Numerical Modeling of Wellbore and Formation Temperature Recovery Prior to Cementing Operations.

Bottom Hole Circulating Temperature (BHCT) of cement slurry is the most critical operational parameter in cementing engineering, directly impacting operational safety and cementing quality. Prior to cementing, the temperature in the bottomhole wellbore and surrounding formation decreases during drilling fluid circulation and then gradually recovers during static periods. While most current BHCT prediction methods in oilfields rely on original formation temperature or geothermal gradient as benchmarks, they fail to account for the discrepancy between the actual postrecovery bottomhole temperature and the baseline formation temperature. A higher degree of temperature recovery correlates with a higher actual BHCT during cementing, and vice versa, making this relationship a key factor affecting prediction accuracy. This study analyzes the heat transfer model between the wellbore and formation, simplifies the physical structure based on model assumptions, proposes a novel wellbore boundary condition treatment method, and develops a transient temperature field mathematical model to numerically calculate temperature recovery in various regions of the wellbore-formation system. The study also comparatively analyzes the effects of fluid static duration, wellbore trajectory, and formation thermal conductivity. Results show that fluid circulation lowers temperatures in the lower well section and raises them in the upper section, with temperature gradually recovering during casing running and cementing preparation when fluid is static. Prolonged static periods attenuate heat exchange and temperature variations in the wellbore and formation while expanding the radial influence range in the formation. Following 2 h of static drilling fluid during cementing preparation, the hotspot temperature increased by 9.78 °C. After 24 h of casing running, the hotspot temperature rose by 26.67 °C, with subsequent increases of 3.54 and 1.47 °C observed at 48 and 72 h of static drilling fluid, respectively. For the bottomhole formation 1.2 m radially from the annulus, temperature was 0.05 °C lower than the original temperature after 24 h of circulation and further decreased by 0.46 °C, 0.4 °C, and 0.15 °C after 24, 48, and 72 h of static. Increasing the length of the buildup or horizontal sections reduces the degree of temperature recovery, while changes in formation thermal conductivity have minimal effect on temperature recovery values. The study emphasizes that incorporating preoperation bottomhole temperature recovery into BHCT prediction enhances forecast accuracy, thereby providing a theoretical foundation for optimizing cementing operation parameters.