A new mathematical model and experimental validation on foamy-oil flow in developing heavy oil reservoirs

Pengcheng Liu,Zhenbao Mu,Yongbin Wu,Xiuluan Li,Wenhui Li

doi:10.1038/s41598-017-08882-2

Abstract

To model foamy-oil flow in the development of heavy oil reservoirs, three depletion experiments were conducted with foamy oil treated as a pseudo-single-phase flow. In this pseudo single phase, dispersed bubbles are viewed as a part of the oil, and the redefined effective permeability varies with the changes of pressure depletion rate, oil viscosity, and gas saturation. A mathematical expression for the effective permeability was developed based on experiments, where the viscosity of foamy oil is assumed to be approximately equal to the saturated oil under equivalent conditions. The compressibility coefficient of foamy oil is treated as a volume-weighted compressibility coefficient of that of oil and gas phases. A new mathematical model for foamy-oil flow was proposed with consideration of foamy-oil supersaturation. To validate the mathematical model, the oil recovery and the production gas-oil ratio (GOR) calculated by the new model, conventional black oil model, supersaturation model and pseudo-bubble-point (PBP) model were all compared with those of the experimental data. The new model provided a substantially improved fit to the experimental data compared with the rest three models, which verifies the suitability of the mathematical model presented for simulating foamy-oil flow in the development of heavy oil reservoirs.

Highlights

Foamy oil is a term used to describe a type of unconventional heavy oil where gas bubbles are dispersed in a continuous oil phase[1,2,3]
For secondary or/and tertiary flooding by injected surfactants or/and other agents, as well as thermal energy, a compositional model is required and they are not the focus of this paper. This experimental part has two functions, the first one is to help establish a mathematical expression of foamy-oil relative permeability, in which the effective permeability was measured through experiments, and the second function is to help validate the accuracy of the model we proposed in this paper by comparing the recovery and production gas-oil ratio (GOR) of experiments with the new model and the other three models which have been proposed by other researchers
(1) According to the depletion experimental results, the redefined effective permeability of the sand pack varying with the pressure depletion rate, oil viscosity, and gas saturation, and an appropriate mathematical expression for the effective permeability on foamy-oil flow in porous media was developed

Summary

Introduction

Foamy oil is a term used to describe a type of unconventional heavy oil where gas bubbles are dispersed in a continuous oil phase[1,2,3]. The transformation from gases in solution to dispersed bubbles, and from dispersed bubbles to a continuous gas phase were both described as sequential-rate processes These models reflect an important feature of foamy oil, in which its characteristics undergo time-dependent changes, but the models are not valid for predicting the outcome of an evolving scenario under varying flow conditions. Pseudo-bubble-point (PBP) models assume that the continuous gas phase begins to form until the formation pressure is below the pseudo-bubble-point pressure, which is defined as an adjustable parameter in the description of this property of foamy oil[26, 27] Though this type of model can capture some important characteristics of foamy-oil flow in porous media, it cannot reflect its time-dependent changes. It indicated that this model is an advanced one and it is more suitable than other models to simulate the development of foamy oils

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Discussion

Conclusion