SPE Projects, Facilities & Construction
Volume 2, Number 3, September 2007, pp. 1-6

Summary

This paper describes and reports the results of analyses of the costs of carbon dioxide (CO2) capture and storage in southwest Western Australia. We analyze the costs of capturing approximately 22 million tonnes per year of CO2 and injecting it into one of three storage sites: the Gage sandstone offshore Perth, the Dongara depleted gas field, and the Neocomian subcrop offshore Geraldton.

The central estimates obtained are that the real cost to capture, transport, and inject CO2 for a period of 25 years is between 59 and 63 Australian dollars (AUD) per tonne of CO2 avoided (in 2005 terms), depending on the location of the injection site.

The sensitivity of these cost estimates to changes in key assumptions is also analyzed. These sensitivity analyses show that the costs of carbon capture and storage (CCS) can vary significantly with different assumptions for key variables.

Introduction

The area in and surrounding Perth in Western Australia emits more than 25 million tonnes (Mt) of CO2 from stationary sources every year. Most of these emissions come from large industrial complexes, including power stations, metal manufacturing facilities, and petrochemical plants.

CCS involves separating CO2 from a mixed-gas source into a concentrated stream, compressing it to a supercritical state, and then transporting it to an injection site, where it will be injected into suitable formations in the subsurface.

This report investigates the cost of capturing CO2 from existing industrial facilities in the Perth region, followed by transportation and offshore storage in one of three sites in southwest Western Australia (one such case is shown in Fig. 1). The objective of this study is to examine the opportunities for CCS within this region. The work was conducted in cooperation with Geoscience Australia and forms part of a larger study on opportunities for CCS in the region. The costs are estimated in real Australian dollars in year 2005 terms and are reported before tax.

The purpose of these preliminary analyses is to estimate the indicative costs of CCS for the area. To do this, the design of a CCS system must be considered in very broad terms. A detailed design for such a system is beyond the scope of the paper.

Assumptions and Methodology

The results are estimated by use of software developed in-house at the University of New South Wales for the CO2CRC. The model performs simple mass- and energy-balance calculations to estimate process-equipment sizes, the number of wells, the size of platforms, and other system parameters. Equipment costs are estimated by use of algorithms developed from rules of thumb, literature data, and vendor quotes. The general methodology has been described elsewhere (Allinson et al. 2003, 2006), and the site-specific assumptions for this study are detailed below.

Economics. Costs of CCS are estimated in AUD per tonne of CO2 avoided. The mass of CO2 avoided is the difference between the amount of CO2 that is emitted without CCS and the amount emitted with CCS. For example, if a power station emits 10 million tonnes of CO2 per year without CCS and only 2 million tonnes of CO2 with CCS, then the mass of CO2 avoided is 8 million tonnes per year (Mt/a). It is assumed in these estimates that the reference plant is the same power station that hosts the CCS process.

Costs are estimated using a real discount rate of 7%, with a construction period of 2 years and a project life of 25 years. The capital costs are phased, 40% in the first year and 60% in the second year. The process is assumed to operate 7,446 hours per year out of the possible total of 8,760 hours, representing a load factor of 85%.
It is further assumed that the energy used in the CCS process is purchased from a newly built external power source that also incorporates CCS. The power source is assumed to be a 1,500-MW natural-gas combined cycle with capture and storage. The cost of electricity purchased from this source is AUD 55/MW-h, and the power source emits CO2 at a rate of 0.05 million tonnes for every megawatt-hour of power generated.

© 2007. Society of Petroleum Engineers

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History

• Original manuscript received: 5 February 2007
• Revised manuscript received: 12 April 2007
• Manuscript approved: 17 April 2007
• Version of record: 20 September 2007