Geothermal energy plants have traditionally been limited to the edges of the tectonic plates but recent advances in Enhanced Geothermal Systems (EGS) show promise to open up a much greater geographical range. EGS wells in these expanded areas tend to be more complex than traditional wells and therefore require more active monitoring. It is agreed upon by industry experts that improved subsurface visualization is critical to successful and reliable EGS operations.
Fiber optic-based Distributed Temperature Sensing (DTS) technology enables real-time subsurface visualization and understanding of fracture distribution during both fracturing operations and production. DTS technology has proven to be valuable in subsurface monitoring through widespread use in the oil & gas industry. DTS systems have been routinely installed in thermally active, complex wellbores since the mid-1990s.
Subsurface conditions in geothermal wells are very similar to subsurface conditions in heavy oil applications where high temperature steam is injected into tar sand reservoirs. SensorTran Distributed Temperature Sensing (DTS) systems can provide monitoring for a variety of geothermal applications. Following are some of the ways that geothermal energy producers and researchers can use DTS data to visualize subsurface conditions.
Estimate the production potential in a new well by measuring the distributed temperature and point pressure
Determine connectivity between different wells by running pressure build-up tests with pressure monitoring in multiple wells
Monitor fracture development during stimulation and fracturing.
Monitor chemical injection during or after fracturing job
Monitor chemical clean-up of the well to wash out mud-cake from the drilling process
Monitor scale build-up and subsurface chemical clean-up of scale
Scale will act as an insulating layer and change the temperature profile over depth
Monitor water injection
DTS traces will highlight which zones and fractures take the injected fluid.
Monitor producer wells to identify which zones and fractures produce fluids
Detect short circuiting so mitigation options can be planned
Monitor integrity of casing and tubing for leaks to avoid contaminating ground water and subsurface aquifers. Additional DTS channels/sensing cables can also monitor surface piping at minimal additional cost.
An additional benefit to having DTS onsite is that it can also be shared for other applications - such as power cable monitoring for hot spot detection and overheating conditions, and to maximize the available capacity of the monitored circuits while minimizing the risk of cable damage.