|Abstract or Summary
- Sedimentation rate could become a new exploration tool for evaluating
the source rock potential of sedimentary basins in frontier regions.
Petroleum source rocks are defined on the basis of total organic carbon
by weight percent. An analysis of Deep Sea Drilling Project (DSDP)
cores indicates that there exists quantitative relationships between
sedimentation rate and total organic carbon content in fine grained
ancient marine sediments of Jurassic, Cretaceous and Cenezoic age.
These relationships are independent of geographic setting, geologic age,
and differential compaction, but are highly dependent upon lithology.
For any given sedimentation rate, the total organic carbon content
increases from calcareous to siliceous to black shale sediments. For
each of these lithologies, the total organic carbon content increases
with sedimentation rate due to reduced aerobic microbial degradation at
higher burial rates. Above a critical sedimentation rate, the total
organic carbon content may decrease with increasing sedimentation rate
due to a clastic dilution effect. Aerobic microbial degradation, however,
continues to be less efficient at higher burial rates. Therefore,
even though the total organic carbon content may decrease, the quality of the organic matter preserved and the oil generation and oil migration
potential of the sediment may continue to increase with increasing
Similar relationships have also been established between total
organic carbon and grain accumulation rate, and total organic carbon
accumulation rate and grain accumulation rate. These relationships
support both reduced aerobic microbial degradation and the clastic
dilution effect. In the latter case, the lithologic control is less
pronounced, and the relationship can be used to determine total organic
carbon content even when the lithology is not known.
The results of this study have important implications for petroleum
exploration in frontier regions. Sedimentation rate and grain accumulation
rate could be determined from seismic isopach and velocity data.
When the lithology is not known, such as prior to exploration drilling,
grain accumulation rates could be used to estimate the total organic
carbon content, and the oil generation and oil migration potential of a
sedimentary basin. Once the lithology is known, the source rock potential
of the basin can be more accurately predicted. Future work should
be directed toward testing the application of sedimentation rate and
grain accumulation rate in the petroleum exploration of frontier regions.