The Role of Advanced Geophysical Monitoring in Improved Resource Expansion and Make-up Drilling Strategy

Abstract

Geophysical monitoring tools such as micro-gravity, micro-seismicity and ground deformation provide geothermal reservoir modellers and resource managers with improved information on reservoir behaviour, especially when fields are under development. As-a- consequence, better production and reinjection strategies can be tested, and future operational scenarios can be fine-tuned to improve utilisation sustainability. Advanced and novel monitoring methods also help improve forecasts of near-surface environmental effects and monitor the results of mitigation efforts undertaken through adaptive reservoir management. This paper reviews current knowledge gained from such methods and discusses the potential for using this knowledge to help develop better strategies for resource expansion and make-up drilling strategy. Recent advances in research into continuous monitoring techniques using geophysical methods include the use of: micro-gravity, seismic-tomography, ground-deformation, repeat resistivity and various forms of remote-sensing. Knowledge has also been gained from reviewing the decades of monitoring of physical changes that have occurred in conventional geothermal projects around the world. To make full use of this information, and to accurately simulate geophysical property changes resulting from reservoir fluid and heat transport, advanced reservoir modelling benefits from coupled thermal, hydraulic, mechanical, and chemical (THMC) processes. Consequently, rock properties used in reservoir simulation, such as permeability and porosity, are variables rather than constants over the lifetime of a reservoir. The benefits of this improved understanding of reservoir processes is an improvement in conceptual models of geothermal resources and therefore better projections of their sustainable energy extraction capacity and recharge parameters. This knowledge is also applied to exploration and expansion strategies to provide better drilling targets and improved production-reinjection strategies for well-established, but aging, geothermal developments.