The spacing between CO2 injection wells and CH4 production wells significantly influences the effectiveness of CO2-enhanced coal bed methane (ECBM) technology. Based on the theory of porous elasticity and seepage mechanics, a hydromechanical coupling model of CO2-ECBM was established, and the process of CO2-ECBM was simulated under varying CO2 injection pressures and well spacings, and the rules of CH4 production and CO2 storage under different well spacings were clarified. By constructing an objective function for evaluating the effect of CO2-ECBM project, the optimal well spacing corresponding to the four types of engineering targets under different injection pressures was obtained. The results show that reducing the well spacing can effectively enhance the effect of CH4 production and CO2 storage, but the enhancement effect weakens as the spacing is reduced, and the enhancement effect decreases or even disappears when the well spacing is less than 180 m. The optimal spacing for the four types of engineering targets increases with increasing injection pressure. Compared with the other three targets, although the engineering time under the time-saving and efficiency-enhancing target is significantly shorter, its corresponding CH4 production and CO2 storage effectiveness are markedly inferior. Therefore, it is believed that time saving and efficiency enhancing should not be regarded as a primary target in practical engineering. Finally, differentiated design strategies for CO2 injection pressure and well spacing are proposed under various engineering objectives, providing theoretical support for determining appropriate CO2 pressure and well spacing in the field.

Lithology identification assumes an absolutely crucial role in the realm of reservoir delineation, functioning as a fundamental prerequisite for accurately determining porosity, oil saturation, and sundry other parameters. The precise identification of lithology effectively forms a foundation for ensuring the effective exploration and development of oil and gas fields in the subsequent stages. Traditional logging lithology identification methods have many limitations, and therefore many challenges. Therefore rapid and accurate lithology identification is a matter of significant concern and importance. This study identified the initial lithology using a cross-plot approach, capitalizing on the distinctive characteristics of the lithology logging response. Subsequently, a rapid lithology identification method was developed for marine carbonate rocks by integrating artificial neural networks and the logging curves. To evaluate its accuracy and precision, the outcomes were compared with the core data and the lithology scanning logging techniques. The neural network–based method proposed in this paper can enable swift and accurate identification of lithologies, encompassing even transitional lithologies such as silty limestone and limy dolomite. Therefore, it provides novel theoretical and technical support that is of tremendous significance for subsequent research and applications.

In COP28, it is understood that the global nuclear energy capacity will be tripled by 2050, supported by more than 20 countries. Related to this, Indonesia also wants to get a net zero emission by at least 2060. In line with the increasing interest in the small modular reactor (SMR), this study is performed to compare several sites in Indonesia to determine the most feasible site for SMR deployment using the Reactor Technology Assessment (RTA) developed by the International Atomic Energy Agency (IAEA). Traditionally used for reactor selection, in this study, the RTA will be used for the site selection when the reactor type has been decided. The sites used for this study are Talisayan, Ujung Lemah Abang, Gelasa Island, and Ngali Island. These sites are chosen based on studies on interest areas for NPP deployment carried out by governmental and public institutions. The SMRs used are BWRX-300, NuScale, and UK SMR due to their variety of designs. From the study, it is found that the most feasible site for BWRX-300 and UK SMR is the ULA site followed by Talisayan and ULA sites for NuScale.

Gas production and pressure from shale gas wells are highest early in the extraction process and decay rapidly over time. Skid-mounted compression equipment (SCE) in the shale gas gathering and transportation system (SGTS) can adapt to production changes in gas wells and can be deployed flexibly, improving equipment utilization. This paper examines the effects of node pressure and equipment type on the deployment scheme of SCE. Using a specific shale gas field production block as a case study, this paper proposes a method for multicycle operation and pressurizing deployment optimization in the SGTS, establishing a mixed-integer nonlinear programming (MINLP) model. Solving this optimization model yields the optimal deployment scheme of SCE at different times, the number of compression equipment, and the equipment utilization rate. The results show that in shale gas field production, SCE can be deployed flexibly, and most equipment utilization rates are above 0.8, with a maximum of 0.99. This not only achieves efficient use of equipment but also reduces the purchase cost, fully reflecting the importance of SCE in the SGTS. A sensitivity analysis was conducted to consider the impact of different costs and type combinations of SCE on the total production cost, and the results showed that the total cost of eight types was 6.28% lower than that of two types of booster equipment combinations.

The demand for electricity is increasing tremendously globally with the development of countries. To fulfill the supply of electricity, many countries have already adopted renewable energy sources. The production of electricity from hydraulic energy sources is one of the oldest methods. The axial flow water turbine can efficiently generate energy from the water flow with a very low head. The current investigation is focused on enhancing the performance of the axial turbine by providing an enclosure around the rotor. The initial experiments were carried out with only the upstream enclosure. The optimized upstream enclosure was taken with different lengths of downstream enclosure for further investigations. The current investigation concluded that the maximum efficiency using only an upstream enclosure is 89.48%, which is around 3.20% higher compared with the bare turbine. The optimum efficiency was found at upstream-side length ratio (ULR)=0.46 (upstream enclosure length LU=40 mm). With using the optimum ULR=0.46, the maximum efficiency for the downstream enclosure was found at downstream-side length ratio (DLR)=0.23 (downstream enclosure length LD=20 mm). The highest efficiency value for this axial runner was obtained at 90.89%, which is 4.83% higher compared with the bare turbine.

본 연구는 액화석유가스 (LPG, liquefied petroleum gas)가 산업용 도시가스의 대체 연로로서 역할을 수행할 수 있는지 여부를 검증하고, LPG가 특정 시황에서 발전용 천연가스를 대체할 때의 경제적 효과를 분석한다. 최소자승법을 활용한 단순 회귀분석 시행 결과, 산업용 도시가스 가격과 LPG 수요 간에는 통계적으로 유의미한 상관관계가 있는 것으로 나타났다. 또한 과거 액화천연가스(LNG, liquefied natural gas)의 현물가격이 급격히 상승한 시장 상황에서 LNG와 LPG의 국내 수입 가격을 비교하고, LNG 대신 LPG를 공급하였을 때 발생했을 무역수지 개선 효과를 산출하였으며, 국내 유통되는 천연가스 가격 안정화에 따른 경제적 효과를 검증하였다.

The horizontal ground heat exchanger has been extensively employed to collect geothermal energy from mine backfill bodies. A novel method for avoiding thermal interference using the thermal influencing radius coupling pipe spacing was investigated. Thermal interference between adjacent heat-transfer pipes can be neglected when D40°C=2R40°C is used as the pipe spacing. The comprehensive impacts of heat-transfer fluid and backfill body on the heat-transfer efficiency and thermal influencing radius of the horizontal single pipe were investigated. The growth ratio of heat-transfer capacity can be as high as 227.3% when thermal conductivity increases from 0.5 kJ/(kg·°C) to 2 kJ/(kg·°C). The heat-transfer capacity increases by 4% for every 1°C reduction in inlet temperature. The thermal influencing radius is significantly influenced by specific heat capacity and thermal conductivity. This study can provide theoretical recommendations for the design and improvement of heat-transfer pipes in the backfill body.

The results of experimental studies of the cocombustion of coal–water fuel with fuel oil are presented. According to the results of experimental studies, the efficiency of joint ignition of stationary single droplets of coal–water fuel and fuel oil was substantiated. A decrease in the ignition delay times of fuel droplets was found in comparison with the ignition of only coal–water fuel droplets under identical conditions. A significant decrease in the ignition delay times of coal–water fuel droplets is typical for droplets with sizes of 2 and 3 mm in the entire studied temperature range of the oxidizer (from 873 to 1,273 K) and distances (from 2 to 4 mm) between drops of coal–water fuel and fuel oil. It has been experimentally established that the reduction of ignition delay times is 58 and 70%. For droplets of coal–water fuel with a characteristic size of 1 mm, the changes in ignition delay times are ambiguous. The joint combustion of coal–water fuel and fuel oil affects the ignition of droplets of coal–water fuel, and the characteristic size of which is more than 1 mm. With this method of burning coal–water fuel and fuel oil, the latter acts as a catalyst when igniting coal–water fuel, thereby ensuring a stable combustion of such fuel. The combustion of two-component coal–water fuel together with fuel oil can avoid the problems typical of such fuels: reduce the requirements for spraying devices, solve the problem of low reactivity, increase the completeness of combustion of this fuel, and fully use it in the production of thermal and electrical energy.

As continental shale oil is explored and developed on a larger scale, its high starting pressure gradient in the shale matrix poses challenges for flow. This paper investigates the effect of imbibition development and the mechanism of oil mobilization under high temperature and high pressure using self-developed dynamic huff-n-puff imbibition equipment based on micropore and percolation characteristics. Using six different injection fluids—slickwater, imbibition agent CY-IMNF-1, sand-carrying agent, guanidine gel breaking fluid, imbibition agent #G-1, and CO2—this study involved an experimental investigation of high-temperature and high-pressure huff-n-puff imbibition at a pressure of 30 MPa and a temperature of 110°C. The effect of injection fluids on imbibition development recovery is analyzed, and the contribution of different scale pores to the oil recovery of continental shale is quantified. It was found that slickwater huff-n-puff resulted in the highest imbibition oil recovery, followed by imbibition agent CY-IMNF-1. Shale oil production in nanopores and micropores was mainly achieved through slickwater huff-n-puff, and the pore and throat size limit for oil mobilization was found to be 4–7 nm. Based on a synergy perspective, optimizing the hybrid system of slickwater and CO2 is suggested. This study provides technical support for developing similar continental shale reservoirs with high-temperature and high-pressure huff-n-puff imbibition.

국내 발전소 등에서는 배출되는 가스 내 황산화물을 제거하기 위한 탈황공정을 운영하고 있으며 주로 고품위 석회석을 탈황용 흡수제로 활용하고 있다. 이에 본 연구는 국내 고품위 석회석을 대상으로 편광현미경을 통한 광물학적 결정구조 특성, 열량측정 장치를 활용한 수화활성도, 기공률 측정기를 활용한 기공크기 특성을 평가하였으며, 이러한 결과를 토대로 로내 탈황 반응장치를 활용한 고품위 석회석의 탈황 특성을 평가하여 활용 방안을 확보하고자 하였다. 실험결과 광물학적 특성 및 소성 후 형성되는 석회석 입자의 기공크기 및 기공면적은 수화반응 및 탈황반응의 반응속도와 전환율에 중요한 인자로 작용하는 것을 확인하였다.