A comparative study on essential parameters to minimize sealing time in wide fractures

Efficient early-time plugging of wide fractures was aimed to investigate by considering granular lost circulation material (LCM) sizes, its concentrations, and geometries as the essential parameters. Fracture sealing time was experimentally investigated using sepiolite based mud prepared considering API standards. Steady shear flow, thixotropy loop and oscillatory dynamic shear tests were conducted using Discovery Hybrid Rheometer (DHR-II) to evaluate gel structure and particle suspension ability of sepiolite based mud as carrier fluid. The set of seventeen sieves 75–3360 μm was used for analyzing grain sizes of calcium carbonate (CaCO₃) as LCM. The effect of sixteen different LCM size ranges on the fracture sealing time was investigated through six slotted discs having different fracture widths (apertures) (508 μm–3048 μm) and lengths. Using wide range of sieve set allows providing uniform, bi-modal, and tri-modal particle size distribution of CaCO₃ pills as the fundamentals to investigate fracture sealing time. Upward flow direction was provided using Pore Plugging Apparatus (PPA) under 1000 psi of pressure differential. Fracture sealing time values were measured using precise pressure transmitter connected between experimental setup and computer. Sealing performance of LCM sizes and concentrations was visually evaluated using optical microscope. Results reveal that rheological characteristics particularly gel structure and thixotropy of carrier fluid are highly noteworthy. High degree of thixotropy and gel structure development make the sepiolite mud an active carrier fluid. Early fracture sealing time intensely depends on accurate combination of fine, medium, and coarse LCMs, particle size distribution, particle shape and concentration of LCM. Early sealing time and plug developing in wide fractures occurs efficiently by increasing modality in particle size distribution. The fine, medium and coarse LCMs must be added with optimum concentrations to seal fracture effectively and minimize sealing time.