摘要
深水天然气水合物层钻井时,水合物颗粒随钻井液上返过程中会随压力降低、温度升高而不断分解,管流相态、特征参数变化明显,对井控要求高。在天然气水合物动态传质分解基础上考虑管流速度、温度及压力对其分解的影响,建立了深水天然气水合物井筒气、液、固复杂介质非平衡相态条件下的多相流动求解模型,并采用数值模拟方法对天然气水合物分解过程中在不同机械钻速、钻井液排量和钻头尺寸下多相流动敏感性影响因素进行了分析,结果表明:天然气水合物摩尔分解速率随着分解反应的进行而降低,随着相对流速的变大而增大,随着环境压力降低而变大,随着环境温度降低而变小,总摩尔分解速率随着破岩粒径的降低而变大;随着钻头尺寸、机械钻速增大,环空流速增加,环空压力降低;随着钻井液排量增大,井筒流速增加,井筒压力升高。上述结果可为深水天然气水合物层钻井井下安全控制提供参考。
When drilling in deep water natural gas hydrate reservoirs, the hydrate clathrate will gradually decompose with the decreasing pressure and increasing temperature along the upward flowing drilling fluid. Along the wellbore the conduit flow phase behavior and characteristic parameters will vary significantly, necessitating sophisticated technology for well control. On the basis of dynamic mass transfer decomposition of gas hydrate, multiphase flow models were established considering the influences on hydrate decomposition of conduit flow velocity, temperature and pressure under the condition of gas-liquid-solid complex media non-equilibrium phase transformation. Then numerical simulation method was used to analyze sensitivity influences of multiphase flow, which mainly include rate of penetration（ROP）, flow rate and bit size. The results show that the molar decomposition rate of individual hydrate particles will decrease with decomposition time, increase with increasing relative flow velocity, increase with decreasing pressure, decrease with decreasing temperature; the total molar decomposition rate will increase with decreasing diameter of particles. The annular flow velocity will increase and annular pressure will decrease with increasing bit size and ROP; and the wellbore flow velocity and wellbore pressure will both increase with increasing flow rate. The research findings can provide references for downhole safety control during drilling in deepwater natural gas hydrate reservoirs.
出处
《中国海上油气》
CAS
CSCD
北大核心
2016年第4期107-113,共7页
China Offshore Oil and Gas
基金
中国工程院
国家自然科学基金委重大战略咨询项目"深海天然气水合物绿色钻采战略及技术方向研究(编号:2013-ZCQ-12
L1322021)"
关键词
深水钻井
天然气水合物
多相流动
敏感性分析
deep water drilling
natural gas hydrate
multiphase flow
sensitivity analysis
