深层高温高压油气井安全高效钻完井基础研究

The exploration and development of oil and gas in deep formation has become a significant demand for China. However, due to complex conditions of high temperature, high pressure and high in-situ stress, the study of basic theories for safe and efficient deep-drilling remains a challenging, which resulting low speed of penetration, poor completion quality and high risk of operation safety. This project will investigate the rock-breaking mechanism and drillability estimation methods under high confining pressure of deep well, by coupling the mechanical loadings, jet impact and bottom hole differential stress. Then the novel rock-breaking method will be achieved by the combination of new type of high pressure jet and mechanical drilling techniques. Secondly, a multiphase transient flow model will be established when coupled the flow between wellhead-wellbore-formation. The multiphase flow mechanisms of deep wellbore flow and characteristics of the pressure wave propagation will be studied. An automatic control method for wellbore pressure during the deep well drilling will be developed. Thirdly, a model of load on casing string under high pressure and high temperature conditions will be established, so as to reveal mechanism of casing failure and form safety design method of casing in life cycle. Fourthly, the mechanism of fracture initiation and propagation of rocks under high pressure and high temperature conditions will be revealed, and then the innovative methods of the Hydra-jet stepless staged fracturing treatment and the integrated technique of Jet radial drilling and hydraulic fracturing will be discussed. The project will primarily deal with the critical and basic problems related to efficient and safe deep well drilling and completion in high temperature and high pressure formations, and provide the scientific guidelines and basis for well drilling and completion in deep hydrocarbon formation.

深层油气勘探开发是国家油气发展的重大需求，但深部地层多处于高温高压等复杂环境，深井钻完井的破岩机理、压力控制、井筒完整性和增产改造等基础理论缺乏，导致钻井速度慢、完井质量差、安全风险高等问题突出。针对上述问题拟开展以下研究：综合考虑机械载荷、射流参数和井底压差，研究深井井底岩石破碎机理和可钻性，探索新型射流水力-机械联合破岩提速新方法；建立井口-井筒-地层耦合的多相流瞬态流动模型，研究深井高温高压下井筒多相流动规律和压力波传递特性，为形成深井钻井井筒压力的闭环控制方法提供依据；建立深井高温高压环境下套管柱载荷计算模型，揭示深井温压条件下的套损机理，形成深井高温高压油气井套管柱全生命周期的安全设计方法；揭示深井高温高围压下地层起裂机理，探索深部致密储层水力喷射无限级压裂及钻完井一体化新方法。项目通过上述关键基础问题的研究并取得原创性突破，将为我国深层油气安全高效钻完井提供关键理论基础和科学依据。

深层油气勘探开发是国家能源战略的重大需求，但深井钻完井面临高温高压、机械钻速低、完井质量控制难、安全风险高等突出难题，为此，本项目围绕深井破岩成井机理、井筒压力控制、管柱安全设计和完井增产改造等基础问题开展系统研究，形成主要成果：1）模拟深井高温高压环境，研制了新型射流破岩实验系统，揭示了高温高压条件下钻头齿与射流破岩机制，即岩石压碎-崩落是钻头齿破岩的主要形式，而射流产生的热应力可辅助破岩；探索形成了超临界CO2射流、液氮射流、热力射流等新型射流破岩方法，为实现高效破岩提供了理论基础和方法原理。2）研制并开展了全尺寸井筒/环空气液固三相流动模拟实验，建立了非等温环空气-液-固三相瞬态流动模型，揭示了深井钻井不同工况下井筒压力和温度的动态变化规律，为深井高温高压环境下井筒压力闭环控制提供了科学依据。3）构建了一套完井、试油、采油全寿命周期的套管安全设计方法，制定形成了中石油企业技术规范，可提高套管安全等级，有效解决了深层高温高压油气井套管损坏难题。4）设计并开展了高温高压下致密储层压裂物模实验，揭示了温度对储层破裂的影响机制，发现压裂液与储层温度差引起的热应力可促进裂缝剪切破裂；低温液氮和超临界CO2等新型压裂流体可有效降低破裂压力；建立了适合于深部致密储层改造的水力喷射无限级压裂及钻完井一体化方法与设计，为深层致密油气高效完井改造提供了理论依据与原理方法。研究成果在《SPE Journal》、《AIChE Journal》、《International Journal of Heat and Mass Transfer》、《石油学报》等行业主流期刊发表论文49篇（SCI收录25篇，TOP期刊8篇），授权国家发明专利7件、实用新型专利1件，申请国家发明专利2件，授权软件著作权5件。部分成果入编英文专著，获国家技术发明二等奖。