A Semianalytical Method for Two-Phase Flowback Rate-Transient Analysis in Shale Gas Reservoirs

Abstract

Summary We propose a new semianalytical method for analyzing flowback water and gas production data to estimate hydraulic fracture (HF) properties and to quantify HF dynamics. The method includes a semianalytical flowback model, a set of two-phase diagnostic plots, and a workflow to evaluate initial fracture volume and permeability, as well as fracture compressibility and permeability modulus. The flowback model incorporates two-phase water and gas flow in both HF and matrix domains and considers variations of fluid and rock properties with pressure. The HF domain is modeled by boundary-dominated flow, whereas an infinite-acting linear flow is assumed for the matrix domain. The flowback model is developed by assigning the variable average pressure in the fracture as the inner boundary condition for matrix according to Duhamel's principle. The average pressure in the fracture and distance of investigation (DOI) in the matrix are calculated from a modified material-balance equation by updating the matrix DOI as well as phase saturation and relative permeability in both the fracture and matrix domains. A modified DOI equation is used for two-phase flow in the matrix, which considers the pressure-dependent fluid and rock properties in pseudotime. The diagnostic plots shed light on the identification of flow regimes during the coupled two-phase flow in both fracture and matrix. The proposed workflow quantifies the HF dynamics through the loss of both fracture volume and fracture permeability by reconciling flowback and long-term production data. The accuracy of the new method is tested against numerical simulations conducted by a commercial numerical simulator. The validation results confirm that the proposed method accurately predicts initial fracture volume, permeability, and permeability modulus. Further, we use production data from a multifractured horizontal well (MFHW) drilled in Marcellus Shale to test the practicality of the proposed method. The results show a significant reduction in fracture volume and permeability during production attributable to the HF closure.

A fracture upscaling method (FUM) for hydraulically fractured reservoirs: From discrete fracture modelling to finite difference simulations

“…Y and Y are the matrix and fracture permeability modulus, respectively. The values used in this study for these parameters are provided in Table 1 (Zhang & Emami Meybodi, 2020).…”

A Novel Mathematical Model for Fracturing Effect Evaluation Based on Early Flowback Data in Shale Oil Reservoirs

“…Here, we use Equation (35) to combine the average reservoir pressure with the pressure in the fracture and the bottom hole flow pressure:…”

“…The effective compression coefficient term and the linear dynamic relative permeability function were introduced to extend the existing singlephase analysis and two-phase simulation models to the analysis of shale gas reservoir flowback data. For shale oil reservoirs, Chen et al [33][34][35][36][37][38][39] proposed a flowback model for complex fracture network shale oil reservoirs. During the numerical solution and inversion processes, it was necessary to use numerical solutions and semianalytical solutions to describe the flow of two-phase water and oil in a fracture and matrix system.…”

Semianalytical method of two‐phase liquid transport in shale reservoirs and its application in fracture characterization

“…The conceptual flowback model describing water and oil flow through fracture and matrix is shown in Figure 1. This model is expanded from the two-dimensional two-phase model developed for shale gas reservoir 29 and thus has the same assumptions of HF as before, which ignores the complex fracture geometry and stress-shadowing effect.…”

“…A set of two-phase diagnostic plots have been proposed to identify flow regimes during flowback of shale gas reservoir. 29,36,37 In this article, we expanded the diagnostic plot proposed by Zhang and Emami-Meybodi 29 to oil reservoirs to F I G U R E 1 Schematic of the conceptual model depicting water and oil transport through fracture and matrix (SEM image from Naraghi, Javadpour 28 ) identify the fracture infinite acting linear flow (IALF), that is, FR1, and fracture boundary-dominated flow (BDF), that is, FR2.…”