深水气井测试管柱内天然气水合物堵塞特征与防治新方法  

Features and prevention of gas hydrate blockage in test strings of deep-water gas wells

作　　者：王志远[1] 赵阳 孙宝江[1] 于璟 

机构地区：[1]中国石油大学(华东)石油工程学院

出　　处：《天然气工业》2018年第1期81-88,共8页Natural Gas Industry

基　　金：国家重点基础研究发展计划(973计划)项目"海洋深水油气安全高效钻完井基础研究"(编号:2015CB251204);国家优秀青年科学基金项目"油气井多相流动理论及应用"(编号:51622405)

摘　　要：目前对于深水气井测试过程中井筒管柱内天然气水合物(以下简称水合物)堵塞的形成机制尚不清楚,因而存在着过度使用水合物抑制剂以及抑制剂利用效率较低等问题。为此,针对多相流,在水合物生成动力学、水合物颗粒运移沉积动力学等方面开展了研究:构建形成水合物堵塞的定量预测模型,预测水合物在管柱内何时何处形成堵塞并评估堵塞严重程度,确定易发生堵塞的高风险区。进而提出了基于拓展安全作业时间窗口的水合物堵塞防治新方法——依据安全作业时间窗口优选抑制剂浓度、优化抑制剂注入速率。研究结果表明:(1)井筒内所生成的水合物在管柱内壁上沉积附着,形成不断增厚的水合物层,造成管径变小,液膜处生成的水合物在管壁上沉积是造成管柱堵塞的主要原因;(2)随着水深增大或产气量降低,不发生水合物堵塞的安全作业时间窗口变窄,形成堵塞所需时间变短;(3)注入水合物抑制剂可以延缓堵塞的发生,拓宽安全作业时间窗口;(4)水合物防治新方法可显著降低所需水合物抑制剂用量和注入速率(在算例条件下可降低50%)。结论认为,新方法有效克服了传统方法过度使用水合物抑制剂的不足,可为深水气井测试中水合物的防治提供指导。Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells, inhibitors are either excessively consumed or inefficiently used when conventional prevention techniques are used. In this paper, a study was conducted on multi-phase flows, in terms of hydrate formation kinetics and hydrate particle migration and settlement kinetics. In this process, a model for quantitative prediction of hydrate blockage was built to predict when and where the blockage occurs in the strings and evaluate the severity of such blockage, in order to define the high-risk zones. Eventually, an innovative hydrate blockage prevention technique based on hydrate blockage free window （HBFW） was proposed to determine the optimal concentration and the flow rate of inhibitors. The study results are in the following four aspects. First, gas hydrates generated in the wellbore may deposit on the internal walls of strings. With the increase in thicknesses of such gas hydrate layers, the diameter of a pipe string decreases. Accumulation of gas hydrates generated around liquid film on pipe walls is the key contributor to the blockage in strings. Second, as the water depth increases or the gas production reduces, the HBFW turns to be narrower for production safety, and the time to initiate blockage is shorter. Third, application of hydrate inhibitors can effectively delay the occurrence of blockage and expand the window of safe production. Fourth, the innovative prevention technique can effectively reduce the volume and the flow rate of inhibitors （by 50% in the case study）. The innovative technique effectively eliminates the problems related to the excessive consumption of inhibitors in the conventional methods and provides a valuable reference for the prevention of gas hydrates formation in deep-water gas well tests.

关 键 词：深水 气井测试 天然气水合物 堵塞 防治方法 安全作业时间窗口 环雾流 抑制剂用量 注入速率 

分 类 号：TE37[石油与天然气工程—油气田开发工程]