SUCHECKI, ROBERT K., G. S. PAN, and A. TURA, ARCO Exploration and Production Technology, Plano, TX

ABSTRACT: Defining the Gap Between Concept and Seismic Resolution of Lowstand Turbidite Reservoirs

Seismic stratigraphic criteria for lowstand turbidite reservoirs suggested from few calibrated examples are amplitude character and external and internal reflection geometries. Moreover, the physical stratigraphy of these lowstand turbidites is inferred to be sheet-like elements (basin-floor fan) and channel-levee complexes (slope fan).

Synthetic seismic modeling to evaluate the sensitivity of these qualitative and conceptual models illustrates the gap between depositional facies derived from rock observations and seismic data. Two-dimensional synthetic seismic sections of sand- and mud-rich turbidite outcrops up to 10

kilometers in lateral extent were constructed based on 1-D vertical incidence, zero offset ray modeling, and full wave field methods. Forward analysis shows that only under optimal conditions can depositional features other than major channels and channel margins be imaged with confident interpretation. Other outcrop depositional and stratigraphic features thatare thought to make up turbidite reservoirs, such as sand-rich compensation cycles and large crevasse and overbank deposits, are poorly imaged in the scale of this analysis.

Analysis of multifold seismic to determine limits of geometry resolution and lithofacies inference in turbidite systems that contain interpreted basin-floor fan and channel-levee seismic features further illustrates the gap between depositional concepts and accurate prediction methods based on seismic data alone. In many instances, definition of even the external geometry to discriminate between basin-floor fan and slope-fan systems is just as ambiguous as its application in outcrop determinations. Characterization of the commensurate uncertainty in lithofacies inference defines the reservoir uncertainty of stratigraphic plays in lowstand turbidite deposits.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.