Elements of Successful Thermogenic Shale Gas Pays
Tobey, Mark H.1, Thomas M. Smagala2, and David E. Schmude3
1Organic geochemistry consultant, Castle Rock, CO
2EnCana Oil & Gas (USA), Inc, Denver, CO
3EnCana Oil & Gas (USA) Inc, Denver, CO
Finding the keys to unlock shale gas plays requires thorough investigation, experimentation, and persistence. These plays are as varied as “conventional” plays in terms of the nature of the “reservoir” and the completion practices which tap those “reservoirs.” Therefore, there is no one formula of attributes which guarantees success. Designing a effective extraction strategy will depend upon the specific attributes of the play, and the application of key learnings from other successful plays. There are common elements to successful shale gas plays, however, which can be evaluated up front to assess their potential and to reduce exploration risk. The hydrocarbon generative potential of the shale depends upon its organic enrichment and kerogen composition. The degree of thermal maturation, coupled with the kerogen type, quantifies the risk for hydrocarbon liquids, the potential for liquid-to-gas cracking, or the risk for hydrocarbon destruction. The shale porosity (rock matrix and total matrix which includes fracture density), organic enrichment, reservoir temperature / pressure, and shale thickness are parameters which contribute to the maximum gas storage capacity of the shale – original gas in place. The potential for remaining gas in place depends upon the timing of maturation, burial / tectonic history, and other factors. Gas delivery potential depends upon shale fabric, permeability, rock mechanical properties, stress environment, and reservoir pressure – and using that information to formulate the key to an effective completion. Individual plays also include additional components relevant to that play. These elements will be reviewed and put into context with productive shale gas plays.
AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah