Study of Single Phase Mass Transfer between Matrix and Fracture in Tight Oil Reservoirs

Renyi Cao,Linsong Cheng,Yang Wang,Zhuoliang Guo,Yuanyuan Peng,Zhongyi Xu

doi:10.1155/2019/1038412

Abstract

In tight fractured reservoirs, oil in matrices is mainly explored due to mass transfer mechanisms during the pressure depletion process. In the modeling of mass transfer in fractured reservoirs using the dual porosity concept, the shape factor is the most important parameter and should be described accurately. However, the current shape factors are not suited for tight oil reservoir simulation because the characteristics of tight oil reservoirs are not taken into account. In order to solve this problem, a new mass transfer function for tight fractured oil reservoirs is proposed by introducing a new time-related correction factor which could consider not only the existence of the boundary layer in nano-microscale throats in tight porous media but also the heterogeneous pressure distribution in matrix blocks. In addition, special contact relations between matrix and fracture are included. The correction factor presented in this study is verified using the experimental data and numerical simulation results. Data analysis results demonstrate that the lower and slower the pressure propagation velocity, the longer the duration time of unsteady flow compared to conventional reservoirs. Therefore, in the calculation of mass transfer flow in tight oil reservoirs, the unsteady flow between fracture and matrix cannot be ignored.

Highlights

At present, the oil production process of tight oil reservoirs is normally applied after the artificial fracturing procedure
During the pressure depletion process, oil in matrix blocks is produced by the mechanism of single phase mass transfer, normally
Barenblatt et al assumed that the flow from the matrix to the fracture is pseudo-flow; Warren and Root [2] proposed a pseudo-steady analytical radical solution of single phase mass transfer flow in fractured reservoirs and applied the analytical solution in well test analysis

Summary

Introduction

The oil production process of tight oil reservoirs is normally applied after the artificial fracturing procedure. Simulation results reported by Bourbiaux shows that Coat’s calculation results are more in coincidence with the reference solution, and Kazemi et al.’s results deviate from fine grid results These mass transfer models mentioned above are proper for the conventional fractured oil reservoir in which the fluid flow in the matrix obeys Darcy’s law and the mass transfer between the matrix and the fracture can be assumed as a steady or pseudo-steady flow. Ranjbar et al [8] had investigated the effect of the fracture pressure depletion regime on the shape factor for a single-phase flow of a compressible fluid. The proposed model is verified by comparing with experimental data or simulation results

Mathematical Methods

Model Validation

Conclusion