抑制水合物冻堵的天然气开井动态模拟研究

针对天然气井工艺管道在开井过程中极易产生水合物冻堵的问题，采用Dynsim 软件建立了开井工况动态模拟模型，讨论了开井流量、工艺管道敷设方式与保温层厚度、节流调节方案对节流后温度压力的影响，分析了开井过程中外界热交换的动态变化特征及对开井过程的影响，提出了加热炉前工艺管道优化设计与开井过程水合物优化控制方案。结果表明：开井流量对水合物生成风险具有重要影响，开井流量越小，水合物生成风险越大，但不管开井流量如何调整，井口工艺管道内均存在水合物生成风险；在保证下游出口超压在可接受范围的前提下，应通过同时调节各级节流阀或主要调节二级与三级节流阀来尽量增大开井流量，并配合注醇、加热等方式来避免在工艺管道中生成水合物；井口至加热炉前的工艺管道宜采用埋地敷设方式，埋地敷设管道无需保温，而架空敷设管道宜加保温措施。

Dynamic Simulation of the Open Process for Natural Gas Wells to#br#Inhibit Hydrate Freeze-plugging

The hydrate freeze-plugging phenomenon is easy to occur in pipelines during the open period of natural gas wellsespecially for wells with high pressure. The dynamic characteristics and optimal hydrate control schemes during well openingperiod，however，have not been studied systematically. So the specific dynamic models have been established to analyzethe dynamic characteristics during well opening period by Dynsim package. The influences of the fluid flowrate，installationmodes of pipelines，thickness of thermal insulation layer as well as throttling regulation schemes on throttling temperature andpressure during well opening period have been discussed by using the dynamic models. The dynamic characteristics of heattransfer between fluid in pipelines and ambient environment during well opening period have also been analyzed. In addition，the optimal control schemes for hydrate inhibition during well opening period and optimization design for pipelines have alsobeen put forward in the paper. The results demonstrate that the fluid flowrate during well opening period has dramatical influenceon the risk of hydrate formation in pipelines. And no matter how to regulate the fluid flowrate during well opening period，hydrate formation risk in pipelines exists all the time，especially when the flowrate remains small. In order to avoid hydrateformation in pipelines，the fluid flowrate during well opening period should be increased as large as possible by regulatingdifferent throttle valves simultaneously or regulating the secondary and tertiary throttle valves mainly. Meanwhile，necessarymeasures like alcohol injection or heating should be done to mitigate the risk of hydrate formation. Furthermore，it is suggestedthat the pipelines between wellhead and heating furnace should be buried underground without thermal insulation layer，whereasother overhead pipelines should be covered by thermal insulation layer.