气体钻井环空气固两相流动数值模拟研究

【作者】 郭建华；

【导师】 李黔；

【作者基本信息】 西南石油大学 ， 油气井工程， 2006， 硕士

【摘要】 气体钻井对于防止井下复杂有明显效果，能较大幅度提高机械钻速，节省钻头，提高采收率，有利于环保，近年来，在国内外应用得越来越广泛。国内气体钻井技术迅速发展，取得了一定的阶段性成果，但是就技术的先进性、成熟性、配套性来讲，与国际先进水平和大面积的成熟应用相比仍有较大差距，尤其在气体钻井的工作特性和工艺参数研究方面还不成熟。 为了提高气体钻井理论模型的计算精度和水平，本文试图利用现代计算流体动力学(CFD)方法对气体钻井环空气固两相流动规律进行数值模拟研究，探索出一套基于CFD的气体钻井全井全尺寸水力学设计分析方法，力图采用该方法后能直观形象地观察到全井任意位置处的流体流动特征。 本文建立了气体钻井环空气固两相流动三维瞬态力学模型，并采用实验数据对模型进行了验证，结果表明采用该模型计算的结果与实验结果吻合较好。采用该模型对气体钻井环空气固两相流动规律进行了数值模拟研究，研究表明： 1．在垂直、倾斜、水平和弯曲井段环空内：压降随气体速度增加先减后增，同心环空压降大于偏心环空；平均岩屑浓度随岩屑直径增加呈对数关系增加；钻柱和井壁受到的剪切应力随速度增加呈幂指数增加，钻柱冲蚀更明显。 2．开泵过程中，沉积在井底的岩屑一般经历沟流、节涌、崩裂、聚团流动四个阶段；开泵瞬间压降较大，随时间延长压降减小，到达最低值后又开始增大。 3．对地层出水后(＜5m~3／h)环空气液固三相流动规律进行了数值模拟分析，从理论上揭示了钻柱腐蚀的原因，即地层水主要分布在钻柱外壁和井壁上。 4．在变截面环空井段过渡截面处，压力分布有突变。 本文基于建立的环空气固两相流动三维瞬态力学模型及CFD理论，对气体钻井全井全尺寸水力学设计分析方法进行了新的探索性研究，研究表明： 1．采用该方法可定量计算分析环空气固两相流动对钻柱和井壁的剪切作用力。 2．该方法结合APIRP14E标准可对钻柱和井壁的冲蚀临界速度进行计算，计算研究表明可通过加载回压控制其冲蚀作用。 3．采用该方法可确定加载的合理回压值，即合理的回压值应确保环空内流速介于最小携岩速度和冲蚀临界速度之间。 本文探索的基于CFD的气体钻井全井全尺寸水力学设计分析方法在川东北M1井得到应用，现场应用结果表明，采用该方法设计的注入参数与现场实际施工数据吻合较好。更多还原

【Abstract】 The gas drilling has the obvious effect for avoiding complexities in the well bore. It can increase drilling rate clearly, decrease the quantities of the bits, improve the recovery ratio, and be benefit for the environmental protection. In the recently years, it is used widely at home and abroad. At present, gas drilling technology is developed rapidly. The researches and applications on this item have acquired lots of fruits at home. But it is far away from the international advanced level and application on a large scale district. The researches on working characteristics and technology parameters are still not mature in gas drilling.In order to improve the computation precision and level of the theory model in gas drilling, in this paper I try to use the computation fluid dynamics method to do, and explore a set of full-well full-scale hydraulics plan and analysis method based on the CFD, by which we can visualize the flow properties in the arbitrary position.By using the CFD theory, the 3D transient dynamic mode of gas-cuttings flow in the annular space in the gas drilling has been built, which is checked by the experiment data. The comparison indicates that the results computed by the mode are better fitful with the experiment data. The gas-cuttings flow in the annular space is been simulated by the mode in this paper, the results indicate that:1. The pressure decreases firstly then increasing by the gas velocity increasing. And the pressure in the concentric annular space is larger than the eccentric one. The average cutting fraction increases by the cutting diameter increasing in logarithm law. The sheer pressure of the part element increases by the velocity increasing in exponent sign, and the erosion of drilling pipes is more obvious.2. The cuttings will pass 4 phases which including channeling, slugging, bursting apart, getting together. The pressure drop is larger at the initial of pumping on, and decreases by time, increase by time after it reaching the minimum value.3. The gas-cuttings-water 3 phase flow has also been researched by the numerical simulation. The results open out the corruption cause of the drilling tools, namely, the formation water mainly distribute on the outer wall of drill tools and wall of the well.4. The pressure will become discontinuity at the transition section in the annular space.Based on the 3D transient dynamic mode of gas-cuttings flow in the annular space and the theory of CFD, the research of full-well full-scale hydraulics plan and analysis method has been explored, the results indicate that:1. The sheer pressure of the part element can be computed quantitatively by this method.2. The critical erosion velocity of the part element can be computed in this method with the criterion of API RP 14E. The results indicate that we can control the erosion by back pressure.3. The proper back pressure can be confirmed in this method, namely the proper back pressure should make sure the velocity in the annular space is between the minimum well更多还原