Stress history influence on sedimentary rock porosity estimates: Implications for geological CO2 storage in Northern Taiwan

Andrew Tien-Shun Lin,Lun-Tao Tong,Chuen-Fa Ni,Toshihiko Shimamoto,Wen-Jie Wu,Tsun-You Pan,Ming-Hsu Li,Jia-Jyun Dong,Yun-Chen Yu

doi:10.3319/tao.2015.09.21.03(gsc)

Abstract

We established a stress-history-dependent porosity model of potential target rocks for CO_2 geosequestration based on rock sample porosity measurements under various effective stresses (5 - 120 MPa). The measured samples were collected from shallow boreholes (＜ 300 m depth) drilled at the frontal fold in northern Taiwan. The lithology, density, and the stress-history-dependent porosity derived from shallow boreholes enabled us to predict the porosity-depth relationship of given rock formations at (burial depths of approximately 3170 - 3470 m) potential sites for CO_2 geosequestration located near the Taoyuan Tableland coastline. Our results indicate that the porosity of samples derived from laboratory tests under atmospheric pressure is significantly greater than the porosity measured under stress caused by sediment burial. It is therefore strongly recommended that CO_2 storage capacity assessment not be estimated from the porosity measured under atmospheric pressure. Neglecting the stress history effect on the porosity of compacted and uplifted rocks may induce a percentage error of 7.7% at a depth of approximately 1000 m, where the thickness of the eroded, formerly overlying formation is 2.5 km in a synthetic case. The CO_2 injection pressure effect on the porosity was also evaluated using the stress-historydependent porosity model. As expected, the pore pressure buildup during CO_2 injection will induce an increase in the rock porosity. For example, a large injection pressure of 13 MPa at a depth of approximately 1000 m will increase the rock porosity by a percentage error of 6.7%. Our results have implications for CO_2 storage capacity injection pressure estimates.

Highlights

Carbon dioxide capture and storage (CCS) is a promising technology for reducing anthropogenic CO2 emissions into the atmosphere (Bachu 2000; Lackner 2003; Wilson et al 2003; IPCC 2005; Bachu et al 2007; Bradshaw et al 2007)
We demonstrate the stress history influence on rock porosity estimates during maximum burial depth using laboratory-measured rock porosities from rocks recovered from uplifted formations
These results indicate that the injection pressure effect on the porosity becomes measurable as the injection pressure increases

Summary

Introduction

Carbon dioxide capture and storage (CCS) is a promising technology for reducing anthropogenic CO2 emissions into the atmosphere (Bachu 2000; Lackner 2003; Wilson et al 2003; IPCC 2005; Bachu et al 2007; Bradshaw et al 2007). Predicting the CO2 storage capacity and the migration of the injected CO2 plume is central to CO2 geosequestration. The rock permeability and porosity are two critical parameters that govern the CO2 storage capacity and plume migration (Juanes et al 2006; Bachu et al 2007). Conventional laboratory experiments (e.g., the imbibition method) and core logging are typically used to evaluate the rock porosity under atmospheric pressure. The influence of the stress history (such as sediment burial, uplift by folding and faulting, and subsequent exhumation) on the porosity of a given rock succession (Wu and Dong 2012) is difficult to evaluate using these methods. A method to evaluate the stress-history-dependent porosity, taking into account the pressure buildup effect from CO2 injection, is required

Results

Discussion

Conclusion