Webinar Q&A – Michael Simmons Answers Your Questions
Are there any major updates for the Paleozoic MFS?
For subscribers to the Neftex product suite, these revisions are already in place. For example extra sequences in the Silurian. Hopefully some of these will be published in due course. I know that Mike Stephenson is taking a new look at the Permian.
How important is Biostratigraphy in sequence stratigraphy?
Very important. It provides the basis for correlation, age calibration and palaeoenvironmental interpretation. Thus MFS and SB recognition. However, much work is still needed to establish the biostratigraphic value of many fossils (e.g. larger benthic foraminifera).
Would you still consider high gamma peaks as the MFS if they are within the carbonates? Is it important to check picks with litho-logs?
MFS can be in clean carbonates with low gamma values. Consider a depositional profile where the carbonates are outboard of the clay-rich lagoon. See papers by Maurer et al. and Droste in GeoArabia Special Publication 4 and Davies et al. 2002 in GeoArabia. But, yes always check the reason for log response carefully.
What are surface types that we can use as sequence boundaries?
Those with time gaps, abrupt facies changes, but can occur in sand on sand relationships. Need to look multiple, not single sections.
Was regional Reservoir Simulation attempted on this model to find out more about the hydrocarbon kitchen and migration pathway from source to reservoir rocks?
In our proprietary work we use the depositional environment maps generated for each MFS and MRS and use these in a depth model to study reservoir effectiveness, source rock maturity, etc.
To what extent can the paleo topography maps driven from 3D structural restoration help build stratigraphic models in Arabian Plate? Which is needed to figure out first the paleogeography or sequence strat.?
The sequence strat provides the time framework to integrate data on depositional environment. This can be integrated with tectonic information to generate paleo-digital elevation models and iteratively inform the palaeogeographies.
Are all stratigraphic cycles the same in number and nature for all the same systems/periods in the world?
Great question. If eustasy was the only control the answer would be yes. But every succession has its local factors. Having said that, many sequences on the Arabian Plate are at least partly eustatic in origin. See a chapter in the new 2020 geological timescale book for a discussion of this.
Can we consider erosional surface as sequence boundary?
Depends on context. Erosional surfaces can be generated by both autocyclic and allocyclic processes.
Is the MFS-based sequence stratigraphy applicable for the glacial sequences e.g. Late Ordovician and Late Paleozoic Ice Age?
Yes, very much so. There are abundant papers on the Late Palaeozoic that demonstrate this. Isostatic effects can cause some diachroneity however, so care should be taken.
What kind of fossils we can use to define MFS surfaces?
The most useful are typically abundances and diversity of planktonic organisms, but in purely platform carbonates other benthic fossils will have value.
What is the limitation of creating a sequence stratigraphic framework using only MSF? E.g. the Lower Cretaceous of the UAE has no shale content in most main reservoirs, and has been deposited on shallow-water platforms with no clastic input.
There is a lot of cyclicity in the Lower Cretaceous of the UAE expressed as marl – carbonate cycles – where the marls are the expression of the land derived clays that are more pure in more proximal settings. See Davies et al. (2002) or Yose et al. (2006) (AAPG Memoir).
If Nahr Umr is rich in Orbitolina fossils, is it therefore considered deeper facies as compared to Natih?
Actually both the Nahr Umr and Natih are rich in Orbitolina and neither indicate particular deep water. Remember that water depth is not the only factor controlling MFS position – consider a depositional transect and which facies are proximal and which are distal. See papers by Maurer et al. and Droste in GeoArabia Special Publication 4 and Davies et al. 2002 in GeoArabia.
What about MFS and surfaces in Kurdistan region, Iraq?
The Arabian Plate model is applicable to Kurdistan. For examples, see the paper on the Triassic by Davies and Simmons (2018) in an EAGE Special Publication.
Can change in the climate now effect the stratigraphical sequence in near future?
For sure! We are now in a time of transgression – the geological record of the past can help us understand the future state of the Earth.
What is the future and relevance of outcrop analogue studies?
These are essential. Only outcrops can really help us really capture all the stratigraphic details. I refer you to the excellent publications of Al-Mojel on the Jurassic of Saudi Arabia.
Why are there limited Cretaceous and Cenozoic stratigraphic traps reported in the Arabian Plate?
Two factors – have they really been looked for? And is seal effectiveness an issue? We need to develop concepts (e.g. lowstands) and then gather the relevant data to prove them up.
Can we differentiate terresial shale and marine shale from wire-line logs with no biostratigraphy information?
Are you aware of any good geochronology work done on Permian strata from sandstones anywhere in the world?
Some nice work has recently been published by Stephenson and Korngreen on the Permian of the Dead Sea region.
Was the Aptian characterized by sea level fall? Wasn’t this age associated with Tethyan extension?
There is a lot of information on the initial Aptian sea-level rise and a glacio-eustatic late Aptian sea-level fall. See GeoArabia Special Publication 4.
Are we close to discovering another giant oil and gas field in the region? Is there any hope in the stratigraphy traps?
Yes. If we develop stratigraphic trap concepts, such as lowstand plays, and then deliberately gather data to test these, they will be found. Large new discoveries continue to be made – the Middle East still has much to give.
Do you think you can actually identify MFS in shelfal carbonates?
Yes, from proximal vs distal facies, and parasequence stacking patterns. But it may not be easy…