Flowback rate transient analysis of multiphase flow through hydraulic fractures in gas condensate shales

Flowback rate transient analysis (RTA) of multi-fractured horizontal wells (MFHWs) in shale gas has historically focused on single-phase or two-phase water and gas flow, ignoring the presence of condensate. We introduce a multiphase flowback RTA for MFHWs in gas condensate shales, accounting for condensate dropout when the pressure in hydraulic fractures (HFs) falls below the dewpoint. We develop a semi-analytical multiphase flowback model to analyze flowback data during HF depletion. Three flow regimes are considered: a two-phase water and gas infinite-acting linear flow (IALF), a two-phase boundary-dominated flow (BDF), and a three-phase water, gas, and oil BDF. We derive pressure diffusivity equations for water-, gas-, and oil-phase flows and employ the material balance approach to determine the average HF pressure. Defined pseudo-variables facilitate the construction of diagnostic plots for flow regime identification and specialty plots for characterizing HF properties. We obtain diagnostic plots for each phase using the developed semi-analytical solution, in which the half-slope line indicates the IALF, while the unit-slope line signals the BDF. Additionally, we validate the developed models against numerical simulations. The results show that the estimated HF permeability and HF half-length from the models closely match the set values in the numerical model, with relative errors below 10%. Finally, we examine the applicability of the developed multiphase flowback model on an MFHW drilled in the Horn River Shale.