A Monitoring and Verification Plan for The Otway CO2 Pilot Project

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 19202, "Developing a Monitoring and Verification Plan With Reference to the Australian Otway CO2 Pilot Project," by Kevin Dodds, SPE, CSIRO, and Sandeep Sharma, SPE, Schlumberger, originally prepared for the 2008 Offshore Technology Conference, Houston, 5–8 May. The paper has not been peer reviewed. The Australian Cooperative Research Center for Greenhouse Gas Technologies (CO2CRC) currently is injecting 100,000 tons of CO2 in a large-scale test of storage technology in a pilot project in southeastern Australia called the CO2CRC Otway Basin Project (Otway). The Otway basin with its natural CO2 accumulations and many depleted gas fields, offers an appropriate site for such a pilot project. An 80% CO2 stream is produced from a well near the depleted gas reservoir used for storage. The goal of this pilot project is to demonstrate that CO2 can be transported and stored underground safely and its behavior tracked and monitored. Introduction The commercial oil and gas leases in the Otway basin in Victoria, selected for the pilot project, are in an undeveloped CO2 field (Buttress), which is the source of CO2, and a depleted gas reservoir (Naylor), which is the injection/containment site. The extracted and separated CO2 stream is transported by pipeline and injected into a new well (CRC-1), drilled downdip of the existing well, and into the depleted Waarre reservoir in the Naylor field at a depth of approximately 2000 m. The existing shut-in production well (Naylor-1) is being used as the monitoring well. Characterization of the site has involved the collection of a large quantity of geological, geophysical, and other regionally relevant data and the construction of static and dynamic reservoir models. The regional formations provide an excellent porous and permeable geological formation that provides a highly suitable reservoir system for CO2 storage. In summary, the site-assessment results, indicating that the Waarre formation is a suitable site for CO2 storage, conclude the following key attributes of the site. There are no significant faults evident in the wells at the Waarre C level; there is a fairly uniform Waarre C thickness. The local and regional seals have contained a number of natural CO2 accumulations in the eastern Otway basin over geological time. The storage reservoir has sufficient porosity and permeability to be able to accept the injected CO2 at forecast rates. The injected CO2 is predicted to move updip from the injector location and migrate to the crest of the fault block and accumulate below the residual-methane gas cap in the vicinity of the existing Naylor-1 well. The selected site has the major advantage of being onshore rather than offshore, allowing the project research teams to test and further refine the monitoring and verification techniques at a more accessible location.