offers advise (at no cost) and a range of services on the most
appropriate service for a specific exploration problem. However,
the service I use most is THR (Thermal History Reconstruction)
which represents the integration of AFTA, VR and basin modelling
to give a constrained thermal or burial history for a
sampled section. I use THR because without it I am forever running
a vast suite of basin models, based on a series of assumptions
(e.g., stretching factors, tectonic environment, porosity as
a function of time and depth) which I am nervously aware are
very poorly constrained. These endless models can give hugely
varying predictions on hydrocarbon prospectivity. With THR,
I can corner, by direct measurement, some of the most
important factors which influence the generation and migration
of hydrocarbons. Principally, these critical parameters are
the TIME of maximum temperature and the MAGNITUDE of maximum
temperature experienced by the section.
Face it, if my team can reduce the number
of viable basin models by first measuring some of these important
factors, then not only do our models have greater application
and use, but also, we will be spending less time developing
(tweaking) alternative models which are inappropriate. Reduce
the number of options, reduce personnel time and reduce risk
- THR is now used routinely in our company at the front end
of an exploration program.
Also, (although I didn't appreciate this
at the outset), I realised after about 5-6 THR jobs that we
had been dedicating considerable time and resources to modelling
parameters that were not directly influencing the bottom line
- i.e., the time and magnitude of generation and expulsion.
For example, I can remember one guy spending weeks looking at
the possible heatflow history for this particular well location
in South America. He reconstructed the tectonic setting and
determined periods of rifting, drifting, foreland setting, etc.
On this basis and following an extensive literature survey,
he assigned heatflow values through time corresponding to each
of these tectonic settings. Another few weeks were dedicated
to resolving the thermal conductivity of the section (so he
could get to temperature versus time) which meant another literature
survey on porosity variations through time for specific lithologies.
You can well imagine, at this point, we had some very detailed
models and beautifully coloured output (really impressed management!),
but no real handle on which of a dozen models was most appropriate.
Sometime later we ran THR on this well (about 5 AFTA samples
and 12VR samples). What we found was that for this Mesozoic
and Cenozoic section, cooling from maximum paleotemperature
commenced at ~5 Ma and that ~2500 metres of section had been
removed in relation to this event at this well site. Knowing
this, we were then able to model with considerably more confidence
the generation and migration history at this location and the
region. About 10 of our 12 models immediately became obsolete.
Also, regrettably, we realised how much time we had wasted in
trying to understand the Mesozoic and Early Tertiary heatflow
history (and related investigations into sediment conductivities
and porosity). Although arguably interesting, it just didn't
matter to the hydrocarbon story, because all the action was
in the last 5 Ma. I don't think management was ever aware, but
on that particular project, we could have saved probably 4 months
of team time, if we had used THR at the start of the project.
So finally, I like to refer
to this THR approach as CONSTRAINED basin modelling. Everybody
does basin modelling these days (off-the-shelf software has
made this activity very common, and commonly abused ...), but
not necessarily CONSTRAINED basin modelling where the factors
most critical to the bottom line are measured first."