Unconventional Resources最新文献

The use of hydrothermal geothermal methods in Enhanced Geothermal Systems (EGS) presents challenges like reduced thermal storage life and high external energy consumption. Due to its stable heat production time and lower external energy demand, CO₂ has the potential to be substituted for H₂O. The research zone for this study was chosen to be located in the HDR reservoir in the Gonghe Basin of Qinghai. A three-dimensional discrete fracture model based on a thermal-hydraulic-mechanical coupling method is established, where numerical simulations are conducted using COMSOL software. The discussion focuses on the comparison of heat production effects between H₂O-EGS and CO₂-EGS in different injection and extraction scenarios are discussed. The results indicate that by lowering the injection temperature and increasing the injection rate, the EGS net heat production rate can be increased, but it also accelerates the heat breakthrough time and shortens the reservoir life. Although CO₂-EGS has a lower heat extraction rate in the early stage of thermal recovery than H₂O-EGS, it has a longer stable heat production time and a more energy-efficient heat production process. Therefore, compared to H₂O-EGS, CO₂-EGS has more economic and social benefits.

Different basins in China have proposed various reservoir grading standards for shale oil. Based on a comprehensive understanding of the basic characteristics of the shale oil reservoir in the Mahu Depression, this paper uses data from high-pressure mercury injection, physical properties, nuclear magnetic resonance, depletion development, and CO₂ displacement development tests to analyze the microscopic pore structure features of the Fengcheng Formation shale oil reservoir. On this basis, the classification boundaries of the pore throats in the shale oil reservoir were analyzed, and a reservoir grading standard suitable for the Fengcheng Formation shale was proposed: large pore throats (greater than 1000 nm), medium pore throats(100∼1000 nm), small pore throats (20∼100 nm), and ultra-small pore throats (less than 20 nm). The medium pore throat is the lower limit for depletion development, the small pore throat is the lower limit under CO₂ displacement conditions, and the ultra-small pore throat cannot be utilized under current conditions. The classification effect of the shale oil reservoir is verified using the production characteristics of Well MY1, the liquid production profile, and the results of geological "sweet spots" studies. The results show that the classification scheme for the microscopic pore throats of the Fengcheng Formation shale oil is reliable and feasible.

The stochastic nature of solar photovoltaics (PV), marked by high-frequency voltage fluctuations due to dynamic climatic conditions such as cloud cover and temperature variations, presents a significant challenge to power quality stability, especially in microgrids. This variability poses a threat to the stability of power electronic devices responsible for power control and monitoring, potentially compromising the power grid's stability. To address this challenge, energy storage systems (ESS) are commonly employed. In this study, we develop a hybrid energy storage system (HESS) incorporating a battery, supercapacitor, and fuel cell. The primary aim is to adjust the inverter voltage for the photovoltaic system using newly developed proportional-integral (PI) and model predictive control (MPC) controllers within the HESS framework. Importantly, this controller eliminates the need for precise knowledge of system parameters and offers robustness, insensitivity to parameter changes, and resilience to time-varying external disturbances, ensuring satisfactory performance. By mitigating power fluctuations, the generated power can be seamlessly integrated into the grid, significantly reducing costs associated with device damage in the power path.

Notably, we integrate the proposed photovoltaic system with an RLC series load using an IGBT inverter. To assess the performance of the HESS in the proposed photovoltaic system, four distinct scenarios are examined. These scenarios involve altering the PV system's location and testing two energy storage systems, namely the battery and fuel cell, which are separately designed components of the HESS for a 14-bus microgrid.

This work focuses on the recycling of waste groundnut oil as a potential feedstock for biodiesel production using activated coconut husk as a regenerating agent. The coconut husk was functionalized using organic acid. The properties of the functionalized coconut husk were investigated via instrumental analysis. Non-parametric modeling involving 2-degree isotherm models were used. The regeneration/recycling of the waste oil were done in batch mode examining key factors of temperature, time, concentration and dosage. Biodiesel was synthesized from recycled waste groundnut oil using transesterification reaction. The properties of biodiesel were examined using ASTM and AOAC official standards. Brunauer-Emmett-Teller surface analysis revealed the surface area of the adsorbent as 371.88 m²/g and a porosity distribution of 0.567 $\eta$ on the surface at a pH of 6.1. Batch mode analysis revealed that 97.5% of impurities was removed from waste groundnut oil under one batch process at 80 °C after 4 h with 6 g of the activated coconut husk. Langmuir isotherm model provided the best fit to the experimental data with adsorption capacity of 33.5 mg/g at R² of 0.996. Adsorption of waste groundnut oil impurities onto activated coconut husk was endothermic, as evidenced by the calculated ΔH of +2.7914 kJ/mol. A high cetane number of 48.4 obtained after transesterification is an indication of the good ignition quality of the obtained recycled waste groundnut oil methyl ester. Kinematic viscosity and acid value were revealed to be 4.65 mm² S⁻¹ and 0.31 mg KOH/g, while the calorific value stood at 38,053 kJ/kg. GC-MS analysis revealed a complex mixture of fatty acid methyl esters dominated by unsaturated fatty acids (58.78%). Recycling of waste cooking oil in this work using activated coconut husk demonstrated good quality as a regenerating agent. The properties of biodiesel obtained showed that it has all the good qualities comparable to other existing biodiesel based on the ASTM and AOAC official standards. More work on the recycling of other waste cooking oils for green energy synthesis to protect our environment from pollution emanating from the use of conventional petro-diesel and promote energy transition is highly recommended.

The development characteristics, scale and control factors of fractures are the core subjects of reservoir sweet spot prediction. The sandstone reservoir of the TX₂ gas reservoir in the Zhongjiang Gas Field is a typical low porosity and low permeability tight reservoir with strong heterogeneity, but relatively high-quality reservoirs can be found in different well areas and well segments. In this paper, taking the second Member of the Xujiahe Formation (TX₂) as an example, the control factors of fractures were systemically investigated via core observation, thin section, logging data, and fracture logging identifications. The results show that shear fractures are mainly developed in the cores, and they generally have high filling rate and poor effectiveness; microfractures can be found based on the vitrinite and cast thin section results. The intersection diagram (semi-quantitative) and the principal component and BP comprehensive identification (quantitative) methods can effectively identify different types of fractures. The combined application of principal component and BP comprehensive identification methods results in an 83.3 % fracture identification probability. Finally, we found that the development of fractures in TX₂ is comprehensively affected by lithology, rock thickness, porosity, and faults.

The vertical distribution of rocks’ radioactive heat production rate in the continental crust is the basis for exploring the deep thermal structure and explaining terrestrial heat flow distribution characteristics. In this paper, taking the Bohai Bay Basin as an example, according to the content of U, Th and K in the rocks and the lithologic composition of each structural layer of the crust, calculating the range of radioactive heat-generating elements in each structural layer. Then, systematically analyze the distribution characteristics of heat production rate in the crust. Finally, establish the vertical distribution model of heat production rate and discuss the relationship between heat flow and heat production rate. The results show that the rock heat production rate is mainly related to lithology. U and Th are primarily enriched in the upper crust with exponential distribution, while K content is unchanged. Under exponential crustal heat production rate distribution, the D_U, D_Th and D_A in the crust are 15.195 km, 15.29 km and 21.11 km, respectively. A linear relationship exists between heat flow and heat production rate but cannot infer the thermal condition of the middle and lower crust.

This study evaluates the productivity of ten major unconventional oil and gas plays in North America, emphasizing the role of completion, stimulation, and geological factors. The primary objective is to thoroughly assess the influence of various completion, stimulation, and geological parameters on well productivity while uncovering key insights and emerging trends unique to each play.

The dataset comprises 72,809 horizontal wells from 2015 to 2022 across 10 plays, encompassing 6 oil plays (Bakken, Delaware, Duvernay, Midland, Eagle Ford, and Scoop|Stack) and 4 gas plays (Haynesville, Barnett, Marcellus, and Utica). This study examines completion and fracture stimulation trends influencing the productivity of various plays, along with the significance of geological and mechanical properties.

Key findings reveal that while geological characteristics, such as total organic carbon (TOC) content and brittleness, significantly impact reservoir quality, operational practices like completion design and stimulation techniques, also play critical roles in well productivity. Key insights from the analysis challenge the traditional emphasis on TOC as a sole productivity indicator, which might not be as pronounced as commonly assumed. The analysis indicates that, contrary to common beliefs, plays exhibiting both a lower brittleness index and fewer wells per pad are associated with faster fracture growth rates. Adding more wells per pad increases the minimum horizontal stress in the neighborhood, which slows fracture growth and causes it to redirect upward. Horizontal spacing plays a crucial role in enhancing productivity, especially in less productive plays which benefit from denser well development. Co-completion of wells leads to superior performance by reducing fracture-driven interactions or “frac hits”. While longer laterals increase resource contact, productivity gains are not linear. The productivity impact of increasing clusters per stage is variable, potentially limited by the stress shadowing effect.

In summary, this study offers critical insights into the productivity-influencing factors across diverse shale plays, contributing to the optimization of well development and resource extraction in the future. This study not only provides technical guidance for the unconventional oil and gas developments in North America, but can also serve as a valuable guide for similar projects elsewhere.

Carbonate geothermal reservoirs are widespread in the Beijing-Tianjin-Hebei region, and acidification stands out as the most effective method to enhance the heat recovery potential of these reservoirs. To understand the propagation patterns of acidized wormholes in geothermal reservoirs, a pore-Darcy scale mathematical model of acidizing reactions in geothermal reservoirs has been established. A normal random distribution function is introduced to depict the reservoir's heterogeneity. Using the finite element method, the study simulated the impact of injection rate, acid concentration, diffusion coefficient, and acid-rock reaction rate on wormhole morphology. The findings indicate that the reaction is uniform in the early stage of acidification, becoming non-uniform in the late stage, ultimately forming distinctive wormhole structures. The acidification radius is more extensive along a particular direction post-acidification. Increasing the acid injection rate, acid concentration, and initial specific surface area proves beneficial in enhancing the acidizing effect. The outcomes of this study hold theoretical and technical significance for optimizing the thermal recovery efficiency of geothermal reservoirs.

Tight sandstone gas represents a crucial domain for augmenting reserves and boosting oil and gas production in the Ordos Basin. Currently, the primary focus for development lies in the Upper Paleozoic tight sandstone gas located in the southwestern Ordos basin. The gas reservoirs in this area present distinct characteristics, including significant burial depth exceeding 4000 m, modest-scale sand bodies, an average thin reservoir thickness of 5.8 m, and rapid lateral variations in sand body distribution. These factors contribute to challenges in establishing a clear correlation between reservoir scale and seismic reflection patterns, leading to uncertainties in reservoir prediction. In this study, three types of seismic reflection characteristics of the bottom interface associated with the development of the S₁³ reservoir in Block X have been summarized by using Forward modeling: (1) strong reflection of peaks on seismic sections; (2) weak reflection of troughs on seismic sections; and (3) strong reflection of complex waves with the bottom of the Shanxi Formation. The main factors that cause the above seismic reflection characteristics include the thickness of the lower coal seam, the spatial distribution and thickness of the reservoir. The above analysis breaks the inherent understanding that traditional strong seismic reflections are indicative of reservoir development, and instead, based on the three types of seismic reflection waveforms, waveform clustering is used to realize the differentiation of zones in the study area. Furthermore, combining with the facies-controlled high-resolution inversion, we achieved high-precision identification of tight sandstone reservoirs in Block X. This approach can be applied to similar reservoirs both at China and abroad.

This study presents a detailed investigation into the microfacies, geochemistry, and depositional environments of carbonate rocks from the southern Benue Trough and eastern Dahomey Basin. This analysis involved a combination of techniques, including X-ray diffraction, X-ray fluorescence, scanning electron microscopy with energy-dispersive X-ray spectroscopy and thin-section petrographic examination. Samples from the Igumale Formation of the southern Benue Trough and samples from Ewekoro Formation of the eastern Dahomey Basin were analyzed, offering insights into their mineral compositions, elemental distributions, and depositional environments. In each basin, two carbonate microfacies were identified. The two microfacies found in the Igumale Formation were recognized as micritic bioclastic packstone and sandy bioclastic wackestone. In the Ewekoro Formation, the two microfacies recognized were bioclastic packstone and sparitic peloidal wackestone. The X-ray diffraction analysis of samples from both basins revealed a dominance of calcite. X-ray fluorescence analysis showcased calcium oxide and calcium as the predominant oxide and elements in both basins with varying concentrations. Scanning electron microscopy-energy-dispersive X-ray spectroscopy results unveiled the elemental composition with calcium and silicon emerging as major constituents. The photomicrographs suggest distinct depositional conditions for both samples with those from the Igumale Formation showing evidence of shallow marine and that of the Ewekoro Formation suggesting calm marine environments comprised of fined grained carbonate rocks containing fossils. This study has provided detailed understanding on the nature, microfacies types, mineralogical composition, depositional environment and diagenetic processes of Cretaceous-Paleocene carbonate rocks within the studied basins.