OCTIO Gravitude has surveyed this summer the Snøhvit, Albatross and Askeladd gas fields, operated by Equinor Energy AS. The survey featured the gWatch technology, the new generation of seabed gravity and subsidence instrumentation. The operation lasted for less than three weeks and was performed very efficiently and with no HSE incidents.

In this type of surveys, the quality of both gravity and seafloor depth data is evaluated by comparing the results of repeated measurements performed at the same locations. The so-called repeatability parameter indicates how similar such independent measurements are to each other, and provides a robust means to evaluate the precision of individual measurements. At the end of this year’s survey at Snøhvit, Albatross and Askeladd, the repeatability has been measured to be 0.8 µGal and 2.2 mm respectively for gravity and depth data. These are both excellent results. In particular, the repeatability in gravity is the best on an offshore survey to date, even when compared with results after final processing and reporting in the previous cases.

Gravimetry and subsidence measurements at the seabed are used by oil companies to monitor fluid movements and rock deformation within hydrocarbon reservoirs. This information contributes to a more efficient reservoir management, and therefore to make hydrocarbon production more efficient in terms of cost and environmental impact. The cost of this type of surveys is significantly lower than that of the more spread 4D seismic technology. An improved quality in the measurement of gravity makes these benefits available for a wider variety of fields and allows for taking measures aimed at optimizing the production at earlier stages of the hydrocarbon field lifetime.

License partner companies at Snøhvit, Albatross and Askeladd are Equinor Energy AS (operator), Petoro AS, Total E&P Norge AS, Neptune Energy Norge AS and DEA Norge AS.

Equinor Energy AS has recently awarded OCTIO Gravitude an exclusive contract for gravimetric monitoring on the Norwegian continental shelf. The contract has an initial duration of five years, with an option of extension to an additional four years.

The operation was performed from the survey and light construction vessel Topaz Tiamat operated by MMT and Reach Subsea.

gWatch2020

gWatch instrumentation mounted on the ROV during the survey at Snøhvit, Albatross and Askeladd in 2019

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