Geomechanical analysis of formation deformation and permeability enhancement due to low-temperature CO2 injection in subsurface oil reservoirs

Ilyas Khurshid,Yoshiaki Fujii

doi:10.1007/s13202-021-01133-1

Abstract

Several benefits of CO2 injection are reported in the literature such as its ability to mitigate greenhouse gas emissions and the increase in oil recovery at a low cost. However, the correlated reservoir-engineering problems with low-temperature CO2 injection including formation damage and leakage risk are still uncertain and has not been comprehensively investigated. This research examines the effect of low-temperature CO2 on lowering of formation breakdown pressure, and the associated formation damage from a geomechanical prospective. This study presents the coupling of the equilibrium stress equation, the system energy balance equation, continuity equation, and saturation equation to develop thermoporoelastic model for the reservoir rock. We determined the cooling-induced formation damage due to decrease in temperature and thermal stresses, formation contraction and tensile stresses, and examine its effects on formation properties, stresses, joint and fracture stability. We observed that low-temperature CO2 would create a low thermal stress region and thus the formation could fail in tension. This process might increase formation permeability but it would decrease the stability of reservoir, basement and caprock. We analyzed several factors affecting formation deformation such as injection rate for both miscible and immiscible CO2 flooding, formation porosity, depth, temperature, and formation breakdown pressure. We also compared our results and findings with experimental data, finding excellent match and similar consequences. Furthermore, as a sequence of low-temperature CO2 injection, the initial formation breakdown pressure was initially at 2560 psi and it reduced to 1928 for immiscible case and 1270 psi for miscible case in the selected case study. We also propose that shallow reservoirs should be avoided for CO2 capture and storage because of stability issues.

Highlights

Carbon dioxide ( CO2) sequestration is gaining a lot of interest from academia and industry because of its potential to store CO2 and mitigate its release into the atmosphere
In this study, our goal is to investigate the magnitude of formation temperature, CO2 temperature at wellbore entry, formation temperature reduction, thermal stresses and change in formation breakdown pressure during C O2 injection
The effect of low-temperature C O2 injection on lowering of formation breakdown pressure and formation damage has been successfully predicted from a geomechanical aspect using the coupled thermoporoelastic model

Summary

Introduction

Carbon dioxide ( CO2) sequestration is gaining a lot of interest from academia and industry because of its potential to store CO2 and mitigate its release into the atmosphere. The CO2 can be sequestrated in a number of subsurface geological structures including un-useable saline aquifers, depleted oil and gas fields, and un-mineable coal seams (Bui et al 2018). Division of Sustainable Resources Engineering, Hokkaido University, Sapporo, Japan in supercritical conditions in a denser phase but its density would be lower than the formation water (Hitchon et al 1999). The depleted oil and gas reservoirs are the most important, because these reservoirs are studied in detail, monitored for long during oil and gas production, and CO2 can be efficiently stored in these reservoirs. For safe and sustainable storage of C O2, it is important that the temperature and pressure conditions of these reservoirs should be critically analyzed. It will help to ensure that CO2 is stored safely without any risk of leakage, as its leakage may cause an environmental catastrophe (Parisio et al 2019)

Objectives

Findings

Conclusion