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

• An integrated temperature model for horizontal well drilling has been developed and field-tested.
• The bottom hole temperature sometimes may exceed the formation temperature.
• The critical mud weight window at toe of horizontal section is different from that at heel of horizontal section.
• Decreasing the temperature will narrow down the critical mud weight window.

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.