Concerns about the application of resistance exercise with blood-flow restriction and thrombosis risk in hemodialysis patients

Background:Hemodialysis(HD) per se is a risk factor for thrombosis.Considering the growing body of evidence on blood-flow restriction(BFR) exercise in HD patients,identification of possible risk factors related to the prothrombotic agent D-dimer is required for the safety and feasibility of this training model.The aim of the present study was to identify risk factors associated with higher D-dimer levels and to determine the acute effect of resistance exercise(RE) with BFR on this molecule.Methods:Two hundred and six HD patients volunteered for this study(all with a glomerular filtration rate of <15 mL/min/1.73 m2).The RE+BFR session consisted of 50% arterial occlusion pressure during 50 min sessions of HD(intradialytic exercise).RE repetitions included concentric and eccentric lifting phases(each lasting 2 s) and were supervised by a strength and conditioning specialist.Results:Several variables were associated with elevated levels of D-dimer,including higher blood glucose,citrate use,recent cardiovascular events,recent intercurrents,higher inflammatory status,catheter as vascular access,older patients(>70 years old),and HD vintage.Furthermore,RE+BFR significantly increases D-dimer after 4 h.Patients with borderline baseline D-dimer levels(400-490 ng/mL) displayed increased risk of elevating D-dimer over the normal range(≥500 ng/mL).Conclusion:These results identified factors associated with a heightened prothrombotic state and may assist in the screening process for HD patients who wish to undergo RE+BFR.D-dimer and/or other fibrinolysis factors should be assessed at baseline and throughout the protocol as a precautionary measure to maximize safety during RE+BFR.

Mechanisms underlying the role of endoplasmic reticulum stress in the placental injury and fetal growth restriction in an ovine gestation model

Background Exposure to bisphenol A(BPA),an environmental pollutant known for its endocrine-disrupting properties,during gestation has been reported to increase the risk of fetal growth restriction(FGR)in an ovine model of pregnancy.We hypothesized that the FGR results from the BPA-induced insufficiency and barrier dysfunction of the placenta,oxidative stress,inflammatory responses,autophagy and endoplasmic reticulum stress(ERS).However,precise mechanisms underlying the BPA-induced placental dysfunction,and subsequently,FGR,as well as the potential involvement of placental ERS in these complications,remain to be investigated.Methods In vivo experiment,16 twin-pregnant(from d 40 to 130 of gestation)Hu ewes were randomly distributed into two groups(8 ewes each).One group served as a control and received corn oil once a day,whereas the other group received BPA(5 mg/kg/d as a subcutaneous injection).In vitro study,ovine trophoblast cells(OTCs)were exposed to 4 treatments,6 replicates each.The OTCs were treated with 400μmol/L BPA,400μmol/L BPA+0.5μg/m L tunicamycin(Tm;ERS activator),400μmol/L BPA+1μmol/L 4-phenyl butyric acid(4-PBA;ERS antagonist)and DMEM/F12 complete medium(control),for 24 h.Results In vivo experiments,pregnant Hu ewes receiving the BPA from 40 to 130 days of pregnancy experienced a decrease in placental efficiency,progesterone(P4)level and fetal weight,and an increase in placental estrogen(E2)level,together with barrier dysfunctions,OS,inflammatory responses,autophagy and ERS in type A cotyledons.In vitro experiment,the OTCs exposed to BPA for 24 h showed an increase in the E2 level and related protein and gene expressions of autophagy,ERS,pro-apoptosis and inflammatory response,and a decrease in the P4 level and the related protein and gene expressions of antioxidant,anti-apoptosis and barrier function.Moreover,treating the OTCs with Tm aggravated BPA-induced dysfunction of barrier and endocrine(the increased E2 level and decreased P4 level),OS,inflammatory responses,autophagy,and ERS.However,treating the OTCs with 4-PBA reversed the counteracted effects of Tm mentioned above.Conclusions In general,the results reveal that BPA exposure can cause ERS in the ovine placenta and OTCs,and ERS induction might aggravate BPA-induced dysfunction of the placental barrier and endocrine,OS,inflammatory responses,and autophagy.These data offer novel mechanistic insights into whether ERS is involved in BPA-mediated placental dysfunction and fetal development.

Effects of maternal methyl donor intake during pregnancy on ileum methylation and function in an intrauterine growth restriction pig model

Background Intrauterine growth retardation(IUGR)affects intestinal growth,morphology,and function,which leads to poor growth performance and high mortality.The present study explored whether maternal dietary methyl donor(MET)supplementation alleviates IUGR and enhances offspring’s growth performance by improving intestinal growth,function,and DNA methylation of the ileum in a porcine IUGR model.Methods Forty multiparous sows were allocated to the control or MET diet groups from mating until delivery.After farrowing,8 pairs of IUGR and normal birth weight piglets from 8 litters were selected for sampling before suckling colostrum.Results The results showed that maternal MET supplementation tended to decrease the IUGR incidence and increased the average weaning weight of piglets.Moreover,maternal MET supplementation significantly reduced the plasma concentrations of isoleucine,cysteine,urea,and total amino acids in sows and newborn pig-lets.It also increased lactase and sucrase activity in the jejunum of newborn piglets.MET addition resulted in lower ileal methionine synthase activity and increased betaine homocysteine S-methyltransferase activity in the ileum of newborn piglets.DNA methylation analysis of the ileum showed that MET supplementation increased the methyla-tion level of DNA CpG sites in the ileum of newborn piglets.Down-regulated differentially methylated genes were enriched in folic acid binding,insulin receptor signaling pathway,and endothelial cell proliferation.In contrast,up-regulated methylated genes were enriched in growth hormone receptor signaling pathway and nitric oxide biosyn-thetic process.Conclusions Maternal MET supplementation can reduce the incidence of IUGR and increase the weaning litter weight of piglets,which may be associated with better intestinal function and methylation status.

Associations of serum D-dimer and glycosylated hemoglobin levels with third-trimester fetal growth restriction in gestational diabetes mellitus

BACKGROUND Gestational diabetes mellitus(GDM)is a special type of diabetes that commonly occurs in women during pregnancy and involves impaired glucose tolerance and abnormal glucose metabolism;GDM is diagnosed for the first time during pregnancy and can affect fetal growth and development.AIM To investigate the associations of serum D-dimer(D-D)and glycosylated hemoglobin(HbA1c)levels with third-trimester fetal growth restriction(FGR)in GDM patients.METHODS The clinical data of 164 pregnant women who were diagnosed with GDM and delivered at the Obstetrics and Gynecology Hospital of Fudan University from January 2021 to January 2023 were analyzed retrospectively.Among these women,63 whose fetuses had FGR were included in the FGR group,and 101 women whose fetuses had normal body weights were included in the normal body weight group(normal group).Fasting venous blood samples were collected from the elbow at 28-30 wk gestation and 1-3 d before delivery to measure serum D-D and HbA1c levels for comparative analysis.The diagnostic value of serum D-D and HbA1c levels for FGR was evaluated by receiver operating characteristic analysis,and the influencing factors of third-trimester FGR in GDM patients were analyzed by logistic regression.RESULTS Serum fasting blood glucose,fasting insulin,D-D and HbA1c levels were significantly greater in the FGR group than in the normal group,while the homeostasis model assessment of insulin resistance values were lower(P<0.05).Regarding the diagnosis of FGR based on serum D-D and HbA1c levels,the areas under the curves(AUCs)were 0.826 and 0.848,the cutoff values were 3.04 mg/L and 5.80%,the sensitivities were 81.0%and 79.4%,and the specificities were 88.1%and 87.1%,respectively.The AUC of serum D-D plus HbA1c levels for diagnosing FGR was 0.928,and the sensitivity and specificity were 84.1%and 91.1%,respectively.High D-D and HbA1c levels were risk factors for third-trimester FGR in GDM patients(P<0.05).CONCLUSION D-D and HbA1c levels can indicate the occurrence of FGR in GDM patients in the third trimester of pregnancy to some extent,and their combination can be used as an important index for the early prediction of FGR.

The Effect of Macronutrient Restrictions on Gut Microbiome and Biochemical Parameters of Wistar Albino Rats

Macronutrients serve as a source of energy for both gut microbiota and its host. An increase or decrease in macronutrients can either increase or decrease the composition of gut microbiota, leading to gut dysbiosis which has been implicated in many diseases state including non-communicable diseases. To achieve this, seven diets were formulated by restricting 60% of each macronutrient. These diets were fed on 42 albino rats (Wistar), divided into 7 groups of 6 rats each. Group 1 was fed on a normal laboratory chow diet (ND), group 2 received a fat-restricted diet (FRD), group 3 received a protein-restricted diet, (PFD), group 4 received a carbohydrate-restricted diet (CRD), group 5 received a protein and fat-restricted diet (PFRD), group 6 re-ceived a carbohydrate and fat-restricted diet (CFRD) and group 7 received a carbohydrate and protein-restricted diet (CPRD). Feed and water intake were given ad libitum and daily weight and food intake were recorded. The experiment went on for 4 weeks after which animals were sacrificed and intestinal content and blood were collected for analysis (gut microbial composition, glucose, insulin levels, serum lipid, and enzyme). Compared to the control group results showed a decrease in Bacteroides (40.50 - 14.00 CFU), HDL (68.20 - 40.40 mg/dl), and AST (66.62 - 64.74 U/L) in FRD. An increase in AST (66.6 - 69.43 U/L), Bifidobacterial (59.50 - 92.00 CFU) and decreased Bacteroides (40.5 - 19.5 CFU) for PRD was also recorded. CRD reduced Lactobacillus (73 - 33.5 CFU), total bacterial count (129 - 48 CFU), HDL (68.2 - 30.8 mg/dl), and cholesterol (121.44 - 88.65 mg/dl) whereas intestinal composition of E. coli (30.5 - 51.5 CFU) increased. PFRD increased Lactobacillus (73.00 - 102.5 CFU), Bifidobacterial (59.5 - 100 CFU), HDL (68.2 - 74.7 mg/dl), and Triglyceride (111.67 - 146.67 mg/dl) concentration. Meanwhile, a reduction in Bifidobacterial (59.5 - 41.5 CFU), and an increasing of AST (66.62 - 70.30 U/l) were recorded for CFRD. However, Bacteroides (40.5 69.5 CFU), LDL (30.95 - 41.98 mg/dl) increased and Bifidobacterial (59.5 - 38.00 CFU) and HDL (68.2 - 53.5 mg/dl) decreased for CPRD. This work, therefore, concludes that macronutrient restriction causes significant changes in serum marker and enzyme profile, and gut microbial composition which can cause gut dysbiosis and later on could expose the host to inflammatory diseases in the long run.

Caloric restriction-mimetics for the reduction of heart failure risk in aging heart: with consideration of gender-related differences

The literature is full of claims regarding the consumption of polyphenol or polyamine-rich foods that offer some protection from developing cardiovascular disease(CVD). This is achieved by preventing cardiac hypertrophy and protecting blood vessels through improving the function of endothelium. However, do these interventions work in the aged human hearts? Cardiac aging is accompanied by an increase in left ventricular hypertrophy, along with diastolic and systolic dysfunction. It also confers significant cardiovascular risks for both sexes. The incidence and prevalence of CVD increase sharply at an earlier age in men than women. Furthermore, the patterns of heart failure differ between sexes, as do the lifetime risk factors. Do caloric restriction(CR)-mimetics, rich in polyphenol or polyamine, delay or reverse cardiac aging equally in both men and women? This review will discuss three areas:(1) mechanisms underlying age-related cardiac remodeling;(2) gender-related differences and potential mechanisms underlying diminished cardiac response in older men and women;(3) we select a few polyphenol or polyamine rich compounds as the CRmimetics, such as resveratrol, quercetin, curcumin, epigallocatechin gallate and spermidine, due to their capability to extend health-span and induce autophagy. We outline their abilities and issues on retarding aging in animal hearts and preventing CVD in humans. We discuss the confounding factors that should be considered for developing therapeutic strategies against cardiac aging in humans.

Long-term implications of fetal growth restriction

Fetal growth restriction(FGR),or intrauterine growth restriction(IUGR),is a complication of pregnancy where the fetus does not achieve its genetic growth potential.FGR is characterized by a pathological retardation of intrauterine growth velocity in the curve of intrauterine growth.However,the FGR definition is still debated,and there is a lack of a uniform definition in the literature.True IUGR,compared to constitutional smallness,is a pathological condition in which the placenta fails to deliver an adequate supply of oxygen and nutrients to the developing fetus.Infants with IUGR,compared to appropriately grown gestational age infants,have a significantly higher risk of mortality and neonatal complications with long-term consequences.Several studies have demonstrated how suboptimal fetal growth leads to long-lasting physiological alterations for the developing fetus as well as for the newborn and adult in the future.The long-term effects of fetal growth retardation may be adaptations to poor oxygen and nutrient supply that are effective in the fetal period but deleterious in the long term through structural or functional alterations.Epidemiologic studies showed that FGR could be a contributing factor for adult chronic diseases including cardiovascular disease,metabolic syndrome,diabetes,respiratory diseases and impaired lung function,and chronic kidney disease.In this review we discussed pathophysiologic mechanisms of FGR-related complications and potential preventive measures for FGR.

The effect of caloric restriction on genetical pathways

Energy restriction is defined as reducing nutrient intake without dragging the organism into malnutrition. Energy restriction is preferred because it is a non-genetic intervention that increases life expectancy. Nicotinamide adenine dinucleotide(NAD~+)and adenosine monophosphate(AMP)levels, which are the indicators of intracellular energy deficiency, increase with energy restriction. The increase in NAD~+ level stimulates sirtuin(SIRT)enzymes, and the increase in AMP level stimulates AMP-activated protein kinase(AMPK). Various mechanisms are regulated by stimulating these enzymes. By Forkhead box O(FoxO)transcription factors, the ability of resistance to oxidative stress increases, and antioxidant genes, DNA repair, and autophagy genes are stimulated. Apoptosis is induced by stimulation of the p53 protein, and tumor growth is suppressed by the disruption of aging cells. The suppression of phosphoinositide 3-kinase(PI3K)-/-Akt, and therefore mTOR signal stimulates autophagy and mitophagia, and cleanses damaged cells and organelles. Mitochondrial biogenesis is stimulated, antioxidant capacity increases, and inflammatory response decreases. Adipose tissue and lipid metabolism are regulated by the regulation of fatty acid synthesis and oxidation. As a consequence, the effects of caloric restriction on cellular metabolism are regulated through the genetic pathways.

Calorie restriction potentiates epigallocatechin-3-gallate-mediated Nrf2 activation in hepatocytes of aged rats

Objective:To explore the combinatorial effect of epigallocatechin-3-gallate(EGCG)and calorie restriction on activation of nuclear factor erythroid 2-related factor 2(Nrf2),a transcription factor involved in the antioxidant defense system of aged rats.Methods:Aged male Wistar rats were calorie-restricted and treated with EGCG orally for 45 days.The initial body weight of aged rats was recorded,and the final body weight was measured at the end of the experimental period.Serum lipid and lipoprotein status,oxidative stress markers such as free radicals and malondialdehyde levels,and reduced glutathione were assessed.In addition,RT-PCR and Western blotting analyses were performed.Results:Calorie restriction potentiated the effect of EGCG on enhancing antioxidant status,improving the levels of serum lipid and lipoproteins,upregulating Nrf2 and Bcl2,and downregulating Keap1,cullin3,Bax and cytochrome c in aged rats.Conclusions:Calorie restriction can promote EGCG-mediated Nrf2 activation in aged rats.This preliminary finding paves the way for a combinatory approach to replenishing the antioxidant status during aging,thereby reducing the risk for age-associated degenerative diseases.

Dietary Vitamin K Restriction and Effectiveness of Vitamin K Antagonists Prescribed at the CNHU-HKM University Cardiology Clinic/BENIN

Introduction: Their efficacy in preventing thrombotic and embolic events has been proven in numerous studies, but their narrow therapeutic index requires particular vigilance, especially in terms of biology. In addition, treatment-related hemorrhagic complications are not uncommon. This study explores the influence of dietary vitamin K restriction on the efficacy of antivitamin K treatment at the University Cardiology Clinic of CNHU-HKM. Methods: Cross-sectional and descriptive study that took place from 25 April to 29 August 2019. Patients’ dietary behaviors and successive INR values were collected. Information on dietary intake was obtained by 2 non-consecutive 24-hour recalls. The effectiveness of VKA treatment was assessed by the “Time in Therapeutic Range” (TTR) of the INR. VKA treatment was considered effective for a TTR greater than 65%. Results: At the end of this study, 40 patients were surveyed. The mean age of the participants was 58.05 years ± 13.32 years, with a sex ratio of 1.35. Complete arrhythmia due to atrial fibrillation was the main indication for VKA treatment (37.50%) and fluindione was the most commonly prescribed drug (77.50%). The duration of treatment was less than or equal to 2 years in 47.5% of the subjects surveyed. Before starting treatment, 85% of patients received advice on restricting vitamin K-rich foods, and 45% of patients reported “food burnout” after a period of compliance with the restriction. The majority of respondents (97.50%) complied with the restriction on vitamin K-rich foods. All respondents had high energy intakes and a poor distribution of macronutrients, with a predominance of carbohydrates and proteins. 2.5% of respondents were on effective anti-vitamin K therapy with a TTR of over 65%. Conclusion: Restriction of vitamin K-rich foods is not conducive to effective treatment with vitamin K antagonists.

Effect of Sleep Hygiene Orientation on Social Cognition Impairments Due to Chronic Sleep Restriction in Mexican Medical Residents

Introduction: Sleep is critical to human physiological function, cognitive performance, and emotional regulation. Healthcare personnel, especially physicians, are chronically exposed to long working hours, which are often accompanied by decreased sleep time. Clinical evidence indicates that these conditions affect their cognitive function and professional practice, but researchers in the field have not sufficiently explored the possible effects of reductions in sleep time on social cognition. Objective: The aim of this is to further explore the effects of sleep restriction among medical residents, the specific impairments in social cognition that it produces, and the effects of a sleep hygiene orientation on those impairments. Method: There were 124 medical residents (50 males, 74 females) who completed a daily sleep/work log, a battery of sleep tests/questionnaires, and neuropsychological evaluations. The participants then received a short course (8 hours) on basic concepts of sleep hygiene and sleep psychoeducation. Once the course was completed, participants filled out the questionnaires again. Results: The results indicate that sleep disturbances in medical residents were associated with severe neurocognitive and social cognition impairments. After the sleep hygiene intervention, neuropsychological function and sleep parameters improved, awareness increased, and social cognition performance significantly improved. Conclusion: Using sleep psychoeducation and sleep hygiene intervention in medical residents is a simple strategy to mitigate the effects of sleep restriction.

Unenumerated Rights Clauses and the System of Restriction on Fundamental Rights——Another Construction Plan for Article 51 of the Constitution of PRC

According to constitutional jurisprudence in China,Article 51 of the Constitution is an unenumerated restrictive clause.Such theoretical construction fails to justify the differentiated restrictions established in the Constitution and makes it difficult to explain the constitutional status of human dignity. Article 51 implies the possibility of other theoretical constructions. It is not an unenumerated restriction clause but an unenumerated rights clause. It aims to provide guarantees for general freedom of action not enumerated in the Constitution rather than restricting fundamental rights. The actual benefit of this kind of theoretical construction lies in that it can establish the basis of the constitutional text for general freedom of action and promote the people’s correct understanding of the model of restriction on fundamental rights established by the Constitution of PRC.

欧盟PFAS限制提案解读及其对制冷空调行业影响与应对

在《〈关于消耗臭氧层物质的蒙特利尔议定书〉基加利修正案》的履约和“双碳”目标的双重驱动下,制冷剂替代是制冷空调领域最为关注的热点之一。采用热物性相近的低GWP的HFOs制冷剂和天然制冷剂作为替代品,实现HFCs的削减被认为是较为合适的替代技术路线;但随着2023年2月欧盟出台的PFAS限制提案,引发了对HFOs制冷剂替代前景的担忧,这可能影响全球制冷剂替代发展。因此,首先对PFAS物质进行了介绍,分析了含氟制冷剂与PFASs的关系,并对PFAS法案的形成脉络和关键内容进行了解读,总结了不同领域对此的观点,希望对未来制冷剂替代方案的制定提供一定思辨意义和参考价值。

开放大学发展社区教育制约因素与对策研究

针对地方开放大学发展社区教育面临思想认识不到位、办学体系不健全、运作模式滞后、办学经费匮乏和师资队伍不足等问题及制约因素,从提高政治站位、创新办学理念、实现社区教育和老年教育融合发展等方面提出发展社区教育的对策与建议,为办好社区教育、推进学习型社会做出新贡献。

基于CiteSpace和VOSviewer可视化软件对饮食限制调控炎症的研究现状与热点分析

目的:基于CiteSpace和VOSviewer可视化软件对饮食限制(DR)调控炎症文献进行定量可视化分析,探索DR调控炎症领域的研究热点和趋势。方法:检索2010年1月1日至2022年9月29日Web of Science核心数据库中收录的DR调控炎症相关文献共1678篇,经筛查最终获得1344篇,使用CiteSpace和VOSviewer可视化软件对检索到的文献数据进行年发文量、国家、机构、作者、被引频次和关键词的定量和可视化分析。结果:最终获得的1344篇文献年发文量总体呈上升趋势,文献最高被引频次为1676次,美国(481篇)是出产文献数量最多的国家,中国(181篇)位居第二。DR调控炎症领域研究热点集中在热量限制(CR)、生酮饮食、衰老、代谢性疾病、脂肪组织及肠道菌群等方面。结论:DR调控炎症愈来愈受到国际和国内研究者青睐,未来研究热点可能是CR模拟物(CRM)、肠道菌群、神经退行性疾病和心血管疾病,总体研究趋势为进一步明确DR的抗炎机制,寻找新的治疗靶点,将更多经过体外和动物模型证实的有效方案进行更严格的临床试验。

miR-34c-5p靶向poFUT1对胎盘血管形成的影响

目的:探讨miR-34c-5p与poFUT1的靶向关系及对胎盘血管形成的影响。方法:利用ENCORI数据库预测miR-34c-5p与poFUT1的结合位点,采用双荧光素酶报告实验验证。随机选取2023年4至10月在郑州大学第三附属医院住院的胎儿生长受限(FGR)孕妇20例(FGR组),选择同期正常孕妇20例为对照。采用实时荧光定量PCR法检测两组胎盘组织中miR-34c-5p和poFUT1 mRNA的表达。取脐静脉内皮细胞,分组转染miR-34c-5p模拟物及其对照(NC)、miR-34c-5p抑制物及其NC、si-poFUT1 NC、si-poFUT1、si-poFUT1+miR-34c-5p抑制物,采用CCK-8法、Transwell实验以及成管实验检测细胞转染24、48、72、96 h后的增殖能力,转染48 h后的侵袭能力和成管能力。结果:FGR组和对照组胎盘组织中miR-34c-5p表达水平分别为(1.57±0.39)、(1.09±0.18),poFUT1 mRNA表达水平分别为(0.51±0.17)、(1.06±0.13),FGR组胎盘组织中miR-34c-5p表达水平高于对照组,poFUT1 mRNA表达水平低于对照组(P<0.05)。与miR-34c-5p模拟物NC组比较,模拟物组侵袭细胞数和管腔节点数减少,细胞增殖活性降低(P<0.05)。与miR-34c-5p抑制物NC组比较,抑制物组侵袭细胞数和管腔节点数增加,细胞增殖活性升高(P<0.05)。与si-poFUT1 NC组相比,si-poFUT1组侵袭细胞数和管腔节点数减少,细胞增殖活性降低(P<0.05),而si-poFUT1+miR-34c-5p抑制物组上述变化较si-poFUT1组部分逆转(P<0.05)。结论:miR-34c-5p可能通过调控poFUT1影响血管内皮细胞功能,从而影响胎盘的血管形成,参与FGR的发生。

我国限制使用的兽药在食品动物中的残留概况

从我国食品动物禁用、停用、特定时期不得使用以及允许使用但不得检出等层面,对我国兽药使用的限制、相关残留检测方法标准适用范围以及相关问题的分析和建议进行综述,以期为养殖业规范用药、食品安全监管部门政策制定和调整、科研机构针对不得检出兽药残留标准相关研究的开展提供参考。

价值均衡视角下宅基地使用权继承纠纷的裁判规则构建

现阶段宅基地使用权继承纠纷解决存在司法处理态度不一、缺少统一立法规范的实践困境。根本原因在于宅基地使用权兼具身份价值和财产价值,而现有纠纷处理模式不能达成两种价值取向的均衡。鉴于此,建议适用“身份资格—房地关系”双重标准的限制继承规则作为司法裁判指引,同时明确“三权分置”背景下宅基地使用权的成员权内涵,以填补双重标准裁判规则的理论漏洞,消解新规则的内在矛盾。

致密砾岩水力裂缝扩展大型矿场实验

砾岩储层由于砾石的存在而具有极强的非均质性,砾岩压裂成缝机理复杂.受限于岩样尺寸和实验条件,室内压裂物理模拟受砾石尺寸效应影响显著,裂缝扩展时间尺度小.为真实记录裂缝动态扩展过程,反映现场实际工况条件下的压后裂缝宏观整体形态,搭建一套超大尺寸(2.0 m×2.0 m×1.0 m)真三轴水力压裂矿场实验平台,通过万吨级应力加载装置、真实管汇和压裂泵车,实现现场真实工况条件下的砾岩水力压裂模拟.基于该平台,分析了水平应力差、压裂液黏度和单孔进液速率对砾岩压裂裂缝动态扩展过程和压后裂缝宏观整体形态的影响规律.实验结果表明,砾岩压裂趋于在井筒处形成“纵向缝+横切缝”的复杂多裂缝形态,远离井筒后,横切主缝扩展优势逐步显现,局部遇砾形成分支缝;12 MPa高水平应力差条件下,压后近井区域形成多缝竞争扩展的复杂裂缝带,横切主缝向远端延伸优势减弱;压裂液黏度低于50 mPa·s时,压后横切主缝扩展优势显著,当压裂液黏度高于50 mPa·s时,近井区域形成复杂多裂缝形态;单孔进液速率超过0.3 m^(3)/min后,井筒处趋于形成多条纵向缝,易导致段间压窜.研究成果有助于深化认识砾岩储层压裂裂缝真实形态,为砾岩水力压裂方案设计提供理论指导.

“培土制水”治法的历史源流及其发展初探

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