Ranking shale performance from water flowback analysis, field case

In recent years, in unconventional reservoirs, main fracture parameters including fracture permeability and fracture volume can be early evaluated using flowback data analysis. For analysis purposes, diagnostic plots, straight-line methods, and simulation model history-matching techniques are utilized. Usually, immediate gas and water production occur during flowback in shale gas wells. In this paper, solution of water diffusivity equation for different flow regimes during the early time of well life was used to analyze water performance. These flow regimes were determined based on the diagnostic plot of water rate vs. time. The analysis from Water RTA was used to calculate initial water in place (OWIP) and fracture parameters. The difference between the OWIP and the injected fracturing fluid was correlated against the formation water saturation. The main conclusions from this analysis are; 1) High quality shale if the OWIP equal to the total injected water volume, and water-production data usually do not show the transient period and in some cases, boundary dominated flow (BDF) is present. 2) Low quality shale if the OWIP is greater than the total injected fracture fluid volume, and transient flow regimes are expected. High quality shale is good candidate for soaking process. The well performance increases after soaking process in the case of low formation water comparing to the high-water saturation wells. Honoring the flowback data can help to estimate the fracture geometry and indicate the quality of the shale formation.