Subnormal Pressure Regimes of the Northern Barents Shelf: Causes and Implications for Hydrocarbon Exploration

Abstract

Summary Underpressure, defined as any pore pressure below the hydrostatic, is relatively underrepresented in literature. In this contribution we document underpressure both onshore Svalbard and in the northern part of the Norwegian Barents Sea. Furthermore we discuss the potential geological processes contributing to the underpressure generation and the implications to petroleum exploration. Underpressure of up to 50 bar is observed onshore Svalbard and in five of the northernmost wells of the Barents Sea, with the former equating to some 50% of hydrostatic pressure at approximately 850 metres depth. Basins, including the study area, where naturally occurring underpressure has been documented share several common geological features; most notably all have undergone recent uplift. Whilst previously documented cases of underpressure have been observed in elevated onshore basins, underpressure on the Barents Shelf occurs below sea level. The combination of detailed onshore well and outcrop observations from Svalbard’s Longyearbyen CO2 lab and outcrops, and numerous offshore exploration wells in the northern Barents sea provide insight into the different potential underpressure forming mechanisms.