The Application of Hydrocarbon System and Play Fairway Analysis for Unconventional Resource Plays: The Case for Shale Gas Reserves in New York’s Ordovician Utica Shale

Leonard, Jay E.¹, Donald Clark¹, Robert J. Coskey¹, Nancy B. Hunter¹, Charles P. James², China O. Leonard¹, Gary G. Lash³, Veit J. Matt¹ (1) Platte River Associates, Inc, Boulder, CO (2) Platte River Associates, Inc, Boulder, (3) SUNY Fredonia, Fredonia, NY

For the exploration of fractured shale gas plays, it is desirable to identify “sweet spots” or areas that could be drilled early to front load the economics. In the Ordovician Utica shale gas play, critical factors such as hydrocarbon generation and expulsion timing coupled with fracture timing defines such “sweet spots”. These factors, combined with reservoir and seal, asses the presence and effectiveness of the play and the play fairway.

Stratigraphy in New York ranges from the late Pre-Cambrian to the late Devonian with scattered Carboniferous and neither Mesozoic nor Tertiary section preserved. Structure, isopach, lithology, and geochemical maps have been integrated with erosional thickness, heat flow, geothermal gradient, and paleo latitude histories to investigate the medial Ordovician shale gas system.

Simulations indicate that the dry gas window is reached in large areas of New York before the Alleghanian regional uplift that resulted in the present day surface unconformity. Practically all organic matter was completely converted across the state by medial Permian. The volume of gas generated in the source rock is primarily a function of initial TOC and the effective source rock thickness. In addition, gas retained is also a function of source rock porosity, fluid pressures, expulsion, and episodic fracture timing and direction.

The calculated generated gas and retained gas maps highlight some “sweet spots“ throughout eastern New York and can be illustrated as common risk segment and P50 maps. These predicted patterns have been compared to the gas shows reported in wells.