The Power of a Global Eustatic Model

Sequence stratigraphy is an invaluable tool for exploration geoscientists. Not only does it facilitate the correlation of time equivalent units, it can also be used as predictive tool. As the industry progressively moves into more frontier and data poor regions, our ability to predict the presence of a working petroleum system becomes ever more important as we continue on our quest to replenish dwindling reserves. The challenge is to continue to develop and refine the application of sequence stratigraphy so we can gain additional exploration insights from a eustatic model.

 

LIFE2017 LONDON: EARTH MODEL FORUM

On Thursday 11th May Landmark Exploration Insights will be hosting the 8th London Earth Model Forum at The Geological Society, during which Dr. Frans van Buchem (Principal Geoscience Advisor), will present on the “The stratigraphic genome: exploration insights from a eustatic model

Abstract: In order to further improve the predictive power of the Neftex Global Sequence Stratigraphic Model, the genetic relationship between eustatic sea level fluctuations and stratigraphic patterns is investigated in more detail. By adding notions of amplitude, frequency and rate of sea-level change, a more subtle relationship emerges than the simple ice-house/green-house concept. This presentation highlights the importance of Cretaceous rapid, high amplitude, high frequency sea level changes, demonstrating how these affected sedimentation patterns and petroleum systems architecture in a predictable way.

The first example is from the Aptian, when very distinct sedimentation patterns developed, dominantly controlled by high amplitude fluctuations in sea level and modified by local climatic and tectonic conditions. The early Aptian transgression resulted in the deposition of worldwide source rocks (OAE1a) including in shallow, carbonate-dominated intra-shelf basins. During the following, long-lasting late Aptian lowstand, low latitude carbonate platforms were exposed, karstified and incised. In higher latitudes siliciclastic lowstands were deposited. In the opening South Atlantic thick evaporates developed at this time, forming the seal of the subsalt play.

The second example is from the Early Cretaceous, which is characterised by large-scale prograding successions punctuated by high amplitude sea level fluctuations, such as the early Valanginian eustatic sea level drop and rise (>100 m). This caused worldwide valley incision and shedding of sands along the basin margins. Carbonate systems of this age show evidence of karstified tops, a faunal crisis and biota turnover, which affected reservoir qualities.

These periods, when major global events acted together to produce the key components of the petroleum system, seem to be largely related to the nature of the sea level curve. The identification of these themes is fundamental for exploration in time-equivalent basins or in other time intervals with comparable conditions. In the future, local variations on these exploration themes will be tested with stratigraphic forward modelling techniques addressing parameter sensitivity and multiple scenario analysis to help reduce risk.

Diagram is an example of an incised valley system in a Mid Cretaceous carbonate platform (van Buchem et al., 2014;  AAPG Mem. 106).

 

JOIN US

This one of a series of technical presentations which will be delivered by Landmark Exploration Insights on Thursday 11th May at our LIFE London event: The Earth Model Forum at The Geological Society, London. The full details of the event and agenda can be found here. Join us as we address some of the key geological challenges facing exploration and unveil the latest developments at the heart of our offering.  

REGISTER NOW

This event is free of charge, but spaces are limited. Reserve your place today by contacting us at LIFE.EMF@Halliburton.com