During continues drilling operation, temperature goes on increases with decreasing in specific energy, what the main reason. What is the technical reason behind this.
Often, a rise in formation temperature corresponds to an increase in pore pressure. That will reduce effective stresses, decreasing the MSE and the energy required to break the rock. But there many factors affecting MSE. You might want to check SPE Paper 178842, "Pore-Pressure Estimation by use of MSE and Drilling Efficiency", Majidi, Albertin & Last.
Please check the pore preasure acted in the bottom of drill bit and the current drilling formation. Under small preasure and granular formations' conditions, the temperature may still rise while the MPE may decrease. Hope that will be helpful.