--> THE GEOLOGY AND GEOCHEMISTRY OF HELIUM, CO2, AND LOW-BTU HYDROCARBON RESERVOIRS IN THE PERMIAN BASIN

2019 AAPG Annual Convention and Exhibition:

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THE GEOLOGY AND GEOCHEMISTRY OF HELIUM, CO2, AND LOW-BTU HYDROCARBON RESERVOIRS IN THE PERMIAN BASIN

Abstract

As petroleum exploration has expanded to more basins and to greater depths in the crust, the discovery of low-BTU natural gas fields (and/or individual wells), including natural gases rich in CO2, helium, and nitrogen, has become increasingly common. These low-BTU discoveries have important economic implications. Negative economic impacts relate to the effective ‘dilution’ of the proportion of recoverable hydrocarbons, the overestimation of recoverable hydrocarbon volumes, and the need for expensive onsite technologies (e.g., nitrogen or CO2 rejection) to purify hydrocarbon products before delivery to the pipeline. Alternatively, low-BTU discoveries often have their own unique value propositions. For example, carbon dioxide a critical resource for tertiary enhanced oil recovery (EOR) and has played a critical part in revitalized U.S. domestic oil production over the last few decades. Similarly, the recovery of helium from high helium wells is needed to meet dramatic increase in anthropogenic demands for helium in the medical, nanotechnology, and defense industries, especially amid decreasing commitments to the US Strategic Helium Reserve. For these reasons, it has become critical to better characterize the geological context of these previously overlooked low-BTU natural gas deposits in order to develop viable exploration strategies. The principal factors for predicting the discovery of these deposits, in addition to the availability of suitable seals and structural or stratigraphic traps, are establishing the relative timing of natural gas emplacement, the mechanisms and dynamics of fluid migration, and the associated compendium of gas-water-rock interactions that typically reduce the volume of CO2 via trapping and increase the release of helium from minerals in the crust by metamorphism. Herein, we will review the state-of-the-art in gas compositional analysis and geochemistry of established and emerging low-BTU natural gas deposits in the continental US with a focus on low-BTU deposits in the Permian Basin. In combination with other traditional petroleum geology and structural/tectonic analysis, this data will provide a perspective on the search for these increasing economically relevant low-BTU natural gas reserves.