Geochemical Stimulation in Siliciclastic Reservoirs to Enhance CO2 Injectivity

Abstract

One of the key challenges for the development of a CO₂ storage site is identifying and maintaining sufficient injectivity within a geologic formation. Even having a large storage volume, the reservoir's potential for storing CO₂ can be significantly reduced due to restricted flow impacting the injectivity. An example of such a case in Australia was the ZeroGen CCS project in Queensland. One of the major shortcomings due to which the project did not proceed further was low permeability of the storage units in the Northern Denison Trough causing limitations for projected industrial scale CO₂ injection. There are numerous reasons for low permeability in sandstone reservoirs. In most cases low permeability is associated with certain types of mineral overgrowth that cements interconnecting pore space within a formation. This study focuses on the application of geochemical stimulation in undamaged clastic reservoirs to enhance their permeability. Geochemical stimulation by acids and other pH controlled solutions can possibly promote mineral dissolution and increase permeability within a reservoir, and thus injectivity. The process of acidizing, as it is commonly known within the field of reservoir engineering, has been common practice in the oil and gas industry. The process has primarily been aimed at removing fines that result from formation damage while drilling or that accumulated over long period of production. So far, the technique has been applied in both sandstone and carbonate units using diverse methods to improve productivity in the near well bore environment. The current objective is to evaluate the efficiency of different solutions used for geochemical stimulation to bring substantial changes in the overall flow properties of a siliciclastic reservoir. The role of pH and temperature in controlling the dissolution rate of silica will be investigated with the help of batch reactors. Core flood experiments will be conducted using the most suitable chemistry to observe pore scale changes in the petro-physical properties of the rock samples at reservoir conditions. Effective deployment of a geochemical stimulation technique at field scale requires a synthesis and understanding of the underlying geochemical reactions coupled to flow properties within a reservoir. Thus, a reactive transport model will be developed to simulate enhanced injectivity at field scale under variable conditions using the ZeroGen project as a case study.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015