Productivity Prediction of Multistage Fractured Horizontal Wells in Tight Oil Reservoirs with Fully Coupled Flow and Geomechanics

Abstract

Tight reservoirs are subsurface formations with extremely low permeability, in which a high resistance to flow can be expected while developing hydrocarbons. Typically, to obtain economic production rates from such reservoirs, multistage fractured horizontal wells (MFHWs) are necessary. During reservoir development, the mutual coupling effect between fluid flow and stress fields cannot be ignored. In this study, a discrete fracture model (DFM) was proposed to simultaneously simulate reservoir deformation and fluid flow behaviors. The finite-element method (FEM) was utilized to obtain the numerical solution for both pore pressure and strain. The numerical simulator was verified using a commercial software, and perfect agreement was obtained. The results indicate that the coupling of flow and geomechanics has important effects on the evolution of the physical parameters of the formation. Some petrophysical properties of tight reservoirs noticeably deteriorate in the early stage of production; for example, the conductivity of hydraulic fracturing can be reduced by up to 90%. The effect of secondary fractures (SFs) on productivity is significant in the early stage. Natural fractures (NFs) mainly increase productivity when the pressure front reaches them at a later stage. Moreover, the tight oil flow capacity can be enhanced by increasing the hydraulic fracture (HF) density, initial conductivity, and the angle between the HFs and SFs. This study shows that fractures impact productivity, considering the full coupling of the flow and geomechanics of MFHWs in tight oil reservoirs. This provides valuable information for the design of hydraulic fracturing and production development programs.