Mono & Thin Layer Performance of Small Mesh Size Proppants Placed in Horizontal Well Fracture Matrices

Abstract

Abstract Today unconventional completion objectives strive toward three major goals: creating large fracture networks, placing as much proppant in those networks as efficiently as possible and ensuring fracture conductivity is sufficient to allow for maximum reservoir drainage. While operators use different, and often proprietary, completion protocols to achieve these goals, market research shows a growing trend towards the use of small mesh size proppants such as 30/50, 40/80 or even 100 mesh proppants primarily utilizing slickwater fracturing fluid systems. Fracturing of unconventional reservoirs in this manner creates a very narrow fracture environment. This creates a completion design problem as most proppant types and sizes are qualified using 2 and 4 lb/ft2 loading conditions to simulate the wider fractures of conventional sandstone reservoirs. Further complication also lies in the fact that prior to shale development, small mesh size proppants, such as 100 mesh were very rarely used or tested as a proppant. The study compares the mechanical strength of 40/80 white sand, 40/80 clay-based economy lightweight ceramics (ELWC) and 40/80 bauxite-based intermediate strength ceramics (ISC), as well as, 35/140 bauxite-based intermediate strength ceramic (ISC) and 100 mesh sand using standard and modified API RP 19-C crush resistance tests. During testing, load cell concentrations were varied from the standardized 4 lb/ft2 to the modified concentrations of 0.5 and 0.25 lb/ft2 – concentrations more realistic for unconventional reservoirs. Mechanical failure of proppants is quantified by comparing proppant size distribution pre- and post-stress application using a Horiba CAMSIZER. Mechanical compression of proppant packs is measured during testing and compared for different proppant types. Failure mechanism of proppants is also evaluated using an in-situ high pressure CT scanning protocol enabling visualization of the proppant failure as a function of applied load, proppant type and concentration. The study shows that mechanical performance of tested materials, measured as proppant crush, deteriorates with decrease in proppant bed height. Deterioration of performance is, however, much less pronounced for small mesh size proppants than previously studied large mesh proppants. Contrary to that, pack compression results indicate higher compression of small mesh proppants under monolayer/thin bed conditions suggesting a large decrease in proppant pack conductivity. The most extreme pack compression is measured for 100 mesh sand proppants. In-situ CT scans also confirm these results and further visualize the effect of pack compression on proppant pack conductivity.