Cements, steels and microbes: CSIRO study improves community understanding of CSG well construction

The project was initiated in response to community concerns about wells and well integrity, and conducted through CSIRO’s Gas Industry Social and Environmental Research Alliance (GISERA). The final project report provides clear written descriptions of the materials used to case and cement coal seam gas (CSG) wells in the Surat and Bowen basins in Queensland.

Additionally, researchers conducted a desktop study to gather data on the type of microbes that occur in subsurface environments of south east Queensland, and explored the capability of those microbes to interact with metal casings or cements used in CSG well construction.

The number of CSG wells in Queensland is expected to reach 22,000 by 2050. Understanding any potential risks associated with gas development activities requires detailed knowledge of CSG well integrity – and that integrity is reliant in part on the performance of casing and cementing materials used in completion and decommissioning.

Detailed information on each CSG well drilled is recorded in a Well Completion Report (WCR) prepared by the operating company and submitted to the Queensland Government. However, WCRs incorporate considerable technical detail, and the information contained within them is not readily accessible or understood by community members.

For this study, CSIRO researchers reviewed WCRs for 131 randomly selected wells and extracted data about the casing and cementing materials used in their construction. Their findings are presented in the project report in a way that makes the data accessible to any interested members of the community, rather than solely to expert audiences or industry specialists.

The microbial desktop study revealed that the most well-studied subsurface microbial communities were for hydrocarbon reservoirs and that significant knowledge gaps exist, especially in aquifers for domestic and agricultural use. In addition, there are no data on microbes that form biofilms, which can promote the microbial activity that impacts the performance of materials used in CSG wells.

Analyses of data related to water from coal resources of the Surat and Bowen basins indicated that microbes present have the genetic capacity to produce sulphides, which can be deleterious to CSG well and other infrastructure. It should be noted, however, that waters in the Surat and Bowen basins are deficient both in the macronutrients required for microbial activity (particularly phosphorus) and in the forms of sulphur required for the production of sulphides. This would tend to limit microbial activity.

As a result of the significant knowledge gaps identified by the desktop study, a new GISERA project to collect and analyse water samples from aquifers and infrastructure in the region has now begun. The results of this second study will provide valuable insights into the potential hazards microbes pose for infrastructure. 

Read more about this project: Review of cements, steels and microbial activity for Qld CSG wells.

Watch our animation on Microbial activity in the subsurface.

Learn about other GISERA research in Queensland.