Analysis of analytical fracture models for wellbore strengthening applications: An experimental approach

摘要

Drilling fluid losses are challenging to prevent or mitigate during drilling. Lost circulation treatments are applied to stop losses using a corrective approach or to hinder losses using a preventive approach, also known as wellbore strengthening. The key factors that must be determined when treating losses are the fracture width and the required particle size. The fracture width is often estimated using analytical fracture models. In this paper, five different fracture width models were analyzed and compared to hydraulic fracturing experiments. The hydraulic experiments were conducted on impermeable concrete cores to investigate the effect of adding lost circulation materials (LCM) to enhance the fracture breakdown pressure and the fracture re-opening pressure. The results showed that adding LCM blends enhanced the breakdown pressure up to 18% and the re-opening pressure up to 210%. The cores that were fractured with fluid-containing solids had a larger fracture width compared to the fractured cores using base fluid. Comparing the measured fracture widths from experiments with analytical models showed a discrepancy in the fracture width estimation for all of the models and the experiments, except for one model. (C) 2016 Elsevier B.V. All rights reserved.