MWDPlanet’s Wireless Downhole Monitoring Tool Used for Geothermal Plug and Abandonment Operations with Coiled Tubing

Cementing geothermal wells requires careful temperature management. When the static water column inside the casing heats up excessively, premature cement setting (“flash setting”) can occur, jeopardizing the operation and risking stuck pipe or incomplete sealing. Conventional wireline or memory tools can measure temperature, but they require multiple trips in and out of the hole, delaying operations and increasing costs.

E-Coil systems could, in theory, provide real-time feedback during cement placement, but their complexity and cost—including the need for specialized reels, cables, and surface equipment—made them impractical for this application. The operator sought a simpler, lower-cost solution capable of providing live temperature and pressure data without the need for wired telemetry.

The project team integrated a Tysk EM transmitter into a 2-7/8” coiled tubing BHA. The system transmitted pressure and temperature data via low-frequency electromagnetic waves that propagated through the formation and casing to surface receivers. Unlike conventional EM transmitters, which often lose signal in casing, the Tysk system uses a patented hybrid H-bridge design that enables continuous data transmission—even within steel casing.

To withstand geothermal conditions, the EM tool was equipped with a high-temperature-rated battery pack and pressure housings rated for harsh environments. The tool’s compact form factor required custom adaptation to fit within the narrow annular space available in the CT string while maintaining hydraulic compatibility for pumping operations.

At the wellsite, setup was straightforward. Ground stakes were installed to serve as antennas for the surface receiver—one placed near the wellhead (on the BOP) and another positioned away from electrical noise sources to reduce interference. The impedance between these two antennas was fine-tuned in the field to achieve optimal signal clarity.

Figure 2.  Location of the second antenna, about 100m away from the wellhead. Photo courtesy of Western Energy.

The 12-foot-long assembled tool was handled using a telehandler and lifting sub to safely connect it to the CT string. Prior hydraulic modeling confirmed that the pressure drop across the tool would be acceptable during cement and water pumping, and field yard testing validated those models, showing lower-than-expected pressure loss.

During operations, the EM system transmitted continuous real-time temperature readings as cooling water circulated downhole. This allowed the surface team to confirm when the wellbore reached safe temperature levels before pumping the cement slurry. The real-time feedback provided the confidence to proceed without overcooling or unnecessary circulation time.