GEOCLASTICA Ltd

Dr ROGER HIGGS
rogerhiggs@geoclastica.com
cc to rogerhiggs@hotmail.com

Consulting in:
Sedimentology, Sequence Stratigraphy &
Climate- & Sea-Level Change



Consultation by the hour, day or week on

CLIMATE & SEA-LEVEL CHANGE

providing:

-education & advice for
governments, businesses & individuals

-predictions of climate & sea level
over the next 100 years

Go directly to ‘Climate & Sea-Level Advice’ page


and



SEDIMENTOLOGY & SEQUENCE STRATIGRAPHY

to:

-assess economic viability of oil/gas fields & basins

-reduce exploration & development dry-hole risk


Vital economic importance

In petroleum exploration and development, incorrect interpretation of sequence stratigraphy (prediction of reservoir distribution) and depositional environment (reservoir geometry) risks huge economic losses in (A) misplaced wells, (B) missed oil and gas, and (C) phantom resources.

Techniques

  • Facies- and sequence analysis of cores, outcrops, image logs
    & correlation panels

  • Thin-section analysis of sandstone composition & diagenesis

Objectives

  • Interpret environments, sequence stratigraphy & depo-tectonic setting

  • Predict sand distribution at the basin scale

  • Predict undiscovered stratigraphic plays, e.g. incised valleys, lowstand fans

  • Predict sand-body geometry, size & orientation, for better placement of exploration & development wells (especially horizontal ones)

  • Improve basin-history models by using thin-section analysis of sandstone diagenesis to interpret number/timing of uplift events & oil charges

  • Determine sandstone porosity type & evolution, for better subsurface porosity prediction

  • Assess reservoir damage risk (swelling clays, etc.)

  • Thin-section determination of porosity & bitumen volume (immobile oil), for improved reserves calculations

  • Obtain more realistic reservoir parameters for production simulation models (geometry, dimensions, facies, porosity)

Pitfalls

Facies- or sequence analysis is not a straightforward observation or calculation, like petrophysics for example. On the contrary, it is highly interpretive and depends utterly on the sedimentologist's experience -

"The best sedimentologist is he/she who has examined the most rocks and studied the most literature".

For example, turbidites can easily be misinterpreted as deep-sea fan instead of shelfal if the subtle differences between unidirectional- and combined-flow cross lamination are missed in core, with profound implications for the predicted geographic distribution and volume of oil or gas.

Similarly, misinterpretation of in situ seismites as far-travelled debrites or slumps can lead to highly erroneous interpretations of depositional environment and tectonic setting (hence incorrect predictions of sand distribution and sand-body geometry), with potentially drastic financial repercussions.

As a final caution, when sedimentary structures are not clearly exposed, as is often the case in cores, their "identification" is really an interpretation, upon which more interpretations (process/environment) are built, i.e. a hazardous double interpretation.

So, choose your sedimentologist carefully!

GEOCLASTICA LTD
Registered in England No 3540967

Homepage en español CV & Publications
CLIMATE & SEA LEVEL ADVICE Petroleum Sedimentology Course
Turbidite Reservoir Analogs Lecture Outcrop Analog Field Trips
Core & Outcrop Facies Logging Sandstone Porosity Prediction
Blockley Cotswold Geological Walks Bude Cornwall Geological Walks
Non-Exclusive Exploration Reports for Sale:
Trinidad Venezuela