Influences of clean fracturing fluid viscosity and horizontal in-situ stress difference on hydraulic fracture propagation and morphology in coal seam

The viscosity of fracturing fluid and in-situ stress difference are the two important factors that affect the hydraulic fracturing pressure and propagation morphology. In this study, raw coal was used to prepare coal samples for experiments, and clean fracturing fluid samples were prepared using CTAB surfactant. A series of hydraulic fracturing tests were conducted with an in-house developed triaxial hydraulic fracturing simulator and the fracturing process was monitored with an acoustic emission instrument to analyze the influences of fracturing fluid viscosity and horizontal in-situ stress difference on coal fracture propagation. The results show that the number of branched fractures decreased, the fracture pattern became simpler, the fractures width increased obviously, and the distribution of AE event points was concentrated with the increase of the fracturing fluid viscosity or the horizontal in-situ stress difference. The acoustic emission energy decreases with the increase of fracturing fluid viscosity and increases with the increase of horizontal in situ stress difference. The low viscosity clean fracturing fluid has strong elasticity and is easy to be compressed into the tip of fractures, resulting in complex fractures. The high viscosity clean fracturing fluids are the opposite. Our experimental results provide a reference and scientific basis for the design and optimization of field hydraulic fracturing parameters.

Synthetic polymers:A review of applications in drilling fluids

With the growth of deep drilling and the complexity of the well profile,the requirements for a more complete and efficient exploitation of productive formations increase,which increases the risk of various complications.Currently,reagents based on modified natural polymers(which are naturally occurring compounds)and synthetic polymers(SPs)which are polymeric compounds created industrially,are widely used to prevent emerging complications in the drilling process.However,compared to modified natural polymers,SPs form a family of high-molecular-weight compounds that are fully synthesized by undergoing chemical polymerization reactions.SPs provide substantial flexibility in their design.Moreover,their size and chemical composition can be adjusted to provide properties for nearly all the functional objectives of drilling fluids.They can be classified based on chemical ingredients,type of reaction,and their responses to heating.However,some of SPs,due to their structural characteristics,have a high cost,a poor temperature and salt resistance in drilling fluids,and degradation begins when the temperature reaches 130℃.These drawbacks prevent SP use in some medium and deep wells.Thus,this review addresses the historical development,the characteristics,manufacturing methods,classification,and the applications of SPs in drilling fluids.The contributions of SPs as additives to drilling fluids to enhance rheology,filtrate generation,carrying of cuttings,fluid lubricity,and clay/shale stability are explained in detail.The mechanisms,impacts,and advances achieved when SPs are added to drilling fluids are also described.The typical challenges encountered by SPs when deployed in drilling fluids and their advantages and drawbacks are also discussed.Economic issues also impact the applications of SPs in drilling fluids.Consequently,the cost of the most relevant SPs,and the monomers used in their synthesis,are assessed.Environmental impacts of SPs when deployed in drilling fluids,and their manufacturing processes are identified,together with advances in SP-treatment methods aimed at reducing those impacts.Recommendations for required future research addressing SP property and performance gaps are provided.

Gas-hydrate formation,agglomeration and inhibition in oil-based drilling fluids for deep-water drilling

One of the main challenges in deep-water drilling is gas-hydrate plugs,which make the drilling unsafe.Some oil-based drilling fluids（OBDF） that would be used for deep-water drilling in the South China Sea were tested to investigate the characteristics of gas-hydrate formation,agglomeration and inhibition by an experimental system under the temperature of 4 ？C and pressure of 20 MPa,which would be similar to the case of 2000 m water depth.The results validate the hydrate shell formation model and show that the water cut can greatly influence hydrate formation and agglomeration behaviors in the OBDF.The oleophobic effect enhanced by hydrate shell formation which weakens or destroys the interfacial films effect and the hydrophilic effect are the dominant agglomeration mechanism of hydrate particles.The formation of gas hydrates in OBDF is easier and quicker than in water-based drilling fluids in deep-water conditions of low temperature and high pressure because the former is a W/O dispersive emulsion which means much more gas-water interfaces and nucleation sites than the later.Higher ethylene glycol concentrations can inhibit the formation of gas hydrates and to some extent also act as an anti-agglomerant to inhibit hydrates agglomeration in the OBDF.

Rheological properties of oil-based drilling fluids at high temperature and high pressure

The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.

Squeeze-Strengthening Effect of Silicone Oil-based Magnetorheological Fluid

In order to study the squeeze-strengthening effect of silicone oil-based magnetorheological fluid （MRF）, theoretical basis of disc squeezing brake was presented and a squeezing braking characteristics test-bed for MRF was designed. Moreover, relevant experiments were carded out and the relationship between squeezing pressure and braking torque was proposed. Experiments results showed that the yield stress of MRF improved linearly with the increasing of external squeezing pressure and the braking torque increased three times when external squeezing pressure achieved 2 MPa.

Intermolecular interactions induced property improvement for clean fracturing fluid by deep eutectic solvents

Fracturing fluid property play a critical role in developing unconventional reservoirs.Deep eutectic solvents(DESs)show fascinating potential for property improvement of clean fracturing fluids(CFFs)due to their low-price,low-toxicity,chemical stability and flexible designability.In this work,DESs were synthesized by mixing hydrogen bond acceptors(HBAs)and a given hydrogen bond donor(HBD)to explore their underlying influence on CFF properties based on the intermolecular interactions.The hydrogen-bonding,van der Waals and electrostatic interactions between DES components and surfactants improved the CFF properties by promoting the arrangement of surfactants at interface and enhancing the micelle network strength.The HBD enhanced the resistance of CFF for Ca^(2+) due to coordination-bonding interaction.The DESs composed of choline chloride(ChCl)and malonic acid show great enhancement for surface,rheology,temperature resistance,salt tolerance,drag reduction,and gel-breaking performance of CFFs.The DESs also improved the gel-breaking CFF-oil interactions,increasing the imbibition efficiencies to 44.2%in 74 h.Adjusting HBAs can effectively strengthen the intermolecular interactions(e.g.,HBA-surfactant and HBD-surfactant interactions)to improve CFF properties.The DESs developed in this study provide a novel strategy to intensify CFF properties.

Comparison and application of different empirical correlations for estimating the hydrate safety margin of oil-based drilling fluids containing ethylene glycol

As the oil and gas industries continue to increase their activity in deep water, gas hydrate hazards will become more serious and challenging, both at present and in the future. Accurate predictions of the hydrate-free zone and the suitable addition of salts and/or alcohols in preparing drilling fluids are particularly important both in preventing hydrate problems and decreasing the cost of drilling operations. In this paper, we compared several empirical correlations commonly used to estimate the hydrate inhibition effect of aqueous organic and electrolyte solutions using experiments with ethylene glycol （EG） as a hydrate inhibitor. The results show that the Najibi et al. correlation （for single and mixed thermodynamic inhibitors） and the Ostergaard et al. empirical correlation （for single thermodynamic inhibitors） are suitable for estimating the hydrate safety margin of oil-based drilling fluids （OBDFs） in the presence of thermodynamic hydrate inhibitors. According to the two correlations, the OBDF, composed of 1.6 L vaporizing oil, 2% emulsifying agent, 1% organobentonite, 0.5% SP-1, 1% LP-1, 10% water and 40% EG, can be safely used at a water depth of up to 1900 m. However, for more accurate predictions for drilling fluids, the effects of the solid phase, especially bentonite, on hydrate inhibition need to be considered and included in the application of these two empirical correlations.

Development of a High Temperature and High Pressure Oil-Based Drilling Fluid Emulsion Stability Tester

When drilling deep wells and ultra-deep wells, the downhole high temperature and high pressure environment will affect the emulsion stability of oil-based drilling fluids. Moreover, neither the demulsification voltage method nor the centrifugal method currently used to evaluate the stability of oil-based drilling fluids can reflect the emulsification stability of drilling fluids under high temperature and high pressure on site. Therefore, a high-temperature and high-pressure oil-based drilling fluid emulsion stability evaluation instrument is studied, which is mainly composed of a high-temperature autoclave body, a test electrode, a temperature control system, a pressure control system, and a test system. The stability test results of the instrument show that the instrument can achieve stable testing and the test data has high reliability. This instrument is used to analyze the factors affecting the emulsion stability of oil-based drilling fluids. The experimental results show that under the same conditions, the higher the stirring speed, the better the emulsion stability of the drilling fluid;the longer the stirring time, the better the emulsion stability of the drilling fluid;the greater the oil-water ratio, the better the emulsion stability of the drilling fluid. And the test results of the emulsification stability of oil-based drilling fluids at high temperature and high pressure show that under the same pressure, as the temperature rises, the emulsion stability of oil-based drilling fluids is significantly reduced;at the same temperature, the With the increase in pressure, the emulsion stability of oil-based drilling fluids is in a downward trend, but the decline is not large. Relatively speaking, the influence of temperature on the emulsion stability of oil-based drilling fluids is greater than that of pressure.

Development of key additives for organoclay-free oil-based drilling mud and system performance evaluation

Traditional oil-based drilling muds(OBMs) have a relatively high solid content, which is detrimental to penetration rate increase and reservoir protection. Aimed at solving this problem, an organoclay-free OBM system was studied, the synthesis methods and functioning mechanism of key additives were introduced, and performance evaluation of the system was performed. The rheology modifier was prepared by reacting a dimer fatty acid with diethanolamine, the primary emulsifier was made by oxidation and addition reaction of fatty acids, the secondary emulsifier was made by amidation of a fatty acid, and finally the fluid loss additive of water-soluble acrylic resin was synthesized by introducing acrylic acid into styrene/butyl acrylate polymerization. The rheology modifier could enhance the attraction between droplets, particles in the emulsion via intermolecular hydrogen bonding and improve the shear stress by forming a three-dimensional network structure in the emulsion. Lab experimental results show that the organoclay-free OBM could tolerate temperatures up to 220 ?C and HTHP filtration is less than 5 m L. Compared with the traditional OBMs, the organoclay-free OBM has low plastic viscosity, high shear stress, high ratio of dynamic shear force to plastic viscosity and high permeability recovery, which are beneficial to penetration rate increase, hole cleaning and reservoir protection.

Calculation and application of partition coefficients of light hydrocarbons in oil-based mud system

To find out the relationship between the oil-based mud,the formation fluid and the extracted gas,we use a thermodynamic approach based on static headspace gas chromatography technique to calculate the partition coefficients of 47 kinds of light hydrocarbons compounds between nC5 and nC8 in two kinds of oil-based mud-air systems,and reconstruct the original formation fluid composition under thermodynamic equilibrium.The oil-based drilling mud has little effect on the formation fluid compositions in the range of nC5-nC8(less than 1%for low-toxicity oil-based mud and less than 10%for oil-based mud).For most light hydrocarbon compositions,the partition coefficients obtained by vapor phase calibration and the direct quantitative methods have errors of less than 10%,and the partition coefficients obtained by direct quantitative method are more accurate.The reconstructed compositions of the two kinds of crude oil have match degrees of 91%and 89%with their real compositions,proving the feasibility and accuracy of reconstructing the composition of original formation fluid by using partition coefficients of light hydrocarbon compositions between nC5 and nC8.

Evaluation of methyl ester sulphonate spacer fluid additive for efficient wellbore clean-up

Oil-based drilling fluid(OBDF)is used to drill through high permeable pay zone to prevent possible damage to the formation.However,the oil based drilling fluid leaves behind filter cake residue and oilwet surfaces which hinder cement bonding.Spacer fluid is usually introduced to clean up the wellbore prior to cementing job.This work presents a spacer fluid designed with environment-friendly anionic methyl ester sulphonate(MES)surfactant and evaluated through a series of experimental tests to ascertain its effectiveness to clean wellbore.Addition of methyl ester sulphonate to confected waterbased drilling fluid at high amount(0.15 g and 0.20 g)showed good rheological properties,compatibility with OBDF and cement and low contact angle on steel and sandstone in the range of 21.9°-34.7°.Furthermore,results show that it requires less amount of MES spacer fluid to revert oil-wet OBDF aqueous phase to water external continuous phase,validating the low contact angle measurements.Cleaning efficiencies for two best performing MES spacer fluids achieved 83.27%and 94.3%respectively.Shear bond strength were measured to be 1.3 MPa and 1.05 MPa for steel and sandstone respectively,above the minimum allowable shear bond strength for oil well cementing.Hence,MES spacer fluid can be used to clean up wellbores in high permeable formations and in well completion,where strong cement bonding is required.

基于仿真数据驱动的激光钻进气体喷嘴结构优化

激光钻进采用气体作为循环介质进行清孔,合理的气体流动特性是高效清孔的保障,气体喷嘴是影响气体流动特性的直接因素,其结构设计不合理会严重影响激光钻进的效率。针对激光钻进实验平台中的气体喷嘴,构建喷嘴基本型态,对影响气体清孔效率的喷嘴结构尺寸进行分析,制定仿真方案,通过Fluent模拟气体流场,对清孔效果进行分析,采用神经网络分析喷嘴结构及仿真结果,训练神经网络模型,得出最佳清孔效率时的喷嘴结构参数并进行验证,为喷嘴结构设计提供参考。

硅片盒喷雾清洗装置设计

为减少在半导体产业中因硅片盒洁净度引起的硅片清洗质量问题,提高硅片盒清洗效率并减少化学液用量,课题组设计了一种硅片盒喷雾清洗装置。该装置采用上部喷雾、下部浸入的化学液湿法清洗方式,结合雾化理论对喷嘴结构进行了参数设计,并对化学液喷雾硅片盒清洗机的骨架、槽体和化学液喷雾装置进行建模及仿真分析。研究结果表明:该装置在保证清洗效果的前提下,可以避免因硅片盒洁净度的不足而影响硅片的表面质量,同时减少了化学液的用量和废气的排放。该设计为硅片盒清洗提供了一种更高效且经济的参考方案。

抗高温油基钻井液的室内研究与应用

针对YJ3-X超深大斜度井三开井段存在的裂缝发育、井漏风险高、斜井段位移长、携砂困难、摩阻扭矩大、完井下套管作业时间长等钻完井难题,室内通过乳化剂的优选对现有抗高温油基钻井液体系配方进行了优化,并根据临井出现的复杂情况模拟该井可能出现的风险,评价了优化后钻井液体系的抗岩屑污染和盐水污染性能。试验结果表明,优化后的抗高温油基钻井液具有良好的流变性,抗温达180℃,破乳电压高达1366 V,高温高压滤失量低至2 mL,抗岩屑污染达20%,抗CaCl2盐水污染达30%,静置120 h后沉降因子为0.52,可满足井下各类复杂环境的作业需求。现场应用效果表明,优化后的抗高温油基钻井液流变性稳定,具有较低的黏度和较强的触变性,井眼清洁良好,起下钻和下套管摩阻低,井壁稳定,较好地满足了YJ区块大斜度深井作业需求。

超临界二氧化碳介质中晶圆清洗与选择性刻蚀研究进展

随着集成电路特征尺寸的逐渐减小,器件结构会要求更高的纵横比,常规湿法清洗由于表面张力很难进入晶圆深沟槽结构内部,不能满足更细线条工艺要求和高深宽比结构,直接影响沟槽内的污染物去除效果;常规湿法刻蚀各向异性差、结构坍塌严重、深沟槽刻蚀效果不明显;而等离子体干法刻蚀则存在刻蚀速率慢、光刻胶脱落和黏附、结构损伤、废气处理等一系列问题。超临界清洗和刻蚀技术是最具有前景的环境友好、无损伤技术,能够耦合刻蚀、清洗与干燥工艺为一体,且可以循环使用,安全环保,是晶圆制造过程中常规清洗和刻蚀的首选替代技术。综述了超临界二氧化碳中晶圆清洗与选择性刻蚀的研究进展,重点介绍了超临界二氧化碳共溶剂、微乳液体系在光刻胶剥离以及含硅基底选择性蚀刻中的应用,展望了超临界二氧化碳晶圆清洗和刻蚀存在的问题和发展趋势。

淹没水射流式贝肉清洗装置设计与试验

随着贝类预制菜产业的发展,基于贝肉的精加工预制食品逐渐在市场上推广,虽然市场上清洗装置品类较多,但是尚未有适合各类贝肉产品清洗的装备,存在清洗效率低、洗净率差和易破损等问题。本研究基于淹没水射流机理,设计了以淹没水射流为清洗动力的贝肉清洗装置,并对清洗装置进行Fluent-EDEM耦合数值模拟,确定清洗装置的关键结构参数范围。通过2个阶段试验论证了该清洗装置的合理性,第1阶段通过清洗正交试验得出,当射流口直径为10 mm,清洗量为14 kg,清洗时间为6 min,淹没水射流式清洗效果最佳;第2阶段进行了生产性对比试验,并以洗净率和破损率作为评价指标,对比3种清洗装置洗净率。结果显示:以扇贝裙边为清洗对象时,淹没水射流式清洗装置的平均洗净率为97.77%,且无破损现象,较螺旋桨式清洗装置洗净率提高了14.4%,较超声波式清洗装置洗净率提高了7.3%;以鸟蛤肉为清洗对象时,淹没水射流式清洗装置的平均洗净率为98.23%,较螺旋桨式清洗装置的洗净率提高了12.49%,较超声波式清洗装置洗净率提高了6.7%,且无破损情况。研究表明,淹没水射流式装置具有较好的清洗效果,具备产业化推广价值。

含亚乙烯基氢氟烯烃的研究进展

对含亚乙烯基的氢氟烯烃(v-HFOs)的合成路线和应用进行了综述。目前,在氟-氯交换、异构化、脱卤化氢、选择性加氢、加氢脱氯、调聚等合成v-HFOs的主要路线中,氟-氯交换的路线具有起始原料易得、容易实现大规模生产的特点,是合成v-HFOs的最佳路线。v-HFOs特殊的分子结构使其具有优异的传热性能、清洁性能、发泡性能和刻蚀性能,主要用作制冷剂、热泵工质、清洗剂、发泡剂和刻蚀剂,特别是E型v-HFOs[(E)-v-HFOs]具有优异的电绝缘性能,分别与其优良的传热性能和清洗性能进行多领域交叉,实现了(E)-v-HFOs应用于浸没式液冷和带电清洗的新场景。展望了v-HFOs的未来发展趋势,提出了今后的研究重点,应开发高活性的氟化催化剂,环保绿色的新型合成路线以及v-HFOs的新型应用。

XYX-1洗油型隔离液体系研究及应用

为提高页岩气井固井质量,降低接触污染的影响,开发了适合油基钻井液的洗油型隔离液XYX-1,可有效去除油膜,冲洗效率达到90.6%。对从川渝地区不同区块页岩气井场中选取了4种油基钻井液进行冲洗实验测试,结果表明该洗油型隔离液对4种油基钻井液常温下冲洗效率均大于90%。

双碳背景下油田清洁能源利用工艺可行性探讨

油田企业是能源行业的用能大户,采用清洁能源替代油田消耗的化石能源,降低油田碳排放,可有效助力我国双碳目标实现。根据油田用能结构特点和资源条件,以不同类型项目为实例,分析了高温采出液利用、热泵工艺、液化天然气(LNG)工艺、太阳能利用和风力发电等油田清洁替代工艺的应用条件、投资、运行费用和碳排放情况。结果表明,在相同的能耗下,水源热泵工艺单位综合造价为0.17×10^(4) CNY/kW、LNG工艺为0.40×10^(4) CNY/kW,二者相较于其他工艺投资低。风力发电和光伏发电不产生碳排放,太阳能光热、光伏发电和风力发电运行费用为0.018×10^(4)~0.040×10^(4) CNY/(kW·a),碳排放强度为0~0.45 t(/kW·a),这3种工艺相较于其他工艺运行费用和碳排放强度低。在高温采出液、油田伴生气和电力等条件均具备的条件下,应优先采用费用现值最低的高温采出液利用和水源热泵工艺,分别为1.20×10^(4) CNY/kW和1.29×10^(4) CNY/kW。在高温采出液和油田伴生气等条件不具备的条件下,优先采用LNG工艺和大型风机发电。与小型风机相比,大型风机发电经济效益更加明显,光伏发电经济效益介于大型风机和小型风机之间。在零碳油田建设中,应优先采用高温采出液利用和水源热泵工艺提供热力,采用大型风机或者光伏提供电力。