海洋天然气水合物藏钻探环空相态特性

发布时间：2018-01-07 06:36

本文关键词：海洋天然气水合物藏钻探环空相态特性　出处：《石油学报》2017年06期 　论文类型：期刊论文

【摘要】：海洋天然气水合物藏钻探过程中,水合物钻屑随钻井液向上返出,随着温度升高、压力降低,水合物钻屑上升至一定位置开始分解,使井筒流动变为环空复杂气液固多相流,这对井下流动安全产生严重威胁。考虑井筒温度、压力与水合物分解的耦合作用与影响,建立了海洋天然气水合物钻井过程中井筒温度模型、井筒压力模型、水合物动态传质分解模型和复杂环空多相流模型。通过模型求解,数值分析了井筒温度、环空压力和水合物分解在不同钻井工况下的变化规律。结果表明:增大钻井液排量,井筒中井底处循环钻井液温度升高,环空中井口处返出钻井液温度降低,分解起始位置下移;增大钻井液密度,环空压力升高,分解起始位置上移;增大钻井液入口温度,井筒温度升高,分解起始位置下移;增大机械钻速,分解起始位置不变。
[Abstract]:During the drilling process of marine natural gas hydrate reservoir, the gas hydrate cuttings come back up with the drilling fluid, and with the increase of temperature, the pressure decreases, and the gas hydrate cuttings rise to a certain position and begin to decompose. The wellbore flow becomes a complicated gas-liquid-solid multiphase flow in annulus, which poses a serious threat to the downhole flow safety. The coupling action and influence of wellbore temperature, pressure and hydrate decomposition are considered. The wellbore temperature model, wellbore pressure model, gas hydrate dynamic mass transfer decomposition model and complex annulus multiphase flow model are established during offshore gas hydrate drilling. The wellbore temperature is numerically analyzed by solving the model. The variation of annular pressure and hydrate decomposition under different drilling conditions. The results show that the drilling fluid temperature increases at the bottom of wellbore and decreases at the wellhead of annulus by increasing the discharge of drilling fluid. The starting position of decomposition is moved down; With the increase of drilling fluid density, the annulus pressure increases and the starting position of decomposition moves up. With the increase of the inlet temperature of drilling fluid, the wellbore temperature increases and the starting position of decomposition moves down; Increase the drilling speed of the machine and keep the starting position of decomposition unchanged.
【作者单位】：西南石油大学油气藏地质及开发工程国家重点实验室;中国海洋石油总公司;中海油研究总院;
【基金】：国家重点研发计划(2016YFC0304008) 国家自然科学基金(No.51334003) 油气藏地质及开发工程国家重点实验室开放基金重点项目(PLN1309、PLN1418)资助
【分类号】：TE28
【正文快照】： 全球天然气水合物总资源量大约为(1.8~2.1)×(dnh-pdteq)-fa(Ta,pa)]h　)=kdAh[feq(Ta,1016　m3,碳含量相当于全球已探明化石能源含碳总量T,aPa的2倍[1]。天然气水合物主要分布在陆地永久冻土带(1)和陆缘外围的海底沉积物中[2],其中海洋天然气水合1.1.1　钻屑颗粒中水合物的分

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