The pre-drill interpretation of a suspected submarine fan complex (SFC) included seismic sequence analysis, seismic facies analysis, isopach mapping of lobes, and structural mapping. The seismic sequence analysis interpreted an eroded sand-rich shelf updip from the SFC and placed the SFC in a lowstand sequence. However, downdip well control showed little sand present near the SFC and sand-richness of the system was a concern.
Seismic facies analysis was performed on a mile by mile grid of seismic data for the purpose of identifying facies of higher probable sand content within the SFC. Due to low seismic resolution, only features larger than 400 ft horizontally and 150 ft vertically were identifiable. The SFC was divided into six chronostratigraphic units using onlap relationships and the principle of superposition. Within each chronostratigraphic unit, interpretation of channel and lobe systems were made. The postulated channels identified as updip were interpreted to bifurcate downdip with channel fill interpreted as depositional and more likely sand prone.
The initial well location was chosen to optimize the number of channels to be intersected, while still drilling structurally updip. An isopach thick was also drilled in the event that the lobe facies were sand prone. A second well was drilled into a downdip isopach thickness suspected of containing only lobe facies.
Post-drill evaluations show the SFC to be fine grained and sand poor. However, two zones containing sand were encountered in the first well at the levels where channels were predicted. Given this result the value of these analyses are readily apparent.
AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)