【作者】 郭建华；

【导师】 施太和；

【作者基本信息】 西南石油大学 ， 油气井工程， 2013， 博士

【摘要】 我国H2S超30g/m3的高含硫天然气探明储量近1万亿m3,普遍具有埋藏深、高温、高压、地质条件复杂、多位于人口稠密地的特点,其资源利用面临腐蚀性强、成本高、毒性大、事故后果严重等难点。自2009年Lg气田、Pg气田相继投产以来,部分气井相继出现了油套、技套环空异常带压现象,对气井的完整性和安全开采提出了严峻挑战。本文针对这类高温高压高含硫气井从异常带压诊断、完井管柱强度完整性、完井管柱密封性、固井水泥环密封性和井口装置完整性5个方面开展理论和室内试验以及现场应用研究,形成了一套高温高压高含硫气井完整性评价方法和异常带压气井防控对策,为防止新井出现环空异常带压、确保已有环空异常带压井安全生产提供了技术支撑。1、结合现场开展了完井管柱强度研究,形成了一套基于第四强度理论的不同工况条件封隔器完井管柱三轴应力强度完整性评价方法及流程,创新提出采用Goodman曲线进行完井管柱交变载荷量化控制评价分析,特殊复杂实例分析表明该方法实用、可靠。2、提出了异常环空压力气井放压/恢复特征曲线,建立了封隔器完井管柱条件生产过程井筒温度、环空压力理论预测、环空压力诊断测试定量分析计算模型,创新提出了封隔器完井管柱气井环空井喷速率及冲击载荷计算模型。3、通过完井管柱密封可靠性研究、复合载荷室内试验和有限元模拟,确定了完井管柱密封可靠性理论计算模型及参数取值,取得了随着生产时间的推移高含硫气井油管柱密封可靠性下降幅度最大(10年后降低50%)的认识,明确了VAM TOP等特殊螺纹具有较好气密封性能的力学机理,试验证实为确保密封完整,螺纹承受压力的改变次数越少越好。4、创新提出固井水泥环端面腐蚀评价方法,明确了水泥环在H2S和CO2条件下的腐蚀机理,取得了特殊腐蚀过渡层的新认识,创新提出在不同酸性环境下水泥石端面腐蚀速率计算公式。5、通过多相流采气井口装置冲蚀、内漏和承载能力数值模拟分析表明：采气井口装置本体力学承压能力相对气藏开发压力递减来说是安全的,应更多考虑井口装置的密封性能；油管悬挂上端、主通径与侧通径转弯附近和法兰连接下法兰处是最容易发生冲蚀伤害的部位,推荐采用相控阵探伤仪检测、应力集中检测和超声波探测分析法进行采气井口装置完整性在线评价。应用实践表明：本文研究形成的高温高压高含硫气井完整性评价方法和异常带压气井防控对策,为Lg气田防止新井出现环空异常带压、确保已有环空异常带压井安全生产提供了重要技术支撑,可在类似高温高压高含硫气田推广应用。更多还原

【Abstract】 Proved reserves of high sulfurous natural gas with H2S over30g/m3is nearly1trillion m3in China, generally with deep burial, high temperature, high pressure, complex geological conditions, mostly located in densely populated areas. Its resource utilization is faced with difficulties such as strong corrosion, high cost, big toxicity, serious accidents. Since2009, Lg gas field and Pg gas field have been put into production, and part of the gas wells have appeared under pressure phenomena in annulus between tubing and production casing or intermediate casing, posing severe challenges on gas well integrity and safe production.Aiming at this kind of high temperature, high pressure, high sulfur gas wells, the paper states theoretical research, laboratory test and field application research from abnormal under pressure diagnosis, well completion string strength integrity, well completion string tightness, cement ring tightness and wellhead integrity. Gas well integrity evaluation method, prevention and control measures for abnormal under pressure gas well have been developed for high temperature, high pressure, high sulfur gas well, providing technical support to prevent abnormal annulus under pressure in new wells and ensure safe production in existing abnormal under pressure well.1. Completion tubing string strength research has been carried out combining with the actual condition, forming a set of packer completion string triaxial stress intensity integrity evaluation methods and processes under different working condition based on the fourth strength theory. Quantitative control evaluation analysis of completion string under alternating loads is innovatively presented by applying Goodman curve. The example analysis shows that this method is practical and reliable.2. Pressure relief/recovery characteristic curve of gas well with abnormal annulus pressure is proposed. Wellbore temperature, annulus pressure prediction, annulus pressure calculation model for quantitative analysis of diagnostic tests in production process is established for packer completion string. Calculation model of annulus blowout rate and impact load for packer completion string is innovatively presented.3. Completion tubing string sealing reliability calculation model and parameter selection have been determined through completion string sealing reliability research, composite loads laboratory test and finite element simulation, revealing that high sulfur gas well tubing string sealing reliability has biggest drop (50%lower in10years) as production time goes on, clearing about mechanics mechanism of good sealing performance of special thread such as the VAM TOP. Tests prove that less times of pressure change on thread is better for sealing integrity.4. Cement ring end face corrosion evaluation method and cement end face corrosion rate formula under different acidic condition are innovatively put forward, clearing about corrosion mechanism of cement ring under H2S and CO2condition, making a new understanding of special corrosion transition layer.5. Multiphase flow numerical simulation analysis on wellhead erosion, internal leakage and bearing capacity shows:mechanical bearing capacity of wellhead body is safe comparing to pressure depletion in gas reservoir development and wellhead sealing performance should be more considered; upper tubing hanging, main sizes and side size, lower part of flange connection is the most prone to erosion damage parts and phased array detector test, stress concentration detection and ultrasonic detection analysis are recommended for wellhead integrity online evaluation.Application practice shows:the high temperature, high pressure, high sulfur gas well integrity evaluation method, prevention and control measures for abnormal under pressure gas well in this paper provide significant technical support to prevent abnormal annulus under pressure in new wells and ensure safe production in existing abnormal under pressure gas wells in Lg gas field and can be promoted and applied in similar high temperature, high pressure, high sulfur gas fields.更多还原