Mechanisms and Modeling of Proppant Production in Shale Gas Reservoirs: A Systematic Analysis

Horizontal wells combined with effective fracture stimulation enabled economic development of shale gas reservoirs. During fracturing, propping agents are placed in the created hydraulic fractures to maintain a highly conductive flow path for fluid flow. While, post stimulation, proppant flowback and production may occur. To date, mechanisms of proppant production are not well understood, even though past experimental and theoretical studies indicated that fracture width, hydrodynamic forces, and closure stress are primary factors affecting proppant production. This study aims to investigate the mechanism that affects and induces proppant production in shale gas reservoirs during the recovery period. In this paper, we will (1) first understand the physics of proppant production through a critical review and analysis of laboratory studies and published work in the literature; (2) build a reservoir model with an unpropped arch to simulate long-term gas recovery and proppant production; (3) develop a script to compute the percentage of the arch capable of producing proppant based on gas flow velocity, Reynolds number, and Shields number with various arch conductivity, pore pressure, fracture spacing, landing point, and propped height; (4) conduct a comprehensive and systematic analysis to investigate how proppant production occurs; and (5) provide guidelines to mitigate and prevent proppant production. On the basis of our results and analyses, proppant production mainly occurs due to creeping. Higher arch conductivity and higher pore pressure lead to more severe proppant production. In the field, gas production management and changing the landing point from top to bottom of the formation are ways to prevent and minimize proppant production. When landing at the bottom of a formation, proppant production could be avoided, while landing at the upper of the formation could result in 11% to 29% of proppant production. The guidelines developed in this study can help mitigate proppant production in field applications, maintain fracture conductivity, and increase long-term gas recovery.