Temperature Changes in Oil Wells and Its Effect on Tubulars Stress Condition

Research subject: Prediction of the wellbore temperature during the downhole operations and its effects on the stress condition of the tubulars is one of the important factors in design of the completion, production and stimulation operations in oil and gas wells. Temperature changes during the life of the well can change the stress condition of the pipes inside the well, such as the tubing and the casing, and cause problems such as wellhead displacement or buckling of the tubulars, which is dangerous in both terms of safety of the well and personnel and it can also be economically inefficient. Research approach: In this study, various operations during the life of a well such as running the completion string, production start-up, the well shut in, acid injection and other common operations in oil wells were simulated in a practical order. Temperature changes during these operations and their effect on the stress condition of the wellbore casing and tubing were investigated. Main results The results showed that long-term production of the well causes the most temperature changes in the well. This increase in the temperature reached a maximum value at a depth of 430 ft, which is the mud line depth.  Further, because the pipe is fixed, it buckles and creates torque at deeper well depths. The results also showed that the time required for the temperature to be completely stable is about a few months, and this should be taken into account in the tubing pressure test analysis.