Modelling of cohesive expandable LCMs for fractures with large apertures

Abstract

The problem of loss circulation in geothermal wells is inherently challenging due to high temperatures, brittle rocks, and presence of abundant fractures. Because of the inherent challenges in geothermal environments, there are limitations in selecting proper lost circulation materials (LCMs). Traditional LCMs such as calcium carbonates that are commonly used in the oil and gas drilling may be softened and prone to failure during geothermal drilling. Moreover, evaluating the performance of different LCMs for geothermal drilling requires unique testing setups, which is expensive, and complicated to run due to harsh environmental conditions of geothermal systems. Herein, we present a numerical approach to simulate LCM transport and bridging through fractures in downhole conditions. By discrete element methods, each individual particle trajectory, and their interactions with the fluid and surrounding particles are incorporated into the analysis. To validate the model, we used experimental results acquired from a high-temperature flow loop system built specifically for this purpose. We took a further step in this work and considered LCM particles that are made from a shape memory polymer (SMP). These particles start expanding and adhering to each other in downhole conditions. The use of SMP is shown to be advantageous in sealing large fractures (3 mm aperture). We demonstrated how numerical modelling may supplement laboratory tests to show initiation of the bridging process, fracture plugging or even its failure. Using the proposed methodology may significantly reduce the number of experiments needed to find an effective LCM recipe, hence drillers can save time and costs by assessing different LCM systems numerically.