Sequence Stratigraphy

RAT Nomogram for Semi-automated Sequence Stratigraphy

2017-11-27T12:34:00.003+01:00

Seismic sequence stratigraphy contains a set of manually or automated horizons, which need calibration. The calibration is generally done by taking the simple measurements from logs and assigning them to a fixed event on seismic. Such an event is generally labelled as a horizon.

Since each seismic horizon can be treated as a timelines, going back to Peter Vail's assertion, one can establish a linear time scale and assign it to a set of seismic horizons. In addition to this, we also have relative time units such as geochronologic (Jurassic, Cretacous, Tertiary). So, we are dealing with three time scales to be calibrated:

An arbitrary time series established by counting seismic horizons, either manually mapped or automatically extracted.
Geochronologic units
Absolute time scale.

To construct a time scale, that matches all time series, one really need to implement or draw a nomogram as proposed by Qayyum et al. (2017).

It may look like this:

Tripple nature of a timeline

It is common to treat a single timelines (a seismic horizons for instance) as relative. By relative here means that it is unknown upfront, just by looking at the geometrical configuration of strata, how much time an event or a horizon represent. However, using the nomogram, one can extract such an information and may find that an event exhibit tripple nature:

1) An isochronous RGT line on seismic data is an isochronous marker in time stratigraphy with absolute measurements.

2) An isochronous RGT line on seismic data is a diachronous marker in time stratigraphy with absolute measurements.

3) An isochronous RGT line on seismic data is an unconformable marker in time stratigraphy with absolute measurements.

Here the term isochronous means that a timeline carrries a unique relative time index/number.

An example nomogram illustrating the tripple nature of a timeline is presented below.

References:

Qayyum, F., Betzler, C., and Catuneanu, O., 2017, The Wheeler diagram, flattening theory, and time,

July 2017,

Marine and Petroleum Geology 86,

DOI

10.1016/j.marpetgeo.2017.07.034

Qayyum, F., Betzler, C., and Catuneanu, O., 2018, Space-time continuum in seismic stratigraphy: Principles and norms, Interpretation, Vol. 6, No. 1 (February 2018); p. 1–12, 5 FIGS., 1 TABLE.

Spatial Limitation of Sequence Stratigraphic Units

2017-11-27T12:12:00.000+01:00

A short note for beginners/students

One of fundamental problems in our stratigraphic understanding is that we consider a stratigraphic unit as layers that may continue over a part of basin and may also correlate within and across the basin. This leads us to a troublesome procedure of correlation to build a sequence stratigraphic framework.

This post is a brief review on the correlation concept within a sequence stratigraphic perspective. I would like to cover briefly one point here that a sequence stratigraphic unit is spatially a limited unit.

A stratigraphic unit is always formed within a specific space (or accommodation space; do not want to complicate with terms). Within such a space, it may be altered or modified by post-depositional sedimentary and structural processes. Despite the fact of its origin; the unit would remain within the same space and may be reduced in volume (if eroded). Such a space would always be geographically restricted suggesting that a unit would be spatially limited.

If a unit is spatially limited, how does it define?

Mostly a stratigraphic unit is defined by its physical properties and time. The physical properties can be measured on surface and also in the sub-surface. Such measurements can thereafter lead us to define a stratigraphic unit. A sequence stratigraphic unit on the other hand relies much on the subjective time correlation. The time is primarily the relative geologic time (RGT). This puts another uncertainty - a sequence stratigraphic unit is time-limited.

Therefore, I would not be too wrong to say that a sequence stratigraphic unit is spatio-temporarily limited.

With such uncertainty, it would be wise if you correlate strata within a basin based on subjective time lines (or time base sequence stratigraphic surfaces) with or without physical properties. The time can be a regional boundary (e.g. Top Cretaceous, Top Jurassic and so forth) if it is correlated from basin center to the basin edge.

References:

Qayyum, F., C. Octavian, and P. F. M. De Groot, 2015, Historical developments in wheeler diagrams and future directions: Basin Research, 27, 336–350, doi: 10.1111/bre.12077.

Stratigraphic Base Level Revisited in Deep-water Settings

2017-09-08T09:58:00.002+02:00

It has been 100 years since Barrell (1917) solidified the base level concept, which is widely used in sequence stratigraphy. The concept was first introduced by Powel (1875). It is still broadly used in non-marine, near shore and deep-water settings. The problem arrives when the base level concept is applied in deep-water settings. Most of us will consider the sea level/wave base as a base level. However, it is simply not! The magnitude at which sea level or wave base varies is much smaller than the changes that we observe on the modern or ancient sea floor. Recalling, below the base level deposition happens and above it erosion is possible. This original definition gets violated when sea level is chosen as a base level proxy. As annotated in the figure below, the sea level or wave base can not be considered as a proxy for the base level since erosion and deposition happen below this level. To solve such a conceptual problem, we always need to place the base level close to the sea floor topography depending on its gradient much similar to the way we define the base level in a non-marine setting. Obviously, the ultimate reference can be the sea level but the instantaneous variations on the Earth’s surface are controlled by a temporary base level. This was the beginning of our synthesis to compile a document that not only describes the concept but also provides an optimum solution to the problem. The preservation/removal of geologic timelines and time units and their reconstruction based on flattening theory is another thing to look at within the context of the base level. It is the base level oscillation that results in creation/destruction of an accommodation space, which allows the erosional and depositional profiles to re-adjust & produce geologic timelines or time-units. To read more, follow this link.

https://authors.elsevier.com/a/1VVEByDcGAl5h

(free copy valid till Sep 15, 2017)

You can also request for a private copy via my ResearchGate page.

Image taken from Qayyum et al., 2017, The Wheeler diagram, flattening theory, and time, Marine and Petroleum Geology, 86, 1417-1430.

Coupled Transgressive - Regressive Systems

2013-02-15T14:30:00.000+01:00

Introduction

Some other day, I thought that I need to post a small blogger note. It should describe the spatial extent of a sequence stratigraphic unit. In my experience, it has been an common misunderstanding in communication and interpretation. If one interprets a systems tract over 100s of kilometers with the same nature (e.g. regression), then other will sub-divide it into several strike oriented systems tracts. Well, I will not go that deep but will simply say, "all sequence stratigraphic units are site-specific just like lithostratigraphic units." Sequence stratigraphy has an advantage because it defines time-based units e.g. base level rise/fall.

The main objective of this post is to show my personal opinions on the present day example taken from Louisiana Holocene continental shelf (N. America).

See the figure below.

Supply vs. Accommodation vs. Shoreline Trajectories:

In the figure above, what do you learn?

Increasing sedimentation of Holocene Mississippi delta compared to the transgression rate. Sediments progrades on to the shelf and build outwards - a regression (HST).
There was an abandoned delta of Pleistocene epoch as it has been annotated in the figure. Nevertheless, that part of the delta has been transgressed and at present it is under strong wave dominated setting. There are several barrier shoals developed parallel to the coast giving hints of wave-dominated settings. Overall, the St. Bernard Shoals and the back shoal margin (Chandeleur region) are transgressive systems (TST).
These systems occur within 20Km of a distance along the coast.
If you try to compare the rate of aggradation in both (red and yellow circles), you will obviously notice that the delta systems aggrades more compared to the wave dominated settings. Note that the later ones are highly destructive systems.

Open Discussion

Along the basin strike, it is quite common to have coupled or coeval systems tracts. When a delta develops outwards, there are some of its components which will either be tide/wave dominated. In principle, most of the delatic systems could have both components at the same time as highlighted in the above system. I wonder if a delta (at present) has all three components (tide, wave, and river) dominating at the coast/shelf. If you know any example, please post here.

I look forward to your comments on my interpretation. I am open and excited to hear back from you either positive or negative.

Cheers,

Farrukh

Maximum Regressive Surface (MRS)

2012-11-28T15:42:00.001+01:00

Maximum Regressive Surface (MRS)

Other Synonyms: Transgressive Surface (TS)

This is a short post about the MRS that is considered as an easy to identify on outcrops and well data because of some reasons. This post would covers the fundamentals of placing a MRS in a stratigraphic unit and how to avoid pitfalls in its interpretation.

Definition

It is a surface that marks the start of shoreline regression towards basin. It suggests a base level fall and subsequent marine regression.

Recognition

In the outcrop and wireline logs it is mostly recognized as a surface separating a coarsening upward succession from the overlying fining upward succession. This suggests that the underlying succession is a regressive unit and the overlying sequence is a transgressive unit.

In the above seismic data, you may notice a distinct MRS separating the underlying regressive unit (RST) from the overlying transgressive unit (TST). This surface forms a healing phase wedge above that is dominated by the transgressive fills. This healing phase is formed soon after the river dominated stages when the delta prograded maximum into the basin. The basinal i.e. deepwater part of the MRS are not within this survey range.

Note that the slope segment of this surface can also be treated as a slope onlap surface (SOS) as defined by Embry (2009).

Same as above but with an emphasis of Embry (2009) concept of SOS.

If a part of this surface is later on being modified by marine transgression, you may also highlight that segment as TS.

Better to colour code this surface as a distinct blue colour.

For the carbonates, similar things should be identified. Note that in carbonates things could be very complex as when maximum regression occur, the platform may be exposed and karstified. In such a case, the MRS may adjoin up-dip with a SU. Other cases could be that during max. regression the platform may contain shallow water environment and the carbonates are happily flourishing. In such a case, MRS would mostly be resolved on wireline logs or cores. Seismic data would mainly show an adjoining surface.

An example from Bover-Arnal et al. (2009) is shown below:

Another point to note that the MRS is a time-based surface (Embry 2009) and it may have associated segments such as SOS, RSME and even SU.

Advantage

The benefit of MRS is that one clearly discriminates between transgressive strata and regressive strata. It marks the boundary or transition from regression to transgression and could be used to predict reservoir (and its quality). In some cases, MRS could also form a seal (e.g. mud rich delta) and in other cases could destroy the sealing potential (e.g. wave-storm dominated settings). In the carbonates it is an indication that the tidal - supratidal facies may seal the previously build-ups reservoirs. In mixed settings, it can trace the regressive delta and its spatial distributions to identify the downslope or basinal reservoirs.

Common Pitfalls

Quite similar context as in the MFS.

References

Catuneanu, O. 2006. Principles of Sequence Stratigraphy, Elsevier.

Embry, A.F., 2009, Practical Sequence Stratigraphy. Canadian Society of Petroleum Geologists, Online at www.cspg.org, 79 p.
See also:http://www.sepmstrata.org/Terminology.aspx?id=maximum%20regressive%20surface

Bover-Arnal, T., Salas, R., Moreno-Bedmar, J.A., Bitzer, K., 2009. Sequence stratigraphy and architecture of a late Early-
Middle Aptian carbonate platform succession from the western Maestrat Basin (Iberian Chain, Spain). Sedimentary Geology,
219, 280-301.

Maximum Flooding Surface

2012-11-25T17:35:00.001+01:00

Maximum Flooding Surface (MFS)

By F. Qayyum

This is a short post about the MFS that is considered as an easy to identify on outcrops and well data because of some reasons. This post would covers the fundamentals of placing a MFS in a stratigraphic unit and how to avoid pitfalls in its interpretation.

Definition

It is a surface that marks the end of shoreline transgression towards land or coastal plain. It suggests a base level rise and subsequent marine transgression onto the shelf or coastal plain.

Recognition

It can be treated as a downlap surface because overlying strata may prograde and downlap on it. This is a typical case for a normal regressive deltaic progradation or simply siliciclastic system reaching the shoreface and basin. The overlying system could either be a HST or LST depending on the location.

On the well logs, it is marked by a deepening up-ward GR trend. This means that one is going to mostly define a massive shale as a MFS marker at a shelf location or in the basin. Back-stepping stratal stacking patterns in the outcrops and also in the seismic data are also useful tools to recognize this surface.

In non-marine intervals, it is difficult to identify the back-stepping patterns. For instance, in the fluvial settings, a rise in base level will flood the floodplains and thereafter a MFS starts developping. Note that in such a case, the stream rejuvination is less than the stream aggradation that could be used as a reference to placing MFS soon before the stream rejuvination starts or base level starts falling. The grain size would serve a reference in such a case.

Advantage

It helps in characterizing as stratigraphic interval as one can use it as a reference surface to identify the source and seal. On seismic data, it can be used to identify stratigraphic traps.

Common Pitfalls

People say that this is an easy to identify surface. But this is not always the case. Not all shale markers are the MFS or FS. It is also difficult to be mapped in the deep-water settings as the strata there do not show back-stepping geometries clearly and also the deep water settings may mostly show a shale prone interval. Same is the case for a floodplain dominated by clay rich setting even if the base level oscillates at every kilo-year.

MFS should be marked or interpreted by integrating various datasets. It should not be placed blindly by looking at the well motifs and calling all shale markers as MFS markers.

MFS could also be scoured and re-worked by storms or a later sedimentary process. In such a case, it could be a separation between two coarsening up-ward trends as indicated by Catuneanu (2002) in his book. A similar case may also occur in a back-stepping beach settings where you may noticed stacked beaches and thereafter the MFS could also be placed at the top of a preserved beach. If no transgressive strata is preserved, you may notice that MFS is adjoining with MRS.

According to Embry (2009) or his previous texts, the MFS is a material-based surface as it defines the rise in base level. For those who do not know about the material-based surface nomenclature, here is a text taken from Embry's paper:

A material-based surface is defined on the basis of observable physical characteristics which include 1) the physical properties of the surface and of overlying and underlying strata and 2) the geometrical relationships between the surface and the underlying and overlying strata.

References

Catuneanu, O. 2006. Principles of Sequence Stratigraphy, Elsevier.

Embry, A.F., 2009, Practical Sequence Stratigraphy. Canadian Society of Petroleum Geologists, Online at www.cspg.org, 79 p.

Tribute to Harry E. Wheeler

2012-11-25T00:13:00.000+01:00

H.E. Wheeler's Innovation

A short note for those who are innovative and do not bother about making patents.
By F. Qayyum

Wheeler spent his time with Sloss and finally got succeeded in presenting a stratigraphic unit within a spatio-temporal framework. When he proposed the idea to the scientific community, he probably did not think that his innovation would be commercialize in such a way that at present days people will earn money. He proposed an idea voluntarily just like other geologists such as Steno, Lyell, William Smith etc. No one would have ever thought that their principles (non patented) would be used everyday. They actually benefited the entire mankind and thanks to them that we are using them to explore for the energy resources.

In any case, we started using those concepts and put patents on top of each others. If you scroll through the historical development of Wheeler diagrams, you would be fully surprised that why are we doing this. We invent something on top of a pre-invented feature and call it as a standalone protected intellectual property. We probably do this because we do not want that others would commercialize our technology / methodology. We are probably right in doing this. It also tells that a human being is hungry at both ends: one wants to protect his idea because the others want to steal it. You cannot just stop it.

Should Innovation Stop?

Innovation should never stop. It is a kind of wind that blossoms the trees and finally us. Wheeler diagrams have always been extended just as the seismic technology is progressing. New ideas are revolutionalizing and people are utilizing these diagrams to understand the subsurface. It does not matter to those who are innovative and like to be creative if their ideas based on a pre-invented idea should be protected or not.

For those, who are not aware of the progress of Wheeler diagrams, here is a brief historical sketch:

1958 - Harry E. Wheeler, fundamental sketch and concept of Time Stratigraphy.

1977 - Exxon Group lead by Peter Vail used Wheeler's idea on the seismic data.
2002 - Keskes from Elf (Total) introduced the seismically driven Wheeler diagram

2003 - Lomask introduced the idea of flattenning without picking in SEG. Stakr also introduced his idea of phased based transformation into age volume that later on got rightly published in 2004.

2004 - Tracy Stark extended the idea to 3D Seismic

2005- 2011, market opens and many algorithms were introduced such as Ligtenberg et al., 2006; Monsen et al., 2007; Lacaze et al., 2011.

2012-onwards Extension to the Wheeler diagrams by Qayyum et al., 2012a, b. Integration of seismic and well data and the introduction of 4th dimension in the existing Wheeler diagrams.

What Next?

I personally think that we should be thinking of innovating and extending the ideas further. We have recently introduced the 4D Wheeler diagrams in the William Smith Meeting 2012. That is the next step for all of us! We should be preparing the chronostratigraphic charts based on such a concept i.e. integrate multi-resolution datasets and add the missing dimension to the diagram that you construct. The only possible approach is the method that we introduced.

I believe that people would like to use that concept to build an appropriate sequence stratigraphic framework. You will read its full text soon. I hope that you will like it.

Tribute to Wheeler

Thank you Harry, if you would not have created such a crazy diagram, we would not have taken it that far. You earned probably reputation but you have no idea what others are earning nowadays. You made the concept clear and people made the applications clearer. Well its a cruel industry. But we can never forget your idea and will continuously extend it. I hope that your message is clear enough to us to give you an everlasting tribute.

This is my first post on this blog! Happy reading and apologies for a bad English.

References

Keskes, N. 2002. GEOTIME TM: A New Tool for Seismic Stratigraphy Analysis. VailFest; Sequence Stratigraphic Symposium, A Tribute to Peter R. Vail.

Lacaze, S., Pauget, F., Lopez, M. & Gay, A. 2011. Seismic Stratigraphic Interpretation from a Geological Model – A North Sea Case Study. 81st International Annual Meeting. San Antonio: Society of Exploration Geophysics (SEG).

Ligtenberg, H., de Bruin, G. & Hemstra, N. 2006. Sequence Stratigraphic Interpretation in the Wheeler Transformed (Flattened) Seismic Domain. 68th EAGE Conference & Exhibition. Vienna.

Lomask, J. 2003. Flattening 3-D seismic cubes without picking. 73rd Annual International Meeting. Dallas, Texas: Society of Exploration Geophysics (SEG).

Monsen, E., Borgos, H. G., Le Guern, P. & Sonneland, L. 2007. Geological Process Controlled Interpretation Based On 3D Wheeler Diagram Generation. SEG Annual Meeting. San Antonio, Texas: Society of Exploration Geophysicists (SEG).

Qayyum, F., de Groot, P., and Hemstra, N., 2012a. Using 3D Wheeler diagrams in Seismic Interpretation - The HorizonCube method. First break, 30, p. 103-109.

Qayyum, F., de Groot, P., and Hemstra, N., 2012a. From 2D to 4D Wheeler diagrams, William Smith Meeting, Strata and Time - Probing the gaps in our understanding, Sep 4-5, London.

Stark, T. J. 2004. Relative geologic time (age) volumes—Relating every seismic sample to a geologically reasonable horizon. The Leading Edge, 23, 928-932.

Wheeler, H.E. 1958, Time Stratigraphy, AAPG Bulletin, 42, p. 1047-1063.

Wheeler, H.E. 1964, Base level, lithosphere surface, and time stratigraphy, Geologic Society of America Bulletin, July 1964, 75(7), p. 599-610.

Welcome!

2011-07-16T12:38:00.001+02:00

Welcome to my blog which is a discussion on sequence stratigraphy.