Devastating complication of negative pressure wound therapy after deep inferior epigastric perforator free flap surgery:A case report

BACKGROUND Thermal injuries on free transferred or replanted tissues resulting from loss of sensibility are an infrequent occurrence.They require immediate and appropriate management before they progress to an irreversible condition.Although negative pressure wound therapy(NPWT)can prevent wound progression by increasing microcirculation,the inappropriate application of NPWT on complicationthreatened transferred and replanted tissues can induce an adverse effect.CASE SUMMARY A 48-year-old woman who underwent immediate breast reconstruction with a deep inferior epigastric artery perforator free flap.While applying a heating pad directly to the flap site,she sustained a deep second to third-degree contact burn over 30%of the transferred flap on postoperative 7 d.As the necrotic changes had progressed,we applied an NPWT dressing over the burned area after en-bloc debridement of the transferred tissues on postoperative 21 d.After 4 d of NPWT application,the exposed fatty tissues of the flap changed to dry and browncolored necrotic tissues.Upon further debridement,we noted that the wound gradually reached total necrosis with a collapsed vascular pedicle of deep inferior epigastric artery.CONCLUSION Although NPWT has been shown to be successful for treating various wound types,the significant risk of NPWT application in short-lasting reconstructed flap wounds after thermal injury should be reminded.

Influence of Perforation on Formation Fracturing Pressure

Hydraulic fracturing treatments of oil wells are greatly affected by the perforation parameters selected. The three-dimensional finite element model together with the tensile criterion of rock materials is employed to systematically investigate the influence of perforation parameters, such as perforation density, perforation orientation, perforation diameter, and perforation length as well as wellbore ellipticity, in vertical wells on the formation fracturing pressure. Based on a six-month simulation research in the University of Petroleum, China, several conclusions are drawn for the first time. Perforation density and perforation orientation angle are the most important parameters controlling the formation fracturing pressure. As the perforation density increases, the fracturing pressure decreases, not linearly but progressively. The fracturing pressure increases with the perforation orientation angle only when the angle is less than 45 degrees, and the relationship becomes very flat when the angle is 45 degrees. However, with regards to the perforation diameter and perforation length, their influences are much slighter. The wellbore ellipticity has a significant effect on the formation fracturing pressure. It is obvious that fracturing pressure increases linearly with the ellipticity of the wellbore.

Mechanism and numerical simulation of pressure stagnation during water jetting perforation

When perforating with an abrasive water jet, it is possible that the pressure in the hole （perforation） will be higher than that in the annulus because of water jet blasting against the hole wall, which also is the theoretical basis for the technology of hydro-jet fracturing. This paper analyzes the mechanism of generating pressure stagnation in water jet hole, and puts forward a new concept of hydroseal. Then, the distribution of pressure in the hole was simulated with the finite element method. The simulation results showed that the pressure in the hole was higher than that in the annulus. Also, the lower the annular pressure （confining pressure） and the higher the blasting pressure, the greater the pressure difference. An experiment indicated that the cement sample was lifted up under the pressure stagnation in the hole, which proved the finite element simulation results obviously.

Calculation of Wave Pressure and Pressure Spectrum for Perforated-Pipe Breakwater

Standing waves are formed due to the reflection when waves meet vertical wall, therefore strong structures are needed to keep the wall stability under the serious wave attack. For the improvement of the working condition and increase of the stability of the wall, the lower reflecting breakwaters have attracted close attention Reports mostly from Japanese researchers are often concerned with the wall of caisson equipped with open windows. In this paper a kind of hollow-pipe perforated breakwater is examined which waves may partially perforate into the harbour basin. The wave in front of the wall can only form partial standing wave and wave force is reduced obviously. And the theoretical calculation of wave force and analysis of wave force spectrum are all derived. Comparison between the results from theoretical calculation and hydraulic modeling shows reasonable agreement.

COMPUTATIONAL FLUID DYNAMICS RESEARCH ON PRESSURE LOSS OF CROSS-FLOW PERFORATED MUFFLER

The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly, which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design.

Numerical Analysis of Perforation during Hydraulic Fracture Initiation Based on Continuous-Discontinuous Element Method

Perforation is a pivotal technique employed to establish main flow channels within the reservoir formation at the outset of hydraulic fracturing operations.Optimizing perforation designs is critical for augmenting the efficacy of hydraulic fracturing and boosting oil or gas production.In this study,we employ a hybrid finite-discrete element method,known as the continuous–discontinuous element method(CDEM),to simulate the initiation of post-perforation hydraulic fractures and to derive enhanced design parameters.The model incorporates the four most prevalent perforation geometries,as delineated in an engineering technical report.Real-world perforations deviate from the ideal cylindrical shape,exhibiting variable cross-sectional profiles that typically manifest as an initial constriction followed by an expansion,a feature consistent across all four perforation types.Our simulations take into account variations in perforation hole geometries,cross-sectional diameters,and perforation lengths.The findings show that perforations generated by the 39g DP3 HMX perforating bullet yield the lowest breakdown pressure,which inversely correlates with increases in sectional diameter and perforation length.Moreover,this study reveals the relationship between breakdown pressure and fracture degree,providing valuable insights for engineers and designers to refine perforation strategies.

Effect of perforation density distribution on production of perforated horizontal wellbore

To address the issue of horizontal well production affected by the distribution of perforation density in the wellbore,a numerical model for simulating two-phase flow in a horizontal well is established under two perforation density distribution conditions(i.e.increasing the perforation density at inlet and outlet sections respectively).The simulation results are compared with experimental results to verify the reliability of the numerical simulation method.The behaviors of the total pressure drop,superficial velocity of air-water two-phase flow,void fraction,liquid film thickness,air production and liquid production that occur with various flow patterns are investigated under two perforation density distribution conditions based on the numerical model.The total pressure drop,superficial velocity of the mixture and void fraction increase with the air flow rate when the water flow rate is constant.The liquid film thickness decreases when the air flow rate increases.The liquid and air productions increase when the perforation density increases at the inlet section compared with increasing the perforation density at the outlet section of the perforated horizontal wellbore.It is noted that the air production increases with the air flow rate.Liquid production increases with the bubble flow and begins to decrease at the transition point of the slug-stratified flow,then increases through the stratified wave flow.The normalized liquid flux is higher when the perforation density increases at the inlet section,and increases with the radial air flow rate.

A Mathematical Model and a Method for the Calculation of the Downhole Pressure in Composite-Perforation Technological Processes

Using the conservation equations for mass,momentum and energy,a model is elaborated to describe the dynamics of high-energy gases in composite-perforation technological processes.The model includes a precise representation of the gunpowder combustion and related killing fluid displacement.Through numerical solution of such equations,the pressure distribution of the high-energy gas in fractures is obtained,and used to determine crack propagation.The accuracy of the model is verified by comparing the simulation results with actual measurements.

Experimental and CFD Simulations of Pressure Loss through Perforated Plates

This paper presents the experimental pressure loss of water flow through perforated plates with geometry similar to the ones of the bottom end piece of a Pressurized Water Reactors （PWR） fuel element. Geometric features like the number, pattern and diameter of holes were evaluated as well as different inlet chamfers. The recovering pressure profile downstream of the plates was also measured. The experimental results were compared with numerical modeling performed with the commercial Computational Fluid Dynamics （CFD） code CFX 11.0. The analysis of the results shows that the standard k-e turbulence model presents the best compromise between computing time and accuracy for the calculation of the total pressure loss through the perforated plates tested.

AN EXPERIMENTAL INVESTIGATION ON THE IMPACT PERFORATION FAILURE OF WATER-FILLED-PRESSURIZED PIPELINES

Some experimental data recorded from impact tests on empty and water-filled pressurized mild steel pipes are presented. The pipes were supported as a three-span continuous beam and impacted laterally by a rigid indenter at the mid-span of middle span. Three kinds of indenter nose shapes were used: blunt-nose, hemisphere-nose and 90?conical-nose. The internal pressure ranged up to 20 MPa. The perforation failure modes and corresponding critical impact energies were obtained under different test conditions. The time-history curves of the internal pressure and impact force were given. The experiments show that the media filled in the tube greatly decreased the ballistic limit energy.

基于弹塑性井周的井筒-射孔地层破裂压力预测模型

深部“高地应力、高温度、高地层压力”的赋存条件,使储层呈现脆性-延性-应变硬化的塑性特征。针对深部塑性储层的水力压裂改造,存在人工裂缝起裂、延伸压力高的挑战。本文通过开展实时高温高围压的储层岩石三轴压缩实验,明确了储层岩石的塑性破坏特征。建立了深部储层岩石的塑性硬化本构模型,推导了井周的弹塑性应力场分布。结合断裂力学理论,建立了考虑井周塑性区的射孔尖端应力强度因子计算模型,并提出相应的迭代求解方法。采用模型预测室内实验与新疆某油田实际条件下的水力压裂裂缝起裂压力,模型预测结果与实测结果对比表明,考虑弹塑性井周应力场的破裂压力预测值比实际压裂预测值高,储层塑性特征不利于水力裂缝的起裂。模型预测值与油田实测结果的误差为6.6%,验证了模型的可靠性。考虑弹塑性井周的破裂压力预测模型可保证压裂设计的安全性,为深部储层的压裂方案设计提供有效指导。

射孔参数对砂砾岩储层压裂的影响

砂砾岩油藏具有应力差大、破裂压力高的特点,导致造缝难度大,如何降低破裂压力是安全压开储层的关键。将水泥与石英砂按3∶1混合并随机混入不同直径的鹅卵石和细碎石粒,制作边长300 mm的人造砾岩,使用水力喷砂射孔枪进行射孔,通过改变角度0~90°、深度1.5~6 cm模拟现场不同射孔方位角和炮眼深度,根据现场数据设置实验三向应力分别为9.4、19.3、24.8 MPa,排量为50 mL/min,压裂液黏度为45 mPa·s,开展室内水力压裂实验,分析射孔角度和射孔深度对裂缝起裂及破裂压力的影响。研究结果表明,射孔方向与最大水平主应力夹角为0°时破裂压力最低,为11.9 MPa,减小射孔方位角能够降低破裂压力3.55 MPa;射孔深度由1.5 cm增加至6.1 cm,破裂压力降低了4.63 MPa;当射孔孔眼附近存在砾石,破裂压力异常增高约10 MPa。建议通过合理优化射孔方位角,适当增加射孔深度,同时遴选砾石粒径较小且分选性较好的层段进行施工,提高压裂改造成功率。研究成果为制定玛湖射孔方案提供了参数优选的依据。

静压下带金属孔板声学覆盖层的耐压与吸声特性

为改善静水压力作用下传统声学覆盖层的吸声性能,提出了将金属孔板插入传统声学覆盖层中的水下声学覆盖层结构。以静力学方法研究了该声学覆盖层结构在不同静水压力下的形变情况。通过建立静水压力作用下的声学有限元方程,分析了该声学结构在不同静水压力下的吸声效果。与传统声学覆盖层相比,在静水压力为0~6 MPa时,该声学结构在中、高频段获得了更好的宽频吸声效果。此外,还讨论孔板厚度、孔板材料及孔板孔隙率对该声学结构吸声性能的影响。研究表明设计含金属孔板声学覆盖层可有效改善静水压力条件下水下声学结构的吸声性能。

海上油气井测试射孔峰值压力预测方法

为有效降低海上油气井射孔测试联作施工安全风险,以东海常用套管、油管、射孔枪、射孔弹组合为参考,建立了射孔管柱有限元数值模型。利用控制变量法,结合射孔峰值压力数值模拟结果,分析了总装药量、井筒初始压力、井筒爆炸空间等参数与射孔峰值压力的相关性,在此基础上,通过多元非线性回归建立了射孔峰值压力的计算公式。利用2口井射孔实测压力结果对公式进行验证,射孔峰值压力相对误差分别为6.1%和9.8%,在合理误差范围内。该公式可用于射孔作业前的峰值压力预测,为现场及时作出安全决策提供指导和支持。

水平井电缆射孔振动安全性分析

水平井射孔时,射孔弹爆炸会产生巨大的冲击波作用于管柱自身,并造成严重的管柱振动行为,甚至造成管柱与管串工具的损坏。为了研究水平井电缆射孔振动安全性,基于Hamilton原理,考虑射孔爆轰载荷的衰减、管柱-井壁的接触碰撞、超深井高温高压环境和管柱自生约束等因素的影响,建立了水平井电缆射孔纵-横-扭耦合非线性动力学模型。使用Newmark-β法对系统非线性离散方程组进行求解,并编制了相应的MATLAB计算程序。采用西南地区H1实例井井深结构和射孔参数,利用非线性振动模型探究了射孔轰爆载荷在超深井高温高压环境下对水平井电缆射孔纵-横-扭耦合振动的影响机理。研究结果表明:射孔枪过长会增大其横向位移、截面位移和振动幅值,过短则会导致管柱所受到Mises应力增大,故在考虑射孔枪安全使用和抑制振动的前提下,射孔枪长度20 m左右最合适。当射孔弹装药量超过20 g时,管柱所受到的最大Mises应力已经超过了其自身的极限应力值,在保证高效率射孔和管柱安全的前提下,射孔弹装药量应控制在15~20 g之间,这一参数与西南地区龙马溪组H2/3实例井使用的装药量相符合。研究结果可以为特定井的射孔弹装药量提供建议。

开孔式削角沉箱防波堤水动力特性模型试验研究

针对开孔式削角沉箱防波堤在设计条件下水动力响应稳定性评估问题,基于物理模型试验方法,在试验水槽中建立开孔式削角沉箱防波堤的缩尺模型,开展不同水位对应波浪条件作用下的结构稳定性、越浪量以及波压力分布模型试验研究,并根据试验结果对结构设计进行改进优化。研究结果表明,结构原始方案在极端高水位和设计高水位对应的波浪条件下护底块体发生明显移动且结构越浪量过大,在设计低水位对应波浪条件下沉箱结构发生显著累积位移,需要有针对性开展结构设计优化;提高胸墙的堤顶高程可以有效降低防波堤越浪量,当堤顶高程提升至15 m时,可以满足设计规范要求;防波堤迎浪面波压力分布中的最大值位置与水位呈正相关性,最大浮托压力出现在沉箱外侧底部,随后向尾部逐渐减小。模型试验充分论证了防波堤结构设计方案的可行性,为结构优化提供参考依据。

万米深地科探井射孔关键技术研究

万米深地科探井肩负着科学探索与油气发现的重大任务,在超深层油气勘探领域具有深远意义。万米深地科探井射孔完井过程中,将面临井筒极端高温高压、射孔管柱超长跨度、油层套管空间狭小等复杂问题,常规深层射孔技术已无法完全满足施工需求。为切实保障万米深地科探井顺利射孔完井,针对性地进行了万米深地科探井射孔关键技术研究,涵盖了特高温特高压射孔器研制、万米深地科探井射孔管柱力学研究、超深层射孔工艺改进。首先,分别对射孔器承压设计、配套火工品配方、药型罩配方与结构进行改进升级,并进行射孔器抗外压强度数值模拟,开展射孔器极限耐压、地面打靶等试验,将射孔器耐温耐压指标提升至260℃/245MPa。其次,针对射孔爆轰压力引起管柱剧烈振动失效问题,采用微元法、能量法结合哈密顿变分原理,建立全井筒射孔爆轰压力场模型及射孔管柱振动计算模型,对比现场采集的试验数据验证其准确性,初步形成万米深地科探井射孔管柱动力学计算程序。最后,基于以上万米深地科探井射孔保障软硬件,对万米深地科探井管柱传输射孔工艺进行配套升级。在BZ107井的现场试验,验证了配套射孔器、计算程序以及施工工艺的可行性,也为下一步万米深地科探井射孔完井顺利实施奠定了坚实基础。

三联作射孔爆轰井筒环空压力脉动规律研究

射孔—酸压—测试三联作(以下简称三联作)射孔爆轰导致井筒环空压力脉动,易造成射孔管柱窜通、断脱等事故。针对这一问题,在射孔爆轰压力脉动理论研究基础上,基于流固耦合理论建立了典型射孔枪—封隔器—套管结构的射孔爆轰井筒压力脉动预测模型;并开展了典型三联作超深井不同井筒环空初始压力、炸药质量、炸药类型对全井筒(封隔器下部井筒)环空压力脉动分布规律及影响研究。结果表明:井筒初始压力在50~125 MPa,炸药质量在15~40 g时,井筒初始压力越高、炸药质量越大,对应的井筒环空压力峰值越大;炸药质量相同时,TNT、HNS、RDX、HMX四种炸药中,RDX炸药造成的井筒环空压力峰值最大。因此,降低井筒初始压力和炸药质量,选用HNS和HMX类型炸药对降低射孔管柱失效风险具有积极意义。研究结果可为三联作射孔作业环空压力安全评估提供参考。

工作面动压区穿层钻孔瓦斯抽采技术及其效果分析

为解决突出煤层瓦斯抽采困难,回采过程中仍易造成瓦斯异常涌出,以及底抽巷瓦斯抽采利用率不足的问题,采用FLAC3D数值模拟软件对工作面回采期间超前支承压力分布及塑性区发育情况进行模拟,根据数值模拟结果有针对性地在底抽巷开展动压区瓦斯二次抽采,并通过瓦斯体积分数检测和瓦斯纯量计量对二次抽采效果进行评价。研究结果显示,工作面前方0~7m范围内为塑性区,垂直应力对煤体起到主要的破坏作用,煤体裂隙发育贯通,易于抽采;可将距工作面0~20m、20~60m和60m外分别划分为高效抽采区、有效抽采区和原始抽采区,各区瓦斯体积分数随着与工作面距离的增加而减小,直至进入原岩应力区而稳定;通过对动压区二次抽采瓦斯纯量进行计量可知,采用穿层钻孔对工作面动压区瓦斯开展二次抽采工作能够提高瓦斯抽采效率,减少工作面瓦斯涌出量。

射孔密度分布对水平井生产动态的影响

针对水平井产量受水平井井筒射孔密度分布影响的问题,建立两种水平井射孔密度分布模式(即分别增大井筒入口段和出口段射孔密度)下的数值模型对水平井两相流动进行模拟;将模拟结果与实验结果进行对比,验证本研究数值模拟方法的可靠性,在此基础上采用数值模拟研究两种射孔密度分布模式下井筒各流型阶段总压降、气水两相流体表观速度、空隙率、液膜厚度和产气量、产液量的变化规律。研究表明,当水相流量保持不变时,随着空气流量的增加,总压降、气水两相流体表观速度增大,空隙率增加,液膜厚度减小;相较于增大出口段射孔密度,当入口段射孔密度增大时,产液量和产气量均增加,且产气量随着气体流量增加而增大;产液量在泡状流阶段增加,而达到弹状流—分层流过渡点后开始降低,进入分层波状流阶段后产液量开始增加;无因次产液量在增大井筒入口段射孔密度的模式下更大,且随着径向气相流量的增加而增大。