Petrophysics: More Important Than Ever Graham Davis Chief Petrophysicist President - Aberdeen Formation Evaluation Society (AFES)

Outline Themes The Role of a Petrophysicist Log Analysis (what) Vs Petrophysics (why) Petrophysics in practise Why is it still important or necessary? Changing analysis requirements through time. Remaining Oil in existing fields – can we quantify it? can we get it? AFES Local Chapter of SPWLA (Society of Petrophysicists and Well Log Analysts) Monthly Meetings for professional development and networking. Presentation to Aberdeen University MSc Course

The Role of a Petrophysicist

Log Analysis (what) Vs Petrophysics (why)

Petrophysics in practise

Why is it still important or necessary?

Changing analysis requirements through time.

Remaining Oil in existing fields – can we quantify it? can we get it?

AFES

Local Chapter of SPWLA (Society of Petrophysicists and Well Log Analysts)

Monthly Meetings for professional development and networking.

Petrophysics – The Customers Calgary Mappers Drillers Geophysicists Geologists Model Builders Petrophysicist Engineers Corporate

Well Logging – making measurements in our Wellbores Photo courtesy of Reeves Wireline

Routine Log Acquisition

Routine Log Analysis Oil Leg Average Sw = 44% -10,060 TVDSS “OWC?” Eyeball Sw 30%

Routine Log Analysis – Parameter Sensitivity Eyeball Sw 20% Oil Leg Average Sw = 38% -10,110 TVDSS “OWC?”

Routine Log Analysis – SWH Modelling Now we’re getting a bit more petrophysical! Saturation height functions require an understanding of how much oil a rock is capable of holding at any height (depth) in the reservoir

Routine Log Analysis + Core Some think of Log + Core = Petrophysics (but really core is just another log unless you “learn” from it) Too much Water in the Core? WBM invasion? Too much Water in the log? Shaly sand?

Petrophysical Analysis – Flow Prediction Even a Geologist could pick the Perfs here (but might be surprised at lack of flow from upper interval) Tarbert & Rannoch are the “Tricky” Brent reservoirs!

Petrophysical Analysis – Moveable Oil? If taken this far, this is probably where the petrophysics would have stopped in days gone by RESIDUAL

Petrophysical Analysis – What if drilled today? Hypothetical swept profile – typical of the logs seen today Now things get complicated!

Petrophysical Analysis – Where’s the water now? We know, from the SWH, what the initial oil saturation would have been, so we can infer where water influx (CYAN) has occurred … ..but can we determine whether residual saturation has been reached?

Petrophysical Analysis – Where’s the water now? We know, from the SWH, what the initial oil saturation would have been, so we can infer where water influx (CYAN) has occurred … ..but can we determine whether residual saturation has been reached? By the way – we rarely get new core in old fields (except for special studies)

Petrophysical Analysis – Residual or Moveable? Obviously it’s not simple – there are even more uncertainties and errors in evaluating saturations at this end of the spectrum The salinity of the sweep water mix is uncertain

Petrophysical Analysis – Residual or Moveable? Electrical (Archie) Parameters in the secondary imbibition cycle are often poorly understood Obviously it’s not simple – there are even more uncertainties and errors in evaluating saturations at this end of the spectrum

Log Analysis – Residual or Moveable? If you just did the “Log Analysis” you may not know whether the oil saturation was swept-residual (so not producible) or poorly charged but still producible.

Summary Why is all this important? Need to know how much “Gas is left in the Tank”. Operating, Buying or selling old Assets. Smaller Resources Pools – reservoir quality relatively more critical. It is accepted that Geophysicists still make the biggest errors! High cost environment (oil price!) – Wells have to deliver as planned Marginal Developments – Less “eyeball” Properties please

Why is all this important?

Need to know how much “Gas is left in the Tank”.

Operating, Buying or selling old Assets.

Smaller Resources Pools – reservoir quality relatively more critical.

It is accepted that Geophysicists still make the biggest errors!

High cost environment (oil price!) – Wells have to deliver as planned

Marginal Developments – Less “eyeball” Properties please

Outline Themes - Revisited The Role of a Petrophysicist Log Analysis (what) Vs Petrophysics (why) Petrophysics in practise Why is it still important or necessary? Changing analysis requirements through time. Remaining Oil in existing fields – can we quantify it? can we get it? AFES Local Chapter of SPWLA (Society of Petrophysicists and Well Log Analysts) Monthly Meetings for professional development and networking. Website: www.afes.org.uk

The Role of a Petrophysicist

Log Analysis (what) Vs Petrophysics (why)

Petrophysics in practise

Why is it still important or necessary?

Changing analysis requirements through time.

Remaining Oil in existing fields – can we quantify it? can we get it?

AFES

Local Chapter of SPWLA (Society of Petrophysicists and Well Log Analysts)

Monthly Meetings for professional development and networking.

Website: www.afes.org.uk

Aberdeen Formation Evaluation Society (AFES) www.afes.org.uk

And Finally! MSc Students please note…….….

MSc Students please note…….….

It Seems Like a Lifetime in Petrophysics! When you first hear that your project is in Petrophysics ..you’re young and naturally a bit apprehensive!

It Seems Like a Lifetime in Petrophysics! Then, with experience, older and wiser, you can look back on your time in Petrophysics with happy memories You made a difference!!

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