Published: 08/19/2021
Published: 08/19/2021
In drilling a new well for the geological disposal of high-level, long-lived waste, the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (NIRAS) needed to thoroughly characterize the various clay layers. The required data included a checkshot seismic survey for velocity model calibration.
The Optiq Seismic solution brings new efficiencies to borehole seismic applications. The solution’s optical interrogator unit at surface is connected to any optical-fiber cable deployed in a well, from hybrid wireline logging cable to production tubing with fiber installed or optical fiber permanently cemented behind casing.
Because the Optiq Seismic solution makes every logging run or fiber installation an opportunity for seismic data acquisition, it significantly improves the efficiency of borehole seismic operations while lowering the cost. No longer is time required for rigging up and down and deploying conventional borehole seismic tools because the solution is simply connected to the fiber at surface and records seismic data in conjunction with other stationary logging services or on its own. A full well profile is recorded for each shot. The full-aperture measurements acquired are suitable for checkshots for seismic calibration or time-lapse imaging over the life of the field.
The NIRAS well was the first commercial deployment of the Optiq Seismic solution on Optiq TuffLINE torque-balanced fiber-optic wireline conveyance, which is a seven-conductor heptacable with two added single-mode optical fibers.
The Optiq TuffLINE conveyance performed well with maximum tension during the logging runs recorded at 3,000 lbf. The Optiq Seismic solution recorded seismic data on each of the four runs while the logging tools were near the bottom of the well. The seismic surveys were recorded transparently along with data acquisition by the FMI fullbore formation microimager, Platform Express integrated wireline logging tool, CMR-Plus combinable magnetic resonance tool, ECS elemental capture spectroscopy sonde, and a borehole seismic imager tool. Comparison shows that the main characteristics of the seismic waves on the imager’s survey are matched by the Optiq Seismic solution’s survey, making it highly usable as checkshot data for time picking.
The Optiq Seismic solution acquired highly usable checkshot data that matches the conventional borehole seismic survey but with only 10% of the shots required and at a 98% reduction in acquisition time.
More importantly, while the borehole imager required 200 shots to conduct the survey, the Optiq Seismic solution acquired seismic data with only 20 shots over the four runs. Similar efficiencies were achieved timewise: The conventional survey took about 6 hours 30 minutes for entire operation including rig-up, running to stations, 3½ hours for recording data, pulling out, and rig-down, whereas the good-quality Optiq Seismic solution survey took 3½ minutes, without needing a separate dedicated run.
Challenge: Efficiently acquire a borehole seismic survey along with a full suite of logs to characterize clay layers.
Solution: Deploy Optiq Seismic fiber-optic borehole seismic solution—leveraging distributed acoustic sensing (DAS) technology and Optiq TuffLINE torque-balanced fiber-optic wireline conveyance—to efficiently record data during conventional logging runs.
Results: Acquired good-quality checkshot data in 3½ minutes per well logging run instead of 3½ hours to conduct a dedicated conventional borehole seismic survey requiring 200 shots.
