Thermal effect on wellbore stability during drilling operation with long horizontal section

In this study, a three-dimensional wellbore stability model is presented that takes into account thermal stresses combined with an integrated circulation temperature model for horizontal well drilling, the bottom hole temperature simulation were then validated using field measurements, and compared with results for vertical wells. A subsequent analysis of temperature sensitivity revealed that the heat source term, the length of horizontal section and mud specific heat were the main reasons cause the bottom hole temperature for horizontal wells rises above the static formation temperature. Results from the wellbore stability model show that the temperature variation magnitude in horizontal well is smaller than that in vertical wells, however, the effect of thermal stress on critical mud weight window in horizontal is more sensitive. The wellbore at toe of horizontal section is more stable than that at heel of horizontal section when the bottom hole temperature exceeds the static formation temperature. This research can provide a theoretical reference for enhancing overall operational efficiency and safety for horizontal well drilling. (C) 2015 Elsevier B.V. All rights reserved.