What’s this?

What’s this?

Occasional interesting posts by Dr Mark


n is a hydrocarbon zone log analysis parameter

The function of n is to translate a rise in (logged Rt / log predicted Ro) above 1.00 into the corresponding reduction in reservoir Sw below 1.00

Sw^-n  = Rt / Ro


Different scales of measurement between SCAL n and logged Rt invalidate SCAL n in heterogeneous reservoir.


n is an internal log analysis parameter. If SCAL n fails to create actual reservoir Sw from logged Rt/Ro, then the n we are using is wrong, period. It doesn’t matter what lab n is.


What do we use?


Ask yourself: “Where in the reservoir is the answer to the question I am asking?” So, where are we reasonably certain of Sw?  Perhaps we have rotary sidewall cored zones with known por, k and height from which we can calculate a J value and estimate Sw?  Then, use whatever n value makes your logged Rt/Ro deliver that reservoir Sw.  It may be an n value you have never seen in the lab, so what? If you don’t use it your log analysis is wrong.


Think don’t follow. Our task is to evaluate the real reservoir with the tools we are given.


Hint: is each input of the saturation equation a measurement taken from exactly the same piece of of reservoir rock? No, it never is in log analysis.  Hence log analysis works well when the rock is homogenous because it doesn’t matter at what scale or location you measure it.

Enjoy Petrophysics!

#petrophysics #logging #core #saturation #reservoirengineering #reservoirengineer #spwla




m is a water saturated internal log analysis parameter

The function of m is to create a predicted Ro which equals logged Rt if reservoir Sw=1

Different scales of measurement between SCAL m and logged Rt invalidate SCAL m in heterogeneous rock.

m is an INTERNAL log analysis parameter. If SCAL m fails to create LOGGED Sw=1 in Sw100zones of the same rock type, m is wrong, period.


So if Sw goes hard left onto 1.00 in water zones what does that tell you?

Hint: always plot Sw 1.25 – 0 until final results

Enjoy Petrophysics!

So what about n ?

#petrophysics #logging #core #saturation #reservoirengineering #reservoirengineer #spwla



Selected Reactions

Ibrahim Al-Quseimi 1st degree connection1stSenior Petrophysicist at Shell   4h

“m is an INTERNAL log analysis parameter. If SCAL m fails to create LOGGED Sw=1 in Sw100zones of the same rock type, m is wrong, period.” ==> given you have assumed Rt is absolutely correct and not impacted by any possible scenarios.

Mark Deakin  Author

Petrophysics Course Instructor & Consultant    49m

I have assumed that Rt logged is the measurement that will be used in the evaluation. It is not relevant whether it is “correct” or not, we have to use it. The point is that Rt logged will be used in the evaluation, like it or not, therefore IF you want to evaluate the reservoir you must use the m value which delivers the LOGGED Rt value when Sw=1 in the same rock type

It best to think in terms of the measurements actually being made. Hence I stress m is an INTERNAL log analysis parameter, it is not an evaluation output like Por, HPV or Kabs, it’s just something that makes the logs work right. That’s the critical requirement

Petrophysics is not as pure science like physics or math. It is empirical – look and see..

Logging tools do not measure any of the outputs we need por, hpv, kabs they measure something else and we combine them (in transforms) to approximate what we need… at a scale often dissimilar to the scale at which the individual measurements were made, which is why heterogeneity causes problems

Thanks and enjoy




Renewable Energy: The beginning of the end of the honeymoon period

Whilst a long term fan of the inevitability of renewables it is perhaps worth noting why we humans have been so in love with oil for the last 100 years: Energy Density.

This slide from REP shows just how deliciously energy dense oil is – something we have gravitated towards throughout history but are now recoiling from. Much maligned diesel, like most fossil fuels, is approx. x22 as dense by volume as a modern Li ion battery and x74 by weight.

Oil’s energy density doesn’t compare with nuclear of course, which is perhaps a more realistic alternative, but we have learnt to mine, pump and store energy in oil with an ease that we are far from achieving with the electricity from renewables.  Electricity is far more problematic to store in an energy dense form than oil; its energy (power) equivalent transmission lines are also hundreds of times more expensive to build, consume hundreds of times the critical minerals and land area and once built proceed to leak 3-7% of their energy per 1000km, even in ultra high 1,000,000 volt transmission lines (UHVDC, UHVAC). These are factors humanity will increasingly come to realise as the true cost of renewable energy. We can of course synthesise energy carriers locally at source as oil, ammonia or hydrogen, whose density becomes comparable with oil, but synthesis wastes energy itself and requires additional new infra structure – more mining and more transportation.

The honeymoon period of renewable energy is ending and although, as proclaimed above, I am big fan of the inevitability of renewable energy, I urge us all to be honest, transparent and practical and to ridicule political correctness regarding the challenges we face in replacing oil as our primary energy source.

REP     Renewable – Energy Primer


#energy #renewable_energy #energy_density #oil #gas #power #transmission #pipeline #petrophysics




Here’s grid level energy storage, just switch it on!

The uptake of cheap, clean RE is stymied by the lack of grid level storage. A solution for smoothing RE’s supply intermittency already exists, it just needs switching on. No impossible technical breakthroughs required.

The storage capacity of Australia’s distributed 23,000 EV is about 1,725,000 kWh. The storage capacity of the world’s largest centralised lithium ion grid storage, Hornsdale SA, is 194,000 kWh, 11% of Australia’s EVs and cost 172m AUD to install plus running costs, or 97 AUD per South Australia head. So, Australia EVs have about 9 times the storage capacity of the worlds largest lithium ion grid storage, its just not connected.

What we need:

– real time pricing of grid electricity embedded in the 50Hz outlet signal (or in a carrier wave. Grid frequency drops as load exceeds source due to increased turbine rotor torque)
– EV inverters which export user defined discharge to the grid as a function of grid price. Charge back when the grid is cheap
– media pressure and deregulation to clear the forces which are blocking this fix

Advantages: a better more effective use of existing resources; Democratisation of energy/energy autonomy (there’s the rub); Increasing EVs increasing grid stability; Energy security;  Flexible; Cheap; Getting cheaper; Lower taxes; Self regulating; No running costs; Neat and something for a country or a state to be proud of !

Ignorant media, institutions and politicians who don’t want to understand critical science and fail to serve their public.


#renewableenergy  #energystorage  #smartgrid  #evcharging