鄂尔多斯盆地延长组第7油层组致密油资源评价

总结了鄂尔多斯盆地延长组第7油层组(简称长7)致密油研究及勘探进展,从砂岩展布、物性特征、致密油充注时间和成藏期次等方面研究长7致密油地质特征,并按特征将致密油划分为A类和B类。在此基础上,采用小面元法和EUR类比法分别计算长7致密油地质资源量和可采资源量。评价结果揭示:长7致密油地质资源量和可采资源量分别为41.78×10~8t和3.73×10~8t,高资源丰度区主要分布在Ning 89井西侧、华池—马岭—环县一带、姬塬和AP11井附近。研究思路和评价结果为中国致密油资源评价及勘探生产提供有益参考。     

Estimated exposure to hepatitis E virus through consumption of swine liver and liver sausages

A quantitative risk assessment was undertaken following the Codex Alimentarius principles in order to predict the exposure of consumers to hepatitis E virus (HEV) through food consumption. Taking into account the tropism of HEV, fresh liver and liver sausages were regarded as having a higher risk of contamination. The model entailed a hypothetical food pathway and was based on worst case scenario where the intake of contaminated food derived from a 100% HEV-infected pig population was estimated. As no data on the prevalence of infectious HEV was available, the HEV-RNA prevalence in food matrices and the seroprevalence of HEV-specific antibodies in swine were assessed and adjusted for diagnostic misclassification and sampling uncertainty. Considering a HEV prevalence of 100% in pigs and excluding further cross-contamination events, a food portion consisting of 130 gr of liver or of 32.5 gr of sausage (containing 30% of liver) yielded an estimated exposure of 8047 and 210 RNA copies (median values), respectively. These findings take into account the effect of thermal treatment on the HEV-RNA concentration of food. Due to the lack of information concerning the correlation between HEV-RNA concentration and the amount of infectious virus as well as the dose-response relationship of HEV, the calculated RNA copies do not allow direct conclusions to be drawn on the risk of infection following ingestion of these food types. The true prevalence was estimated for Switzerland and Germany, leading to an overall prevalence of HEV-RNA in food of 6.2% (90% Highest Density Intervals (HDIs): 2.5%–11.2%). In comparison with fresh liver, liver sausages showed a higher prevalence, most likely due to the presence of more than one liver within the same sausage. The true prevalence of anti-HEV IgG ranged between 59.4% (HDIs 56.5%–62.4%) and 62.6% (HDIs 58.8%–64.3%) and between 7.6% (HDIs 3.3%–13.2%) and 30.5% (HDIs 23.2%–38.2%) in pigs and wild boars, respectively. The high prevalence of antibodies support the evidence that these animals can act as reservoirs for HEV and can contribute epidemiologically to the maintenance of the virus in the surroundings. This study is a preliminary investigation and highlights the major existing gaps needed to be filled in order to enable a refined HEV risk assessment that can drive future decisions for the implementation of food safety and of control measures.     

A review of Listeria monocytogenes: An update on outbreaks,virulence, dose-response,ecology, and risk assessments

Improved control measures starting in the 1990s have greatly reduced the prevalence of L. monocytogenes in many food categories, particularly in meats and meat products. However, the rate of listeriosis has remained constant during the last decade and the more severe, systemic (invasive) form of listeriosis is now recognized as occurring more frequently in small outbreaks than previously recognized. This review addresses the recent advances in epidemiology and virulence, in growth and modelling, and insights from the risk assessments. Recognition of recent outbreaks from food vehicles not traditionally associated with L. monocytogenes (celery, cantaloupe, mung bean sprouts, stone fruits, caramel apples and ice cream) was facilitated by PFGE and, increasingly, whole genome sequencing. The Key Events framework, an understanding of the key individual biochemical steps from ingestion to infection, provides a structure for relating new knowledge on strain variability, mutations, and host susceptibility to the probability of illness. Guidance for determination of the growth/no growth potential of a food has been issued by several regulatory authorities and the risk assessments indicate that prevention of growth remains a principle control element. The recognition of biofilm formation and the possible existence of dormant, non-dividing persister cells will require additional attention. The recent outbreaks underscored the individual characteristics of specific foods (melons vs all fruit; microenvironments in the caramel apples) and raised questions about the current understanding of infectivity of lower doses and the susceptibility of specific individuals. Advances have been made in these areas, but further research is clearly necessary to control this pathogen.     

Quantitative risk assessment of Campylobacter in broiler chickens – Assessing interventions to reduce the level of contamination at the end of the rearing period

The European Food Safety Authority (EFSA) has estimated that a proportion ranging from 20% to 30% of campylobacteriosis in humans may be attributed to the consumption of broiler meat and a reduction in the numbers of Campylobacter in the intestines of infected birds at slaughter by 3 log units would reduce the public health risk by at least 90%. In this study, a stochastic model was implemented to reproduce the dynamics of Campylobacter transmission in broiler flocks and explore the effects of several management conditions and/or on-farm mitigation strategies on the estimated level of contamination of infected flocks at slaughter. Results were expressed as ‘proportion of highly contaminated flocks’ (%HCFs) and estimated as a function of the proportion of infected birds in the flock the day of final depopulation and the individual level of contamination in infected birds. The effects of the mitigation strategies aimed at reducing the level of contamination in infected birds were modelled assuming that those effects are exerted on the distribution describing the bacterial load in infected birds. The impact of management conditions such as the adoption of enhanced biosecurity measures (B+) and/or partial depopulation during the production cycle (T+) were quantified using results of an extensive epidemiological study conducted in UK. A standard broiler flock was reproduced and used as baseline to make comparisons and simulate the effects of the mitigation strategies of interest. The baseline model predicted 18.8% probability of HCFs at slaughter. A positive effect ranging from −32.44% to −4.78% was attributed to B+ while T+ had negative effect ranging from +17.55% to +86.70%. When both the effects were tested simultaneously (B+T+), results were not conclusive with %HCFs ranging from −20.21% to +77.65%. When mitigation strategies operating on Campylobacter concentration in intestine were tested, a reduction of 100% and 99.6% in %HFCs were estimated following a generic treatment with bacteriocins and bacteriophages. Reduction in %HCFs as a function of immunization measures were explored and a reduction of 15% in the rate of transmission led to a %HCFs at slaughter reduced by almost 50%. The model was developed to be flexible, easily reproducible, updatable and adaptable to several baseline scenarios. The main parameters and assumptions underlying the baseline model were tested and a sensitivity analysis was performed to identify and discuss the impact that the uncertainty in the baseline information might have on the outcomes.     

Assessment of foodborne pathogen presence in the peach supply chain and its potential risk to the end consumer

Peaches are popular, nutritious and widely consumed. Being a tree crop, it is considered a low risk fruit, with no direct water contact, and no previous foodborne disease outbreaks associated with its consumption. However, in 2014 the pioneer association between stone fruit and a foodborne illness was reported, linking Listeria monocytogenes to stone fruit. This highlights the need for better understanding of risk associated with contaminated fresh stone fruit, in order to implement adequate preventative measures. No information is available on the presence of foodborne pathogens on peaches in the supply chain. A case study approach was therefore followed to assess foodborne pathogen presence on the farm, focusing on the impact of irrigation water, facility sanitation and hygiene by collecting various fruit and environmental samples (n = 428). This study demonstrates the effectiveness of integrating basic microbial testing with safety management and risk assessment tools that can be collectively used to improve the food safety management system. No Salmonella Typhimurium was detected from samples, however, Escherichia coli O157:H7, Listeria spp. and Staphylococcus aureus were detected on fruit and environmental samples. Despite the GlobalG.A.P. certification status of the farm, livestock frequented water sources which lead to E. coli O157:H7 contamination. This conclusion was based on positive detection of foodborne pathogens from the water sources and subsequent removal of livestock which resulted in a definite decrease in pathogen detection. A number of E. coli O157:H7 and S. aureus were detected during the second year of monitoring from environmental samples and it was observed that the personal hygiene and facility sanitation was not adequately enforced. Based on feedback given to the farmer, enforcement was improved and a definite decrease in foodborne pathogens was observed in the following sampling cycle. Areas of risk that were still identified following the fourth year of monitoring included the water source used for irrigation and poor sanitation in the production and processing facilities. Limited foodborne pathogen prevalence on peaches over the full study period as well as the extended export supply chain at controlled temperatures resulted in low-to-medium calculated consumer risk. The correct and meticulous implementation of integrated and holistic pre- and post-harvest food safety management systems is therefore essential to prevent produce contamination, reduce the consumer risk and therefore ensure overall product safety.     

Assessment of safety margins of exposure to non-genotoxic chemical substances in food

The concept of Food Safety Margin (FSM) was introduced in microbiological risk analysis as an alternative approach to risk characterization within the informed-risk decision-making process. Its aim was to verify compliance with food safety objectives by assessing the effects of uncertainties. This paper describes the fundamentals and develop a new formulation of safety margins to verify compliance with food safety goals in relation to exposure to non-genotoxic chemical hazards. Both classical and probabilistic metrics were used to compare a given exposure to an estimated daily intake (EDI) with a given safety goal, the acceptable daily intake (ADI). The safety margins of these metrics were assessed in the exposure of peaches to organophosphorus pesticides. The pesticides considered were Azinphos-methyl, Chlorpyrifos, Diazinon, Dimethoate, Methamidophos, Parathion-methyl and Phosmet. The concentrations were obtained from the USDA pesticide database. The study period included the 11 years in which peaches were analysed from 1994 to 2014. The results show the importance of using the effect of uncertainty instead of mean values for risk characterization and that not only safety margins increased during this period but also that uncertainty was reduced. In general, large safety margins were observed in the period studied and few situations were found in which exposure was outside the safety limits.     

海底腐蚀管道剩余强度评估方法对比

为了准确评估海底腐蚀油气管道的剩余强度,对目前常用的5种海底管道腐蚀强度评估方法,即ASME-B31G 标准、管道腐蚀准则方法（PCORRC）、DNV-RP-F101标准、API 579准则和有限元分析方法的评估原理、适用范围以及相互之间的异同点进行了对比,从而优选出更合理准确的剩余强度评估方法。分析结果表明,有限元分析方法不但考虑到了管道内缺陷之间的相互作用对评估结果的影响,还考虑到了缺陷形状和尺寸对评估结果的影响以及管道外界载荷的影响,且评估过程不需要近似公式,评估环境与实际环境类似,所以评估结果的准确性较高,未来应加强有限元分析方法的使用。     

灰色关联分析法在油气管道半定量风险评价中的应用

肯特(W．kent Muhlbauer)管道风险评价法是一种半定量风险评价法,但是该方法在我国还处在起步阶段,其理论基础和应用技术都很不完善。为了有效处理评分中存在的主观性和不确定性因素,已经把模糊综合评判法引入到管道风险评价中。但是,传统的相对风险值计算还不够准确,为此介绍了灰色关联分析在油气管道半定量风险评价中的应用。通过对影响管道风险的评价指标(因素)体系的综合分析,确定了灰色综合评价的层次结构模型。构建了由第三方破坏指数、腐蚀指数、设计指数、错误指数、介质危险指数5大指标体系构成的管道系统风险综合评价指标体系,并采用层次分析与专家打分相结合的方法计算权重。在油气管道半定量风险评价中应用灰色关联分析法,可以使评价结果更准确。     

压井施工的精细计算

随着油气勘探开发的不断深入,目前油气钻井的难度、深度不断增加,大多数井的压力大,温度高,井控问题目益突出。如我国西北部油田在勘探开发过程中,常遇到高温高压（超高温超高压）油气层。目前采用的压力控制技术及井控装备已不能完全满足这些井的勘探开发需要。文中仍是采用经典的井控理论,主要对工程师压井法进行了更为细致地划分和计算,从而提高了这种常规压井方法的计算精度,为压井决策提供了保障。