Offshore field trial application of low-frequency passive microseismic technology in the North Sea for exploration, appraisal and development of hydrocarbon deposits

Abstract

The recent downturn in the industry has led to a focus on maximizing economic recovery and low-frequency seismic sounding (LFS) technology has the potential to delineate oil and gas reservoirs to derisk drilling decisions and shorten the appraisal and development timeframe. The change in the low-frequency range of natural microseismic background noise is due to the mechanics of fluid saturated, fractured and porous media, with oil and gas reservoirs having a high-velocity dispersion and attenuation at low frequencies. Here, we demonstrate the offshore deployment, acquisition and applicability of LFS to delineate hydrocarbon deposits in the North Sea. The spectra of the dry and oil-bearing sections of the surveyed area is observed in the frequency range of 0.6–1.9 Hz, while noise interference in the form of Scholte waves is also observed in the low-frequency range of 2Hz. We developed new filtering procedures to remove interference and exclusively select vertically directed P waves from the recorded signal. The result is a map of correlation coefficients which characterize the absence and presence of hydrocarbons as a probability map of hydrocarbon. The offshore trial has confirmed the application of the LFS technology highlighting areas that can be improved to deliver optimal results.