Effect of Displacement Pressure on Oil–Water Relative Permeability for Extra-Low-Permeability Reservoirs

Abstract

The oil−water relative permeability is an important parameter to characterize the seepage law of fluid in extra-lowpermeability reservoirs, and it is of vital significance for the prediction and evaluation of the production. The pore throat size of extra-low-permeability reservoirs is relatively small, and the threshold pressure gradient and capillary pressure cannot be negligible. In this study, the oil−water relative permeability experiments with three different displacement pressures were carried out on the same core from the extra-low-permeability reservoir of Chang 4+5 formation in Ordos basin by the unsteady experimental method. The results show that the relative permeability of oil increases, while the relative permeability of water remains unchanged considering the capillary pressure and oil threshold pressure gradient compared with the JBN method. As the displacement pressure enlarges, the relative permeability of oil and water both increases; the residual oil saturation decreases, therefore the range of the two-phase flow zone is improved. Moreover, the isotonic point of water−oil relative permeability curves moves to the upper right region, and the reference permeability improves as well with the increasing pressure.

Experimental and Modeling Study of Water Imbibition and Flowback in Shale: Prediction of Relative Permeability and Capillary Pressure Curves

“…The displacement pressure also affects the relative permeability data in ultralow permeability reservoirs. 19 The dominant capillary end effect makes the measurement of water−gas relative permeability experiments on shale core plugs with limited length unreliable. The laboratory measurement of the relative permeability and capillary pressure curves of shale rocks is not feasible by conventional techniques of core flooding and centrifugal techniques.…”

“…As a result, a substantial water hold-up is generated at the outlet face of the core, forming a non-uniform saturation profile. The displacement pressure also affects the relative permeability data in ultralow permeability reservoirs …”

Stress-Dependent Fractal Model for Predicting the Relative Permeability of Rocks Based on Equivalent Capillaries

“…Two-phase flow in rocks is a ubiquitous phenomenon and has attracted widespread interest in many engineering fields, such as oil and gas extraction and storage, coalbed methane recovery, nuclear waste treatment, and pollutant transportation. , In oil and gas extraction, the relative permeability can fully characterize the basic two-phase flow properties and become an essential basis for estimating reservoir capacity, injection capacity, and ultimate recovery. , However, the extreme complexity and irregularity of rock pores make it extremely challenging to obtain relative permeability, which increases the difficulty in understanding the two-phase flow transport properties. Therefore, a simple and effective method to describe the flow characteristics of rocks and to obtain relative permeability has become a key problem to be solved in the current two-phase flow studies.…”

A New Method for Calculating the Relative Permeability Curve of Polymer Flooding Based on the Viscosity Variation Law of Polymer Transporting in Porous Media

“…Relative permeability curves can describe the seepage state of multiphase fluid in porous media and play important roles in many aspects, such as history matching and the design of oil field development schemes. Studies on oil-water relative permeability [11][12][13][14][15][16][17][18][19][20][21][22] and oil-gas relative permeability [23][24][25][26][27] were carried out in recent years. For the acquisition of oil-water relative permeability curves, except that a few studies used some parameters to predict [16][17][18], most of them were measured by experiments [19][20][21][22].…”