Experimental study on seepage flow patterns in heterogeneous low-permeability reservoirs

Qiannan Yu,Xue Liu,Yikun Liu,Yang Yu,Di Yao

doi:10.1007/s13202-017-0354-y

Abstract

Heterogeneous artificial core plate models with low permeability are designed, made and evaluated based on similarity theory of heterogeneous reservoir with low-permeability physical simulation by artificial core plate model; then, simulative experiments for seepage flow patterns can be carried out. Pressure data are obtained by pressure transducers symmetrically arranged in artificial core plate models to study on the seepage flow patterns in heterogeneous reservoirs with low permeability. Experimental results show that the pressure gradient around injection and production points is high, and the pressure gradient of diagonal corner is very low. The distribution of pressure gradient changes as plane heterogeneity of artificial core plate models changes. The higher permeability increases the spread range of pressure, but the enhancement of heterogeneity has a negative effect on pressure transmission at the same time. The effect of permeability is greater than the negative impact of heterogeneous when the overall permeability of plate model is at a very low level. Non-seepage flow section becomes smaller with the increase in permeability, and the proportion of quasi-linear seepage flow section which is more conducive to fluid flow raise as seepage flow section becomes larger.

Highlights

The main object of water flooding in high-watercut oilfield has changed from homogeneous reservoirs with good physical property to heterogeneous reservoirs with low permeability or ultra-low permeability
Fluid seepage flow in reservoirs is the process of fluid flow by consuming pressure, and pressure gradient represents the pressure change in unit length along the pressure and fluid flow direction, so pressure gradient distribution of heterogeneous artificial core plate models with low permeability can reflect seepage flow patterns of heterogeneous low-permeability reservoirs
Pressure gradient distribution maps of artificial core plate models (Fig. 5) show that the pressure gradient contours are approximately elliptical with the well points as the center of the ellipse and connection line of injection and production points as long axis, and the integral form of pressure gradient contours of different plate models are Pressure gradient/(MPa/m)

Summary

Introduction

The main object of water flooding in high-watercut oilfield has changed from homogeneous reservoirs with good physical property to heterogeneous reservoirs with low permeability or ultra-low permeability. The seepage flow patterns in heterogeneous low-permeability reservoirs are basic problems to be further studied on. Qualitative description and quantitative characterization of seepage flow patterns in lowpermeability reservoirs in different heterogeneous conditions offer certain guidance in further study of seepage mechanism and oilfield production practice. There are many researches on fluid percolation characteristics in porous media, but the research of seepage flow patterns and relevant mechanism in heterogeneous low-permeability reservoirs is not systematic and perfect, and experiments are limited to relationship between pressure difference and fluid volume (Kortekaas 1985; Mala and Li 1999; Qu and Kong 2002) or experimental determination of relative permeability curves of natural cores (Zhang et al 2004; Li et al 2008). Sand packing method is carried out to simulate greatly varied sedimentary facies between injection and production points, permeability is controlled by particle size, and porosity is controlled by cement content and packing pressure (Pi 2010)

Methods

Results

Conclusion