深水油气井导管全寿命周期承载力演化机理研究

Conductor is the “throat” of deepwater wells and its stability is recognized as primary technical problems worldwide. The shallow soil in deepwater area usually has complex layer, which leads to low and changeable bearing capacity. The conductor installation needs to overcome the technical problem that low bearing capacity and cementing quality trouble. At present, the conductor jetting technology has been successfully applied in deepwater wells. However, the design method mostly relies on engineering practice and is lack of theoretical foundation, which has resulted in some failures in field operation. So the relevant basic theory needs to be studied urgently. Based on China's deepwater geological characteristics, this project will carry the research through regional geology analysis, theoretical model study, simulation experiment and numerical modeling. The project aims to solve the problem that construction’s impact on the coefficient of friction between pile and deepwater layered soil. The soil bearing capacity evolution model will be established with complex load during jetting in. Under the drill pipe dynamic load, the project will also build the real time stability mechanism of conductor. Finally, the conductor’s whole life stability evolution model can be set up considering the production vibration load and temperature change. With this, theoretical basis and scientific guidance can be provided for deepwater drilling technology.

导管是深水油气井的“咽喉”，其下入时稳定性、生产时安全性是业界公认的首要难题。深水浅部地层普遍存在承载力低、承载力变化大等特点，导管下入过程需要克服承载力低、稳定性难控制等风险。目前，喷射下入导管技术已在国内外深水油气井进行了应用，但下入设计方法多是基于现场工程实践经验，缺乏针对性理论指导，造成失败工程案例时有发生，相关基础理论研究亟待攻关。本课题将针对我国深水油气区的工程地质特征，通过区域地质特征分析、理论模型研究、室内模拟实验和数值模拟验证，研究深水分层土体的施工扰动过程对桩—土间摩阻系数的影响及摩擦力演化机制；构建导管喷射下入过程复杂载荷条件下的分层土体承载力演化模型；研究钻进过程钻柱动态载荷作用下的导管实时稳定性机制；创建综合考虑油气生产过程中振动载荷及温度变化耦合作用下的全寿命周期导管承载力演化模型。为我国深水钻井技术体系提供理论依据和科学指导。

我国油气对外依存度已连续5年超过60%警戒线，并持续攀升至2020年的73%，国家能源安全形势严峻。南海油气资源丰富，约占我国油气总资源量的1/3，其中深水占比超过70%，深水油气已成为世界石油工业的主要增长点和科技创新的制高点。深水钻井导管的下入是深水油气井建设的基础，直接决定了建井过程的成败，其稳定性面临着全寿命周期内的复合动载荷影响。本课题针对深水浅部地层普遍存在承载力低、承载力变化大等特点，导管下入过程需要克服承载力低、稳定性难控制等风险，通过开展不同砂、泥比例土体的界面摩阻力对比性实验，揭示了摩阻力的变化规律，建立了导管—土接触界面的摩阻力系数模型，揭示了摩阻力随时间的演化规律。开展了钻井导管下入过程的承载力对比性模拟实验，揭示下入导管施工扰动条件下的实时承载了演化机理，建立了考虑管柱上下活动因素的导管实时摩阻力模型。通过数值仿真分析，创建了钻进工况下的导管实时承载力模型，并根据振动特征、振动历时等实验数据进行演化机制分析，揭示了二开后钻进过程的导管承载力的传递特性，建立了钻入法下入技术条件下的钻柱动态载荷对导管承载力的影响分析模型。通过深水油气生产载荷模拟实验，揭示深水油气井水下井口采油树、回接管汇系统等在生产过程中所产生的振动载荷对导管承载力的影响规律，并揭示了考虑因生产所致的温度场改变与生产动态载荷耦合作用下的导管稳定性机理，构建深水导管全寿命周期的导管承载力计算模型。本项目通过深水浅层钻井基础理论研究和模拟实验验证，取得了多项具有创新性和应用性的成果，为突破深水钻井中的技术瓶颈奠定了理论基础，推动了海洋深水钻井关键技术自主研发。