Fracturing and thermal extraction optimization methods in enhanced geothermal systems

Fracture networks, fluid flow and heat extraction within fractures constitute pivotal aspects of enhanced geothermal system advancement. Conventional hydraulic fracturing in dry hot rock reservoirs typically requires high breakdown pressure and only produces a single major fracture morphology. Thus, it is imperative to explore better fracturing methods and consider more reasonable coupling mechanisms to improve the prediction efficiency. Cyclic fracturing using liquid nitrogen instead of water can generate more complex fracture networks and improve the fracturing performance. The simulation of fluid flow and heat transfer processes in the fracture network is crucial for an enhanced geothermal system, which requires a more comprehensive coupled thermo-hydro-mechanical-chemical model for matching, especially the characterization of coupling mechanism between the chemical and mechanical field. Based on the results of field engineering, laboratory experiments and numerical simulation, the optimum engineering scheme can be obtained by a multi-objective optimization and decision-making method. Furthermore, combining it with the deep-learning-based proxy model to achieve dynamic optimization with time is a meaningful future research direction.Document Type: PerspectiveCited as: Yang, R., Wang, Y., Song, G., Shi, Y. Fracturing and thermal extraction optimization methods in enhanced geothermal systems. Advances in Geo-Energy Research, 2023, 9(2): 136-140. https://doi.org/10.46690/ager.2023.08.0

Practice and understanding of deep coalbed methane massive hydraulic fracturing in Shenfu Block, Ordos Basin

The proven geological reserves of the Shenfu deep coalbed methane (CBM) field on the eastern margin of the Ordos Basin exceed 100 billion cubic meters. It is of great significance to realizing the efficient development of deep CBM in this region to ensure the national energy supply. However, the complexity of the geological environment which includes high stress, medium-high temperatures, low permeability, strong heterogeneity, and wide developed cleats and natural fractures, makes it challenging for the existed shallow and medium CBM fracturing techniques to be fully applicable to deep CBM resources. As a result, the stimulation scale and parameters for deep coalbed fracturing are still in the trial-and-error stage. In order to explore the stimulation techniques which are compatible with the geological conditions of deep coalbeds, the Shenfu block in the Ordos Basin was taken as the geological background and the large-scale hydraulic fracturing of deep coal seams was conducted as an engineering practice. The authors designed the idea of “Push the limit to the beyond + balanced propagation + effective support”, and proposed the massive hydraulic fracturing techniques based on “multi-stage multi-clusters with moderate-dense cutting + perforation with equal apertures, deep penetration and limited flow + integrated variable viscosity (rock breaking by higher viscous slick water + complex fracture network generating by lower viscous slick water) + high pumping rate with high proppant concentration + pre-acid treatment to reduce the breakdown pressure + graded proppants with multiple sizes to support fractures”. Then, the authors put forward an integrated “Geology-Engineering-AI” workflow to perform post-frac analysis, through double matching and correcting the fracturing pumping pressure and production rate automatically, accurately characterized the stimulated reservoir volume (SRV) and drained rock volume (DRV), and predicted the estimated ultimate recovery (EUR) under different fracturing scales and well types. Finally, by statistically analyzing the gas production characteristics of multiple wells in the Shenfu block and utilizing the random forest method, the primary controlling factors affecting the production capacity of deep CBM were quantitatively analyzed. The results demonstrate that after reservoir stimulation, directional wells can achieve a maximum daily gas production rate exceeding 10 000 m3/d, while horizontal wells can achieve a maximum daily gas production rate exceeding 20 000 m3/d. It indicates that the deep coal beds have good fracturing properties and great development potential. The primary impact factors for peak gas production rate are gas content, coalbed thickness and proppant concentration, while the major impact factors for cumulative gas production include gas content, proppant concentration, and total volume of proppants

A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks

A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A “hump” that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the “hump” can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the “hump” more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production

A Theoretical Analysis of Pore Size Distribution Effects on Shale Apparent Permeability

Apparent permeability is an important input parameter in the simulation of shale gas production. Most apparent permeability models assume a single pore size. In this study, we develop a theoretical model for quantifying the effect of pore size distribution on shale apparent permeability. The model accounts for the nonuniform distribution of pore sizes, the rarefaction effect, and gas characteristics. The model is validated against available experimental data. Theoretical calculations show that the larger the pore radius, the larger the apparent permeability. Moreover, the apparent permeability increases with an increase in the width of pore size distribution, with this effect being much more pronounced at low pressure than at high pressure

Pore-scale analysis of coal structure and mechanical properties evolution through liquid nitrogen thermal shock

Liquid nitrogen fracturing is one of the potential feasible technologies for improving the stimulation efficiency of coalbed methane (CBM) reservoirs. At present, the visualization of pore-throat connectivity and microscopic seepage characteristics in coal rocks under liquid nitrogen thermal shock is still lack of studying. Hence, the influence of liquid nitrogen thermal shock on the micro-nano pore structure and mechanical property of coal rocks are not understood clearly. In order to provide theoretical basis for the stimulation behavior of liquid nitrogen fracturing in coal beds, this paper investigates the change of micro-nano pore structure and mechanical property of coal rocks before and after liquid nitrogen treatment means of CT scanning and atomic force microscope (AFM). In addition, the influence of liquid nitrogen thermal shock on the seepage routes of coal rock are revealed. The following research results can be obtained. First, the number and scales of pores in the coal increase after liquid nitrogen thermal shock. In this experiment, porosity is increased by 200%, micro-fracture is dominant and its volume proportion is increased to 90.0% from 7.7% before liquid nitrogen treatment. Second, the three-dimensional pore structure reconstruction model obtained by CT shows that after the liquid nitrogen treatment, the number, total length and total volume of throats in the coal rock are increased by 170%, 140% and 130% and the pore connectivity is improved greatly. Third, after liquid nitrogen treatment, the sample's absolute permeability is improved significantly. In this experiment, the absolute permeability of coal after liquid nitrogen treatment is 77 times higher than that before liquid nitrogen cooling. The micro-fractures induced by thermal stress are the main percolation routes in coal after liquid nitrogen cooling. Fourth, pores and fractures are newly formed on both matrix and mineral domains, and the surface roughness is increased. In the meantime, the elastic modulus in matrix and mineral domains of coal drops, and the average elastic modulus drops by 81% and 91%, respectively. In conclusion, liquid nitrogen thermal shock leads to the increase of microscopic defects in coal and the deterioration of mechanical property. Liquid nitrogen fracturing is expected to be a new kind of efficient and green CBM reservoir stimulation technology

Antioxidant Effect of a Marine Oligopeptide Preparation from Chum Salmon (Oncorhynchus keta) by Enzymatic Hydrolysis in Radiation Injured Mice

Abstract: Marine oligopeptide preparation (MOP) obtained from Chum Salmon (Oncorhynchus keta) by the method of enzymatic hydrolysis, has been found to possess a radioprotective property through stimulation of the radiation-induced immunosuppression. The current study aimed to further investigate the free radicals scavenging and antioxidant effects of MOP in radiation injured mice. Female ICR mice (6–8 weeks old) were randomly divided into 5 groups, i.e., blank control, irradiation control and MOP (0.225, 0.450 and 1.350 g/kg body weight) plus an irradiation-treated group. The result revealed that MOP significantly increased the white blood cell counts after irradiation, and lessened the radiation-induced oxidative damage. These effects may be caused by augmentation of the activities of antioxidant enzymes, such as SOD and GSH-Px, reduction of the lipid peroxidation (MDA level) in liver, and protection against radiation-induced apoptosis. Therefore, we propose that MOP be used as an ideal antioxidant to alleviate radiation-induced oxidation damage in cancer patients. Keywords: bioactive peptide; GSH-Px; MDA; radioprotective; SODMar. Drugs 2011, 9 2305 1

The Protective Effects and Potential Mechanisms of Ligusticum chuanxiong: Focus on Anti-Inflammatory, Antioxidant, and Antiapoptotic Activities

Ligusticum chuanxiong (LC) is a Chinese materia medica which is widely used in clinical settings to treat headaches, blood extravasation, and arthritis. Recent studies demonstrate that LC possesses versatile pharmacological functions, including antiatherosclerosis, antimigraine, antiaging, and anticancer properties. Moreover, LC also shows protective effects in the progression of different diseases that damage somatic cells. Oxidative stress and inflammation, which can induce somatic cell apoptosis, are the main factors associated with an abundance of diseases, whose progresses can be reversed by LC. In order to comprehensively review the molecular mechanisms associated with the protective effects of LC, we collected and integrated all its related studies on the anti-inflammatory, antioxidant, and antiapoptotic effects. The results show that LC could exhibit the mentioned biological activities by modulating several signaling pathways, specifically the NF-κB, Nrf2, protein kinase, and caspase-3 pathways. In future investigations, the pharmacokinetic properties of bioactive compounds in LC and the signaling pathway modulation of LC could be focused

Bubble dynamics characteristics and influencing factors on the cavitation collapse intensity for self-resonating cavitating jets

Based on bubble dynamics theory, a mathematic model describing the cavitation bubble size variation in the flow field of self-resonating cavitating jet was developed considering the pressure field and mass and heat exchange between cavitation bubble and ambient fluid. With this model, the influence factors on the cavitation intensity are investigated. The results show that the destructiveness of cavitating jet in breaking rocks depends on the bubble's first collapse, with decreasing intensity in the subsequent collapses. The self-resonating effect significantly enhances the cavitation intensity by promoting the collapse pressure and elongating its duration. Hydraulic parameters are proven to be the dominating factors influencing cavitation intensity: while collapse intensity monotonously increases with jet velocity, there exists an optimum ambient pressure where highest collapse intensity can be achieved. Conversely, the fluid properties show minor influences: cavitation intensity only slightly decreases with the increasing of fluid's density and barely changes with the variation of viscosity and surface tension. The results from this investigation help to uncover the mechanism of the enhanced erosion potential of self-resonating cavitating jet. The conclusions can be used to further improve the performance of self-resonating cavitating jet in field applications. Key words: self-resonating cavitating jet, cavitating bubble, collapse intensity, hydraulic parameters, fluid propertie

Factors that influence the choice of long-acting reversible contraceptive use among adolescents post-abortion in Chongqing, China: a cross-sectional study

Background Induced abortion can seriously harm the physical and mental health of adolescent women. Long-acting reversible contraception (LARC) can effectively reduce unplanned pregnancies and prevent repeated abortions among adolescents. This study aimed to analyse the factors affecting the choice of LARC among adolescents in Chongqing of China.Methods A total of 555 adolescents who underwent induced abortions for unplanned pregnancies between January 2019 and October 2021 were selected as study subjects. Logistic regression analysis was used to determine the factors affecting adolescent LARC choices following induced abortions.Results The factors that affected adolescent LARC choices included an average monthly income ≥ ¥3000 (OR = 3.432, 95% CI: 1.429∼8.244), history of previous abortions (OR = 3.141, 95% CI: 1.632∼6.045), worrying about unplanned pregnancy (OR = 0.365, 95% CI: 0.180∼0.740), parental support for using LARC (OR = 3.549, 95% CI: 1.607∼7.839), sexual partners’ support for using LARC (OR = 2.349, 95% CI: 1.068∼5.167), concerns about using LARC (OR = 0.362, 95% CI: 0.176∼0.745), and willingness to use free IUDs (OR = 13.582, 95% CI: 7.173∼25.717).Conclusion Cost is one of the factors affecting LARC choices. Parents and sexual partners may play important role in the choice of LARC

Lung fluid biomarkers for acute respiratory distress syndrome: a systematic review and meta-analysis

Abstract Background With the development of new techniques to easily obtain lower respiratory tract specimens, bronchoalveolar lavage fluid and other lung fluids are gaining importance in pulmonary disease diagnosis. We aimed to review and summarize lung fluid biomarkers associated with acute respiratory distress syndrome diagnosis and mortality. Methods After searching PubMed, Embase, Web of Science, and the Cochrane Library for articles published prior to January 11, 2018, we performed a meta-analysis on biomarkers for acute respiratory distress syndrome diagnosis in at-risk patients and those related to disease mortality. From the included studies, we then extracted the mean and standard deviation of the biomarker concentrations measured in the lung fluid, acute respiratory distress syndrome etiologies, sample size, demographic variables, diagnostic criteria, mortality, and protocol for obtaining the lung fluid. The effect size was measured by the ratio of means, which was then synthesized by the inverse-variance method using its natural logarithm form and transformed to obtain a pooled ratio and 95% confidence interval. Results In total, 1156 articles were identified, and 49 studies were included. Increases in total phospholipases A2 activity, total protein, albumin, plasminogen activator inhibitor-1, soluble receptor for advanced glycation end products, and platelet activating factor-acetyl choline were most strongly associated with acute respiratory distress syndrome diagnosis. As for biomarkers associated with acute respiratory distress syndrome mortality, interleukin-1β, interleukin-6, interleukin-8, Kerbs von Lungren-6, and plasminogen activator inhibitor-1 were significantly increased in the lung fluid of patients who died. Decreased levels of Club cell protein and matrix metalloproteinases-9 were associated with increased odds for acute respiratory distress syndrome diagnosis, whereas decreased levels of Club cell protein and interleukin-2 were associated with increased odds for acute respiratory distress syndrome mortality. Conclusions This meta-analysis provides a ranking system for lung fluid biomarkers, according to their association with diagnosis or mortality of acute respiratory distress syndrome. The performance of biomarkers among studies shown in this article may help to improve acute respiratory distress syndrome diagnosis and outcome prediction