水下油气临界分流取样计量理论及实现方法

Extracting and separating multiphase metering method has the advantages of small space, low cost and can be used widely in deepwater oil and gas field. Unfortunately, the measurement accuracy can’t be further improved because the sample fluid fails to represent the main fluid due to phase separation of gas-liquid two-phase flow. A special multi-nozzle sampler is designed and a flow pattern adjustment coupled with critical distribution method is proposed to eliminate mal-distribution. A novel tube bundle is also developed for sample fluid separation and measurement. In order to ensure the sample fluid and the main fluid have identical quality, upstream flow patterns are transformed into annular flow with uniform film thickness to make sure all the nozzles have same inlet condition. Several critical nozzles are mounted at the pipe wall to accelerate the gas-liquid mixture to achieve critical flow and block the propagation of pressure wave from downstream. Experiments will be carried out in an air-water two-phase flow loop to study the phase separation influencing factors and mechanism. The gas-liquid separation phenomena of gas-liquid two-phase flow in the tube bundle will be investigated and the synergistic effect of phase separation at junction, gravity and sieve tube will be studied. A multiphase numerical model is developed to study the gas-liquid distribution characteristic in the sampler and tube bundle. The flow insurance methods will be proposed to avoid hydrate, shock wave and whistling noise in the distributing nozzle. The research conducted in the project will reveal the gas-liquid two-phase critical distribution mechanisms. The outcome will be helpful to enrich and perfect the multiphase parameters measurement theory and can be used to develop novel subsea multiphase flow meter for deepwater oil and gas filed.

基于取样原理的多相流计量装置具有体积小、造价低的优点，在深水油气田开发中潜力巨大，但由于气液相分离的发生，取样缺乏代表性已成为制约测量精度进一步提升的瓶颈。项目以气液两相临界流动中的“壅塞”现象为灵感，提出了基于“流型调整+临界分流”的相分离控制方法以及适用于深水高静压环境的组合管束取样流体分离计量模式，切断下游压力扰动向上游传播途径，实现了气液等比例取样。项目将研究多喷嘴取样器气液临界分流特性，分析取样相分离敏感因素及作用机制；研究气液两相流组合管束分离规律，阐明三通相分离、重力沉降以及多孔筛管强化气液分离协同作用机理；建立气液两相流数值模型，预测发生临界分流条件，优化计量装置结构；研究分流喷嘴水合物生成风险，分流喷嘴内激波发生和演化规律以及流动啸声来源与控制机理。研究将形成临界取样气液两相流计量新理论，为自主研发用于深水油气开发的新一代水下多相计量装置提供科学支撑。

基于取样原理的多相流计量装置具有体积小、造价低的优点，在深水油气田开发中潜力巨大，但由于气液相分离的发生，取样缺乏代表性已成为制约测量精度进一步提升的瓶颈。项目以气液两相临界流动中的“壅塞”现象为灵感，提出了基于“流型调整+临界分流”的相分离控制方法以及适用于深水高静压环境的组合管束取样流体分离计量模式，切断下游压力扰动向上游传播途径，实现了气液等比例取样。.在国家自然科学基金资助下，开展了气液两相流取样敏感性实验研究，通过气液相分流系数表征相分离特征，研究发现取样规律受主管路流型、气液流速、取样孔位置等影响显著，分配特性主要受取样孔和气液界面相对位置控制；研究了气液两相流组合管束分离规律，自主研发了管束体气液两相分离器，在实验范围内实现了气、液混合物100%完全分离；建立气液两相流数值模型，优化旋流叶片结构和最佳取样截面位置，研究表明螺旋叶片整流效果最好，叶片下游45mm处环状液膜分布最均匀；研究提出了临界取样气液两相流计量新理论，研发了“18分流通道-3取样通道”取样器，以及“20分流通道-变取样通道（1,2,4,8）”两类计量装置样机，并在气液两相流环道上开展了试验测试。实验气相折算速度范围：2.3m/s-19m/s，气相折算速度范围：0.018m/s-0.185m/s，出现的流型包括分层流、波浪流、段塞流和环状流。实验测试表明，计量精度不受气液两相流流型、取样孔尺寸以及气液相流速波动的影响，气液相分流系数能在宽广的气液流量范围内保持恒定，油气计量误差≤5%。.项目研究所提出的临界分流取样计量方法，融合了传统分离和非分离方法的优点，体积小、结构紧凑，取样比只取决于取样通道占总分流通道的比值，无需标定，可根据需要随意调节，在深水油气田开发中应用前景广阔。.项目研究发表SCI论文8篇，中文论文5篇，授权发明专利6项，申请发明专利1项，培养硕士生5名，获教育部科技进步二等奖等科技奖励3项。