LAUSR

Abstract In oil and gas well drilling operations, lost circulation is characterized by the invasion of drilling fluid into permeable formations. Besides generating additional costs to the process, the loss of circulation can damage producer formations and, if uncorrected, reduce pressure inside the well, inducing kicks. One of the alternatives for combating this problem is the addition of lost circulation materials (LCM) to the drilling fluid. The added LCMs will accumulate and form a filter cake on the interface between the well and the porous formation, thus reducing the volume of fluid lost. In the present work, the cake formation process resulting from the deposition of particulate material on a porous substrate is studied experimentally. The objective is evaluating the influence of type and concentration of two polymeric additives and four types of LCM on the formation of the filter cake. The experiments were carried out in an API filter press at pressures of 100 psi, using solutions of carboxymethylcellulose (CMC) and xanthan gum (XG) in water at 1.05 and 2.10 lbm/bbl. The particle size used as loss of circulation material comprises two values (2 – 44 and 44 – 106 μ m) of calcium carbonate (CaCO 3 ), glass microspheres (180 – 300 μ m), and plastic particles (250 – 420 μ m). The efficiency of the fluid-LCM combination in combating lost circulation is evaluated based on the filtrate volume, thickness, dry and wet cake masses, and filtrate flow curves. Results show that the increase of the LCM concentration and the use of the calcium carbonate particulate with smaller particles favor the filtrate volume reduction. Also, the filtrates exhibit non-Newtonian behavior with reduced values of viscosity due to the retention of polymeric chains by the formed filter cake. Such phenomenon is most significantly detected when calcium carbonate is used.