An Experimental Study of LCM Effect on Formation Fracture Gradient to Improve Wellbore Strengthening

Drilling fluid plays an important role during the drilling operation of a well and can lead to a lot of problems or cure different challenges. Loss circulation is one of these challenges, which can increase non-productive time and operation costs, dramatically. The key solution for solving this problem is to increase the pressure-bearing capacity of the formation and to strengthen the wellbore with the help of drilling fluid. The purpose of this study is to design the "Wellbore Strengthening Evaluation" apparatus to simulate the formation fracturing process and investigate the LCM effects on the improvement of mud properties and rock fracture gradient. Therefore, in this paper, the cylindrical concrete cores are used as rock samples and Water-based bentonite drilling mud containing two different types of LCM are considered as drilling fluid. The results of experiments show that the addition of different LCMs to the drilling fluid leads to an increase in the formation breakdown pressure (FBP) and fracture reopening pressure (FRP) to 33 and 72%, respectively. Therefore, before drilling a formation with the possibility of loss circulation, it is an effective practice to add LCM particles in the drilling fluid to increase the fracture pressure of the formation.