Hydraulic fracturing is the most efficient stimulation technique used to enhance productivity in low permeability reservoirs with the productivity enhancement strongly dependent on the resulting conductivity. In order to maintain conductivity under increasing load, proppant must be able to withstand the closure stress at the concentration level that it is present in the fracture. Among the most important characteristics for proppant selection are strength and bulk density.

Current standard procedure for measurement of proppant strength is based on concentration of 4 lb/ft2 and determination of percent crushed proppant under a specified load. The procedure does not represent realistic field conditions and fails to capture the effect of increasing closure stress on proppant and fracture conductivity loss. In this paper, a new technique to determine the failure stress of proppant is proposed and a summary of the results are presented. This new approach enables us to not only determine the behavior of different proppant pack over a wide range of pressures but also to determine failure point of proppant at a given concentration.

The new proppant crush test approach was used to compare the strength of 40/70 sand, 40/70 resin coated sand, 30/50 sand, and 30/50 resin-coated sand. The failure stresses for the above proppants were determined as a function of proppant concentration. A significant increase in failure stress was observed as proppant concentration varied from 0.5 to 2 lb/ft2. Failure stress was relatively constant for proppant concentration greater than 2 lb/ft2. In addition, different pattern of proppant behabior with closure stresse was observed for resin coated sand at concentrations above 2 lb/ft2 as compared to all other proppants and other concentrations.

You can access this article if you purchase or spend a download.