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由于气体钻水平井中岩屑受力状态与直井有很大不同,特别是遇到井径扩大,更是携岩的关键点。因此,在分析了气体钻水平井岩屑运移特点以及建立环空连续性方程和动能方程的基础上,以实际井为例考虑了不同井径扩大率,数值模拟了其扩径段气固两相的流动状态,包括气固速度、岩屑浓度、压力分布等。研究结果表明:气体在经历扩径段时环空压力有个降落又回升的过程,随着井眼扩径系数的增大,压力下降又回升,所经历的长度会逐渐增长;扩径系数大于一定值时,扩径变径处存在一定区域的零流动区;扩径系数越大,低速区和回流区就越大越长,扩径下部区域越容易堆积岩屑,填充井眼。
Since the stress state of cuttings in gas drilling horizontal wells is very different from that of vertical wells, especially in the case of expanding the borehole diameter, it is the key point for carrying rocks. Therefore, based on the analysis of the transport characteristics of cuttings in gas-drilling horizontal wells and the establishment of annular continuity equation and kinetic energy equation, taking the actual wells as an example, the expansion rates of different bore diameters are considered, and the gas-solid Two-phase flow conditions, including gas-solid velocity, cuttings concentration, pressure distribution. The results show that the annular pressure decreases and rises during the expansion of the gas. As the borehole expansion coefficient increases, the pressure drop increases and the length experienced increases gradually. The expansion coefficient is larger than A certain value, there is a certain region of the zero-flow zone at the diameter-expanding and diameter-reducing points. The larger the diameter-expansion coefficient is, the longer the low-velocity zone and the recirculation zone are, and the more the lower-diameter zone is likely to accumulate cuttings and fill the borehole.