钻具稳定器结构对复合钻井导向力的影响

The effect of configuration of drilling stabilizer on the steering force during combined drilling

单弯螺杆钻具+PDC钻头复合钻井已广泛在钻井提速和井眼轨迹控制作业中应用,对该类钻具组合导向力分析也有成熟的方法,但常常忽略螺杆稳定器结构的影响。为此,基于油气田现场作业应用的直棱和螺旋棱稳定器结构,讨论了螺杆稳定器外径和支点位置变化对钻具导向力的影响,建立了稳定器实际偏心距计算模型,提出了考虑螺杆稳定器结构影响的钻具复合钻井导向力分析方法。通过对单弯螺杆单稳定器钻具组合、单弯螺杆双稳定器钻具组合复合钻井导向力的分析,结果发现:①忽略螺杆稳定器结构的复合钻井导向力分析方法计算结果与钻具导向合力差别较大;②直棱稳定器由于棱槽包角的存在,等效外径周期性变化使得钻具组合导向力发生周期性增加或降低,变化幅度最高达50%,影响钻具导向稳定性能和疲劳寿命。进而提出建议:①计算复合钻井导向力时应采用考虑螺杆稳定器结构影响的钻具复合钻井导向力分析方法;②现场复合钻井时选用带棱槽包角为零的螺旋式稳定器或选用带棱槽包角小的直棱稳定器的螺杆钻具。

Combined drilling technology with single-bend screw drill and PDC bit is widely used to increase penetration rate and con- trol well course. There are methods available for its steering force analysis, but the effect of configuration of screw stabilizers are u- sually negleeted. Therefore, this paper investigates the configurations of straight blade and screw blade stabilizers that are adopted in oil and gas fields, and discusses the effect of external diameter and supporting point position of screw stabilizers on the steering force of drilling tools. A calculation model was established for real offsetting of stabilizers, and an analysis method considering the effect of configurations of screw stabilizers was put forward for the steering force during combined drilling. Steering force analysis was con- ducted for single bend screw-single stabilizer assembly and single bend screw-double stabilizer assembly. It is shown that there is greater difference between resultant steering force and the calculation result when the configuration of screw stabilizers is ignored. There is a blade slot wrapping angle in straight blade stabilizers, so the BHA steering force rises or drops periodically with the high- est extent of variation up to 50~ due to the periodic variation of equivalent external diameter. Consequently, stability and fatigue li- fetime of BHA guides are spoiled. Therefore, two suggestions are proposed. Firstly, the effect of configuration of screw stabilizers should be taken into consideration when steering force of combined drilling is calculated. Secondly, in combined drilling it is neeessa- ry to adopt screw drills whieh have screw stabilizers with blade slot wrapping angle of zero or straight blade stabilizers with small blade slot wrapping angle.