王瑞和, 倪红坚, 宋维强, 肖彩云. 超临界二氧化碳钻井基础研究进展[J]. 石油钻探技术, 2018, 46(2): 1-9. DOI: 10.11911/syztjs.2018040
引用本文: 王瑞和, 倪红坚, 宋维强, 肖彩云. 超临界二氧化碳钻井基础研究进展[J]. 石油钻探技术, 2018, 46(2): 1-9. DOI: 10.11911/syztjs.2018040
WANG Ruihe, NI Hongjian, SONG Weiqiang, XIAO Caiyun. The Development of Fundamental Research on Supercritical Carbon Dioxide Drilling[J]. Petroleum Drilling Techniques, 2018, 46(2): 1-9. DOI: 10.11911/syztjs.2018040
Citation: WANG Ruihe, NI Hongjian, SONG Weiqiang, XIAO Caiyun. The Development of Fundamental Research on Supercritical Carbon Dioxide Drilling[J]. Petroleum Drilling Techniques, 2018, 46(2): 1-9. DOI: 10.11911/syztjs.2018040

超临界二氧化碳钻井基础研究进展

The Development of Fundamental Research on Supercritical Carbon Dioxide Drilling

  • 摘要: 超临界CO2钻井技术是以CO2为钻井介质的新型钻井技术,在实现CO2资源化利用和提高非常规油气钻探效益等方面潜力巨大,其关键理论和技术问题主要体现在超临界CO2在井筒中的流动规律、携岩能力、射流破岩及井壁稳定性等井筒多相流和流体与岩石相互作用方面。为此,利用超临界CO2在井筒中的流动模型分析了影响超临界CO2钻井环空压力分布的因素;通过理论计算和室内携岩试验分析了超临界CO2的携岩能力;根据理论分析和室内射流破岩试验分析了超临界CO2射流破岩机理;利用临界CO2与井壁围岩的力-热耦合模型并结合超临界CO2对岩石力学性质的影响,分析了超临界CO2钻井的井壁稳定性。结果表明:循环流量和井口回压是影响超临界CO2钻井环空压力分布的主要因素;井斜角为48°~72°时超临界CO2携岩最小返速比较高,超临界CO2的携岩效果与清水接近,但远优于空气;超临界CO2射流破岩产生的温度应力可有效降低破岩门限压力,提高破岩效率;采用超临界CO2钻进水平层理硬质页岩地层时井壁稳定性好。研究结果为完善超临界CO2钻井理论和尽快形成超临界CO2钻井技术奠定了理论基础。

     

    Abstract: Supercritical CO2 drilling,a new type of drilling technique uses CO2 as its sole drilling fluid and has great potential in accomplishing the resource utilization of CO2 and improving the efficiency of drilling unconventional oil/gas wells.The key theoretical and technical challenges in supercritical CO2 drilling mainly involve supercritical CO2 flow law in the borehole,the cuttings carrying capacity,rock jet-breaking and wellbore stability in multiphase flow and fluid-rock interactions.In this paper,the supercritical CO2 wellbore flow model was used to analyze the factors affecting the distribution of supercritical CO2 drilling annulus pressure;theoretical calculation and cuttings carrying experiments were conducted to analyze the cuttings carrying ability of supercritical CO2. According to theoretical analysis and rock jet breaking tests,the mechanism of supercritical CO2 jet breaking was analyzed.Wellbore stability in critical CO2 drilling was analyzed through mechanical and thermal coupling model of critical CO2 and surrounding rock in combination with the effect of supercritical CO2 on rock mechanical properties.The results show that circulation flow rate and wellhead back pressure were the main factors in the distribution of supercritical CO2 drilling annulus pressure.When the well inclination was 48°-72°,the minimum return velocity of supercritical CO2 cuttings carrying was relatively high and the cuttings carrying efficiency was closed to that of fresh water which was remarkably higher than that of air;the reduced stress from temperature change when rock broke down from supercritical CO2 jetting could effectively reduce the threshold pressure of the rock breaking down and improve the efficiency of rock breaking.When drilling through horizontal beddings of hard shale strata with supercritical CO2,a perfect wellbore stability was observed.The research established a foundation for the perfection of supercritical CO2 drilling theory and the establishment of supercritical CO2 drilling techniques.

     

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