ALBERT

Description: Transient pressure analysis is a crucial tool to forecast the production performance during the exploration and production process in gas reservoirs. Usually, a regular shaped outer boundary is assumed in previous studies for well-testing analysis, which is just a simplification of practical cases and cannot reflect the actual boundaries of reservoirs. In this paper, a mathematical model is established to analyze the transient pressure behaviors of a horizontal well in an arbitrarily shaped gas reservoir. Dimensionless treatment, Laplace transformation, and boundary element method are applied in solving the model, which is verified by comparing with the results from the source function method. Based on the Stehfest numerical inversion method, the models of single-porosity media and dual-porosity media are solved respectively. Then, the time-domain curves of pseudo pressure and its derivative are obtained, and the flow regimes are identified. Finally, the impacts of some critical parameters on pressure transient behaviors are analyzed, including storativity ratio, interporosity coefficient, well length, and well orientation. This paper presents an effective way to handle complex external boundary problems in gas reservoirs.

Description: This study analyzes the feasibility of satisfying the demand of three Football Stadiums for the 2022 FIFA World Cup in Qatar, using the wind’s kinetic energy. For all three selected locations (Lusail, Al Rayyan, and Al Wakrah), the wind potentiality is calculated through an environmental parameters study, from which the wind power density is obtained. Furthermore, a commercial wind turbine with proper characteristics is selected, and the same case study for each location is presented, to quantify the capacity that wind energy offers for satisfying the maximum energy demand of each associated stadium. In addition, the environmental benefits and the time required by each wind farm to satisfy the energy demand are computed. The results reveal that the conditions enable the use of wind energy for this purpose, based on a 5.06 m/s, 4.63 m/s, and 5.18 m/s velocity mean for Lusail, Al Rayyan, and Al Wakrah, respectively; from which values of 187.49 W/m2, 150.96 W/m2, and 187.29 W/m2 of wind power density are obtained. Also, the proposed wind farms could produce 69,952.56 MWh/year, 59,550.19 MWh/year, and 75,333.70 MWh/year, respectively. Moreover, the wind farms should produce energy for a period of 5.64 h, 4.41 h, and 5.23 h, to satisfy the maximum demand by a football match in its associated location. Additionally, to avoid the implementation of a storage system, the electricity obtained from the wind is connected to the power grid, decreasing the quota of fossil fuel power plants. In consequence, Qatar will eliminate the emissions of approximately 23.376 tons of CO2 in total per trio of matches held in these stadiums. Finally, a post 2022 FIFA World Cup scenario is analyzed, obtaining a positive outcome from both environmental and economic perspectives, in which an average of 14,675 tons of CO2 and 6.03 Million US$ can be saved annually.

Description: The mining area is the main place for the development and utilization of Coalbed Methane (CBM), and there are a series of systems for the development and utilization of CBM. However, owing to lack of a clear understanding of demand-side gas consumption rules and a reasonable resource allocation system, a large amount of CBM resources in the mining area are wasted. In order to predict the demand for CBM dynamically, the Seasonal Auto Regressive Integrated Moving Average (SARIMA) model, Additive Holt-Winters (AHW) model and Multiplicative Holt-Winters (MHW) model based on time series are used to predict the monthly demand for CBM in Yangquan Mine Area in 2020, respectively. Then the predicted results are evaluated by using the prediction model parameters combined with the characteristics of actual demand for CBM. Finally, a resource allocation system under different supply and demand conditions is built to reduce the waste of resources. In this paper, it is found that the information of the actual data is not sufficiently extracted in the MHW model while the SARIMA model can reflect the cyclical trend of monthly demand for CBM under ideal conditions. Furthermore, the AHW model can reasonably predict the demand for CBM under the influence of COVID-19, with a mean relative error of 0.099. The supply and demand distribution system built based on the proposed models can solve the problem of seasonal unevenness of CBM demand in mining areas and ensure the economic benefits of mining areas.

Description: The reservoir architecture analysis of braided rivers, especially falling-silt seam forms, has played a key role in predicting remaining oil distributions. However, no studies have used architecture analyses that document braided river outcrops and researched the tapping of the few remaining oil distributions based on outcrops in the Songliao basin, northeast China. In this paper, the architecture characteristics and remaining oil distribution of braided river reservoirs are studied using a combination of an outcrop, modern deposition and subsurface well data. The new 8–13 m thick Lower Cretaceous Quantou Formation outcrop of the Songliao basin is a braided fluvial succession arranged in one large fining-upward cycle. Eight facies (Gt, St, Sm, Sh, Sp, Sw, Fl and Fm), four architecture elements (CH, DA, LV, and FF), and three orders of bounding surfaces (third-, fourth-, and fifth-order) are recognized. A new distribution pattern of falling-silt seams and a braided river architecture model are presented according to the analysis of the outcrop. In the mid-channel bar, the falling-silt seams thin from the mid-bar to the bar tail following the flow direction. Each falling-silt seam is oriented tangentially to the basal surface of the mid-channel bar, and the upper falling-silt seam extends farther than the lower one. In a Daqing Oilfield exploitation block in the Songliao basin, while channels and bars are the main reservoir units, they have different remaining oil distribution patterns. For bars, water injection wells located at the mid-bar, zonal injection technology, the drilling of horizontal wells, and proper well patterns are proposed. Fourth-order bounding surfaces, single braided channels, stacking patterns, and the lateral blocking of levees and floodplains are the key factors affecting the remaining oil distribution in channels.

Description: Wind resource assessments are carried out for two sites in Tuvalu: Funafuti and Nukufetau. The wind speeds at 34 and 20 m above ground level were recorded for approximately 12 months and analyzed. The averages of each site are computed as the overall, daily, monthly, annual, and seasonal averages. The overall average wind speeds for Funafuti and Nukufetau at 34 m above ground level were estimated to be 6.19 and 5.36 m/s, respectively. The turbulence intensities at the two sites were also analyzed. The turbulence intensity is also computed for windy and low-wind days. Wind shear analysis was carried out and correlated with temperature variation. Ten different methods: median and quartiles method, the empirical method of Lysen, the empirical method of Justus, the moments method, the least squares method, the maximum likelihood method, the modified maximum likelihood method, the energy pattern factor method, method of multi-objective moments, and the wind atlas analysis and application program method were used to find the Weibull parameters. From these methods, the best method is used to determine the wind power density for the site. The wind power density for Funafuti is 228.18 W/m2 and for Nukufetau is 145.1 W/m2. The site maps were digitized and with the WAsP software, five potential locations were selected for each site from the wind resource map. The annual energy production for the sites was computed using wind atlas analysis and application program to be 2921.34 and 1848.49 MWh. The payback periods of installing the turbines for each site are calculated by performing an economic analysis, which showed payback periods of between 3.13 and 4.21 years for Funafuti and between 4.83 to 6.72 years for Nukufetau.

Description: The development of coalbed methane not only ensures the supply of natural gas but also reduces the risks of coal mine accidents. The micropore structure of coalbed methane reservoir affects the seepage of coalbed methane; improvement of pore structure is one of the effective methods to enhance the efficiency of coalbed methane exploitation. In this study, low-pressure nitrogen gas adsorption, specific surface area analysis, nuclear magnetic resonance spectroscopy, and centrifugation experiment were used to evaluate the effect of ethanol on coal microscopic pore structure and fluid distribution during hydraulic fracturing. Seven coal samples were collected from the No. 3 coal seam in Zhaozhuang Mine, Qinshui Basin. The samples are mainly composed of micropores, transition pores, and mesopores. The experimental results show that ethanol can significantly change the pore structure by increasing the pore diameter. The average specific surface area, pore volume, and pore diameter of rock samples before ethanol immersion are 1.1270 m2/g, 0.0104 cm3/g, and 14.20 nm, respectively. The three parameters of rock samples after ethanol immersion are 0.5865 m2/g, 0.0025 cm3/g, and 29.37 nm. Ethanol improves the connectivity between micropores and mesopores. The average irreducible fluid saturation of samples saturated with formation water after centrifugation is 86%, and the average irreducible fluid saturation of samples soaked in three concentrations of ethanol solution decreases. It is considered that an ethanol solution of 0.4% concentration has the best effect on improving the pore structure and fluid distribution.

Description: The hydrogen energy system based on the multi-energy complementary of renewable energy can improve the consumption of renewable energy, reduce the adverse impact on the power grid system, and has the characteristics of green, low carbon, sustainable, etc., which is currently a global research hotspot. Based on the basic principles of hydrogen production technology, this paper introduces the current hydrogen energy system topology, and summarizes the technical advantages of renewable energy complementary hydrogen production and the complementary system energy coordination forms. The problems that have been solved or reached consensus are summarized, and the current status of hydrogen energy system research at home and abroad is introduced in detail. On this basis, the key technologies of multi-energy complementation of hydrogen energy system are elaborated, especially in-depth research and discussion on coordinated control strategies, energy storage and capacity allocation, energy management, and electrolysis water hydrogen production technology. The development trend of the multi-energy complementary system and the hydrogen energy industry chain is also presented, which provides a reference for the development of hydrogen production technology and hydrogen energy utilization of the renewable energy complementary system.

Description: Shale gas production after drill-in, completion, and hydraulic fracturing is strongly affected by formation damage. In order to determine the damage mechanisms for nonmarine shale reservoir, a series of assessments of sensitivity damage, water block damage, water-based drill-in fluids damage, and water damage to gas diffusion on 20 shale samples obtained from Chang 7 Formation were conducted and analyzed. Results indicate that, in the Chang 7 Formation shale, there is extremely strong stress sensitivity and moderately weak water sensitivity damage. Although the liquid phase invasion depth is shallow and the water block damage is limited, the liquid phase and solid particles would enter the microfractures in the reservoir.The P-1 water-based drill-in fluid is compatible with the Chang 7 Formation shale reservoir which can meet the requirement of Chang 7 Formation shale damage controlling, the effect of water-based drill-in fluid on wellbore stability should be paid more attention. The diffusion coefficient of the shale decreases with the presence of water.A systematic damage evaluation method of working fluid considering the multi-mechanism and multi-scale mass transfer process of shale gas is needed to establish.

Description: This study examines the impact of financial development on carbon dioxide emissions in Nigeria over the period 1971–2014. Income per capita, energy consumption, exchange rate and urbanization are incorporated in the analysis. The empirical analysis based on linear and nonlinear autoregressive distributed lag techniques provides evidence of long-run relationship among the variables in Nigeria. The results in general show that financial development has significant asymmetric effects on carbon dioxide emissions in Nigeria. Both short-run and long-run analyses show that the impact of positive changes in financial development on carbon dioxide emissions is significantly different from that of negative changes. The results suggest that in Nigeria positive shocks in financial development have significant reducing effect on carbon dioxide emissions, while negative shocks in financial development have significant increasing effect on carbon dioxide emissions. The empirical results also show that the response of carbon dioxide emissions to negative shocks in financial development is stronger. Based on these findings, this study concludes that mitigation policies would need to incorporate strategies to strengthen the depth of financial intermediation in the Nigerian economy.

Description: Application of Weibull distribution in a generalized way to estimate wind potential cannot always be advisable. The novelty of this work is to estimate wind potential using Normal probability density function. A comparison of five probability distributions namely Normal, Gamma, Chi-Squared, Weibull, and Rayleigh was done using three performance evaluation criteria. Four years (2015–2018) hourly wind data at 50 m height at five stations near the coastline of Pakistan was used. It was found that normal distribution gives the best fit at each of these stations and against each evaluation criterion followed by Weibull distribution while Rayleigh distribution gives the poorest fit. Further energy generation by fifteen turbine models was calculated and GE 45.7 was found the best in terms of amount of energy generation and capacity factors while Vestas V42 shows the worst. However, GE/1.5 SL is the most economical while Vestas V63 is the least. Among five locations, Shahbandar is the best potential site while Manora is the least.