非均匀套管磨损对套管强度的影响

在深井、大位移井钻井过程中，由于钻杆与套管长时间的接触会造成上层套管受到不均匀磨损，导致套管抗挤强度和抗内压强度降低，给安全钻井带来隐患。根据ISO 10400推荐的套管抗挤强度和抗内压强度计算模型，考虑磨损后套管壁厚不均度、内壁不圆度的影响，推导出了非均匀磨损套管抗挤强度和抗内压强度的计算模型，分析了套管磨损厚度对套管抗挤强度和抗内压强度的影响。计算结果表明，非均匀磨损套管的抗挤强度和抗内压强度降低百分比随套管磨损厚度的增加而增加；在相同的磨损厚度情况下，磨损后套管的抗挤强度比抗内压强度降低得更快；与磨损后CS 110T套管抗挤强度试验数据相比较，由理论计算出的非均匀套管磨损抗挤强度与实测值的相对误差在5%以内。该计算模型为深井、大位移井钻井过程中非均匀套管磨损提供了新的评价方法。

The effects of non-uniform casing wear on casing strength

During the drilling in deep wells and extended reach wells, non uniform casing wear occurs due to the frequent contact between the drill pipe and the casing. While severe casing wear will lead to the reduction of casing collapse strength and internal pressure strength, this becomes a threat to drilling safety. Based on the recommended calculation formulae for casing collapse strength and internal pressure strength by the ISO 10400, the calculation models of casing collapse strength and internal pressure strength for non uniform wear casing were derived, with the effects of casing eccentricity and ovality considered. Then the collapse strength and internal pressure strength of casing with different wear thicknesses were calculated. The results showed that the casing collapse strength and internal pressure strength will decrease as the casing wear thickness increases. Under the same wear condition, the casing collapse strength decreases more rapidly than the internal pressure strength. From the comparison between the theoretical calculation result and the measured collapse strength of CS 110T worn casing, it is concluded that the relative error of this method is within 5%. This model will provide a new evaluation method for non uniform casing wear in deep wells and extended reach wells.