Study of the performance of LCMs in fractured formations.
Leandro Galves, Stefan Miska, Evren Ozbayoglu, Małgorzata Ziaja
Vol. 34, no. 1 (2017), s. 103-121, 
This study focuses on modeling three phenomena that greatly affect the performance of lost circulation materials (LCMs) in sealing thief zones: the process of construction of the LCM seal, the final flow rate after its creation, and the fractability of this seal to the pressures inside the wellbore. To model them, concepts related to fluid mechanics, and geomechanics become of the utmost importance. To help the validation of the models presented in this work, an experimental facility to simulate lost circulation was constructed. The facility makes use of a real limestone core drilled with the Tulsa Drilling Research Projects (TUDRP) drilling rig. This experimental setup represents progress in the reproduction of overall field conditions in comparison with other setups found in the literature. Several tests were performed with walnut at different sizes and concentrations, as well as with distinct fracture openings, inclinations, and orientations. As a result, a D90 as large as the size of the fracture aperture ends up to being effective in the plugging process. In addition, a D50 the size of 1/3 of the fracture opening also provides of a good seal. Depending on the concentration, smaller sizes can be applied - the smaller the size is, the larger the concentration must be. Finally, a computer program has been developed. Estimations of particle size distribution (PSD), plug time, and flow rate after seal formation are outcomes. This method of LCM selection can be used to assess the performance of different LCMs in the field. Hence, cost, time, and energy can be saved in dealing with lost circulation.