Abstract

Aggressive drawdown on unconventional wells commonly leads to the return of proppant pumped during the stimulation treatment, reducing propped fracture aperture, with potential impact on hydrocarbon production. Despite being identified by the available literature as a source of concern to operators, how much proppant flowback affects unconventional well production is a question that remains unanswered. This study quantifies the impact of proppant flowback on gas production under different drawdown scenarios through numerical simulations history-matched with proppant production measurements in the field.

The numerical simulations were performed with a fully coupled reservoir, fracturing and geomechanics commercial simulator (ResFrac) using its module to simulate proppant flowback. The physical model employed to quantify proppant production was tested, validated, and improved with this study. Two different operators shared proppant flowback and production data from two gas wells in the Vaca Muerta Formation (Argentina) to carry out this analysis. Such field data was utilized to history-match proppant flowback data from unconventional wells for the first time. The calibrated models were used to understand the effect of drawdown management on proppant flowback and its impact on early-time gas production and its estimated ultimate recovery. A series of sensitivity analyses on critical variables in the model were also conducted to further study the potential influence of proppant flowback on gas production under different conditions. Results show that proppant flowback may not always be detrimental to gas production, and that its influence varies depending on each case.

Introduction

During completion operations in unconventional wells, proppant agents are pumped to prop fractures open after pumping stops. Often, a portion of the proppant flows back into the wellbore with the produced fluid during the clean-up phase after the stimulation. This phenomenon is known as proppant flowback and is highly undesirable since it can damage surface and downhole equipment (e.g., erosion of pipes, orifice, pumps, ESP, etc.) and may reduce well productivity.