Allison Hortle

Safe storage and effective monitoring of CO2 in depleted gas fields

Carbon capture and storage (CCS) is vital to reduce CO2 emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO2 storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO2 storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO2.

Baseline characterisation and monitoring protocols for development of shale and tight gas resources, northern Perth Basin

CSIRO, in collaboration with Latent Petroleum, AWE Limited, Origin Energy, Norwest Energy and the WA Department of Mines and Petroleum (DMP) have established a research program into methods of calculating baseline values of environmental indicators and monitoring techniques during development of tight gas resources in the northern Perth Basin. As part of the project, a desktop review of available groundwater monitoring data around the sponsors’ permit areas was conducted, along with measurements of ambient methane (CH4) concentrations. The groundwater study indicated a lack of monitoring wells within the permit areas, apart from those being monitored by explorers, and provides a valuable update to the regional groundwater models built by the WA Department of Water (DoW). The mobile CH4 survey measured ambient levels of CH4 across the basin, and CH4 concentrations were close to those measured at the Cape Grim atmospheric research station (Tasmania). The soil-gas flux survey measured very low or negative CH4 flux, closely associated with carbon dioxide (CO2) levels, indicating the flux rate was controlled by microbial action. The outcomes of the project are intended to assist operators to address community assurance, adhere to or surpass regulatory requirements and establish industry best practice standards.

Impact of faults and compartmentalisation on geological carbon storage estimates in highly faulted basins

Faults have extensively been studied for hydrocarbon exploration and production; however, previous studies on fault behaviour for geological carbon storage have focused on sealing capacity or reactivation potential during injection or post-injection phases. Little is known on the impact of faults for estimating storage capacity in highly faulted basins. A geological conceptual model of a representative compartment was designed to identify the key drivers of storage capacity estimates in highly faulted basins. An uncertainty quantification framework was then designed upon this model to address the impact of geological uncertainties such as fault permeability, reservoir injectivity, compartment geometry and closure on the compartment storage capacity. Pressure-limited storage capacity was estimated from numerical simulation of CO2 injection under the constraints of maximum bottom hole pressure and fault reactivation pressure. Interpretation of the simulation results highlights that (1) two injection regimes are observed: borehole- or fault-controlled, (2) storage capacity can vary more than an order of magnitude, (3) fault and reservoir permeability can be regarded as the most influential properties with respect to storage capacity, (4) compartment geometry mainly influences the injection regime controlling the storage capacity and (5) the large sensitivity of storage capacity to the type of enclosure and fault permeability indicates that pressure build-up at the fault is often the deciding factor for CO2 storage capacity.