The use of flowback data for estimating dynamic fracture volume and its correlation with completion-design parameters: Eagle Ford cases

Abstract

Hydraulic fracturing combined with horizontal drilling is the key to unlocking vast unconventional reservoirs. However, understanding the relationship between completion-design parameters (CDPs) and fracturing efficiency remains challenging. The objective of this paper is analyzing flowback data to 1) evaluate the change in effective fracture volume (Vef), and 2) investigate the existence of correlations between CDPs and Vef. We analyze flowback data and CDPs of 22 gas and oil wells completed in the Eagle Ford formation. First, we estimate ultimate water recovery and initial effective fracture volume (Vefi) using harmonic-decline (HD) model. Second, we estimate the loss in Vef (Vloss) during flowback using a new iterative approach that accounts for dynamic fracture porosity and compressibility. Third, we introduce a new parameter to characterize fracture closure rate (FCR) during flowback. FCR represents how fast Vef shrinks during flowback. Then, we present a dimensionless type curve to evaluate FCR and investigate its correlation with CDPs. Finally, we conduct a multivariate analysis to correlate CDPs with Vefi and FCR.The developed correlation between Vefi and CDPs shows that the gross perforated interval (GPI) has the most significant effect on Vefi. The proposed correlation between FCR and CDPs demonstrates the significant effect of proppant concentration on fracture closure during flowback.