A Two-Phase Flow Model for Pressure Transient Analysis of Water Injection Well considering Water Imbibition in Natural Fractured Reservoirs

Mengmeng Li,Jiaen Lin,Gang Bi,Qi Li

doi:10.1155/2018/2896251

Abstract

The pressure injection falloff test for water injection well has the advantages of briefness and convenience, with no effect on the oil production. It has been widely used in the oil field. Tremendous attention has been focused on oil-water two-phase flow model based on the Perrine-Martin theory. However, the saturation gradient is not considered in the Perrine-Martin method, which may result in errors in computation. Moreover, water imbibition is important for water flooding in natural fractured reservoirs, while the pressure transient analysis model has rarely considered water imbibition. In this paper, we proposed a semianalytical oil-water two-phase flow imbibition model for pressure transient analysis of a water injection well in natural fractured reservoirs. The parameters in this model, including total compressibility coefficient, interporosity flow coefficient, and total mobility, change with water saturation. The model was solved by Laplace transform finite-difference (LTFD) method coupled with the quasi-stationary method. Based on the solution, the model was verified by the analytical method and a field water injection test. The features of typical curves and the influences of the parameters on the typical curves were analyzed. Results show that the shape of pressure curves for single phase flow resembles two-phase flow, but the position of the two-phase flow curves is on the upper right of the single phase flow curves. The skin factor and wellbore storage coefficient mainly influence the peak value of the pressure derivatives and the straight line of the early period. The shape factor has a major effect on the position of the “dip” of pressure derivatives. The imbibition rate coefficient mainly influences the whole system radial flow period of the curves. This work provides valuable information in the design and evaluation of stimulation treatments in natural fractured reservoirs.

Highlights

The methods for pressure transient analysis of water injection well mostly still use the conventional well test method of single phase flow
We proposed a semianalytical oilwater two-phase flow imbibition model for pressure transient analysis of a water injection well in natural fractured reservoirs
Validation of the presented model was performed by analytical method and a field water injection test

Summary

Introduction

The methods for pressure transient analysis of water injection well mostly still use the conventional well test method of single phase flow. The total mobility, skin factor, and average formation pressure can be obtained based on this method If it is a two-phase flow well test model of a water injection well, a multizone composite reservoir model [3,4,5,6,7,8] is used due to the different properties of the injected fluid and the reservoir fluid. Some scholars [9,10,11,12,13] developed a two- or threezone composite reservoir well test model by finite-difference or Laplace transformation method to get the pressure curves for water injection and pressure falloff period These models assumed no saturation gradients within oil and water transition zone and the zone boundaries were virtually stationary before the well shut-in. New ideas had been put forward in accordance with the analysis above

Model Description

Pressure Transient Model

Verification of the Mathematical Model

Model Features Analysis

Conclusions