, sand volume, and total liquid volume, enriching the evaluation methods for post fracturing productivity of coal seam pressure.

The issue of coal fine production is increasingly prominent in the development of coal-bed methane. Implementing appropriate measures to control the migration and production of coal fines is crucial for achieving stable and high production of coal-bed methane wells. However, the characteristics of coal migration and production in the coal seams of Baode block remain unclear, which hinders the efficient development of coal-bed methane in some wells in this area. To address the problem of coal fine production in coal-bed methane development, core flooding experiments were conducted to investigate the migration and production characteristics of coal fines concerning influencing factors such as formation water velocity, salinity, gas-water ratio, effective stress, etc. The experimental results revealed that during the drainage stage, the amount of coal fines produced at low formation water flow is minimal, with coal fines moving within fractures and accumulating at the outlet, forming a coal powder filter cake. However, when formation water flow surpasses the critical flow, a significant amount of coal fines is produced. A substantial pressure fluctuation can flush out the coal fines obstructing the outlet. Furthermore, the salinity of the formation water plays a role in carrying coal powder, with higher salinity increasing its transport capacity. While single gas phase flow is not effective in displacing the coal fine migration and production, two-phase flow with a gas-water ratio of 50∶50 exhibits a stronger ability to carry coal powder. The concentration of coal fine in the produced liquid continued to decline with the increase of the effective stress loaded on the coal, Similarly, the holding pressure at the outlet follows a downward trend, but the displacement pressure difference increases. The research findings provide essential data and a theoretical basis for implementing on-site prevention and control of coal fine production.

The exploration and development of shale gas in Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation in Nanchuan and its adjacent blocks have yielded fruitful results. However, it is crucial to pay closer attention to the comprehensive use of fluid characteristics for analyzing the differences in shale gas preservation conditions in each block. Research findings reveal the following key points: ① With the prolongation of recovery time, the mineralization degree of the produced water gradually increases, exhibiting notable differences from fracturing fluid. This suggests the presence of the presence of movable CaCl₂-rich formation water in shale layer, characterized by a mineralization degree exceeding 50 g/L; ② Enriched and high-yield wells exhibit low water production, low mineralization and rich in NaHCO₃, which are indicative of condensate water; ③ Under different preservation conditions, the deuterium oxygen isotopes of the produced water vary with time. The high pressure stable block in the basin gradually deviates from the atmospheric precipitation line, while the normal（low） pressure complex block outside the basin remains close to the atmospheric precipitation line; ④ From the inside to the outside of the basin and from deep to shallow, the homogenization temperature of fluid inclusions in shale fracture filled calcite veins gradually decreases（from 240 ℃ to 90 ℃）. Simultaneously, the metamorphism coefficient of the inclusions also gradually increases, reflecting the degree of differential damage of shale gas preservation conditions.

Considering complex shape and non-uniform distribution of fracturing fractures in shale reservoir, on the basis of multiple migration mechanisms a unified apparent permeability model is developed, incorporating two types of pore apparent permeability based on multiple migration mechanisms. This model serves as the foundation for establishing a gas reservoir-fracture-wellbore coupled seepage model, utilizing real space source function theory and pressure drawdown superposition principle. Through simulations and analyses, the study investigates the effects of micro seepage, fracture shape and non-uniform distribution of fractures on shale gas productivity. The demonstrate that micro seepage significantly impacts shale gas well production, with daily gas production being 20.3 % higher when considering micro seepage during the initial stage compared to neglecting it. Furthermore, the productivity of wells with complex fractures is lower than that of wells with ideal rectangular fractures, and star-shaped fractures exhibit the lowest productivity. The non-uniform distribution of fractures also affects the productivity of horizontal wells, and an optimal fracture layout is identified. The model takes into account both the micro seepage mechanism and actual fracturing fracture of shale gas, providing valuable guidance for the productivity research of fractured horizontal wells in shale gas reservoir.

Traditional methods for predicting shale gas well production often struggle to effectively analyze the complex relationship between reservoir parameters, fracturing parameters and production. To address these challenges, a novel approach is introduced, involving the construction of characteristic parameters based on physical meaning and random combination. The small batch gradient descent method（MBGD） is adopted as the training function to develop an improved artificial neural network prediction model for shale gas well production. An example is utilized to demonstrate the effectiveness of the improved artificial neural network model in predicting shale gas well production. The model’s performance is evaluated using the mean squared error（MSE） and the modified determination coefficient（T）. The results indicate that the predictions from the improved network model align well with the actual production data. Moreover, the model exhibits superior prediction accuracy and stability compared to the traditional BP（error backpropagation algorithm） neural network model. With its high accuracy and reliability, the proposed model can provide valuable support for fracturing optimization design and productivity evaluation in shale gas reservoirs.

In southern Sichuan, thousands of shale gas wells have been drilled, generating a vast amount of high-dimensional data during geological evaluation, drilling, and production processes. Predicting reserve recovery ratios through data exploration and analysis is essential for guiding the exploration and development of shale gas resources. To achieve this goal, a novel approach is introduced, which couples principal component analysis（PCA） and orthogonal partial least square（OPLS） analysis, enabling rapid and accurate prediction of reserve production degree. The new method is put to the test using Zhaotong shale gas well samples to evaluate its effectiveness in predicting reserve recovery ratios. The results show that the average accuracy of reserve recovery ratio prediction using PCA-OPLS method surpasses the anticipated result, that this algorithm can swiftly and precisely predict recovery ratios. With its advantages of simplicity, high accuracy, and promising application prospects, this method holds great potential for efficiently evaluating the production and recovery ratios of shale gas reserves.

CO₂ storage in saline aquifers is one of the feasible technical deployment schemes, and it is also the main approach to reduce CO₂ emission in the medium and long term. To meet the assessment requirements of the storage potential in saline aquifers, four CO₂ geological storage mechanisms are systematically expounded. Based on the storage mechanism, an evaluation index system for the suitability of CO₂ geological storage in saline aquifers is established, including four evaluation index layers of safety, technology, economy, and social environment. The weight of each evaluation index factor is calculated using the analytic hierarchy process. For saline aquifers with an open structure and rich hydrogeology, it is recommended to consider the combination of residual trapping and solubility trapping to evaluate CO₂ storage potential. The CO₂ geological storage suitability evaluation index system of saline aquifers provides a reference for conducting the national CO₂ storage suitability evaluation.

The study of formation conditions and accumulation mode of biogenetic mudstone gas reservoir in Sanhu Depression is essential for understanding the accumulation mechanisms and enrichment rules of such gas reservoirs. It holds significant theoretical and practical implications for guiding the exploration and development of Quaternary mudstone gas reservoirs. This research focuses on the Quaternary mudstone in the Sanhu Depression as the main subject. To determine the reservoir formation conditions and establish the accumulation mode, various experiments were conducted, including soluble organic carbon analysis, porosity determination, and chromatography-mass spectrometry analysis. The results reveal that the presence of high levels of soluble organic carbon and herbaceous humic organic matter, along with cold and dry conditions, create favorable conditions for the generation of biogenetic mudstone gas. The Quaternary formation in Sanhu Depression has the characteristics of high porosity and low permeability with numerous micro-nano pores that provide ample space for the occurrence of biogenetic gas. Gas flow primarily occurs through Fick diffusion and slip flow. The self-sealing effect of mudstone leads to the in-situ accumulation of biogenetic gas. However, during the late Himalayan tectonic movement, the gas containment of mudstone is disrupted. As a result of buoyancy, the gas migrates upward and accumulates in high parts of the mudstone, which are adjacent to the gas-generating center, and are superimposed longitudinally with sandstone biogenetic gas reservoirs.

The accurate calculation of the water holdup and the inversion of fluid distribution for multi-phase flow play a crucial role in understanding the development performance in horizontal wells. This study builds upon the array electromagnetic wave holdup instrument and proposes a novel method for calculating water holdup. The method is based on the weight of the mid-point tangential area of the probe's radial projection. Additionally, inversion methods for oil-water phase distribution in horizontal wells, considering high, middle, and low water content, were developed by comparing them with existing quantitative calculation methods of the array holdup instrument. The results demonstrated that the new method exhibited an average absolute error of 4.43 % and relative errors of 16.34 %. These values were significantly better than those obtained using the weight coefficient method and the radial contour area method. For the inversion of fluid distribution in horizontal wells with high, middle, and low water cut conditions, the Gaussian Radial Basis method and multivariate linear method provided the best matches. This research lays a solid foundation for evaluating the production performance of multi-phase flow in horizontal wells.

Currently, the large-displacement slickwater fracturing process has become the primary method for developing unconventional oil and gas resource. However, the efficiency of this process is limited by the sand carrying capacity of slickwater, which results in rapid settlement and short migration distance of the proppant within the fractures, leading to a need for further improvement in the reservoir transformation effect. To address this issue, a water-soluble material is applied to coat the surface of the self-suspending proppant, enhancing its suspension effect in slickwater or clear water and thereby increasing the crack support volume. The self-suspending proppant meets the required technical standards, showing a total suspension time of less than 40 seconds in tap water at a 20 % sand ratio, and maintaining stable suspension for over two hours at 90 ℃ even during thorough mixing. In a practical on-site test at Mahu sandstone reservoir in Xinjiang Oilfield, continuous sand carrying was achieved using clean water, reaching a maximum sand concentration of 480 kg/m3 while maintaining stable construction pressure. The successful application of self-suspending proppant clear water fracturing technology in Xinjiang oilfield serves as a valuable reference for the selection of oil and gas resource technology in the future stage.

The adjustment of the flow field proves to be an effective way for enhancing the recovery of remaining oil during the high water cut development stage in a water-flooding oilfield. As the water flooding oilfield enters the high water cut development stage, a dominant flow field gradually forms between oil and water wells, resulting in the ineffective circulation of injected water. As a result, the effect of reservoir development is reduced. To address this issue, a flow field adjustment model is established based on standard determinant well pattern arrangement using Python programming language, guided by the working principle of flow field adjustment. In this model, the flow field streamlines transition angles are 27°, and 45° respectively. The finite difference method is employed to simulate the dominant flow field range before and after the adjustment. The results demonstrate that the nine-spot method and the five-spot method could enhance the oil displacement efficiency, while the flooding efficiency of the M-shaped well-mesh is relatively low. Moreover, the 45°-streamline transition proves to be particularly beneficial for oil exploitation during the high water cut development stage in a water-flooding oilfield. The study holds significant guiding significance for adjusting the well pattern and enhancing the recovery efficiency, thereby facilitating the extraction of remaining oil in the high water cut development stage.

Lithofacies analysis serves as the foundation for reservoir evaluation. However, due to the limited coring quantity and cost constraints, identifying lithofacies using logging data for uncored wells becomes crucial. In the Longdong area of the Ordos Basin, the lithofacies of the Chang-7 member have been classified into six types dependent on core identification results and imaging logging data. Based on core calibration, the logging response characteristics of different lithofacies were summarized, leading to the establishment of the lithofacies recognition mode using conventional logging curve. To achieve automatic lithofacies recognition in the study area, machine learning algorithms were employed. The traditional classification algorithms were affected significantly by the unbalanced sample. After comparing the application effects of different unbalanced data classification algorithm in the region, it’s found that bagging algorithm of ensemble learning notably improved the classification performance of all lithofacies by combining multiple classifiers. As a result, the overall lithofacies identification precision of this region has been improved by 20 %. According to the regional application results, the identification accuracy of single well can reach 84.33 %, demonstrating its practical applicability and effectiveness.