Investigation of the thermal history of the Delaware Basin (West Texas, USA) using carbonate clumped isotope thermometry
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AbstractWe utilized carbonate clumped isotope thermometry to explore the thermal history of the Delaware Basin, West Texas, USA. Carbonate wellbore cuttings from five oil/gas wells across the basin yielded clumped isotope temperatures (T(47)) ranging from 27C to 307C, interpreted to reflect a combination of initial precipitation/recrystallization temperature and solidstate CO bond reordering during burial. Dolomite samples generally record lower apparent T(47)s than calcite, reflecting greater resistance to reordering in dolomite. In all five wells, clumped isotope temperatures exceed modern downhole temperature measurements, indicating higher heat flow in the past. Using modelled burial curves based on sedimentological history, we created unique timetemperature histories by linearly applying a geothermal gradient. Applying two different thermal history reordering models, we modelled the extent of solidstate CO bond reordering to iteratively find the timeaveraged bestfit geothermal gradients for each of the five wells. Results of this modelling suggest that the shallower, southwestern portion of the study area experienced higher geothermal gradients throughout the sediment history (~45C/km) than did the deeper, southeastern portion (~32C/km), with the northern portion experiencing intermediate geothermal gradients (~3538C/km). This trend is in agreement with the observed gas/oil ratios of the Delaware Basin, increasing from east to west. Furthermore, our clumped isotope temperatures agree well with previously published vitrinite reflectance data, confirming previous observations and demonstrating the utility of carbonate clumped isotope thermometry to reconstruct basin thermal histories.
