Combining Surface Geochemical Surveys and Downhole Geochemical Logging for Mapping Hydrocarbons in the Utica Shale
Given the heterogeneity of shale plays it is important to identify hydrocarbon variability in a 3-dimensional sense. To capture this 3-dimensional hydrocarbon picture both Amplified Geochemical Imaging and Amplified Geochemical Logging were used in the Utica shale play. A surface geochemical survey was used to generate a 2-D hydrocarbon map over the area for both gas and liquid phase hydrocarbons. The surface geochemical survey incorporated a passive sampler containing a specially engineered hydrophobic adsorbent encased in a layer of microporous expanded polytetrafluoroethylene (ePTFE) and monitored hydrocarbons from C2 – C20. The resulting data was used to: • identify three distinct gas hydrocarbon signatures • identify a liquid hydrocarbon signature across the field • differentiate between economic and noneconomic gas areas in the play • differentiate and map light and heavy hydrocarbon signatures throughout the area • image hydrocarbon anomalies aligned with surface lineaments indicating hydrocarbon filled fractures In addition to the surface geochemical survey, Downhole Geochemical Logging was also employed on a well drilled after the surface survey. Downhole Geochemical Logging of the cutting samples provided the ability to directly characterize the composition of hydrocarbons vertically through the prospect section. The methodology measured a broad compound range from C2 to C20 and had a 1,000 time greater sensitivity than traditional methods. As a result, the data was used to: • detect by-passed pays • infer compartmentalization • infer from which zones the economic and noneconomic gases in the play may have originated • infer from which depths and formations the liquid hydrocarbons may have originated The combination of the surface survey and the Downhole Geochemical Logging provided a 3-D picture of the hydrocarbons in this play. As such, the data indicated that the ubiquitous noneconomic gas may have been coming from the Utica formation. The survey also allowed the mapping of areas where the economic gas could be found and implied that the economic gas had a unique source and was in fact originating from the deeper Trenton formation and accumulating in natural fractures above. Additional the Downhole Geochemical Logging inferred that the liquid hydrocarbon locations mapped by the surface survey were most likely coming from the Upper and Lower Queenston formation and that there was mostly likely a seal between the two sections.
AAPG Datapages/Search and Discovery Article #90195 © 2014 Eastern Section Meeting, London, Ontario, Canada, September 27-30, 2014