【作者】 侯铎；

【导师】 施太和； 李颖川；

【作者基本信息】 西南石油大学 ， 油气田开发工程， 2013， 博士

【摘要】 随着全球对油气资源需求量的不断增长,石油天然气开发开采所面临的形势日趋复杂,在高温、高压、高矿化度地层水以及高含H2S、CO2腐蚀性介质的酸性环境中,井筒的腐蚀问题日趋严重,由于氢损伤作用引发环境开裂,导致油井管发生穿孔、漏失、断裂等失效问题,增大开采作业难度。目前,对于油井管氢损伤、环境开裂的实验方法都是基于断裂力学评价标准,应力环A法及DCB法等测试结果平行性和重现性差、数据离散性大,实验结果应用价值严重受限,无法为现场施工、油井管强度设计和环境开裂适用性评价提供有力依据。本文以石油工程、管柱力学、断裂力学、腐蚀电化学理论以及强度理论为依据,设计制造70MPa、200℃动态循环多相流高温高压釜、恒载荷、三点弯曲应力腐蚀实验装置,建立高温高压恒载荷应力腐蚀实验方法、慢拉伸应力腐蚀实验方法、三点弯曲应力腐蚀实验方法,分别测试油井管C110-1和C110-2在高温高压静载(80%σs恒定拉应力或剪应力)、动载(3.5×10-4mm/s应变速率)服役工况中强度和韧性受氢渗透作用的损伤程度,计算氢损伤造成的强度衰减率和塑性损伤率,表征氢损伤对环境开裂作用特性,建立氢渗透系数与强度损伤可靠性方程,利用正交试验方法研究氢致强度、塑性损伤规律,氢致腐蚀作用加速以及环境开裂规律,推导油井管材在各种条件下的应力强度因子计算公式确定应变能计算方法,根据油井管应力腐蚀开裂特性以及强度、塑性损伤规律建立环境开裂适用性评价方法以及应变能判据的基本准则。研究油井管材在不同环境工况中应变老化现象,分析氢损伤对硬化、脆化和应变老化的作用机理。依据油井管抗拉强度、屈服强度和硬化指数受氢损伤作用的变化特征,建立氢致强度衰减规律；根据氢损伤作用对油井管冲击韧性、断后伸长率、断面收缩率、表面损伤和断口特征的影响作用,建立氢致塑性损伤机理；通过氢渗透行为实验确定材料强度、韧性损伤大小与氢渗透系数、可扩散氢浓度之间的关系,建立计算氢损伤作用对强度衰减的可靠性方程。根据应变能量损伤以及第四强度理论,设计L16(45)正交试验分析恒载荷应力腐蚀实验、慢拉伸应力腐蚀实验和三点弯曲应力腐蚀实验油井管材在H2S、CO2酸性环境中应力应变曲线下移的原因,根据油井管材在服役工况中的损伤规律确立应变能判据,通过实验测试、理论计算两方面建立可靠、稳定的油井管环境敏感开裂适用性评价方法。从完善油井管材强度设计、适用性评价和提高油井管材综合性能三个方面研究不同工况环境中油井管材应力强度因子的计算方法,研究油井管在静载、动载服役环境中裂纹尖端应力场大小及其环境开裂特性,提出油井管出厂、使用前进行适用性评价的重要性和必要性,建立油井管环境敏感开裂适用性评价方法及其详细操作规程,为现场油井管选材和适用性评价提供方法和理论依据。更多还原

【Abstract】 With the rising global demand for oil and gas resources, the situation of the oil and gas exploration has been increasingly complicated. Corrosion of tubing and casing remains a key obstacle for sustaining operational success in the acidic environment of high temperature, high pressure, and high salinity formation water with high levels of H2S, CO2, CH4 and other corrosion medium. The difficulty of oilfield development is increased due to the perforation, leakage, and rupture failure of tubing and casing caused by hydrogen damage resulting in environmental cracking. Currently, the experimental method of hydrogen damage and environmental cracking are based on the evaluation criteria of fracture mechanics. The test results of stress ring A method and DCB method are so poor in reproducing and paralleling data, and have great data discreteness that the application of the experimental results is severely limited and cannot supply evaluation principle for oilfield construction, strength design and environmental cracking.Based on the petroleum engineering, wellbore mechanics, fracture mechanics and the theory of electrochemical corrosion and strength, the dynamic multiphase flow autoclave, constant load, three-point bending test device is designed and manufactured at the pressure of 70 MPa and temperature of 200℃. The high temperature and high pressure (HTHP) constant load stress corrosion test method. HTHP slow strain rate tensile (SSRT) stress corrosion method, and HTHP three-point bending stress corrosion method are used to test the strength and toughness loss of well pipes C110-1 and Cl 10-2 under HTHP static load (80% σs,constant tensile stress or shear stress) and HTHP dynamic load (3.5×10-4mm/s strain rate) while the intensity and plastic loss is calculated caused by hydrogen damage. The characteristic of environmental cracking caused by hydrogen damage is represented and the reliability equations between hydrogen permeability coefficient and strength loss is formulated. The strength decay, plastic loss, and accelerating corrosion rate induced by hydrogen are studied by the method of orthogonal combination experiment while the environmental cracking is also considered. The Kic of the well pipes under different corrosion environments is calculated, and the environmental cracking evaluation method and strain energy criterion are established according to the characteristics of SCC, strength decay and plastic loss of the well pipes.Evaluation study on strain aging phenomenon of well pipes under different conditions has been conduced while the mechanism of hardening, embrittlement and strain aging caused by hydrogen damage is studied. The strength loss based on tensile strength, yield strength and hardening exponent of the well pipes as a result of hydrogen damage is analyzed. The toughness loss is determined on the basis of hydrogen damage affecting impact toughness, elongation, section shrinkage, surface damage and fracture appearance of the well pipes. According to the test of hydrogen permeation, the relationship between hydrogen damage and hydrogen permeability coefficient or concentration of diffusion hydrogen is determined so that reliability equation about hydrogen damage and strength loss is established.According to the fourth strength theory and strain energy damage, the L16(45) orthogonal experiment is designed to analyze the stress-strain curves of well pipe slope down in acidic environment detected by HTHP constant load stress corrosion test, HTHP SSRT stress corrosion test and HTHP three-point bending stress corrosion test. With the results of well-pipe hydrogen damage in service condition, strain energy criterion is determined while a reliable and stable applicability evaluation method for environmental sensitive cracking of well pipes is put forward depending on experimental and theoretical results.The stress intensity factor calculation method of well pipes in different acidic environment is proposed by improving strength design, applicability evaluation and enhancing mechanical properties of the well pipes. The size of the stress field of the crack tip and characteristic of environmental cracking under static and dynamic load service conditions are analyzed. The applicability evaluation on well pipes in factory and in wellbore are not only important but also necessary. The evaluation method and procedures for environmental sensitive cracking applicability of well pipes are established to supply the method and theoretical basis for the material selection and fitness evaluation of well pipes.更多还原