Continuous TDEM for monitoring shale hydraulic fracturing

Monitoring and delineating the spatial distribution of shale fracturing is fundamentally important to shale gas production. Standard monitoring methods, such as time-lapse seismic, cross-well seismic and micro-seismic methods, are expensive, time- consuming, and do not show the changes in the formation with time. The resistivities of hydraulic fracturing fluid and reservoir rocks were measured. The results suggest that the injection fluid and consequently the injected reservoir are characterized by very low resistivity and high chargeability. This allows using of the controlled-source electromagnetic method （CSEM） to monitor shale gas hydraulic fracturing. Based on the geoelectrical model which was proposed according to the well-log and seismic data in the test area the change rule of the reacted electrical field was studied to account for the change of shale resistivity, and then the normalized residual resistivity method for time lapse processing was given. The time-domain electromagnetic method （TDEM） was used to continuously monitor the shale gas fracturing at the Fulin shale gas field in southern China. A high-power transmitter and multi-channel transient electromagnetic receiver array were adopted. 9 h time series of Ex component of 224 sites which were laid out on the surface and over three fracturing stages of a horizontal well at 2800 m depth was recorded. After data processing and calculation of the normalized resistivity residuals, the changes in the Ex signal were determined and a dynamic 3D image of the change in resistivity was constructed. This allows modeling the spatial distribution of the fracturing fluid. The model results suggest that TDEM is promising for monitoring hydraulic fracturing of shale.

Effect analysis of borehole microseismic monitoring technology on shale gas fracturing in western Hubei

Hydraulic fracturing technology is an important means of shale gas development,and microseismic monitoring is the key technology of fracturing effect evaluation.In this study,hydraulic fracturing and microseismic monitoring were simultaneously conducted in the Eyangye 2HF well(hereinafter referred to as EYY2HF well).The target stratum of this well is the second member of the Doushantuo Formation of the Sinian System,which is the oldest stratum of horizontal shale gas wells in the world.A total of 4341 microseismic fracturing events were identified,and 23 fracturing stages of the well were defined.The fluctuation of the number of events showed a repeating“high-low”pattern,and the average energy of these events showed minimal differences.These findings indicate that the water pressure required for the reconstruction of the EYY2HF well is appropriate.The main body of the fracture network extended from northwest to southeast,consistent with the interpretation of regional geological and seismic data.The stimulated rock volumes showed a linear increase with the increase of the fracturing stage.Some technological measures,such as quick lift displacement,quick lift sand ratio,and pump stop for secondary sand addition,were adopted during fracturing to increase the complexity of the fracture network.Microseismic fracture monitoring of the well achieved expected eff ects and guided real-time fracturing operations and fracturing eff ect evaluation.

On-Line Monitoring of Cutting Tool Fracture & Wear

A technique of detecting cutting tool fracture and ultimate wear by si- multaneously monitoring both the spindle motor current and cutting process related acoustic emission(AE)in the cutting process is reported.The technique can detect breakage of drills having diameter over 0.8mm,turning cutter crack of area over 0.2mm,and the ultimate wear.The principle,system construction,experimental method and result of the technique are discussed.The ratio of success in detection approaches 96% or higher.

Groundwater Monitoring in the Gneisso-Basaltic Fractured Rock Aquiferous Formations of Kumba, Southwest Region Cameroon: Seasonal Variations in the Aqueous Geochemistry and Water Quality

The objective was to determine and monitor seasonal changes during four hydrological seasons: Wet season (September), Wetdry season (December), Dry season (March) and Drywet season (June) in the groundwater aqueous geochemistry and its domestic-agro-industrial quality using physicochemical parameters and hydrogeochemical tools: Temperature, Electrical Conductivity EC, pH, Total dissolved solids TDS, Ionic ratios, Gibbs diagrams, Piper diagrams Durov diagrams, total hardness HT, Water quality index WQI, Sodium adsorption ratio SAR, Percent Sodium %Na, Kelly’s Ratio KR, permeability index PI, Magnesium adsorption ratio MAR, Residual sodium carbonate RSC and Wilcox diagram. Field physicochemical parameters ranged from: Wet season;pH 3.9 - 6.9;Temperature, 23.3°C - 29.1°C;EC, 10 - 1900 μS/cm;TDS, 6.7 - 1273 mg/L;Wetdry, pH, 5.7 - 11.7;Temperature, 23.6°C - 28.3°C;EC, 1 - 1099 μS/cm, TDS, 0.67 - 736.33 mg/L;Dry pH, 5.7 - 13.1;Temperature, 26.3°C - 30.2°C;EC, 12 - 770 μS/cm, TDS, 8.04 - 515.9 mg/L and Drywet, pH, 4 - 7.4;Temperature, 25.8°C - 30.7°C;EC, 10 - 1220 μS/cm, TDS, 6.7 - 817.4 mg/L. Seventy-two groundwater samples, 18 per season were analysed. All ionic concentrations fell below acceptable World Health Organization guidelines in all seasons. The sequence of abundance of major ions are;Wet, Ca+ > Mg2+ > Na+ = K+ > NH4+, HCO3? > Cl? > NO3? > SO42? > HPO42?;Wetdry Ca+ > K+ > Mg2+ > Na+ > NH4+, HCO3? > Cl? > SO42? > NO3? > HPO42?;Dry Ca+ > K+ > Mg2+ > Na+ > NH4+, HCO3? > Cl?> NO3? > SO42? > HPO42?;Drywet NH4+ > Ca+ > K+ > Mg2+ > Na+;Cl? > HCO3? > NO3? > SO42? > HPO42?. Groundwater ionic content was due to rock weathering and ion exchange reactions. CaSO4 is the dominant water type in Wet and Wetdry seasons;followed by CaHCO3, Na + K-Cl Wet, CaSO4 and CaHCO3 Wetdry;MgCl Dry and Drywet followed by CaCl, CaHCO3 Dry and CaSO4, CaHCO3 Dry-Wet. The dominant hydrogeochemical facies are Ca-Mg-Cl-SO4 followed by Na-K-SO4 Wet and Ca-Mg-HCO3? in all other seasons. Ion exchange, Simple dissolution and uncommon dissolution are the processes determining groundwater character. The water quality indices;WQI, HT, SAR, %Na, KR, PI, MAR,RSC and Wilcox diagrams, indicate that groundwater in Kumba is 80% - 100% excellent during the Drywet &Wet seasons, 5% - 10% unsuitable during the Wetdry & Dry seasons for domestic use while being excellent-good for Agro-Industrial uses in all other seasons. Physicochemical parameters in some areas exceeded permissible limits for drinking. All hydrogeochemical parameters vary with seasons and these variations show the impact of annual cycles of seasonal changes on the aqueous geochemistry of groundwater in Kumba.

A novel true triaxial test system for microwave-induced fracturing of hard rocks

This study introduces a test system for microwave-induced fracturing of hard rocks under true triaxial stress.The test system comprises a true triaxial stress loading system,an open-ended microwaveinduced fracturing system,a data acquisition system,an acoustic emission(AE)monitoring system,and an auxiliary specimen loading system.Microwave-induced surface and borehole fracturing tests under true triaxial stress were fulfilled for the first time,which overcomes the problem of microwave leakage in the coupling loading of true triaxial stress and microwave.By developing the dynamic monitoring system,the thermal response and fracture evolution were obtained during microwave irradiation.The monitoring system includes the infrared thermometry technique for monitoring rock surface temperature,the distributed optic fiber sensing technique for monitoring temperature in borehole in rock,the AE technique and two-dimensional digital speckle correlation technique for monitoring the evolution of thermal damage and the rock fracturing process.To validate the advantages of the test system and investigate the characteristics of microwave-induced fracturing of hard rocks,the study demonstrates the experimental methods and results for microwave-induced surface and borehole fracturing under true triaxial stress.The results show that thermal cracking presented intermittent characteristics(calm eactiveecalm)during microwave-induced surface and borehole fracturing of basalt.In addition,true triaxial stress can inhibit the development and distribution of thermal cracks during microwave-induced surface fracturing.When microwave-induced borehole fracturing occurs,it promotes the distribution of thermal cracks in rock,but inhibits the width of cracks.The results also prove the reliability of the test system.

Mechanism of rock deformation and failure and monitoring analysis in water-rich soft rock roadway of western China

Aiming to get the strata behavior and stability rules of surrounding rock of the main return airway of Yushujing Coal Mine, convergence deformation of two sides and force of U-shaped steel yieldable support and bolt were monitored, and deformation of surrounding rock and mechanical characteristics of support structure were timely obtained to guide the informa- tion construction and optimize supporting parameters in water-rich soft rock roadway. The field monitoring results indicate the following. （1） Convergence displacement of rock surface increases with time continuity and shows surrounding rock＇s intense theological behavior. The original support scheme cannot control the large deformation and strongly theological behavior; （2） Without backfilling, the U-shaped steel support begins to bear load after erecting for 4-7 days and increases rapidly in the first 30 days. The U-shaped steel support at the right shoulder and top of roadway bears a larger force and the left side and shoulder bears a smaller force; （3） The stress of bolt increasing over time and at the right shoulder of roadway has larger growth and value. The mechanism of rock deformation and the failure and strata behavior in water-rich soft rock roadway are revealed based on the results of the measured relaxation zone of surrounding rock, measured stresses, and the rock mechanics tests.

A Comparison of Shale Gas Fracturing Based on Deep and Shallow Shale Reservoirs in the United States and China

China began to build its national shale gas demonstration area in 2012.The central exploration,drilling,and development technologies for medium and shallow marine shale reservoirs with less than 3,500m of buried depth in Changning-Weiyuan,Zhaotong,and other regions had matured.In this study,we macroscopically investigated the development history of shale gas in the United States and China and compared the physical and mechanical conditions of deep and shallow reservoirs.The comparative results revealed that themain reasons for the order-ofmagnitude difference between China’s annual shale gas output and the United States could be attributed to three aspects:reservoir buried depth,reservoir physical and mechanical properties,and engineering technology level.The current engineering technology level of China could not meet the requirements of increasing production and reducing costs for deep shale gas reservoirs;they had reached the beneficial threshold development stage and lacked the capacity for large-scale commercial production.We identified several physical and mechanical reasons for this threshold development stage.Deep shale reservoirs were affected by the bedding fracture,low brittleness index,low clay mineral content,and significant areal differences,as well as by the transformation from elasticity to plasticity,difficulty in sanding,and high mechanical and strength parameters.Simultaneously,they were accompanied by six high values of formation temperature,horizontal principal stress difference,pore pressure,fracture pressure,extension pressure,and closure pressure.The key to deep shale gas horizontal well fracturing was to improve the complexity of the hydraulic fracture network,formadequate proppant support of fracture surface,and increase the practical stimulated reservoir volume(SRV),which accompanied visual hydraulic discrete network monitoring.On this basis,we proposed several ideas to improve China’s deep shale gas development involving advanced technology systems,developing tools,and supporting technologies in shale gas exploration and development in the United States.These ideas primarily involved stimulation technologies,such as vertically integrated dessert identification and optimization,horizontal well multistage/multicluster fracturing,staged tools development for horizontal wells,fractures network morphology monitoring by microseismic and distributed optical fiber,shale hydration expansion,soak well,and fracturing fluid flow back.China initially developed the critical technology of horizontal well large-scale and high-strength volume fracturing with a core of“staged fracturing with dense cutting+shorter cluster spacing+fracture reorientation by pitching+forced-sand addition+increasing diameter perforating+proppant combination by high strength and small particle size particles”.We concluded that China should continue to conduct critical research on theories and technical methods of horizontal well fracturing,suitable for domestic deep and ultra-deep marine and marine-continental sedimentary shale,to support and promote the efficient development of shale gas in China in the future.It is essential to balance the relationship between the overall utilization degree of the gas reservoir and associated economic benefits and to localize some essential tools and supporting technologies.These findings can contribute to the flourishing developments of China’s deep shale gas.

Combined fascia iliaca compartment block and monitored anesthesia care for geriatric patients with hip fracture: Two case reports

BACKGROUND Major hip surgery usually requires neuraxial or general anesthesia with tracheal intubation and may be supplemented with a nerve block to provide intraoperative and postoperative pain relief.CASE SUMMARY This report established that hip surgical procedures can be performed with a fascia iliaca compartment block(FICB)and monitored anesthesia care(MAC)while avoiding neuraxial or general anesthesia.This was a preliminary experience with two geriatric patients with hip fracture,American Society of Anesthesiologists status III,and with many comorbidities.Neither patient could be operated on within 48 h after admission.Both general anesthesia and neuraxial anesthesia were high-risk procedures and had contraindications.Hence,we chose nerve block combined with a small amount of sedation.Intraoperative analgesia was provided by single-injection ultrasound-guided FICB.Light intravenous sedation was added.Surgical exposure was satisfactory,and neither patient complained of any symptoms during the procedure.CONCLUSION This report showed that hip surgery for geriatric patients can be performed with FICB and MAC,although complications and contraindications are common.The anesthetic program was accompanied by stable respiratory and circulatory system responses and satisfactory analgesia while avoiding the adverse effects and problems associated with either neuraxial or general anesthesia.

四川泸州地区大深度页岩气水力压裂电磁监测的应用

电磁法在评估压裂液范围及裂缝形态时发挥着重要作用,在压裂监测中应用前景广泛。然而,对于川南地区的大深度页岩气水力压裂监测应用较少。为此,本文基于电磁监测理论,通过简化压裂模型进行数值模拟实验,在建立电磁监测技术的数据处理流程基础上,结合现场试验,从压裂液波及范围、用液强度、加砂强度、重复改造面积等多方面分析了压裂监测效果,进一步分析了电磁法进行水力压裂裂缝监测的有效性。其中,压裂监测段共计13段,获得各段波及面积4700~24042 m 2,波及宽度36~182 m,平均波及长度207 m。应用实例表明,电磁监测技术能实时了解压裂波及范围与展布形态,对压裂效果评价与施工参数的优化具有一定程度的指导意义。

产教融合背景下电磁法水力压裂裂缝监测实验平台建设

水力压裂是油田提高勘探开发效率的核心技术之一,电磁监测是评估水力压裂效果的有效测量手段。该文升级改造了传统裂缝监测装置,搭建了基于电磁法的水力压裂裂缝在线监测实验教学平台,平台包含多种裂缝模型,且能合理设计各裂缝模型参数,以油田现场压裂裂缝监测问题为导向,灵活优化组合裂缝模型,使用COMSOL数值模拟及可视化方法,在实验室探索压裂裂缝参数与电磁监测信号间的规律,为反演有效裂缝参数提供理论依据。该实验项目具有前沿性、学术研究性和应用性选题特点,可以提升学生自主创新能力和实践探究能力。

基于充电导体模型的水力压裂电磁响应特征分析

随着中国非常规、超低渗油气资源的大力开发,压裂监测技术迎来重大发展机遇。电磁法在地球物理探测方面具有成本低、时效性强、探测深度大等优点,但面对大深度压裂环境,电磁压裂监测技术的可行性亟须论证。基于充电导体和电偶极源扩散电磁场理论,首先构建了不同深度和不同长度下的裂缝压裂模型,分析了各模型的地面总场及异常场的电磁响应特征。分析结果表明:利用井地电磁法进行压裂监测时,观测总场对裂缝长度增加引起的电磁响应不敏感,异常场存在低值带;深度为4000 m时,电磁异常小于1%,深度越大异常场衰减越严重,且相邻测点间异常场的绝对值与深度呈负相关,电磁法压裂监测技术难以兼顾探测精度与探测深度。然后,通过建立压裂监测物理模型,分析实测数据电磁异常曲线特征,验证了理论计算的正确性。最后,结合前人理论成果和实践经验,提出了一种井中激发—地面接收的测网式电磁法压裂监测观测系统,对测区范围与测点间距进行合理约束,系统具有野外施工简捷、监测深度大等优势,为电磁法压裂监测提供了新的发展方向。

基于混合优化算法的电磁监测裂缝参数识别

压裂实时监测是水力压裂效果评价和工程参数优化的重要保障措施之一。传统电磁监测裂缝参数识别方法的准确性和精度难以保证,影响了监测效果。为了提高裂缝参数识别能力,提出了一种基于海洋捕食者密度聚类混合优化算法的电磁监测裂缝参数识别方法。利用海洋捕食者算法(MPA)进行多次寻优,以每次寻优结果作为初始数据集,然后,利用密度聚类算法(DBSCAN)进行聚类,构建中间样本数据集,最后,抽取该样本数据中值作为最终输出结果。采用Rastrigin函数进行测试,分析混合优化算法寻优能力。测试结果表明,相对粒子群优化算法(PSO),MPA算法单次寻优效果较佳。但两种算法寻优结果均具有较强随机性,其中,PSO和MPA算法50次寻优精度分别为10^(-7)~10^(2)和10^(-10)~10^(-2),而改进的混合优化算法寻优效果更稳定,寻优精度达10^(-7)。构建缝长、方位压裂模型并进行了数值模拟实验,结果表明,在噪声低于15%时,缝长和方位识别平均绝对误差分别小于1 m和1°。利用改进的算法对四川盆地某井页岩气压裂电磁监测实测数据进行分析,确定了裂缝改造的长度(缝长)与方位。实例分析结果验证了改进算法的可行性和有效性。

光纤传感技术在油气田开发中的应用

分布式光纤监测技术在油气田开发中具有无可比拟的优势。从分布式光纤传感技术基本原理和井中布设方式出发,介绍了光纤传感技术在水力压裂、连续油管产液剖面测试、邻井压裂监测、油气井注采监测、储气库安全监测和套损监测等多个石油工程领域应用情况。整体表明光纤监测是一种经济高效的监测技术,具备实时监控油气井全生命周期的潜力,是具有科学性、时代特性和安全高效的生产测井技术。同时指出分布式光纤传感技术在油田应用的未来发展应聚焦于提升传感器性能、丰富光纤监测场景应用、提高资料处理解释水平能力,降低应用成本,进一步发挥光纤在油气田开发中的作用。

非常规油气储层智能压裂技术研究进展与展望

非常规储层油气资源丰富,压裂是释放非常规储层油气的必要手段,但压裂优化是一个多模态、高维度、大尺度、细时空的复杂大系统问题。为实现非常规储层压裂系统开发,梳理了油气压裂人工智能3个应用场景:透明油气藏数智化构建和压裂双甜点智能优选、机理—数据联合驱动的压裂工艺参数智能优化和压裂风险预警及在线监控智能调控,然后明确了智能压裂3个方面技术特征,并展望了智能压裂未来5个方面的技术攻关方向。研究结果表明:(1)形成了地质多源数据、建模迭代更新精准化技术,助力了优选地质工程压裂双甜点;(2)建立了机理数据驱动多目标优化压裂参数方法,促进了裂缝均衡扩展、扩大体积和提高产量;(3)开发了压裂动态监测及在线调控流程,支撑了压裂高效、可持续开发,提高压裂效率和油气采收率;(4)提出了“甜点选择数智化—压裂参数智能化—在线监测调控精准化—四维可视化”的地质—工程“动态一体化”智能压裂新理念。结论认为,强化数字孪生智能压裂可视化技术、构建生成式智能压裂大数据生态系统、融合机理数据的工艺参数优化方法、开发压裂动态智能预测监测技术、创新远程智能压裂决策控制系统,可为智能压裂革新发展提供理论指导和技术支撑,为未来压裂人机交互智能决策和闭环调控的实现指明了方向。

分布式光纤传感技术在水力压裂中的研究进展

分布式光纤传感技术作为最新的水力压裂监测技术,应用于各大油田的水力压裂过程中,并且能够实现实时监测,已取得了显著的应用效果。为使业界进一步了解不同类型传感技术的基本原理、理论模型研究进展、现场应用情况,从分布式光纤温度传感技术和声波传感技术在水力压裂过程中的监测基本原理出发,系统总结了各类传感技术的理论模型研究进展和在产液剖面、裂缝扩展形态监测等方面的应用现状,最后提出了未来分布式光纤传感技术的发展方向。研究结果表明:①分布式光纤传感技术可以利用温度或者声波信号转换得到周围环境温度或应变的变化情况,从而实现水力压裂过程中的实时监测;②与分布式光纤声波传感技术相比,温度传感技术的相关理论模型相对较为成熟,能够实现产液剖面及裂缝形态的相关计算;③分布式光纤传感技术主要用于水力压裂过程中压裂液的注入、裂缝扩展等方面的监测。结论认为:分布式光纤传感技术可以有效地推动中国非常规储层的勘探和开发,同时提高水力压裂效果评价技术水平,这对中国油气行业的可持续发展具有重要推动作用。

不同压裂规模下煤储层缝网形态对比研究——以延川南煤层气田为例

以大砂量、大液量为特点的储层改造技术推动深层煤层气开发取得突破,煤层气增储上产保持着良好势头。为探索深部煤储层水力压裂过程中裂缝扩展形态,在鄂尔多斯盆地延川南煤层气田开展不同压裂规模煤储层改造的矿场试验,对比分析压后裂缝扩展形态和储层改造面积,查明了不同类型气井、不同施工规模下裂缝形态的差异性,分析投产后的产气效果,形成了适合研究区深部煤储层改造工艺。结果表明:①低效老井多次中等规模压裂、新井多次大规模压裂和新井单次超大规模压裂均能有效延伸裂缝长度、扩大储层改造面积,但缝网形态存在较大差异。受排采过程和诱导应力影响,低效老井经多次中等规模压裂后,形成主裂缝延伸、次裂缝扩展的“玫瑰花”型缝网;新井压裂改造后形成的缝网形态呈“长椭圆”型,但单次超大规模的液体使用效率更高,相同规模下裂缝半长和改造面积更大。②随压裂次数增加,裂缝半长和改造面积均呈对数增加的趋势,且有明显的递减效应,试采证实2次大规模压裂施工具有良好的经济性,研究结果为井网部署提供了依据。以柴油为动力来源的压裂设备较难适应提升规模后的连续施工,电驱动压裂装置是未来整装煤层气田开发的可靠途径。

页岩油藏水平井分段多簇压裂全井段裂缝扩展数值模拟——以济阳坳陷沙河街组为例

济阳坳陷古近系页岩油资源量达40.5×10^(8) t,展现出良好的勘探开发前景。但页岩油储层埋藏较深、构造复杂、非均质性强,页岩油储层水力压裂裂缝扩展规律尚不明确。为准确预测水力压裂裂缝的扩展形态,建立了基于无量纲近似解的裂缝扩展流固耦合模型。根据济阳坳陷页岩油储层地质工程特征,对该区块一口典型的页岩油水平井开展了裂缝扩展模拟,并将微地震和示踪剂监测结果与模拟结果进行了对比。结果表明:模拟缝长与微地震折算缝长的整体趋势基本一致;模拟结果和示踪数据监测结果的吻合度高于其与微地震监测结果的吻合度;在某些井段,示踪剂结果和微地震结果与模拟结果高度一致。该研究可为济阳坳陷页岩油藏压裂方法设计提供指导。

油气勘探中地震监测技术在裂缝识别中的应用

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海洋CO_(2)管道输送技术现状与展望

管道输送是经济高效的CO_(2)运输方式,海洋CO_(2)运输是离岸碳捕集、利用与封存(CCUS)产业链的关键环节和规模化开展离岸CCUS工程建设所需的核心技术。本文明晰了我国实施离岸CCUS的优势、典型海洋碳运输情境和海洋CO_(2)运输方式,剖析了国内外海洋CO_(2)管道输送的技术与工程概况;从CO_(2)流体相态及流动安全,沿程腐蚀风险评估、监测及预警,CO_(2)泄漏实时监测技术,高压CO_(2)泄放及对环境的影响等方面梳理了海洋CO_(2)管道输送工艺技术现状;从CO_(2)管道材料断裂行为及止裂措施、高耐蚀及密封材料、碳钢管道长寿命运行的关键腐蚀控制技术、注采井筒的腐蚀风险评估等方面梳理了海洋CO_(2)管道材料技术现状。研究认为,加快发展适应海洋CO_(2)管道输送复杂工况的材料体系、全流程CO_(2)管道的智慧管理与数字孪生技术、海底CO_(2)管道全生命周期运行关键技术、在役海底管道改输评估与保障技术,采取加快推动我国近海碳封存CO_(2)管网规划、拓展和深化跨行业/跨机构合作模式创新、系统建设海陆统筹的标准体系、引导专业化技术服务企业深度参与海底CO_(2)管网建设等举措,促进我国海洋CO_(2)管道输送体系高质量建设。