Abstract

Proppant placement plays an important role in stimulation effectiveness. In recent years, numerous studies have been conducted to understand proppant transport in both wellbores and fractures. However, achieving uniform proppant placement in each perforation cluster remains a challenge for fracturing treatment optimization. This paper experimentally investigates the impact of key parameters on proppant placement at both perforation and cluster levels. The parameters studied include perforation orientation, pumping rate, fluid rheology, proppant size, etc. A key focus in this study is to investigate the effect of perforation orientation on proppant distribution among individual perforations and clusters.

A novel horizontal wellbore apparatus with four modular perforation clusters was constructed. Each cluster is removable and the perforation number, spacing, size and orientation in each cluster can be adjusted. The unique setup allows the measurement of fluid and proppant exiting through individual perforations with different orientations along the horizontal pipe. Numerous experimental tests were conducted using 100 mesh brown and 40/70 white sand. Various types of fluids, including Newtonian fluids (fresh water and glycerin solution) and slickwater with two commercial friction reducers at various loadings, were used in the tests.

Test results show that perforation orientations have significant impact on proppant distribution, specifically at low flow rates. Gravitational effects become dominant over the momentum and viscous forces at low flow rates and cause more sand to exit perforations at the lower side of the wellbore. Conversely, at higher flow rates, the momentum effects have greater influence on proppant distribution among all clusters, particularly for perforations in clusters toward the heel. This is because larger proppant particles with greater momentum are unable to turn into the perforations in clusters near the heel. In addition, the experimental results show that proppant placement was substantially improved when all perforations were designed with the same orientation in each cluster.

The test results demonstrate that slickwater, even with very low FR loadings, can substantially enhance proppant suspension and transport in comparison with Newtonian fluids. The findings in this paper provide new insights into perforation orientation effects on proppant placement, and how to achieve uniform proppant placement and optimized treatment design via appropriate perforation design.

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