Proppant performance can significantly affect production in unconventional plays. Quantifying the mechanical damage and conductivity of proppants are, however, challenging. This paper introduces a new method using Nuclear Magnetic Resonance (NMR) measurements to characterize pore-size distribution in proppant packs. Pore-size distribution is affected by mechanical damage and conductivity of proppant packs and can be used to evaluate these properties. We carried out NMR measurements on proppant packs to quantify the sensitivity of NMR T2 (spin-spin relaxation time)distribution to (a) different types of proppant with different surface relaxivity, (b) mixture of proppants with different sizes, and (c) proppants with different levels of mechanical damage.
The results showed that NMR T2 distribution is sensitive to pore-size distribution in the proppant packs which contained a mixture of proppants with different sizes and levels of mechanical damage. These measurements reflect the contribution of fines to the pore-size distribution of the proppant pack, and the effect of mechanical damage on different combinations of proppant size. We also observed measurable sensitivity of T2 distribution to the different levels of mechanical damage in the proppant packs, which enabled quantifying damage in proppants. The loss of pore volume predicted by NMR T2 distribution was in agreement with direct measurements applied on the proppant packs. Furthermore, we quantified the sensitivity of the NMR measurements to the proppants composed of different materials and coating. The results showed that NMR T2 distribution is sensitive to the presence of paramagnetic materials such as iron in the proppants, especially if well distributed on the proppant surface. The results confirmed that the new method enables evaluating mechanical damage in proppant packs through quantifying pore structure in the packs, which eliminates the challenges with fluid-flow-based conventional techniques.
Authors: Saurabh Tandon (The University of Texas at Austin), Aderonke Aderibigbe (Texas A&M University), Zoya Heidari (The University of Texas at Austin), Jingyu Shi (Saint-Gobain Proppants), Tihana Fuss-Dezelic (Saint-Gobain Proppants)
Paper Number: AAPG 2383015