Integration of 3-D Seismic with Geological Knowledge can Detect Non-Amplitude Combination Traps and Discover New Pay Zones in a 600 BCF Mature Play, Northern Lafourche Parish, Louisiana

Steven H. Brachman
Pogo Producing Company, Houston, TX

Fifteen Middle and Lower Miocene reservoir sands have produced over 600 BCFE from seven fields in the Thibodaux project area, northern Lafourche Parish, Louisiana .Traditional interpretation associated productive wells with classic Gulf Coast structural traps. Based on subsurface mapping, Pogo Producing Company staff believed that opportunities existed for stratigraphic and combination traps in the Robulus L-age (Lower Miocene) sands, and especially, their uppermost member, the Nicholls Sand. Our team determined that an unconformity played a major role in determining the location of Nicholls production in the Thibodaux project area. Further mapping revealed other areas where potential for similar traps existed. Subsequent drilling by Pogo and its partners resulted in the largest Nicholls sand discovery to date.

The inability of 3-D seismic to help us identify the presence of either reservoir rock or hydrocarbon accumulations on the Thibodaux 3-D forced us to rely on our subsurface knowledge to help decipher geologic relationships in the upper Rob L sequence. We answered the question of discontinuous Nicholls Sand distribution by identifying the correlation on seismic between a single strong amplitude event and Nicholls Lime, the subsurface relationship between Nicholls Lime and Nicholls Sand, and the impact of the Middle/Lower Miocene unconformity. We concluded that careful subsurface mapping with available well control afforded us a major advantage to discovering new opportunities in the Thibodaux project area, than if we had tried to understand the geologic picture from 3-D seismic alone.