Relied on labor control, most traditional methods to estimate engineering cost are featured by inferior efficiency and accuracy, and man-made discrepancy. Thus, offering efficient and precise data on both investment estimate and budget for rapid decision-making in drilling, an artificial intelligence (AI) model based on machine learning (ML) was built for cost management. A few historical data including geological conditions, drilling devices and technologies were selected from 265 drilling projects. Then, a data set containing key indexes was constructed by data pre-processing and feature extraction. Several models, for example classification and regress tree (CART), gradient boosting decision tree (GBDT), support vector regression (SVR) and eXtreme gradient boosting (XGBoost), were discussed, and their findings were also verified and compared. The XGBoost model might be served as the core one for training and optimization. A rapid cost estimation model suitable for drilling investment projects was successfully built after adjusting model parameters and feature extraction. Results show that (i) XGBoost is slightly superior to the other models in terms of total well expense and prediction accuracy; (ii) ML-based models can not only establish the relation of engineering parameters to cost but reduce the cost calculation time to a few minutes from several hours by manual manner, to further improve the estimation efficiency. In conclusion, shortage of data samples results that the model is confronted with difficulties in feature extraction and has wide confidence interval. It is necessary to expand the scope of data set and combine additional factors affecting this cost estimation to improve its generalization and accuracy.

Influenced by water invasion, most carbonate gas reservoirs with edge and bottom water, Sichuan Basin, are confronted with history-matching difficulties of water production and wellhead tubing pressure in gas producers by means of numerical simulation. Thus, a set of history-matching methods were individually developed for three modes of water-producing gas wells with relative permeability adjustment, barrier and interbed adjustment, and waterbody supplement. Results show that (i) as for determining both waterbody size and gas-water contact in reservoirs, the water breakthrough time calculated from the simulation is deviated from the real time. However, the matching is realized for certain gas producers whose water breakthrough time is not conditioned by adjusting relative permeability curve. And this matching mode is called as relative permeability adjustment; (ii) for a few wells without water in reservoirs but with water in their neighboring wells, the matching is implemented by adding barrier and interbed. This matching mode is named as barrier and interbed adjustment; and (iii) for those wells without waterbody in reservoirs but water production generally over 10 cubic meters per ten thousand cubic meters of gas production in the actual production, the matching is realized by supplementing waterbody. And water bulk is confirmed by the way of material balance. This matching mode is known as waterbody supplement. In conclusion, these three history-matching methods for water-producing gas wells present remarkable effect after their application to Changxing carbonate gas reservoirs with edge and bottom water in Yuanba gasfield.

To thoroughly liberalize price of gas source serves as the ultimate destination in natural-gas price reforms. Thus, focusing on market-oriented reforms on natural-gas gate price, we analyzed existing problems in gate price mechanisms and pointed out next development needs so as to work on a new national unitary market and optimize efficient resource allocation. Moreover, both goal and direction were discussed for the next round of market-oriented reforms on natural gas. Results show that (i) after the comparison on two schemes of livelihood gas consumption assurance during transitional period of reforms and after price integration, it is recommended to implement one scheme of "maintaining regulated gas supply+monetary subsidy" during transitional period while the other of "stepwise pricing+gas coupon" after integration, being supplemented by moderate price adjustment fund in order to solve key problems, for instance, different pricing between upstream gas source and end users, livelihood gas consumption assurance, and price integration of regulated with unregulated gas; (ii) through the analysis on this integration's concept and strategy, it is suggested to establish a new pricing mechanism to further directly achieve the price integration; (iii) both thinking and specific pathway to price reforms have been raised to promote natural gas in quality development; and (iv) some suggestions are made to deepen these reforms step by step, perfect the people's livelihood system, and impose greater transparency and much stricter regulation on this market.

The capability of diagnosing the faults of natural gas compressor units under complex working conditions needs to be enhanced. In this paper, the traditional diagnosis techniques are investigated for their deficiencies in processing multi-source heterogeneous data, semantic understanding and real-time response, and their limitations in terms of accuracy, interpretability and real-time performance are revealed. Then, a multimodal knowledge graph-based question-answering (MMKG-QA) model is proposed, which integrates multiple data types such as text, images and timing signals and uses natural language processing and computer vision technologies to extract deep features. On this basis, a multimodal knowledge graph integrating expertise and industry standards is constructed to structurally express the semantic relationships among fault mechanisms, key components and operating parameters. The model achieves knowledge representation and reasoning through graph neural networks, supporting the understanding of complex semantics and question answering. The following results are obtained. First, the proposed model yields significantly improved accuracy of fault identification compared with traditional methods, and it is stably performed especially in multi-factor coupling scenarios. Second, the QA system is capable of fast response and real-time diagnosis. It is concluded that (1) multimodal data fusion and knowledge graph construction can effectively enhance the expression and recognition of fault features of compressor units; and (2) the intelligent QA mechanism combined with graph neural networks is conducive to enhancing the semantic reasoning and intelligent diagnosis capability of the system.

Both natural gas and liquefied natural gas (LNG) in the Guangxi Zhuang Autonomous Region were surveyed in an effort to optimize natural-gas resource allocation and LNG layout. Moreover, some layout suggestions on these two were made. Results show that (i) in this autonomous region, the consumption of natural gas will be concentrated around residential gas and transportation sectors in the future. And that of industrial fuel will reveal some growth, but the increase is slowly; (ii) in terms of five major gas use in urban gas, transportation, power generation, and industrial fuel, both LNG demand and transportation will become a big concern which may make up gas consumption areas that cannot be transported by pipelines; and (iii) considered LNG infrastructure in Guangxi and LNG layout of refueling stations in counties and cities and coastal terminals, the operation cost, investment scale and economic radius of logistics were analyzed by adopting LNG transportation modes and cost analysis methods. In conclusion, Guangxi's natural-gas utilization among all sorts of energy will hold a relatively advantageous growth in the future, especially with a great prospect in transportation. Optimizing LNG utilization and infrastructure layout should be of utmost importance. It is advisable to construct new LNG processing and supply bases in Baise, Guilin and Wuzhou cities where its infrastructure projects in coordination with natural-gas pipelines and coastal LNG terminals will be conducive to constructing an efficient LNG supply-demand framework around these three cities.

Taken C2 well in Chaganhua North subsag, Changling fault depression, Songliao Basin, as an example, two well tests on pressure buildup were conducted in an effort to figure out dynamic response features and productivity variations in volcanic gas reservoirs at the process of their development. Then, the wellbore flow regime, buildup characteristics, and dynamic evolution of physical parameters were made clear for the reservoirs by combining flow pressure and temperature testing, bottomhole static pressure and temperature gradient testing, and transient well-testing analysis. Results show that (i) the formation pressure in this well decreases to 25.39 MPa from initial 68.49 MPa as production time continues, meaning reservoir energy in sharp decline; (ii) the effective reservoir permeability drops from 0.0122 mD to 0.0062 mD, the fracture half-length from 35.2 m to 23.4 m, and the detection radius from 63.4 m to 26.8 m, respectively, representing so weak seepage behaviors near wellbore; and (iii) synchronously, two productivity indexes decline, such as one index of gas productivity index from 3,980.02 m³·d^-1·MPa^-1 to 1,320.29 m³·d^-1·MPa^-1 and the other of liquid productivity from 0.9016 m³·d^-1·MPa^-1 to 0.4156 m³·d^-1·MPa^-1, implying that the overall development effect gets worse. In conclusion, dynamic features in the volcanic gas reservoirs are dominantly under the joint influence of reservoir-stress sensitivity effect and production system. The tight volcanic reservoirs with high pressure undergo an increase in their effective stress during production, leading to fracture closure and permeability loss. What's more, optimizing production system and controlling pressure drop may be regarded as essential measures to maintain fracture conductivity or delay productivity drop.

Taken 3D geological modeling on gas reservoirs of the fourth member in Leikoupo 4 Formation (hereinafter referred to as Leikoupo 4 Member), Xinchang block, western Sichuan Basin, as an example, both difficulties and solutions were analyzed and addressed on the basis of well- and mud-logging, and seismic data, as well as basic geological characteristics in an effort to achieve these reservoirs in the efficient and rational development. Ideas and methods were determined for the modeling on carbonate gas reservoirs of tidal flat facies. Additionally, in accordance with objective geological conditions, a 3D fine model was also established. Results show that (i) developed with multi-level faults, the top of Leikoupo Formation in this block has suffered from erosion and pinchout. Guided by theories of structural geology and sequence stratigraphy, fault and bedding plane models from coarse to fine has been created by the VBM algorithm of structural framework modeling; (ii) micrite- to powder-crystalline dolomite, algae bound dolomite and calcareous dolomite are regarded as favorable reservoir lithofacies. Data volume of lithofacies, and reservoir facies and porosity inversion is optimized for hierarchical constraints. And a model of matrix porosity is built for the reservoirs by means of the sequential Gaussian random simulation which can effectively depict attribute variations between thin reservoirs and interbeds; and (iii) another model of discrete fracture network (DNF) is adopted, simulation algorithms are selected to construct small-, medium-, and large-scale fracture sheet models, and the diadochic assignment algorithm is adopted to integrate each fracture model and to set up a complete 3D fracture grid model. In conclusion, the modeling ideas and methods of "multi-level sequence + VBM algorithm controlling framework, origin + multi-attribute constraints conditioning attributes, and multi-scale DNF model integrating fracture models" can resolve difficulties in accurately describing heterogeneity and characterizing seepage behaviors in fractured-porous reservoirs, especially in the modeling on carbonate gas reservoirs of tidal flat facies, further to improve the accuracy in geological models.

The "Daqing-scale gas province in southwestern China" is the first "Gas Daqing" project constructed in this country after entering a new development stage. Therefore, four sorts of value dimension in economy, safety, society and culture were discussed for the project in an effort to fully appreciate both strategic value and implementation, and some strategies were also made. Results show that (i) from the aspect of economic value, this construction can not only create considerable benefits and wealth but promote industrial upgrading and high-quality development in Sichuan and Chongqing areas; (ii) the "Gas Daqing" project is able to guarantee smooth domestic natural-gas supply in the view of safety value, and lay a solid foundation in the energy's economic domain; (iii) for the society, this construction project supports the social development and high-level technological self-reliance and self-improvement in both areas, and assists in achieving of the dual-carbon goal (including carbon peak and carbon neutrality); (iv) from the standpoint of cultural value, this project makes the contemporary meaning of both Daqing Spirit and Iron Man Spirit more colorful to advance natural-gas cultural brand communications; and (v) it is essential to forge a "special zone" for natural-gas strategic expansion, build the whole gas markets in China with Sichuan as its hinterland, and put the effort on the "Gas Daqing" construction.

For new energy resources, their industrial development was discussed in order to scientifically assess the value of new energy enterprises to make investment decision. In addition, taken an acquisition case of Georgian KG Company as an example, a new valuation method based on discounted cash flow (DCF) and Black-Scholes (B-S) models was put forward and verified. Results show that (i) such enterprises feature long cycle, high risk and rapid growth, so their value may be underestimated by using a single traditional valuation way, while both DCF and B-S models may reflect the profitability and potential growth opportunities in existing assets more thoroughly; (ii) DCF model is employed to calculate the future discounted cash flow of existing power generation assets, while B-S model to quantify the option value brought by uncertainties from policy, technology and market; and (iii) both volatility and risk-free interest rate are the main valuation parameters requiring sufficient support from market data, and multi-stage investment projects should be assessed with the multi-stage compound B-S model to improve the valuation accuracy. In conclusion, the application of B-S model depends on some theoretical assumptions. What's more, the acquisition of overseas assets by Chinese capital is developing rapidly, but the market features lower maturity, as well as both merger and acquisition samples are very few. So it is essential to further investigate international finance and capital markets. Multi-stage compound of real options should be required for those enterprises involving multi-stage investment, but the valuation becomes increasingly difficult.

At present, global energy transition is in full swing. And China's petroleum industry is confronted with challenges in low-carbon development under the dual-carbon goal. The relation of energy transition to the dual-carbon goal is inclusive not parallel (dual carbon is a part of the transition). Therefore, adopting the policy analysis, technology assessment and dynamic market diagnosis, we discussed synergistic mechanisms on the integrated development of both petroleum and new energy resources and practical development pathway so as to balance contradictions between energy security guarantee and new energy scale substitution. Results show that (i) policy synergy is an essential driving force for this integrated development. Low-carbon transformation is push forward for oil and gasfields through such mechanisms as green-power substitution and multi-energy complementary; (ii) technological innovation greatly raises the efficiency of resources utilization, like carbon capture, utilization and storage (CCUS) technologies to reduce the carbon-emission intensity in traditional industry, as well as hydrogen storage and transportation and photovoltaic hydrogen to accelerate the clean-energy replacement; and (iii) market competition presents a dual-track parallel pattern of both stock optimization and incremental substitution. All projects on wind, power, gas and hydrogen storage are dominated by state-owned oil and gas enterprises. Nevertheless, both technical and economic shortage together with competition in homogeneous market may constraint on the in-depth development. In conclusion, it is essential to break down barriers through cross-industrial synergistic mechanisms, green-card trading and key technological breakthrough, and to promote the transformation of petroleum industry from a "main supplier" to a "system synergist" in an effort to realize the double goals of "maintaining supply" and "reducing carbon emission" on the basis of energy security assurance, and provide Chinese plans for global energy system in the green and low-carbon development.

Taken gas reservoirs of the first member in the Middle Permian Shihezi Formation (Shihezi 1 Member), Xinzhao block, Dongsheng gasfield, as examples, geological and engineering parameters, characteristics of induced fractures with single factor, and fracture monitoring data were analyzed for different reservoirs in an effort to figure out characters of induced fractures from horizontal-well fracturing in tight sandstone reservoirs with high heterogeneity. And with various fracturing scale, the induced fractures in Shihezi 1 reservoirs were analyzed. Results show that (i) the better the physical properties are in Shihezi 1 reservoirs, the lower the Poisson's ratio, Young's modulus and in-situ stress, and the higher the brittleness index; (ii) given the same fracturing parameters, such fractures possess following characters: the lower the fractures and the smaller the fracture half-length for the better physical properties, the higher the fractures and the smaller the fracture half-length for the thicker reservoirs, and the lower the fractures and the larger the fracture half-length for the larger the stress difference between reservoir and interlayer; (iii) under the same geological conditions, the higher the injection flow rate is and the greater the net liquid volume injected is, the larger the fracture height, the larger the fracture half-length, and the larger the fracturing extent. Moreover, the larger the number of perforation cluster is, the greater the spread width of fracture and the smaller the fracture half-length under the same geological and fracturing parameters; and (iv) the net liquid volume is the main influential factor to expand fracturing extent in tight sandstone gas reservoirs with high heterogeneity. It is concluded that the induced fractures in such reservoirs are jointly affected by geological and engineering factors. Depending on reservoir properties at one fracturing site, the designed fracturing parameters should be differential so as to attain the expected fracture half-length and height.

Main hydrogen production technologies are increasingly grown up. Hydrogen economy will rely on hydrogen transportation and distribution with low cost in the coming years. Carbon steel pipelines with high pressure can achieve long-distance and large-scale transportation despite of many problems in this transportation, such as fragile, high flow rate, easy leakage and high consumption of compressional energy. Compared to other transportation modes, it still reduces transportation cost. Thus, taken long-distance hydrogen pipelines as examples, a levelized cost model was built to discuss their technical characteristics, construction investment and operation costs. In this model, the pipeline system was simplified as lines and stations for calculating both construction investment and operation cost. And the investment and cost were subdivided and computed by using the relational expression of HDSAM model. In addition, the levelized cost was calculated after dividing annualized cost by mass flow rate, and this model was compared with other transportation modes. Results show that (i) the levelized cost is 2.44 CNY/kg H2 for the DN900 long-distance hydrogen pipelines with 500-km long; and (ii) compared to other transportation modes, the long-distance hydrogen pipelines boast greatly lower transportation cost and achieve more remarkable benefits. In conclusion, this cost model can quickly estimate both investment expense and levelized cost to provide basis for economic evaluation, facilitate the impact of pipeline length, diameter and throughput, and assist in making investment decisions in early engineering projects. This model is also applicable to long-distance pipelines of other media.

In this study, we employed SWOT method to deeply probe into the hydrogen energy industrial development in Chongqing city from four aspects of strengths, weaknesses, opportunities and threats according to the current industrial status in an effort to promote this energy application. Additionally, some strategies were made for this promotion. Results show that (i) Chongqing's hydrogen energy industry has evident strengths, including powerful policy support, gradually improving industrial layout, and extensive application; (ii) its weaknesses contain incomplete subsidy scope, lagging construction of hydrogen-refueling stations, and uncoordinated development among districts and counties. It is necessary to unify policy standards and expand subsidy scope; and (iii) opportunities faced in Chongqing include hydrogen energy vehicle market, regional coordinated development, and potential hydrogen energy application in both waterway and industrial domain. However, it is also threatened by energy competition and hydrogen supply in winter. Therefore, it is essential to provide funding assistance, conduct hydrogen production pilot projects, improve infrastructure, implement policy guidance and subsidies to promote the introduction of hydrogen energy vehicles into taxi and online ride-hailing operation platforms, the diversification of supply end and the storage of hydrogen energy, strengthen regional cooperation, and undertake industrial transfer. Relevant enterprises and research institutes should offer more detailed data for policy makers in decision making. In conclusion, hydrogen energy industry in Chongqing has obvious strengths and huge potential despite several weaknesses. With its continuous development, Chongqing is expected to achieve the carbon-peaking carbon-neutrality goal, further to lay a solid foundation for the energy structure transformation.

Hydration may bring about wellbore instability in shales to further affect drilling safety and fracturing effect. Thus, taken shale samples with individual bedding angle as examples, some experiments on both hydration and ultrasonic transmission were carried out. Then, an elasticity parameter was inverted after optimization according to the principle of least square. Finally, the changes of acoustic velocity, as well as elasticity and anisotropy parameters at dissimilar hydration time were discussed, and the quantitative relation of elasticity parameter to hydration time was also pointed out. Results show that (i) shale hydration is considered as a continuous and then being stabilized process. And its degree increases fast, then slowly, and at last tending to be stable; (ii) the inversion method of elasticity parameter based on acoustic velocity at different bedding angle boasts high accuracy; and (iii) the model of quantitative relation of elasticity parameter to hydration time is achieved. In conclusion, qP wave velocity decreases apparently and then tends to be gentle as hydration time goes by. It is highly sensitive to this hydration, and can be used to evaluate not only hydration degree but fractures' propagation velocity inside shales. Moreover, qSH wave velocity presents the decreasing tendency along with hydration time and is weakly sensitive to the hydration. The elasticity parameter is negatively correlated to hydration time, among which, C₁₁, C₃₃ and C₁₃ have a large drop range while small in C₅₅ and C₆₆. And as hydration time goes by, the anisotropy intensity increases, then decreases, and tends to be stable.

In China, state-owned petroleum enterprises are confronted with increasingly strict requirements in their compliance management with the continuous deepening reform in all state-owned enterprises. In order to advance this management in depth fusion and the enterprises in high-quality development, practical achievements in current state-owned petroleum enterprises were discussed for the compliance management from six sorts of core dimension, including policy design, organizational operation, risk assessment, standard construction, cultural cultivation, and technological empowerment. Results show that (i) although some progress made, such enterprises still face challenges in this management, such as intensified international compliance pressure, high domestic regulatory complexity, insufficient internal governance function, and risk transmission in industrial chain; (ii) the new round of deepening reform in the state-owned enterprises, energy transformation policy dividends, technological innovation, and market mechanism improvement provide new changes for petroleum enterprises' compliant development; and (iii) it is necessary to make breakthrough from strategy, technology, ecology and international participation, build the hierarchical and classified governance system to strengthen strategic guidance, empower management with full-chain digital tools, diversify risks through industrial chain co-governance mechanisms, explore a flexible compliance mode to cope with difference in international rules, and advance management guarantee to ultimately achieve the transformation from "passive defense" to "active empowerment", providing strong support for these enterprises in both deepening reform and high-quality development.

Oil and gas show is active in central Sichuan Basin where is developed with more than 29 sets of hydrocarbon reservoirs vertically. However, stratigraphic unconformity results in great challenges in predicting reservoir pressure. Shallow gas may be often discovered unexpectedly in upper terrigenous strata, especially where is accompanied with some oil-bearing oil and gas with high pressure, creating difficulties in pressure calculation or well killing. In addition, insufficient calculation evidence may cause overflow failure. Thus, in order to precisely calculate the density of killing mud for overflow in such shallow oil and gas (oil-bearing accompanied gas) layers with high pressure in central basin, both pressure origin in such wells and the phenomenon of incorrect calculation were discussed through successful killing in PY2 well by means of the reciprocating engineer method. Then, taken oil column self-locking force into consideration, a new method to calculate the reservoir pressure was used to achieve the killing-mud density in accordant with the equivalent density of actual pressure, so that one-trip killing could be realized in success. Results show that (i) the reason why the improper density is computed by means of traditional killing formula is analyzed. And it is suggested there is the self-locking phenomenon in high-pressure oil and gas; (ii) the killing-mud density calculated from the new method has a deviation of only 8% from the actual density, indicating this accuracy is improved and can meet requirement of actual killing; and (iii) the calculated reservoir pressure is closer to the real pressure, implying this method can diminish well control risk greatly and reduce production loss. In conclusion, the method is of great referential value for disposing similar shallow oil and gas overflow wells.

For pneumatic-hydraulic valves, a sort of key devices on long-distance gas pipelines, its normal run decides downstream gas safety. Pneumatic-hydraulic actuators, however, have frequently suffered from abnormal shutdown with high failure in recent years since most devices early constructed and put into operation in both domestic gas distribution stations and long-distance pipelines become worse, further to greatly affect production safety for numerous enterprises. Thus, the abnormal shutdown of the Shafer pneumatic-hydraulic actuator caused by device failure was discussed, and failure mechanisms were pointed out for some key parts, including LineGuard electronic line break detection controller (hereinafter refer to as LineGuard controller), power supply equipment, pressure sensor, electromagnetic valve and hydraulic circuit. Results show that (i) incorrectly triggering the LineGuard controller is the main cause of abnormal shutdown; (ii) the power supply equipment in failure generates abnormal control signal; (iii) the data distortion of the pressure sensor results in misjudgment; (iv) the abnormality of the electromagnetic valve creates emergency failure; and (v) both blockage or leakage in the hydraulic circuit lessen the driving force in this actuator. In conclusion, it is recommended to establish a multi-level protection system and improve the lightning grounding, shielding grounding, cathodic protection, and insulation joint installation in these devices according to regulatory requirements; to establish redundant mechanisms for the power supply equipment and strengthen the calibration and maintenance of pressure equipment; to regularly check the electromagnetic valve and the circuit sealing; and to incorporate the LineGuard controller into the prevention system and check its integrity and function periodically.

One sour gasfield with high sulfur (H₂S) and moderate carbon dioxide (CO₂) was taken as an example to discuss how to recycle low-pressure sour gas from the gathering and transportation system so as to reduce the adverse effect of burning emission from sour gas on environment as well as improve exploitation and transportation. Such sour gas, however, cannot be directly recycled by means of traditional techniques due to low pressure. It is usually burnt with release flare, bringing about environmental pollution and resource waste. Thus, a methodology, which adopts compressors to pressurize low-pressure sour gas and then deliver it to high-pressure processes in the gathering and transportation system for recycling, has been proposed. Results show that (i) adopting low-flow multi-stage compressors can overcome technical problems in this recycling to ensure their efficient running; and (ii) for sour-gas compressors, both optimization and adjustment on running conditions greatly lower their failure and improve stable running. In conclusion, this methodology reduces environmental pollution, boosts resource utilization, and achieves win-win benefits in both economic and environmental levels. What's more, compressors' proper selection and running optimization guarantee them in long and smooth operation in high-sulfur environment, and provide credible technical assistance for zero emission of tail gas in sour gasfields.

The lagging data acquisition of gas and water production in gas wells restricts the validity of early warning for an individual well. Thus, based on machine learning (ML) algorithms, a method to dynamically predict gas and water production was established to improve the validity in abnormal producers. Results show that (i) with high correlation, seven core characteristic parameters including working system and tubing pressure are selected after the correlation analysis to construct a multi-dimensional data set; (ii) three ML algorithms are adopted for model training and testing (the ratio of training and testing sets is 2:1), among which the best stability and the highest accuracy are achieved in the random forest model; and (iii) combined with production characteristics, one classification model and another distinguished prediction model of "one strategy per well" are established according to the random forest algorithm. For these two models, the mean relative error in testing set is within 20%. After running stably in Windows' Python program for one year, the models remains their prediction accuracy over 80%. In conclusion, for all models, the error mainly results from data quality, data-setting rules, division of characteristic parameter sets, model design, and special production characteristics and changes of fluid flowing laws in gas producers. What's more, this ML-based method can predict gas and water production in the individual well in real time, and improve the early-warning validity in those abnormal producers, which is conducive to the transformation of gasfield production and management from digitalization to intelligence.

As a sort of cleaner energy resources, natural gas is of great significance for ensuring energy supply security in China and optimizing domestic energy structure with the accelerated structure transition and intensified climate changes on the globe. However, three uncertainties such as geopolitical conflicts, price fluctuation and environmental challenges severely threaten both stability and ductility in natural-gas system. Therefore, an estimation method which covers various indicators of gas production, supply, storage and sales was constructed for the ductility in terms of four kinds of dimension in resources, politics, economy and environment. And corresponding estimation models were also established. In addition, some measures were made to promote this ductility. Results show that (i) both analytic hierarchy process (AHP) and entropy method can quantify the impact of multiple factors (e.g. external risks, domestic policies, and production, supply, storage and sales) on the ductility. The ductility index was 0.46876 in 2022. In which political stability, nonviolence index and government efficiency exerted the greatest impact, followed by both capacity and production in underground gas storages (UGSs); (ii) this ductility increases continuously in China. With the diversification of gas supply and the acceleration of UGS's construction, the system to resist risks and recover is greatly improved; (iii) at present, the key measures to promote the ductility and major risk prevention and resolution capacity are strengthening for the diversified development of gas import channels, reducing the impact of geopolitical conflicts on the domestic natural-gas system, and upgrading emergency mechanisms, and the construction of production, supply, storage and sales infrastructure. In conclusion, this estimation method provides scientific evidence and practical guidance for the management and optimization on the natural-gas system.

The grey relative correlation degree was employed to evaluate the significance level of multi-collinearity among various influential factors in an effort to precisely predict the evolutional trend of natural-gas demand in China. Followed by the criterion of decreasing correlation, a method of stepwise regression analysis was also used to discuss these factors influencing on the demand. Additionally, an "optimal" model was created for demand prediction. Results show that (i) economic expansion is the most important valid motivator for the rapid increase in this demand, and optimizing the energy consumption structure is the key effective motivator for this demand growth; (ii) the created "optimal" model of stepwise regression double logarithmic demand function accurately captures the trend of nonlinear inflection points in the demand, and also achieves better prediction performance. It is regarded as a powerful tool to predict the trend of natural-gas demand; and (iii) this demand in China will peak in two years when the peak will be 5,938×10⁸ m³ from 2035 to 2036. And it will attain 4,784 × 10⁸ m³ in 2040 with the annual growth decreasing to 1.8%. In conclusion, in addition to the prediction on the natural-gas demand, this model not only offers technical assistance for predicting the demand trend but theoretical basis for related energy enterprises and institutions to draw up allocation plans and policies about natural-gas resources.

Taking tight sandstone gas reservoirs of the second member in Xujiahe Formation (hereinafter referred to as Xujiahe 2 Member), Zhongba gasfield, northwestern Sichuan Basin, as examples, we analyzed reservoir rocks in terms of mineral composition, pore types and micro characteristics by means of several experimental ways, such as core observation, X-ray diffraction, cast-thin section, nano-CT scanning, high-pressure mercury injection, and nuclear magnetic resonance (NMR), in order to optimize reservoirs' development effect and improve their ultimate recovery factor. In addition, the main factors affecting the difference among physical properties were discussed for these reservoirs. And both development prospect and technical direction were also pointed out for these low-quality reservoirs through some stimulation practice. Results show that (i) Xujiahe 2 reservoirs can be classified into three types. Among which, both type I and II reservoirs are dominated by residual intergranular pore and intergranular dissolved pore. In type III, the proportion of feldspar and lithic intragranular dissolved pore increases significantly, and pore structure becomes more complicated; and (ii) these three types are similar in distribution interval of main pore radius while great division in throat structure. The pore-throat radius is mainly in the range of 0.75-1.55 μm and 0.08-0.21 μm in type I, 0.49-0.75 μm in type II, and further decrease to 0.37-0.49 μm in type III, respectively. This radius discrepancy directly results in the reservoirs in various permeability and productivity. In conclusion, our understanding that pore-throat radius is a key factor controlling the difference among physical properties of Xujiahe 2 reservoirs in Zhongba gasfield may provide theoretical basis for formulating development strategies. What's more, production wells are dominated by type I and II reservoirs in the early development. Practice proves that sand fracturing with high intensity in type III can actively expand the effective pore-throat radius and setup hydraulic fracture network to release natural gas from intragranular dissolved pore, indicating that, with a certain development prospect, this type serves as the vital reservoirs for this field to ensure stable production further to increase.

To assess exactly the effect of natural-gas price fluctuation on the energy, economy, and environment (3E) system is an essential prerequisite to expedite the market-oriented mechanism reform. Therefore, taken Sichuan province of the "Daqing-scale gas province" in China as an example, a model of computable general equilibrium (CGE) was constructed for this fluctuation in terms of production, trade, households, and environment sectors. Moreover, affected by distinct fluctuation, the regional macroeconomic development, economic benefits in individual department, energy consumption structure, and CO₂ emission from energy utilization were assessed. Results show that (i) stemmed from both reduction and expansion in government subsidies, the fluctuation of natural-gas price may induce resource reallocation by altering actual consumer demand to exert a heterogeneous effect on economic output in several sectors; (ii) the fluctuation may initiate some changes in energy supply and demand through a substitution effect whose degree is sorted from big to small: natural gas, coal, oil, and electricity and heating power, reflecting that gas industry exhibits monopolistic character, while a little fluctuation in other energy resources regulated or controlled by the "invisible hand" of market; (iii) CO₂ emission from both agriculture and construction industry is less correlated to gas price because of their small dependence on energy; (iv) light and service industries are somewhat related to this price, but it is essential to prevent resource waste from price drop; (v) CO₂ emission from transportation industry varies with the price due to the substitution effect stimulated by the dual-carbon goal and cost effect; (vi) it is difficult for heavy industry to separate from coal and oil consumption under existing technologies, resulting in a minor effect of gas price fluctuation; and (vii) apparently, chemical industry has something to do with this fluctuation since natural gas serves as not only a chemical raw material but a type of fuel.

Tight sandstone gas reservoirs feature strong interlayer and planar heterogeneity greatly impacting on the accuracy of geological modeling. Apart from the aims of cost reduction and efficiency increase, the contribution of each horizontal interval to production is unclear, and the main influential factors to restrict single-well productivity increase are ambiguous. Thus, some horizontal wells in tight sandstone gas reservoirs were taken as objectives to deeply discuss their production profile and the association with related factors by means of the method of gray correlation whose findings were introduced into this modeling to further optimize modeling. Results show that (i) as a geological factor, gas saturation is closely in correlation with gas production; (ii) based on dual constrains of actual drilling and production profile, multi-point geostatistics are adopted in the model of geological modeling correction to simulate facies boundary once more. The model accuracy in reservoir expansion can be enlarged by 15% after correction; and (iii) eventually, on the basis of gray correlation analysis, the attribute model is more accordant with dynamic production data after reservoir parameters are recorrected through the weight correction formula. In conclusion, as for the development of tight sandstone gas reservoir by horizontal wells, probing into both gas production profile and influential factors is crucial for fully understanding and optimizing productivity and development strategies. Moreover, dependent on dual constrains of actual drilling and production profile, the model of geological modeling correction and the tool to correct reservoir parameters from gray correlation analysis may amend some bias in modeling, further to provide reliable evidence for next development.

The emergence of foreign trading hubs with mature natural-gas markets was ascertained in order to push forward market-oriented reforms on natural gas in China and promote global impact. Furthermore, a comparative analysis was conducted on hub types and spot transaction modes, and some scenarios and suggestions to propel China's natural-gas hub pricing were made. Results show that (i) setting up China's trading hubs is important for reform push and impact promotion. Hub pricing is the future orientation in national natural-gas industry; (ii) most of China does not qualify for hub construction while the greatest potential in the Yangtze River Delta and Pearl River Delta regions; and (iii) China's natural-gas hub pricing neither uses blindly American mode nor copy European mode. Instead, it must explore a fresh mode available for its own conditions. Accordingly, some suggestions are made as follows: changing the pricing benchmark in the current mechanism from government pricing to hub pricing, establishing virtual hubs which call for pillars in both infrastructure and software, and initiating the research and design of hub pricing, as well as planning and constructing essential infrastructures, hence making hub pricing a reality as soon as possible.

Natural-gas industry is regarded as the transitional link with low-carbon energy transformation while hydrogen energy industry as the key pillar of clean energy in the future. Their collaboration will promote the optimization of energy structure to fruther achieve the dual-carbon goal. Thus, their current industrial status and the feasibility of natural gas to hydrogen energy were figured out. Furthermore, the pathway towards this collaboration throughout the whole industrial chain was put forward. Results show that (i) it is essential to continuously leverage natural gas in its low-carbon advantages in the current stage of increasing fossil energy; (ii) natural-gas industry shall perform carbon capture, utilization and storage (CCUS) pilot projects to ensure this collaboration in the upstream, comprehensively utilize cold energy at LNG-receiving stations, and manufacture small skid-mounted containerized hydrogen production equipment, while hydrogen energy industry shall innovate green hydrogen electrolysis technologies relying on natural-gas resources, so as to set up a complementary layout of low-carbon hydrogen production pathway; (iii) to ensure facility sharing in the midstream, it is suggested to make use of existing infrastructure such as gas pipelines or LNG-receiving stations to make breakthrough in hydrogen-blending transportation of in-service gas pipelines, pipeline transformation for high-pressure hydrogen transportation, and liquid hydrogen storage; and (iv) to guarantee scenario coupling in the downstream, it is recommend to highlight the construction of hydrogen energy transportation and platform, and orderly enlarge the hydrogen energy available for transportation, energy storage, and industrial domains. In conclusion, the collaboration of both natural gas and hydrogen energy throughout the whole industry drives the green upgrading of traditional energy and the large-scale substitution of hydrogen energy by virtue of collaborative cost reduction and low-carbon technological coupling, which is of profound significance for accelerating the construction of safe and efficient new energy system.

With natural-gas price liberalization and control as the soul, both thoughts and measures were discussed and made to promote market-oriented reform on natural-gas price in China in order to thoroughly implement the spirit of the Third Plenary Session of the 20th Central Committee of the Communist Party of China (CPC). Results show that (i) this price must be "flexible" and "controllable", which is an inevitable requirement for building the socialist market economy system in high standard and also an inevitable choice for correctly handling the relation of the government to markets, thus brings new and strict demand for reform promotion according to the overall idea of "controlling the middle and liberalizing both ends", which means greater challenges to the reform; and (ii) the realization of "flexible" and "controllable" price refers to the price of the gate station link, but local distribution is the "Last One-kilometer" of natural-gas industrial chain. So, deepening this reform in local gas distribution link is crucial to achieving this price "flexible" and "controllable". Some thoughts and measures are proposed and made as follows. First, short-term reform should lay equal stress on "flexibility" and "controllability", and achieve those two by improving the combination policy under the current price system. The recommended solution is to cancel the price at the gate station link, liberalize the price at both ends, and divide the market into regulated and unregulated gas market from the consumption end to the application to different price policy. Second, long-term reform is to construct trading hubs to replace governmental pricing with market's standard price, and get the ultimate goal of market-oriented price reform. It is recommended to construct the hub pricing scheme and hubs as soon as possible, including some study on related supporting measures. Third, price reform on the gas distribution link should be deepened by promoting the extensive integration of urban-gas enterprises and the fair access to local gas distribution pipelines, standardizing the pricing in these enterprises, strictly supervising gas distribution price, and establishing the sound price linkage mechanism in both upstream and downstream.

Currently, petroleum enterprises are facing challenges in the marketization of natural-gas price. Therefore, pricing mechanisms in PetroChina was made a comparison with those in Sinopec and CNOOC to analyze marketization constraints. Then, coupled with marketization process in China, the development trend of natural-gas trading and its impact on such enterprises were discussed entirely. At last, a corresponding strategy was made from aspects of transaction mode, classified pricing, secondary transaction, facility coordination, and customer management. Results show that (i) the innovated "annual or medium to long-term" contract period and the established price mechanism linked LNG index with oil price can mitigate fluctuation risks; (ii) jointly promoting gas storage facilities and production peak shaving can greatly expand both resource allocation and configuration flexibility; and (iii) classified pricing, secondary transaction mode and stable long-term contract customers can strengthen the market's buffering capacity against supply-demand imbalance. In conclusion, integrating mechanism innovation, facility coordination with precise policy implementation, petroleum enterprises need to set up an all-round response system covering price risk management, resource optimization and allocation, and market supply-demand regulation in order to remarkably advance market adaptability and stable profits, thereby contributing to the sustainable development of natural-gas industry under this price marketization.

Continuous tests on production profile were conducted in DS66P18H horizontal well of tight gas reservoirs with rich water, Dongsheng gasfield, Ordos Basin, so as to figure out production performance from hydraulically fractured intervals in such reservoirs. Moreover, production changes on pay zones were analyzed for all production periods. The relation of production performance was found to not only pay zones but reservoir properties, also this relation to fracturing treatment. It is pointed that these tight reservoirs are characterized high water saturation and complex seepage mechanisms. And the contribution of each pay zone to productivity is jointly conditioned by reservoir's physical properties, fracturing intensity, and working system. Results show that (i) along with the increase of production pressure difference, the principal gas-producing interval does not change its site at the same production period. However, its contribution to production deceases, while those pay zones without production in initial stage start contributing to output; (ii) the contribution of each pay zone to output is positively correlated to physical properties and gas-bearing property, that is, the better the physical properties and gas-bearing property are, the greater the contribution is; and (iii) this contribution is less affected by fracturing treatment. In conclusion, production performance in each pay zone may be made clear from production profile tests on horizontal wells in tight gas reservoirs with rich water. And production profile is of practical significance for such reservoirs in sustained, stable, quality and efficient development.

Low-carbon energy, for example renewable resources and natural gas, will serve as the major force in its future development with the proposed dual-carbon goal (including carbon peak and carbon neutrality). Thus, taken the natural-gas industry in Sichuan and Chongqing areas as an example, the industrial current status was analyzed and problems in risk transmission were discussed in an effort to find out an inherent law on this transmission in these two areas. With that, a susceptible, exposed, infected, recovered, and susceptible (SEIRS) model which is suitable for the risk transmission has been developed. Then, the impact of its threshold on the transmission was analyzed by means of Matlab software, and the effect of threshold factors was simulated. Finally, some policy suggestions on risk control were made. Results show that (i) because of infection rate, direct immunity rate, cure rate, and immune degeneration rate, there exists a threshold in this risk transmission; (ii) the transmission may be conditioned through human intervention. It is essential to implement whole process control involving before, during, and after the event in the case of sudden risks; and (iii) fair risk diversification and emergency response mechanisms may improve the ability to withstand risks in the natural-gas industrial chain. In conclusion, this SEIRS model can provide reference for formulating the policy system for safe and smooth gas supply in Sichuan and Chongqing areas.

As the backbone to build a novel energy system in China, both natural gas and hydrogen energy play regulating, supporting and balancing roles in the process of green and low-carbon energy transition. Thus, based on current situation and growth trend of these two energies, the growth room was discussed for their integration to promote coordinated and quality development. From the perspective of whole industrial chain, the growth pathway towards their integration was discussed, and strategies and suggestions are formulated and made. Results show that (i) for natural gas, its supply increases steadily in China along with more and more exploration and development. The consumption sustains its growth in the near and medium term; (ii) for hydrogen energy resources, their exploitation are deepened continuously and the productivity construction is accelerated. And the resources serve as a new driving force for energy increase in China; (iii) the integration of natural gas and hydrogen energy industries has broad development prospect. And the industrial chain features, technological foundation, and institutional environment may provide support for this deep integration; (iv) the co-development and growth of limited carbon based energy and infinite zero-carbon new energy can be achieved by enhancing the collaboration and mutual promotion between industrial chain, strengthening resource sharing and complementary advantages, and deploying the utilization pathway towards the integration in upstream preparation, midstream storage and transportation, and downstream application; and (v) it is necessary to empower the value enhancement of industrial chain in terms of top-level design, industrial alliance, technological innovation, digital and intelligent transformation, and demonstration application, and sufficiently inspire the integration potential throughout the whole industrial chain, so as to inject green new momentum to advance energy transition in this country, promoting the ecological and healthy growth of carbon neutrality industry.

As clean energy, both biogas and hydrogen energy get more and more concerns along with the increasing demand in global clean energy. Thus, an integrated gas-electricity-hydrogen energy model coupled with biogas was proposed to break the bottleneck encountered in their employment, and resolve the current situation that renewable energy sources are utilized in an isolated pattern. And energy conversion rate, economy, and environmental impact under this model were estimated comprehensively. Results show that (i) this model constitutes two units of both biogas preparation and application. Among which the application unit covers three modules (such as gas power generation, hydrogen production from natural gas, and urban gas pipeline) and energy management system; (ii) this model deeply integrates two technologies including biogas power generation and steam methane reform, thus realizing the cascade utilization and complementary superiority of energy sources; and (iii) the integrated model evidently improves energy utilization and reduce environmental pollution. In conclusion, owing to the improved utilization and reduced pollution, this model possesses better economic feasibility in the future and provides new development direction for energy transformation. Despite negative net present value and higher costs nowadays, this integrated energy model is still provided with a great prospect for future profitability due to hydrogen sales and diversified energy structure.

For classic natural-gas transmission-loss management modes, there exist some shortcomings, for example insufficient data sharing, low capability in real-time diagnosis, and low collaborative efficiency. Therefore, taking one oil and gas district with complex pipeline network as an example, we established a full-chain digital transmission-loss management system covering data acquisition, intelligent diagnosis and decision support in an effort to promote the management validity for digital transformation. Then, this validity was verified by means of evaluation tools. And the key technical course was analyzed for digital technologies in terms of data integration, intelligent warning and collaborative management. At last, inherent deficiencies of traditional electronic means were found out in terms of dynamic data response, trans-department collaboration and decision support. Results show that (i) this digital system achieves dynamic correlation through the data center integration system that efficiently acquires multi-source heterogeneous data based on the Internet of Things (IoT) and SCADA technology, resulting in an 80% increase in data acquisition; (ii) the intelligent diagnosis module based on machine-learning algorithm directly monitors the loss fluctuation and predicts its trend, with the accuracy of anomaly detection up to 90%. This module is able to trigger and push the warning within 5 minutes, which is 90% more efficient than manual positioning. It timely avoids leakage and measurement failure, and reduces economic losses by more than 2 million yuan per year; (iii) the centralized storage and multi-terminal collaboration mechanism improve the work order processing by 85%, the trans-department collaboration by 70%, and user satisfaction from 78% to 91%, respectively; and (iv) this system saves labor costs by 2.75 million yuan per year on the average and achieves carbon reduction by reducing non-metric losses, wining great economic and social benefits. In conclusion, digital technologies reconstruct the paradigm of transmission-loss management through a closed loop of "data-business-decision", whose end value lies in breakthrough made in real time, collaboration and prediction capability, providing feasible pathway for agile management in the scenarios of complex pipeline network. What's more, it is essential to further integrate natural language processing and federated learning technologies in the future to develop the ability to process unstructured data and break the bottleneck in inter-enterprise data sharing, and promote the evolution of transmission-loss management into the intelligent stage.

Natural gas, as a sort of low-carbon and clean energy resources, reveals an increasingly strategic role with the accelerating transformation of energy structure in the world. However, its producers are obliged to invest more constantly as exploration and development extend to deep-seated or unconventional gas. For full cost, as a core indicator for predicting economic benefits in such enterprises, its accuracy may directly affect the investment decision, market pricing, and national energy security. Thus, an innovative model was developed to fast predict the full cost in natural gas because traditional approaches based on complex financial models are difficult to make rapid decision. Furthermore, a theory on dual cost structure of new and old gas wells was proposed to achieve dynamic balance in cost behaviors between existing and new production wells through an algorithm of production weight coupling. Results show that (i) full cost consists of operating cost, depletion, depreciation and amortization, period expenses, as well as taxes and fees in addition to income tax. For those wells newly put into production, their full cost is basically confirmed at the time of commissioning and remains relatively stable in the coming years; (ii) coupled with cost behaviors of both new and existing wells, the dual cost structure theory can help in quick prediction on the full cost trend, further to improve short-term prediction accuracy and judge long-term tend; and (iii) relying on technological advancement, gas producers may reduce single-well investment and increase individual output in new production wells so as to control their full cost. In conclusion, the optimized prediction model is of great significance for these producers to confront with price fluctuation and policy adjustment. Prediction results from this model can be used to choose better investment direction in a planned way for cost control with effect and promote enterprises' healthy and sustainable development.

So far, a set of relatively mature techniques has been developed to settle drilling complexities such as sticking, broken drilling rig, and overflow. According to statistics, however, practicable solutions are still absent in some rare events, which may affect drilling schedule to further increase nonproductive time, for instance casing slip while setting casing. These events also cause even worse accidents or well abandonment. As the matter of fact, there exist difficulties in casing fishing resulted from long casing fish, high suspended weight and large lifting friction. For example, originated from downhole fish structure, damage of the fish top, and wellbore and casing size, the second-spud Ø244.5 mm casing slipped and fell into WH-3 well. And some fishing tools, including special large-headed male cone, casing circulation head, and retractable caving fishing spear, did not work. Thus, we optimized conventional casing circulation head and developed an improved circulation-head fishing tool. Results show that (i) the improved fishing tool can successfully catch the fallen fish at the first time, and reduce the frequency of drilling trips; and (ii) with circulation flushing and fastening capability, functional integration has been conducted to deal with wellbore cleaning and connection strength. It is concluded that the new fishing tool offers reusable solutions on similar accidents and provides valuable reference for studying these accidents.

For China's energy enterprises, the strategic performance management has become an indispensable management tool to get used to the major strategic deployment on accelerating digitalization and green low-carbon transformation, ensuring energy supply security, and promoting regional coordinated development. Therefore, the performance management with low-cost strategy was optimized by means of management theories and methods based on the development trend and goals in oil and gasfield enterprises. Results show that (i) from the perspective of strategic management, the built model structurally consists of low-cost strategic development environment analysis, development plan, performance management organization, performance business process, performance assessment, and performance decision support; (ii) from the perspective of balanced scorecard, optimizing this performance model includes the optimization of strategic map, business chain performance assessment index system, performance evaluation index calculation model, performance evaluation, and application scenario of evaluation results; and (iii) from the perspective of collaborative innovation, some measures are made to ensure the smooth implementation of low-cost strategic management, for example cultivating a new concept of low-cost strategy, building the strategic cost management system, collaboratively innovating technology and management, actively developing and cultivating oil and gas markets, perfecting the corporate governance system, and constructing the comprehensive performance evaluation system. It is of practical significance for optimizing traditional management model with low-cost strategy, improving acting mechanisms of performance management and the application effectiveness of tools in key control links, and promoting the collaborative innovation of performance management system and mechanisms, technology and management, and policies and regulation and governance in the oil and gasfield enterprises.

Most shale gas wells in Weirong gasfield suffer wellbore blockages in the production tail. Thus, the composition was diagnosed for the captured blockages by means of thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) and energy dispersive spectrum (EDX), indicating that these blockages are composed of organic oil phase and inorganic solid phase. Results show that (i) perhaps the oil phase in blockages mostly stem from the third-spudding oil-based drilling fluid; (ii) dominated by ceramsite, iron compound, cuttings and fiber, the solid phase is the product of fracturing sand backflow, oxidizing dreg and carbon dioxide (CO₂) corrosion; and (iii) based on the diagnosed blockages' genesis, the composite removal system including organic and inorganic acid, amino polyether and higher alcohol has been optimally prepared in laboratory. Its dissolution is up to 52.2%. It is only takes 48 minutes to entirely pass through the simulated blockage points under indoor pressure difference of 5 MPa and 70℃. In conclusion, the primary reason for wellbore blockages in this field is the channel throttling blockages containing iron compound, fracturing sand and oil phase accumulated in wellbore. What's more, the prepared removal system according to the idea of "desorption for oil removal, dispersion for solution enhancement, and dissolution for carrying" may dissolve, disperse and penetrate these blockages very well. The buildup soaking realized by pump and gas-lift trucks or liquid-blending tanks as well as the full hole flushing serve as two means for blockage removal in wellbore. Additionally, such removal has been applied to 20 wells like WY25-3HF well, with the success rate up to 90% and incremental production of 1,500×10⁴ m³.

There exists low accuracy in predicting daily price of liquefied natural gas (LNG) because of high price fluctuation and complex periodicity. Thus, integrated the Informer architecture to the Fast Fourier Transform (FFT) frequency enhancement mechanism (Informer-FFT), a short-term dynamic prediction method have been developed. It makes use of Informer's advantages in handling long-sequence dependency and introduces FFT to extract frequency-domain characters explicitly in price sequence as auxiliary input in order to synchronously capture both time-domain dynamics and periodic patterns in price fluctuation. Some empirical study was conducted by using daily data on China's LNG factory price from 2011 to 2025. Results show that (i) the mean absolute percentage error (MAPE) from this method is 2.37% and 2.65% on both test and validation sets, respectively, much superior to that from the other two baseline models of long short-term memory (LSTM) and standard Transformer; (ii) frequency-domain analysis reveals a strong dominant period, approximately 955 days, in LNG price sequence, proving the effectiveness of introducing FFT characters in capturing non-traditional long-period patterns and obviously enhancing this model in predicting ability; and (iii) the model still takes on excellent generalization ability and robustness on the validation set containing unknown data, and the predicted curves are highly consistent with actual ones. It is concluded that this integrated method can precisely and stably predict LNG's daily price, and provide effective technical support for relevant market entities in risk management and decision-making.

One technology of liquid organic hydrogen carrier (LOHC) was discussed from aspects of chemical mechanism, economy and regional adaptability in order to address technical difficulties in renewable energy consumption as well as hydrogen storage and transportation in Sichuan and Xizang regions. Then, the potential demand, technical feasibility and commercial pathway were figured out for the green hydrogen in these two regions. Based on liquid carriers such as methylcyclohexane, a plan to optimize storage and transportation was worked out. In addition, with catalyst optimization, scenario adaptation and policy coordination as the soul, some promotion strategies were made for these regions. Results show that (i) abundant hydropower and photovoltaic resources which may provide enormous potential for green hydrogen production are found in these two regions. It is predicted that the green-hydrogen demand will reach 607×10⁴ t in 2060; (ii) compared with traditional high-pressure gaseous hydrogen storage and low-temperature liquid hydrogen storage, LOHC technology is characterized by the storage density of up to 5.0wt%-7.5 wt%, low transportation costs, and especially high compatibility with existing petrochemical infrastructure (oil tankers or pipelines); and (iii) combined with corresponding policy guidance, non-precious metal catalysts, for example iron-based or nickel-based catalysts, may effectively improve the impact of high-altitude, low-pressure anoxic environment on storage efficiency, so as to facilitate this technology more available for complex geographical environment in Sichuan and Xizang regions, promote the closed-loop development of hydrogen energy industrial chain, and assist energy's clean transformation and economically sustainable development. In conclusion, in addition to abundant wind and solar resources, heavy future demand in green hydrogen provides extensive application scenarios for LOHC technology. What's more, compared with traditional hydrogen-storage technologies, LOHC’s vigorous advancement significantly reduces costs and is provided with economic advantages in Sichuan and Xizang regions. Furthermore, LOHC technology is quite available for complex geographical environment and has better regional adaptability.

For natural-gas power generation in China, its industrial chain growth is an important link in achieving the dual-carbon goal. At present, most financial evaluation methods for gas-fueled power projects attach importance to project itself. However, for petroleum companies with the entire industrial chain in gas power generation, such methods cannot thoroughly reflect the overall contribution of gas-fueled power plants to this chain. Therefore, based on the marginal contribution theory, a novel evaluation method which considers the chain's incremental value resulted from new plants in a comprehensive manner has been proposed. Results show that the proposed financial model can be used to evaluate the project's overall value in this industrial chain, discuss the impact of project on each chain to facilitate sound decision-making on project investment, contrast several projects with the same type under capital constraints, and reveal that the investment entity holding complete industrial chain may share risks of gas price fluctuation at all chain, enabling it to have higher risk resistance than independent power plants. It is deemed that the new method is of great significance for the decision-making on gas-fueled power projects, project selection, and layout of gas power generation industrial chain.