Impact of Particle Size Distribution on Fracture Sealing Capability; a Simulation for Better Geothermal Drilling

Abstract

Geothermal reservoirs are typically naturally fractured with large permeable channels and openings. Without proper treatments, these situations may result in problems such as well control and an increase in non-productive time. Some treatment options include underbalance drilling and the additive of lost-circulation materials (LCMs). The unpredictive nature and abnormally large fracture sizes in geothermal wells make it difficult to design proper LCM size distribution. Especially under high-temperature conditions, reduction of mechanical properties can occur, such as Young’s modulus and particle sizes. A successful design in preventing or mitigating lost-circulation event can alleviate large drilling costs. The use of LCMs can be inexpensive and effective. Most commonly seen LCMs can be categorized as flaky, granular, or fibrous. The fracture sealing results of granular LCMs have been tested. In this paper, the computational fluid dynamics (CFD) and discrete element method (DEM) are employed to simulate fracture sealing of non-granular LCMs. A smoothed fracture with narrowing end is created to study fracture sealing phenomenon. Various combinations of different size distribution and aspect ratios will be tested to compare the effectiveness of fracture sealing.