Distributed acoustic sensing system operating at Atlantis

Aug. 11, 2021
Silixa has installed its distributed acoustic sensing system, Carina Subsea 4D, on bp’s Atlantis Phase 3 development in the deepwater US Gulf of Mexico.

Offshore staff

LONDONSilixa has installed its fiber optic distributed acoustic sensing (DAS) system, Carina Subsea 4D, on bp’s Atlantis Phase 3 development in the deepwater US Gulf of Mexico.

Atlantis Phase 3 involves a new subsea production system with eight new wells tied into the Atlantis semisubmersible production platform, 150 mi (241 km) south of New Orleans.

The engineered fiber optic system is said to enable high-definition seismic data acquisition along the entire subsea wellbore. This allows seismic acquisitions at a lower cost, enabling better reservoir management.

The Carina Subsea system has been installed in two wells, and installation is continuing over the rest of the field. A zero offset DAS VSP was acquired to validate coupling and signal to noise characteristics and showed excellent data quality, the company said. Subsequent production noise recordings showed little impact.

This is the world’s first permanent in well seismic acquisition system for subsea wells, the company claimed. It can operate independently or provide complementary data to ocean bottom node surveys. It is especially effective for reservoirs that are traditionally difficult to image using surface seismic such as presalt reservoirs or those beneath gas clouds.

The Silixa system is said to deliver 100 times improvement in signal-to-noise ratio compared to DAS systems using standard fibers. It features Constellation fiber engineered with brighter backscatter centers along its length to capture and reflect 100 times more light back to the interrogator without introducing significant loss to the forward propagating laser pulses. This makes this new technology ideal for subsea tieback applications where high optical losses from subsea connectors have previously prevented DAS deployment, the company said. It also does not require complex electronics to be placed on the seafloor.

Garth Naldrett, Silixa’s chief product officer, said: “Until now, subsea fields had to rely on sparse data acquisition due to the risk and cost of acquisition. Bringing our engineered distributed fiber optic sensing technology to subsea wells and allowing the same data acquisition we have already enabled on land and platform wells will have a tremendous impact on the industry.”

Sebastien Soulas, Senior Borehole Seismic Advisor at LYTT, said: “The first subsea DAS VSP field recording has confirmed and shown excellent data quality with high fidelity measurements and signal-to-noise-ratio in the expected downhole array aperture for borehole seismic imaging in actively producing wellbores.”