涡流式水力降低井底压差机制及现状

 石油与天然气钻探实践表明,降低井底压差,减小岩屑的压持效应,并尽量实现井底的欠平衡条件,可以显著提高钻井的机械钻速。本文在介绍涡流式水力降压技术的原理的基础上,综述了环空涡流泵、涡流式水力降压短节和涡流钻头等涡流式水力降压工具的结构特点、降压效果和研发应用情况,采用计算流体力学软件对涡流PDC(聚晶金刚石复合片)钻头的井底流场进行了数值模拟研究。结果发现,涡流钻头与井壁间的密封是降压的关键,推荐上返喷嘴的倾角为150°—180°,推荐上返流量为32%以上,为涡流钻头的研发提供理论指导。

Depressurization Mechanism of the Vortex Methods and Its Current Development status

The drilling practices of oil and gas wells have proved that reducing the Bottom-Hole Differential Pressure (BHDP) is able to significantly improve the Rate of Penetration (ROP), reducing the drilling cost. The structure features, depressurization capacities, and the current researches and developments of Equivalent Circulation Density (ECD) reduction tool, vortex joint, and vortex bit are summarized based on the analysis of the depressurization theory of the vortex tools. The numerical simulation analysis is carried out to study the bottom hole flow field of the vortex Polycrystalline Diamond Compact (PDC) bit using the CFD software, the results show that the critical factor affecting the vortex bit depressurization capacity is the reliable sealing of the annulus between the vortex bit and the borehole walls. 150°-180° is recommended for the angle of the reverse nozzle, and more than 32% of the total circulation drilling fluid is also recommended as the upflow, providing the theoretical guide for the development of the vortex bit.