A Composite Model for Multi-Stage Fractured Horizontal Wells in Heterogeneous Reservoirs

Abstract

Analytical multi-linear models are popular in the well testing analysis of multi-stage fractured horizontal wells (MFHWs). But such models are challenged now. In high density network of hydraulic fractures, the fluid flow around fracture tips no longer behaves like linear flow. Moreover, the production behaviors of hydraulic fractures are different at different stages in heterogeneous reservoirs. To overcome the two challenges, this study develops a semi-analytical composite model for MFHWs in heterogeneous reservoirs. The stimulated reservoir is regarded as a combination of several closed sub-systems with hydraulic fractures centered or uncentered. Each sub-system is further divided into several regions based on reservoir heterogeneity and flow characteristics. Reservoir and hydraulic fracture properties can be different in those regions. The production from each region is modeled by the solutions of linear flow equations or radial flow equations or source/sink functions. The production from a sub-system is modeled by coupling the solutions of regions in the sub-system. The production from the whole reservoir is then modeled by coupling the solutions of all sub-systems. The composite model was validated by analytical solutions in homogeneous reservoirs and numerical solutions in heterogeneous reservoirs. Calculations of production pressure and rates with this composite model generate type curves for the pressure and rate transient analysis of MFHWs. Two field cases are further analyzed with the type curves. One novelty of this model is to consider the non-linear flow around hydraulic fracture tips. Therefore, our model is better prepared for incorporating pressure-dependent heterogeneous reservoir properties in the future. The other novelty of this study is the ability to model the different production behavior at different fracture stages in complex heterogeneous reservoirs.

Pressure Transient Analysis and Transient Inflow Performance Relationship of Multiple-Fractured Horizontal Wells in Naturally Fractured Reservoirs by a Trilinear Flow Model

“…Moreover, there have been numerous works analyzing the performance of fractured wells through the transient pressure behavior and production decline analysis. − Zhang et al developed a semianalytical model to investigate the transient behavior of multiwing fractured vertical wells in coal-bed methane gas reservoirs considering the effects of adsorption–desorption, diffusion, and viscosity flow. Wang et al and Kou et al provided novel mathematical models of vertical wells with multiple radial hydraulic fractures in the stress-sensitive coal-bed methane reservoir to simulate the transient pressure responses.…”

Development and Calibration of a Semianalytic Model for Shale Wells with Nonuniform Distribution of Induced Fractures Based on ES-MDA Method

“…Currently, a lot of effort has been done to model the pressure transient and rate transient of MFHWs aiming to forecast the production accurately. Through numerical methods, analytical methods, and empirical methods [4][5][6][7], production data analysis in unconventional reservoirs, such as Barnett, Bakken, and Eagle, shows that the linear flow in formation, especially in hydraulic fractures (HFs) and SRV, dominates the production of MFHWs. Meanwhile, the advantage of analytic models is their simplicity and less parameters compared with numerical and empirical models, although they cannot characterize the over-complex heterogeneity properties and fracture system.…”

“…The unknowns including the well length, fracture number, conductivity, and length were determined by history matching. Yao et al [7] developed an analytical multi-linear model based on linear flow and radial flow assumption. Permeability and length of different regions, and fracture length were estimated by history matching with several field data.…”

Transient model analysis of gas flow behavior for a multi-fractured horizontal well incorporating stress-sensitive permeability

“…Lei et al (2016) proposed a comprehensive hybrid grid model and performance analysis workflow to study the impact of reservoir and hydraulic fracturing parameters on production performance of tight oil reservoir. Yao et al (2016) developed a semi-analytical composite model for multi-stage fractured horizontal wells (MFHWs) in heterogeneous reservoirs. The model was better prepared for not only incorporating pressure-dependent heterogeneous reservoir properties, but also investigating the different production behavior at different fracture stages in complex heterogeneous reservoirs.…”