Quantitative estimates of oil-seepage rates from satellite imagery with implications for oil generation and migration rates

A new approach to quantifying oil fluxes from natural seafloor seepage sites based on the dynamic characteristics of floating oil slicks is presented. It enables rapid analysis of interpreted satellite imagery and permits large datasets to be analyzed. The method uses the drift path of the oil on water surface, termed the “centerline” of the slick, along with average current and wind speeds to estimate the age of seepage slicks. The results of the CL (centerline) method compare favorably with the hindcast modeling approach which requires time-resolved analysis of wind and current for each slick. The CL method yields an average flux estimate within the range of the flux documented by on-bottom capture for a seafloor oil pollution source. A survey of published flux estimates using a variety of techniques reveals a wide range with on-bottom estimates (0.08–12 ml/s) generally lower than estimates from slicks (1.6–125 ml/s). Determination of fluxes from three seepage sites in the Gulf of Mexico (GC600, Bush Hill, and TYK) reveals a wide range in seepage rates from 2.4 to 52.9 ml/s and flux distributions. Comparison of the observed fluxes from seeps with potential fluxes from a source region can be used to constrain source rock parameters (e.g., thickness, richness, area) and to understand the cumulative oil supply represented by seeps over geologic time scales. •New method allows rapid estimation of instantaneous flux from satellite imagery.•Accuracy of method demonstrated against an oil capture system.•Seepage sites show significant variations in flux.•Estimated seepage fluxes indicate large oil volumes are released over time.