Experimental Investigation of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-Water-Rock Interactions during CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Flooding in Carbonate Reservoir

Na Xiao,Meiqin Lin,Shi Li

doi:10.4236/ojogas.2017.22008

Abstract

Injecting CO2 into underground reservoir to displace oil is a viable means of reducing greenhouse gas emission to the atmosphere and enhancing oil recovery. To evaluate the effect of CO2-water-rock interactions on the characteristics of carbonate reservoir at high pressure, the mineralogy of calcite, the ion concentration in the reacted solution, the surface texture of calcite, the permeability of calcite after reacted with injected CO2 and deionized water was investigated by X-ray diffraction (XRD), inductive coupled plasma-atomic emission spectrometry (ICP-AES), scanning electronic microscope (SEM), and sand-packed model at pressure of 5.0 MPa. The results show that the mineral dissolution of calcite would occur when interacting with injected CO2 and water. The mineral dissolution of calcite caused the change of surface texture of calcite and increase in Ca2+, HCO-3 ion concentration in the solution. With the increase of CO2 pressure, the surface dissolution of calcite appeared more obvious. With the increase of reaction temperature, the surface dissolution of calcite also appeared more obvious and Ca2+, HCO-3 ion concentration in the solution increased first, then decreased. The mineral dissolution of calcite caused the improvement in water permeability of calcite/quartzsand-packed model.

Highlights

To evaluate the effect of CO2-water-rock interactions on the characteristics of carbonate reservoir at high pressure, the mineralogy of calcite, the ion concentration in the reacted solution, the surface texture of calcite, the permeability of calcite after reacted with injected CO2 and deionized water was investigated by X-ray diffraction (XRD), inductive coupled plasma-atomic emission spectrometry (ICP-AES), scanning electronic microscope (SEM), and sand-packed model at pressure of 5.0 MPa
The results show that the mineral dissolution of calcite would occur when interacting with injected CO2 and water
1) The mineral dissolution of calcite would occur when interacting with injected CO2 and water, and the dissolution caused the change of surface texture of calcite

Summary

Introduction

The porosity and permeability of the reservoir [13] [14] [15] [16] [17], the wettability of the rock surface and the characteristics of the crude oil will be changed by the reaction between carbonic acid and the rock [18] [19], which will affect the efficiency of CO2 flooding and geological sequestration of CO2 [20] [21] [22]. Carbonate reservoir is mainly composed of calcite, dolomite, ankerite and magnesite, and these minerals can dissolve in carbonate solution which leads to corrosion of the rock and increase of reservoir permeability. Izgec [24] pointed out that a large number of loop hole formed in the process of the dissolution of carbonate mineral, it obviously improved the connectivity of pore, and so caused the permeability improved significantly. Some scholars pointed out that the change of physical property of carbonate reservoir was related to formation water pressure, temperature, and rock mineral composition and CO2 partial pressure [26]

Methods

Results

Conclusion