CO₂ flow in saline aquifer with salt precipitation

Abstract

Purpose

The purpose of this paper is to introduce the solution to two-phase flow in CO₂/brine system with salt precipitation by applying mixed hybrid finite element (MHFE) method to pressure equation and finite volume (FV) method to saturation equation. Mixed finite element method solves pressure and velocity in two subspaces while hybrid method is an extension of mixed method, where the Lagrange multiplier is added to the former in order to ensure the continuity from one element to the adjacent elements. The authors propose the modeling of salt precipitation using core flood experimental result and adapt to be applicable for numerical modeling.

Design/methodology/approach

The governing equations are discretized using Mixed Hybrid Finite Element-Finite Volume (MHFE-FV) method. This method has the feature of localized conservation which is attractive for application on heterogeneous porous media. In addition to this, the salt precipitation effect is modeled using the data from core flood experiment (Ott et al., 2011). The random data are linearized to obtain the relationship between salt precipitate and CO₂ saturation and implemented to the algorithm for two-phase flow in CO₂ and brine system.

Findings

The solution of MHFE-FV scheme has good agreement with the solution using implicit pressure and explicit saturation (IMPES) reported by Negara et al. (2011), with average error of 4.20 percent. Localized conservation is demonstrated in the case of randomized heterogeneous porous media where fingering effects are explicitly observed. Salt precipitation prediction using the proposed method is able to predict the decrement of porosity by 16.71 percent and permeability by 22.19 percent. This results in the decreased amount of CO₂ injected by 64.70 percent.

Research limitations/implications

This paper presents the solution of two-phase flow in CO₂ brine system during CO₂ injection in saline aquifer using MHFE-FV method with the additional salt precipitation model obtained based on core flood experiment result.

Practical implications

A methodology to predict the salt precipitation based on CO₂ saturation.

Social implications

Contribution to green house gas reduction.

Originality/value

The authors use MHFE-FV to solve hyperbolic PDE to obtain accurate results of CO₂ saturation, and subsequently use this to compute the salt precipitation.

Citation

Pau, J.S., Pao, W. and Yong, S.P. (2016), "CO₂ flow in saline aquifer with salt precipitation", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 26 No. 1, pp. 122-145. https://doi.org/10.1108/HFF-02-2015-0051