Integrated Technology for Deep Boreholes: Modular Borehole Monitoring

Abstract:

Understanding the impacts caused by engineered activities in the deep subsurface, such as waste disposal, necessitates a comprehensive borehole monitoring strategy. Similarly, characterization of continental subsurface properties for scientific understanding requires optimal use of deep boreholes. While surface-based and other remote geophysical methods can provide information on the structure, lithology and properties of subsurface formations, the scale of investigation is typically large and some properties require direct measurement, e.g. verification of the geochemical conditions. Validation of remote sensing data, along with increasing data spatial resolution, requires measurements from boreholes that penetrate the formations of interest. Unfortunately, the high cost of drilling deep wellbores and deploying instrumentation systems constrains the number of dedicated monitoring borings as well as limits the technologies that can be incorporated in a borehole completion. We recently completed a Modular Borehole Monitoring (MBM) Program to develop a robust suite of well-based tools optimized for subsurface monitoring of CO2 injected into sedimentary basins. These tools included seismic sensing, temperature sensing, in-situ fluid sampling and in-situ fluid pressure measurement. as part of a comprehensive well-based monitoring program. Characterization of crystalline rock requires a similar suite of tools. A MBM system should have enough flexibility to be easily reconfigured for various borehole geometries and geologies. The MBM Program sought to provide operators with a turn-key, fully engineered design that incorporated key technologies, could function over the long time-span necessary for monitoring engineered activities, and meet industry acceptable risk profiles for deep-well installations. We will present design information and monitoring results from previous installations and discuss needs for crystalline rock monitoring.