Abstract

In the 4850 ft deep Sanford Underground Research Facility (SURF) in South Dakota, we analyzed the microbial communities in the injected and produced water by high-throughput sequencing to explore the microbial community similarities across boreholes during an interwell flow scenario frequently encountered in reservoir development. Despite the rapid tracer breakthrough tracer recoveries (~30%) in all tracer tests and the cumulatively >100,000 L of exogenous water (carrying exogenous microbes) injected into the reservoir, the overall structure of produced-fluid microbiome did not increasingly resemble that of the injectate. However, producers with better connectivity with the injector (based on tracer test results) did have more sequence variants that overlapped with those in the injectate. We identified possible drivers behind our observations and verified the practicality of repeated microbial sampling in the context of reservoir characterization and long-term monitoring. We highlight that time-series injector-producer microbial profiling could provide insights on the evolution of relative connectivities across different producers with a given injector, and that the associated logistical needs may be comparable or even less than that of classic tracer tests. This work was part of the PhD research of Yuran Zhang.

Bio

Roland N. Horne is the Thomas Davis Barrow Professor of Earth Sciences and Professor of Energy Science and Engineering at Stanford University, and Director of the Stanford Geothermal Program. He was formerly the Chairman of the Department of Petroleum Engineering at Stanford from 1995 to 2006.  He is best known for his work in well test interpretation, production optimization, and tracer analysis of fractured geothermal reservoirs.  So far in his academic career he has supervised the graduate research of 60 PhD and 120 MS students, including about 60 in geothermal topics. He served on the International Geothermal Association (IGA) Board 1998-2001, 2001-2004, and 2007-2010, and was the 2010-2013 President of IGA.  He was Technical Program Chairman of the World Geothermal Congress 2005 in Turkey, 2010 in Bali, Melbourne in 2015, and again in Iceland in 2020-2021. 

Roland is a member of the US National Academy of Engineering and an Honorary Member of the Society of Petroleum Engineers.  He is also a Fellow of the School of Engineering, University of Tokyo and an Honorary Professor of China University of Petroleum – East China.