RESERVOIR CHARACTERIZATION AND PETROLEUM ASSESSMENT OF AN ACTIVE GAS AND LIQUID CONDENSATE FIELD IN SOUTHWESTERN IDAHO

<span">Preliminary results are presented for a five year reservoir characterization study of Miocene to Pliocene rocks deposited in the western Snake River Plain region of Idaho. This NW-SE-trending intracratonic extensional basin contains gas and liquid condensate resources with seventeen active hydrocarbon wells, six of which are in production. Basin formation persisted between 5-15 Ma with major structurally induced down warping between 9-11 Ma (Wood and Clemens, 2002, IGS Bulletin, p. 69-103). From oldest to youngest the Payette, Poison Creek, Chalk Hills, and Glenns Ferry formations were deposited concurrently with basin extension and normal faulting. Lacustrine and fluvial deposition interspersed with subordinate amounts of rhyolitic and basaltic flows and sills created a unique reservoir system to a depth of 6500’ in the subsurface. Preliminary analysis of petrophysical well logs resulted in the identification of three main reservoir target intervals that have average net to gross values of 40-80% (with a gross interval thickness between 150-450’). Average porosity of the target intervals are between ~ 10-30%. Analysis of well cuttings reveals potential provenance of clastics for the basin and highlights the interplay between active volcanic emplacement and sedimentation with syndepositional faulting. Depth-structure and isochore maps were generated using Petrel® E&P software platform and illustrate subsurface orientation and thicknesses variations throughout the basin.