大尺寸储气库套管抗挤强度影响因素试验研究

根据大尺寸储气库套管受到外挤载荷时的受力及变形特点,通过室内全尺寸试验分析套管椭圆度、钢级、径厚比等因素对大尺寸储气库套管抗挤强度的影响,并利用试验数据对现有的套管抗挤计算公式进行修正。将套管变形分为弹性和塑性变形两个阶段,建立套管弹、塑性变形受力计算模型,利用能量平衡方程推导出套管抗挤强度计算公式,分析初始椭圆度、套管钢级和径厚比对大尺寸储气库套管抗挤强度的影响,将修正前后的计算结果与试验结果进行对比分析。研究结果表明:利用本文建立的套管挤毁受力模型能够很好地预测带有初始椭圆度的大尺寸储气库套管抗挤强度,计算公式简单、准确,适用于不同椭圆度、屈服强度和径厚比的套管抗挤强度计算,能够弥补现有大尺寸储气库套管规范的不足及缺失;套管的抗挤强度随着初始椭圆度和径厚比的增加而降低,随着套管钢级的增加而增加;内、外椭圆度对大尺寸储气库套管抗挤强度影响具有耦合作用,在制造过程中要严格控制椭圆度及其跳跃性,建议制订相应的储气库大尺寸套管内壁椭圆度控制规范以满足相应套管的需求。     

钻井过程中计算磨损套管强度的理论研究

油气井钻井过程中，由于钻具和套管相互摩擦，造成套管内壁磨损并引起磨损套管抗挤强度降低，导致某段油气井报废或整口油气井报废。因此，套管柱设计就尤为重，更重的是建立新的计算方法适应新的磨损问题。本文通过对计算方式的比较研究，得出了新的更加科学的计算磨损套管抗挤强度的算法。     

技术套管磨损程度及剩余强度分析

在大位移井、大斜度井、水平井和深井钻井中,或者在狗腿严重度较大的井段,或者在技术套管下人后的长裸眼钻井过程中,常常出现套管磨损问题。由此而诱发的套管抗挤强度和抗内压强度降低问题制约了油井的后续完井测试作业的顺利进行,影响了油井寿命,严重时还会导致某段油井报废和整口油井报废。国内外学者研究了许多措施来减缓套管磨损问题。本文在技术套管磨损程度及剩余强度分析的基础上,吸收国内外学者的减缓套管磨损问题成果,提出在技术套管磨损程度及剩余强度分析的对策。     

非均匀载荷作用下偏心磨损套管稳定性准则

采用小参数摄动法建立了非均匀载荷作用下具有初始椭圆度的磨损套管稳定性准则,根据计算得到的磨损套管相对应变及其临界值之间的关系确定磨损套管是否发生挤毁失效。分析了磨损套管相对应变及其临界值与套管外径、壁厚、磨损深度、载荷非均匀度、初始椭圆度之间的关系。套管外径增加导致失稳临界应变减少,磨损套管保持其稳定的壁厚也随之增加。非均匀载荷作用下磨损套管相对应变与初始椭圆度之间是线性关系,套管初始椭圆度越大,相对应变越大。相对应变与载荷非均匀性之间是抛物线关系。磨损套管载荷非均匀性越大,相对应变越大。非均匀载荷作用下磨损套管的相对应变随磨损深度线性增加。该准则能够用于评价非均匀载荷作用下含磨损缺陷套管的井筒的完整性。     

超深井下套管新技术探索

影响我国深井超深井的技术难点是多方面的,特别是在新的区块钻第一口探井时,由于地质上不确定因素较多.井下复杂情况也较多,工程技术上也存在较多的难点需要解决。在此我们对深井、超深井油套管选择与管件设计,固井完井方面的关键技术作以探讨。     

双层组合套管抵抗非无效载荷能力分析

在抵抗非均匀载荷方面，双层组合套管具有明显的优点。由于应力应变关系的复杂性，用理论方法求解非均匀荷载作用下双层套管的传递系数十分困难。本文用有限元方法计算了不同类型非均匀载荷作用下的传递系数，对其变化规律进行了分析。在大量计算结果的基础上，进行了传递系数计算公式的回归分析，给出了椭圆分布载荷作用下传递系数拟合曲线及回归公式。这些结果弥补了理论分析的不足，为双层组合套管的设计提供了一种有效的计算依据。计算过程还证实了双层组合套管的一些实验结果，对该种套管的特点有了进一步的认识。     

浅析钻井液性能对套管抗磨损的影响

在深井、超深井的钻进过程中,钻井周期长,钻杆与套管之间的摩擦时间长,套管磨损是一个不容忽视的问题,而钻井液作为套管和钻杆之间的润滑介质,研究其性能对套管抗磨损的影响具有重要的现实意义。本文通过对前人所做实验的分析,提出了一些改善钻井液性能、合理保护套管的具体措施,从而为减缓套管的磨损,延长套管的使用寿命提供了一定参考。     

含磨损缺陷套管抗挤强度的数值分析

为了确定在内壁上有新月形磨损缺陷套管的抗挤强度,本文采用有限元法,分别按平面应力、平面应变和空间问题进行分析。研究结果表明,其抗挤强度远小于按最小壁厚从手册中查得的值,它随磨损缺陷深度的增加和半径的减小而降低：当磨损缺陷的轴向尺寸足够大时,则完全可以按照平面问题处理．     

利用套后成像测井技术分析某井套管泄漏原因

某井套管柱试压发生了泄漏,随后对套管柱进行了套后成像测井(IBC),根据测井结果分析了影响套管泄漏的因素。通过分析套管磨损对其承压能力的影响,认为套管泄漏与套管内壁磨损有很大关系;依据测井原理对套管泄漏位置进行了分析,认为IBC测井无法直接准确判定较细的套管穿透裂纹的确切位置,只能给出磨损最严重、最有可能发生漏失的位置;通过分析固井质量对使用寿命的影响,认为套管柱多处磨损后发生了椭圆变形,与固井质量不好,套管受到非均匀载荷有关。     

非均布荷载作用下震后地下拱结构抗动载能力评估

为评估非均布荷载作用下震后地下防护结构的抗动载能力,针对震前震后三种结构型式,给出了动荷载动力系数的确定方法,推导出了非均布荷载作用下地下拱形结构的弯矩和拱脚推力的计算公式。针对工程实例,计算了不同损伤型式的拱结构承受非均布动载时的结构内力,从而给出了非均布荷载作用下震后结构的抗动载能力评估方法。研究表明:抗弯设计条件下震后拱结构抗非均布动载能力将降低约13%,而在抗剪设计条件下由于裂缝的穿透震后拱结构抗非均布动载能力将降低50%以上。     

Experimental investigation of the failure mechanism of P110SS casing under opposed line load

Many studies focused on casing collapse strength under uniform load have been done, and the API 5C3 and ISO standards have been formed. However, only a limited number of researches on collapse failure mechanism of casing have been done under non-uniform load, especially experimental study, although the non-uniform load has a great impact on casing collapse strength. Hence, the collapse experiment is conducted for P110SS casing under opposed line load by using electro hydraulic servo pressure testing machine. The displacement variation rules of P110SS casing have been obtained under opposed line load. The strain of casing is measured in the process of collapse testing by the method of gluing strain-gauge on the outside surface of P110SS casing. The initial yield load of casing, instability load of casing and the yield load, stress-hardening rate, strain-hardening rate of casing after hardening are obtained. The stress-strain rules of casing after hardening are analyzed. The hardening characteristic and collapse failure mechanism of P110SS casing have been clarified under non-uniform load (under opposed line load). Experimental results can provide important references for the theoretical study on failure mechanism and collapse strength of casing under non-uniform load.     

注汽井套管的三轴预应力设计

以暴露于热蒸汽中的目的层套管为研究对象,根据弹性力学理论,首先给出了套管在热应力和非均匀地应力作用下的三轴应力表达式,然后利用对套管施加预应力来降低套管的轴向热应力,以使得套管的有效应力控制在相应温度下套管的最小屈服极限内为原则,得到了热采井套管三轴预应力设计方法,并对辽河油田常用的N80钢级套管进行了预应力设计分析,给出了该套管在不同注汽温度和井深条件下所应使用的径厚比及相应的预应力值。研究表明,在实际注汽过程中适当增加注汽压力可以提高套管的安全性,传统的单轴预应力设计及只考虑热应力的三轴预应力设计结果偏于保守,建议以后注汽井在进行预应力设计时应考虑热应力和实际非均匀地应力的共同作用。     

Experimental study the collapse failure mechanism of cemented casing under non-uniform load

Under non-uniform in-situ stress, the casing collapse failure often happens easily, and especially in soft rock the problem is more serious. In addition, only the few scholars do some studies about failure mechanism of cemented casing under non-uniform in-situ stress which has a strong effect on collapse properties of cemented casing, especially testing investigation. Hence, the collapsing test was performed for cemented casing under non-uniform load (NFL) by adopting self-developed testing equipment, by which the radial deformation of cemented casing and damage rules of cement sheath have been measured and the stress-strain laws of cemented casing are obtained during the testing process by the electrical method. The initial yield load and plastic limit load of cemented casing as well as the subsequent yield load have been obtained. By analyzing testing data, the stress-hardening rate and strain-hardening rate after hardening have been determined. The effects of cement sheath on collapse properties of P110SS casing and strain and deformation laws of P110SS casing after hardening have been obtained. The hardening character and failure mechanism of cemented casing have been figured out under NFL.     

Investigation of the ultimate residual strengthen of a worn casing by using the arc-length algorithm

The accurate prediction of the ultimate residual strength (URS) (including collapse, burst, and tensile strength) of worn casing is important in the design and safety assessment of casings for the oil and gas industry. Based on the true stress–strain constitutive relationship of P110 steel, this paper establishes a three-dimensional (3D) finite element model (FEM) to obtain the URS of worn casing by using the arc-length algorithm. The effects of worn defect length, wear percentage, drillstring diameter, and casing thickness on the URS are investigated. Moreover, three full-scale experiments on casings with different wear percentages are conducted to verify the accuracy and reliability of the 3D FEM and of the algorithm. The validation proves that the URS of worn casing can be predicted by the 3D FEM to a satisfactory degree of accuracy. The URS has an exponential relation with defect length, but a linear relation with wear percentage, drillstring diameter, and casing thickness. The effects of numerous factors on the URS are also studied. Regression analysis is conducted on the basis of 3D FEM predictions, and the corresponding design equations for worn casing are presented.     

长庆油田渗氮套管的耐腐蚀性能研究

针对长庆油田油井套管腐蚀问题,采用并评价了真空渗氮工艺.该工艺处理套管表面形成氮化层,在不降低原有机械性能的前提下提高了表面耐磨、抗蚀能力.经室内、现场试验发现,渗氮管在长庆油井腐蚀情况下的耐腐蚀性能优良.此外,还就渗氮层在不同弯曲、拉应力条件下的微观表面变化对使用性能的影响进行了研究,确定了渗氮套管下井条件.并于2003年首次在2口井得以应用.该工艺为低产低渗透油田的防腐蚀研究提供了新思路.     

Plastic collapse load of corroded steel plates

Corrosion is one of the detrimental phenomena which reduces strength of structures. It is common practice to assume a uniform thickness reduction for general corrosion. Since the actual corroded plate has rough surfaces, to estimate the remaining strength of corroded structures, typically a much higher level of accuracy is required. The main aim of present work is to study plastic collapse load of corroded steel plates with irregular surfaces under tension. Non-linear finite element method by using computer code ANSYS was employed to determine plastic collapse load. By comparing the results with uniform thickness assumption, a reduction factor was proposed. It is found that by uniform thickness assumption, plastic collapse load of corroded plates are overestimated.     

进口φ39．7mm套管在固井过程中脱扣原因分析

某井进口φ339．7mm电阻焊（ERW）套管固井事故进行了全面调查研究,通过对磁性定位测井CCL曲线反映的套管柱失效形貌和对井下捞出的套管残片形貌进行分析认为,套管柱在固井过程中发生了脱扣,脱扣位置在第5根套管的工厂连接端。通过对套管的螺纹加工、材料和上扣连接质量等进行分析和对套管柱在固井过程中的受力状态进行计算认为,套管所受栽荷远小于其连接强度,排除了过载导致套管脱扣的可能性,认为套管接头是在固井期间首先松动之后才发生脱扣的;套管接头在井下松动的原因是由于套管柱在固井过程中受到了很大的震动载荷;套管接头从工厂上扣端松动脱扣的原因主要与工厂上扣扭矩偏小有关．     

P110石油套管水压试验开裂原因分析

通过对材料的化学成分分析、断口分析及金相检验,对φ177.8 mm×11.51 mm P110石油套管水压试验后出现的管体异常开裂现象进行分析。结果表明:导致管体纵向开裂的原因是该套管管体组织内分布着大型夹杂物,它的存在破坏了材料组织的连续性,削弱了横向抗拉强度,在应力集中的条件下,局部应力超过实际的抗拉强度从而产生开裂。