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 Biostratigraphic
services include micropaleontology (foraminifera), calcareous
nanoplankton, palynology, palynofacies, wellsite biostratigraphy,
stratigraphic reviews, correlation studies and multi-disciplinary
integrated studies. Core Laboratories is increasingly involved in
high-resolution biostratigraphy and palynofacies/biofacies studies
fully integrated with seismic, wireline log and sedimentological or
lithofacies data. The resulting sequence stratigraphic
interpretation gives a much fuller geological understanding of the
sedimentary section than that provided by biostratigraphy
alone.
Foraminferal
and Calcareous Nannoplankton Analyses
It
is important to date a micropalaeontological assemblage in terms of
standard biozones and necessary to recognise stratigraphically
significant rock units based on their micropalaeontological
assemblage for interwell correlation. Micropalaeontological and
palynological assemblages can also be used to assess the
depositional environment since different microfauna are found
associated with different water depths. This data is valuable for
geological and reservoir modeling since the depositional environment
dictates the likely sand geometry, continuity and reservoir
quality. Similarly in carbonate environments the recognition of fore reef, back reef, or lagoonal facies is
important for predicting the most likely location for the
reef.
Semi-quantitative analysis refers to visually
estimated abundances and is recommended for basic interpretation of
age and depositional environment. Quantitative analysis provides
absolute counts and is particularly useful for detailed, high
resolution biostratigraphic studies in a sequence stratigraphic
framework.
Palynofacies Analysis
Detailed palynofacies determination can be of
great value for correlation and assist in defining sequence
stratigraphic events by putting the relatively few taxonomically
based palynological marker events in the correct stratigraphic
context.Palynofacies
analysis allows the identification of distinct palynosequences
bounded by "key" stratal surfaces of regional and/or local sequence
stratigraphic significance. Correlatable stratal surfaces often
prove to be coincident with (and enable more accurate picking of)
seismic events in well sections. Stratal surfaces recognised from
palynofacies associations have been proven to form an invaluable
framework within which each palynology event can be seen in its
geological context.All
this can be achieved independently of, for example, lithofacies,
electrofacies and sedimentology. If, however, palynofacies is
integrated with other disciplines its effectiveness can be
considerably enhanced.
Wellsite Biostratigraphy
Both
micropaleontological and palynological analyses can be performed at
the wellsite in self-contained units both on and offshore. The data
gathered can be invaluable for quick evaluation of age and
environment of the formations drilled. Wellsite data may also be
useful for biosteering in horizontal wells where vertical variations
in palynomorph character allows real-time adjustment to bit
trajectory to keep the well on target.
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