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

Abstract

. (2017) 'Determining uid migration and isolation times in multiphase crustal domains using noble gases. ', Geology., 45 (9). pp. 775-778. Further information on publisher's website:https://doi.org/10.1130/G38900.1Publisher's copyright statement: c 2017 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTGeochemical characteristics in subsurface fluid systems provide a wealth of information about fluid sources, migration, and storage conditions. Determining the extent of fluid interaction (aquifer-hydrocarbon connectivity) is important for oil and gas production and waste storage applications, but is not tractable using traditional seismic methods. Furthermore, the residence time of fluids is critical in such systems and can vary from tens of thousands to billions of years. Our understanding of the transport length scales in multiphase systems, while equally important, is more limited. Noble gas data from the Rotliegend natural gas field, northern Germany, are used here to determine the length scale and isolation age of the combined water-gas system. We show that geologically bound volume estimates (i.e., gas to water volume ratios) match closed-system noble gas model predictions, suggesting that the Rotliegend system has remained isolated as a closed system since hydrocarbon formation. Radiogenic helium data show that fluid isolation occurred 63-129 m.y. after rock and/or groundwater deposition (ca. 300 Ma), which is consistent with known hydrocarbon generation from 250 to 140 Ma, thus corroborating long-term geologic isolation. It is critical that we have the ability to distinguish between fluid systems that, despite phase separation, have remained closed to fluid loss from those that have lost oil or gas phases. These findings are the first to demonstrate that such systems remain isolated and fully gas retentive on time scales >100 m.y. over >10 km length scales, and have broad implications for saline aquifer CO 2 disposal site viability and hydrocarbon resource prediction, which both require an understanding of the length and time scales of crustal fluid transport pathways.

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

“…In order to assess the extent of interaction that an oil phase has had with ASW, the original noble gas inventory of ASW in the subsurface is first constrained. As with previous solubility models (e.g., Ballentine et al, ; Barry et al, , , ; Gilfillan et al, ; Zhou et al, ), it is assumed that air‐derived noble gases ( 20 Ne, 36 Ar, 84 Kr, and 132 Xe) are originally input into the subsurface dissolved in water during aquifer recharge and/or during burial of air saturated pore fluids and subsequently isolated from further atmospheric inputs. Additionally, we assume that air‐derived light noble gases (i.e., 20 Ne and 36 Ar) do not have any significant subsurface source, unlike radiogenic and/or mantle‐derived noble gas isotopes.…”

“…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.…”

“…The concentration of radiogenic nuclides can be predicted by estimating flux rates in open fluid systems (Castro, Goblet, et al, ; Castro, Jambon, et al, ; Torgersen, ; Torgersen & Clarke, ; Torgersen & Ivey, ; Zhou & Ballentine, ). In contrast, in closed systems where fluids are trapped and stored over geologic timescales, the rate of accumulation is critical for calculating isolation estimates (Ballentine et al, ; Barry et al, ; Cook et al, ; Holland et al, ; Solomon et al, ; Tolstikhin et al, , ; Warr et al, ). In such closed systems, parent radionuclide concentrations in reservoir rocks are critical, as is the efficiency of release (Barry et al, , ; Darrah et al, ; Hunt et al, ; Lowenstern et al, ; Tolstikhin et al, , ) from the source rock into the fluid phase.…”

“…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.…”

A Novel Method for the Extraction, Purification, and Characterization of Noble Gases in Produced Fluids

“…Terrestrial reservoirs of noble gases (atmospheric, crustal, and mantle) have well-characterized and diagnostic isotopic and abundance compositions, meaning fluid contributions from each reservoir can be easily differentiated. Previous studies have successfully used noble gas isotopes and abundances to quantify water-oil-gas interactions in both conventional and unconventional hydrocarbon systems and those effected by EOR techniques (Ballentine et al, 1991(Ballentine et al, , 1996(Ballentine et al, , 2002Barry et al, 2016Barry et al, , 2017Barry, Kulongoski, et al, 2018;Barry, Lawson, et al, 2018;Byrne et al, 2018aByrne et al, , 2018bDarrah et al, 2014Darrah et al, , 2015Györe et al, 2017Györe et al, , 2015Prinzhofer, 2013). These studies have primarily focused on natural gas systems, although some have specifically investigated oil systems (e.g., Ballentine et al, 1996;Györe et al, 2017), unconventional systems (e.g., Byrne et al, 2018b;Zhou et al, 2005) and multi-component systems (Barry, Lawson, et al, 2018).…”