Successful appraisal of the CarbonNet Pelican CO2 offshore storage site

Abstract

The CarbonNet Project is operated by the state of Victoria, and jointly funded and managed by State and Federal governments. The Pelican storage site is situated in the shallow marine environment, between 1 to 15 km offshore from the iconic Ninety Mile Beach in Victoria, Australia. The site requires careful and diligent appraisal to demonstrate its suitability for safe and environmentally-benign permanent storage of CO2 at commercial scale. A 125 million tonne storage site has now been confirmed using new state-of-the-art high-resolution 3D seismic data covering the P90 probabilistic 3D volume of future plume travel in a wide range of scenarios and sensitivities. A new appraisal well (data well) has recently been completed, confirming pressure isolation across the main seal interval and suitable sandstone lithologies for storage, with excellent multi-layered reservoirs (up to 10 darcy permeability, over 150m net). The open-file petroleum database that is available to CarbonNet consists of over 1,500 exploration and development wells in this basin and “wall-to-wall” 3D seismic data offshore, supplemented by extensive onshore 2D seismic data. In addition, over 20,000 onshore boreholes targeting brown coal allow an excellent onshore-offshore stratigraphic correlation and detailed interpretation of depositional environments and facies geometries. The drilling and seismic acquisition were both successfully completed, and a wide range of data has been acquired which now enables detailed site characterisation to be fully completed and facilities design to commence. CarbonNet is following international codes of recommended practice for CO2 site characterization, and is working under Australian Greenhouse Gas legislation which contains detailed criteria for definition of a secure storage site - described as a Declaration of an Identified Storage Formation, and similar to a Storage Complex as understood in Europe and North America. The Storage Formation has been fully defined on the basis of pre-existing petroleum industry data. The new GHG data acquisition – well and 3D seismic – is aimed at delineating detailed reservoir and seal properties to inform the site development plan and consequent application for an Injection Licence. The topseal at the CarbonNet site is a sequence of intraformational shales with interbedded coals and minor sands/silts. These are proven by nearby hydrocarbon traps and by the pressure and salinity data from numerous local wells, including the recent appraisal well, Gular-1. A comprehensive set of conventional core and wireline log data was collected from the reservoir and overburden sections at Gular-1. This data will be used for detailed geomechanical studies to guide optimum reservoir injection of CO2. The excellent reservoirs are supported by a world-class aquifer with strong pressure buffering and dissipation capacity which will limit any local pressure increase due to injection. Aquifer performance is quantified by basin-wide pressure responses to a 60-year production history in this prolific petroleum basin. Development of the Pelican site will be linked through a multi-user hub to a potential onshore hydrogen production plant, and other industrial facilities. The CarbonNet project has commenced a commercialisation process for interested and capable industrial partners to participate in the whole project or in selected elements, including the pipeline transport system, storage site development and management, and in environmental and storage security monitoring. This shallow-water marine site offers unique monitoring challenges in terms of ecological sensitivity, operational visibility, and a high-energy marine environment. These challenges strongly affect the choices of effective monitoring technologies and the CarbonNet project has participated closely in field trials of a range of surface, water column, atmospheric, and subsurface sensing technologies in a range of projects conducted by the CSIRO, and leading Australian Universities. These projects have been commissioned and managed by ANLEC R&D.