Abstract: Geometrical Characterization of Geology and Reservoir Features in Submarine Fan and Channel Deposits through Integration of Borehole Imagery, LWD or Well Logs, Core and Geotesting

NURMI, ROY, STEVE HANSEN, and CHRIS PRESMYK, Schlumberger, Houston, TX, and Bakersfield, CA

The geometrical analysis of depositional facies, erosional channels and sedimentary structures as well as tectonic features can be critical in assessing wildcats or development wells. Often there is interaction between syndepositional tectonism and depositional processes in controlling fan and channel geometry and orientation. Borehole imagery, including electrical, new density and a variety of acoustic imagery techniques are providing new insights into reservoir geometry, including otherwise undetected erosional channels and fault blocks with undrained attic oil. Detailed analysis of channel (shape and scour) orientation and fault orientations shows that some submarine channels follow faults striking across basinal slopes. In addition, the numerous microfaults and larger faults revealed provide a key to fault distribution mapping as well as to their origin, geometry and possibly hydraulic characteristics.

Intimate mixtures of sand, silt, and shale or conglomerates generally frustrate the standard evaluation of cuttings, sidewall cores and standard well logs. However, imagery used to define the local structure, fault types and geometry, channel presence and orientation also reveals the presence and geometry of these terrigenous mixtures even at a centimeter scale. Quantification of imagery by nuclear magnetic resonance and/or new-high resolution data from standard nuclear measurements is providing reservoir quantification unequaled by standard well logs, as indicated by highly controlled samples. Very thin-bed alternations below the resolution of most technology are usually present as either channel fills and adjacent levees or distal fan deposits. In other cases it is important to define the deformation of bedding and terrigenous mixtures in large-scale slumps or extensive burrowing.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California