醇对薄膜扩展剂扩展压力的影响

本文研究了醇对薄膜扩展剂扩展压力的影响.结果表明:醇对薄膜扩展剂的扩展压力有较大的影响,其影响程度与醇的分子结构有关.

顺层长钻孔多缝槽控制压裂裂缝扩展规律研究

预置缝槽控制是解决煤岩体水力压裂空白带的有效措施。以唐口煤矿为例,采用RFPA软件,分析煤矿井下工作面顺层长钻孔预置多缝槽控制压裂裂缝扩展规律。研究表明:多缝槽控制压裂水压主裂缝全部沿垂直于最小水平主应力的方向扩展,存在优势缝槽优先诱导产生水压裂缝扩展;随着预置缝槽密度增大,单侧水压主裂缝的长度减小而裂缝张开角增大,单侧最大水压主裂缝的长度变化大致符合线性关系;平均单侧最大水压主裂缝长度为26.3 m,平均裂缝张开角为11.8°,裂缝稳定扩展压力为18.0 MPa;合理的缝槽密度为0.04 m^(-1),对应的缝槽间距为25 m;单孔平均卸压2537 m^(2),水压主裂缝区域渗透率可以提高100~200倍。

裸眼临时弃置井水泥塞-地层界面剥离数值模拟

地层流体沿水泥塞-地层界面运移并泄漏至地面会影响裸眼临时弃置井井筒密封完整性。为此,建立基于Cohesive单元方法的水泥塞-地层系统三维有限元模型,模拟水泥塞-地层界面裂缝的萌生及扩展过程,并与现有微环隙计算模型进行对比以验证模型的可靠性。定量分析了水泥塞-地层界面剥离过程中裂缝发展形态、裂缝扩展压力和裂缝剥离高度的变化,并对水泥塞力学参数、界面胶结强度及水平地应力差进行了敏感性研究。研究结果表明:较大的界面胶结强度和较高的水泥塞弹性模量有益于增大水泥塞-地层界面裂缝扩展压力,降低裂缝剥离高度,减小界面剥离失效的风险;在非均匀水平地应力条件下,地应力差越大,界面越容易剥离;水泥塞泊松比对裂缝扩展压力及剥离高度影响较小。研究结果为预测水泥塞-地层界面剥离导致的裸眼临时弃置井井筒密封完整性失效提供了有效方法。

岩体水力定向压裂技术研究

水力压裂是高效破岩技术之一,在煤岩层增透、卸压控制等方向应用较多。但是,目前就煤岩体定向压裂控制方向的研究相对较少。为突破常规煤岩体压裂限制,本文研究水力破岩压裂技术的可控性及适用性。为分析水力压裂的定向控制性,开展了理论和数值分析。结果表明,在λ<1时,起裂、扩展压力随λ增加而增加,在λ>1时起裂压力、扩展压力随λ增加而减小,主裂纹沿最大主应力方向扩展;在近似等围压条件下,定向控制裂纹可以引导和控制破岩主裂纹的扩展,且定向控制裂纹与最大主应力的方位角越小,定向控制裂纹对主裂纹引导作用越明显。基于理论和数值分析结果,可知水力定向压裂技术具有较好的应用价值。

由非完整压裂曲线解释地应力的方法

水力压裂的地破试验是测量深部原位地应力的有效方法,从完整地破试验曲线可以解释出地应力,但现场地破试验大多得到非完整地破试验曲线,无法从中解释出地应力。利用弹性力学方法,提出了裂缝扩展压力与两个水平主应力的关系,结合裂缝起裂压力与两个水平主应力的关系进行地应力解释。琼002井4 340 m处地应力解释结果表明:由非完整压裂曲线解释地应力方法与传统解释方法得到的最大地应力相差0.53%,最小地应力相差0.15%。由非完整压裂曲线解释地应力的方法具有可靠性与准确性。

水平井压裂过程中水泥环界面窜流模拟分析

现有研究不仅未定量分析水平井分段压裂过程中压裂液侵入水泥环界面的窜流长度,而且也未考虑压裂液流速等因素对界面脱黏的影响。为此,基于Cohesive单元方法,建立水泥环界面窜流模型,模拟压裂液侵入水泥环界面造成的窜流现象,对比水泥环-地层界面和水泥环-套管界面发生窜流的难易程度,研究水泥环弹性模量、泊松比及压裂液流速等因素对窜流长度的影响,并结合油田实例进行分析。分析结果表明:水泥环-地层界面更容易发生窜流;增大水泥环弹性模量有利于降低界面窜流的风险,水泥环泊松比对界面窜流的影响不大;在压裂施工的过程中若检测到窜流的发生,在保证压裂正常进行的同时,可以适当减小施工排量来降低窜流的风险。所得结论可为现场施工提供借鉴。

Force analysis and experimental study of pure aluminum and Al-5%Ti-1%B alloy continuous expansion extrusion forming process

The deformation zone of CONFORM extrusion was divided into primary gripping zone,gripping zone,conical expansion chamber zone,cylindrical zone and sizing zone of die,and corresponding force equilibrium equations were established using the Slab method.The deformation force formulae of CONFORM machine at any wrapping angle with an expansion chamber were obtained.Experiment on pure aluminum and Al-5%Ti-1%B alloy was conducted on the CONFORM machine self-designed.The resistance to deformation of Al-5%Ti-1%B alloy at the deformation temperature of 400℃ and the strain rate of 3.07 s-1 was measured to be 50 MPa using Gleeble-1500 thermal simulation machine.The calculation results of deformation forces for CONFORM process with an expansion chamber for pure aluminum and Al-5%Ti-1%B alloy were given.The experimental CONFORM radial force is in agreement with the radial force obtained by theoretical formula.

Extrusion force analysis of aluminum pipe fabricated by CASTEX using expansion combination die

To determine the extrusion force of pipe fabricated by continuous casting and extrusion (CASTEX) using an expansion combination die, the metallic expansion combination die was divided into diversion zone, expansion zone, flow dividing zone, welding chamber, and sizing zone, and the corresponding stress formulae in various zones were established using the slab method. The deformation zones of CASTEX groove were divided into liquid and semisolid zone, solid primary gripping zone, and solid gripping zone, and the formulae of pipe extrusion forces were established. Experiments were carried out on the self-designed CASTEX machine to obtain the aluminum pipe and measure its extrusion force using the expansion combination die. The experimental results of radial extrusion force for aluminum pipe are in good agreement with the calculated ones.

Crack propagation and hydraulic fracturing in different lithologies

We simulated hydraulic fracturing in different lithologic rocks in the horizontal drilling by using the true physical model experiment and large rock specimens, carried out the real-time dynamic monitoring with adding tracer and then did post-fracturing cutting and so on. Based on this monitoring results, we compared and assessed the factors affecting expansion in shale, shell limestone, and tight sandstone and the fracture expansion in these rocks. In shale, the reformed reservoir volume is the highest, fracture network is formed in the process of fracturing. In tight sandstone, the fracture surface boundaries are curved, and the fracture surface area accounts for 25–50% of the entire specimen. In shell limestone, the complexity of the fracture morphology is between shale and tight sandstone, but no fracture network is developed. Brittleness controls the fracture surface area. In highly brittle rocks, the fracture surface area is high. Fracture toughness mainly affects the initiation and propagation of cracks. A fracture network is formed only if bedding planes are present and are more weaker than their corresponding matrix. The horizontal in situ deviatoric stress affects the crack propagation direction, and different lithologies have different horizontal in situ deviatoric stress thresholds. Low f luid injection rate facilitates the formation of complex cracks, whereas high fluid injection rate favors the development of fractures. Fluid injection weakly controls the complexity of hydraulic fracturing in low-brittleness rocks, whereas lowviscosity fracturing fluids favor the formation of complex cracks owing to easy enter microcracks and micro-pore. Displacement has a greater impact on high brittle rocks than low brittle rocks.

心理分离研究进展

心理分离指的是个体在非工作时间里从工作中分离出来,个体不仅身体上远离工作场所,精神上也摆脱掉工作的事情,对员工工作压力的恢复过程非常关键。首先,文本概述了心理分离的概念及其进展;其次,论述了心理分离研究现状;最后,阐述了心理分离的已有研究存在的问题和未来研究的方向。

Numerical simulation of hydraulic fracture propagation in weakly consolidated sandstone reservoirs

Frac-packing technology has been introduced to improve the development effect of weakly consolidated sandstone.It has double effects on increasing production and sand control.However,determining operation parameters of frac-packing is the key factor due to the particularity of weakly consolidated sandstone.In order to study the mechanisms of hydraulic fracture propagation and reveal the effect of fracturing parameters on fracture morphology in weakly consolidated sandstone,finite element numerical model of fluid-solid coupling is established to carry out numerical simulation to analyze influences of mechanical characteristics,formation permeability,fracturing fluid injection rate and viscosity on fracture propagation.The result shows that lower elastic modulus is favorable for inducing short and wide fractures and controls the fracture length while Poisson ratio has almost no effect.Large injection rate and high viscosity of fracturing fluid are advantageous to fracture initiation and propagation.Suitable fractures are produced when the injection rate is approximate to3–4m3/min and fluid viscosity is over100mPa?s.The leak-off of fracturing fluid to formation is rising with the increase of formation permeability,which is adverse to fracture propagation.The work provides theoretical reference to determine the construction parameters for the frac-packing design in weakly consolidated reservoirs.

Finite element modeling for analysis of cracked cylindrical pipes

The characteristic properties of shell element with similar shapes are used to generate a so-called super element for the analysis of the crack problems for cylindrical pressure vessels. The formulation is processed by matrix condensation without the involvement of special treatment. This method can deal with various singularity problems and it also presents excellent results to crack problems for cylindrical shell. Especially,the knowledge of the kind of singular order is not necessary in super element generation; it is very economical in terms of computer memory and programming. This method also exhibits versatility to solve the problem of kinked crack at cylindrical shell.

气举阀的特性试验和数据相关

本文提供了一种测试气举阀特性数据的装置,可在流动工况下确定阀杆实际的动态位置。并对所需数据的试验方法作了说明。

Wing crack propagation model under high hydraulic pressure in compressive-shear stress state

A new wing crack model subjected to hydraulic pressure and far-field stresses was proposed considering the effect of hydraulic pressure in wing crack and the connected part of the main crack on the stress intensity factor at the wing crack tip. With the equivalent crack length Ieq of the wing crack introduced, the stress intensity factor Kl at the wing crack tip was as- sumed to the sum of two terms： on one hand a component K1^（1） for a single isolated straight wing crack of length 21, and subjected to hydraulic pressure in the wing crack and far-field stresses; on the other hand a component K1（2） due to the effective shear stress induced by the presence of the equivalent main crack. The lateral tensile stress and hydraulic high pressure are the key factors that induce crack propagation unsteadily. The new wing crack theoretical model proposed can supply references for the study on hydraulic fracture in fractured masses, hydraulic fracturing in rock masses.

Experimental investigation of an adjustable ejector for CO_2 heat pump water heaters

An adjustable ejector expansion device for a CO2 heat pump water heater (HPWP) is proposed to improve the system performance. It has been designed to investigate experimentally the effects of the motive nozzle throat area of the ejector, entrained flow pressure, back pressure and primary flow pressure on the entrainment ratio. Experiments based on different motive nozzle throat areas were conducted and the results of the prototype ejector using CO2 as working fluid are presented. The results show that an adjustable ejector can achieve high performance and work well in a wide range of working conditions.

双金属衬里复合管内衬塌陷失稳三维有限元研究

针对双金属衬里复合管的内衬塌陷失稳问题,建立了三维有限元力学模型,研究了受限内衬临界失稳载荷与后屈曲构型之间的相互关系,并将计算结果与二维平面应变有限元模型的计算结果进行了对比,最后通过实物实验评价了两种模型的适用性。结果表明:使用三维有限元模型计算的临界失稳载荷值与实验结果的相对误差为1.33%;衬管的临界失稳载荷值是缺陷敏感的,0.6%的不圆度缺陷会使其临界失稳载荷下降约50%;二维模型与三维模型(长径比L/D>6)计算的受限内衬的临界失稳载荷值几乎无误差,但对于计算衬管的临界坍塌扩展传播压力Ppc,三维模型的计算结果更接近实验结果。建立的三维有限元力学模型可以准确地求解受限内衬的临界失稳行为,为双金属衬里复合管的内衬止屈设计、保证集输系统安全运行提供了理论依据。

量子化学模型方法在机械力化学中的应用

机械力化学作为一种无需溶剂的绿色化学技术得到广泛关注。然而,机械力化学反应机制需要从原子和分子尺度上深入理解力诱导的化学反应。在过去的20年中,量子化学模型方法在机械力化学机理研究中得到广泛应用,高精度量化计算可得到外力下变形分子的几何结构、能量、过渡态等诸多性质。本文介绍了目前机械力化学领域的主流量子化学模型的基本原理,同时也关注了这些模型方法在软件上的具体实现,并借助典型的案例阐述了量子化学模型在解释机械力化学机理中的作用与价值。