Study on Safety Evaluation of Casing Wear Residual Strength in Well SK1
During drilling in deep and ultra-deep wells,the wearing of technical casing can not be ignored due to factors such as hole dogleg,ROP,and rotary speed.In serious cases,it will lead to a significant reduction of its collapse strength and burst strength,which will cause great hid-den danger to the wellbore integrity.Based on the in-depth analysis of the cause of ø244.5 mm technical casing wear in the SK1 well,the prediction method of casing wear was established by using the theoretical model of"wear-efficiency".It was pointed out that severe casing wearing u-sually occurred in the depth with big hole dogleg,and the casing wearing increased significantly with the increase of rotary speed and the decrease of ROP.By simplifying the worn casing into the defective casing with out-of-round inner wall and uneven wall thickness and"rectangular groove"casing,the calculation method of the residual collapse strength,the residual burst strength and their safety factors of the whole well section were established.The analysis results showed that when the rotary speed was higher than 100 r/min and the ROP was lower than 0.87 m/h,the minimum collapse strength safety factor of the ø244.5 mm casing in SK1 well would be lower than 1.0,and the reasonable drilling speed-up and anti-abrasion measures should be taken to ensure the strength safety of the technical casing.The research results had important guiding for the safety design of technical casings in deep and ultra-deep wells in the future.
NETL
NSTL
万方数据
维普
