Noble gases solubility models of hydrocarbon charge mechanism in the Sleipner Vest gas field

Abstract

Noble gases are chemically inert and variably soluble in crustal fluids. They are primarily introduced into hydrocarbon reservoirs through exchange with formation waters, and can be used to assess migration pathways and mechanisms, as well as reservoir storage conditions. Of particular interest is the role groundwater plays in hydrocarbon transport, which is reflected in hydrocarbon-water volume ratios. Here, we present compositional, stable isotope and noble gas isotope and abundance data from the Sleipner Vest field, in the Norwegian North Sea.Sleipner Vest gases are generated from primary cracking of kerogen and the thermal cracking of oil. Gas was emplaced into the Sleipner Vest from the south and subsequently migrated to the east, filling and spilling into the Sleipner Ost fields. Gases principally consist of hydrocarbons (83-93%), CO 2 (5.4-15.3%) and N 2 (0.6-0.9%), as well as trace concentrations of noble gases. Helium isotopes ( 3He/

Determining fluid migration and isolation times in multiphase crustal domains using noble gases

“…Using these well-defined controls on noble gas concentrations in groundwater, it is possible to calculate the extent and character (i.e., fractionation) of noble gas distribution between any gas or oil phase that interacts with water, using estimates of subsurface system pressure, temperature, and salinity. These data further preserve details about the hydrocarbon/water volume ratio and whether the system is open to gas loss (Ballentine et al, 1996;Zhou et al, 2005;Barry et al, 2016). Radiogenic noble gases, which are isotopically distinct from the air-derived noble gases dissolved in water, accumulate in groundwater systems and can be used to investigate mean fluid residence (e.g., Torgersen, 2010;Aggarwal et al, 2014).…”

“…This process is referred to as gas stripping of noble gases. With knowledge of the initial noble gas composition of the air-saturated water (determined by groundwater recharge conditions) and measured noble gas concentrations in the hydrocarbon phase, it is possible to calculate the extent of hydrocarbon-water interaction and therefore predict a volumetric gas/water (G/W) ratio (e.g., Barry et al, 2016).…”

Geochemical applications in petroleum systems analysis: new constraints and the power of integration

“…Instead, they provide information on the physical interaction and mixing of fluids in the subsurface, and can yield constraints on the timescales associated with hydrocarbon storage. Prior applications of noble gas geochemistry focused on the role of groundwater flow in hydrocarbon migration (Zartman et al 1961;Bosch & Mazor 1988;Ballentine et al 1991;Barry et al 2016) and cementation (Ballentine et al 1996). Recent advances in multicollector mass spectrometry now provide increasingly sensitive measurements of noble gases with greater precision.…”

Noble Gases in Deepwater Oils of the U.S. Gulf of Mexico

“…Terrestrial reservoirs (i.e., air‐derived, crustal, and mantle) have diagnostic noble gas isotopic compositions, and therefore, fluids derived from each reservoir can be readily identified. For example, isotopic and abundance compositions of various fluid sources in sedimentary basins can be used to identify and quantify physical exchange mechanisms between water, oil, and gas phases in a hydrocarbon system (Ballentine et al, ; Barry et al, , ; Bosch & Mazor, ; Prinzhofer, ; Zartman et al, ). In air‐saturated water (ASW), noble gases are dissolved at solubility equilibrium.…”

“…In addition, the reservoir fluid phase varies from oil with associated gas in the Genesis, Hoover, and Madison fields to dominantly gas with a small underlying oil phase in the Diana field. We adapt a series of solubility models that were developed to understand two‐phase (gas‐water) systems (Barry et al, , ) and two‐phase oil systems in order to interpret three phase (gas‐oil‐water) systems. These models describe how noble gas concentrations and elemental ratios evolve as (1) ASW interacts with oil and (2) oil reaches gas saturation and forms a gas phase in the subsurface reservoir.…”