Advanced production decline analysis of tight gas wells with variable fracture conductivity

Considering the characteristics that the fracture conductivity formed by hydraulic fracturing varies across space and time, a new mathematical model was established for seepage flow in tight gas fractured vertical wells which takes into account the effects of dual variable conductivity and stress sensitivity. The Blasingame advanced production decline curves of the model were obtained using the finite element method with hybrid elements. On this basis, the effects of fracture space and time dual variable conductivity and stress sensitivity on Blasingame curve were analyzed. The study shows that the space variable conductivity mainly reduces decline curve value at the early stage; the time variable conductivity can result in drops of the production and the production integral curves, leading to a S-shaped curve; dual variable conductivity is the superposition of the effects given by the two variable conductivities; both time and space variable conductivities cannot delay the time with which the formation fluid flow reaches the quasi-steady state. The stress sensitivity reduces the curve value gradually rather than sharply, delaying the time the flow reaching the quasi-steady state. Ignoring the effects of variable conductivity and stress sensitivity will not affect the estimation on well controlled dynamic reserves. However, it can result in large errors in the interpretation of fractures and reservoir parameters. Conventional advanced production decline analyses of a tight gas fractured well in the Sulige gas field showed that the new model is more effective and reliable than the conventional model, and thus it can be widely applied in advanced production decline analysis of wells with the same characteristics in other gas fields.

A Novel Process for Natural Gas Liquids Recovery from Oil Field Associated Gas with Liquefied Natural Gas Cryogenic Energy Utilization

A novel process to recovery natural gas liquids from oil field associated gas with liquefied natural gas (LNG)cryogenic energy utilization is proposed.Compared to the current electric refrigeration process,the proposed process uses the cryogenic energy of LNG and saves 62.6%of electricity.The proposed process recovers ethane, liquid petroleum gas(propane and butane)and heavier hydrocarbons,with total recovery rate of natural gas liquids up to 96.8%.In this paper,exergy analysis and the energy utilization diagram method(EUD)are used to assess the new process and identify the key operation units with large exergy loss.The results show that exergy efficiency of the new process is 44.3%.Compared to the electric refrigeration process,exergy efficiency of the new process is improved by 16%.The proposed process has been applied and implemented in a conceptual design scheme of the cryogenic energy utilization for a 300 million tons/yr LNG receiving terminal in a northern Chinese harbor.

GAS DETECTING AND FORECASTING VIA TIME SERIES METHOD

The importance and urgency of gas detecting and forecasting in underground coal mining are self-evident. Unfortunately, this problem has not yet been solved thoroughly.In this paper, the author suggests that the time series analysis method be adopted for processing the gas stochastic data. The time series method is superior to the conventional Fourier analysis in some aspects, especially, the time series method possesses forecasting (or prediction) function which is highly valuable for gas monitoring.An example of a set of gas data sampled from a certain foul coal mine is investigated and an AR (3) model is established. The fitting result and the forecasting error are accepted satisfactorily.At the end of this paper several remarks are presented for further discussion.

Comparative analysis of greenhouse gas emission inventory for Pakistan: Part Ⅱ agriculture, forestry and other land use and waste

Understanding Pakistan's greenhouse gas(GHG)emission status is critical for identifying the national targets for GHG mitigation with respect to the nationally determined contributions(NDCs).This study focuses on the development of Pakistan's GHG(C0_(2),CH_(4),and N20)inventories for agriculture,forestry and other land use(AFOLU)and waste sectors using 2006 IPCC Guidelines.This study should be seen as a direct continuation of the preceding one(Part I[Available online at:https://doi.Org/10.1016/j.accre.2020.05.002])which discusses energy and industrial processes and product use in compliance with the 2006 and 1996 IPCC Guidelines.It also provides sector-specific comparative time series(1994-2017)analysis of GHG inventories,identification of key categories,and national GHG emissions trend for Pakistan.The results indicate an average relative difference(on average for time series 1994-2017)of 19%and 6%in total GHG emissions(C0_(2)-eq)from AFOLU and waste sector respectively between 2006 and 1996 IPCC Guidelines.The absolute difference over the entire time series for AFOLU and waste sector was in the range of 3-67 Mt C0_(2)-eq and 1-7 Mt CQ2-eq respectively.Findings further reveal that the quantity of national GHG emissions by 2006 IPCC Guidelines is 10%lower on average for complete time series compared to 1996 IPCC Guidelines.The average relative difference for total national emissions of C0_(2),CH_(4) and N20 is-1%,9%,and 48%respectively.Key category analysis based on 2006 IPCC Guidelines estimates identified three categories,each contributing>10%to the level assessment in the latest year 2017 and accounting for approximately half of the national GHG emissions.In order to further improve the reliability of GHG inventories,Pakistan needs to move from 1996 to 2006 IPCC Guidelines under a higher Tier approach particularly for identified key categories.

Sensitivity analysis of a methanol and power polygeneration system fueled with coke oven gas and coal gas

The sensitivity analysis of a polygeneration energy system fueled with duo fuel of coke oven gas and coal gas is performed in the study,and the focus is put on the relations among syngas composition,conversation rate and performance.The impacts of the system configuration together with the fuel composition on the performance are investigated and discussed from the point of cascading utilization of fuel chemical energy.First,the main parameters affecting the performance are derived along with the analysis of the system configuration and the syngas composition.After the performance is being simulated by means of the Aspen Plus process simulator of version 11.1,the variation of the performance due to the composition of syngas and the conversion rate of chemical subsystem is obtained and discussed.It is obtained from the result that the proper conversion rate of the chemical subsystem according to the specific syngas composition results in better performance.And the syngas composition affects the optimal conversion rate of the chemical subsystem,the optimal point of which is around the stoichiometric composition for methanol production(CO/H_(2)=0.5).In all,the polygeneration system fueled with coke oven gas and coal gas,which can realize the reasonable conversion of syngas to power and chemical product according to the syngas composition,is a promising method for coal energy conversion and utilization.

Formation and utilization of water resources of Tarim River

The Tarim River is a typical inland river in arid area without runoff yield of itself, and water resources are all supplied by its headstreams. The method of time series analysis is applied to annual runoff series of three headstreams, namely the Aksu River, Yarkant River and Hotan River to analyze their dynamic variations. A model is established to estimate water consumption in the headstream areas. Quantitative results indicate that both total annual runoff of headstreams and water consumption in the headstream areas have an increasing trend. The dynamic trends of annual runoff of hydrologic stations along the mainstream of the Tarim River are also presented to estimate the intermittence drying-up time at each station. Water consumption model of the mainstream area is used to analyze the characteristics of water consumption in the upper and middle reaches. It is shown that water consumption in each river reach of the mainstream decreases with the decrement of inflow and increases with human activities.

地下管廊抗震研究现状综述

针对地下管廊工程建设高速发展、抗震减灾需求愈发凸显的现状,综述地下管廊抗震研究现状.首先,通过国内外以往的震害实例,对地下管廊的震害形式、震害影响因素及震害机理进行了系统性总结.其次,从拟静力试验和振动台试验两个方面总结了地下管廊抗震性能的试验研究现状.再次,总结了地下管廊抗震分析的简化分析方法、动力时程方法、地震易损性评估及减隔震技术的研究现状.最后,基于文献综述提出了目前地下管廊抗震研究亟待解决的问题并做出展望,以期促进地下管廊抗震研究的发展.研究表明:地下管廊在地震作用下的破坏形式主要有混凝土剥落、裂缝贯通、接缝错位或张开、管廊受剪断裂等;地震作用下地下管廊穿越非均匀场地时动力响应的放大效应显著,地下管廊穿越软硬交互等非均匀场地时的抗震性能研究值得重视;交叉节点是地下管廊的薄弱环节,交叉管廊的抗震设计方法研究值得关注;预制管廊接头易受到地震破坏,不同类型预制管廊接头的抗震性能研究需深入探索;城市大型地下管廊系统抗震性能受到不同交叉节点和不同管廊之间的交互影响,高效的地下管廊系统建模方法和高效的简化分析方法亟待研究;城市大型地下管廊系统地震易损性分析是重要的发展方向;地下管廊的减隔震技术值得发展.

Simulation of pore space production law and capacity expansion mechanism of underground gas storage

One-dimensional gas injection storage building and one-cycle injection-production modeling experiment,and two-dimensional flat core storage building and multi-cycle injection-production modeling experiment were carried out using one-dimensional long core and large two-dimensional flat physical models to find out the effects of reservoir physical properties and injection-production balance time on reservoir pore utilization efficiency,effective reservoir capacity formation and capacity-reaching cycle.The results show that reservoir physical properties and formation water saturation are the main factors affecting the construction and operation of gas-reservoir type underground gas storage.During the construction and operation of gas-reservoir type gas storage,the reservoir space can be divided into three types of working zones:high efficiency,low efficiency and ineffective ones.The higher the reservoir permeability,the higher the pore utilization efficiency is,the smaller the ineffective working zone is,or there is no ineffective working zone;the smaller the loss of injected gas is,and the higher the utilization rate of pores is.The better the reservoir physical properties,the larger the reservoir space and the larger the final gas storage capacity is.The higher the water saturation of the reservoir,the more the gas loss during gas storage capacity building and operation is.Optimizing injection-production regime to discharge water and reduce water saturation is an effective way to reduce gas loss in gas storage.In the process of multiple cycles of injection and production,there is a reasonable injection-production balance time,further extending the injection-production balance period after reaching the reasonable time has little contribution to the expansion of gas storage capacity.

长期护理保险对失能人员医疗服务利用及费用的影响——基于中断时间序列分析

目的:研究长期护理保险政策对长期护理保险待遇享受人员医疗服务利用及费用的影响,探讨长期护理保险实施效果并提出建议。方法:采用卡方检验、中断时间序列分析,综合分析待遇享受人员的医疗服务利用及费用在长期护理保险实施前后的变化情况。结果:研究发现,对不同医疗保险类型、失能等级和年龄的失能人员选择不同的照护方式存在显著差异(P<0.05),待遇享受人员医疗服务利用频次及费用均有降低。结论:医疗保险类型、失能等级和年龄是照护方式选择的影响因素,待遇享受人员的医疗服务利用和费用显著降低,长期护理保险可能减少了“社会性住院”行为。政策建议:缩小城乡待遇差异、促进一体化发展,探索居家照护与机构上门结合、促进护理机构综合发展,健全照护服务体系、减轻家庭压力。

Analysing Delay Impact from Potential Risk Factors on Project Delivery of Oil and Gas Pipeline:A Case Study in IRAQ

The aim of this paper is to present the design and specifications of an integrated Delay Analysis Framework(DAF),which could be used to quantify the delay caused by the Risk Factors(RFs)in Oil and Gas Pipelines(OGPs)projects in a simple and systematic way.The main inputs of the DAF are(i)the potential list of RFs in the projects and their impact levels on the projects and the estimated maximum and minimum duration of each task.Monte Carlo Simulation integrated within@Risk simulator was the key process algorithm that used to quantify the impact of delay caused by the associated RFs.The key output of the DAF is the amount of potential delay caused by RFs in the OGP project.The functionalities of the developed DAF were evaluated using a case study of newly developed OGP project,in the south of Iraq.It is found that the case study project might have delayed by 45 days if neglected the consideration of the RFs associated with the project at the construction stage.The paper concludes that identifying the associated RFs and analysing the potential delay in advance will help in reducing the construction delay and improving the effectiveness of the project delivery by taking suitable risk mitigation measures.

退役锂电池高压放电声音信号时频特征研究

为实现退役动力电池的梯次利用,以10 A·h方壳电池高压放电声音为研究对象,将不同SOH电池内部离子活性、放电能力、电荷迁移与补给能力等与其放电声纹建立联系,提取相关统计指标表征电池老化状态,为后续通过声音特征快速检测退役电池SOH打下理论基础。通过自搭建声音采集实验平台采集电池放电声音,而后对放电声音进行预处理,最后提取其时域特征(时域图、均方根能量)与频域特征(声谱图)进行分析。通过时频域特征分析得知:电池在高压电场诱导下放电发声,电池放电高能区域集中于10 kHz附近,随着SOH的降低,电池内部离子失活,电荷迁移与补给能力减弱,时域图中声音信号波形稳定性越差,且振幅主体范围不断减小,电池放电声音的均方根能量不断降低,语谱图中则表现为放电现象微弱,放电频率以及能量大幅下降。

时序InSAR方法在矿区变形监测中的应用

煤炭资源的不断开采所引起的矿区沉降会给地表基础设施带来不同程度的损毁,监测矿区的变形对地表建筑安全具有重要意义。基于短基线合成孔径雷达干涉测量(Small Baseline Subset Interferometric Synthetic Ap-erture Radar,SBAS-InSAR)技术对某矿区的145景哨兵一号卫星影像数据进行处理,对其开展了近5年的时序形变监测,获取了该矿区的累计沉降量和年平均沉降速率。结果表明,该矿区共形成7处沉降区域,最大累计沉降量为410mm,最大年平均沉降速率为83.9mm/a,且有沉降继续加深、影响范围扩大的趋势。最后,利用土地利用数据分析造成矿区的主要原因为建设用地的不断扩张。本研究说明时序InSAR技术在矿区变形监测中有较好的应用,可为今后矿区资源的开发利用提供科学依据。

关于燃驱压缩机组冷备的分析与探讨

某长输天然气管道承载着为西部区域城市输送天然气清洁能源的任务,沿线设有天然气输配场站和天然气增压场站。燃气轮机作为压气站主要动力设备,为天然气增压提供能量,同时也是能耗最大的设备,对燃压机组进行冷备能耗研究,对降低能量消耗,清洁生产意义重大。近年来,因上游气田产量降低、工艺调整等情况,某中间压气站全年机组运行时间较少,为合理降低能耗,开展机组的冷备具有较好经济效益和生产意义[1]。

基于时程分析法的综合管廊抗震性能研究

提高地下综合管廊工程抗震能力对城市可持续发展意义重大。以实际工程为背景,建立了地下综合管廊的不同长度结构-土体三维模型,在模态分析的基础上,采用Rayleigh阻尼方法对模型进行时程分析。采用相关性热力图方法分析模型长宽比对模型计算精度的影响,研究了壁厚对结构力学性能的影响。研究结果表明:(1)当长宽比小于1∶1时,模型刚度较小,导致误差很大;模型长宽比为1∶1~10∶1时,分析结果比较稳定;当长宽比达到12∶1时,模态分析结果以刚性位移为主。(2)对于仅需要得到结构最大响应的分析模型,长宽比宜为1∶1。(3)结构应力的主要受到弯矩的控制,结构弯矩主应力最大区域集中于四周角点区域,在实际工程中应当加强角点区域。(4)随着壁厚的增加,结构所受地震荷载均有所增大,但同时最大主应力和层间位移角则有所减小,综合考虑安全经济两方面因素,壁厚宜选择250mm。

地下管廊减隔震装置抗震性能分析

为降低地震对城市地下综合管廊内部管道运营安全的影响,利用三维有限元数值模拟对围岩-管廊体系进行模态分析,提出新型减隔震支架和减隔震支墩设计方案,对围岩-管廊体系、围岩-管廊-支架体系和围岩-管廊-支墩-管道体系进行动力时程分析,并对减隔震支架进行室内抗震性能试验。结果表明:围岩-管廊体系前十阶固有频率位于3.5~6.1 Hz间,与地震波频率接近,地震作用下容易出现共振;管廊横截面上部及底部棱角处动载荷均超过40 MPa,中上部位移变形超过30 mm,受地震作用影响大;地震作用下,减隔震支架最大位移较普通支架降低55%,且较大位移持续时间明显缩短;最大应力较普通支架减小26%,且最大应力由支架根部移至支架斜撑位置;减隔震支墩支撑管道最大位移较普通支墩降低9.97%,且管道位移相位后移;最大应力较普通支墩降低约24%;减隔震支架极限抗拉承载力为普通支架的2.39倍,极限抗压承载力为普通支架的4.53倍,抗震性能显著优于普通支架。新型减隔震装置的抗震性能及承载力明显优于传统装置,可有效降低地震对管线安全的影响。

气井时间利用分析

气井是气田天然气生产的主要对象 ,气井利用情况对天然气生产量影响很大。在地质条件和气井数量不变的情况下 ,加强气井管理 ,减少关井 ,增加采气时间 ,改善气井的利用情况 ,就可以达到生产更多的天然气。气井利用情况 ,包括两个方面因素 :一是改善气井的利用 ,使本期应采气的气井尽可能投入开采 ;二是投入开采的气井应尽可能充分利用。文章通过对气井的时间利用指标的计算和分析 ,运用指数分析的原理 ,从计划开井口数、气井利用率和采气时率的变化 ,分别对影响气井时间利用和气井综合利用率进行了分析 ,找到影响气井时间利用和气井综合利用的主要因素 ,从而提高气井的时间利用。

采用效用分析方法测量中国人青光眼患者的视觉相关生活质量

背景近年来关于青光眼对患者生活质量的影响日益受到临床工作者的关注，但调查结果表明各种视功能量表均存在一定的不足，准确、全面地评价影响青光眼患者生活质量的主观和客观因素值得深入研究。目的利用效用分析的方法测量青光眼患者视觉相关生活质量并初步分析其相关因素。方法收集北京同仁医院门诊确诊的青光眼患者，采用效用分析中的线性等级尺度（RS）法和时间交易（TTO）法进行问卷调查以获得反映青光眼患者疾病相关生活质量的效用值，比较RS法和TTO法所得效用值的差异和相关性，分析不同性别、年龄、受教育程度、工作状态、青光眼家族史、青光眼手术史、不同视功能损害程度以及不同青光眼类型对患者效用值的影响。结果研究共纳入青光眼患者86例，其中男62例，女24例；平均年龄44．67岁。RS法和TTO法测得青光眼患者的效用值分别为0．62±0．19和0．77±0．12，两种方法获得的效用值之间无显著相关关系（r=0．074，P=0．499）。RS法计算所得的效用值受日常生活视力、视野缺损程度以及青光眼手术史的影响，而TTO法测得的效用值主要与患者的年龄、工作状态以及受教育程度有关，与患者视力和视野损害的严重程度无相关性。校正了年龄、工作状态和受教育程度以后，较差眼视力≥0．3的青光眼患者其TTO效用值显著高于较差眼视力〈O．3者（P=0．029）。结论效用分析的方法简单、灵敏，可较好地被患者所接受。RS法所得效用值受日常生活视力、视野缺损程度以及青光眼手术史的影响，反映了患者对自身视觉状态的主观评价。TTO法测得的效用值主要与患者的年龄、工作状态以及受教育程度有关，反映了不同患病个体对自身视觉相关生活质量的主观评价。视功能的损害程度在青光眼患者的总体生活质量中不起决定性作用。

单相受热面通用动态计算模型

本文以文献［２］为基础，提出了一种通用于单相受热面工作过程实时数字仿真和工程定量分析的动态数学模型及其算法。其主要特点在于：（１）该算法在很大的积分时间步长范围内具有良好的计算精度和数值稳定性；（２）文中所建立的分布参数模型只有一个可调的变量△τ，针对不同的应用场合，选用适当的△τ，即可满足对模型运算速度或计算精度的需求。

基于不同抗震方法的砂土地区单舱管廊地震反应分析

利用三种不同的抗震分析方法——反应加速度法、反应位移法、时程分析法,基于有限元计算方法对砂土地区单舱管廊结构进行横向地震作用计算,分析了在三种不同分析方法下单舱管廊的受力响应特征,比较了三种方法在同种工况下的响应规律。分析结果表明,在单舱管廊结构抗震分析中三种方法具有相似又呈现不同特点的内力分布规律。同时可以得出,单舱管廊结构的受力敏感位置为结构侧墙与底板角点一定范围内,设计时应重点关注。

公交运行状况改善与客流量之间的灵敏度分析

为了实时掌握公交运行状况改善后各种交通方式客流特别是公交客流的变化,将不同交通方式的运行状况用平均运行时间和运行时间可靠度2个指标来表示,并将其引入到效用函数中,应用Log it模型得出同一OD对间不同交通方式的客流量.在此基础上提出了OD对客流在不同交通方式间的均衡配流模型,然后采用灵敏度分析方法中存在2个或多个扰动参数的情形设计了公交运行状况改善与客流量间的关系模型.实例计算表明该模型与算法是有效的.